CW room-temperature visible single quantum well Ga0.73Al0.27As diode lasers grown by metalorganic chemical vapour deposition

Room-temperature CW laser operation at 7125 ? has been achieved in a (Ga1?xAlxAs, x?0.27) single quantum well double heterostructure (SQW-DH) diode laser. The laser consists of a 9 ?m-wide delineated shallow proton stripe. The pulsed threshold current for a 250 ?m long device is 115 mA whereas the CW threshold current is 140 mA. The CW external differential quantum efficiency is 60%.     

650 nm GalnP/AlGaInP laser diodes with low threshold and compressively strained MQW active layer

650 nm AIGalnP/GalnP laser diodes with compressively strained MQW active layer have been successfully fabricated by means of single epitaxy growth. The threshold current is 6.4 mA,at 40 mA CW operation, the fundamental transverse-mode still remains, and the output power and the slope efficiency can reach 34 mW and 1.1 mW/mA respectively. The dead output power in CW operation can reach 66 mW at a saturation current of 88 mA. During 200 h burn in test,the laser diodes show good stabilization with a degradation of less than 8 %.     

A Four‐Channel Laser Array with Four 10 Gbps Monolithic EAMs Each Integrated with a DBR Laser

A distributed Bragg reflector (DBR) laser and a high speed electroabsorption modulator (EAM) are integrated on the basis of the selective area growth technique. The typical threshold current is 4 to 6 mA, and the side mode suppression ratio is over 40 dB with single mode operation at 1550 nm. The DBR laser exhibits 2.5 to 3.3 mW fiber output power at a laser gain current of 100 mA, and a modulator bias voltage of 0 V. The 3 dB bandwidth is 13 GHz. A 10 Gbps non‐return to zero operation with 12 dB extinction ratio is obtained. A four‐channel laser array with 100 GHz wavelength spacing was fabricated and its operation at the designed wavelength was confirmed.     

Fabrication of InGaAsP Double Shallow Ridge Rectangular Ring Laser With Total Internal Reflection Mirror by Cascade Etching Technique

InGaAsP double shallow ridge rectangular ring laser photonics integration circuits have been successfully fabricated by cascade etching technique. Varied thresholds with coupling current I_c and coupling length L_c are observed. The lowest threshold current of 75 mA, including I_c and I_d, at I_c = 30 mA in the device of L_c = 300 mum is obtained. The device of L_c = 200 mum exhibits single-mode operation with sidemode suppression ratio = 15 dB and Q = 6513 just beyond the threshold. The cascade etching technique is of interest for fabrication of other multilayer monolithic photonic integration circuits.     

复增益耦合型取样光栅DFB激光器的设计制作与性能

A complex-coupled DFB Laser with sampled grating has been designed and fabricated. The key concepts of the approach are to utilize the +1st order reflection of the sampled grating for laser single mode operation, and use a conventional holographic exposure combined with the usual photolithography to fabricate the sampled grating. The typical threshold current of the sampled grating based DFB laser is 25mA, and the optical output is about 10mW at the injected current of 100mA. The lasing wavelength of the device is 1.5385μm, which is the +1st order wavelength of the sampled grating.     

Asymmetric sampled grating laser array for a multiwavelength WDM source

We propose a multiwavelength laser array associated with asymmetric sampled grating lasers. The laser was designed to operate at the first-order reflection of a sampled grating with the aid of an index shifter. A four-channel laser array with 400-GHz wavelength spacing was fabricated and its operation at designed wavelengths was confirmed. Individual lasers showed a threshold current of 11-17 mA and slope efficiency of around 0.18 W/A. A high side-mode suppression ratio over 39 dB was observed as well.     

Double quantum wire GaAs/AlGaAs diode lasers grown byorganometallic chemical vapor deposition on grooved substrates

Structure and lasing characteristics of double-quantum-wire lasers are reported. Threshold current as low as 2.4 mA and continuous wave operation at room temperature were achieved for lasers with uncoated facets. Subbands due to lateral quantum confinement were observed in the laser spectra. Good agreement between measured dependence of threshold current on cavity length and a simple model accounting for gain saturation was found     

Design and performance of a complex-coupled DFB laser with sampled grating

A complex-coupled DFB laser with sampled grating has been designed and fabricated. The method uses the + 1 st order reflection of the sampled grating for laser single-mode operation. The typical threshold current of the sampled grating based DFB laser is 25 mA, and the optical output is about 10 mW at the injected current of 100 mA. The lasing wavelength of the device is 1.5385μm, which is the +1 st order wavelength of the sampled grating.     

A high-voltage hollow-cathode Au-II 282-nm laser

Laser operation on the Au-II 282.3-nm line is obtained from a high-voltage, segmented hollow-cathode discharge tube with external mirrors. Measurements of the laser output power and the small-signal gain demonstrate that, for a given total discharge current, the optimum performance of the laser is obtained for a discharge length for which the linear current density is approximately 65 mA cm^-1. The gain is approximately 2546 m^-1 at this current density and increases with current density up to the highest value used (250 mA cm ^-1), at which the gain exceeds 50% m^-1. The threshold current decreases monotonically, with decreasing length, the lowest observed value being 6.28 A for a length of 5 cm. A quasi-CW output power of 20 mW is obtained for a gain length of 20 cm and a discharge current of 3.2 A in a partially optimized tube with unoptimized output coupling     

1.5 µm range InGaAsP/InP distributed feedback lasers

Lasing characteristics of InGaAsP/InP distributed feedback (DFB) lasers in the 1.5 μm range were studied theoretically and experimentally. Wave propagation in five-layer DFB waveguides were analyzed to estimate the effect of the structural parameters on threshold conditions. A brief consideration on designing a low threshold laser and its lasing wavelength was made. DFB buried heterostructure lasers with fundamental grating emitting at 1.53 μm were prepared by liquid phase epitaxial techniques. CW operation was confirmed in the temperature rangeof -20° to 58°C, and a CW threshold current was as low as 50 mA at room temperature. A stable single longitudinal mode operation was observed both in dc condition and in modulated condition by a pseudorandom pulse current at 500 Mbits/s. No significant increase in the threshold current was observed after 1400 h continuous CW operation at 20°C.     

