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Silicon photonics is the core technology in the post-Moore ’ s era, characterized by the deep integration of optoelectronics and microelectronics. Silicon photonics can leverage the existing complementary metal-oxide-semiconductor (CMOS) infrastructure to fabricate low power consumption, high integration density, fast transmission speed, and highreliability silicon photonic chips which are widely employed in data centers and communication systems. At present, most optoelectronic devices like Si-based photodetectors and Si-based optical modulators have realized on-chip integration except for the Si-based lasers as essential light sources. The directly epitaxial III-V materials on silicon substrates is recognized as one of the most promising solutions to achieve low-cost and large-size monolithic integration of Si-based lasers, still facing many significant challenges. In this paper, the research progress of Si-based light sources is presented from the aspects of directly epitaxial on-axis III-V/ Si (001) substrates, on-axis Si-based laser materials, epitaxy technology and monolithic integration at first. Then the achievements in Si-based directly epitaxial quantum well lasers and quantum dot lasers in our group are reported in detail, including the growth of antiphase domains-free GaAs/ Si (001) substrates, epitaxial materials of InGaAs/ AlGaAs quantum well lasers and InAs/ GaAs quantum dot lasers, and fabrication of novel coplanar electrode structures of silicon photonic chips in parallel mode. [ABSTRACT FROM AUTHOR]

We report for the first time the direct growth of quantum dot (QD) lasers with electrical pumping on 300 mm Si wafers on both a planar template and in-pocket template for in-plane photonic integration. O-band lasers with five QD layers were grown with molecular beam epitaxy (MBE) in a 300 mm reactor and then fabricated into standard Fabry–Perot ridge waveguide cavities. Edge-emitting lasers are demonstrated with high yield and reliable results ready for commercialization and scaled production, and efforts to make monolithically integrated lasing cavities grown on silicon-on-insulator (SOI) wafers vertically aligned and coupled to SiN waveguides on the same chip show the potential for 300 mm-scale Si photonic integration with in-pocket direct MBE growth. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are zero-dimensional (0D) nanomaterials with charge confinement in all directions that significantly impact various applications. Metal-free organic quantum dots have fascinating properties such as size-dependent bandgap tunability, good optical absorption coefficient, tunability of absorption and emission wavelength, and low-cost synthesis. Due to the extremely small scale of the materials, these characteristics originated from the quantum confinement of electrons. This review will briefly discuss the use of QDs in solar cells and quantum dots lasers, followed by a more in-depth discussion of QD application in photodetectors. Various types of metallic materials, such as lead sulfide and indium arsenide, as well as nonmetallic materials, such as graphene and carbon nanotubes, will be discussed, along with the detection mechanism. [ABSTRACT FROM AUTHOR]

The effect of the phase conjugate coupling on routes to chaos (mainly stable, sustained pulsating oscillations, evolves into double-period oscillation and quasi-periodic routes) in incoherent optical feedback semiconductor quantum dot laser is theoretically investigated using bifurcation diagrams, time series, attractors and inter-spike interval probability distribution. The parameter values of the coupling strength (η) and delay time (τ) (mirrors respond as fast and slow-response photorefractive mirrors) are modified to examine the sensitivity of routes to chaos with variation in the phase-conjugate mirrors. Both routes are found to be highly sensitive to the phase conjugate coupling effect. Instability and homoclinic chaotic can be observed in such a system. [ABSTRACT FROM AUTHOR]

In this report, we measured experimentally the modal absorption spectra of the InP and InAsP quantum dot (QD) lasers using multi-section device technique. The optical absorption cross section (σ0) and inhomogeneous broadening for the ground state (GS) and excited state (ES) were analyzed and calculated theoretically from the absorption spectra. The results showed that the InP QD laser exhibited σ0 to be 1.347×10−14 ​cm2.eV and 3.016×10−14 ​cm2eV for GS and ES respectively, whereas for the InAsP QD material it was found as 0.511×10−14cm2eV and 3.099×10−14cm2.eV for GS and ES respectively. Moreover, the inhomogeneous broadening in the GS increases from 35.6 eV to 63.6 eV when As was added to InP QD, similarly, the inhomogeneous broadening of ES increases from 46.9 eV to 103.8 eV. The alloying InP QDs with arsenic decreases the σ0 of the ground state (lasing state) and increases both inhomogeneous and linewidth broadenings. This finding may help the grower to control the growth conditions and the molecule fractions of the crystal to improve the spectral properties of the optoelectronics devices.

We report for the first time the direct growth of quantum dot (QD) lasers with electrical pumping on 300 mm Si wafers on both a planar template and in-pocket template for in-plane photonic integration. O-band lasers with five QD layers were grown with molecular beam epitaxy (MBE) in a 300 mm reactor and then fabricated into standard Fabry–Perot ridge waveguide cavities. Edge-emitting lasers are demonstrated with high yield and reliable results ready for commercialization and scaled production, and efforts to make monolithically integrated lasing cavities grown on silicon-on-insulator (SOI) wafers vertically aligned and coupled to SiN waveguides on the same chip show the potential for 300 mm-scale Si photonic integration with in-pocket direct MBE growth.

