This PDF file contains the front matter associated with SPIE Proceedings Volume 10912, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Nanolasers and nanoLEDs are seen as potential sources for low-power optical interconnects. The enhancement of the spontanous emission rate (Purcell effect) related to the small volume has been perceived as a key aspect in the operation of these devices. The fundamental aspects of size scaling in practical nanolasers and nanoLEDs will be discussed in this talk. Firstly, experimental results on nanoLEDs coupled to waveguides on Si will be presented. The effect of surface recombination will be discussed, together with promising passivation methods. In the second part of the talk, a simple theoretical model based on rate equations will be used to investigate the ultimate limits to scaling. In this model, spontaneous and stimulated emission are treated on the same footing, leading to a consistent treatment of the rate enhancement due to the decreasing volume. The analysis shows that Purcell enhancement of spontaneous emission plays a limited role in practical structures, due to the unavoidable linewidth broadening, while the related volume dependence of the stimulated emission rate has a key impact on nanolaser dynamics.

Metal cavities in some ways behave like non-metal cavities in creating optical modes confined by the cavity mirrors. However metal cavities create an additional physical effect when an emitter is placed in the cavity that is not included in the interaction between the cavity modes and the emitter. Not included in the Hamiltonian for the emitter-mode coupling is the nonradiative decay caused by the metal cavity walls acting on the longitudinal electromagnetic fields of the emitter. To capture the additional interaction includes an additional term in the Hamiltonian not usually captured, for example, by the metal cavity's modal analysis. This talk will address these Hamiltonians and present the analysis based on Green's functions solutions to the different Hamiltonians to address the added interactions. It is shown that a typical Maxwell' solver approach to find "empty" cavity modes is not adequate to predict how the cavity and emitter will work. Instead a complete Green's function solution that includes the longitudinal fields of the Hamiltonian must be used, which includes requiring the emitter's existence in the cavity. This added effect is shown to dramatically change predictions of efficiency and device operation for both lasers and spontaneous emitters that propose to use metal cavities.

The possibility to observe a macroscopically coherent state in a gas of two-dimensional direct excitons at temperatures up to tens of Kelvin is described. The dramatic increase of the exciton lifetime allowing effective thermalization is predicted for the o_-resonant cavities that strongly suppress exciton recombination. The material systems considered are single GaAs quantum wells of different thicknesses and a transition metal dichalcogenide monolayer, embedded in a layered medium with subwavelength period. The quantum hydrodynamic approach combined with the Bogoliubov description yield the one-body density matrix of the system. Employing the Kosterlitz-Thouless “dielectric screening” problem to account for vortices, we obtain the superfluid and the condensate densities and the critical temperature of the Berezinskii-Kosterlitz-Thouless crossover, for all geometries in consideration. Experimentally observable many fold increase of the photoluminescence intensity from the structure as it is cooled below the critical temperature is predicted.

All major performance data of optoelectronic devices usually show a strong temperature dependence due to carrier redistribution from ground to excited states. This is even more severe in smaller bandgap materials such as InP based compounds addressing telecom emission wavelengths of 1.55 µm. As a consequence, not only static properties are deteriorated, also high-speed properties deteriorate at high operation temperatures. In particular, in integrated optoelectronic devices with different functionalities and a high heat load, it is mandatory to use optoelectronic components with much reduced temperature sensitivity compared to conventional semiconductor devices. Atomic-like gain material, such as quantum dot (QD) material, offers strong improvements due to delta-like density of states functions. In the ideal case of a sufficiently large energy splitting between ground and exited states, the carrier distribution stays constant, independent of the operation temperature. This results in constant laser performance, i.e., temperature independent threshold conditions, differential efficiency and modulation properties. However, not only the temperature stability gains from an atomic-like gain profile. Also the emission linewidth in semiconductor lasers can be minimized by avoiding the redistribution of carriers into higher order states. With a symmetric gain function, as obtained in QD materials, the linewidth enhancement factor can be kept well below 1, which suppresses the linewidth broadening effects observed in quantum well gain material. This talk gives an overview of the most recent progress in the development of InP-based QD gain material for directly modulated laser diodes, semiconductor optical amplifiers as well as for ultra-narrow linewidth distributed feedback lasers.

The light-current characteristic (LCC) of quantum dot (QD) lasers is studied in the presence of internal optical absorption loss, which varies with charge carrier density in the waveguide region. Depending on the parameters of the structure, the LCC is shown to be either one- or two-valued. In one-valued LCC, the output optical power increases with increasing injection current, approaches its maximum, rolls over on further increasing current, and finally goes to zero at the maximum operating current. The output power in the first branch of a two-valued LCC behaves similarly to that in a one-valued LCC with the only difference that it is non-zero at the maximum operating current, beyond which the lasing quenches. Besides, at a certain current (second threshold current) exceeding the threshold current for the first branch (first threshold current), the second branch emerges in the LCC. The output power in this branch increases monotonously with increasing current; at the maximum operating current (which is the same as that for the first branch), the two branches merge together. An analytical criterion is derived, which determines whether the LCC will be one- or two-valued. The following parameters enter into this criterion and hence control the shape of the LCC: cross-section of internal loss, maximum modal gain (which, in turn, is controlled by the QD-size dispersion), cross-section of carrier capture into QDs, thickness of the waveguide region, and spontaneous radiative recombination coefficient in that region. The transformation of the LCC shape (from one- to two-valued), which occurs via the variation of the above parameters, is discussed.