Continuous-wave operation of lateral current injectionmultiquantum-well laser

Continuous-wave operation of an AlGaAs/GaAs lateral current injection multiquantum-well laser at room temperatures has been achieved by improving the structure and fabrication process. The laser has exhibited a threshold current of 47 mA and a differential quantum efficiency of 11%     

Long-wavelength multiple-quantum-well voltage-controlled bistablelaser diodes

We have investigated static and dynamic characteristics of a multiple-quantum-well (MQW) voltage-controlled bistable laser diode at 1.5 μm. Using the quantum confined Stark effect, the absorption coefficient and the absorption band edge of the saturable absorption region are controlled by applied voltage, resulting in easy change of the hysteresis width and the threshold current. Applied voltage from below the current injection regime to the saturable absorption region, typically the reverse bias voltage, allows faster turn-off switching speed due to the carrier sweep-out by the applied electric field, MQW bistable lasers with InGaAs-InP, InGaAs-InGaAsP and InGaAs-InAlAs systems and several kinds of well numbers were fabricated and their threshold current and switching characteristics are compared. A hysteresis width change of about 20 mA was obtained by changing the applied voltage of about 1 V in each case, Less than 100 ps turn-on switching time with injection light of 1-mW peak intensity was obtained. The device can be switched-on by injection light with about 50 nm bandwidth, and the minimum input light switching intensity of less than 10 μW is achieved around the absorption peak wavelength of the saturable absorber. The InGaAs-InAIAs system has the advantage of low voltage bias at the saturable absorber, because the absorption edge is sharper than other materials due to its high conduction band offset. It has a turn-off switching time of less than 100 ps at the applied voltage height of 2.0 V. And also, memory operation with the repetition rate of 2 GHz has been achieved using input light and the applied voltage     

Effect of source and load resistance on the performance of bistablelasers

The effect of source and load resistances on the bistable behavior of multiquantum-well laser diodes is studied. Lower values of source resistance are found to affect the threshold current with a slight change in the hysterisis width. Also, the turn ON delay is found to decrease exponentially with the increase in source resistance. Lower values of load resistance leads to smaller hysterisis width, and for values less than 125 Ω, for the device under study with an input resistance (R_in) of 1 kΩ, an astable behavior is observed when triggered by an electrical pulse in the gain section     

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     

High efficiency InGaAs/GaAs single-quantum-well lasers usingsingle-step metalorganic chemical vapor deposition

Low-threshold-current single-quantum-well InGaAs/GaAs lasers are fabricated by metalorganic chemical vapor deposition on a nonplanar substrate. By taking advantage of the growth rate and doping differences on different crystal facets during the growth, a buried heterostructure laser with natural current blocking p-n-p-n junction is formed by a single growth step. Threshold currents as low as 1.0 mA under pulsed operation and 1.2 mA under continuous-wave operation are obtained for uncoated lasers at room-temperature. The lasers showed high external quantum efficiency (80%) and high T₀ (150 K). High reflection coated laser (95%/95%) have CW threshold current as low as 0.28 mA     

Large CW power, very-low-threshold, single transverse modeoperation of vertical cavity mushroom structure surface emitting lasers

Summary form only given. Continuous-wave GaAs mushroom structure surface emitting laser (MSEL) operation at a threshold current as low as 1.6 mA, an output power >2.0 mW, and a single transverse mode up to three times threshold current is reported. The relatively large CW output power was achieved by reducing the series resistance using a selective zinc diffusion. The low threshold current and single-mode operation are attributed to good lateral current confinement in a small constricted region formed by mesa undercutting. The complete device was mounted junction-side up on a chip carrier and tested CW at room temperature. Some results are given     

Very large bandwidth strained MQW DFB laser at 1.3 μm

A 3-dB bandwidth of 20 GHz has been demonstrated for a compressively strained multiquantum well InGaAsP-InP DPB laser operating at 1.3 μm. The laser displayed superior static performance including very low threshold current (~8 mA), high external quantum efficiency (0.44 mW/mA), high CW output power (>60 mW) and high temperature operation     

Continuous-wave operation of terahertz quantum-cascade lasers

We report continuous-wave (CW) operation of a 4.4-THz quantum-cascade laser grown in the GaAs-AlGaAs materials system by molecular beam epitaxy. The device operates at 4 K with a threshold current of 160 mA, and an output power of /spl sim/25 /spl mu/W. In pulsed mode, the maximum operating temperature is 52 K, with a threshold current of 108 mA at 4 K. CW lasing was achieved by using a small cavity ridge area (60/spl times/600 /spl mu/m), and by coating one of the laser facets. These two features allowed for a substantial decrease of the threshold current and therefore reduced detrimental heating effects. The role played by the lateral resistance of the 800-nm GaAs layer underneath the active region was also investigated. Experimental data is presented showing that the temperature of the active region, which eventually hinders CW lasing, can be substantially influenced by the value of this lateral resistance.     

Low threshold operation of 1.5-µm DFB laser diodes

Highly reliable distributed feedback (DFB) laser diodes operating at 1.5-μm wavelength range are fabricated through optimizing the device parameters. Thickness control of the active layer is found to be an essential factor in achieving low threshold operation of DFB lasers. The threshold current as low as 11 mA and stable single longitudinal mode CW operation up to 106°C is achieved with these DFB lasers.     

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