This PDF file contains the front matter associated with SPIE Proceedings Volume 9894, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

In this work we present a detailed analysis of bifurcation structures of cavity solitons (CSs) and determine the different dynamical regimes in the Lugiato-Lefever (LL) equation in the presence of anomalous and normal chromatic dispersion regimes. Such an analysis has been shown to also increase our understanding of frequency combs (FCs). A FC consists in a set of equidistant spectral lines that can be used to measure light frequencies and time intervals more easily and precisely than ever before. Due to the duality between CSs in microcavities and FCs, we can gain information about the behavior of FCs by analyzing the dynamics of CSs. In the anomalous dispersion case bright CSs are organized in what is known as a homoclinic snaking bifurcation structure. In contrast, in the normal dispersion regime dark CSs are organized differently, in a structure known as collapsing snaking. Despite the differences in bifurcation scenarios, both types of CSs present similar temporal instabilities.

A new approach to design waveguides for supercontinuum generation through dispersive wave emission from optical wave-breaking is proposed in this work. In two steps, the spectral broadening is analytically related to the dispersion curve, and the cross-section of a waveguide is optimized in a few iterations to fit such dispersion profile and, consequently, the target output bandwidth. This strategy does not only improve the efficiency of design tasks, but also provides new insights into the underlying nonlinear processes.

We show that modulation instability (MI) can be suppressed in vertical external cavity surface emitting lasers (VECSELs) by introducing a periodic spatio-temporal modulation of the pump profile which in turn allows a simple flat-mirror configuration. The stability analysis of such pump modulated flat-mirror VECSELs is performed by a modified Floquet method and results are confirmed by full numerical integration of the model equations. It is found that the amplitude of the modulation as well as its spatial and temporal frequencies are crucial parameters for high spatial beam quality emission. We identify regions of complete and partial stabilization in parameter space for VECSELs with different external cavity lengths. The proposed method is shown to efficiently stabilize VECSELs with cavity lengths ranging from millimetres up to centimetres. However, the applicability of this method becomes limited for micro-meter-long cavities due to strong intrinsic relaxation oscillations.

We analyze numerically and experimentally the pattern formation process in an optical system composed of a bulk photorefractive crystal subjected to a single optical feedback. In this configuration, the system admits an homogeneous solution for low coupling strength. Increasing the coupling strength leads to a sub-critical bifurcation which leads to a pattern state. Such a bifurcation gives access to a well-defined hysteresis. In this paper we demonstrate that the size of the bistable area can be adjusted by different system parameters such as the intensity of the input beam, the power of an external background illumination and more interestingly by the feedback mirror tilt angle.

We present the essential features of the dissipative parametric instability, in the universal complex Ginzburg- Landau equation. Dissipative parametric instability is excited through a parametric modulation of frequency dependent losses in a zig-zag fashion in the spectral domain. Such damping is introduced respectively for spectral components in the +ΔF and in the -ΔF region in alternating fashion, where F can represent wavenumber or temporal frequency depending on the applications. Such a spectral modulation can destabilize the homogeneous stationary solution of the system leading to growth of spectral sidebands and to the consequent pattern formation: both stable and unstable patterns in one- and in two-dimensional systems can be excited. The dissipative parametric instability provides an useful and interesting tool for the control of pattern formation in nonlinear optical systems with potentially interesting applications in technological applications, like the design of mode- locked lasers emitting pulse trains with tunable repetition rate; but it could also find realizations in nanophotonics circuits or in dissipative polaritonic Bose-Einstein condensates.

Using the Fourier Modal Method for gratings with Kerr media [J. Opt. Soc. Am. B 31, 2371 (2014)] we demonstrate that low energy Optical Bistability for normally incident light field can be observed by strong nonlinear light-matter interactions in a Silicon Nitride waveguide-grating with 2-D periodicity. Finite divergence of the incident light beam has been taken into account in our numerical study and the gratings are designed to observe bistable behavior in direct transmitted light inside the optical telecommunication C-band (1520 nm-1570 nm). The waveguide grating structures are fabricated from PECVD synthesized Silicon Nitride thin film on top of quartz with standard electron beam lithography and reactive ion etching techniques. We aim to demonstrate this phenomenon experimentally using a tunable narrow line-width pulsed laser. Our resonant nanostructures may find applications in free space all-optical information processing and all-optical switching.

Optical time lenses have proven to be very versatile for advanced optical signal processing. Based on a controlled interplay between dispersion and phase-modulation by e.g. four-wave mixing, the processing is phase-preserving, and hence useful for all types of data signals including coherent multi-level modulation formats. This has enabled processing of phase-modulated spectrally efficient data signals, such as orthogonal frequency division multiplexed (OFDM) signals. In that case, a spectral telescope system was used, using two time lenses with different focal lengths (chirp rates), yielding a spectral magnification of the OFDM signal. Utilising such telescopic arrangements, it has become possible to perform a number of interesting functionalities, which will be described in the presentation. This includes conversion from OFDM to Nyquist WDM, compression of WDM channels to a single Nyquist channel and WDM regeneration. These operations require a broad bandwidth nonlinear platform, and novel photonic integrated nonlinear platforms like aluminum gallium arsenide nano-waveguides used for 1.28 Tbaud optical signal processing will be described.

