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This work investigates the dynamics of two-state quantum dot lasers through semi-analytically solving a set of rate equations. Simulations reveal that the occurrence of excited state lasing reduces the damping factor and relaxation oscillation frequency of the laser while increases the linewidth enhancement factor associated to the ground state transition. These results are in good agreement with the experimental observation showing that the quantum dot laser becomes more sensitive to external optical feedback at excited state lasing threshold. This work brings novel insights in the understanding of quantum dot laser physics that are useful for designing feedback resistant lasers in photonic integrated technologies.

A frequency-domain description of semiconductor mode-locked lasers is presented. The approach provides self-consistent accounting of locking mechanism, gain saturation, mode competition and carrier-induced refractive index, in addition to directly connecting mode-locking performance to the bandstructure.

Direct heteroepitaxy of compound semiconductors on silicon represents the most promising approach for realizing monolithic laser sources for silicon photonics. Record material quality and defect tolerant quantum dot lasers are reported.

Photonic integrated circuits enable energy efficient and compact technologies for modern information communications. Here, we explore semiconductor epitaxial quantum dots lasers on silicon and demonstrate their high suitability for addressing the important issues associated to photonic integration on silicon.

This work experimentally investigates the impact of p-doping on the relative intensity noise (RIN) properties and subsequently on the modulation properties of semiconductor quantum dot (QD) lasers epitaxially grown on silicon. Owing to the low threading dislocation density and the p-modulation doped GaAs barrier layer in the active region, the RIN level is found very stable with temperature with a minimum value of − 150 d B / H z . The dynamical features extracted from the RIN spectra show that p-doping between zero and 20 holes/dot strongly modifies the modulation properties and gain nonlinearities through increased internal losses in the active region and thereby hinders the maximum achievable bandwidth. Overall, this Letter is important for designing future high-speed and low-noise QD devices integrated in future photonic integrated circuits.

This work reports on an investigation of the optical feedback in an InAs/InGaAs passively mode-locked quantum dot (QD) laser epitaxially grown on silicon. Under the stably-resonant optical feedback condition, experiments demonstrate that the radio-frequency linewidth is narrowed whatever the bias voltage applied on the saturable absorber (SA) is; on the other hand, the effective linewidth enhancement factor of the device increases with the reverse bias voltage on the SA, hence it is observed that such an increase influences the mode-locking dynamic and the stability of device under optical feedback. This work gives insights for stabilizing epitaxial QD mode-locked lasers on silicon which is meaningful for their applications in future large-scale silicon electronic and photonic applications requiring low power consumption as well as for high-speed photonic analog-to-digital conversion, intrachip/interchip optical clock distribution and recovery.

We present the overview of the results on the development of compact THz setups based on the quantum dot photoconductive antennas obtained during the past five years. We demonstrate the potential of the InAs/GaAs Quantum-Dot based setups to become an efficient approach to compact, room-temperature operating CW and pulsed terahertz setups for spectroscopy and imaging. We describe the photoelectronic processes in quantum dot substrates and reveal the role of quantum dots in free carrier lifetimes and the formation of the ultrafast photocurrent. We demonstrate the operation mode of the proposed antennas in pulsed and CW regimes under resonant (carriers are excited only inside the quantum dots) and off-resonant (carriers are excited in the bulk volume of the substrate) pumps with compact quantum dot semiconductor lasers. The results allow suggesting the quantum dot based setups as a new approach to field condition compact THz sources for imaging and spectroscopy.

The paper presents the results of experimental studies of the influence of the local anodic oxidation control parameters on the geometric parameters of oxide nanoscale structures (ONS) and profiled nanoscale structures (PNS) on the surface of epitaxial structures of silicon doped gallium arsenide with an impurity concentration of 5 &times, 1017 cm&minus, 3. X-ray photoelectron spectroscopy measurements showed that GaAs oxide consists of oxide phases Ga2O3 and As2O3, and the thickness of the Ga2O3 layer is 2&ndash, 3 times greater than the thickness of As2O3 area&mdash, i.e., the oxidized GaAs region consists mainly of Ga2O3. The experimental studies of the influence of ONS thickness on the resistive switching effect were obtained. An increase in the ONS thickness from 0.8 &plusmn, 0.3 to 7.6 &plusmn, 0.6 nm leads to an increase in the switching voltage Uset from 2.8 &plusmn, 0.3 to 6.8 &plusmn, 0.9 V. The results can be used in the development of technological processes for the manufacturing of nano-electronic elements, such as ReRAM, as well as a high-efficiency quantum dot laser.