As an optical gain medium, colloidal quantum dots (CQDs) are suffering from band-edge state degeneracy which demands multiple-exciton to achieve population inversion. However, fast non-radiative Auger recombination in the multiple-exciton CQDs increases the lasing threshold and limits the gain lifetime. Here, by embedding the quasi type-II CQDs (CdSe/CdS/ZnS core/shell/shell) into the Sawyer−Tower circuit to apply a potential that is experienced as an electric field by the CQDs, we have reached and showed tunable amplified spontaneous emission (ASE) threshold in a long-sought practical device where the CQDs sandwiched between two dielectric layers to retain their high quantum efficiency as in parent solution (quantum yield of > 70%). Singly-charged CQDs help building up population inversion due to pre-existing electrons while strongly enhanced Auger recombination in multiple-charged CQDs stymies the optical amplification. The approach allows us to fine-tune and achieve the optimal charging level to utilize the advantages of singly charged CQDs and avoid the adverse effect of doubly charged CQDs. In addition to experimentally demonstrating threshold tunability, we also developed a kinetic equation model to systematically analyze the electric field dependent ASE threshold. The kinetic model not only confirms our experimental results but also presents to be a reliable tool for accessing the requirements of charging level to achieve nearly zero-threshold trion gain in CQDs. The implications, then, to potential applications of our robust and environment-undependable tuning method are broad, from controlling exciton recombination dynamics to continuous wave (CW) or possibly electrically pumped CQD lasers.

III-Nitrides form a class of wide bandgap semiconductors that have broad applications in optoelectronics technology due to their relatively large band gap, high carrier drift velocity and high breakdown voltage. In particular, GaN and its alloys are promising as component materials in solid-state lighting, radio-frequency, and power electronics. However, these materials generally grow with high defect densities, which can substantially degrade their electronic and optical properties. Therefore, an accurate and detailed knowledge of the influence of defects on their electronic structure will be central to the design of new high-performance materials. Here, we take a density functional theory (DFT) and many-body perturbation theory (MBPT) approach to describe the excited-states of defective GaN. Utilizing MBPT within the GW/BSE approximation, we develop an approach to systematically identify defects, and their associated trap state energies. For a +1 charged nitrogen vacancy within bulk GaN, the predicted bandstructure indicates that this particular defect results in the formation of shallow defect states with trap state energies near the band edges. However, analysis of the electron-hole correlation function reveals that the low-energy excitations are comprised of a mixed bulk-like and defect-like character with significant exciton binding energies (~ 0.1 eV). We discuss the implications of these defect-induced-states for the electron transport and optical properties of GaN.

We investigate the spectral broadening in deep ultraviolet (UV) multi quantum well light emitting diodes (LED) by modeling the emission spectra. Experimental emission spectra of deep UV LEDs exhibit a at tail towards lower energies and a steep decrease towards high energies that cannot be explained by convolution of the spectrum with a broadening function. We devise a luminescence model based on the broadening of the density of states (DOS) function which is consistent with the experimental spectra. The broadening of the DOS also explains the emission red shift with respect to the quantum well subband transitions. In addition, we investigate the in uence of the DOS broadening on the carrier and luminescence in the active region.

The need of high brightness micro-displays in portable applications dedicated to mixed and/or virtual reality has drawn an important research wave on InGaN/GaN based micro-sized light emitting diodes (μLEDs). We propose to use a SPICE modelling technique to describe and simulate the electro-optical behavior of the μLED. A sub-circuit portrayal of the whole device will be used to describe current-voltage behavior and the optical power performance of the device based on the ABC model. We suggest an innovative method to derive instantaneously the carrier concentration from the simulated electrical current in order to determine the μLED quantum efficiency. In a second step, a statistical approach is also added into the SPICE model in order to apprehend the spread on experimental data. This μLED SPICE modelling approach is very important to allow the design of robust pixel driving circuits.

The operation of vertical-cavity surface-emitting lasers (VCSELs) results from the interplay among different physical mechanisms. For this reason, even a basic VCSEL model must address the coupling of electrical injection, stimulated/spontaneous emission and optical resonances, without disregarding the strong thermal effects affecting each of these models, leading to the need of an entangled multiphysical description. With the aim to fill the present gap of advanced comprehensive VCSEL models, in this work we present our VCSEL electro-opto-thermal numerical simulator (VENUS). The paper describes the VENUS constitutive blocks and their coupling strategy. The model is then validated by comparing the most significant lasing features with experimental results.

A relatively simple and stable microwave oscillator tunable across the full X-band is achieved. The microwave oscillations are self-generated limit-cycles produced by a laser diode subjected to optical feedback from a mirror. Further, the oscillations are stabilized utilizing two techniques in tandem, the first being a resonance effect based on locking the two inherent timescales of the laser, and the second being optoelectronic feedback. The resulting stable oscillations are fully tunable across the X-band from 5.5 to 12.1 GHz with typical phase noise performance of -107 dBc/Hz at 10 kHz offset. Further, the system is relatively simple by not requiring multiple lasers, radio-frequency filters, external RF sources, or any specialized equipment, thus, enabling a compact and low-cost microwave oscillator for applications in radar, radio over fiber, and telecommunications.

GaSb-based multiple-quantum-well lasers with In_0.2Ga_0.8Sb wells, Al_0.35Ga_0.65Sb barriers, and Al_0.9Ga_0.1Sb claddings have been fabricated as broad-area Fabry-Perot devices of dimensions 1000 μm × 800 μm. Their current-voltage and light-current characteristics, as well as emission spectra have been measured over a wide temperature range from 280 K down to 20 K. These data have been analyzed for experimental information on carrier freeze out, gain changes related to temperature, temperature-dependence of series resistance, and prospects for high-performance lasers operating at cryogenic temperatures.

