Quantum Dot Lasers Research Articles

Blue lasers using low-toxicity colloidal quantum dots.

Blue lasers play a pivotal role in laser-based display, printing, manufacturing, data recording and medical technologies. Colloidal quantum dots (QDs) are solution-grown materials with strong, tunable emission covering the whole visible spectrum, but the development of QD lasers has largely relied on Cd-containing red-emitting QDs, with technologically viable blue QD lasers remaining out of reach. Here we report on the realization of tunable and robust lasing using low-toxicity blue-emitting ZnSe-ZnS core-shell QDs that are compact in size yet still feature suppressed Auger recombination and long optical gain lifetime approaching 1 ns. These characteristics allow us to handle the blue QDs like laser dyes for liquid-state amplified spontaneous emission and lasing. The blue QD laser is operated under quasi-continuous-wave excitation by solid-state nanosecond lasers. A Littrow-configuration cavity enables narrow linewidth (<0.2 nm), wavelength-tunable, coherent and stable laser outputs without circulating the solution. These results indicate the promise of ZnSe-ZnS QDs to fill the 'blue gap' of QD lasers and to replace less stable blue laser dyes for a multitude of applications.

Electron beam induced multi-wavelength lasing in CdSe quantum dot lasers

Electron beam induced multi-wavelength lasing in CdSe quantum dot lasers

High capacity, low power, short reach integrated silicon photonic interconnects

The architecture and component technology of a low power, high capacity, short reach optical interconnect are detailed. Measurements from high-performance 300 mm silicon photonics components that comprise the system are shown, along with a quantum-dot mode-locked laser 20-channel comb source with free space wall plug efficiencies up to 17%, advanced packaging techniques for 3D silicon photonic-electronic integration, and schematics for integrated electronics that control the photonic integrated circuits. Techniques for operating such a system in the presence of changing ambient temperature are addressed. Experiments on a 1 Tbps design are conducted with an optical link experiment indicating sub-picojoule/bit energy consumption at scale.

Design of the Single Heterogeneous Quantum Dot Lasers Emitting 4 Wavelengths Using Combination‐Grating Technology

AbstractMulti‐wavelength light sources are crucial for high‐bandwidth silicon photonic chips. In this paper, a single heterogeneous quantum dot distributed feedback (DFB) laser emitting 4 wavelengths using the combination‐grating technology is designed. To the best of the knowledge, this is the first heterogeneously integrated quantum dot DFB laser that lases stable multi‐wavelength in a single cavity. When the etching depth, etching width, and total length of gratings are 100 , 550 nm, and 1 000 µm, respectively, 4‐wavelength with 1297.01 , 1303.38 , 1309.74 , and 1316.11 nm are obtained by varying the grating period from 196 to 199 nm with the spacing of 1 nm. Compared to the conventional DFB laser arrays, the DFB laser units are significantly reduced by 3/4 while maintaining the same number of output wavelengths. Additionally, by optimizing the λ/4 phase‐shift position and the duty cycle of gratings, the output power at the front‐end of the 4‐wavelength laser is significantly improved. Specifically, the ratio of the output power from the front‐end and rear‐end of the laser increases from the conventional 1.00 to 2.51. This work provides a competitive candidate for multi‐wavelength, high‐performance, and large‐scale silicon‐based light sources used in data centers, lidar, and component detection.

Improvement of optical noise in optical-injection-locked quantum dot lasers epitaxially grown on silicon by reducing external carrier noise

Abstract This study theoretically investigates the impact of external carrier noise from pumping sources on the optical noise of epitaxial quantum dot (QD) lasers on silicon. The findings indicate that the spectral linewidth and relative intensity noise (RIN) of silicon-based QD lasers using a quiet pump are significantly reduced. At 5.5 times the threshold current, the spectral linewidth decreases from 337.2 kHz to 213.2 kHz, and the RIN decreases from −141.3 dB Hz−1 to −168.8 dB Hz−1. This reduction is attributed to the lower external carrier noise level of the quiet pump, which also suppresses the spectral linewidth rebroadening effect at a high bias current. Moreover, when external optical injection locking is applied, the spectral linewidth further decreases to 24 kHz at an injection ratio of −70 dB and to 1.8 mHz at 0 dB. The RIN also slightly decreases to −172.4 dB Hz−1 with an injection ratio of 10. These results demonstrate that using a quiet pump is an effective and manageable strategy for significantly reducing both the spectral linewidth and RIN of QD lasers, thereby facilitating their application in next-generation photonic integrated circuits, continuous-variable quantum key distribution, quantum computing and ultra-precise quantum sensing.

