High output power and high temperature operation of 1.5 μmDFB-PPIBH laser diodes

Highly efficient 1.5-μm distributed-feedback (DFB) p-substrate partially-inverted buried heterostructure laser diodes with a thin active layer developed using a metal-organic chemical vapor deposition technique are discussed. An average slope efficiency of 0.26 mW/mA (quantum efficiency 33%) and maximum slope efficiency of 0.39 mW MW/mA (49%) were achieved. The full width at half maximum in the direction perpendicular to the junction plane of 25° was obtained. A high output power of 77 mW was obtained under CW conditions at room temperature. This laser diode lased up to 120°C, and more than 10 mW was obtained, even at 90°C     

Low-noise 650-nm-band AlGaInP visible laser diodes with a highlydoped saturable absorbing layer

Stable self-sustained pulsating and low-noise 650-nm-band AlGaInP visible laser diodes were demonstrated by adopting a novel structure, which has a highly doped saturable absorbing (SA) layer. Short carrier lifetime, which is indispensable for self-pulsation, was realized by applying high doping concentration to the p-type SA layer. 500-μm-long devices with 51%/51% coated facets were fabricated, resulting in the threshold current of 75 mA at 20°C. The temporal output power was measured at the average output power of 5 mW and the stable self-pulsation was observed up to an ambient temperature of 60°C. Therefore, the relative intensity noise (RIN) was kept about -140 dB/Hz in temperature ranging from 20°C to 60°C. Since the refractive index difference could be kept large and the optical mode could be confined effectively, the astigmatism in this work was below 3 μm at 5 mW against dc injection current. The lasers operated over 1350 h under the average output power of 5 mW at 60°C     

Room-temperature, continuous-wave operation for mode-stabilisedAlGaInP visible-light semiconductor laser with a multiquantum-wellactive layer

646 nm continuous-wave operation at room temperature (25°C) has been achieved by a transverse mode stabilised AlGaInP laser diode with a (multi-)quantum-well structure. The laser structure was grown by metalorganic vapour phase epitaxy. The threshold current (density) is 55 mA (4.4 kA/cm²) and maximum light output power is 19 mW. Stable fundamental transverse-mode operation was obtained, at least up to 15 mW     

2.05-μm wavelength InGaAs-InGaAs distributed-feedbackmultiquantum-well lasers with 10-mW output power

Single-mode operation beyond 2.05-μm wavelength has been achieved in InGaAs-InGaAs distributed-feedback (DFB) laser with four quantum wells. The continuous-wave output power is 10.5 mW at a drive current of 200 mA and 25°C, The tuning range of the wavelength is between 2.051-2.056 μm with a temperature tuning rate of +0.125 nm/°C     

Very low threshold operation of 1.52 μm GaInAsP/InP DFB buriedridge structure laser diodes entirely grown by MOCVD

1.52 μm GaInAsP/InP DFB laser diodes with a buried ridge structure were fabricated entirely by MOCVD, with a second-order corrugation on the GaInAsP guiding layer. The 5 mA minimum threshold current achieved is believed to be the lowest yet reported for DFB lasers. Single longitudinal-mode operation with a side-mode suppression ratio greater than 35 dB was obtained from 20°C (up to 16 mW) to 90°C (up to 3 mW)     

Low threshold 650 nm band real refractive index-guided AlGaInPlaser diodes with strain-compensated MQW active layer

650 nm band real refractive index-guided AlGaInP laser diodes with a strain-compensated MQW active layer have been successfully fabricated. A threshold current of 9 mA, which is the lowest ever reported was achieved and 5 mW operation was obtained up to 120°C. These lasers have been operated for >3000 h under 5 mW at 90°C     

High-temperature CW operation of planar buried-ridge structurelasers at λ=1.5 μm

GaInAsP/InP-PBRS lasers emitting at 1.5 μm have been fabricated by multiple liquid-phase epitaxy. Effective current confinement is achieved without current blocking layers. CW threshold current is as low as 9 mA at 25°C. Output powers per facet of up to 10 mW at 80°C and 3.5 mW at 100°C are obtained. The maximum operation temperature of 110°C is the highest value yet achieved with this type of laser at 1°5 μm     