Versatile and easy to implement methods to generate arbitrary optical waveforms at high repetition rates are of considerable interest with applications in optical communications, all-optical signal processing, instrumentation systems and microwave signal manipulation. While shaping sinusoidal, Gaussian or hyperbolic secant intensity profiles is commonly achieved by means of modulators or mode-locked lasers, other pulse profiles such as parabolic, triangular or flat-top shapes still remain challenging to synthesize. In this context, several strategies were already explored. First, the linear pulse shaping is a common method to carve an initial ultrashort pulse train into the desired shape. The line-by-line shaping of a coherent frequency comb made of tens of spectral components was also investigated to generate more complex structures whereas Fourier synthesis of a few discrete frequencies spectrum was exploited to efficiently generate high-fidelity ultrafast periodic intensity profiles. Besides linear shaping techniques, several nonlinear methods were implemented to benefit from the adiabatic evolution of the intensity pulse profile upon propagation in optical fibers. Other examples of efficient methods are based on the photonic generation involving specific Mach-Zehnder modulators, microwave photonic filters as well as frequency-to-time conversion. In this contribution, we theoretically and experimentally demonstrate a new approach enabling the synthesis of periodic high-repetition rate pulses with various intensity profiles ranging from parabola to triangular and flat-top pulses. More precisely by linear phase and amplitude shaping of only four spectral lines is it possible to reach the targeted temporal profile. Indeed, tailoring the input symmetric spectrum only requires the determination of two physical parameters: the phase difference between the inner and outer spectral sidebands and the ratio between the amplitude of these sidebands. Therefore, a systematic bidimensional analysis provides the optimum parameters and also highlights that switching between the different waveforms is achieved by simply changing the spectral phase between the inner and outer sidebands. We successfully validate this concept with the generation of high-fidelity ultrafast periodic waveforms at 40 GHz by shaping with a liquid cristal on insulator a four sideband comb resulting from a phase-modulated continuous wave. In order to reach higher repetition rates, we also describe a new scenario to obtain the required initial spectrum by taking advantage of the four-wave mixing process occurring in a highly nonlinear fiber. This approach is experimentally implemented at a repetition rate of 80-GHz by use of intensity and phase measurements that stress that full-duty cycle, high-quality, triangular, parabolic or flat-top profiles are obtained in full agreement with numerical simulations. The reconfigurable property of this photonic waveform generator is confirmed. Finally, the generation of bunch of shaped pulses is investigated, as well as the impact of Brillouin backscattering.

The generation of picosecond pulse trains has become of great interest for many scientific applications. However, even though different techniques of nonlinear compression have been developed for optical fibers in the anomalous dispersion regime, only a few exist for normally dispersive fibers. Here, we describe a new method based on the generation of a strong nonlinear focusing effect induced by the cross phase modulation of a high power 40-GHz beat-signal on its orthogonally polarized interleaved weak replica. More precisely, while the normally dispersive defocusing regime induced a nonlinear reshaping of a high power 40-GHz sinusoidal signal into successively parabolic then broad and sharp square pulses, it also progressively close a singularity at its null point characterized by steeper and steeper edges. Here we show that the cross phase modulation induced by this nonlinear dark structure on a weak interleaved orthogonally polarized replica then turns out the normally dispersive regime into a focusing dynamics. This phenomenon is similar to the polarization domain wall effect for which the energy of a domain is strongly localized and bounded by the commutation of both orthogonally polarized waves. In other words, since a particle in a gradually collapsing potential, the energy contained in the weak interleaved component is found to be more and more bounded and is thus forced to temporally compress along the fiber length, thus reshaping the initial beat-signal into a train of well-separated short pulses. We have experimentally validated the present method by demonstrating the temporal compression of an initial 40-GHz beat-signal into a train of well separated pulses in different types of normally dispersive fibers. To this aim, an initial 40-GHz beat-signal is first split into 2 replica for which one is half-period delayed and 10-dB attenuated before polarization multiplexing in such a way to generate a strongly-unbalanced orthogonally-polarized interleaved signal. The resulting signal is then amplified and injected into the fiber under-test. In first fibers of 1 and 2 km (D = -15 ps.km-1.nm-1, γ = 2.3 W-1.km-1, α = 0.2 dB.km-1), we have observed the nonlinear focusing of the initial 40-GHz sinusoidal signal input into a train of 5.5-ps pulses. By decreasing the dispersion coefficient down to D = -2.5 ps.km-1.nm-1 in such a way to exacerbate the nonlinear defocusing effect of the strongest component far beyond the wave breaking, we have successfully compressed the orthogonally polarized 40-GHz beat-signal into well-separated 2.5-ps pulses after 5 km of propagation for a total input power of 28 dBm. We then studied the effect of total power on the compression ratio, and showed that compression is more efficient with higher total power, even after the wave breaking phenomenon. We followed by showing that the power ratio between the two polarization axes is closely linked to the compression factor, as the higher the power difference between the two axes, the better compression. Finally, our experimental results are in excellent agreement with our numerical predictions.

The field of fiber optics nonlinearity is more discussed last years due to such remarkable enhancement in the nonlinear processes efficiency. In this paper, and for optical performance monitoring (OPM), a new achievement of nonlinear effects has been investigated. The use of cross-phase modulation (XPM) and four-wave mixing (FWM) effects between input optical signal and inserted continuous-wave probe has proposed for impairments monitoring. Indeed, transmitting a multi-channels phase modulated signal at high data rate (1 Tbps WDM Nyquist NRZ- DP-QPSK) improves the sensitivity and the dynamic range monitoring. It was observed by simulation results that various optical parameters including optical power, wavelength, chromatic dispersion (CD), polarization mode dispersion (PMD), optical signal-to-noise ratio (OSNR), Q-factor and so on, can be monitored. Also, the effect of increasing the channel spacing between WDM signals is studied and proved its use for FWM power monitoring.