Discovered recently, tensile-strained quantum dots are optically active, defect-free nanostructures. Large tensile strains allow us to tailor band structures for applications from tunable infrared emitters to entangled photon sources. I will discuss the history, current state-of-the-art, and future directions of this rapidly expanding research field.

Auger recombination, a process closely related to the device reliability, of a working 2 µm InGaSb/AlGaAsSb quantum well (QW) laser is first investigated via measuring its spontaneous emission. By extracting and analyzing the Z power parameter, severe Auger recombination at relatively low current density/carrier density of GaSb-based lasers has been experimentally revealed.

During air or liquid cooling, thermal resistance of the devices is measured precisely from the thermal information at the junction. But existing thermal measurement technologies fall short because of highly transient events such as unstable vortex formation (air cooling) and bubble growth (two-phase liquid cooling). In solving this problem, this paper reports a novel and low-cost thermal mapping technique that can capture highly spatio-temporal temperature evolution at the solid-liquid interface. Essentially, a robust interface is fabricated with CuInS 2 /ZnS Quantum dots (λ peak = 550 nm and 750 nm) trapped inside nanopores (20 nm-30 nm) of a ceramic membrane (50 µm) and/or everyday use paper. It is observed that such nanoconfinement assisted Quantum dots provided sustained thermal photoluminescence coefficient (-0.1 nm/°C) at high number of heating-cooling cycle. This unique yet low cost thermal mapping technique is applied to capture thermal evolution during micro-droplet impingement cooling and hemiwicking flows through anisotropic wicks which showcase commendable spatio-temporal benefits.

High quality III-Vs on Si are a promising candidate for high efficiency, cost-effective tandem solar cells due to the superior optoelectronic properties of III-Vs and low cost of Si. In recent years, progress towards the integration of high-quality, monolithically-grown III-Vs on Si has been made through careful control of the GaP on Si nucleation step [1]. A variety of pretreatments have successfully been used to modify the surface reconstruction of the Si to prevent the formation of antiphase domains (APDs) [2]– [5]. This has led to promising III-V/Si multijuction solar cell results, with efficiencies now exceeding 20% [6], [7].

An InAs/InGaAs quantum dot laser with a heterostructure epitaxially grown on a silicon substrate was used to fabricate injection microdisk lasers of different diameters (15&ndash, 31 &micro, m). A post-growth process includes photolithography and deep dry etching. No surface protection/passivation is applied. The microlasers are capable of operating heatsink-free in a continuous-wave regime at room and elevated temperatures. A record-low threshold current density of 0.36 kA/cm2 was achieved in 31 &micro, m diameter microdisks operating uncooled. In microlasers with a diameter of 15 &micro, m, the minimum threshold current density was found to be 0.68 kA/cm2. Thermal resistance of microdisk lasers monolithically grown on silicon agrees well with that of microdisks on GaAs substrates. The ageing test performed for microdisk lasers on silicon during 1000 h at a constant current revealed that the output power dropped by only ~9%. A preliminary estimate of the lifetime for quantum-dot (QD) microlasers on silicon (defined by a double drop of the power) is 83,000 h. Quantum dot microdisk lasers made of a heterostructure grown on GaAs were transferred onto a silicon wafer using indium bonding. Microlasers have a joint electrical contact over a residual n+ GaAs substrate, whereas their individual addressing is achieved by placing them down on a p-contact to separate contact pads. These microdisks hybridly integrated to silicon laser at room temperature in a continuous-wave mode. No effect of non-native substrate on device characteristics was found.

Lasers with multi-wavelength colloidal quantum dots (CQDs) can be achieved using complex grating structures and flexible substrate. The structure contains graduated periods and rectangular cavity fabricated through interference lithography, which acts as the distributed feedback cavity. A layer of densely packed CQD film is deposited on the cavity via spin coating technique. The performance of CQD lasers based on different distributed feedback cavities is investigated. Multi-wavelength lasing is achieved based on a flexible rectangular cavity.

