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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]

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]

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]

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]

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, 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]

Delay identification from the chaotic intensity output of a quantum dot laser with optical feedback is done using numerical and information theoretic techniques. Four quantifiers, namely autocorrelation function, delayed mutual information, permutation entropy and permutation statistical complexity, are employed in delay estimation. A detailed comparison of these quantifiers with different feedback rates and delay is undertaken. Permutation entropy and permutation statistical complexity are calculated with different dimensions of symbolic reconstruction to obtain the best results. [ABSTRACT FROM AUTHOR]

We propose an optimized quasiperiodic microcavity with the aim of achieving the highest quality factor. The proposed structure consists of two quasicrystal rings with different geometries. By performing several optimizations on the structure, the highest quality factor of 8.16 × 107 for a femtosecond laser with a wavelength of 1040 nm can be achieved. The quasiperiodic microcavity is used for a quantum dot laser application that obtained the highest output power of 3800 W/m2. The most important characteristics of this structure are the improvement of the quality factor and a simultaneously stable cavity wavelength. [ABSTRACT FROM AUTHOR]

Self-assembled InAs quantum dots (QDs) were grown by solid source molecular beam epitaxy. The impact of the growth parameters like the growth temperature of the InGaAlAs nucleation layer, V/III ratio and growth rate during growth of QD layers were carefully investigated by using atomic force microscopy and photoluminescence spectroscopy. The excellent size uniformity of InAs QDs grown on InP substrates are verified by narrow photoluminescence line widths of 17 meV for single QD layers and 26 meV for stacked QD layers, respectivaly. Both values measured at 10 K. [ABSTRACT FROM AUTHOR]

Since the external cavity quantum dot laser was first demonstrated, the performances have been improved in terms of operation temperature, output power, pulse generator and tuneability based on the naturally size fluctuation of quantum dot. Nowadays, the external cavity quantum dot sources have been successfully used in different absorption spectroscope techniques, in industry, biomedical and research. In this paper we reviewed the recent developments of quantum dot lasers operated in a grating-coupled external cavity system where a single frequency and wide tunable wavelength range were easily obtained by adjusting the grating angle. In all cases, we mainly stressed the significant progresses in understanding of basic optical and electronic properties to enable the importance steps forward. The prospects for further progress directed towards stability, mode-hoping-free tuning range, miniaturization and integration of the external cavity quantum dot lasers also reviewed. [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. [ABSTRACT FROM AUTHOR]

• The gain-switched method is more advantageous to obtain short pulses, owing to its simple implementation and low production costs. • Short pulse generation with a width of 25–40 ps with a high peak power from excited state of InAs-InP (1 1 3)B quantum dot laser by applying an external optical beam to the laser excited state. • Short optical pulses with high response speeds and peak power are in demand in many fields, such as high-speed optical communication, medical biotechnology, clock distribution, electro–optic sampling systems, etc. • Study incorporates the science and technology underlying quantum electronics. For generating picoseconds or sub-picosecond optical pulses having a moderate peak power, semiconductor lasers are preferred as sources owing to their compatibility, cost-effectivity, easy integrability with other optoelectronic devices, and electrical pumping characteristics. As a result, semiconductor lasers that are based on small-size heterostructures, such as quantum dot lasers, are very promising for such applications. The gain switching characteristics and the effect of laser parameters on the output pulses of an InAs-InP (1 1 3)B quantum dot laser are investigated for the first time using theoretical models to obtain shorter pulses by applying an external optical beam to the laser excited state. The model is based on the rate equations, which are solved by the Runge –Kutta method. The results showed that without an optical beam, long pulse widths are obtained because of the ground state transition, and the change in the parameters strongly affects the laser output. However, with an optical beam illumination, short pulses with a width of 25–40 ps with a high peak power are generated owing to the excited state transition at low currents, and the change in the laser parameters does not affect the output pulses strongly. These results are important for long-distance optical transmissions as well as medical biotechnology. [ABSTRACT FROM AUTHOR]

We present a theoretical study of a quantum-dot-based microcavity laser where two nearly degenerate high- Q modes are involved in the laser dynamics. To analyze the coupled carrier-photon system we have extended a single mode microscopic semiconductor theory to the case of two modes and have also taken the crosscorrelation functions into account. Our theoretical results show that the mode which loses the mode competition exhibit super-thermal photon bunching ( [ABSTRACT FROM AUTHOR]