A soliton explosion is a dramatic effect, whereby a pulse circulating in a mode-locked laser dissipates and then remarkably reforms within a few roundtrips. Our group recently reported the first observation of such explosions in an all-fibre laser. Here, we expand on our initial work, reporting a detailed numerical and experimental study of the dynamics and characteristics of soliton explosions. Our experiment is based on a passively mode-locked Yb-doped fiber laser, where explosions occur close to the boundary between stable and noise-like operation. To capture the events, we use the dispersive Fourier transformation to record, in real time, the pulse-to-pulse spectra emitted by the laser. We explore a variety of operating conditions by systematically adjusting the laser pump power and its cavity length. We also use a realistic model based on a set of generalized nonlinear Schrodinger equations to simulate the explosion dynamics. We find that the explosion dynamics can be influenced by adjusting the operating conditions. As a general trend, the frequency of the events increases as the conditions move closer to the boundary of unstable operation. In fact, when sufficiently close to the boundary, the “explosions” can even become more frequent than ordinary pulses. Moreover, our simulations reveal that complex features in the spectral and temporal profiles of the explosion events can be explained in terms of a multi-pulsing instability. Finally we have examined how the statistics of the events depend on the laser geometry and also whether such explosions indicate the existence of a “strange attractor”.

In this paper, we deal with optical Airy beams propagating in a nonlinear photorefractive crystal. We first study the dynamics of one Airy beam and show that it evolves in two stages: when we apply a focusing nonlinearity on the crystal, the output beam first turns into an off-shooting soliton. Then we observe a relaxation-type dynamics towards a focused redistributed solution where an Airy-like profile and the previous off-shooting soliton are superimposed. In a second step we add a second Airy beam counterpropagating in the nonlinear crystal. We show that the interactions induced by counter-propagating Airy beams allow for achieving complex waveguiding structures that would otherwise require the counter-propagating interactions of more than two Gaussian beams. Finally we present that the stationary waveguide structures shown previously can be switched to spatiotemporally varying structures by tuning the photorefractive nonlinearity of the system. The system dynamically evolves from a steady-state regime to time-dependent stable and turbulent states where the off-shooting solitons begin to move first periodically then erratically around specific Airy-induced output positions. These localized spatiotemporal dynamics are induced by the peculiar energy distribution of the counterpropagating Airy beams.

We present a new experimental technique based on the analysis of beam self-action to measure optical nonlinearity in planar waveguides. This technique is applied to analyze the nonlinear properties of slab chalcogenide waveguides that can develop Kerr induced self-focusing or self-defocusing, depending upon the waveguide structure and composition. Optical nonlinearity in chalcogenide waveguide is studied in the 1200 nm to 1550 nm wavelength range in femtosecond regime. Results of the proposed technique compare favorably with n₂ values obtained with the Z-scan technique. In addition, beam self-trapping in the chalcogenide waveguides due to material photosensitivity is also observed.

We briefly review the technology of advanced nonlinear resonators for all-optical gating with a specific focus on the application of high-performance signal sampling and on the properties of III-V semiconductor photonic crystals

We investigate a simple way to create dynamic photonic crystals with different lattice symmetry by interference of four non-coplanar laser beams in colloidal solution of CdSe/ZnS quantum dots (QDs). The formation of dynamic photonic crystal was confirmed by the observed diffraction of the beams that have excited photonic crystal at the angles equal to that calculated for the corresponding three-dimensional lattice (self-diffraction regime). Self-diffraction from an induced 3D transient photonic crystal has been discovered in the case of resonant excitation of the excitons (electron – hole transitions) in CdSe/ZnS QDs (highly absorbing colloidal solution) by powerful beams of mode-locked laser with picosecond pulse duration. Self-diffraction arises for four laser beams intersecting in the cell with colloidal CdSe/ZnS QDs due to the induced 3D dynamic photonic crystal. The physical processes that arise in CdSe/ZnS QDs and are responsible for the observed self-action effects are discussed.

We report implementation of compact cascaded multicrystal scheme for single-pass second-harmonic-generation (SHG), using birefringent crystal, for continuous-wave (cw) deep ultraviolet (UV) generation. The system comprises of 4 cascaded stages, is based on critical phase-matched interaction in β-BaB₂O₄ (BBO), and pumped by a cw singlefrequency green source at 532 nm. A deep-UV cw output power of 37.7 mW at 266 nm has been obtained with a high passive power stability of 0.12 % rms over more than 4 hours in Gaussian spatial beam quality with a circularity of >70%.

