Single-facet Output Power Research Articles

1.3 μm InAs/GaAs quantum-dot lasers grown on planar on-axis Si (001) substrates with high slope-efficiency and low differential resistance

We report electrically pumped continuous-wave (CW) InAs/GaAs quantum dot lasers monolithically grown on planar on-axis Si (001) substrates. Combining an asymmetric waveguide epitaxy structure with aluminium-free upper cladding layers and a symmetrical cathode chip structure, 1.3 μm band lasers with low differential resistance and high slope-efficiency have been achieved. Moreover, the optimized symmetrical cathode structure of the laser chips is used to improve the slope-efficiency by reducing the differential resistance and waste heat. The Fabry–Perot broad-stripe edge-emitting lasers with 2000 μm cavity length and 15 μm stripe width achieve a single-facet output power of 73 mW, a single-facet slope efficiency of 0.165 W A−1, and a differential resistance of 1.31 Ω at ∼1.31 μm wavelength under CW conditions at room temperature (25 °C). Importantly, these results provide an effective strategy to achieve 1.3 μm wavelength band single-mode distributed feedback lasers directly on planar on-axis Si (001) substrates with high efficiency.

High thermal performance hybrid GaInAsP/SOI ridge waveguide lasers with enhanced heat dissipation structure

Hybrid GaInAsP/SOI ridge waveguide Fabry–Pérot lasers with reduced thermal resistance were fabricated and measured. The lasers were formed by room-temperature surface-activated bonding of InP and silicon-on-insulator wafers. Thin SiO2 film was introduced as ridge-sidewall insulation to increase heat flow to the p-electrode side-metal. By incorporating a thermal shunt structure and Au electroplating, a single-facet output power of 20 mW and lasing operation up to 110 °C were achieved for a cavity length of 2.0 mm under continuous-wave conditions. The proposed structure showed low thermal resistance of 14.3 K W−1 and a threshold current density of approximately 0.7 kA cm−2.

Demonstration of room-temperature continuous-wave operation of InGaAs/AlGaAs quantum well lasers directly grown on on-axis silicon (001)

Room-temperature continuous-wave operation of InGaAs/AlGaAs quantum well lasers directly grown on on-axis silicon (001) has been demonstrated. A 420 nm thick GaAs epilayer completely free of antiphase domains was initially grown on the silicon substrate in a metal-organic chemical vapor deposition system and the other epilayers, including four sets of five-period strained-layer superlattices and the laser-structural layers, were successively grown in a molecular beam epitaxy system. The lasers were prepared as broad-stripe Fabry–Pérot ones with a stripe width of 21.5 μm and a cavity length of 1 mm. Typically, the threshold current and the corresponding threshold current density are 186.4 mA and 867 A/cm2, respectively. The lasing wavelength is around 980 nm, and the slope efficiency is 0.097 W/A with a single-facet output power of 22.5 mW at an injection current of 400 mA. This advancement makes the silicon-based monolithic optoelectronic integration relevant to quantum well lasers more promising with an enhanced feasibility.

Monolithic Integration of O-Band InAs Quantum Dot Lasers with Engineered GaAs Virtual Substrate Based on Silicon.

The realization of high-performance Si-based III-V quantum-dot (QD) lasers has long attracted extensive interest in optoelectronic circuits. This manuscript presents InAs/GaAs QD lasers integrated on an advanced GaAs virtual substrate. The GaAs layer was originally grown on Ge as another virtual substrate on Si wafer. No patterned substrate or sophisticated superlattice defect-filtering layer was involved. Thanks to the improved quality of the comprehensively modified GaAs crystal with low defect density, the room temperature emission wavelength of this laser was allocated at 1320 nm, with a threshold current density of 24.4 A/cm−2 per layer and a maximum single-facet output power reaching 153 mW at 10 °C. The maximum operation temperature reaches 80 °C. This work provides a feasible and promising proposal for the integration of an efficient O-band laser with a standard Si platform in the near future.

High wall-plug efficiency and narrow linewidth III-V-on-silicon C-band DFB laser diodes.

