High performance of 1.55-μm buried-heterostructurevertical-cavity surface-emitting lasers

We report a record low threshold current of 1.55-μm vertical-cavity surface-emitting laser (VCSEL). Thin-film wafer-fusion technology enables InP-based buried heterostructure VCSELs to be fabricated on GaAs-AlAs distributed Bragg reflectors. Threshold current density is independent of mesa size, and a 5-μm VCSEL exhibits a threshold current as low as 380 μA at 20°C and a single transverse mode up to the maximum optical output power under continuous-wave operation     

Multi-oxide layer structure for single-mode operation invertical-cavity surface-emitting lasers

We propose a novel vertical-cavity surface emitting laser (VCSEL) with Al(Ga)As multi-oxide layer (MOX) structure for the purpose of enlarging window aperture maintaining single transverse mode operation. We have fabricated an InGaAs-GaAs VCSEL with the proposed MOX structure formed on GaAs (311)B substrate. We have performed a numerical simulation to investigate single-mode behavior of the proposed structure and showed a possibility of single-mode VCSEL's with a large active area. We have fabricated an 11-μm current aperture 960-nm wavelength VCSEL with this MOX structure. The threshold current and voltage were 1.0 mA and 2.0 V, respectively, which are comparable to those of conventional oxide VCSELs. In 8-μm aperture, single-mode operation was maintained with a driving current up to four times the threshold     

GaAs/AlGaAs multiple quantum well GRIN-SCH vertical cavity surfaceemitting laser diodes

Vertical cavity surface emitting lasers (VCSELs) with GaAs/AlGaAs multiple quantum well (20 wells) graded-index separate-confinement-heterostructure (GRIN-SCH) active regions are discussed. The VCSEL structures, which also contained two Al_xGa_1-xAs/Al_yGa_1-yAs distributed Bragg reflectors, were grown by molecular beam epitaxy and had a threshold current and current density at room temperature pulsed excitation of 16 mA and 14 kA/cm², respectively, near 0.85-μm wavelength. Both single-longitudinal and fundamental transverse mode emission characteristics were observed with a light output greater than 3 mW and a slope efficiency of 0.12 mW/mA     

1.15-μm wavelength oxide-confined quantum-dot vertical-cavitysurface-emitting laser

Low-threshold lasing is achieved at 1.154 μm for an oxide-confined quantum-dot (QD) vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs substrate. The long wavelength emission is obtained through use of an InAs-GaAs QD active region. A continuous-wave (CW) threshold of 502 μA is obtained for a device size of 10-μm diameter, corresponding to a threshold current density of 640 A/cm²      

Thermal impedance of VCSELs with AlOx-GaAs DBRs

The authors have measured the thermal impedance of vertical-cavity surface-emitting lasers (VCSELs) with oxide/GaAs DBRs and shown that it is comparable to that of VCSELs with all-semiconductor DBRs. A VCSEL with an 8-μm oxide aperture shows a thermal impedance of 2.8°C/mW. By varying the aperture size, the thermal conductance of the material below the active area is 0.255 W/cm°C. These results demonstrate that the oxide is not a major barrier to heat transport out of the active region     

Long-wavelength (1.55-μm) vertical-cavity lasers withInGaAsP/InP-GaAs/AlAs DBR's by wafer fusion

We propose a novel design for a 1.55-μm vertical-cavity surface-emitting laser (VCSEL) structure employing double InGaAsP/InP-GaAs/AlAs distributed Bragg reflectors. The fundamental features of InP/GaAs wafer fusion are examined as a function of load pressure. We demonstrate an exact 1.55-μm emission wavelength in the CW mode with low threshold voltage (2.1 V) and low threshold current density (1.8 kA/cm²)     

Low resistance intracavity-contacted oxide-aperture VCSELs

The authors study, analytically and experimentally, the extrinsic series resistance in intracavity-contacted vertical-cavity surface-emitting lasers (VCSEL's). Low resistance, low threshold-current, intracavity-contacted VCSELs are fabricated, with resistances ranging from 355 Ω for 4-μm square apertures to 80 Ω for 12-μm square apertures and threshold voltages as low as 1.35 V. To the best of our knowledge, these are the lowest values reported for this type of VCSEL. The threshold currents range from 270 μA for 4 μm×4 μm apertures to 850 μA for 12 ×12 μm. From a comparison of the resistance as a function of oxide aperture radius, the measured data follows closely with the calculated data, demonstrating the validity of the derived expressions for series resistance     

