Semiconductor Lasers and Laser Dynamics XI

Photonic approaches emulating the powerful computational capabilities of the brain are receiving increasing research interest for radically new paradigms in ultrafast neuromorphic (brain-like) information processing and Artificial Intelligence (AI). This talk will report our research on light-enabled neuromorphic systems built with artificial photonic spiking neurons and photonic spiking neural networks (SNN). We will review the properties and performance of the photonic devices employed for the implementation of optical spiking neurons, including semiconductor lasers (e.g. Vertical Cavity Surface Emitting Lasers) and resonant tunnelling diodes. We will also discuss the strategies for their network-connectivity into photonic SNN architectures, and the techniques and algorithms realised for their use in complex functional information processing tasks (e.g. pattern recognition, image processing, data classification). We will also showcase the potentials of these spike-based photonic processing systems for ultrafast, low-energy and high-accuracy performance, with a hardware-friendly implementation that benefits from spike-based learning protocols with highly-reduced complexity.

We explored how linking a semiconductor laser to two mirrors can lead to unpredictable laser behavior, which has exciting applications like improving security in communications and generating random numbers. By precisely adjusting the mirrors, we can control the laser's stability and increase the unpredictability of its output. Based on simulations and experiments, we show that even small shifts in the mirror position can significantly influence the laser's performance. These insights challenge previous beliefs based on simpler setups and could pave the way towards further advances in laser technologies.

In our research, we systematically study the polarization-resolved nonlinear dynamics of a VCSEL under both continuous-wave (CW) optical injection (OI) and 3-line gain-switched (GS) optical frequency comb (OFC) injection, applied orthogonally to its parallel polarization. Our results show that the nonlinear dynamics induced by GS-OFC injection are determined by two factors: (1) the frequencies of the nonlinear dynamics of the VCSEL under CW OI and (2) the polarization switching curves for both types of OI. Both factors are essential in understanding the physics of the OFCs observed at the VCSEL output. Moreover, we provide guidelines on how to expand the width of the injected comb at the VCSEL's output demonstrating OFCs with approximately 50 GHz width.

We propose the use of Reservoir Computing (RC), a machine learning paradigm, to predict the temporal evolution of the complex dynamical behavior of semiconductor lasers under optical injection or feedback. Through numerical simulations, we illustrate two applications of RC: cross-predicting laser variables from intensity observations, reducing the need for continuous monitoring, and inferring laser dynamics for various optical feedback delay times based on data from a single delay. Our study suggests that a trained RC model can serve as a digital twin for semiconductor lasers, offering practical applications by minimizing experimental requirements and facilitating accurate predictions of their behavior.

We experimentally study the synchronization of chaos generated by semiconductor lasers in a cascade injection setup. Our setup able us to generate two different chaos, and the correlation coefficient rises to values above 90% for each. Furthermore, the effect of measurement bandwidth on the correlation value is studied.

Optical cavities with nonlinear elements and delayed self-coupling are widely explored candidates for photonic reservoir computing (RC). For time series prediction applications that appear in many real-world problems, energy efficiency, robustness and performance are key indicators. With this contribution I want to clarify the role of internal dynamic coupling and timescales on the performance of a photonic RC system and discuss routes for optimization. By numerically comparing various delay-based RC systems e.g., quantum-dot lasers, spin-VCSEL (vertically emitting semiconductor lasers), and semiconductor amplifiers regarding their performance on different time series prediction tasks, to messages are emphasized: First, a concise understanding of the nonlinear dynamic response (bifurcation structure) of the chosen dynamical system is necessary in order to use its full potential for RC and prevent operation with unsuitable parameters. Second, the input scheme (optical injection, current modulation etc.) crucially changes the outcome as it changes the direction of the perturbation and therewith the nonlinearity. The input can be further utilized to externally add a memory timescale that is needed for the chosen task and thus offers an easy tunability of RC systems.

Programmable photonic circuits manipulate the flow of light on a chip by electrically controlling a set of tunable analog gates connected by optical waveguides. Light is distributed and spatially rerouted to implement various linear functions by interfering signals along different paths. A general-purpose photonic processor can be built by integrating this flexible hardware in a technology stack comprising an electronic monitoring and controlling layer and a software layer for resource control and programming. This processor can leverage the unique properties of photonics in terms of ultra-high bandwidth, high-speed operation, and low power consumption while operating in a complementary and synergistic way with electronic processors. This talk will review the recent advances in the field and it will also delve into the potential application fields for this technology including, communications, 6G systems, interconnections, switching for data centers and computing.