Based on the cascade relaxation model of the quantum dot (QD) lasers, the nonlinear dynamics of a two-state QD laser subject to optical injection is numerically studied. The simulation results show that, for a two-state QD laser operating at the ground-state (GS) and excited-state (ES) emission simultaneously, through adjusting the injection parameters, the two emission states can display the stable (S), injection locking (IL), suppression (SP), period-one (P1), period-two (P2), multi-period (MP), and chaotic pulse (CP) states when the frequency of the injection light is close to the GS lasing frequency. Further mapping of these dynamic states in the parameter space of frequency detuning and injection strength, it is found that the complex dynamic behaviors are mainly distributed in the negative frequency detuning region. In addition, the complexity of the chaotic signal is qualified by the permutation entropy (PE) calculating, and the high complexity signal with PE value over 0.95 is obtained. Moreover, within a certain frequency detuning range, the ES emission can be effectively suppressed by increasing the injection strength. [ABSTRACT FROM AUTHOR]

The introduction of a closely stacked quantum dot (QD) structure is considered as one of the most effective approaches to extend the emission wavelength of InAs/GaAs QDs beyond 1.3 μm (1300 nm). Herein, a trilayer QD structure (three closely stacked QD layers) is proposed to further extend the emission wavelength of QDs. Room‐temperature (RT) emission at 1418 nm from InAs/GaAs trilayer QDs is demonstrated. Moreover, based on these results, an E‐band InAs/GaAs trilayer QD laser is fabricated on a GaAs substrate, achieving RT oscillation at 1370 nm with a low threshold current density of 96 A cm−2 under continuous‐wave mode operation. The results indicate that the trilayer QD structure is promising for realizing high‐performance QD lasers on GaAs substrate over 1300 nm without incorporating metamorphic buffer layers. [ABSTRACT FROM AUTHOR]

The family of III-nitride materials has provided a platform for tremendous advances in efficient solid-state lighting sources such as light-emitting diodes and laser diodes. In particular, quantum dot (QD) lasers using the InGaN/GaN material system promise numerous benefits to enhance photonic performance in the blue wavelength regime. Nevertheless, issues of strained growth and difficulties in producing InGaN QDs with uniform composition and size pose daunting challenges in achieving an efficient blue laser. Through a review of two previous studies on InGaN/GaN QD microdisk lasers, we seek to provide a different perspective and approach in better understanding the potential of QD emitters. The lasers studied in this paper contain gain material where QDs are sparsely distributed, comprise a wide distribution of sizes, and are intermixed with “fragmented” quantum well (fQW) material. Despite these circumstances, the use of microdisk cavities, where a few distinct, high-quality modes overlap the gain region, not only produces ultralow lasing thresholds (∼6.2 μJ/cm2) but also allows us to analyze the dynamic competition between QDs and fQWs in determining the final lasing wavelength. These insights can facilitate “modal” optimization of QD lasing and ultimately help to broaden the use of III-nitride QDs in devices.

Monolithic integration of III-V quantum dot (QD) lasers onto a Si substrate is a scalable and reliable approach for obtaining highly efficient light sources for Si photonics. Recently, a combination of optimized GaAs buffers and QD gain materials resulted in monolithically integrated butt-coupled lasers on Si. However, the use of thick GaAs buffers up to 3 μm not only hinders accurate vertical alignment to the Si optical waveguide but also imposes considerable growth costs and time constraints. Here, for the first time, we demonstrate InAs QD lasers epitaxially grown on a 700 nm thick GaAs/Si template, which is approximately four times thinner than the conventional III-V buffers on Si. The optimized 700 nm GaAs buffer yields a remarkably smooth surface and low threading dislocation density of 4 × 10 8 cm -2 , which is sufficient for QD laser growth. The InAs QD lasers fabricated on these ultrathin templates still lase at room temperature with a threshold current density of 661 A/cm 2 and a characteristic temperature of 50 K. We believe that these results are important for the monolithically integrated III-V QD lasers for Si photonics applications.