An InAs/GaAs quantum dot laser, fabricated with a narrow-striped width of 6 μm by a wet etching technique, is reported. The etching solutions are composed of three components, i.e. phosphoric acid, hydrogen peroxide, and deionized water. We observed that the unavoidable undercutting was changed with the ratio of etching solution in the GaAs materials. By taking a suitable ratio of etching solution, good performance of quantum dot laser with a size of 6 μm × 700 μm was achieved for fabrication at room temperature. Under continuous wave mode, the lasing wavelength exhibited a single mode, which is located in the region of 1051 nm. In contrast, multimode lasing with a series of non-lasing gaps appeared and the spectra were gradually broadened to the high energy side by increasing the injection current. The laser has one facet power more than 22 mW, with a slope efficiency of 140 mW/A, just a little above threshold current. [ABSTRACT FROM PUBLISHER]

Abstract: We report on the lasing characteristics of InAs/InP(100) quantum dots laser through changing the temperature under continuous-wave mode. Three lasing peaks are simultaneously observed at temperature of 80K and the lasing order of each peak is unrelated with each other when injection current increases. Laser spectra obtained under fixed current for different temperatures show a drastic influence on their shape. A large spectral broadening is observed at low temperature, while the width of lasing spectra gradually narrows when the operating temperature increased. The lasing process of quantum dot laser is obviously different from that of a reference quantum well laser in the same wavelength region. In addition, very high wavelength stability of 0.088nm/K in the temperature range of 80–300K is obtained, which is 6.2 times better than that of reference quantum well laser. [Copyright &y& Elsevier]

In this paper, for the first time, we present a semiclassical noise model for InAs/GaAs quantum dot (QD) laser considering two photon modes, i.e., ground and first excited states lasing. This model is based on the five level rate equations. By using this model, the effect of temperature variations on relative intensity noise (RIN) of QD laser is investigated. We find that the RIN significantly degrades when excited state (ES) lasing emerges at high temperature. Furthermore, we investigate the influence of the quantum dot numbers on the RIN properties. [ABSTRACT FROM AUTHOR]

Abstract: The I–V characteristics of an InAs/GaAs quantum dot (QD) laser diode have been investigated under both the high and low input current conditions. Under the low current condition, the I–V curve obeys the Shockley equation, from which the forbidden energy gap of the junction can be derived. On the other hand, in the high current range, the I–V characteristics violate the Shockley equation and the device tends to operate as a resistance. In addition, the I–V curve can be used to fit the temperature coefficient of the forward voltage, which is a critical parameter for determining the junction temperature of the laser diode. [Copyright &y& Elsevier]

Abstract: We report on the temperature dependent lasing characteristics of InAs/GaAs quantum dot lasers under continuous wave mode. The five-stacked InAs quantum dots were grown by gas-source molecular beam epitaxy with slightly different thickness. Ridge waveguide laser with stripe width of 6μm was processed on the growth structure. The characteristic temperature was measured as high as infinity in the temperature range of 80–180k. With the increase of injection current, the lasing spectra of laser diode broaden gradually at low temperature of 80k. However, when the operation temperature increases from 80 to 300K, the width of lasing spectrum reduces gradually from 40 to 2.0nm. The lasing process is obviously different from that of a reference quantum well laser which widens its width of lasing spectra by increasing operation temperature. These experiments demonstrate that a carrier transfer from the smaller size of dots into larger dots caused by thermal effect play an important role in the lasing characteristic of quantum dot lasers. In addition, the laser can operate at maximum temperature of 80°C under continuous wave mode with a maximum output power of 52mW from one facet at 20°C. A wavelength thermal coefficient of 0.196nm/K is obtained, which is 2.8 times lower than that of QW laser. The low wavelength thermal coefficient of quantum dot laser is mainly attributed to its broad gain profile and state filling effects. [Copyright &y& Elsevier]

We present experimental results from an edge-emitting diode laser with an active layer consisting of a 2-D patterned quantum well superlattice. We demonstrate control over the density of optical transitions by engineering the unit cell geometry of the lattice. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of an edge-emitting semiconductor laser with a gain medium consisting of two layers of patterned, self-aligned, vertically coupled quantum dots (QDs) using a wet-etching and regrowth technique. A threshold current density of 300 A/cm^2 is demonstrated at 77 K. The presence of emission from QD excited states in both the spontaneous emission and laser spectra indicates 3-D quantum confinement in QDs fabricated using this technique. [ABSTRACT FROM PUBLISHER]