Photonic-crystal waveguides have led to a new generation of integrated high-Q Kerr-nonlinear microresonators, in which linear and nonlinear dynamics can be strongly influenced and tailored. We discuss ultrashort pulse and frequency comb formation in such resonators, novel self- and sideband injection locking dynamics, as well as, methods for full phase-stabilization as needed for chip-based optical precision metrology.

We present the remarkable tunability of the output spectrum of an Optically Injected Semiconductor Laser under an input signal, in the form of a periodic pulse train, modulating the current. Conditions for discrete output spectra, in the form of frequency combs, are determined. The characteristics of the output frequency combs in terms of the number, the distance and the amplitude of the spectral lines, are shown to be controlled by the parameters of the input periodic pulse signal, namely the pulse amplitude, duration and period, suggesting a multi-functional device for a variety of applications.

A tunable optical comb source is presented via gain switching of a three-section photonic integrated circuit (PIC). The PIC consists of a two-section single mode laser referred to as the Primary Laser (PL) and a Fabry-Perot cavity laser referred to as the Secondary Laser (SL). The two lasers are mutually phase-locked via bidirectional coupling and can produce a coherent, single mode spectrum. Optical Frequency Combs (OFCs) are generated by gain switching the SL with a high-power radio frequency signal. Depending on the frequency of the gain switching, the output can vary greatly. Non-linear dynamical regimes including multi comb output, harmonic comb output and chaos are observed. A multi-mode model consisting of a bimodal PL bidirectionally coupled to a bimodal SL reproduces the experimental results extremely well.

We propose and demonstrate a new type of cascaded injection scheme of semiconductor lasers to generate optical frequency comb (OFC) signals. A typically Period-one (P1) dynamics are generated in the first stage injection system. With proper injection power adjusted in the second stage, the relaxation oscillations of the semiconductor laser become undamped, and subharmonic oscillations appear. The frequency spacing of the subharmonic oscillation is half of the first stage P1 dynamics, thus causing OFC generation. The OFC signal exhibits at least 15 comb lines with 10 GHz frequency spacing and bandwidth greater than 140 GHz.

Broad-area edge-emitting semiconductor lasers are well known for their spatio-temporal instabilities caused by the interaction of multiple transverse modes. We perform high-resolution spatio-spectral measurements using heterodyning of a 50 µm wide broad-area laser to obtain the mode profiles and linewidths of all transverse modes. First, we find that the profiles of certain transverse modes depend significantly on the pump current, which we attribute to carrier-induced index changes and thermal lensing effects. Second, we observe the formation of multiplets of 1st and 2nd order transverse modes which generate a narrow RF beat note. Since the linewidths of the involved modes are much larger than that of the beat note, we conclude that these transverse modes are phase locked. The analysis of the phase fluctuations of the heterodyning time traces confirms the observation of spontaneous phase-locking of transverse modes in a broad-area laser.

Nanolasers offer substantial promise for various applications due to their high efficiency, compact size, and low energy consumption. While their dynamical properties could further broaden their application scope, the current limitation of low photon flux hinders in-depth studies. Micro-VCSELs emerge as an ideal platform for comparing statistical and dynamical indicators, providing a comprehensive understanding of the physics and applications at the nanoscale. Remarkably, the reduction in laser size introduces heightened noise in the temporal signal evolution, paradoxically resulting in enhanced stability. This interplay between noise and stability yields novel dynamical behavior, expanding the parameter space to encompass the "below-threshold" region, reduced field coherence at equivalent pump levels, and potentially superior performance in data transmission. A statistical characterization of the photon number distribution near the laser threshold offers a nuanced perspective compared to macroscopic devices, while polarization bistability offers insights into coherence exchange between emission branches.

Exceptional points (EPs) are spectral singularities at which two or more eigenvalues of a non-Hermitian operator (often Hamiltonians), together with their corresponding eigenvectors, coalesce. Systems operating at or near EPs can give rise to many unique phenomena, such as self-termination of laser and unidirectional invisibility. However, in the aforementioned works, EPs are accessed below the lasing threshold, and therefore are of linear nature. In this work, we experimentally locate and track the EPs above the lasing threshold in coupled semiconductor photonic crystal nanocavities featuring gain/loss components. These EPs are inherently nonlinear, i.e. they are bifurcation points of a nonlinear dynamical system.

