InGaAsP/InP separated multiclad layer stripe geometry laser emitting at 1.5 µm wavelength

We have developed an InGaAsP/InP separated multiclad layer (SML) stripe geometry laser emitting at 1.5 μm wavelength. In this laser, the optical confinement is done by the effective refractive index step owing to the formation of the coupled waveguide outside the stripe region. The current confinement is done by the p-n-p-n structure outside the stripe region. The CW threshold current at 25 °C is only 82 mA for the stripe width and the cavity length of 6 μm and 250 μm, respectively. The maximum temperature where the CW lasing is obtained is 65°C. The characteristic temperature of the threshold current is 60 K. The transverse mode is fundamental up to 1.8 times the threshold. Ten samples are operated at 50°C with constant optical output of 5 mW/facet. These samples are still operating at over 10 000 h with a slight increase in the driving current. The appreciable change in the characteristics due to aging is not observed.     

InGaAsP/InP buried crescent laser diode emitting at 1.3 µm wavelength

The fabrication procedure, designing of an active region and a p-n-p-n current blocking structure, characteristics and the aging results of an InGaAsP/InP buried crescent (BC) laser diode are described. The BC laser diodes exhibit high laser performances, such as a low-threshold current, a fundamental transverse mode oscillation with linear light output-current characteristics. CW operation at as high as 100°C is achieved with a junction up configuration as a result of the improvement in the current blocking structure. A stable CW operation at 80°C has been realized with a constant optical output power of 5 mW.     

InGaAsP double-channel- planar-buried-heterostructure laser diode (DC-PBH LD) with effective current confinement

A new high-performance 1.3-μm InGaAsP semiconductor laser is described, in which effective current confinement into the active region has been realized. A p-n-p-n current blocking structure is made by liquid-phase epitaxy (LPE) on both sides of the active-stripe mesa which is defined by a pair of channels in the double-heterostructure wafer. The double-channel-planar-buried-heterostructure laser diodes (DC-PBH LD's) exhibit high-laser performances, such as a high differential quantum efficiency of 78-percent maximum, which results in high electrical to optical power conversion efficiency 43 percent, and high light output power of over 50 mW, as a result of the improvement in the current blocking structure. The threshold current temperature sensitivity is found experimentally to be reduced remarkably by increasing the doping concentration in the p-cladding layer. Characteristic temperature as high as 100 K has been obtained. CW operation is possible up to 130°C.     

Characteristics of diffused-stripe InP/InGaAsP/InP lasers emitting around 1.55 µm

Fabrication and lasing characteristics of InGaAsP/InP lasers emitting around 1.55 μm are described. Zn-diffused stripe-geometry lasers with emission wavelengths in the1.53-1.60mum range were fabricated from InP/InGaAsP/InP DH epitaxial wafers prepared by a low temperature LPE technique. The dependence of the lasing charaeteristics on the stripe width was examined. The lowest threshold current (≃160 mA under CW operation at 27°C) was obtained for a laser with a 13 μm stripe. CW operation of the laser has been achieved at a heat-sink temperature as high as 53°C. For sufficiently narrow stripe widths (simeq6 mum), fundamental-transverse mode and single-longitudinal mode operation was obtained under CW operation. Moreover, the lasers have good high-frequency performance. The lasers showed excellent dynamic properties without waveform distortion under high-frequency (800 Mbits/s) large-signal pulse modulation. The full width at half maximum of the longitudinal mode envelope was approximately 30 Å at 800 Mbits/s.     

