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In this study, the research on the nonlinear dynamics of semiconductor quantum dot laser with two time-delayed optical feedbacks is numerically investigated. Results show that the nonlinear dynamics behaviors of the laser are very sensitive to the rich system parameters in which both feedback strength and bias current are easily controlled to significantly influence the nonlinear dynamics including the periodic state and chaotic state. By judiciously adjusting the bias current of the laser or the feedback strength in the external cavity, period one, period doubling, quasi-period, and chaos are achieved. The feedback level-related bifurcation diagrams are analyzed in detail while fixing another feedback level at a constant or varying the bias current. In addition, the translation variables of the 0–1 test method that are clearly bounded for regular behavior and exhibit the Brownian motion for irregular phenomenon are adopted to further evaluate the periodic state and the chaotic state. These results can give insight into the quantum dot laser–based applications in various optical technologies.

Optical connectivity, which has been widely deployed in today's datacenters and high-performance computing (HPC) systems, is a disruptive technological revolution to the IT industry in the new Millennium. In our journey to debut an Exascale supercomputer, a completely new computing concept, called memory-driven computing, was innovated recently. This new computing architecture brings challenges and opportunities for novel optical interconnect solutions. Here, we first discuss our strategy to develop appropriate optical link solutions for different data traffic scenarios in memory-driven HPCs. Then, we present detailed review on recent work to demonstrate fully photonics-electronics-integrated single- and multi-wavelength directly modulated laser (DML) transmitters on silicon for the first time. Compact heterogeneous microring lasers and laser arrays were fabricated as photonic engines to work with a customized complementary metal-oxide semiconductor (CMOS) driver circuit. Microring lasers based on conventional quantum well and new quantum dot lasing medium were compared in the experiment. Thermal shunt and MOS capacitor structures were integrated into the lasers for effective thermal management and ultra low-energy tuning. It enables a controllable dense wavelength division multiplexing (DWDM) link architecture in an HPC environment. An equivalent microring laser circuit model was constructed to allow photonics-electronics co-simulation. Equalization functionality in the CMOS driver circuit proved to be critical to achieve up to 14 Gb/s direct modulation with 6 dB extinction ratio. Finally, the on-going and future work is discussed towards more robust, higher speed, and more energy efficient DML transmitters.

Photonic integrated circuits (PICs) have enabled numerous high performance, energy efficient, and compact technologies for optical communications, sensing, and metrology. One of the biggest challenges in scaling PICs comes from the parasitic reflections that feed light back into the laser source. These reflections increase noise and may cause laser destabilization. To avoid parasitic reflections, expensive and bulky optical isolators have been placed between the laser and the rest of the PIC leading to large increases in device footprint for on-chip integration schemes and significant increases in packaging complexity and cost for lasers co-packaged with passive PICs. This review article reports new findings on epitaxial quantum dot lasers on silicon and studies both theoretically and experimentally the connection between the material properties and the ultra-low reflection sensitivity that is achieved. Our results show that such quantum dot lasers on silicon exhibit much lower linewidth enhancement factors than any quantum well lasers. Together with the large damping factor, we show that the quantum dot gain medium is fundamentally dependent on dot uniformity, but through careful optimization, even epitaxial lasers on silicon can operate without an optical isolator, which is of paramount importance for the future high-speed silicon photonic systems.

We measure the FM noise power spectral density of quantum-dot mode-locked lasers (QD-MLLs) and compare this to their measured linewidths as predictors of performance in a digital coherent system. We explain our observations in terms of the non-Lorentzian line shape of the source wherein linewidth is determined by the low frequency part of its FM noise. Investigation of system performance with simulations based on the measured phase sequences and back-to-back coherent transmission experiments show that QD-MLLs with linewidths of several megahertz can have comparable performance to that of a laser with only a few hundreds of kilohertz of Lorentzian linewidth, due to the non-white part of their FM noise. We show that spectral linewidths of lasers with similar spectral properties can underestimate their performance in coherent systems, regardless of the linewidth measurement technique used. We propose a “ Lorentzian-equivalent linewidth ” measure to characterize lasers with non-white FM noise and to estimate their impact in digital coherent optical systems. This measure is obtained from phase variations at frequencies higher than typical frequencies often used to characterize lasers with white FM noise and comparable to the system baud. The proposed measure is shown to be a better predictor of system performance than the measured linewidth, for lasers with non-white FM noise. The impact of non-white FM noise on the optimization of carrier phase recovery and system performance is also discussed.