Shock waves are well-known nonlinear waves, displaying an abrupt discontinuity. Observation can be made in a lot of physical fields, as in water wave, plasma and nonlinear optics. Shock waves can either break or relax through either catastrophic or regularization phenomena. In this work, we restrain our study to dispersive shock waves. This regularization phenomenon implies the emission of dispersive waves. We demonstrate experimentally and numerically the generation of spatial dispersive shock waves in a nonlocal focusing media. The generation of dispersive shock wave in a focusing media is more problematic than in a defocusing one. Indeed, the modulational instability has to be frustrated to observe this phenomenon. In 2010, the dispersive shock wave was demonstrated experimentally in a focusing media with a partially coherent beam [1]. Another way is to use a nonlocal media [2]. The impact of nonlocality is more important than the modulational instability frustration. Here, we use nematic liquid crystals (NLC) as Kerr-like nonlocal medium. To achieve shock formation, we use the Riemann condition as initial spatial condition (edge at the beam entrance of the NLC cell). In these experimental conditions, we generate, experimentally and numerically, shock waves that relax through the emission of dispersive waves. Associated with this phenomenon, we evidence the emergence of a localized wave that travels through the transverse beam profile. The beam steepness, which is a good indicator of the shock formation, is maximal at the shock point position. This latter follows a power law versus the injected power as in [3]. Increasing the injected power, we found multiple shock points. We have good agreements between the numerical simulations and the experimental results. [1] W. Wan, D. V Dylov, C. Barsi, and J. W. Fleischer, Opt. Lett. 35, 2819 (2010). [2] G. Assanto, T. R. Marchant, and N. F. Smyth, Phys. Rev. A - At. Mol. Opt. Phys. 78, 1 (2008). [3] N. Ghofraniha, L. S. Amato, V. Folli, S. Trillo, E. DelRe, and C. Conti, Opt. Lett. 37, 2325 (2012).

We present a new scientific software which is able to simulate any experimental setup based on photon pair creation with spontaneous parametric down-conversion in periodically poled crystals. Moreover, our software is able to optimise experimental parameters for the sake of high down-conversion efficiency and quantum performance. Given the optional input of any relevant individual experimental setup, the large number of output parameters and plots and the user-friendly intuitive graphical user interface, we believe that our software can be a helpful tool to any experimentalist who uses the quasi-phase-matching technique to generate collinearly propagating photon pairs.

A re-visitation of the well known free space Mach Zehnder interferometer is here reported. Coexistence between one-photon and two-photons interference from collinear color entangled photon pairs is investigated. This is seen to arise from an arbitrarily small unbalance in the arm transmittance. The tuning of such asymmetry is reflected in dramatic changes in the coincidence detection, revealing beatings between one particle and two particle interference patterns. Our configuration explores new physics of the real Mach Zehnder interferometer especially useful for quantum optics on a chip, where the guiding geometry forces photons to travel in the same spatial mode.

Two series of nanodisk arrays were designed. The first one was fabricated out of a silicon-on-insulator (SOI) wafer using electron-beam lithography and a reactive-ion etching process. The top layer of a SOI wafer is a 260-nm layer of monocrystalline (100)-cut silicon. We consider three square 400x400 μm2 arrays distinguished by the disk diameter values – 340, 345 and 360 nm, respectively; the period of the nanodisk ordering in the array amounted to 2.85 μm – this value allows for regarding the disks as isolated ones in terms of optical coupling. The nanodisk diameter choice specifies the magnetic dipolar (MD) resonance wavelength [1]. The second series of arrays was made of a 130-nm hydrogenated amorphous silicon (a-Si:H) film grown by plasma-enhanced chemical vapor deposition on a thin glass substrate. In order to study the nonlinear optical response of the nanodisks and verify the multipole resonances roles, we conducted third-harmonic generation (THG) spectroscopy measurements using a tunable (1.0-1.5 μm) optical parametric oscillator (200 fs pulses with the repetition rate of 76 MHz) pumped by a Ti:Sapphire laser. The laser beam waist diameter was set at 11 μm by an aspheric lens. The full thickness of both the SOI and glass wafers (∼500 μm each) was less than the waist depth. The resulting peak intensity reached the values of about 1 GW/cm2 in the sample plane. The laser beam polarization was linear as controlled by a Glan-Taylor laser prism. The transmitted and collimated THG signal was selected by a set of blue filters and detected by a photomultiplier tube connected with a lock-in amplifier. This signal was proven to be of TH origin by checking its cubic dependence on the pump power and by direct measurements of its spectrum. It was also verified that the THG beam was polarized parallel to the orientation of the pump beam polarization. It should be pointed out that the penetration depth of the THG into silicon does not exceed the nanodisk height. The experimental technique [2] of nonlinear spectroscopy consists of defining the ratio of the TH signal from the nanostructured area to the successively measured signal from the nearby area where the top layer of silicon was etched away (in the case of the SOI wafer) or to the signal from a reference channel (in the case of the a-Si:H film). These ratios reveal the enhanced third-order optical response; moreover, the dispersion of the silicon nonlinear susceptibility is thereby taken into account. The resultant normalized THG signal represents the nanodisks and their resonant contribution. In this contribution, we have shown the third-harmonic response of silicon nanodisks at their electric and magnetic dipolar resonances. The enhanced up-conversion efficiency at the MD resonance of the nanodisks is observed, whereas the electric dipolar resonance yields less nonlinear conversion. The maximum area-normalized THG enhancement is around 30. In this work, the observed linear and nonlinear spectra are confirmed by numerical calculations. [1] I. Staude, et al., ACS Nano, 7, 7824 (2013). [2] M.R. Shcherbakov, et al., Nano Lett., 14, 6488 (2014).