In anisotropic spin-lasers, the ultrafast dynamics of a coupled system between carrier and photon spins will be exploited to realize spin and polarization modulation at frequencies above 200 GHz, far beyond the current limits for conventional current-modulated laser devices. This makes spin-VCSELs excellent candidates not only for the next generation of ultrafast optical communication systems, but also for many other emerging applications such as polarization-based optical communication, neuromorphic computing, chaos-based random bit generation, or microwave and THz generation. Here we present our recent developments on ultrafast spin and polarization control in anisotropic spin-lasers and discuss the prospects and challenges of this new technology on its way to application.

This study introduces a comprehensive model for a single-mode nanolaser, incorporating two-particle quantum correlations. Contrary to semi-classical predictions, our results reveal that the onset of lasing necessitates finite amplitude fluctuations in stimulated emission. Coexisting lasing and non-lasing regimes appear, consistently with the quantization of light. The laser solution exhibits a central frequency, determined by a universal formula, and a finite linewidth, offering experimentally verifiable insights into the emission process. Electron-electron correlations, inducing collective effects like superradiance, elevate the stimulated emission threshold, mitigated by weak phonon scattering. As intracavity emitters increase, our quantum model converges to its semiclassical counterpart, except in a laser threshold nighbourhood. Additionally, we identify a bistability region influenced by two-particle quantum correlations, emphasizing compatibility with light quantization and revealing non-classical bistability in systems deviating from the semiclassical limit.

GeSn alloys hold the promise for on-chip, scalable industry-compatible light sources. In this paper, we introduce a novel strain engineering approach to create tensile-strained GeSn microlasers. By controlling the amount of strain, multiple lasers with different emission wavelengths were achieved on a single chip. This work offers a simple, cost-effective solution for diverse on-chip laser arrays, enabling applications extending to on-chip wavelength division multiplexing.

This study proposes integrating a MoS2–insulator-metal (MIM) structure with a ZnO nanowire to enhance surface plasmon polaritons (SPP). Notably, this improvement occurs at room temperature, significantly impacting plasmonic nanolaser performance. Compared to similar nanolaser systems on aluminum substrates, our approach reduces the threshold by 30%, shifting the ZnO gain medium from milliwatts (mW) to microwatts (uW).

The compactization of lasers is an ongoing challenge in increasing their effectiveness and integrability of other systems, from nanosatellites to medical devices. The need to decrease their dimensions, especially, for diode-pumped solid-state microchip laser systems causes significant problems with beam quality. Such lasers feature an additional problem of Brightness to output power scaling power. We report an approach where we used a thin film dielectric Fano-like resonance structure as a replacement to a conventional output coupler to overcome this challenge. The structure is engineered to function as a flat spatial filter element for selecting the fundamental transverse mode of the cavity. We achieved an increase of 2x over a conventional setup in CW operation. The data matches well with the numerical analysis performed for a single longitudinal mode model. We predict that this discovery could lead to advanced power scaling in submillimeter cavities, while maintaining the beam quality.

This work presents photonic integrated multi-channel transmitters for free-space optical communication systems applications. The circuits were designed and fabricated using the generic indium phosphide technology, which offers integration of passive and active elements and light amplification within the classical telecom C and L bands. The transmitters comprise an array of DBR laser light sources connected to electro-absorption modulators and an arrayed waveguide grating used as a wavelength multiplexer. The validity of the applied solution was investigated and confirmed with high-speed transmission experiments, including BER and eye diagram measurements of one and two-channel operations. The performance of the transmitters has been verified in the back-to-back configuration, and the first tests of free-space optical transmission have also been performed. The obtained results confirm the applicability of integrated transmitters in novel FSOC systems.

The realization of electrically pumped semiconductor lasers through solution methods not only holds significant importance for various applications, but it also remains a scientific challenge. Metal halide perovskites possess advantages of both organic and inorganic semiconductor materials, such as the ability for low-temperature solution preparation, high luminescence efficiency, large absorption coefficient, and high carrier mobility, offering the potential to achieve electrically pumped laser diodes. High-efficiency electroluminescence and continuous-wave optical-pumping lasing are prerequisites for realizing electrically pumped semiconductor lasers. The presenter will introduce his recent research advancements from these two aspects, and discuss the feasibility of achieving electrically pumped perovskite lasers.