International audience; This work reports on the optical feedback dynamics of InAs/GaAs QD lasers epitaxially grown on silicon operating in both the short and long delay regimes. Both undoped and p-doped QD lasers are considered. Whatever the external cavity length, no chaotic oscillations are observed on both samples as a result of the small α-factor observed in the silicon QD lasers. Despite that, experiments conducted in the short-cavity region raise period-one oscillation for the undoped QD laser. In addition, the transition from the short to long delay regimes can be finely covered by varying the external cavity length from 5 cm to 50 cm, and the boundaries associated to the appearance of the periodic oscillation are identified. In the short-cavity region, boundaries show some residual undulations resulting from interferences between internal and external cavity modes; whereas in the long-delay regime, the feedback ratio delimiting the boundaries keeps decreasing, until it progressively becomes rather independent of the external cavity length. Overall, our results showed that the p-doped device clearly exhibits a much higher tolerance to the different external feedback conditions than the undoped one, seeing that its periodic oscillation boundaries are barely impossible to retrieve at the maximum feedback strength of-7 dB. These results show for the first time the p-modulation doping effect on the enhancement of feedback insensitivity in both short-and long-delay configurations, which is of paramount importance for the development of ultra-stable silicon transmitters for photonic technologies.

We demonstrate 10.8 Tbit/s (16-QAM 48×28 GBaud PDM) coherent data transmission over 100-km of standard single mode fiber using an InAs/InP quantum dot mode-locked laser with a channel spacing of 34.2 GHz., Optical Fiber Communication Conference (OFC), March 8-12, 2020, San Diego, California

Most comb research is focused on the generation of pulses. However, frequency combs can also exhibit a very different behavior that is characterized by a continuous output intensity – the frequency modulated (FM) comb regime. Here, we present our theory including a new master equation to describe the involved physical mechanisms and explain which conditions need to be fulfilled to generate self-starting FM combs. Using our new insights we will discuss experimental observations of FM combs in quantum cascade lasers, as well as lasers with slower dynamics, such as interband cascade, quantum well and quantum dot laser.

The small-signal dynamic response of quantum dot (QD) lasers with asymmetric barrier layers (ABLs) is studied. The modulation bandwidth of this novel type of laser is shown to have a maximum as a function of the dc component of the pump current and parameters of the structure. This provides a clear path for optimizing the laser structure to enhance its bandwidth. The effect of non-instantaneous capture of electrons and holes into QDs on the modulation bandwidth is studied. The maximum bandwidth and the optimum dc injection current at which it is attained are calculated as functions of the capture cross-section. The optimum dc injection current is shown to be considerably lower in ABL QD lasers as compared to conventional QD lasers, i.e., the maximum bandwidth is easier to attain in ABL QD lasers.

Experiments on QD lasers grown on GaAs and on Si have revealed the quenching of the GS optical power as the current overcomes the ES threshold. A common technique to mitigate this quenching is the modulation p-doping, but an excessive p-doping level results in a deterioration of the GS optical power and threshold current. Theoretical models based on rate equations have ascribed the GS power quenching to the de-synchronization between the electron and hole dynamics. However, these approaches resort to phenomenological transport times. In this contribution, we study a 1.3 um QD laser grown on silicon by employing a drift-diffusion model for the transport of carriers across the SCH region. We show that the unbalance of electron and hole mobilities in the GaAs barriers is responsible for the GS quenching. The simulations also emphasize the existence of an optimum modulation p-doping level minimizing the GS threshold current, which we ascribe to electrostatic effects induced by this doping.

This paper describes a theory for mode locking and frequency comb generation by four-wave mixing in a semiconductor quantum-dot active medium. The derivation uses a multimode semiclassical laser theory that accounts for fast carrier collisions within an inhomogeneous distribution of quantum dots. Numerical simulations are presented to illustrate the role of active medium nonlinearities in mode competition, gain saturation, carrier-induced refractive index and creation of combination tones that lead to locking of beat frequencies among lasing modes in the presence of cavity material dispersion.

In this paper we review our recent progress on high performance mode locked InAs quantum dot lasers that are directly grown on CMOS compatible silicon substrates by solid-source molecular beam epitaxy. Different mode locking configurations are designed and fabricated. The lasers operate within the O-band wavelength range, showing pulsewidth down to 490 fs, RF linewidth down to 400 Hz, and pulse-to-pulse timing jitter down to 6 fs. When the laser is used as a comb source for wavelength division multiplexing transmission systems, 4.1 terabit per second transmission capacity was achieved. Self-mode locking is also investigated both experimentally and theoretically. The demonstrated performance makes those lasers promising light source candidates for future large-scale silicon electronic and photonic integrated circuits (EPICs) with multiple functionalities.