The family of III-nitride materials has provided a platform for tremendous advances in efficient solid-state lighting sources such as light-emitting diodes and laser diodes. In particular, quantum dot (QD) lasers using the InGaN/GaN material system promise numerous benefits to enhance photonic performance in the blue wavelength regime. Nevertheless, issues of strained growth and difficulties in producing InGaN QDs with uniform composition and size pose daunting challenges in achieving an efficient blue laser. Through a review of two previous studies on InGaN/GaN QD microdisk lasers, we seek to provide a different perspective and approach in better understanding the potential of QD emitters. The lasers studied in this paper contain gain material where QDs are sparsely distributed, comprise a wide distribution of sizes, and are intermixed with "fragmented" quantum well (fQW) material. Despite these circumstances, the use of microdisk cavities, where a few distinct, high-quality modes overlap the gain region, not only produces ultralow lasing thresholds (∼6.2 μJ/cm2) but also allows us to analyze the dynamic competition between QDs and fQWs in determining the final lasing wavelength. These insights can facilitate "modal" optimization of QD lasing and ultimately help to broaden the use of III-nitride QDs in devices. [ABSTRACT FROM AUTHOR]

Monolithic integration of III–V materials and devices on CMOS compatible on‐axis Si (001) substrates enables a route of low‐cost and high‐density Si‐based photonic integrated circuits. Inversion boundaries (IBs) are defects that arise from the interface between III–V materials and Si, which makes it almost impossible to produce high‐quality III–V devices on Si. In this paper, a novel technique to achieve IB‐free GaAs monolithically grown on on‐axis Si (001) substrates by realizing the alternating straight and meandering single atomic steps on Si surface has been demonstrated without the use of double Si atomic steps, which was previously believed to be the key for IB‐free III–V growth on Si. The periodic straight and meandering single atomic steps on Si surface are results of high‐temperature annealing of Si buffer layer. Furthermore, an electronically pumped quantum‐dot laser has been demonstrated on this IB‐free GaAs/Si platform with a maximum operating temperature of 120 °C. These results can be a major step towards monolithic integration of III–V materials and devices with the mature CMOS technology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The barrier layer thickness separating the dot-in-well structure in optoelectronic devices plays a crucial impact on the performance of these devices. Here, we report the effect of the barrier width in quantum dot (QD) laser. Three series of InAsP QD lasers were papered with different barrier widths (i.e., 8, 16, and 24 nm) of (AlGa)InP. The samples were prepared by MOVPE at 730 °C. Data of threshold current density, J th giving a lower J th for 8 nm barrier width sample and it becomes more temperature dependency evident by a low value of characteristic temperature, T o ≈ 77 k. Emission spectra of 2 mm long lasers showed a blue-shift by approximately 11 nm when the barrier width increased from 8 to 24 nm. The modal absorption study showed a decrease in the inhomogeneous broadening for 24 nm barrier width sample. Simulation results revealed an increase in the optical absorption cross-section, σ o with increasing barrier width. These results showed that significant improvements in the spectral properties of the InAsP QD lasers can be made by altering the (AlGa)InP barrier width. • The effect of the barrier width of (AlGa)InP quantum wells (i.e., 8, 16, and 24 nm) on the operation of InAsP QD lasers was investigated. • 8-nm barrier width sample revealed lower threshold current density. • Lasing emission showed an 11 nm blue-shift when the barrier width varied from 8 to 24 nm. • The inhomogeneous broadening of the ground state and exited states decreases at 24-nm barrier width sample. • Simulation results raveled increase of the optical absorption cross-section σ o , with increasing barrier width. • Significant improvements on the optical and spectral properties of the InAsP QD lasers can be made by altering the (AlGa)InP barrier width. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear rate equations governing a quantum dot laser isused to simulate the transient as well as the steady-state behaviors of the laser.Computation results show that the rate equations are capable of simulating true behaviorof a quantum dot laser. Then, the pump rates of the rate equations (which show indirectelectrical pumping of the quantum dots through a wetting layer) are changed so thatthey can show direct electrical pumping of the quantum dots. Simulation results predictthat a quantum dot laser with direct pumping has much lower threshold current than theindirect one. It is also shown that duration time of the transient regime to reach steadystate operation is shorter in direct pumping.

The effect of out-tunneling leakage of carriers from quantum dots (QDs) on modulation bandwidth of semiconductor double tunneling-injection (DTI) QD lasers is studied. In this type of laser, as an alternative to conventional pumping, electrons and holes are injected into QDs by tunneling from two separate quantum wells (QWs) located on the opposite sides of the QD layer and separated from the latter by thin barrier layers. Fast tunneling-injection into QDs should be maintained to ensure the high modulation bandwidth. It may also seem that out-tunneling leakage from QDs (tunneling of electrons to the hole-injecting QW and holes to the electron-injecting QW), which is an undesirable process, should be kept as slow as possible (or even totally suppressed) to maximize the modulation bandwidth. However, it is shown in this paper that, due to zero-dimensional nature of QDs, the modulation bandwidth is practically unaffected by out-tunneling leakage from them—it depends only slightly on the out-tunneling time. Hence, concerning out-tunneling leakage, DTI QD lasers are robust—provided that tunneling-injection is fast, no significant effort should be necessary to suppress out-tunneling leakage in practical devices. [ABSTRACT FROM AUTHOR]

Aiming to realize high-speed optical transmitters for isolator-free telecommunication systems, 1.3 μm p-modulation doped InGaAs/GaAs quantum dot (QD) lasers with a 400 μm long cavity have been reported. Compared with the un-doped QD laser as a reference, the p-doped QD laser emits at ground state, with an ultra-low threshold current and a high maximum output power. The p-doped QD laser also shows enhanced dynamic characteristics, with a 10 Gb/s large-signal direct modulation rate and a 7.8 GHz 3dB-bandwidth. In addition, the p-doped QD laser exhibits a strong coherent optical feedback resistance, which might be beyond −9 dB.