We study the coherent multi-mode phenomena in single section Quantum Dot (QD) lasers using a time domain traveling wave approach. In the conventional Fabry-Perot configuration and close to the lasing threshold, we report a continuous wave solution (CW) instability consisting in several longitudinal modes turned on by the strong carrier grating due to the standing wave pattern. In this regime we found intervals of the bias current where the FP-QD laser spontaneously emits Optical Frequency Combs (OFC) as narrow, equally spaced, spectral lines with locked phases. Interestingly, in the unidirectional ring configuration, where carrier grating due to standing wave pattern cannot take place, our simulations show the occurrence (at high pump current) of a new type of self-pulsing phenomenon leading to sub-picosecond pulses with THz repetition rate, multiple of the ring free spectral range. The linear stability analysis of the CW solution of the ring laser is in good agreement with the numerical simulation and it allows to establish an analogy between the observed self-pulsing regime and the well known Risken-Nummedal-Graham-Haken instability consisting in the amplification of the Rabi frequency of the system. Systematic simulations also indicate that, contrary to what happens for self-generation of OFC in FP laser, THz self-pulsing is robust and controllable over a wide range of bias currents, device lengths and degree of inhomogeneous gain broadening. Our results on FP lasers well agree with recent experimental evidences.

In this work, we will review and dramatize legacy topics on tabletop experiments, refined numerics, and continuation methods as well insightful asymptotics for the dynamics of phased arrays of optically coupled quantum well and quantum dot diode lasers. The new set of recent experiments on Topological Diode Lasers provide us with a burning motivation to reexamine these topics and shade light into the ubiquitous instabilities Recoding the linewidth and lineshape of the optical power spectrum of two coupled diode lasers}, optically injected lasers and various feedback configurations we were guided to derive third order Adler type phase equations, as the minimal model of optically coupled diode systems to make predictions and connections with the Kuramoto model. Based on these findings, we have been promoting a differentially pumped two diode laser configuration as a remarkable candidate for the unit cell for the next generation of Topological lasers and Superradiant emitters. The analysis and computation will be presented of the Hopf points and Exceptional Points} for such systems, with their spectral features using rate equations as the staring model. The small signal modulation function of such photonic integrated circuits has been computed and analyzed, finding that even in the twin system we can observe resonances that exist 100GHz speeds. All these findings and observations about the Photonic Meta-Atom will be also reviewed as possible candidate for building blocks of low-noise, highly tunable and ultrafast photonic chip-scale oscillators, with an added simplicity the removal of the expensive optical isolator removed. In addition, two new proposals will be advocated, first, how to observe and dissect Photonic Turbulent Chimeras in large arrays of diode lasers and connect such observations to the elusive Synchronous Sisyphus effect in external cavity lasers, also investigate the chimera presence as a path to the a superradiant emitter and reexamining coexistence of coherent and incoherent modes in the optical comb generated by a passively mode-locked quantum dot laser. We will advocate interpreting such state as a chimera state. Finally, Potential applications of photonic Chimeras in integrated circuits as generators for on-demand optical diverse waveforms will be presented.

Long cavity fibre-based wavelength sweeping lasers are promising devices with a wide range of potential applications ranging from communications to life sciences. For example, Fourier Domain Mode-Locked (FDML) lasers, which are commonly used for Optical Coherence Tomography (OCT) imaging applications are long cavity lasers incorporating an intra-cavity resonator driven in resonance with the cavity round trip time. The coherence properties of such swept sources are of major importance as they define the image quality. The purpose of this work is to analyze the mechanism that deteriorates the coherence of long lasers. In our experiment, the laser included a 100nm wide semiconductor optical amplifier at 1310nm and a fibre cavity that could vary from 20m to 20km. the laser emission wavelength was controlled using a fibre based intra-cavity filter with a bandwidth of 10GHz. Near the lasing threshold and/or for fast carrier decay rate, we observed the appearance of periodic power dropouts with stable Nozaki-Bekki holes (NBH) that circulate in the laser cavity. As a function of the injection current, the laser could operate in various regimes including bi-stability between NBH and stable (cw) operation, unstable NBH or chaotic operation. Such behavior indicates that the interplay between the injection current and carrier decay rate can lead to highly coherent emission of a long cavity laser.

We focused on the effects of group-velocity dispersion (GVD) on the coherent pulse progression in mid-infrared (MIR) quantum-cascade lasers (QCLs). Comparison of GVD effects on the two kinds of typical QCL cavities, i.e., FP and ring cavities, brings insight into the interaction between the GVD and the spatial hole burning (SHB) effect which is only supported by FP cavities but not ring cavities. The theoretical model is built based on the Maxwell-Bloch formulism accounting for two-way propagations of electric field and polarization as well as the couplings among the electric field, the polarization, and the population inversion. The pulse evolution in time-spatial domains is simulated by the finite difference method with prior nondimensionalization, which is necessary for a convergent solution. Results predict that the SHB could broaden the QCL gain bandwidth and induce additional side modes closely around the central lasing mode with an intensity more pronounced than that of GVD associated side modes. Moreover, owing to the SHB, the lasing instability caused by GVD is weaker in a FP cavity than a ring cavity.

We explore experimentally and theoretically the dynamics of a DFB quantum well laser subject to external optical feedback from a mirror. With increasing feedback, the system exhibits the following dynamical scenario: an extremely small limit cycle appears first and is followed by a quasi-periodic regime, and then by three subsequent limit cycles with different repetition rates. This sequence of limit cycles can be associated with the change of phase of the reflected field which reveals translational symmetry and the fact of periodic solutions coexistence which we confirm numerically. The results can be useful for applications in reservoir computing with phase space of coexisting limit cycles acting as a nonlinear reservoir as well as for other applications.

Beamforming, namely exciting properly a set of sources whose collective radiation mimics a given pattern, is an inherently inverse problem. Since the inverse design methods are recently being introduced in photonic systems leading to devices of unprecedented efficiency, we reconsider beamforming in this context. Accordingly, flawless beam-shaping is reported for the simple case of multiple emitters placed along a line. The key parameter to fulfill such an objective is the distance between two consecutive antennas which should obey an approximate inequality, securing both diversity and coherence for the emitting patterns. This condition cannot be attained when infinite directivity is demanded; however, ultra-narrow radiation lobes are developed for the suitable, inversely-determined excitations.