In this paper, for the first time, the switchable two-color quantum dot laser has been realized considering solution process technology, which has both simultaneous and lonely lasing capability exploiting selective energy contacts. Furthermore, both channels can be modulated independently, which is a significant feature in high-speed data transmission. To this end, utilizing superimposed quantum dots with various radii in the active layer provides the different emission wavelengths. In order to achieve the different sizes of QDs, solution process technology has been used as a cost-effectiveness and fabrication ease method. Moreover, at the introduced structure to accomplish the idea, the quantum wells are used as separate selective energy contacts to control the lasing channels at the desired wavelength. It makes the prominent device have simultaneous lasing at different emission wavelengths or be able to lase just at one wavelength. The performance of the proposed device has been modeled based on developed rate equation by assuming inhomogeneous broadening of energy levels as a consequence of the size distribution of quantum dots and considering tunnel injection of carriers into the quantum dots via selective energy contacts. Based on simulation results, the simultaneous lasing in both or at one of two wavelengths 1.31 μm and 1.55 μm has been realized by the superimposition of two different sizes of InGaAs quantum dots in a single cavity and accomplishment of selective energy contacts. Besides, controlling the quantum dot coverage leads to managing the output power and modulation response at the desired wavelengths. By offering this idea, one more step is actually taken to approach the switchable QD-laser by the simple solution process method.

Direct epitaxial growth of III-V lasers on silicon provides the most economically favorable means of photonic integration but has traditionally been hindered by poor material quality. Relative to commercialized heterogeneous integration schemes, epitaxial growth reduces complexity and increases scalability by moving to 300 mm wafer diameters. The challenges associated with the crystalline mismatch between III-Vs and Si can be overcome through optimized buffer layers including thermal cyclic annealing and metamorphic layers, which we have utilized to achieve dislocation densities 10,000,000 h). At 60°C, lasers with extrapolated time-to-failure >50,000 h have been demonstrated for >4,000 h of continuous aging. Lasers have also been investigated for their performance under optical feedback and showed no evidence of coherence collapse at back-reflection levels of 100% (minus 10% tap for measurement) due to the ultralow linewidth enhancement factor (αH < 0.2) and high damping of the optimized quantum dot active region.

We investigate the degradation processes that limit the long-term lifetime of 1.3 μm quantum dot lasers grown on silicon substrate. The analysis is based on combined optical and electrical characterization, carried out before and during accelerated ageing tests. Specifically, we demonstrate that: (i) when submitted to constant current stress, the analyzed devices show a monotonic increase in threshold current; (ii) degradation kinetics are strongly dependent on stress current; a power-law dependence of TTF on stress current was extrapolated (TTF proportional to J^-3.9). (iii) during stress time, a decrease in slope efficiency was detected, well correlated to the threshold current increase. This effect was ascribed to a decrease in injection efficiency of the devices. (iv) A detailed analysis of the degradation kinetics showed that the threshold current increase has a square-root dependence on stress time, indicating the presence of a defect-diffusion process, that degrades the properties of the active region. Finally (v), the analysis of the spectral characteristics plots indicates that stress is impacting quantum dots with high energy emission preferentially. The results collected within this paper are explained by considering that stress promotes the diffusion of defects towards the active region of the devices. This mechanism results in a decrease in the SRH recombination lifetime, and in the subsequent increase in threshold current and drop in sub-threshold emission. An increase in the SRH rate next to the quantum dots can also reduce the injection efficiency into the QDs, thus inducing a drop in the slope efficiency of the lasers.

The temperature behavior of operating characteristics in semiconductor lasers with a quantum-confined active region is studied with a proper account for (i) non-instantaneous capture of charge carriers from the waveguide region into the active region and (ii) internal optical loss that depends on the carrier densities. Because of (i), the carrier densities are not pinned in the lasing mode, i.e., they are functions of the injection current. In view of (ii) and as a result of pump-currentdependence of the carrier densities, so becomes the internal loss coefficient. This in turn leads to the roll-over of the light-current characteristic at high currents (i.e., decreasing optical power with increasing injection current) and, under certain conditions, appearance of the second branch in it. The laser characteristics are shown to transform qualitatively with varying temperature: they are conventional, i.e., consist of one branch, at low temperatures but they have two branches, i.e., are of a binary nature, at high temperatures. The two branches merge together at the maximum operating current beyond which the lasing quenches. In contrast to the first (conventional) lasing threshold, the threshold for emerging the second branch decreases with increasing temperature. The pump-current-dependence of the carrier densities and internal loss coefficient is also fascinating: these quantities decrease with increasing current in their second branches.