We analyze the nonlinear response of an on-chip multi-wavelength laser (MWL) subject to optical injection with single-sideband modulation. We report the asymmetric power evolution of the sidebands while the modulation frequency is swept. The power and bandwidth of the signal emerging around the injected and un-injected modes strongly depend on the cavity resonance frequency of the injected mode, which can be tailored by twerking the injection strength and the detuning of the injected signal. We obtained an excellent agreement between numerical models based on the rate equations and experimental results thus highlighting the influence of key injection and laser parameters.

Heterogeneous integration of III-V semiconductor material on a Silicon substrate presented a promising solution to the challenge of laser integration in Silicon photonics. This will greatly benefit sensitive applications such as Analog Radio over Fiber (ARoF) in achieving a low-cost, highly integrated, and limited noise architecture. Meanwhile, careful laser design and characterization are essential to allow for high power emission, wide tunable operation, and the reduction of Relative Intensity Noise (RIN) which are vital to the performance of the ARoF through enhancing the signal-to-noise ratio and dynamic range. This paper presents two designs of a ring-resonator-based widely tunable laser, all designed by the III-V Lab and fabricated at the CEA-Leti, with differences in their vernier filter and Sagnac mirrors configuration. These laser chips have been characterized and compared through their output power, wavelength tunability evaluation, and RIN under different bias conditions. The presented results show a threshold current≤40 mA, a large wavelength tunable range of up to 48 nm, and a low RIN of up to −150 dB/Hz

Leading-edge machine learning algorithms require large amounts of matrix multiplications, which absorb significant computational resources in modern digital electronic systems. Analogue optical computing systems consisting of light sources, modulators and receivers may perform these operations with much higher efficiency. We introduce an integrated device based on electro-optically modulated (EOM) vertical-cavity surface-emitting lasers (VCSELs) that can perform analog multiplication at >28 GHz and at <20 mW power consumption. Due to its monolithic integration, the EOM VCSEL may be used as a building block for integrated optical computing devices. Development of such devices can help create 3-dimensionally integrated computing and communication systems.

This article presents an exploration, both experimentally and theoretically, of the dynamic behavior of a heterogeneously integrated III-V-on-SOI distributed feedback (DFB) quantum well laser (QWL). We investigate the complex interactions emerging when the laser is simultaneously subjected to optoelectronic and optical feedback. Our analysis focuses on the combined effects of these dual feedback mechanisms, with particular emphasis on frequency response and laser stability. Using the Lang-Kobayashi model, our simulations illustrate improved stability in laser operation and diverse dynamic transformations in response to dual feedback, providing essential benefits for the reliability of neuromorphic systems.

We numerically study the dynamics of VCSEL-SA when modulated by an analog on-off keying (OOK) current. It is found that the laser gives a pulse-like response when operated below the threshold current. After the threshold current, which is in the excitable phase, the laser generates single spikes (phasic spiking) and a series of spikes (tonic spiking) wherein the amplitude of the spikes varies as the form of the current. Complex dynamics such as bursting oscillations and chaotic dynamics are successfully generated at low frequencies (few MHz). After this excitable phase, the laser copies the OOK current with underdamped oscillations generated during the OFF phase of the OOK current.

We numerically investigate the dynamics of Vertical-Cavity Surface-Emitting Lasers (VCSELs) described by the current-dependent gain model and subjected to current in the form of amplitude modulation (AM) and frequency modulation (FM). Since VCSELs have two polarization modes (PMs), the competition between them offers more complex dynamical behaviors. It is found that when operating close to the threshold current, the laser converts the AM and FM currents into a series of pulse packages (PPs) that are globally irregular and modulated either in amplitude or frequency. In the particular case of FM current, both modulations occur in a unique signal. Besides, chaotic light is recovered even at low frequencies (few MHz) where it is not usually expected when sinusoidal current modulation is used. But, if the AM and the FM currents evolve over the threshold value, the laser does not alter the form of the current. Therefore, those currents are linearly converted into light signals.

Resonance modes are important component of an optical resonator. Linewidths of these modes and the energy confinement ability of a resonator is determined by its Quality factor. Intensity distributions inside a Fabry-Pérot (FP) resonator with broadband mirrors and also with periodic grating can be expressed as sum of its mode profiles. Here, we investigate the mode profiles and the intensity distributions of a FP resonator with partially and completely random Bragg grating on either sides and compare them. Randomness of the feedback gratings is considered to have uniform distribution and varied over several orders of magnitude. In both partially and completely random grating based FP resonators, we observe that the shape and linewidth of the resonance modes, as well as the Airy distributions change significantly compared to that of a FP resonator with perfectly periodic grating mirrors. However, interestingly, the relation between the mode profiles and the intensity distributions remains unaltered.