长波长垂直腔面发射激光器

给出了长波长垂直腔面发射激光器的器件结构的发展现状，同时对GaInNAs／GaAs垂直腔面发射激光器进行了详细的介绍。最后，给出了所设计的新型1.3μm GaInNAs/GaAs长波长垂直外腔面发射半导体激光器的结构设计，有源区量子阱由980nm半导体激光二极管进行泵浦。这种器件设计实现了激光二极管泵浦与长波长垂直腔面发射激光器的有机结合，同时具有两者的优点。此外，本文还对器件的阈值特性和光输出功率进行了理论计算。     

MOVPE growth of a monolithic VCSEL at 1.56 μm in theInGaAlAs-InAlAs system lattice matched to InP

The first demonstration of a one-step-growth vertical-cavity surface-emitting laser (VCSEL) at 1.56 μm by low-pressure metal-organic vapor phase epitaxy in the InGaAlAs (λ_gap=1.43 μm)-InAlAs system lattice matched to InP is presented. The VCSEL's threshold current density was 7.5 kA/cm² and pulsed lasing had been obtained up to +55°C for 45-μm diameter proton implanted devices. This material system represents a high potential for continuous-wave VCSELs at 1.55-μm wavelength using a simple approach for large-scale industrial production     

Mesa-size dependence characteristics of vertical surface-emitting lasers

The vertical-cavity surface-emitting laser (VCSEL) is the most suitable light source for many optoelectronic applications because of its planar nature. The design of large VCSEL arrays requires accurate modeling of device characteristics. In this paper, we present a thermal model to analyze the dependence of VCSEL threshold current and light-output characteristics on aperture size. For both 850-nm and 980-nm VCSELs, a linear dependence of threshold current on device area is observed for oxidized aperture sizes with diameters between 5 μm and 25 μm. Good agreement between theoretical and experimental light-output characteristics is observed using a simple thermal model.     

Near-ideal I-V characteristics of GaInP/GaAsheterojunction bipolar transistors

GaInP/GaAs heterojunction bipolar transistors (HBTs) have been fabricated and these devices exhibit near-ideal I-V characteristics with very small magnitudes of the base-emitter junction space-charge recombination current. Measured current gains in both 6-μm×6-μm and 100-μm×100-μm devices remain constant for five decades of collector current and are greater than unity at ultrasmall current densities on the order of 1×10^-6 A/cm². For the 6-μm×6-μm device, the current gain reaches a high value of 190 at higher current levels. These device characteristics are also compared to published data of an abrupt AlGaAs/GaAs HBT having a base layer with similar doping level and thickness     

Single-mode power dependence on surface relief size formode-stabilized oxide-confined vertical-cavity surface-emitting lasers

We have studied the mode behavior of oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with a surface relief for fundamental mode selection. The dependence of single-mode power on the surface relief diameter was measured and compared with numerically calculated values. VCSELs with diameters of 9 and 12 μm were equipped with surface reliefs with diameters in the range 4-10 μm. The results show that there exists an optimum relief diameter for each VCSEL size. A maximum single-mode power of 2.2 mW was achieved for a 9-μm-diameter VCSEL with a 4-μm-diameter surface relief     

Direct coupling of VCSELs to plastic optical fibers using guideholes patterned in a thick photoresist

In this letter, we report a simple passive alignment method to couple plastic optical fibers (POFs) to vertical-cavity surface-emitting lasers (VCSELs) for use in parallel optical interconnects. Polymer guide holes were fabricated directly on the top of VCSELs by means of standard photolithography using SU-8 epoxy-based thick photoresist. Perfluorinated graded-index POFs were inserted and fixed in the guide holes to provide butt-coupled packaging modules. For a VCSEL of 15-μm diameter and a POF of 124-μm core diameter, coupling efficiencies were obtained between about 80% and 50%, depending on drive current. The standard deviation of the efficiency at a drive current of 10 mA was 5.9% for a 1 × 5 array     

Single transverse mode operation of 1.55-μm buriedheterostructure vertical-cavity surface-emitting lasers

In this letter, we report the single-mode operation of 1.55-μm buried heterostructure vertical-cavity surface-emitting lasers (VCSELs) fabricated on a GaAs-AlAs distributed Bragg reflector using thin-film wafer fusion. A 7-μm VCSEL exhibits a single transverse mode at up to about 0.1-mW maximum optical output power and 75°C maximum operation temperature under continuous-wave operation     

AlGaAs vertical-cavity surface-emitting laser responses to 4.5-MeV proton irradiation

We have irradiated single- and multimode AlGaAs vertical-cavity surface-emitting laser (VCSEL) arrays operating at a nominal wavelength of 780 nm with 4.5-MeV protons and doses ranging from 10 to 30 Mrad in the active region. We observed a peak power reduction of about 2% per Mrad in the 14-/spl mu/m aperture, multimode VCSELs. Single-mode VCSELs having an aperture of 6 /spl mu/m exhibited a smaller peak power reduction of 0.4%-1% per Mrad. A slight shift in the current threshold was observed only for the multimode VCSELs at dose levels above 10 Mrad. First results indicate a reduced VCSEL peak laser power output that is dominated by a temperature shift caused by the radiation induced increase in resistive heating. In contrast, the power reduction in edge-emitting lasers is dominated by the enhanced radiation induced nonradiative recombination rate. The VCSEL irradiation was performed with a focused ion micro beam that was rastered over the device surface, ensuring a very uniform exposure of a single device in the array.     