High-performance single-longitudinal-mode operation of InGaAsP/InP DFB-DC-PBH LD's

The lasing performance of InGaAsP/InP distributed feedback laser diodes with double-channel planar buried heterostructure (DFB-DC-PBH LD's) is reported for end-titled and antireflection (AR) coated configuration. High-power CW single-longitudinal-mode (SLM) operation over 55-mW light output at room temperature, high-temperature CW SLM operation over 105°C, as well as stable SLM operation under 2-Gb/s high-speed direct modulation, have been attained for 1.3-μm band DFB-DC-PBH LD's. 1.5-μm band DFB-DC-PBH LD's have also exhibited excellent DFB lasing characteristics, such as high power over 20 mW and high temperature over 75°C CW SLM operation. DFB SLM yield in the laboratory was also examined for 1.3-μm DFB-DC-PBH LD's, giving rise to a good prospect for practical use in optical-fiber communication systems.     

V-grooved substrate buried heterostructure InGaAsP/InP laser emitting at 1.3 µm wavelength

Details of the fabrication, optimization of the dimensions of the active region, characteristics, and the aging results of theV- grooved substrate buried heterostructure (VSB) InGaAsP/InP laser are described. It is shown that the VSB laser can be fabricated in one-step epitaxy as well as two-step epitaxy. The active region width below 2.5 μm and the thickness of0.15-0.2 mum are shown to give stable fundamental mode operation and good temperature characteristics. The fundamental mode operation up to the optical output of 20 mW/facet at 25°C and the CW operation above 100°C are obtained. The pulse response showed the strongly damped relaxation oscillation with a frequency as high as 4.5 GHz. The spectral width under the modulation of 400 Mbit/s RZ single is as narrow as 25 Å in full width at half maximum. Highly stable aging characteristics at an elevated temperature of 50°C are obtained in both two-step epitaxy lasers and one-step epitaxy lasers.     

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.     

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.     

Fabrication and lasing properties of mesa substrate buried heterostructure GaInAsP/InP lasers at 1.3 µm wavelength

Fabrication and lasing properties of novel GaInAsP/InP injection lasers at 1.3 μm, with buried heterostructure grown on mesa substrate and fabricated by single-step crystal growth are reported. In this mesa substrate buried heterostructure (MSB) laser, the GaInAsP active layer was grown separately on the top of a mesa structure formed along the surface of a     

MOVPE-grown 1.5 µm distributed feedback lasers on corrugated InP substrates

A single-step low-pressure metalorganic vapor phase epitaxy (MOVPE) was applied to the fabrication of 1.5 μm InGaAsP/InP distributed feedback laser diodes on corrugated InP substrates, accompanied by LPE for buried heterostructure formation. High probability of single longitudinal mode operation was obtained due to the uniformity of the active layer thickness. A typical threshold current was 35 mA with both facets cleaved. A maximum output power of up to 27 mW was also obtained under single longitudinal mode operation with anti-reflective/cleaved facet configuration. The laser diode had high spectral stability under high-frequency direct modulation of 1.4 GHz. Results of initial aging tests (APC of 5 mW at 25°C for longer than 3800 h) have shown no degradation in driving currents. It is found that low-pressure MOVPE is favorable for epitaxial growth on corrugated substrates.     

A 0.2 W CW laser with buried twin-ridge substrate structure

An extremely high output power has been obtained with a new structure laser named the buried twin-ridge substrate (BTRS) laser. The very thin active layer formed on a ridged substrate permitted high power output increasing the catastrophic damage level. The buried stripe formed with a blocking layer remarkably improved the current confinement lowering the threshold current. A multilayer coating technique was applied to both facets to increase the front facet output. Fundamental transverse mode is achieved at more than 100 mW in CW with an uncoated laser while the maximum output power attained is as high as 200 mW in CW operation with a multicoated laser.     