Authors theoretically present the characterization of the multiple states broadband InGaAs/GaAs quantum-dot lasers that agrees well with the measured data. Based on the derived model, this new class of semiconductor laser is further characterized theoretically to gain an idea of the derivative characteristic such as linewidth enhancement factor in providing a picture of the competency of this novel device for diverse applications. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate that excellent 1.3μm QD laser performance can be achieved with the use of a high-temperature step during the growth of the GaAs spacer layers. An optimised laser structure exhibits a very low room-temperature Jth and operates CW from the ground-state up to at least 105°C. Spontaneous emission measurements indicate that the high-temperature performance is limited by non-radiative processes rather than by the thermal excitation of carriers into higher energy QD states. [Copyright &y& Elsevier]

Abstract: GaAsSb strain-reducing layers (SRLs) are applied to cover InAs quantum dots (QDs) grown on GaAs substrates. The compressive strain induced in InAs QDs is reduced due to the tensile strain induced by the GaAsSb SRL, resulting in a redshift of photoluminescence (PL) peaks of the InAs QDs. A strong PL signal around a wavelength of 1.3μm was observed even at room temperature. A laser diode containing InAs QDs with GaAsSb SRLs in the active region was fabricated, which exhibits laser oscillation in pulsed operation at room temperature. These results indicate that GaAsSb SRLs have a high potential for fabricating high efficient InAs QDs laser diodes operating at long-wavelength regimes. [Copyright &y& Elsevier]

Abstract: We have observed ultraviolet lasing of CuCl quantum dots embedded in a NaCl single crystalline matrix. Stable ultraviolet lasing of biexciton (two e–h pairs) luminescence has been achieved below 70K under the two-photon direct excitation of biexcitons of CuCl quantum dots. Laser action occurs with parallely cleaved surfaces of the NaCl crystalline matrix acting as an optical cavity, which shows a very high efficiency of lasing. [Copyright &y& Elsevier]

We have investigated light-current and spectral characteristics of 2-, 5- and 10-stack InAs/InGaAs/GaAs quantum dot (QD) ridge-waveguide lasers grown by MBE. Ultra-low threshold current of 1.43 mA was achieved for 2-stack QD laser. Simultaneous lasing at ground- and excited-states was observed. This effect is accounted for the finite time of carriers capture to the ground-state in QDs. Multi-stack QD structures enables to maintain continuous-wave (CW) ground-state lasing up to the current density of 100×Jth and to achieve the highest output power and efficiency ever recorded for any single-mode lasers of 1.3-μm-wavelength range. [ABSTRACT FROM AUTHOR]

Within the last few years a breakthrough in the device performance of quantum dot lasers occurred and new application areas were opened. Recent advances in the understanding and realisation of quantum dot lasers are reviewed. To cite this article: J.P. Reithmaier, A. Forchel, C. R. Physique 4 (2003). [Copyright &y& Elsevier]

In this paper, the multi-wavelength solution-processed quantum dot laser has been proposed by the superimposed quantum dots. To this end, the rate equation framework has been developed to model the simultaneous lasing in desired wavelengths by considering inhomogeneous broadening of energy level as a result of the size distribution of quantum dots and the homogeneous broadening due to the carries scattering inside quantum dots. Moreover, the solution process technology has been utilized in order to synthesize the quantum dots in various sizes according to the desired wavelengths. The simulation results show that simultaneous lasing has been realized by superimposition of two sizes of InGaAs quantum dots in a single cavity at two wavelengths of 1. 31 μ m and 1. 55 μ m which have special importance in telecommunication applications. Besides, the output power intensity at the desired wavelengths can be managed by controlling the density of quantum dots. [ABSTRACT FROM AUTHOR]

Abstract: We propose the idea of making quantum dot (QD) lasers by embedding direct-bandgap QDs in a short-period superlattice whose bandgap is indirect. In comparison with similar QD lasers with barriers of direct band gap, this technique not only reduces the temperature dependence of threshold current, but also leads to extremely small linewidth enhancement factor, making low-temperature sensitivity, low chirp, and narrow linewidth semiconductor lasers feasible. [Copyright &y& Elsevier]

A high‐performance 1.3 μm InAs/GaAs quantum‐dot laser directly grown on Si substrates has been achieved by using InAlAs/GaAs strained‐layer superlattice serving as dislocation filter layers (DFLs). The Si‐based laser achieves lasing operation up to 111°C with a threshold current density of 200 A/cm2 and an output power exceeding 100 mW at room temperature. [ABSTRACT FROM AUTHOR]