Two-states quantum dot laser complex dynamics under optically injection

Two-states quantum dot laser complex dynamics under optically injection

Design of 16-wavelength heterogeneous quantum dot laser arrays with varying silicon waveguide width and grating period

Design of 16-wavelength heterogeneous quantum dot laser arrays with varying silicon waveguide width and grating period

Rare earth Nd3+-doped organic-inorganic hybrid perovskite quantum dots for white LED

Lead halide perovskite quantum dots (QDs) have garnered significant attention due to their tunable band gaps, unique quantum confinement effects, and high photoluminescence quantum yields (PLQYs). Among them, Organic-inorganic QDs make them promising candidates for optoelectronic devices such as quantum dot light-emitting diodes (QLEDs), solar cells, lasers, and photodetectors. However, the toxicity of lead (Pb) has raised environmental and health concerns, hindering their industrial application. To alleviate concerns about heavy metals Pb, extensive research has been conducted on B-site doping and the development of lead-free perovskites. Herein, we firstly developed B-site doping strategy on organic-inorganic hybrid perovskite QDs via rare-earth elements. Neodymium (III) (Nd3+) doped FAPbBr3 QDs were prepared through the ligand-assisted reprecipitation method at room temperature. The B-site doping strategy could alleviate the heavy metal problem of Pb and modulate the band gap of FAPbBr3 QDs facilely. The results demonstrated that increasing the concentration of Nd³⁺ can change the emission of FAPbBr₃ QDs from pure green to deep blue. Specifically, we achieved highly pure blue emission (∼438 nm) with a full width at half maximum (FWHM) of 13 nm for Nd³⁺-doped FAPbBr₃ QDs. Time-resolved photoluminescence (TRPL) spectroscopy revealed a decrease in the lifetime of FAPbBr₃ QDs from 22.86 to 15.46 ns as the doping concentration increased. Additionally, we fabricated a white LED (WLED) utilizing blue-emitting Nd³⁺-doped FAPbBr₃, green-emitting FAPbBr₃ QDs, and red QDs, achieving a white emission color coordinate of (0.33, 0.36). This study pioneers the application of B-site rare-earth doping in organic-inorganic hybrid perovskite QDs, demonstrating that B-site composition engineering is a reliable strategy to further exploit the perovskite family for wider optoelectronic applications.

Quantum dot fourth-harmonic colliding pulse mode-locked laser for high-power optical comb generation

Quantum-dot mode-locked lasers have advantages such as high temperature stability, large optical bandwidth, and low power consumption, which make them ideal optical comb sources, especially for wavelength-division multiplexing (WDM) telecommunications, and optical I/O applications. In this work, we demonstrate an O-band quantum dot colliding pulse mode-locked laser (QD-CPML) to generate optical frequency combs with 200 GHz spacing with maximum channels of 12 within 3 dB optical bandwidth. To achieve the high output power of individual comb lines, four channel conditions are implemented at central wavelength of 1310 nm for WDM transmission experiments. Each channel exhibits more than 10 dBm output power with 200 Gb/s PAM-4 and 270 Gb/s PAM-8 modulation capability via thin-film LiNbO3 Mach–Zehnder interferometer modulator without the requirement of any optical amplifications. This high-order QD-CPML is an ideal comb source for power-efficient optical interconnects and large bandwidth optical data transmission.

Design of 16-wavelength high-power heterogeneous III-V/Si laser arrays with varying stripe width and grating period

Multi-wavelength laser array is currently one of the most attractive technologies to provide high density links for advanced optical communications and computing. The conventional scheme of varying grating period is almost impossible to achieve 8-wavelength or more. And, the optical output power of heterogeneously integrated quantum dot laser can hardly meet the commercial demand. In this paper, we report a 16-wavelength high-power heterogeneously integrated quantum dot distributed feedback laser array. To the best of our knowledge, this is the first heterogeneously integrated quantum dot laser array that tunes the lasing wavelength by combining the scheme of varying the stripe width and grating period of laser units. The effective refractive index of gratings is calculated by eigenmode expansion method. When the grating period is fixed at 198 nm, and the stripe widths of laser units are 2.00 μm, 2.25 μm, 2.60 μm and 3.15 μm, respectively, the corresponding lasing wavelengths are 1307.94 nm, 1308.49 nm, 1309.06 nm and 1309.63 nm, respectively, and the wavelength spacing of the adjacent laser units is about 100 GHz. By additionally adjusting the grating period between 196 nm and 202 nm with 2 nm spacing of grating period, a 16-wavelength QD DFB laser array is designed with the wavelength range from 1294.73 nm to 1336.09 nm. In addition, asymmetric distributed feedback grating is adopted to improve the optical output power at the front-end of laser arrays. The maximum ratio of the output power at the both end of laser units is 19.6 when the grating duty cycles of the front-end and the back-end of the λ/4 phase-shift is 0.7 and 0.5, respectively, and the grating lengths is 250 μm and 450 μm, respectively. This work will promote the performance improvement of heterogeneously integrated quantum dot lasers and develop the quantum dot lasers towards multi-wavelength.