A standard (targeted) distributed Bragg reflector (DBR) has periodic square-wave–like refractive-index profile and its optical performance is determined by the refractive-index ratio of the two applied materials (n12 = n1/n2, n1 > n2) and the number of their periods (N). It is well known that its structural disorder strongly affects its optical properties, but, despite that, this influence has not been quantitatively addressed in the literature. In this work, we propose a precise quantitative definition for a structural disorder of a single DBR unit cell (disorder factor, DF), completing the set of DBR fundamental parameters (n12, N, DF). Then we expose the basis for a novel simulation method, named effective refractive-index approximation (ERIA) [1], showing that, as long as DBR optical properties are concerned, the influence of increasing structural disorder (DF↑) is virtually identical to the influence of decreasing refractive-index ratio (n12↓), with the latter influence being easily quantified. Making use of the ERIA method, simple analytical formulas, which enable rapid insights into the reflectivity and stop-band width of DBRs with different types of transient layers at the heterointerfaces are derived and the results validated, via both transfer-matrix simulations and direct experimental measurements of highly disordered DBRs. The ERIA method is then further applied on resonant microcavities, yielding simple analytical formulas which link their structural disorder (DF) with subsequent deterioration of their quality (Q) factor, and enable comprehensive insight into the link between the two. [1] Ž. Gačević and N. Vukmirović, Phys. Rev. Appl. 9, 064041 (2018).

The majority of commercially available surface plasmon resonance (SPR) sensors rely solely on the detection of the intensity minimum of the reflected signal avoiding the extraction of the polarization properties. Such properties, i.e. the phase difference between polarization components and the azimuthal angle of the polarization ellipse, give sharper responses than the intensity which lead to a better measurement accuracy. Therefore, the lack of extraction of polarization properties in such devices significantly limits their performance. In this work we suggest different configurations of multifunctioning SPR sensing systems that can extract both the normalized reflectivity and the polarization properties simultaneously in the angular and spectral modes. This leads to a significant boost in the performance of existing SPR sensors as multi-parametric functioning systems.

The device-scale simulation of electrically driven solid state quantum light emitters, such as single-photon sources and nanolasers based on semiconductor quantum dots, requires a comprehensive modeling approach, that combines classical device physics with cavity quantum electrodynamics. In a previous work, we have self-consistently coupled the semi-classical drift-diffusion system with a Markovian quantum master equation in Lindblad form to describe (i) the spatially resolved current injection into a quantum dot embedded within a semiconductor device and (ii) the fully quantum mechanical light-matter interaction in the coupled quantum dot-photon system out of one box. In this paper, we extend our hybrid quantum-classical modeling approach by including a Schroedinger–Poisson problem to account for energy shifts of the quantum dot carriers in response to modifications of its macroscopic environment (e.g., quantum confined Stark effect due to the diode’s internal electric field and plasma screening). The approach is demonstrated by simulations of a single-photon emitting diode.

Light-emitting transistor (LET) and transistor laser (TL) can provide the high-speed electrical and optical modulations simultaneously, advancing light-emitting diodes and diode lasers. Still, between experimental data and rate-equation modeling, there are two-order-of-magnitude uncertainties on the carrier lifetimes of quantum wells (QWs) inserted in heavily p-doped bases of these devices. In view of the importance of this timescale on the modulation speed, we provide a comprehensive approach to calculate carrier lifetimes under such circumstances. We model the Hartree potential energy with self-consistent solutions of the Schrodinger’s and Poisson’s equations. The hole distribution is obtained from real-space density of states through multiband retarded Green functions, taking the outgoing-wave features of hole quasi-bound states into account. We then estimate the carrier lifetimes based on a multiband source-radiation approach including both bound-to-bound and bound-to-continuum components of spontaneous (SP) emissions. Under low surface carrier injections, a large Hartree potential is formed, and the valence band around the QW is strongly tilted. Both bound and quasi-bound valence states are present, and quasi-bound holes may tunnel out of QW and reemerge in the base. The SP spectrum from the QW in the heavily doped base is significantly larger than that from an undoped one due to preexisting holes. At the high injection level, the screening effect significantly reduces the Hartree potential and band bending. We also include the nonradiative Auger recombination to evaluate the total carrier lifetime. Overall carrier lifetimes and small-signal ones are estimated as hundred picoseconds at a doping density of 10¹⁹ cm⁻³ and might be even shorter in the case of heavier doping.

Phosphorus-free multiple-quantum-well lasers with In_0.53Ga_0.47As wells, In_0.53Al_0.2Ga_0.27As barriers, and In_0.53Al_0.47As claddings have been fabricated as Fabry-Perot devices of different lengths and widths. Their current-voltage and light-current characteristics have been measured over a wide temperature range from 200 K down to 20 K. These data have been analyzed for experimental information on carrier freeze out, gain changes related to temperature, temperature-dependence of series resistance, and prospects for high-performance lasers operating at cryogenic temperatures.

PureB single-photon avalanche diodes (SPADs) were investigated with the aid of a newly developed TCAD-based numerical modeling method with which characteristics related to the avalanching behavior can be simulated. The p⁺ region forming the anode of the PureB p⁺n photodiode is extremely shallow, only a few nanometer deep, which is essential for obtaining a high photon detection efficiency (PDE) for near-, vacuum- and extreme-ultraviolet (NUV/VUV/EUV) light detection but when an implicit guard ring (GR) is implemented, the dark count rate (DCR) can, despite the GR, be deteriorated at the very sharp corners of the p⁺-region where there is a high concentration of the electric-field. By comparing measurements to simulations, the main mechanism dominating the DCR in the PureB SPADs was identified as band-to-band tunneling (BTBT) while trap-assisted-tunneling also plays a role when the perimeter breakdown is low. Increasing the dose of carriers in the enhancement region negatively impacts the total DCR of the device, but also shifts the origin of the dominant DCR contribution from perimeter to the active region. The simulations for optimization of the SPAD geometry predict that a modification of the n-doped epitaxial region of the PureB SPADs could decrease the DCR by almost two orders of magnitude. This is achieved by increasing the n-epi-layer thickness from 1 μm to 3 μm and lowering the doping from 10¹⁵ cm^-3 to 10¹⁴ cm^-3. A high electric field at the vertical pn junction in the active region can also be minimized by modifying the implantation parameters of the n-enhancement region thus keeping the BTBT contribution to the DCR sufficiently low.