Self-aligned InGaP/GaAs heterojunction bipolar transistors formicrowave power application

As an alternative to AlGaAs/GaAs heterojunction bipolar transistors (HBTs) for microwave applications, InGaP/GaAs HBTs with carbon-doped base layers grown by metal organic molecular beam epitaxy (MOMBE) with excellent DC, RF, and microwave performance are demonstrated. As previously reported, with a 700-Å-thick base layer (135-Ω/sq sheet resistance), a DC current gain of 25, and cutoff frequency and maximum frequency of oscillation above 70 GHz were measured for a 2-μm×5-μm emitter area device. A device with 12 cells, each consisting of a 2-μm×15-μm emitter area device for a total emitter area of 360 μm², was power tested at 4 GHz under continuous-wave (CW) bias condition. The device delivered 0.6-W output power with 13-dB linear gain and a power-added efficiency of 50%     

Design and characterization of In0.2Ga0.8AsMQW vertical-cavity surface-emitting lasers

The device design, material characterization, and performance of optimized vertical-cavity surface-emitting lasers (VCSELs) are presented. The basic design goal was to increase the output power of the lasers without greatly increasing the low threshold current reported in earlier devices. The material characterization was performed by measuring in-plane lasers and broad-area VCSELs made from the same material as the small VCSELs. For 10-μm-square devices, outputs over 3 mW, device operation over 100°C, 6% wall-plug efficiency, threshold voltages under 3 V, and threshold currents under mA are reported     

Efficient single-mode oxide-confined GaAs VCSEL's emitting in the850-nm wavelength regime

Single- and multimode vertical-cavity surface-emitting lasers (VCSELs) with three unstrained GaAs quantum wells (QWs) and emission wavelengths around 850 nm have been fabricated using molecular beam epitaxy (MBE) for crystal growth. Wet chemical etching and subsequent selective oxidation are applied for current confinement. The influence of oxide layer position on lateral index guiding is studied in detail in order to increase maximum single-mode output power. A device of 3-μm active diameter and reduced index guiding shows maximum single-mode output power of 2.25 mW with a side-mode suppression ratio (SMSR) of more than 30 dB for high-efficiency oxidized VCSELs     

Electrical characteristics of proton-implanted vertical-cavitysurface-emitting lasers

The electrical characteristics of proton-implanted GaAs quantum-well vertical-cavity surface-emitting semiconductor lasers (VCSELs) have been studied. We show that the 2 kT current, observed over many decades in these VCSELs, is primarily due to nonradiative recombination mechanisms. These include surface recombination at the edges of the proton-implanted region and bulk recombination at defects and heterojunction interface traps. The contribution of these mechanisms to the total nonradiative current and the threshold current density has been calculated. Lateral spontaneous emission measurements have been used to prove that the radiative current has a kT behavior in the subthreshold region. Electrical derivative measurements have been used to identify leakage current paths through the proton-implanted region in the low-bias regions. In addition, electrical derivative measurements have been used to measure the variation of series resistance with current near the lasing threshold. From a consideration of the various current paths in the VCSEL, a lumped circuit equivalent model for the VCSEL has been developed     

Low threshold current 1.3-/spl mu/m GaInNAs VCSELs grown by MOVPE

The structure of the conventional contact 1.3-/spl mu/m GaInNAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) was optimized and low threshold current 1.3-/spl mu/m GaInNAs VCSELs grown by metal-organic vapor-phase epitaxy were reported. The idea is to optimize the active region, the doping profiles, and the pairs of p-distributed Bragg reflectors, and the detuning between the emission wavelength and the photoluminescence gain peak wavelength. The continuous-wave 1.0-mA threshold current was achieved for the single-mode VCSEL. For the multiple-mode VCSELs, the below 2-mA threshold currents at 5/spl deg/C-85/spl deg/C , the 1.13-mA threshold current at 55/spl deg/C, and 1.52-mA threshold current at 85/spl deg/C are the best results for 1.3-/spl mu/m GaInNAs VCSELs.