This work investigates the degradation processes affecting the long-term reliability of 1.3 μm InAs quantum-dot lasers epitaxially grown on silicon. By submitting laser samples to constant-current stress, we were able to identify the physical mechanisms responsible for the optical degradation. More specifically, the samples (i) exhibited a gradual increase in threshold current, well correlated with (ii) a decrease in sub-threshold emission, and (iii) a decrease in slope efficiency. These variations were found to be compatible with a diffusion process involving the propagation of defects toward the active region of the device and the subsequent decrease in injection efficiency. This hypothesis was also supported by the increase in the defect-related current conduction components exhibited by the electrical characteristics, and highlights the role of defects in the gradual degradation of InAs quantum dot laser diodes. Electroluminescence measurements were used to provide further insight in the degradation process.

Dynamics of a multimode quantum dot laser with polarization-rotated optical feedback is investigated in a wide range of bias current. The results reveal that the laser is more sensitive to optical feedback when the polarization of feedback beam is rotated a large angle from the original polarization, which is different from the results in DFB lasers. Anticorrelated fluctuations between orthogonal polarizations are observed in a certain range of selected polarizations. Accordingly, dynamics in the total power can be weaker than that in a selected polarization. The anticorrelated polarization dynamics may be related to different polarizations of longitudinal modes.

This paper reviews optical injection locking (OIL) of semiconductor lasers and its application in optical communications and signal processing. Despite complex OIL dynamics, we attempt to explain the operational principle and main features of the OIL in an intuitive way, aiming at a wide understanding of the OIL phenomenon and its associated techniques in the optic and photonic communities. We review and compare different control techniques that enable robust OIL in practical systems. The applications are reviewed with a focus on new developments in the past decade, under the categories of ‘High Speed Directly Modulated Lasers’ and ‘Optical Carrier Recovery’. Finally, we draw our vision for future research directions.

We report high-performance broad-area eight-layer InAs/GaAs quantum-dot lasers (QDLs) emitting at 1.3 μm in the pulse and continuous-wave (CW) operations. Operational characteristics of the fabricated QDLs, including the emission wavelength, output power, threshold-current density, differential quantum efficiency, and characteristic temperature, are investigated at different temperatures. For as-cleaved facets of 100 μm wide and 1 mm cavity-length device, an output power of 100 mW is achieved at 1 kHz with 5% duty cycle and 49 mW in the CW operation. The device exhibits a threshold-current density of 56 A/cm2 at room temperature in both the operating modes and increases to 71 and 80 A/cm2 the in the pulse and CW modes, respectively, at 343 K. Over a temperature range of 298K to 343 K, we calculate the threshold characteristic temperature of 166K and 119K and slope-efficiency characteristic temperature of 2061K and 408K in the pulse and CW modes, respectively. The laser exhibits differential quantum efficiency of 41% and 32% in the pulse and CW mode, respectively. We observed that the device exhibited negligible dependence over a temperature range of 298K to 343 K.

$p$ -type modulation doping of the quantum dot active region is known to improve high temperature and dynamic performance of quantum dot lasers. These improvements are critical to realizing commercially relevant quantum dot devices on silicon and are shown to enable continuous wave operation over 100°C, nearly complete insensitivity to optical feedback, and orders of magnitude improvement in device reliability relative to unintentionally doped active regions. Also described is a spectrally resolved analysis of the effect of p-modulation doping on the optical gain revealing anomalous behavior that explains the high characteristic temperatures commonly observed in literature for similar devices on native substrate.