Mosaic filter-on-chip CMOS sensors enable the parallel acquisition of spatial and spectral information. These mosaic sensors are characterized by spectral filters which are applied directly on the sensor pixel in a matrix which is multiplied in the x- and y-direction over the entire sensor surface. Current mosaic sensors for the visible wavelength area using 9 or 16 different spectral filters in 3 × 3 or 4 × 4 matrices. Methods for the reconstruction of spectral reflectance from multispectral resolving sensors have been developed. It is known that the spectral reflectance of natural objects can be approximated with a limited number of spectral base functions. Therefore, continuous spectral distributions can be reconstructed from multispectral data of a limited number of channels. This paper shows how continuous spectral distributions can be reconstructed using spectral reconstruction methods like Moore-Penrose pseudo-inverse, Wiener estimation, Polynomial reconstruction and Reverse principal component analysis. These methods will be evaluated with monolithic mosaic sensors. The Goodness of Fit Coefficient and the CIE color difference are used to evaluate the reconstruction results. The reconstruction methods and the spectral base functions applied for the mosaic sensors are juxtaposed and practical conclusions are drawn for their application.

Links at 1 micron offer key advantages over longer wavelength links. Both ultra-stable, low noise Nd:YAG lasers and high power efficiency, temperature-stable GaAs lasers operate at wavelengths around 1 micron. These components are particularly beneficial for quantum optical systems and links which require stability over a wide range of temperatures, such as are required in avionics. However, a key component missing in these 1 micron photonic links is a high-power photodiode receiver with high linearity and high quantum efficiency. Freedom Photonics and the University of Virginia have collaborated to develop photodiodes which fill this need. The photodetectors are based on an optimized vertically illuminated modified uni-traveling carrier (MUTC) photodiode technology. We report devices with quantum efficiencies in excess of 80% at 1064 nm, with a 3-dB bandwidth of 28 GHz, for a 20µm diameter device. The same device size handles very high power, with a 1-dB compression of >16 dBm RF power at a 64-mA photocurrent. These photodiodes have a major impact on peak performance of a photonic link, supporting high link gain and large bandwidths. Additionally, the high linearity of these devices minimizes noise and signal distortion, maximizing spurious-free dynamic range (SFDR). These are the first photodiodes of this type which have been packaged and made commercially available for this target wavelength.

The recently proposed nonlinear optical processing method named Optical Dynamic Range Compression (ODRC) has been shown to reduce the burden on the dynamic range in photodetection and data acquisition and enhance the signal-to-noise ratio. Signals with a large dynamic range are compressed by the analog optical dynamic range compressor through a logarithmic-like transform before the photodetection and digitization and then recovered digitally. This powerful idea enables a larger detectable range, optical non-uniform quantization and signal statistics redistribution. To compress the high-dynamic-range optical signals, ODRC devices should have a nonlinear gain/loss that decreases /increases as input amplitudes increase, and is able to respond to the instantaneous power change. In this work, we explore the extension of this idea to create an optical limiter that harvests the optical power that would otherwise be wasted by the action of the limiter. In silicon nano-scale waveguide, two-photon absorption (TPA) and the induced free-carrier absorption (FCA) generate nonlinear absorption and limit the output power when the input power increases. The limiting curve can be sharpened to take effect at lower input power by introducing saturated Raman amplification in the forward propagation direction. Through the two-photon photovoltaic effect, the free carriers generated through the two-photon absorption are recycled so the optical energy lost in the compression is harvested as electrical power. The limiting transform can be tuned with the input pump power and the biasing voltage to best fit the statistics of the input signal. In applications where the device bandwidth is a concern, we showed that the carrier lifetime can be significantly reduced to tens pico-second through the carrier sweep-out with reverse bias.

Surface plasmon resonance (SPR) photonic crystal fiber (PCF) biosensors have recently attracted the attention of many researchers due to their unique properties which paved the way for many applications. Unlike the conventional configurations of SPR, the PCF-based sensors make remote sensing and real-time detection feasible. In addition, it is required to remove the conventional fiber cladding for obtaining a high sensitivity. In this paper, the use of Titanium Nitride (TiN) as a refractory plasmonic material in a highly sensitive plasmonic PCF is presented and analyzed by full vectorial finite element method. The proposed design relies on a silver layer as a plamonic material. Further, a thin coating layer of the abrasion-resistant alternative plasmonic material TiN is used to protect the silver layer from oxidation. In this investigation, the Ag/TiN configuration achieves high refractive index sensitivities of 9400 nm/RIU for both quasi-transverse electric (TE) and quasi-transverse magnetic (TM) modes by optimizing the design geometrical parameters. It is found out that the resonant peaks corresponding to the two polarized modes are extremely sensitive to the analyte refractive index variations. Moreover, the performance of the suggested design has high linearity. To the best of the authors’ knowledge, it is the first time to introduce TiN in a bimetallic PCF biosensor as a plasmonic material with high sensitivity.

In this paper, we are going to select low-cost plasmonic material and in accordance with special design structure which is economical with respect to high-cost noble metals with respect to conventional structure. We are going to analyze and compare the sensitivity of different metal with fixed special structure. The optical property of the material is size dependent and can be achieved by tuning micro and nanostructure design and selection of proper material. Due to change in optical property of macro and nano scales structure properties of materials, we can achieve for low-cost material with high-performance SPR sensor. Optical properties of submicron sized metal nanoparticles have drawn and simulated with nanometer precision for different material. The selection of nanostructure with proper material gives the best trade-o_ with the noble metal. The low-cost SPR sensor is needed for society to check pollution and other biochemical property and as biosensors.