High-performance 670-nm AlGaInP/GaInP visible strained quantum welllasers

We have grown high-performance AlGaInP/GaInP visible (670 mn) strained quantum well lasers by low-pressure metalorganic chemical vapor deposition. With AlInP cladding layer, a high-power AlGaInP/GaInP visible laser diode is achieved. Its threshold current is about 30 mA. The output power of this laser diode can maintain, at least, at 32 mW under continuous-wave (CW) operation at room temperature. High slope efficiency (0.8 mW/mA) and differential quantum efficiency (0.87) can be achieved. To improve beam quality, AlGaInP/GaInP visible lasers with and without depressed index cladding layer are theoretically and experimentally studied. From experimental results, the transverse beam divergence can be reduced from 41.4° to 26.2° while maintaining a low threshold current (from 36 mA to 46 mA). By using the transfer matrix method, our theoretical calculations are in good agreement with the experimental results     

50 mW CW-operated single-mode surface-emitting AlGaAs lasers with45° total reflection mirrors

The authors report on the fabrication and testing of surface-emitting AlGaAs 3.5 μm ridge lasers with etched mirrors and 45° internal deflectors. The 45° mirror coupling coefficient and the resulting threshold current penalty have been analyzed theoretically and experimentally. A surface-emitted optical power of 50 mW CW at 26 mA threshold current and external differential efficiency of 57% has been achieved in lateral fundamental-mode operation. The optical power density of 14 mW CW per micrometer ridge width is the highest reported to date and produces two-dimensional surface-emitting laser arrays of diffraction-limited beam quality suitable for optical storage applications     

Native-oxidized InAlAs blocking layer buried heterostructureInGaAsP-InP MQW laser for high-temperature operation

A novel idea of InAlAs native oxide utilized to replace the p-n-p-n thyristor blocking layer and improve the high-temperature performance of the buried heterostructure first proposed and demonstrated. A temperature (To) of 50 K is achieved from an InAlAs native oxide buried heterostructure (NOBH) InGaAsP-InP multiquantum-well laser with 1.5-μm-wide diode leakage passage path. The threshold current and slope efficiency of NOBH laser changes from 5.6 mA, 0.23 mW/mA to 28 mA, 0.11 mW/mA with the operating temperature changing from 20°C to 100°C. It is comparable to conventional p-n reverse biased junction BH laser with minimized diode leakage current, and is much better than the buried ridge strip with proton implanted laterally confinement laser     

Dry-etched 650 nm AlGaInP visible-light laser diodes with operatingtime of over 3000 h

The authors have achieved CW operation of 650 nm GaInP/AlGaInP index waveguide-type visible-light laser diodes (LDs) with dry-etched mesa stripes fabricated by Cl₂ reactive ion beam etching. The threshold current of 47 mA and slope efficiency of 0.40 W/A are almost the same as those of a wet-etched LD fabricated from the same wafer (L=500 μm). The cross-sectional scanning electron microscope view of the buried mesa stripe shows that the dry-etched LD has a symmetric mesa shape resulting in a small focusing spot and stable mode operation. The wet-etched mesa, however, is asymmetric because a 6° misoriented substrate is used for this wavelength operation. An aging test with light output power of 3 mW at 50°C has revealed that these LDs have an operating time of over 3000 h, which represents a sufficient reliability for conventional uses     

InGaAs-GaAs-InGaP distributed feedback buried heterostructurestrained quantum-well lasers for high-power operation at 0.98 μm

Data are presented on device results from InGaAs-GaAs distributed feedback buried heterostructure (DFB BH) strained-quantum-well lasers with InGaP cladding layers. DFB BH lasers with a p-n InGaP current blocking junction entirely grown by a three-step MOVPE on GaAs substrates show a low laser threshold of 3.2 mA and a high output power of 41 mW with single-longitudinal-mode operation, both measured CW at RT. The monomode oscillation is obtained even at the injection current of 140 mA (44 times the laser threshold) with the side-mode suppression ratio of 35 dB and the temperature sensitivity of Bragg modes being 0.5 Å/°C measured between 20 and 40°C     