(Invited) Epitaxial III-V Nanomaterials on the Si Platform for Quantum and Data Communications

As Si-based integrated photonic components begin to replace older technologies for optical data communications, the need for better integration of semiconductor lasers on the Si platform is greater than ever. In addition, emerging interest in integrated-photonic-based quantum computing and quantum sensing presents a further need for quantum light emitters—entangled and single-photon—on Si. III-V quantum dots represent a promising solution, both for the active region of telecommunications-wavelength lasers and for quantum emitters. However, epitaxial quantum dots grown on conventional (100) substrates typically lack the high symmetry required for entangled-photon emission.This presentation will discuss our recent work to develop a novel approach for III-V direct growth on Si via an ultrathin (<10 nm) single crystal strain relieving buffer layer, realized by the selective oxidation and condensation of an amorphous SiGe surface layer. The fabrication and properties of this novel Ge-rich buffer layer, as well as its use for subsequent III-V organometallic vapor-phase epitaxy will be presented.The second part of the talk will present our recent work on the epitaxial growth and characterization of (In,Ga)As quantum dots for the above-mentioned applications. Specifically, I will show that surface-energy-modifying surfactants (Sb, Bi) present the possibility to externally direct quantum dot formation “on-demand” in strained InAs layers on GaAs(111) substrates, where quantum dot formation by the Stranski–Krastanov process does not naturally occur. These nanostructures are prospective for high-symmetry entangled-photon emitters. The three-dimensional (3D) composition profile of InAs quantum dot layers is characterized by atom-probe microscopy (APT), elucidating the real-world quantum dot matrix. This 3D composition data is input into a finite element solver to determine the quantum dot energies and wavefunctions for electrons and holes. The modeling reveals that in high-density quantum dot layers, the electron and hole states are hybridized between multiple quantum dots in the matrix. This has important consequences for design of quantum dot light emitters. The predicted transition energies are in agreement with low-temperature photoluminescence. This work constitutes a promising approach for integrating telecommunications-wavelength quantum dot lasers and entangled photon emitters on the Si integrated photonics platform.

1.3 µm InAs/GaAs Quantum‐Dot Lasers with p‐Type, n‐Type, and Co‐Doped Modulation

AbstractTo further enhance the performance and understand the mechanism of InAs quantum dot (QD) laser under high temperature, both theoretically and experimentally it is investigated, the effects of the technique of the combination of direct n‐type doping and modulation p‐type doping, namely co‐doping, in the active region for a wide temperature range over 165 °C. Through the comparison of co‐doped, modulation p‐type doped, direct n‐type doped, and undoped QD lasers, it reveals that the co‐doping technique provides a significantly reduced threshold current density across the whole temperature range and robust high‐temperature operation. Furthermore, it is also observed that the effectiveness of co‐doping in suppressing round‐state quenching is comparable to that of p‐doping. The improvements in the doping strategies are also revealed through the rate equation simulation of the lasers.

Broadband amplitude squeezing at room temperature in electrically driven quantum dot lasers

The generation of squeezed states of light lies at the heart of modern photonics-based quantum information technologies. Traditionally, optical nonlinear interactions have been employed to produce squeezed states. However, the harnessing of electrically pumped semiconductor lasers offers distinctive paradigms to achieve enhanced squeezing performance for real-world applications. We present the first evidence that quantum dot lasers enable the realization of broadband amplitude-squeezed states at room temperature across a wide frequency range, spanning from 3 GHz to 12 GHz. Our findings are corroborated by a stochastic simulation in agreement with the experimental data. Published by the American Physical Society 2024

Design of high power evanescent quantum dot distributed feedback lasers on Si

Great advancements in III–V/Si epitaxy have pushed quantum dot lasers to the forefront of silicon photonics. In this work, we designed the structures of evanescent coupled quantum dot distributed feedback lasers with asymmetric gratings, which made significant improvement in on-chip output power while maintaining single-longitudinal-mode stability. The optimal λ/4 phase-shift position (the ratio of the grating length from the rear-end of λ/4 phase-shift to the total grating length) from conventional position of 0.50 to 0.64 allows the ratio of the output power at both sides of silicon waveguide to be increased from 1.0 to 5.9. Moreover, the optimal duty cycle at one side of the phase-shift from 0.50 to 0.8 allows the ratio to be increased from 1.0 to 3.7. Meanwhile, the ratio could be dramatically improved from 1.0 to 9.2 by changed the duty cycle at one side of phase-shift to 0.7 while maintaining the phase-shift position of 0.64. With those designed structures, evanescent coupled quantum dot lasers could challenge the state-of-the-art bonded quantum well lasers and may eventually become ubiquitous and affordable for future commercial production.