Owing to the excellent properties of perovskite quantum dots (QDs), such as an easy synthesis process, high photoluminescence quantum yields, high defect tolerance, and tunable bandgap with different elements, laser actions have been widely conducted. Over the past few years, several approaches have been used for successfully creating perovskite QD lasers. In this review, we summarize the progress of perovskite QD lasers from the aspects of laser theory, characteristics and applications of QD lasers, advantages of perovskite materials for lasers, factors influencing the QD laser threshold, two‐photon pumped QD lasers, and perovskite QD laser stability. At the same time, aiming at existing problems, possible solutions and prospects are presented.

A three-fold reduction of threshold current, with a minimum threshold current density of 286 A/cm 2 , a maximum operating temperature of 80 °C, and a maximum 3 dB bandwidth of 5.8 GHz was achieved for 1.3 μm InAs quantum dot lasers on patterned, on-axis (001) Si. This was enabled by the reduced threading dislocation density (from 7×10 7 to 3×10 6 cm −2 ), and optimized probe design. The patterned Si produced antiphase domain free material in the coalesced GaAs buffer layer with reduced misfit/threading dislocation nucleation, without the use of Ge/GaP buffers or substrate miscut. Utilizing aspect ratio trapping, cyclic thermal annealing, and dislocation filter layers, high quality III-V on Si devices were grown, demonstrating the compelling advantages of this patterned Si template for a monolithic Si photonics integration platform.

Free-running quantum cascade lasers (QCLs) show a natural tendency to operate in the multimode regime as a result of both spatial and spectral hole burning. While multimode operation by itself is far from unusual, what distinguishes QCLs from other lasers is that the phases of the individual modes in them can be locked in the absence of any additional intracavity elements, thus forming frequency combs (FCs) that have many practical applications. Unlike typical FCs produced in mode-locked lasers or microcavities, the temporal shape of a QCL FC is not a short pulse but rather a combination of frequency and (to a lesser extent) amplitude modulated signals, the origin of which is not obvious. In this paper, we develop a theory aimed at explicating the most recent experimental measurements of temporal characteristics of QCL FCs. We identify spatial hole burning as the root cause of frequency modulation and show that, in addition to previously analyzed rapid, pseudo-random frequency modulation, the experimentally observed long linearly chirped signal can also alleviate spatial hole burning efficiently. We find that in the absence of spectral hole burning, a linearly chirped regime has the lowest threshold. Furthermore, we show that for relatively weak frequency modulation, amplitude modulation should also arise as confirmed experimentally. The result of this paper is a first step toward reliably engineering FCs with specified characteristics in mid IR and THz regions.

The linewidth enhancement factor ( $\alpha _\mathrm{H}$ ) is an important parameter for semiconductor lasers. In this paper, we investigate, both theoretically and experimentally, the key parameters that affect $\alpha _\mathrm{H}$ of InAs/GaAs quantum dot lasers. Both dot uniformity and doping density are found to be critical in achieving small $\alpha _\mathrm{H}$ in quantum dot lasers. The prospects for quantum dot lasers in isolator-free and narrow linewidth applications are also discussed.

This paper investigates the intensity noise and pulse oscillation characteristics of an InAs/GaAs quantum dot laser epitaxially grown on germanium. We show that the relative intensity noise of the free-running laser generally decreases with increasing pump current, and the minimum value reaches down to about $-$ 126 dB/Hz. The intensity noise is hardly affected by the optical feedback, unless there is a resonance or pulse oscillation in the noise spectrum. The laser pumped at a high current is more sensitive to the optical feedback. Interestingly, it is found that the free-running Ge-based quantum dot laser generates self-sustained pulse oscillations with one period or two periods upon the pump current, without incorporating saturable absorbers. This behavior is valuable for both self-generation of photonic microwaves and for understanding nonlinear dynamics of semiconductor lasers.