High flux of hyperentangled photons entails collecting the two-photon emission over relatively wide extent in frequency and transverse space within which the photon pairs are simultaneously entangled in multiple degrees of freedom. In this paper, we present a numerical approach to determining the spatial-spectral relative-phase and time-delay maps of hyperentangled photons all over the spontaneous parametric down conversion (SPDC) emission cone. We consider the hyperentangled-photons produced by superimposing noncollinear SPDC emissions of two crossed and coherentlypumped nonlinear crystals. We adopt a vectorial representation for all parameters of concern. This enables us to study special settings such as the self-compensation via oblique pump incidence. While rigorous quantum treatment of SPDC emission requires Gaussian state representation, in low-gain regime (like the case of the study), it is well approximated to the first order to superposition of vacuum and two-photon states. The relative phase and time-delay maps are then calculated between the two-photon wavepackets created along symmetrical locations of the crystals. Assuming monochromatic plane-wave pump field, the mutual signal-idler relations like energy conservation and transversemomentum conservation define well one of the two-photon with reference to its conjugate. The weaker conservation of longitudinal momentum (due to relatively thin crystals) allows two-photon emission directions coplanar with the pump beam while spreading around the perfect phase-matching direction. While prior works often adopt first-order approximation, it is shown that the relative-phase map is a very well approximated to a quadratic function in the polar angle of the two-photon emission while negligibly varying with the azimuthal angle.

Creation of effective means of protection from laser radiation of high power requires the development of optical materials (working substance), with their transparence being decreased sharply above a certain critical value of the laser intensity due to the appearance of non-linear optical properties (limiting threshold). Based on the threshold model, the working substance of the optical limiter was characterized. Experimental data of z-scan with open aperture are used to determine the nonlinear optical parameters of solutions of dimeric phthalocyanine complexes of Mg and Zn of J-type in tetrahydrofuran (THF) and thin films of their conjugates with single-walled carbon nanotubes (SWCNTs). The output characteristic (output (peak) fluence vs input (peak) fluence), that describes the basic properties of optical limiters, was obtained with the fixed location of the optical limiter. Dimeric phthalocyanine complexes were found to have low limiting threshold ~ 2 MW·cm^-2 and high value of the nonlinear absorption coefficient ~ 330 and 370 cm GW^-1, respectively. Conjugates of these dimeric phthalocyanines with SWCNTs have been produced for the improving of the limiting parameters and increasing of the optical nonlinearity. Size of J-type dimeric phthalocyanine complexes of Mg and Zn were determined by the scanning electron microscopy (SEM). The atomic force microscopy (AFM) allowed to determine the dimensions of nanotubes. The structure parameters, such as diameter and defects as well as the strength of aggregates were estimated with the Raman spectroscopy. For our experiments, the lens with a focal length of 20 cm was used. As the laser radiation source, the Nd:YAG laser was used to generate pulses of 16 ns duration at a wavelength of 532 nm with the linearly polarized laser beam in the horizontal plane and a shape closed to Gaussian type.

We report main features of spectral compression of parabolic pulses in nonlinear optical fibers. It is shown that the variational analysis correctly describes evolution of pulse parameters during spectral compression. The model of cascade amplifier system employing spectral compression is developed to achieve superior spectral densities. The proposed configuration is promising as optical pulse preamplifier for operation in the high-energy pulse laser systems.

We developed an explicit analytical solution of FWM under the laser beam propagation in a medium with cubic nonlinear response in the framework of both plane wave approximation and long pulse duration approximation. We used the approach based on the problem invariants and assumption of equal pump-wave amplitudes. It is impossible to get the explicit solution of the problem under consideration without taking into account the problem invariants. The developed analytical solution allows providing a full analysis of FWM modes in the space of interaction parameters. We have shown, in particular, the existence of bistable mode for energy conversion from the pump waves to the signal wave. This mode of energy conversion is very important for FWM experiments explaining.

We investigate optical pulse localization at its propagation in 2D layered photonic crystal (PC) with cubic nonlinear response. In the case under consideration, a light localization takes place due to spatial solitons appearing in certain PC elements. Soliton velocity depends on its intensity and location in the PC. This results in sub-pulses velocities changing which reflect from the PC or transmit through the PC. The formation of soliton depends on input light intensity, duration of pulse and length of the elements from which the PC consists. The soliton may move with slow velocity inside the PC elements. Under certain conditions, the soliton can stop near the PC boundaries. This phenomenon can be used for data storage.

We numerically investigate the capabilities and advantages of Raman lasers based on integrated single-crystal diamond ring resonators. To this end, we first model continuous-wave (CW) Raman lasing action while taking into account the lasing directionality, the linear and nonlinear losses, and the coupling of the fields between the bus and ring sections of racetrack-shaped diamond ring resonators. We then consider the design of the ring resonators for a short-wavelength infrared (SWIR) and an ultraviolet (UV) Raman laser. Using our Raman lasing model, we determine the lasing directionality, pump threshold and lasing efficiency of the SWIR and UV devices. We find that both can yield efficient CW operation with SWIR and UV lasing slope efficiencies of 33% and 65 %, respectively. These results showcase the potential of integrated diamond ring Raman lasers for producing wavelengths that are challenging to generate with other types of integrated lasers.

We report the first realization of low-loss orientation-patterned gallium antimonide waveguides for frequency conversion in the mid-infrared. Planar waveguide structures were grown by molecular-beam epitaxy on periodically patterned gallium arsenide templates prepared by wafer bonding. Ridge waveguides were designed and fabricated from the planar structures. Record losses of 0.73 dB/cm in periodically oriented waveguides were measured at 2 μm.