To develop a simple and inexpensive laser technique to remotely measure the concentration of nitrogen dioxide (NO2) gas concentration in ambient air, a single-mode external cavity diode laser (ECDL) emitting in the blue spectral region is developed. The ECDL, which uses a low-power Fabry-Perot laser diode, is designed in the Littrow configuration using a reflective holographic grating. The developed ECDL has a narrowband emission at 448 nm of 0.01 nm that coincides with a strong absorption cross-section of NO2 gas molecule, tuning ranges of 4.0 nm just above the threshold and 0.2 nm at high injection current. A maximum output power of 60 mW are achieved under the optimal operating conditions of the Fabry-Perot laser diode. The output emission power obtained corresponds to an efficiency of 80 % with respect to the Fabry-Perot laser diode in free-running condition. High stability of the laser system over many hours was also achieved with a fluctuation of less than 1 %.

The width of a laser line may be reduced by increasing the length of a laser cavity with the help of an extended cavity (optical feedback), or also by transferring the purity from another laser (master laser) through the process of frequency-locking brought by optical injection. In this presentation, using a Hz-linewidth master laser, we reduce the linewidth a DFB laser by around 70 dB of magnitude (depending on the operating pump rate). The result is obtained for a null detuning (or a null frequency difference between the master and the slave). We show that the optically-injected laser is indeed operating as a laser and not an optical amplifier by studying the frequency-locking threshold with respect to the injected optical power. This result is not in contradiction with the Schawlow-Townes limit, which is obtained for an internal source, the spontaneous emission, which is coupled to the stimulated emission, while in this case, the seeding photons for the laser process are coming from the external master source. However, these results clearly show that a laser can operate well below its Schawlow-Townes limit.

Low-noise lasers are critical in precision spectroscopy, displacement measurements, and optical atomic clock development. These fields require lasers with minimal frequency noise, combining cost-effectiveness with robust design. We introduce a simple, single-frequency laser that uses a ring fiber cavity for self-injection locking in a standard semiconductor distributed feedback (DFB) laser. Our design, unique in its use of polarization-maintaining (PM) single-mode optical fiber components, offers a maintenance-free operation and enhanced stability against environmental noise. Achieving continuous wave (CW) single-frequency operation, it maintains this state with low-bandwidth active optoelectronic feedback. The laser operates at ~8 mW, reducing the Lorentzian linewidth to ~75 Hz and achieving phase and intensity noise levels below –120 dBc/Hz and –140 dBc/Hz, respectively. Additionally, its thermal stabilization limits frequency drift to < 0.5 MHz/min with a maximum deviation of < 8 MHz. Implementing this design in integrated photonics could significantly cut costs and space requirements in high-capacity fiber networks, data centers, atomic clocks, and microwave photonics.

Photoinduced phase segregation and low coupling efficiency between QDs and cavities make is challenging to achieve stable blue cavity-enhanced superfluorescence in halide-doped perovskite QD system. Here, long-range-ordered CsPbBr2Cl QD superlattices are developed, in which the two core issues can be appropriately addressed. Based on the CsPbBr2Cl QD superlattices with regularly geometrical structures, stable and ultrafast blue cavity-enhanced superfluorescence was realized.

We develop a high-precision chaos lidar system using broadband optical chaos from a semiconductor laser subjected to optical feedback. We study how the detector bandwidths, cut-off frequencies, signal-to-noise ratios, and peak sidelobe levels in correlation affect the precision in ranging. With a detector bandwidth of 1600 MHz, a precision of 0.43 mm is achieved from the chaos-modulated pulses with a pulsewidth of 70 ns. The demonstration and comparison of 3D imaging obtained by waveforms with bandwidths of 1600 and 400 MHz show an enhancement in image quality with broader bandwidths.

This study explores the paradoxical relationship between noise, device size, and performance in Vertical Cavity Surface Emitting Lasers (VCSELs). Despite smaller VCSELs exhibiting heightened intrinsic noise and an unclear threshold current, they surprisingly demonstrate advantages such as increased robustness, rapid response times, energy-efficient pulse generation, and novel sensing applications. Employing fully stochastic simulations for varying β values, we find that smaller devices are less affected by noise, despite their intrinsic photon fluctuations. A detailed explanation, rooted in the dynamical response relative to β, unveils this paradox. Statistical analyses of overshoot peak distribution and delay time, relative to pump levels, offer insights into the interplay between noise, size, and performance in VCSELs.