Initial age-related degradation mechanisms for InAs quantum dot lasers grown on silicon substrates emitting at 1.3 μ m are investigated. The rate of degradation is observed to increase for devices operated at higher carrier densities and is therefore dependent on gain requirement or cavity length. While carrier localization in quantum dots minimizes degradation, an increase in the number of defects in the early stages of aging can increase the internal optical-loss that can initiate rapid degradation of laser performance due to the rise in threshold carrier density. Population of the two-dimensional states is considered the major factor for determining the rate of degradation, which can be significant for lasers requiring high threshold carrier densities. This is demonstrated by operating lasers of different cavity lengths with a constant current and measuring the change in threshold current at regular intervals. A segmented-contact device, which can be used to measure the modal absorption and also operate as a laser, is used to determine how the internal optical-loss changes in the early stages of degradation. Structures grown on silicon show an increase in internal optical loss, whereas the same structure grown on GaAs shows no signs of increase in internal optical loss when operated under the same conditions.

Dual-state emission is a common and important phenomenon which takes place in semiconductor Quantum Dot Lasers at different temperature and operating conditions usually investigated from microscopic carrier interaction modeling or even rate-equations based approaches. In this study, we revisit the topic, but the investigation is here performed from a system identification perspective; we built black-box models based on artificial neural networks approach, using the Multilayer Perceptron, the Extreme Learning Machine and a hybrid Echo State Network - Extreme Learning Machine. As a case study, we focused on switch-on transient and its prediction. The study revealed the model was able to separate and to predict, from the solely total power, without using any QDL design parameters, the optical power around the ground state and first excited state lasing lines of InAs/InGaAs quantum dot laser. The error performance was low as a RMSE of 2.81 μW and MAPE of 0.50% with processing time (training and testing time) of 15.27 s, enabling the alternative model to be used in optical filtering instrumentation as low-resolution and low-cost filters for applications in which it is not economically viable to use a spectrum analyzer, which can be replaced by a simple optical power meter.

Quantum dot (QD) laser as a light source for silicon optical integration has attracted great research attention because of the strategic vision of optical interconnection. In this paper, the communication band InAs QD ridge waveguide lasers were fabricated on GaAs-on-insulator (GaAsOI) substrate by combining ion-slicing technique and molecular beam epitaxy (MBE) growth. On the foundation of optimizing surface treatment processes, the InAs/In0.13Ga0.87As/GaAs dot-in-well (DWELL) lasers monolithically grown on a GaAsOI substrate were realized under pulsed operation at 20 °C. The static device measurements reveal comparable performance in terms of threshold current density, slope efficiency and output power between the QD lasers on GaAsOI and GaAs substrates. This work shows great potential to fabricate highly integrated light source on Si for photonic integrated circuits.

Funding: This paper incorporates results obtained from the project, JPNP20017, commissioned by 474 the New Energy and Industrial Technology Development Organization (NEDO) in Japan. Here, we report on the design and performance of a silicon photonic micro-transceiver required to operate in 5G and 6G environments at high ambient temperatures above 105 °C. The four-channel “IOCore” micro-transceiver incorporates a 1310 nm quantum dot laser system and operates at a data rate of 25 Gbps and higher. The 5 × 5 mm micro-transceiver chip benefits from a multimode coupling interface for low-cost assembly and robust connectivity at high temperatures as well as an optical redundancy scheme, which increases reliability by over an order of magnitude. Publisher PDF

A semi-empirical model is compared with measurements to establish limiting factors in the performance of p-modulation doped InAs quantum dot (QD) lasers. Fitted absorption spectra allow identification of supposed factors and comparison of multiple samples isolates their origin, providing insights for future laser design.