In this paper two all optical packet forwarding architectures based on non linear effect in semiconductor optical amplifier in Mach-Zehnder configuration SOA-MZI are studied. The first architecture consist in combing flip flop functionality with the AND logic functionality in the same unit. Error free operation at 40 Gbps for two cascaded nodes is achieved. In the second architecture two separated units namely the flip flop and the AND logic gate are used. 100 Gbps bit rate is reached. At 40 Gbps error free operation is achieved for three cascaded nodes.

We proposed a novel 2×2 all optical packet switching router architecture supporting asynchronous, labelled and variablelength packet. A proof of concept through Matlab Simulink simulation is validated. Then we discussed the three possible scenarios to demonstrate the contention resolution technique based on deflection routing. We have showing that the contending packet is detected and forwarded according FIFO (First In First Out) strategy to another output.

In this paper, we compare the theoretical performance of two design methods that allow simultaneous phase matching of two arbitrary X⁽²⁾ processes along with the capability of adjusting their relative strength. The crystal of these 1-D aperiodic gratings is chosen to be the orientation-patterned gallium arsenide (OP-GaAs), which has been recently used in several devices for high power infrared beam generation. These single gratings placed in an optical parametric oscillator (OPO) or an optical parametric generator (OPG) can simultaneously phase match two optical parametric amplification (OPA) processes, OPA-1 and OPA-2, for converting the 2.1-μm pump laser radiation into the long-wave infrared (8-12 μm) in an idler-efficiency enhanced scheme. The first aperiodic grating design method (Method-1) relies on generating an aperiodic grating structure that has domain walls located at the zeros of the summation of two cosine functions each of which has a spatial frequency that equals one of the phase-mismatches of the two processes. In this method some of the domain walls are discarded considering the minimum domain length (D_min) that is achievable in the production process. The second design method (Method-2) relies on discretizing the crystal length with samples with a length that is much smaller than D_min and testing each sample’s contribution in such a way that the sign of the nonlinearity maximizes the magnitude sum of the real and imaginary parts of the Fourier Transform of the grating function at the relevant phase-mismatch spatial frequencies. Also, during the procedure, the smallest domain length is imposed to be D_min. In this paper, we present the results of Method-2 which we find that it produces a similar performance as Method-1 in terms of the maximization of the magnitudes of the Fourier peaks located at the phase-mismatches of the nonlinear processes while adjusting their relative strength. To our knowledge, we are the first to propose such aperiodic OP-GaAs gratings for efficient long-wave infrared beam generation based on simultaneous phase matching.

In this paper, we study the self-phase modulation on a sub-micro graphene waveguide to show the nonlinear optical properties of graphene. Self-modulation is one of the most popular nonlinear effects that has been observed due to selfinfluence of a mode propagation in third-order materials. This effects is capable to demonstrate the nonlinearity based the structure. Our study is aimed to show the appearance of SPM in considered waveguide as a common effect of nonlinear refraction to proof the capability of graphen on apply the based waveguide in nonlinear regime to access the desired parameters such as dimension and insertion power. An interest aspect is placed in this simulation may be conversion step-index to grade-index due to change from linear to the nonlinear that causes high confinement of light in waveguide.

The nonlinear absorption properties of Ag nanoprism arrays synthesized by nanosphere lithography have been investigated by z-scan measurements. A picoseconds and low repetition rate laser source has been used to excite the electronic component of the nonlinear optical response without inducing thermal effects on the samples. Spectral effects in the nonlinear absorption response have been highlighted by performing measurements at different wavelengths, matching the laser wavelength with the dipolar and the quadrupolar surface plasmon resonances of the synthesized nanoarrays. The nonlinear absorption properties of the samples have been also investigated as a function of the polarization of the laser source and dichroism effects have been revealed.

We present results of supercontinuum generation in highly nonlinear polarization maintaining photonic crystal fiber using various harmonics of sub-nanosecond passively Q-switched Nd:YAG microlaser. The pump source was a Nd:YAG microlaser generating 50 μJ energy 300 ps duration pulses at 1064 nm with kilohertz repetition rate. We demonstrated that we can expand the supercontinuum spectrum to cover the whole visible range and beyond using either first or second harmonic of our pump laser in simple experimental setups: supercontinuum extended from 400 nm to 1300 nm in case of λ_p = 1064 nm and from 400 nm to 900 nm in case of λ_p = 532 nm. We compared supercontinuum evolution and dependence on pump pulse energy in both cases. We also performed numerical simulations of supercontinuum generation in PCF by applying the traditional approach of solving generalized nonlinear Schrödinger equation (GNLSE) and also presented a new numerical simulation approach -deriving and solving equation for evolution of spectral components of pulse propagating in the PCF. In case of GNLSE approach, the simulated supercontinuum spectra display the same qualitative features as the ones measured in the experiment.

The development of methods of generation of ultrashort pulses (USP) of femto- and attosecond duration ranges with controlled parameters necessitates the theoretical study of features of their interaction with a matter [1]. Among such features that do not exist in case of “long” pulses should first of all be the nonlinear dependence of the photoprocess probability W on the USP duration (τ) [2] as well as the dependence on the carrier phase with respect to the pulse envelope (φ) [3-4]. It should be noted that if the dependence of the probability W on the phase φ manifests itself either only for very short pulses, when ωτ < 1 (ω is carrier frequency of the pulse), or in case of a nonlinear photoprocess [3], the function W(τ) can differ from a linear function in the limit ωτ> 1 too for fields of moderate strength, when the perturbation theory is applicable [2].