Demonstration of saturation spectra of caesium D/sub 2/line with a low linewidth distributed feedback laser diode

Low linewidths for Al-free active region distributed feedback lasers using a self-heterodyne measurement method (minimum beat width of 0.8 MHz at 20 mW and 12 C, 1.2 MHz at 852.12 nm 35 mW and 36 C) are demonstrated. Singlemode emission was achieved at 852.12 nm corresponding to the D₂ caesium transition, with an optical output power of 35 mW at 140 mA under CW operation. Finally, the saturation spectra of caesium atoms with the DFB laser diode was recorded with a resolution close to the natural linewidth.     

High reliability of AlGaInP LED's with efficient transparentcontacts for spatially uniform light emission

The indium-tin oxide (ITO) films with low sheet resistance and conducting transparency have been used on the AlGaInP double-heterostructure orange light-emitting diodes (LED's) to improve the light extraction from the LED surface and device reliability. The orange LED's with ITO films exhibit a light output power of 1 mW at 50 mA, which corresponds to an external quantum efficiency of 1.1%. They can operate stably for more than 3000 h at 20 mA and 25°C without any degradation     

2-μm GaInSb-AlGaAsSb distributed-feedback lasers

Room temperature continuous-wave operation of 2-μm single-mode InGaSb-AlGaAsSb distributed-feedback (DFB) lasers has been realized. The laser structure has been grown by solid source molecular beam epitaxy (MBE). Single-mode DFB emission is obtained by first-order Cr-Bragg gratings on both sides of the laser ridge. For a cavity with 900 μm length and 4 μm width, the threshold currents are around 20 mA and the continuous-wave output power is 10 mW at a drive current of 200 mA at 20°C. Monomode emission with sidemode suppression ratios of 31 dB has been obtained     

InP/InGaAsP p-type substrate and mass transported doubly buried heterostructure laser

A novel InP/InGaAsP buried heterostructure laser diode on p-type InP substrate has been developed. The laser has achieved a threshold current as low as 20 mA DC with high power output of 50 mW under CW operation in the fundamental transverse mode.     

Temperature-dependent characteristics and single-mode performanceof AlGaInP-based 670-690-nm vertical-cavity surface-emitting lasers

We report on temperature dependent characteristics and single mode performance of one-wave cavity, planar implanted, AlGaInP-based vertical-cavity surface emitting lasers. By optimizing the overlap between the gain peak and the cavity mode of the structure, we demonstrate record device performance, including 8.2 mW maximum output power and 11% power conversion efficiency for multimode operation and 1.9 mW and 9.6% power conversion efficiency for single mode operation at 687 nm. Improved performance at elevated temperatures is also achieved, with 1.5 mW output power demonstrated at 50°C from a 15-μm-diameter device     

All MOCVD grown 850-nm-wavelength refractive-index-guidedsemiconductor-buried vertical-cavity surface-emitting lasers withp/n-InGaP current blocking layers

All metal-organic chemical vapor deposition (MOCVD) grown 850-nm-wavelength refractive-index-guided semiconductor-buried vertical-cavity surface-emitting laser is proposed and their performance is investigated. P/n-InGaP current-blocking region enables both selective regrowth and the formation of refractive-index-guided region which surrounds multiquantum-well active/core regions. We have achieved room temperature CW operation of the new types of vertical-cavity surface-emitting lasers. The minimum threshold current was 9.5 mA with 18 μm square mesa size at 30°C. The device lased at up to 70°C, and the maximum output power exceeds 1 mW at above 30°C. The near field pattern indicates the single-lobed output beam at low bias current     

Extremely high power 1.48 μm GaInAsP/InP GRIN-SCH strained MQWlasers

A record CW output power of 360 mW at 25°C was achieved by investigating the structure of optical confinement layer in 1.48 μm GRIN-SCH MQW lasers. It is experimentally demonstrated that the use of a wide bandgap and thin SCH layer gives a high differential quantum efficiency without expense of threshold current. Low driving currents, 195 mA for 100 mW, 450 mA for 200 mW and 890 mA for 300 mW, were obtained in the optimized cavity lengths     

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