III-V semiconductor lasers integrated on Si-based photonic platforms are eagerly awaited by the industry for mass-scale applications, from interconnect to on-chip sensing. The current understanding is that only quantum dot lasers can reasonably operate at the high dislocation densities generated by the III-V-on-Si heteroepitaxy, which induces high non-radiative carrier recombination rates. Here we propose a strategy based on a type-II band alignment to fabricate quantum well lasers highly tolerant to dislocations. A mid-IR GaInSb/InAs interband cascade laser grown on Si exhibits performances similar to those of its counterpart grown on the native GaSb substrate, in spite of a dislocation density in the 10 8 c m − 2 range. Over 3800 h of continuous-wave operation data have been collected, giving an extrapolated mean time to failure exceeding 312,000 h. This validates the proposed strategy and opens the way to new integrated laser development.

The realization of monolithic integration of a stable III–V laser on a standard silicon-on-insulator (SOI) substrate has been regarded as a challenging technology for silicon-based photonic integration circuits (PICs). Here, we successfully demonstrated the electrically pumped P-doped 1300 nm InAs/GaAs quantum dot (QD) laser epitaxially grown on {111}-faceted SOI hollow substrates. These III–V QD lasers, which are epitaxially grown on an SOI substrate, generally exhibit strong thermal accumulation due to the oxide layer underneath. By applying a double-side heat dissipation design, the maximum operation temperature of the SOI-based InAs/GaAs QD laser under a continuous-wave (CW) operation mode is ramped up to 35°C from 20°C. Moreover, the thermal profile simulation of three different structures has also been carried out to show the effectiveness of the top heat sink design in order to improve laser performance. An integrated thermal shunt design is proposed to improve heat dissipation without using the external top heat sink. The successful realization of room-temperature SOI-based InAs/GaAs QD lasers pave a viable way for integrating light sources in PICs.

We review results on the optical injection of dual state InAs quantum dot-based semiconductor lasers. The two states in question are the so-called ground state and first excited state of the laser. This ability to lase from two different energy states is unique amongst semiconductor lasers and in combination with the high, intrinsic relaxation oscillation damping of the material and the novel, inherent cascade like carrier relaxation process, endows optically injected dual state quantum dot lasers with many unique dynamical properties. Particular attention is paid to fast state switching, antiphase excitability, novel information processing techniques and optothermally induced neuronal phenomena. We compare and contrast some of the physical properties of the system with other optically injected two state devices such as vertical cavity surface emitting lasers and ring lasers. Finally, we offer an outlook on the use of quantum dot material in photonic integrated circuits.

Based on the three-energy level exciton model of the quantum dot lasers (QDLs), the nonlinear dynamics of the sole ground-state emitting QDL (GS-QDL) under external optical injection is numerically studied. The results show that the GS-QDL can generate period-one, period-two, multi-period, chaotic pulse and injection locking states under suitable injection parameters. By analyzing the distribution of these dynamic states in the injection parameter space, it is found that the period-one state and injection locking state occupy a large area, but the region of the complex dynamics is relatively small. Moreover, the complexity of the chaotic signals generated by the GS-QDL is quantified by the permutation entropy calculation. The results show that the complexity of the chaotic signals is less than 0.90, which indicates that the GS-QDL is low sensitivity to external optical injection. The GS-QDL can be used in isolator-free photonic integrated circuits.

We propose a multilayer silicon nitride (SiN) -on-silicon photonic integrated circuit (PIC) platform with a monolithic laser at the C-band. A tapered edge coupler and a meta-structure-based interlayer directional coupler in the platform were designed to realize low-loss broadband laser-to-chip 3D coupling with small footprint. The coupling length of the interlayer directional coupler and the gap between different SiN layers were optimized as 12.7 µm and 1.4 µm. We measured the 1-dB-drop optical operation bandwidth of greater than 76 nm and the coupling loss of 6.1 ± 0.1 dB at 1550 nm for the interlayer directional coupler. The hybrid integration was demonstrated as a proof of concept for monolithic integration of light sources. The butt-coupling loss of 3.7 ± 0.1 dB between an on-chip DFB laser and a SiN edge coupler at 1549.48 nm was achieved. This approach opens the possibility of employing monolithic laser in the silicon photonics platform.