We present recent results on compact and power efficient C-band distributed feedback lasers through adhesive bonding of a III-V die onto a silicon-on-insulator circuit. A wall-plug efficiency up to 16% is achieved for bias currents below 40 mA. The laser cavity is 180 µm long and a single facet output power up to 11 mW is measured at 20 °C by incorporating a broadband reflector in the silicon waveguide at one side of the cavity. Single mode operation at 1567 nm with a side mode suppression ratio of around 55 dB is demonstrated. By controlling the phase of the external feedback, the laser linewidth is decreased to 28 kHz. Measurement result shows a low relative intensity noise below -150 dB/Hz at 60 mA up to 6 GHz. We also report 20 and 10 Gbps data transmission at a bias current of 50 mA at 20 °C and 40 °C, respectively.

1300 nm Semiconductor Optical Amplifier Compatible With an InP Monolithic Active/Passive Integration Technology

In monolithic photonic integrated circuits (PICs), an optimized active/passive integration is needed to provide efficient coupling and low amount of interface reflections between amplifiers and passive components. A 1300 nm semiconductor optical amplifier (SOA) on InP substrate and optimized for butt-joint reflections is investigated. Material performance were assessed from measurements of broad area lasers. Room temperature operation reveals 1.2 W single facet output power with threshold current around 100 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> per well. Characteristic temperatures of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 75 K and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> = 294 K were obtained. A compact model description of the SOA, suitable for the design of PICs and rate equation analysis, was applied to parametrize the unsaturated gain measurements. Current injection efficiency of 0.65, transparency carrier density of 0.57 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> , and free carrier absorption losses up to 15 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> were extracted from fitting the data. The model is verified with measurements of optical gain saturation. A modal gain of 15 dB for a 600 μm long narrow ridge SOA leads to output saturation power higher than 30 mW at 7 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This building block contributes to the development of an InP monolithic integration technology in the 1300 nm range, which can enable the use of photonic integrated circuits in many kind of applications.

&gt;25 W pulses from 1.5 μm double‐asymmetric waveguide, 100 μm stripe laser diode with bulk active layer

The experimental characterization of a high-power pulsed semiconductor laser operating in the eye-safe spectral range (wavelength around 1.5 μm), with an asymmetric waveguide structure, a 100 μm wide stripe, and a bulk active layer positioned very close to the p-cladding, is reported. An anti-reflection/high reflection coated laser with a stripe width of 100 μm exhibits a single-facet output power over 25 W at a pumping current amplitude of 100 A.

Watt-level, high wall plug efficiency, continuous-wave room temperature quantum cascade laser emitting at 7.7µm.

In this article, a InP based strain-balanced In0.58Ga0.42As/In0.47Al0.53As quantum cascade laser emitting at 7.7µm is reported. The active region is based on a slightly-diagonal bound to continuum design with 50 cascade stages and a low voltage defect Δinj of 96 meV. By optimizing the active region and waveguide structure, the waveguide loss αw of 1.18cm-1 are obtained, which contribute to a high wall-plug efficiency (WPE) of 9.08% and low threshold current of only 1.09 kA/cm2 in continuous-wave(CW) operation at 293K. The maximum single facet output power of 1.17W in CW operation and 2.3W in pulsed operation are measured at 293K. The narrow ridge and buried ridge structure epi-side-down-mounted on the diamond heatsink improved the heat dissipation of the device. A beam of pure zero order mode and a broad external-cavity tuning range from 7.16µm to 8.16µm are also achieved.

Comparison of growth structures for continuous-wave electrically pumped 1.55 μm quantum dash lasers grown on (001) Si

Semiconductor lasers directly grown on silicon offer great potential as critical components in high-volume, low-cost integrated silicon photonics circuits. Although InAs/InP quantum dash (QDash) lasers on native InP substrate emitting at 1.5 μm (C-band) have demonstrated notable performance, the growth of InAs/InP QDash lasers on silicon remains undeveloped because of the 8% lattice mismatch between InP and silicon. Here we report advances of growth techniques leading to the first C-band room-temperature continuous-wave electrically pumped QDash lasers on CMOS standard (001) silicon substrates by metalorganic chemical vapor deposition. A correlation between various material characterizations and device performance is analyzed for different QDash laser structures grown on planar nominal (001) silicon. With the optimized QDash growth and improved fabrication process, the lowest threshold current density of 1.5 kA / cm 2 was determined on an 8 μm × 1.5 mm device on planar silicon with a single facet output power exceeding 14 mW. The device results illustrate the good material quality of the QDash lasers grown on silicon, suggesting potential applications for other active components of photonic integrated circuits, such as semiconductor optical amplifiers, modulators, and photodetectors.