The small and large signal responses of InP-based 1.55 μm high-speed quantum dot (QD) lasers with and without tunnel-injection (TI) quantum well (QW) and/or p-type doping in the active region (incorporating nominally identical QDs) were designed, manufactured and compared. The structures were grown by a molecular beam epitaxy system equipped with group-V valved cracker cells. In all cases, the active region consisted of six QD or TI-QD structures, which were embedded in InAlGaAs barriers lattice matched to InP. The InGaAs TI-QWs were separated by a thin InAlGaAs tunnel barrier from the InAs QDs. The laser structures were processed into ridge waveguide lasers and analyzed. The results show, that the bandwidth and maximum data rates were reduced by incorporation of TI-QWs. P-doping resulted in slightly worse performance of the simple QD laser, but in an improvement of the TI QD laser. Furthermore, the large signal response of the tunneling injection QD laser is one of the first reports of digital modulation of such a laser. An optimization of the doping profile is promising to further improve the laser performance over the undoped counterparts.

In Opt. Lett. 44, 5755 (2019)OPLEDP0146-959210.1364/OL.44.005755, a factor is missing in the result of Eq. (1). Thus, the width of the comb spectrum Δ ν becomes Δ ν = 2 3 Γ α e .

We report electrically pumped, continuous-wave (cw) InAs/GaAs quantum dot (QD) lasers directly grown on quasi-nominal Si (001) substrates with offcut angle as small as 0.4°. No GaP, Ge buffer layers or substrate patterning is required. An anti-phase boundary free epitaxial GaAs film was grown by metal-organic chemical vapor deposition (MOCVD) with a low threading dislocation density of ${3\times 10^{7} {\rm{cm^{-2}}}}$ . Room-temperature cw lasing at ∼1.3 μm has been achieved, with a minimum threshold current density of 34.6 A/cm2 per layer, a maximum operating temperature of 80 °C, and a maximum single facet output power of 52 mW. A comparison of various monolithic III-V hetero-epitaxy on Si solutions is presented. Direct growth on unpatterned quasi-nominal (001) Si may yield the best material quality at the lowest lifecycle cost.

The emission spectrum of a superradiant laser is calculated analytically using quantum Langevin equations. New sideband peaks and fine structure in the spectrum are predicted for lasers with strong relaxation oscillations.

1550 nm InAs/InAlGaAs quantum dash lasers exhibit higher modulation efficiencies and bandwidths than the InGaAsP-based quantum well lasers. Their lasing thresholds, output powers and temperature stabilities are greatly improved after the high reflectance coating.

An InAs-on-InP quantum dash buried heterostructure laser and silicon chip optimized for mutual integration by direct facet-to-facet coupling have achieved -1.2 dB coupling efficiency, with coupled laser RIN of -150 dB/Hz and 152 kHz linewidth., 2020 22nd International Conference on Transparent Optical Networks (ICTON), July 19-23, 2020, Bari, Italy

MOCVD grown aluminum-free quantum dot lasers have been demonstrated with a maximum wall-plug efficiency of 30%, a lowest threshold current of 8 mA, and a maximum single-facet output power of 200 mW.

International audience; We analyze the nonlinear dynamics of a semiconductor laser with optical injection from a frequency comb. When varying both the injection parameters (detuning and injection ratio) and the comb properties (number of comb lines and comb spacing), we identify and select several dynamics, including (1) injection locking with selective amplification of the comb line that shows the smallest detuning from the injected laser, (2) unlocked time-periodic dynamics that correspond to a new frequency comb with a broadened optical spectrum, thereby sharpening the pulse generated at the injected laser output, and (3) unlocked chaotic dynamics.