With exponential growth in data traffic and limitations of Moore’s Law, electronic integrated circuits have reached a bottleneck period. Photonic Integrated Circuits (PICs) are seemed as candidate for solving the problem of data transmission. Moreover, robust laser sources are significant building block for PICs design. Here, we demonstrate several InAs/GaAs quantum dot microcavity lasers monolithically grown on planar on-axis Si (001) substrates, including microdisk cavity [1], 2D Photonic Crystal with L3 defects cavity [2], 1D Photonic Crystal nanobeam cavity, bandedge Photonic Crystal cavity, bound states in the continuum (BIC) cavity, etc.

For the first time, RIN reduction in gain-switched quantum dot laser is demonstrated with an optical beam illumination to the excited state. It is also found that pulses having a width of 27–29 ps with a high peak power are generated under the noise.

Regrown quantum-dot distributed feedback lasers on Si demonstrate record performance, with a threshold current of 10 mA, an intrinsic linewidth of 41.2 kHz, a side-mode suppression ratio of 57.5 dB, and a maximum power of 11.7 mW.

InAs quantum dot lasers on silicon using misfit dislocation trapping layers show 400-fold improvement in lifetime at 80°C (failure criterion: 50% initial peak power). Trapped misfit segments show no evidence of recombination enhanced dislocation climb, leading to an order of magnitude reduction in its extent.

For the first time, with an optical beam illumination, gain-switched short pulses with a width of 25–40 ps with a high peak power are generated owing to excited state transitions, and the change in the laser parameters does not affect the output pulses strongly.

We demonstrate the superior emission properties of a red-emitting self-assembled quantum dot microsphere laser made from a blend of green and red bandgap CdS x Se 1-x / ZnS quantum dots. The addition of the higher bandgap material reduces self-absorption and improves the Q-factor.

International audience; How far can we go in shaping the luminescence of quantum emitters? It is well known that by using cavities or nano-antennas, one can beam their luminescence into well-controlled directions of space. Here, we push this control to a level of complexity usually achieved with laser radiation: we make an assembly of colloidal quantum dots spontaneously emit vector vortex beams, which are swirls of light combining a non-zero angular momentum and an inhomogeneous field structure. The key ingredient to obtain this result is to increase the spatial coherence of the emitted photons. To fulfill this condition, we design and use plasmonic holograms that also impart a non-zero orbital angular momentum and a radial polarization state to the beam.

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Direct epitaxy of InP quantum dot (QD) lasers on silicon (Si) provides an on-chip red laser source for integrated Si photonics with different applications. Here, we demonstrate the first, to the best of our knowledge, InP QD lasers directly grown on (001) Si. Combining highly emissive InP QDs and a GaAs/Si template with low defect density, continuous-wave (CW) lasing of micro-disk lasers (MDLs) on Si is achieved at room temperature. The lowest threshold of MDLs on Si is ∼ 500 n W , without considering the micro-disk surface absorption efficiency of the pump power. The MDLs grown on the native GaAs substrate with the same growth and fabrication process are compared using statistical data analysis. Similar material characterization results and device performances on these two substrates further confirm the performance of QD lasers on Si. This demonstration paves the way for future realization of integrated photonic circuits with red and near-infrared (NIR) lasers on Si.