Experimental Investigation on the Dynamics Characteristics of a Two-State Quantum Dot Laser under Optical Feedback

Experimental Investigation on the Dynamics Characteristics of a Two-State Quantum Dot Laser under Optical Feedback

Nonlinear Dynamics of Silicon-Based Epitaxial Quantum Dot Lasers under Optical Injection

For silicon-based epitaxial quantum dot lasers (QDLs), the mismatches of the lattice constants and the thermal expansion coefficients lead to the generation of threaded dislocations (TDs), which act as the non-radiative recombination centers through the Shockley–Read–Hall (SRH) recombination. Based on a three-level model including the SRH recombination, the nonlinear properties of the silicon-based epitaxial QDLs under optical injection have been investigated theoretically. The simulated results show that, through adjusting the injection parameters including injection strength and frequency detuning, the silicon-based epitaxial QDLs can display rich nonlinear dynamical states such as period one (P1), period two (P2), multi-period (MP), chaos (C), and injection locking (IL). Relatively speaking, for a negative frequency detuning, the evolution of the dynamical state with the injection strength is more abundant, and an evolution path P1-P2-MP-C-MP-IL has been observed. Via mapping the dynamical state in the parameter space of injection strength and frequency detuning under different SRH recombination lifetime, the effects of SRH recombination lifetime on the nonlinear dynamical state of silicon-based epitaxial QDLs have been analyzed.

Heterogeneous quantum dot lasers on low-confinement silicon nitride with reduced-bending architecture.

Low-confinement silicon nitride (SiN) waveguides offer ultra-low losses but require wide bend radii to avoid radiative losses. To realize the benefits of silicon nitride in a heterogeneous laser while maintaining a small footprint, we employ metal-coated etched facets and transversely coupled Fabry-Perot resonators as mirrors. Heterogeneous quantum dot lasers are fabricated using an on-chip facet plus adiabatic taper coupler, and Fabry-Perot cavities are defined by metal mirrors and post-grating-distributed Bragg reflectors (DBRs). Threshold current densities below 250 A/cm2 are observed, and a power >15 mW is measured in an integrating sphere. A laser linewidth of <5 MHz is measured by tuning two lasers to about 50 MHz apart and measuring their beatnote on a photodiode. The total device footprint is <1 mm2.

Low‐Defect Quantum Dot Lasers Directly Grown on Silicon Exhibiting Low Threshold Current and High Output Power at Elevated Temperatures

The direct growth of III‐V materials on silicon is a key enabler for developing monolithically integrated lasers, offering substantial potential for ultradense photonic integration in vital communications and computing technologies. However, the III‐V/Si lattice and thermal expansion mismatch pose significant hurdles, leading to defects that degrade lasing performance. This study overcomes this challenge, demonstrating InAs/GaAs‐on‐Si lasers that perform on par with top‐tier lasers on native GaAs substrates. This is achieved through a newly developed epitaxial approach comprising a series of rigorously optimized growth strategies. Atomic‐resolution scanning tunneling microscopy and spectroscopy experiments reveal exceptional material quality in the active region and elucidate the impact of each growth strategy on defect dynamics. The optimized III‐V‐on‐silicon ridge‐waveguide lasers demonstrate a continuous‐wave threshold current as low as 6 mA and high‐temperature operation reaching 165 °C. At 80 °C, critical for data center applications, they maintain a 12 mA threshold and 35 mW output power. Furthermore, lasers fabricated on both Si and GaAs substrates using identical processes exhibit virtually identical average threshold current. By eliminating the performance limitations associated with the GaAs/Si mismatch, this study paves the way for robust and high‐density integration of a broad spectrum of critical III‐V photonic technologies into the silicon ecosystem.

Numerical investigation on nonlinear dynamics of two-state quantum dot laser subject to optical injection

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.

Integration of O-band quantum dot lasers with AlGaN/GaN waveguides.

We integrate edge-emitting etched-facet InAs/GaAs quantum dot (QD) lasers to an AlGaN/GaN-on-sapphire waveguide platform via micro-transfer printing. The lasers are placed into a trench etched into the sapphire substrate so as to transversely align the waveguides. The AlGaN/GaN waveguide structure is designed to allow for tolerant alignment of the active lasing mode to the passive waveguide mode. 4 μm wide waveguides show a TE propagation loss of 4.5 dB/cm. For a QD laser with a 1.2 mm long cavity and 3.5 μm wide ridge waveguide, 2.3 mW was measured at 80 mA under continuous wave conditions from the end of a 0.64 cm long 4 μm wide waveguide with an estimated coupling efficiency of >20 %. The measured coupled output power is 1.5 mW at 70°C and 100 mA. To our knowledge, this is the first demonstration of the heterogeneous integration of a GaAs lasing device to a GaN-based PIC by any means. The results show real promise for GaN to be a suitable platform for integrated photonics applications requiring O-band operation.