Publisher’s Note: This paper, originally published on 12 July 2016, was replaced with a corrected/revised version on 26 July 2016. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. We have developed a terahertz time domain spectroscopy system (THz TDS). For THz generation, optical rectification process and for detection, electro-optic sampling processes are used. Identical < 110 > cut ZnTe crystals are used for both generation and detection of THz radiation.This spectroscopy system can be used for the noninvasive and contactless electrical and optical characterizations of various samples. In this work spectroscopic measurements of pure, Chromium and Indium doped GaSe crystals within 0.4 THz to 3 THz range are taken by the developed set-up to study the dielectric response of the samples.

We present measurements of nonlinear refraction (NLR) and nonlinear absorption (NLA) of single crystalline gold nanosheets (single crystalline-GNSs) and sputter coated polycrystalline thin gold metal film hybridized with multilayer grapheme (MLG) using Z-Scan technique for near-infrared wavelengths (NIR) ranging from 700 nm to 900 nm. Single crystalline GNSs of 20 nm thickness were prepared through chemical synthesis. MLG was found to have few monolayers of graphene, usually between 1-7 layers with an average of 4 monolayer thickness. The composite of GNSs and MLG was prepared by drop casting GNSs on MLG. Z-Scan experimental was carried out using Ti:sapphire femtosecond pulsed laser (700 nm - 900 nm wavelength, 115-130 fs pulse width and 0.82 MHz-82 MHz repetition rate). Intensity dependence on open aperture Z-scan was studied in detail for all materials. The NLA of polycrystalline thin gold metal film was found to be fractionally higher than that of single crystalline-GNSs. This is thought to be due to field enhancement around of gold islands formed on polycrystalline thin gold metal film during sputtering process. At higher repetition rates NLA phenomenon is diminished due to the temperature accumulation effect. As the repetition rate decreases the nonlinear effect is enhanced. On the other hand MLG exhibited saturable absorption (NSA) . Z-Scan results for single crystalline and poly crystalline gold-MLG nanocomposite exhibit NSA characteristics. The measured NSA coefficient ‘α’ was found to be approximately ≈1.7×10^-5-4.5×10^-5 cmW^-1 which is lower than that of MLG, clearly demonstrating the effect of hybridization.

A transient chirped grating structure is formed by beam interferences in nonlinear photonic crystal waveguide. Pulse propagation in nonlinear transient grating media is investigated and its impact on the transmission dynamics is explored. The grating may not be stationary propagating but anharmonically oscillating. Thus, effective modification of the refractive index needs to be evaluated in detail.

UV generation via four-wave-mixing (FWM) in optical microfibres (OMFs) was demonstrated. This was achieved by exploiting the tailorable dispersion of the OMF in order to phase match the propagation constant of the four frequencies involved in the FWM process. In order to satisfy the frequency requirement for FWM, a Master Oscillator Power Amplifier (MOPA) working at the telecom C-band was connected to a periodically poled silica fibre (PPSF), producing a fundamental frequency (FF) at 1550.3 nm and a second harmonic (SH) frequency at 775.2 nm. A by-product of this second harmonic generation is the generation of a signal at the third harmonic (TH) frequency of 516.7 nm via degenerate FWM. This then allows the generation of the fourth harmonic (FH) at 387.6 nm and the fifth harmonic (5H) at 310nm via degenerate and nondegenerate FWM in the OMF.The output of the PPSF was connected to a pure silica core fibre which was being tapered using the modified flame brushing technique from an initial diameter of 125 μm to 0.5 μm. While no signal at any UV wavelength was initially observed, as the OMF diameter reached the correct phase matching diameters, signals at 387.6 nm appeared. Signals at 310 nm also appeared although it is not phase matched, as the small difference in the propagation constant is bridged by other nonlinear processes such as self-phase and cross phase modulation.

Light propagation in small-core photonic crystal fibers enables tight optical confinement over long propagation lengths to enhance light-matter interactions. Not only can photonic crystal fibers compress light spatially, they also provide a tunable means to control light-hypersound interactions. By exploring Brillouin light scattering in a small-core and high air-filling fraction microstructured fiber, we report the observation of Brillouin scattering from surface acoustic waves at lower frequencies than standard Brillouin scattering from bulk acoustic waves. This effect could find potential applications for optical sensing technologies that exploit surface acoustic waves.

Direct modulation of the bias voltage of a LTG-GaAs photomixer is exploited to modulate the signal generated at the frequency of the optical beat between two diode lasers at 820 nm. The photomixing signal is calculated from an expansion in power series of the amplitude of the modulation voltage and displays amplitude modulation sidebands equidistantly spaced to the frequency of the optical beat by integer multiples of the modulation frequency. Modulation at harmonics of the modulation frequency is allowed by the electrical nonlinear response of the photomixer, driven at low voltage by the saturation of the electron drift velocity. Coupling of an alternative voltage to the photomixer operated at zero-bias leads to bifrequency operation. Modulation of the photomixing signal and bifrequency operation of the photomixer are observed experimentally with an optical beat in the microwave regime.