A framework for simulating the elastic modes in waveguides taking into account the full tensorial nature of the stiffness is presented and implemented in an open-source finite element solver, FEniCS. Various approximations of the elastic-wave equation used in the analysis of stimulated Brillouin scattering are studied and their validity and applicability to micron-sized integrated waveguides is discussed.

Highly reliable and low-cost long-period corrugation and phase gratings based on a cascade of phase-shifted lithium niobate waveguides are theoretically analyzed, experimentally realized and characterized in a logical sequence. The realization of these phase-shifted waveguide gratings (LPWG) is subsequently achieved via a two-step proton exchange method. The measurement results have demonstrated that the maximum dip contrast is up to 19.73 dB and the narrowest full-width-at-half-maximum (FWHM) is close to 2.34 nm. Furthermore, for the cascaded pi-phase-shifted long-period waveguide gratings (LPWG), the two resonance wavelengths are symmetrically shifted away from the center wavelength in response to an increase in the number of LPWG sections incorporated.

This paper researches the applicability of an intuitive advertising system for large indoor environments using Visible Light Communication (VLC). This VLC based positioning system includes the use of the visible light signal to light the space and to transmit the information for travelers’ positioning and of advertising campaigns in the surroundings. White RGB-LEDs, whose original function is providing illumination, are used as transmitters due to the ability of each individual chip to switch quickly enough to transfer data. This functionality is used for communication where the multiplexed data can be encoded in the emitting light. The light signals emitted by the LEDs positioned in the area of the advertising campaign are interpreted directly by the customers’ receivers. A SiC optical sensor with light filtering and demultiplexing properties receives the modulated signals containing the ID and the geographical position of the LED and other information, demultiplexes and decodes the data and locates the mobile device in the environment. Different layouts are analysed: square and hexagonal meshes are tested, and a 2D localization design, demonstrated by a prototype implementation, is presented. The key differences between both topologies are discussed. For both, the transmitted information, indoor position and motion direction of the customer are determined. The results showed that the LED-aided VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction as a function of time and to interact with information received.

This paper focuses on design of specific type of optical logic gates - universal gates (NAND and NOR). These gates are based on microring resonators (MRR) coupled both in series (for NAND gate) and in parallel (in case of NOR gate). Because of their simplicity in terms of fabrication, the MRRs are modulated through thermo-optic effect of silicon. The MRRs in the proposed devices act as input ports combined with a constant source of light at specific wavelengths. Thus, through different coupling configurations of the rings, the logic is obtained. Due to the architectural features of the devices, complements of these gates (AND, OR) can be obtained as well. Consequently, the proposed designs exhibit the behavior of universal gates and their complements simultaneously. In addition, using Optical Spectrum Analyzer (OSA) as well as Optical Oscilloscope, static and corresponding dynamic responses are illustrated. Furthermore, complementary parameters such as extinction ratio and speed are evaluated.

An optical system which consists of a transmitter array, a fiber array, and a receiver array, experience some signal loss and crosstalk as the signals travel from the transmitter to the receiver. Signal loss and crosstalk occur at the interface between the light source (Vertical Cavity Surface Emitting Laser, or the VCSEL) and the fiber array, and also at the interface between the fiber array and the detector (photodetector). In order to obtain the real-time analysis of the transmitted and crosstalk signals, optical convolution is employed in this work. Optical convolution of the radiated signals (from the VCSEL) and the fiber array is performed to determine the signal intensity at the receiver end and also the amount of crosstalk in the array system. Transmitted signal intensity and crosstalk are essential for defining signal integrity and reliability during the packaging of optoelectronic transmitter and receiver modules in an optical system. A theoretical analysis of transmitted and crosstalk signals is performed with various separation distances between the transmitter modules and the fiber array and with a zero separation distance between the fiber array and the photodetector. The analysis is also performed for a top-emitting VCSEL (for the planar transmitter module) and bottom-emitting VCSEL (for the multi-chip transmitter module). The optical convolution allows us to obtain the real-time and the actual transmitted and crosstalk signals at the receiver end of an optical array system. It also provides optical system performance analysis.

High-speed ray tracing for illumination optics using GPGPU was investigated. Optical simulation for illumination optics requires many rays tracing for precise simulation. Especially, optics for automotive LED lighting have small textures on the exit surface of the lens to diverge part of the light for satisfying specific illumination pattern which is required in the regulation. Many ray tracing requires much simulation times and it increases development cost. Recently, parallel computing using CPU and GPU has been used for accelerating computing speed and reported its merit in computer sciences. In this research, the ray tracing consists of two parts which are intersection searching and refraction calculation was done in parallel using CUDA, GPGPU API provided by NVIDIA. Interpolation calculations such as linear interpolation, Nagata triangular patch interpolation, and Nagata quadrilateral patch interpolation were used in intersection searching calculation. The results indicate that there is a possibility to accelerate ray tracing speed by using GPU. As a representative example, GPU ray tracing was about twice faster than the commercial software. In addition, error differences depend on the interpolation types for intersection calculation were observed. Moreover, the results indicate calculation error differences between single precision float calculation and double precision float calculation. In conclusion, even there are several issues such as errors from interpolation and calculation precision, accelerated ray tracing using GPU was achieved.

Surface-plasmon resonance (SPR) sensors are widely used in different applications. In the present study, a noble electric field sensing is done theoretically by surface-plasmon resonance (SPR) phenomena using a multilayer structure. A glass prism is coated with a two metal (gold) layers sandwiched with lithium-niobate (LiNbO₃) material. The electric field is applied to the first and third layer of the metal. The measured electric field sensitivity is based on the angle interrogation and applied an electric field. The required mathematical expressions are included in this paper and the results are verified with the help of COMSOL multiphysics and MATLAB software.