Group IV materials suffers from a lack of efficient light generation for the on-chip integration of active photonic component on silicon (Si). One of the solutions is to use new material like Germanium-tin alloys (GeSn) that can provide direct band gap alignment of the band structure. The use quantum well (QW) is known, in principle, to favor room temperature laser operation at reasonable thresholds over bulk material. While most of advances were performed with bulk materials, exploring adequate designs of GeSn/SiGeSn based QW including strain engineering should be helpful for futures developments of Si-based active photonic devices. Here we demonstrate up to 290 K laser operation in GeSn/GeSn multi-QW microdisks cavities under optical pumping. The QW and barrier were performed by varying the Sn content. We used specific layer transfer technology and a Silicon Nitride (SiN) stressor layer was introduced to inject tensile strain in the active region such to enhance the directness of the transition. Interestingly this is the highest temperature of operation for GeSn quantum wells lasers. This progress opens the route towards room temperature electrically pumped laser operating.

Advancements in semiconductor materials, particularly within Group IV, are crucial to meet the demand for efficient and adaptable laser sources. Germanium-tin (GeSn) alloys have emerged as promising candidates, facilitating full monolithic integration into silicon photonics. Progress in optically pumped GeSn lasers is remarkable, but electrically injected ones face challenges due to low index contrast to effectively confine the optical mode. We propose an electrically pumped laser design based on GeSnOI (GeSn On Insulator) scheme. Modal analysis was performed at 2500 nm wavelength using finite element method, optimizing electromagnetic wave confinement, and mitigating direct electrical contact deposition on the active zone. Simulation results indicated that the most effective fabrication approach involves bonding with another silicon substrate using SiN dielectric layer as cladding, thus taking advantage of high optical index contrast. This advancement heralds the potential for room temperature operation of electrically pumped lasers.

3D laser nanoprinting based on multi-photon absorption (or multi-step absorption) has become an established commercially available and widespread technology. Here, we focus on recent progress concerning increasing print speed, improving the accessible spatial resolution beyond the diffraction limit, increasing the palette of available materials, and reducing instrument cost.

Biological discovery is a driving force of biomedical progress. With rapidly advancing technology to collect and analyze information from cells and tissues, we generate biomedical knowledge at rates never before attainable to science. Nevertheless, conversion of this knowledge to patient benefits remains a slow process. To accelerate the process of reaching solutions for healthcare, it would be important to complement this culture of discovery with a culture of problem-solving in healthcare. The talk focuses on recent progress with optical and optoacoustic technologies, as well as computational methods, which open new paths for solutions in biology and medicine. Particular attention is given on the use of these technologies for early detection and monitoring of disease evolution. The talk further shows new classes of imaging systems and sensors for assessing biochemical and pathophysiological parameters of systemic diseases, complement knowledge from –omic analytics and drive integrated solutions for improving healthcare.

Recently , quantum cascade laser proved to be an extremely interesting platform for frequency combs both in Mid-IR and THz frequency ranges. We will discuss some peculiar aspects of these devices arising from the combination of ultrafast gain, circular cavities and strong RF modulation. Despite the ultrafast nature of the gain medium, by properly engineering dispersion we demonstrate dissipative Kerr solitons both in Mid-IR and THz , with pulse durations of 3.7 ps in the Mid-IR and 10 ps in the THz. Then, by RF modulating a circular cavity, we demonstrate a quantum walk comb in synthetic frequency space. The initially ballistic quantum walk does not dissipate into low supermode states of the synthetic lattice; instead, the state stabilizes in a broad frequency comb, unlocking the full potential of the synthetic frequency lattice. Combs as broad as 100 cm-1 in the Mid-IR with flat top profile are reported.

We present a study of high-power quantum-cascade lasers (QCL) for 8 μm spectral range with active regions of lattice-matched to InP substrate and strain-balanced designs. The use of the strained quantum well/barrier pairs made it possible to increase the energy barrier between the upper laser level and continuum by ~ 200 meV. Our experiments show that utilization of the strain-balanced design of the active region makes it possible to more than double the threshold characteristic temperature T0 to 253 K from 125 K for the lattice-matched design. In pulsed mode, QCLs with strain-balanced active region demonstrated high efficiency of 12% and high output optical power of 21 W (over 10 W per facet). This is the highest value of the optical power demonstrated to date in 8 μm spectral region to the best of our knowledge.