The spontaneous emission spectra of a 1.28?m InAs/GaAs QD (Quantum Dot) Fabry-Perot laser device has been measured under continuous wave operation at a fixed junction temperature of 300K. At low carrier densities, empirically observed static peak wavelength position and a fixed spectral shape of the spontaneous emission spectra are indicative of the random-like population distribution rather than a global Fermi level in the system. A theoretical model based on the Monte-Carlo method has been shown to have good agreement with the empirical results. In addition the evolutions of spontaneous emission spectral shapes are also explained in terms of many body effects.

This paper reports a hybrid integrated light source fabricated on a silicon platform using a 1.3 μm wavelength quantum dot array laser. Temperature insensitive characteristics up to 120 °C were achieved by the optimum quantum dot structure and laser structure. Light output power was obtained that was high enough to achieve an optical error-free link of a silicon optical interposer. Furthermore, we investigated a novel spot size convertor in a silicon waveguide suitable for a quantum dot laser for lower energy cost operation of the optical interposer.

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We propose a tunable dual-wavelength heterogeneous quantum dot laser diode. The tunable dual-wavelength laser consists of a quantum dot semiconductor optical amplifier as the optical gain medium and an external cavity fabricated from silicon photonics technology as the wavelength tunable filter. We successfully demonstrated dual-wavelength lasing oscillation by tuning the difference frequency from approximately 34 to 400 GHz. [ABSTRACT FROM AUTHOR]

In this paper, modulation bandwidth characteristics of InGaAs/GaAs quantum dot (QD) laser were theoretically investigated. Simulation was done by using the fourth order Runge-Kutta method. Effect of carrier relaxation life time, temperature and current density on characteristics of tunneling injection QD laser (TIL) and conventional QD laser (CL) were analyzed. Results showed that tunneling injection in QD laser increases the modulation bandwidth indicating that it is very useful for using in the fiber optic communication systems.

The nondegenerate four-wave mixing (NDFWM) characteristics in a quantum-dot Fabry-Perot laser are investigated, employing the dual-mode injection-locking technique. The solitary laser features two lasing peaks, which provides the possibility for efficient FWM generation. Under optical injection, the NDFWM is operated up to a detuning range of 1.7 THz with a low injection ratio of 0.42. The normalized conversion efficiency (NCE) and the side-mode suppression ratio (SMSR) with respect to the converted signal are analyzed. The highest NCE of -17 dB associated with a SMSR of 20.3 dB is achieved at detuning of 110 GHz.

In this paper, a G a A s / A l x G a 1 − x A s quantum dot laser with a semi-parabolic spherical well potential is assumed. By using Runge-Kutta method the eigenenergies and the eigenstates of valence and conduct bands are obtained. The effects of geometrical sizes, external electric fields and hydrogen impurity on the different electronic transitions of the optical gain are studied. The results show that the optical gain peak increases and red-shifts, by increasing the width of well or barrier, while more increasing of the width causes blue-shift and decreases it. The hydrogen impurity decreases the optical gain peak and blue-shifts it. Also, the increasing of the external electric fields cause to increase the peak of the optical gain, and (blue) red shift it. Finally, the optical gain for 1s–1s and 2s–1s transitions is prominent, while it is so weak for other transitions. [ABSTRACT FROM AUTHOR]

In this paper, the effects of temperature, hydrostatic pressure and size on optical gain for GaAs spherical quantum dot laser with hydrogen impurity are investigated. For this purpose, the effects of temperature, pressure and quantum dot size on the band gap energy, effective mass, and dielectric constant are studied. The eigenenergies and eigenstates for valence and conduction band are calculated by using Runge-Kutta numerical method. Results show that changes in the temperature, pressure and size lead to the alteration of the band gap energy and effective mass. Also, increasing the temperature redshifts the optical gain peak and at special temperature ranges lead to increasing or decreasing of it. Further, by reducing the size, temperature-dependent of optical gain is decreased. Additionally, enhancing of the hydrostatic pressure blueshifts the peak of optical gain, and its behavior as a function of pressure which depends on the size. Finally, increasing the radius rises the redshifts of the peak of optical gain. [ABSTRACT FROM AUTHOR]