A method based on optical heterodyning is proposed for measuring relative optical phases of pulses circulating in a synthetic photonic lattices. The knowledge of the phases can be further used for qualitative reconstruction of an eigenmode excitation spectrum in the synthetic photonic lattice.

For pulses propagating in fibers with a running refractive index wave, the pulse power could be drastically increased due to decrease of the pulse duration. We report temporal and spectral compression of the pulses and conditions for formation of soliton-like chirped pulses in nonlinear fibers with a running refractive index wave. We demonstrate 100- fold compression of the wave packets propagating in media with a running refractive index wave (down to sub-picosecond durations) achieved on lengths shorter than 10 cm. In addition, the modulation instability of wave packets will be studied in such media.

Delay systems subject to delayed optical feedback have recently shown great potential in solving computationally hard tasks. By implementing a neuro-inspired computational scheme relying on the transient response to optical data injection, high processing speeds have been demonstrated. However, reservoir computing systems based on delay dynamics discussed in the literature are designed by coupling many different stand-alone components which lead to bulky, lack of long-term stability, non-monolithic systems. Here we numerically investigate the possibility of implementing reservoir computing schemes based on semiconductor ring lasers. Semiconductor ring lasers are semiconductor lasers where the laser cavity consists of a ring-shaped waveguide. SRLs are highly integrable and scalable, making them ideal candidates for key components in photonic integrated circuits. SRLs can generate light in two counterpropagating directions between which bistability has been demonstrated. We demonstrate that two independent machine learning tasks , even with different nature of inputs with different input data signals can be simultaneously computed using a single photonic nonlinear node relying on the parallelism offered by photonics. We illustrate the performance on simultaneous chaotic time series prediction and a classification of the Nonlinear Channel Equalization. We take advantage of different directional modes to process individual tasks. Each directional mode processes one individual task to mitigate possible crosstalk between the tasks. Our results indicate that prediction/classification with errors comparable to the state-of-the-art performance can be obtained even with noise despite the two tasks being computed simultaneously. We also find that a good performance is obtained for both tasks for a broad range of the parameters. The results are discussed in detail in [Nguimdo et al., IEEE Trans. Neural Netw. Learn. Syst. 26, pp. 3301–3307, 2015]

We investigate the effect of phenomenological relaxation parameters on the third order optical nonlinearity of doped graphene by perturbatively solving the semiconductor Bloch equation. We focus on the contributions of optical transitions around the Dirac points, where the widely used linear dispersion relation is a good approximation. An analytic expression for the nonlinear conductivity at zero temperature can be obtained even if relaxation is included. With this analytic formula as a starting point, we construct the conductivity at finite temperature; and we illustrate the dependence of several nonlinear optical effects, such as third harmonic generation, Kerr effects and two photon absorption, and parametric frequency conversion.

Novel piezoelectric resonance laser calorimetry technique, based on impedance spectroscopy, is introduced for measuring low optical absorption coefficients of nonlinear-optical crystals. This method exploits dependence of crystal piezoelectric resonance frequencies on its temperature. Nonuniform temperature of the crystal heated by laser radiation is characterized by equivalent temperature that is directly determined by measuring frequency shift of certain piezoelectric resonance calibrated on temperature. Kinetics of crystal equivalent temperature during its interaction with laser radiation is obtained by measuring frequency kinetics of piezoelectric resonance. It is demonstrated that optical absorption coefficient can be determined from the linear slope of initial part of temperature kinetics. Basing on experiments with LiB₃O₅ and LiNbO₃ crystals it was proved that values of optical absorption coefficients determined from initial part and full time kinetics of equivalent temperature have almost the same values.

In current work optical properties of LiB₃O₅ (LBO) crystal with ultraviolet (UV) (λ= 266 nm) induced volume macroscopic defect (track) are investigated using novel piezoelectric resonance laser calorimetry technique. Pulsed laser radiation of 10 W average power at 532 nm wavelength, is consecutively focused into spatial regions with and without optical defect. For these cases exponential fitting of crystal temperature kinetics measured during its irradiation gives different optical absorption coefficients α₁ = 8.1 • 10^-4 cm^-1 (region with defect) and α =3.9⋅10⁻⁴ cm^-1 (non-defected region). Optical scattering coefficient is determined as the difference between optical absorption coefficients measured for opaque and transparent lateral facets of the crystal respectively. Measurements reveal that scattering coefficient of LBO in the region with defect is three times higher than the optical absorption coefficient.

Even non-chiral objects can exhibit effective optical chiral response due to particular symmetry breaking of the investigating light and the sample morphology. Here we show linear and nonlinear optical measurements performed on a metasurface composed by self-assembled tilted golden nanowires on silicon substrate. The measurements are performed in three different schemes: optical reflectance, photoacoustic absorbance and second harmonic generation. In all these schemes circular polarized light was used in order to evidence the optical chiral behavior in different reciprocal disposition of the wires and light direction. The circular dichroism results to be present in all schemes when the three directions formed by i) the wires orientation, ii) the impinging light wave vector and iii) the normal to the metasurface forms a non-planar triad. Indeed non-planar triad of vectors represents a system that cannot be superposed to its mirror image, thus it is chiral system. We measured a sample obtained by vacuum evaporation of gold at glancing angle on a silicon substrate maintained at the temperature of 300K. The gold nanowires form a forest homogeneously distributed on 1 square inch substrate. Even if the chirality was detected both in linear and nonlinear optical measurements, the second harmonic generation process results to be more sensitive.