Often described as the quantum mechanical counterpart to the classical random walk, the quantum walk is characterized by a ballistic spread of the spatial particle probability distribution, with fundamental implications as well as practical relevance, e.g., for quantum algorithms. Recently, it has been shown that optical frequency combs can mimic the behavior of a quantum walk. This “quantum walk comb” is induced by the injection of a radio frequency (RF) signal into a ring-shaped, mid-infrared quantum cascade laser (QCL). Here, we report on a compact and accurate extension to the Maxwell-Bloch formalism to model RF injection into ring QCLs, including the dependence of the electronic system Hamiltonian on the RF bias field which co-propagates with the optical waveform. We present dynamical simulations of the quantum walk comb in good agreement with experiment, reproducing key features such as the ballistic buildup of the comb and the resulting Bessel-like spectra.

We present a study of quantum cascade laser dynamical properties accounting for the Joule heating releasing in the active region. In particular we study the QCL emitting at 8 µm in the pulsed pumping mode, and present the experimental measurements and theoretical description of the QCL build-up time, showing the features appearing due to the different pump pulse rise time. Recent advances in quantum cascade laser (QCL) studies established this technology as the most promising for creating mid-IR sources needed for such applications as gas-sensing, medical spectroscopy, wireless communications and many others. As shown in [1] the thermal properties of QCL significantly affect its performance that manifests itself in the degradation of the lasing emission and the threshold current growth. At the same time, QCL dynamics is also affected. In particular, one can find it considering the non-monotonous behaviour of the build-up time. In this work we provide the analytical description of the build-up time behavior for the QCL under pump pulse close to the experimentally observed. We show that non-monotonous build-up time/current dependence is a direct consequence of the QCL Joule heating, and compare our analytical result with numerical solution of rate equations [2], revealing the main differences between the conventional approach and our analytical model. Apart from that our approach explains the possible appearing of the “negative” build-up time, which arises in the numerical solution without any motivation. Finally, we provide the experimental measurements of the build-up time in the QCLs emitting in the 8 µm region and compare the result with the provided theoretical analysis. The work is supported by the Russian Science Foundation (project 21-72-30020) [1] Vrubel, Ivan I., et al. "Active Region Overheating in Pulsed Quantum Cascade Lasers: Effects of Nonequilibrium Heat Dissipation on Laser Performance." Nanomaterials 13.23 (2023): 2994. [2] Cherotchenko, E. D., et al. "Observation of long turn-on delay in pulsed quantum cascade lasers." Journal of Lightwave Technology 40.7 (2021): 2104-2110.

Semiconductor lasers have become the light source of choice in many applications. IR VCSELs are widely used for sensing purposes in consumer electronics. On the other hand, longer wavelength i.e. SWIR are appearing and expected to rise. We introduce complete measurement setup for LIV with spectrum analysis of SWIR semiconductor lasers. Hereby InGaAs sensors with appropriate optics and electronics are combined. Our measurement set up benefits from a high-resolution array spectroradiometer, highly reflective integrating sphere and sensitive photodiode sensor. Further, the measurement setup is Metrologically calibrated and is traceable to the international standards. The influence of the temperature on the laser performance, characteristics and properties is thoroughly analyzed. Extension and further automisation of our measurement routine is required to facilitate the semiconductor lasers development and as well to speed up the industrialization of the semiconductor lasers.

In this contribution we will report on the realization of a single frequency, high-power 2.0 μm VECSEL laser for a specific quantum frequency conversion process and the development of the locking scheme using an optical frequency comb for the wavelength stabilization. We were able to reach a single frequency output power of 2.3 W in CW-operation at 2062 nm with a long-time absolute wavelength stability in the MHz range.

Low-loss coupling of VCSELs (vertical-cavity surface-emitting lasers) to optical fibres is a key issue for increasing their use in optical communications and instrumentation systems. However, tolerances on angular tilts and lateral misalignments are tight, particularly in the case of single mode devices. To address this challenge, a new fabrication method based on NIR single-mode self-writing (NIR-SM-SWW) of a polymer waveguide was developed and tested for the coupling of two single mode fibers at 850 nm (Thorlabs 780-HP) with a mode field diameter close to that of 850 nm single mode VCSEL. The specificity of our method is to use a writing wavelength identical to that designed for single mode propagation in the fibers, leading to a single step photopolymerization process that will be directly transferable to 850 nm VCSEL-to-fiber coupling. First results show coupling losses at 850 nm as low as 0.86 dB for a distance between the fibers of 100 µm.