Electrically pumped continuous-wave O-band quantum-dot superluminescent diode on silicon.

High-power, broadband quantum-dot (QD) superluminescent diodes (SLDs) are ideal light sources for optical coherence tomography (OCT) imaging systems but have previously mainly been fabricated on native GaAs- or InP-based substrates. Recently, significant progress has been made to emigrate QD SLDs from native substrates to silicon substrates. Here, we demonstrate electrically pumped continuous-wave InAs QD SLDs monolithically grown on silicon substrates with significantly improved performance thanks to the achievement of a low density of defects in the III-V epilayers. The fabricated narrow-ridge-waveguide device exhibits a maximum 3 dB bandwidth of 103 nm emission spectrum centered at the O-band together with a maximum single facet output power of 3.8 mW at room temperature. The silicon-based SLD has been assessed for application in an OCT system. Under optimized conditions, a predicted axial resolution of ∼5.3µm is achieved with a corresponding output power of 0.66 mW/facet.

Low Threshold Quantum Dot Lasers Directly Grown on Unpatterned Quasi-Nominal (001) Si

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 × 107 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.

Demonstration of Electrically Injected Semipolar Laser Diodes Grown on Low-Cost and Scalable Sapphire Substrates.

The last two decades have shown an increasing need for GaN-based laser diodes (LDs), which are currently only grown on bulk GaN substrates, which remain to date very expensive and/or only available in small sizes. The ever growing laser market will expand in the coming years, thanks to the development of automotive laser lighting, high-speed Li-Fi optical data transmission, LiDAR sensing for autonomous vehicles and smart cities, head-up displays, and AR/VR systems, in addition to biomedical and further industrial applications. These emerging technologies demand for mass-production of GaN-based lasers to be produced on large-size, low-cost, and industrially compatible substrates. To address this issue, we demonstrate the first electrically injected semipolar 440 nm LD on high-quality and low-defect-density (11-22) GaN templates grown on scalable and low-cost sapphire substrates. The LDs exhibit a threshold current density of 17 kA/cm2, a single facet output power of more than 200 mW at 2 A with a slope efficiency of 0.85 W/A, and a TE polarization having a ratio of 97.6%. These results enable the advancement of ultra-low-cost LDs while benefiting from the inherent advantages of semipolar GaN properties.

Origin of Defect Tolerance in InAs/GaAs Quantum Dot Lasers Grown on Silicon

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.

13 μm InAs/GaAs quantum dot lasers on silicon with GaInP upper cladding layers

We report on the first electrically pumped continuous-wave (CW) InAs/GaAs quantum dot (QD) laser grown on Si with a GaInP upper cladding layer. A QD laser structure with a Ga0.51In0.49P upper cladding layer and an Al0.53Ga0.47As lower cladding layer was directly grown on Si by metal–organic chemical vapor deposition. It demonstrates the postgrowth annealing effect on the QDs was relieved enough with the GaInP upper cladding layer grown at a low temperature of 550°C. Broad-stripe edge-emitting lasers with 2-mm cavity length and 15-μm stripe width were fabricated and characterized. Under CW operation, room-temperature lasing at ∼1.3 μm has been achieved with a threshold density of 737 A/cm2 and a single-facet output power of 21.8 mW.