Quantum dots (QDs) are a revolution in the field of photoelectric and have a crucial potential for future applications as a color converter in micro/mini- LEDs. However, the reported QD converter efficiency (-20-40%) has not reached the level on par with that of the conventional phosphor color converters (~40-60%). In this study, we fabricate the QD nanowires (NWs) templated in the nanoporous anodic aluminum oxide (AAO) substrate using a combination of inkjet printing and vacuum-deposition. Owing to the light couple and waveguide effect of the nanopores cavity structure, we demonstrate a 1.25-fold enhancement in the luminous flux and a 2.04-fold increase in the photoluminescence (PL) intensity compared with the traditional QD planar converter. Furthermore, the stability test showed a 2.34 times improvement in lifetime resulting from the heat dissipation and moisture protection of the nanopores. The inkjet printing fabrication strategy combined with the nanostructure provides new insights for mass-produce high-quality QD NWs, which is promising for modern lighting applications in the micro/mini-lighting-emitting diodes (LEDs).

Dual-state emission is an phenomenon which takes place in Quantum Dot Lasers at different temperature and operating conditions. In this study, we investigate that issue from a nonlinear regression model based on Extreme Learning Machine, which revealed to be able to predict the spectrally resolved transient response of InAs/InGaAs quantum dot laser with error performance as low as 0.54%.

For the first time gain-switched short pulse generation with a width of 25-40 ps from excited state is demonstrated applying an external optical Gaussian beam to the excited state of InAs-InP-(113)B quantum dot laser.

We discuss the integration of quantum dashes (QDashes) into laser simulations using Crosslight Pics3D, outlining the approach for developing a model featuring asymmetrical active regions. The importance of including wetting layers to accurately represent carrier transport is investigated using results obtained for an InAs/InP QDash laser. While leakage current across the active region is unaffected by the absence of wetting layers, their presence enhances Auger recombination losses in the active region, leading to lower overall device efficiencies.

InAlGaAs/GaAs quantum dots (QDs) are grown by molecular beam epitaxy and subsequently characterized to achieve emission $\lt 1\ \mu$m. Growth parameters are optimized to grow a new generation of homogeneous quaternary QDs with a PL FWHM of $\sim 60\ \mathrm{meV}$ and a surface density of $\gt10^{10} \mathrm{~cm}^{-2}$.

Quantum cascade lasers (QCLs) facilitate compact optical frequency comb sources that operate in the mid-infrared and terahertz spectral regions, where many molecules have their fundamental absorption lines. Enhancing the optical bandwidth of these chip-sized lasers is of paramount importance to address their application in broadband high-precision spectroscopy. In this work, we provide a numerical and experimental investigation of the comb spectral width and show how it can be optimized to obtain its maximum value defined by the laser gain bandwidth. The interplay of nonoptimal values of the resonant Kerr nonlinearity and cavity dispersion can lead to significant narrowing of the comb spectrum and reveals the best approach for dispersion compensation. The implementation of high mirror losses is shown to be favorable and results in proliferation of the comb sidemodes. Ultimately, injection locking of QCLs by modulating the laser bias around the round trip frequency provides a stable external knob to control the frequency-modulated comb state and recover the maximum spectral width of the unlocked laser state.

A modified rate equation model was presented to theoretically investigate the nonlinear dynamics of solitary two-state quantum dot lasers (TSQDLs) under optical feedback. The simulated results showed that, for a TSQDL biased at a relatively high current, the ground-state (GS) and excited-state (ES) lasing of the TSQDL can be stimulated simultaneously. After introducing optical feedback, both GS lasing and ES lasing can exhibit rich nonlinear dynamic states including steady state (S), period one (P1), period two (P2), multi-period (MP), and chaotic (C) state under different feedback strength and phase offset, respectively, and the dynamic states for the two lasing types are always identical. Furthermore, the influences of the linewidth enhancement factor (LEF) on the nonlinear dynamical state distribution of TSQDLs in the parameter space of feedback strength and phase offset were also analyzed. For a TSQDL with a larger LEF, much more dynamical states can be observed, and the parameter regions for two lasing types operating at chaotic state are widened after introducing optical feedback.