User-friendly single-photon sources with high photon-extraction efficiency are crucial building blocks for photonic quantum applications. For many of these applications, such as long-distance quantum key distribution, the use of single-mode optical fibers is mandatory, which leads to stringent requirements regarding the device design and fabrication. We report on the on-chip integration of a quantum dot (QD) microlens with a 3D-printed micro-objective in combination with a single-mode on-chip fiber coupler. The practical quantum device is realized by the deterministic fabrication of the QD-microlens via in situ electron-beam lithography and the 3D two-photon laser writing of the on-chip micro-objective and fiber chuck. A QD with a microlens is an efficient single-photon source, whose emission is collimated by the on-chip micro-objective. A second polymer microlens is located at the end facet of the single-mode fiber and ensures that the collimated light is efficiently coupled into the fiber core. For this purpose, the fiber is placed in an on-chip fiber chuck, which is precisely aligned to the QD-microlens thanks to the sub-micrometer processing accuracy of high-resolution two-photon direct laser writing. The resulting quantum device has a broadband photon extraction efficiency, a single-mode fiber-coupling efficiency of 22%, a measured single-photon flux of 42 kHz (8.9 kHz) under cw (pulsed) optical excitation, which corresponds to 1.5 MHz (0.3 MHz) at the single-mode fiber output, and a multi-photon probability in terms of g(2)(0) = 0.00±0.04/0.00 (0.13 ± 0.05) under cw (pulsed) optical excitation. The stable design of the developed fiber-coupled quantum device makes it highly attractive for integration into user-friendly plug-and-play quantum applications.

We demonstrate widely tunable, narrow linewidth, heterogeneous QD lasers utilizing Vernier ring resonators, setting a record for integrated lasers in the O-band with 47 nm tuning range, 52 dB SMSR, and 9.5 kHz Lorentzian linewidth.

We theoretically investigate power-induced lasing state switching and bistability in a two-state quantum dot laser subject to optical injection. The simulated results show that, for a free-running two-state quantum dot laser operating at the ground state under low current, a power-induced lasing state switching between the ground state and the excited state can be achieved through introducing optical injection with a frequency (winj) close to the lasing frequency of excited state (wES). The injection power required for the state switching depends on the scanning route of injection power, i.e. there may exist state bistability for the injection power within a certain region. For forward scanning injection power, with the increase of frequency detuning (ΔΩ = winj – wES), the injection power required for the state switching shows a decreasing trend accompanied by slight fluctuations. However, for backward scanning injection power, the injection power required for the state switching exhibits obvious fluctuations with the increase of ΔΩ. The width of the hysteresis loop fluctuates with ΔΩ, and the fluctuation amplitude is increased with the increase of the injection current. Additionally, the influences of the inhomogeneous broadening factor and the electron escape rate on the bistability performances are analyzed.

This presentation will look at co-packaged optics to reduce power consumption in the data center while considering some of the challenges ahead. We will also discuss other opportunities for energy savings and how photonics can enable it.

© 1983-2012 IEEE. High-performance III-V quantum-dot lasers monolithically grown on Si substrates have been demonstrated as a promising solution to realize Si-based laser sources with very low threshold current density, high output power, and long lifetime, even with relatively high density of defects due to the material dissimilarities between III-Vs and Si. On the other hand, although conventional III-V quantum-well lasers grown on Si have been demonstrated after great efforts worldwide for more than 40 years, their practicality is still a great challenge because of their very high threshold current density and very short lifetime. However, the physical mechanisms behind the superior performance of silicon-based III-V quantum-dot lasers remain unclear. In this paper, we directly compare the performance of a quantum-well and a quantum-dot laser monolithically grown on on-axis Si (001) substrates, both experimentally and theoretically, under the impact of the same density of threading dislocations. A quantum-dot laser grown on a Si substrate with a high operating temperature (105 °C) has been demonstrated with a low threshold current density of 173 A/cm2 and a high single facet output power >100 mW at room temperature, while there is no lasing operation for the quantum-well device at room temperature even at high injection levels. By using a rate equation travelling-wave model, the quantum-dot laser's superior performance compared with its quantum well-based counterpart on Si is theoretically explained in terms of the unique properties of quantum dots, i.e., efficient carrier capture and high thermal energy barriers preventing the carriers from migrating into defect states.

We have investigated the cavity-resonant excitation of quantum dot which is spectrally and spatially coupled with the fundamental mode of micropillar, achieving a single photon source that is highly efficient both in excitation and emission. © 2020 The Author(s)

We study phase-noise spectral properties of comb lines from a QD-MLL, show that their large linewidth variability attributes to the low-frequency phase variations, and has minimal effect on coherent system performance at practical symbol rates.

We report the first demonstration of an offset quantum dot laser platform which enables integration of active gain section with passive waveguide section. Based on this platform, we have designed and fabricated dispersion compensated offset quantum dot mode-locked lasers.