Narrow-Linewidth Oxide-Confined Heterogeneously Integrated Si/III–V Semiconductor Lasers

We demonstrate a narrow-linewidth heterogeneously integrated Si/III–V laser, where the current confinement in the III–V structure is obtained by oxide isolation rather than by the prevailing ion-implantation technique. This method provides effective electrical isolation as well as III–V surface passivation, and a pathway for high-efficiency diode injection laser performance. This method also offers increased compatibility with potentially high-temperature annealing processes. The lasers shown here possess a threshold current of as low as 60 mA and a single-facet output power of more than 3 mW at 20 °C. A linewidth of 28 kHz at 1574.8 nm is obtained at a current of 200 mA ( $I = 3.3 \times I_{\mathrm{ th}}$ ). Single-mode operation is achieved with a side-mode suppression ratio larger than 55 dB.

Electrically pumped continuous-wave 1.3 µm InAs/GaAs quantum dot lasers monolithically grown on on-axis Si (001) substrates.

We report on the first electrically pumped continuous-wave (cw) InAs/GaAs quantum dot (QD) lasers monolithically grown on on-axis Si (001) substrates without any intermediate buffer layers. A 400 nm antiphase boundary (APB) free epitaxial GaAs film with a small root-mean-square (RMS) surface roughness of 0.86 nm was first deposited on a 300 mm standard industry-compatible on-axis Si (001) substrate by metal-organic chemical vapor deposition (MOCVD). The QD laser structure was then grown on this APB-free GaAs/Si (001) virtual substrate by molecular beam epitaxy (MBE). Room-temperature cw lasing at ~1.3 µm has been achieved with a threshold current density of 425 A/cm2 and single facet output power of 43 mW. Under pulsed operation, lasing operation up to 102 °C has been realized, with a threshold current density of 250 A/cm2 and single facet output power exceeding 130 mW at room temperature.

Electrically pumped continuous-wave 1.3 μm quantum-dot lasers epitaxially grown on on-axis (001) GaP/Si.

We demonstrate the first electrically pumped continuous-wave (CW) III-V semiconductor lasers epitaxially grown on on-axis (001) silicon substrates without offcut or germanium layers, using InAs/GaAs quantum dots as the active region and an intermediate GaP buffer between the silicon and device layers. Broad-area lasers with uncoated facets achieve room-temperature lasing with threshold current densities around 860 A/cm2 and 110 mW of single-facet output power for the same device. Ridge lasers designed for low threshold operations show maximum lasing temperatures up to 90°C and thresholds down to 30 mA.

Optically Pumped Continuously Tunable Mid-IR Distributed-Feedback Semiconductor Laser

An 80-nm continuous, mode-hop-free, wavelength tuning range centered at $3.1~\mu \text{m}$ has been demonstrated for a large area, optically pumped mid-infrared type-II semiconductor distributed feedback (DFB) laser with a spectral linewidth of 1.2 nm at $2.5\times $ threshold and 820 mW single-facet output power operated CW at 80 K, suitable for atmospheric pressure molecular spectroscopy and remote sensing. Wavelength tuning of this DFB laser is achieved by translating the optical pump stripe across the device patterned with a hyperbolically chirped, location-dependent-period grating. The impact of chirp along the gain stripe is clarified and optimized to allow continuous tuning.

A Buried Ridge Stripe Structure InGaAsP-Si Hybrid Laser

A buried ridge stripe (BRS) structure InGaAsP-Si hybrid laser based on selective area metal bonding (SAMB) method is demonstrated. This novel hybrid laser structure combines the SAMB method's advantage of low bonding requirements and great flexibility and the BRS lasers' low threshold, high thermal performance, and good optical field and carrier confinement. The 300-$\mu $ m-long hybrid laser has a threshold current of 14 mA and a maximum single-facet output power of 5.4 mW at room temperature, with a slope efficiency of 0.17 W/A. The laser has a characteristic temperature of 50 K, with continuous wave operation at temperature >50 °C.

Heterogeneously integrated III-V/silicon distributed feedback lasers

Heterogeneously integrated III-V-on-silicon second-order distributed feedback lasers utilizing an ultra-thin DVS-BCB die-to-wafer bonding process are reported. A novel DFB laser design exploiting high confinement in the active waveguide is demonstrated. A 14 mW single-facet output power coupled to a silicon waveguide, 50 dB side-mode suppression ratio and continuous wave operation up to 60°C around 1550 nm is obtained.