Inversion boundaries (IBs) are charged planer defects that arise from the growth of polar III-V materials on non-polar Si (001) substrate. This paper demonstrates a novel technique to achieve all-MBE grown, IB-free GaAs on on-axis Si (001) substrates by employing periodic Si single-atomic-height steps to re-distribute the nucleation of IBs and promote IB self-annihilation in the subsequent GaAs growth. Furthermore, an electronically pumped quantum-dot (QD) laser has been demonstrated on this IB-free GaAs/Si platform with a maximum operating temperature of 120 °C. These results could be a significant step towards the monolithic integration of III-V materials and devices with mature CMOS technology.

We propose and numerically demonstrate a photonic microwave generation scheme based on the dynamic period-one oscillation of a solitary spin-polarized vertical-cavity surface-emitting laser (spin-VCSEL). The evolution of the oscillation amplitude, frequency, power, and linewidth of the generated microwave is systematically investigated by using two-dimensional maps. The results show that the generated microwave signals with a dominant linewidth of about 3 MHz have a broad tunable frequency (from several gigahertz to hundreds of gigahertz), which benefits from the birefringence-induced oscillation in spin-VCSELs. Moreover, with the help of optical feedback, the microwave linewidth can be effectively minimized ( ∼ 51 k H z ) by increasing the feedback strength and feedback delay time. Importantly, this Letter offers prospects for applications requiring a feasible and resource-efficient microwave source in microwave photonic fields.

We semianalytically and numerically investigate the static and dynamical characteristics of quantum-dot (QD) lasers directly grown on silicon by considering the Shockley-Read-Hall (SRH) recombination. The static characteristics are studied through small-signal analysis, including the ${\ensuremath{\alpha}}_{H}$ factor, damping factor, and modulation dynamics. In addition, the feedback dynamics are analyzed through improved corpuscular rate equations based on the classical Lang-Kobayashi (LK) model with time series, bifurcation diagrams, and phase portraits. We find that a smaller ${\ensuremath{\alpha}}_{H}$ factor but larger damping factor are obtained by decreasing the nonradiative recombination lifetime. On top of that, in both the short- and long-external-cavity regimes, any decrease of the SRH recombination lifetime obliterates significantly chaotic regions and shifts the first Hopf bifurcation point to higher feedback values. Overall, this work provides insights into the understanding of QD laser physics, hence highlighting the influence of the SRH lifetime on the reflection sensitivity of epitaxial QD lasers on silicon. These results are qualitatively consistent with recent experiments and are therefore helpful for designing feedback-resistant lasers for future photonic integrated circuits operating without optical isolation.

We experimentally investigate the complex dynamics of a multi-mode quantum-dot semiconductor laser with time-delayed optical feedback. We examine a two-dimensional bifurcation diagram of the quantum-dot laser as a comprehensive dynamical map by changing the injection current and feedback strength. We found that the bifurcation diagram contains two different parameter regions of low-frequency fluctuations. The power-dropout dynamics of the low-frequency fluctuations are observed in the sub-GHz region, which is considerably faster than the conventional low-frequency fluctuations in the MHz region. Comparing the dynamics of quantum-dot laser with those of single- and multi-mode quantum-well semiconductor lasers reveals that the fast low-frequency fluctuation dynamics are unique characteristics of quantum-dot lasers with time-delayed optical feedback.

Spin-optoelectronics is a rapidly developing field with promises to provide extra functionalities in communication and spectroscopy via ultrafast polarization modulation [1] . We are addressing the question of spin memory in InAs/GaAs quantum dots (QD) which can serve as gain structures for vertical-external cavity lasers (VECSELs), whereas most previous investigations focused on monolithic VCSELs. VECSELs offer possibilities not only for power scaling but also for additional flexibility as polarization controlling elements can be introduced into the free space sections [2] , [3] . Moreover QDs extend the wavelength coverage of GaAs based materials to the 1300 nm telecomm band with long spin lifetimes having been reported [4] . However, previous investigations concentrated on low temperatures and/or charged/doped dots and we are not aware of results on structures at strong excitation for lasing at room temperature.