Recent advances in midwave infrared interband cascade lasers (ICLs) include novel distributed feedback configurations, vertical-cavity surface-emitting lasers, light-emitting devices, frequency combs, dual-comb spectroscopy, and ICLs incorporated into photonic integrated circuits on silicon and III-V platforms.

We demonstrate an optimized structure design and analyze the optical mode characteristics of 1.55 µm Si-based III-V square microcavity laser with InAs/InGaAs quantum-dot active region and directional midpoint output waveguide. © 2020 The Author(s)

The huge progress in laser miniaturization opens new fields of research at the crossroads between nanophotonics and nonlinear dynamics. Cavity-enhanced microcavities exhibit lasing close to the quantum regime and are excellent testbeds for exploring nonlinear dynamics at the low-power limit by optical injection. Quantum dot micropillar lasers exhibit a bimodal behavior that features intrinsic dynamics and intriguing photon statistics. In the present thesis, the photon number distribution of two qualitatively different types of microlasers is investigated and injection locking of quantum dot micropillar lasers is explored. The photon statistics is an important measure for the evidence of lasing in high-β microlasers operating at sub-μW light powers. Utilizing the outstanding photon detection capabilities of transition-edge sensors, the full photon number distribution of microlaser is measured for the first time to obtain profound insight into the emission dynamics of these nanophotonic devices. For bimodal quantum dot micropillar laser, two cases are distinguished. In the first case of a stable microlaser, one polarization mode undergoes a transition from thermal emission below threshold to a lasing state above threshold. Meanwhile, the other polarization mode transfers to a non-lasing thermal state. In the second case of a bistable quantum dot micropillar, both polarization modes have the potential to reach the lasing regime and the photon number distribution exhibits a superposition of a thermal and a coherent distribution in a single measurement. This behavior was inaccessible with common experimental techniques and is revealed by the photon number distribution. The second type of microlaser under investigation is an exciton-polariton laser which is based on stimulated scattering and Bose-Einstein condensation of quasi-particles and not on population inversion as it is required for conventional photon lasers. The transition to lasing is investigated by means of the photon number distribution. The photon statistics exhibits a coherence buildup well described by thermal-coherent states. Slight deviations from the model can serve as the starting point for the examination with competing theories. In the following experiments, quantum dot micropillar lasers are subject to optical injection. A single-mode microlaser reveals locking to the master laser. However, at the boundaries, the microlaser discloses a ’partial locking’ to the master laser which is a novel effect of the enhanced spontaneous emission. Optical injection into the non-lasing mode pushes this mode to lasing. Moreover, optical injection causes stochastic mode switching between the modes, depending on their relative strength and spectral detuning. In summary, measurements of the photon statistics and optical injection experiments reveal new dynamics of microlasers and yield deeper insights into their physics. The results of this thesis have high potential to pave the way for the control of dynamics close to the quantum regime which is crucial for future applications, e.g. in photonic reservoir computing., Der enorme Fortschritt in der Laserminiaturisierung eröffnet neue Forschungsansätze im Spannungsfeld zwischen Nanophotonik und nichtlinearer Dynamik. Resonatorverstärkte Mikrokavitäten führen zu Laseremission nahe des Quantenregimes und eignen sich daher hervorragend als Versuchsobjekte, um durch optische Injektion an der unteren Leistungsgrenze die nichtlineare Dynamik zu erforschen. Quantenpunkt-Mikrosäulen-Laser zeigen ein bimodales Verhalten, welches sich durch intrinsische Dynamik und faszinierende Photonenstatistiken auszeichnet. Im Rahmen dieser Arbeit wird die Photonenzahlverteilung zweier qualitativ unterschiedlicher Typen von Mikrolasern und optische Injektion von Quantenpunkt-Mikrosäulen-Lasern untersucht. Die Photonenstatistik ist ein wichtiges Maß für den Nachweis von Laseremission in Mikrolasern mit einem hohem β-Faktor, welche mit Leistungen unterhalb des μW-Regimes arbeiten. Unter Ausnutzung der hervorragenden Photonendetektionseigenschaften von supraleitenden Phasenübergangsthermometern (Transition-Edge Sensors) wird die vollständige Photonenzahlverteilung von Mikrolasern zum ersten Mal gemessen. Dadurch ergibt sich ein tieferer Einblick in die Emissionsdynamik von Mikrolasern. Im Zusammenhang mit bimodalen Quantenpunkt-Mikrosäulen-Lasern werden zwei Fälle unterschieden. Im ersten Fall eines stabilen Mikrolasers geht die eine Polarisationsmode von einer thermischen Emission unterhalb der Laserschwelle in einen lasenden Zustand oberhalb der Laserschwelle über. Währenddessen geht die andere Polarisationsmode in einen nicht-lasenden Zustand über. Im zweiten Fall eines bistabilen Quantenpunkt-Mikrosäulen-Lasers können beide Polarisationsmoden das Laserregime erreichen und die Photonenzahlverteilung zeigt eine Überlagerung einer thermischen und einer kohärenten Verteilung in einer Einzelmessung. Dieses Verhalten war unzugänglich mit üblichen experimentellen Techniken und wurde durch die mittels eines supraleitenden Phasenübergangsthermometers gemessene Photonenzahlverteilung aufgedeckt. Der zweite hier untersuchte Mikrolasertyp ist ein Exziton-Polariton-Laser. Dieser beruht auf stimulierter Streuung und Bose-Einstein-Kondensation von Quasiteilchen und steht damit im Gegensatz zu einem herkömmlichen Photonenlaser, welcher auf Besetzungsinversion basiert. Der Übergang zu Lasing wird anhand der Photonenzahlverteilung untersucht. Die Photonenstatistik zeigt einen durch thermisch-kohärente Mischzustände gut beschriebenen Kohärenzaufbau. Geringe Abweichungen vom Modell können als Ausgangspunkt für die Überprüfung konkurrierender Theorien dienen. In den folgenden Experimenten werden Quantenpunkt-Mikrosäulen-Laser optisch injiziert. Dabei zeigt sich eine Phasen- und Frequenzangleichung eines Einzelmoden-Mikrolasers an den Master-Laser. An den Grenzen offenbart der Mikrolaser jedoch eine "teilweise Angleichung" an den Master-Laser. Letzteres stellt einen neuartigen Effekt, hervorgerufen durch die verstärkten spontanen Emission dar. Die optische Injektion treibt die nichtlasende Mode in einen lasenden Zustand. Darüber hinaus bewirkt die optische Injektion eine stochastische Umschaltung zwischen den Moden in Abhängigkeit von ihrer relativen Stärke und der spektralen Verstimmung. Zusammenfassend lässt sich sagen, dass Messungen der Photonenstatistik und Experimente zur optischen Injektion neue Dynamiken von Mikrolasern aufzeigen und tiefere Einblicke in ihre Physik geben. Die Ergebnisse dieser Dissertation weisen ein hohes Potential auf, den Weg für die Kontrolle der Dynamik von Mikrolasern nahe des Quantenregimes zu ebnen. Dies ist für zukünftige Anwendungen, wie beispielsweise im Reservoir Computing, von entscheidender Bedeutung.