We demonstrate two highly coherent tunable high power laser concepts, based on a III-V semiconductor VECSEL technology, operating in the 1µm wavelength range. We report experimentally and theoretically the existence of deterministic dynamics of a coherent semiconductor laser field, with a route to robust single-frequency operation exhibiting broad non-linear frequency pulling far above the thermally-assisted conventional tuning range. Thanks to a complementary design, we demonstrate an inhibited laser state exhibiting high power, high spatial and temporal coherence under ultralow light matter interaction, overcoming fundamental and technical limitations of common on the shelf laser technology, like quantum, electronic and thermal noise, as well as thermal lensing induced wave aberrations.

Spot size is an important parameter of the laser, which not only represents the resolution of laser, but is also involved in the calculation of other parameters. Nowadays, CCD imaging systems, scanning imaging systems, and other sensors are used to measure the laser spot size. But they are all lacking flexibility when measuring the spot size in different locations, not to mention their high cost. In this study, a new spot size measurement device based on laser back-injection interferometry was presented. The photodiode integrated with the laser diode was used to collect the feedback laser, then the laser spot size was calculated by the feedback current. A commercial CCD imaging system was used to provide the laser spot size as a reference. Results show that our spot size measurement device could measure the spot size (FWHM) of 5 laser diode modules both in the x (Gaussian-like profile) and y (top-hat-like profile) direction through scanning-slit. Though there are variations between the scanning-slit results and spot sizes from the CCD imaging system due to the diffuse and specular reflection, the accuracy of the spot size measurement device is ranging from 96.07 % to 99.46 %.

In this work, we explore the relationship between controlled application of mechanical strain and precise wavelength tuning of 1550nm VCSEL chips, demonstrating a 1nm tuning range. By using a four-point bending module we induce changes in refractive indices along the crystallographic axes through the elasto-optic effect, we thus unveil the influence of strain on VCSEL wavelength showing a linear correlation between strain and wavelength change. Our findings offer a comprehensive model to predict fabrication-induced wavelength shifts during VCSEL manufacturing as well as an innovative technique for precise wavelength tuning in optical communication while maintaining a consistent output power. These findings hold wide-reaching implications, bridging the gap between strain-induced wavelength control and different optical applications.

With simulations relying on a rate equations model, we clarify wavelength switching in feedback phase-controlled multi-wavelength semiconductor lasers. In particular, we identify how the differential gain and the coupling between the modes affect their controllability and capability of simultaneous emission. Additionally, we explore the optical feedback-related parameters space to delimit regions leading to wavelength control, simultaneous emission, or dynamics. Therefore, our work contributes to defining requirements for the operation of feedback phase-controlled multi-wavelength lasers, that are relevant for applications ranging from THz generation and processing to all-optical wavelength conversion.

Chaotic dynamics in semiconductor lasers under feedback is useful for ranging, security, reinforcement learning, and random bit generation. Complementing temporal characterizations, geometric characterization is realized using the correlation dimension D2. Numerically, a coherent combination of injection and feedback on a laser is considered in showing dimensional enhancement that qualitatively agrees with recent experiments. Experimentally, measurements of the dimensions continue to show enhancement in complexity by coherently incorporating injection and feedback without fixing the phase. The measurements are enabled by employing a large data size, while re-embedding through including a principal component analysis (PCA) is considered. Also, balanced homodyning with a delay is considered on a laser under injection alone, where the estimated dimension is found to nearly double as the baseband is strengthened. Based on single-mode laser dynamics, the coherent approaches of continuous-wave injection, delayed feedback, and balanced homodyning are demonstrated for manipulating the chaotic complexity for applications.

We show that a III-V semiconductor vertical external-cavity surface-emitting laser (VECSEL) can be engineered to generate light with a customizable spatiotemporal structure. Temporal control is achieved through the emission of temporal localized structures (TLSs), a particular mode-locking regime that allows individual addressing of the pulses traveling back and forth in the cavity. The spatial profile control relies on a degenerate external cavity, and it is implemented due to an absorptive mask deposited onto the gain mirror that limits the positive net gain within two circular spots in the transverse section of the VECSEL. Our results are a proof of concept of a laser platform capable of handling light states of scalable spatio-temporal complexity.