In this work, we present the model of plasmonic chrial nanolasers composed of aluminum-coated gallium-nitride (GaN) gammadions, which may lase with a high degree of circular polarization at room temperatures. Using the finite-element method, we examine resonant modes of the four-fold rotationally symmetric cavities of gammadions whose resonant frequencies lie in the gain spectrum of GaN. We find a degenerate doublet of resonant modes which can couple to plane waves in the far-field zone above gammadions. Their near-field profiles exhibit localized distribution in the arms of gammadions and a Fabry-Perot standing-wave pattern along the post. In practice, fabrication imperfections would inevitably spoil the four-fold rotation symmetry of gammadions. Typical perturbation could lift the degeneracy of doublet and leads to mixing of the two degenerate modes which may still output signals with observable handedness above gammadions. Considering a gammadion cavity with a single elongated arm, we show that the magnitude of dissymmetry factor of its resonant mode can be larger than unity. Our calculations are consistent with the experimental results, indicating that the right-handed gammadion cavities lase with a magnitude of dissymmetry factors near 1 at a wavelength of 364 nm. The dimensionless effective mode volume scaled by the cube of effective wavelength is 2.62, reflecting a modal distribution remarkably confined in the plasmonic structures and the capability of enhancing the spontaneous-emission rate noticeably. These chiral nanolasers with an ultrasmall footprint could be potentially utilized as future circularly-polarized photon source at the chip level.

Heat induced by electromagnetic absorption affects optical properties and experimental conditions. For this reason, thermal effects in optics remain important. In this work, we investigate thermal properties of a wire-grid polarizer (WGP). A WGP is a well-known optical polarizing device and easy to combine with planar structures such as microfluidic channel and other optical components. We analyzed thermal characteristics of a WGP by considering the effects of various geometric parameters: wire-grid period, height, and fill factor. For far-field calculation of optical characteristics, rigorous-coupled wave analysis (RCWA) has been used with 40 spatial harmonics. Together, we solved wave-coupled heat transfer equation by 2D finite element method (FEM) for computing electromagnetic-thermal characteristics. 2D FEM calculation was verified with RCWA and 3D FEM. From the analysis, it was shown that a fill factor was the most dominant geometrical parameter for near-field thermal extinction. In addition, TM polarized light has higher local temperature T_max = 354.5 K than that of TE polarized light T_max = 331.7 K with an incident power at 0.1 mW/μm². Polarization switching was found to induce thermal extinction of 4.78 dB with a temperature difference ▵T = 54.3 K in an identical WGP structure. Furthermore, the ratio of steady-state time was almost uniform within 15%, because the heat transfer mechanism is almost identical for TE and TM polarization. Time scale was on the order of μs. We expect this result to be useful for the integration of WGPs in polarization-sensitive thermal switching applications.

In this paper, metallo-dielectric core-shell Yagi-Uda nanoantennas (NAs) are reported and optimized using 3D finite different time domain (FDTD) method and particle swarm optimization (PSO) technique to maximize the directivity. The suggested design has a silicon rectangular prism with spherical or rectangular silver core to improve the directivity and radiation efficiency. The proposed design with rectangular prism silver core achieves radiation efficiency of 77.23 % with a directivity of 18.41 at a wavelength of 500 nm. However, the directivity is increased to 21.22 with a radiation efficiency of 69.15 % with spherical-core based structure. The achieved enhancement is attributed to the elements shape in addition to the metallo-dielectric structure. Further, the silicon dielectric shell exhibits magnetic mode with high refractive index, as well as the surface plasmon mode supported by the silver core.

Systematic investigation of temperature-dependence on thermal quenching of X-ray luminescence (XL) from various single perovskite crystals was carried out. In the family of methylammonium lead halide perovskites (MAPbX₃, MA = methylammonium, X= Cl, Br or I), the quenching temperature of XL decreases from Cl to I. According to our analysis, such behavior is strongly affected by their corresponding decrease of thermal activation energy ▵E_q from 53 ± 3 to 6 ± 1 meV. Different concentrations of Bi³⁺-doped MAPbBr3 are also prepared and both four-point probe measurement and X-ray thermoluminescence (TL) confirms the successful doping. When we dope MAPbBr3 with Bi³⁺, Γ₀/Γ_v increases to 78 ± 18 for crystal with Bi/Pb ratio of 1/10 in precursor solution.

An enhanced multifunctional biosensor based on surface plasmon resonance is proposed and studied based on alcohol mixture filled photonic crystal fiber (PCF). The suggested biosensor has an alcohol mixture housed into a central hole which operates as a temperature dependent material. In addition, a gold nano-rod is attached at the inner surface of a large hole which is infiltrated with the analyte under study. Accordingly, both analyte refractive index and temperature sensing can be achieved using the reported biosensor where the guided core modes in the central hole can be coupled to the surface plasmon modes around the gold nano-rod. The sensitivity of the proposed biosensor is maximized by studying the effects of the structure geometrical parameters. In this regard, full-vectorial finite element method is used throughout the numerical analysis with perfect matched layer boundary conditions. The multifunctional alcohol mixture filled PCF sensor achieves very high temperature sensitivity of 13.1 nm/℃ with very high analyte refractive index sensitivity of 12700 nm/RIU. According to the literature review, the achieved refractive index and temperature sensitivities are higher than those for similar recent sensors in the same sensing range.

Supercontinuum generation (SCG) is the production of continuous spectral broadening. Efficient SCG is affected by the group velocity dispersion (GVD), nonlinear characteristics, waveguide geometrical parameters, and pump wavelength. Photonic crystal fibers (PCFs) offer promising advantages over standard fibers such as desirable dispersion properties and controllable mode area. Silicon (Si) is known for its large refractive index which enhances the nonlinear effect in silicon waveguides. The promising properties of silicon is combined with the strong characteristics of photonic crystals in a silicon-core PCF to broaden the spectrum. The effect of varying the pump power, and input pulse wavelength on the broadening bandwidth is studied. The modal characteristics of the reported PCF are calculated using full vectorial finite element method (FV-FEM) with perfectly matching layers (PML) boundary conditions. In this investigation, the effective mode index, dispersion profile of the fundamental quasi TM-mode of the silicon-based PCF are simulated to quantify the performance of the suggested design. The simulation results show that the proposed PCF produces spectral broadening spanning the wavelength range 1000 – 3000 nm with bandwidths ranging from 892 ± 50 to 1659 ± 50 nm at both telecommunications’ wavelengths 1.3 μm and 1.55 μm as well as at the zero dispersion wavelength (ZDW) of 2.0 μm through a device length of 10 mm. It is also found that increasing the pump wavelength from 1.3 μm to 2.0 μm widens the SC spectra by 715 ± 50 nm.