This work investigates the performance of 1.3-μm quantum dot lasers epitaxially grown on silicon under optical feedback sensitivity with different temperature and doping profiles. Experiments show that these quantum dot lasers exhibit a very high degree of resistance to both incoherent and coherent optical feedbacks. 10 Gbps penalty-free transmissions are also unveiled under external modulation and at different temperatures. The paper draws attention on quantum dot lasers with p-doping that exhibit a better thermal resistance, a lower linewidth enhancement factor, a higher critical feedback level, and a better spectral stability with less intensity noise. Together, these properties make epitaxial quantum dot lasers with p-doping more promising for isolator-free and Peltier-free applications, which are meaningful for future high-speed photonic integrated circuits.

We demonstrated a single section mode-locked laser monolithically grown on Si with 23.5 GHz repetition rate. With self-injection feedback locking setup, the RF linewidth of MLL was reduced ~100 times from 900kHz to 8kHz. © 2020 The Author(s)

We report the first directly modulated single-mode tunable quantum dot lasers at 1.3 pm. 27-channel wavelength switching was achieved with side-mode-suppression-ratio of around 35 dB without requiring nonuniform gratings or epitaxial regrowth.

We present spectroscopy measurements of individual InAsP quantum dots in photonic nanowires [1] using (i) a home-build Czerny Turner spectrometer with an astronomy camera and (ii) an economical sub-picometre laser wavemeter from MOGLabs®.

We present our work on a hybrid silicon quantum dot-based comb laser using wafer bonding. The device has a 3, 6, and 10 dB comb width of 12 nm, 18 nm, and 25 nm respectively.