Micro-structured fiber (MF) devices such as polarization rotators, polarization filters, and polarization splitters have been widely used in optical communication systems. The concept of multifunctional photonic device becomes a new trend in optical systems. Therefore, it is essential to propose a new and compact multifunctional MF widely known as photonic crystal fiber (PCF) devices. In this paper, a compact polarization splitter that operates at two telecommunication wavelengths (1.31 μm or 1.55 μm) is designed. The proposed splitter is based on plasmonic tellurite dual core PCF in order to split the x and y polarization modes at wavelengths of 1.31 μm or 1.55 μm at the same device length. The nematic liquid crystal is selectively infiltrated in the cladding air holes to increase the birefringence in the introduced design. Further, the central hole is filled by a gold nanowire. The simulation results are obtained by using full vectorial finite element method with perfect matched layer boundary conditions. The numerical results reveal that the suggested splitter can split the x and y polarized modes at λ=1.31 and 1.55 μm at a short device length of 131.0 μm. The obtained crosstalk is -38 dB and -48 dB with bandwidths of 58 nm and 48 nm at λ= 1.31 μm for x and y polarized modes, respectively. In addition, crosstalk of -56 dB and -47 dB are achieved with bandwidths of 124 nm and 88 nm at λ= 1.55 μm for x and y polarized modes, respectively.

In missile applications, countermeasures are one of reasons for enhanced rate of false alarm. Aiming to o decrease false alarm rate, algorithms are used but it would be useless for some kind of countermeasures. Adding benefits of two or more wavelengths to seeker subsystem makes overall system more robust to countermeasures. In this study, first critical missile parameters will be given. Then; proposed short-wave infra-red and four quadrant method will be discussed. In addition; two different optical designs have been made for short-wave infra-red imaging and four quadrant systems. Optical designs performances have been illustrated in simulation results. Furthermore, opto-mechanical design of the dual mode seeker is illustrated. Finally, conceptual design of dual mode seeker will be summarized.

Compact seeker design is important in missile application. Main reason is the challenging allocation of drag coefficient reduction, performance/mass ratio and flight motor performance. All of these factors are tried to be optimized in an iterative manner for a couple of periods. However, because of the disturbing nature of the vibration of missiles, gimbals and vibration isolation/suppression methods are popular. Depending on the frequency of the vibration, old fashioned gimbal approaches can end up in an increase of the missile diameter to embody complex mechanisms to eliminate vibration effect. New proposed methods are vulnerable to jitter on image. In order to keep the diameter of the missile at certain level, complex gimbal subsystems can be removed from seeker. Not to be affected from the jitter on image, piezo actuator system can be used. In this study; an optical design and production of the camera module is conducted. Performance of the camera module is analyzed in simulation and tested in laboratory. After that, target is simulated in the collimator system to illustrate the performance of the module. Later, camera module performance is tested under the vibration test profile with automatic target acquisition algorithm to compare results of the system objectively. Finally, analyzes are performed to show piezo actuator effects on vibration test profile.

We consider four different laser arrangements with the nonlinear loops of Kerr type, and discuss square wave pulse operation using modeling based on delay differential equation (DDE) approach. We reduce DDE models to 1D maps, which enable square wave operation and analyze numerically the possible dynamical scenarios of the square wave evolution.

We modeled Multilayer Perceptron and Extreme Learning Machine Artificial Neural Networks (ANNs) for computing band structures (BSTs) and photonic band gaps (PBGs) of 2D and 3D photonic crystals (PhCs). We aim at providing fast ANN models which might boost the computations of BDs and PBGs regarding electromagnetic solvers. The case studies considered 2D and 3D PhCs with different lattices, geometries, and materials. Datasets for ANN training were built by varying the geometric shapes' dimensions and the dielectric constants of the case-study PhCs. We demonstrate simple and fast-training ANNs capable of providing accurate BSTs and PGBs through speedy computations.

In this paper, we propose a systematic approach to controllably fabricate silver nanoparticles, dendrites and nanovoids on porous template based on silicon and two-step wet process. Geometry of metallic structures was managed by variation of dopant type of silicon, regimes of template formation and deposition of silver. General models of each structure were developed and studied for distribution and strength of electric field arising in them under 473, 633 and 785 nm lasers. Simulation results revealed reasons of variable activity of fabricated structures in surface enhanced Raman spectroscopy, which allowed to define optimal conditions of analysis of target molecules.

Anisotropic materials can be multilayer stacks made from isotropic-isotropic, uniaxial-uniaxial or uniaxial-isotropic layers. Under certain conditions, these multilayer stacks can be modeled as a bulk anisotropic medium using effective medium theory. In this work, the effective permittivity tensor of arbitrary anisotropic layers is first derived using effective medium theory. Thereafter the Berreman matrix method is used to analyze electromagnetic propagation in this effective bulk medium. The overall transmittance and reflectance are investigated as a function of the thickness of the layers, number of layers, wavelength and the incident angle. Illustrative examples of stacks made from uniaxial-uniaxial layers and uniaxial-isotropic layers are provided. The uniaxial layers are, in turn, made from a sandwich of two isotropic layers. An example of a transmission filter comprising a multilayer stack on a substrate is also discussed, along with comparison with experimental observations.