Reliability in InGaAsP/InP buried heterostructure 1.3 µm lasers

A study was conducted of aging-induced Sn whisker growth at the surface of Au-Sn bonding solder layers around a laser chip, as well as metallurgical reactions, especially in p-side down lasers, at the interface of the solder and laser crystal just below the active layer. These phenomena cause electrical shorts in InGaAsP/InP laser diodes, which occur suddenly in devices operated for long periods without any previous symptoms having appeared in their aging characteristics. To completely eliminate such failures, a novel assembling method in which chips were mounted p-side up on semiinsulating SiC submounts using Pb-Sn solder, was applied to InGaAsP/InP buried heterostructure (BH) lasers emitting at 1.3 μm. BH lasers assembled by this method do not suffer any shorting failure even after 8000 h operation under 60°C and 5 mW/facet output conditions. The small degradation rates obtained, for example, 3 percent/kh (median) at 60°C, certify the reliability of these improved lasers. As long as the stripe width of the active layer was optimized to be in the range of1.5-2.5 mum necessary for obtaining kink-free light output versus current properties, no detrimental changes in laser characteristics, including transverse and longitudinal modes and dynamic output response, were observed in aged lasers. In this paper, the long-term degradation modes observed are presented, and possible causes are discussed.     

Spectral linewidth estimation of a 1.5 µm range InGaAsP/InP distributed feedback laser

Spectral linewidth of a 1.5 μm range distributed feedback buried heterostructure (DFB-BH) laser in CW operation is estimated theoretically and experimentally. Considering the equivalent mirror facet loss coefficient and the confinement factor in the active layer, etc., we modified the conventional formula for the spectral linewidth of single-mode semiconductor lasers and presented a formula for the linewidth of DFB lasers. Furthermore, power-dependent linewidth measurements of a 1.5 μm range InGaAsP/InP DFB-BH laser with a window region were carried out using Fabry-Perot interferometers. The linewidth was observed to increase linearly with inverse output power. The measured result was explained by the calculated result through the modified formula. The full width at half maximum was estimated to be 50 MHz at an output power of 1 mW.     

InGaAsP planar buried heterostructure laser diode (PBH-LD) with very low threshold current

Using a new LPE growth technique, an InGaAsP/InP planar buried heterostructure laser diode (PBH-LD) has been realised in 1.3 and 1.5 ?m wavelength regions. As a result of the effective carrier confinement, CW threshold currents as low as 8.5 mA and 13 mA have been obtained in 1.3 and 1.5 ?m PHB-LDs, respectively, at room temperature.     

Transverse mode control in InGaAsP/InP buried crescent diode lasers

Transverse mode stabilisation of InGaAsP/InP buried crescent laser diodes emitting at 1.3 ?m is described. Width and thickness of the active region have been reduced to stabilise the transverse mode. Operation up to 17 mW/facet in a stable transverse mode and threshold current as low as 12 mA in CW operation have been obtained.     

Low threshold current MOVPE grown GaInAs-Al(Ga)InAs separateconfinement heterostructure multiquantum well metal-clad ridge-waveguidelasers emitting at 1585 nm

GaInAs-Al(Ga)InAs separate confinement heterostructure (SCH) multiquantum-well (MQW) metal-clad ridge-waveguide (MCRW) laser diodes were successfully fabricated for the first time from layer structures grown by atmospheric pressure (AP) metalorganic vapor-phase epitaxy (MOVPE) on InP substrate without any use of phosphine. CW operation of 2.9-μm-wide and 400-μm-long MCRW laser diodes emitting at 1585 nm was demonstrated with a minimum threshold current of 38 mA     

高频大功率InGaAsP/InP SPB-BC激光器

在普通掩埋新月型激光器的基础上,提出了一种高频大功率的InGaAsP/InP激光器结构——选择性质子轰击掩埋新月型(SPB-BC),并对激光器结构模型进行了理论分析。采用p-InP衬底,最大输出功率为80mW。500μm腔长激光器,它的调制带宽可以达到6.0GHz。     

Low threshold InGaAsP/InP buried crescent laser with double current confinement structure

An InGaAsP/InP laser diode emitting at 1.3 μm with a crescent shaped active region is described. The active region is completely embedded in InP by a two-step LPE technique, and a double current confinement scheme is incorporated with two reverse biased p-n junctions at both sides of the active layer. A threshold current as low as 20 mA has been achieved in CW operation at room temperature. Fundamental transverse mode operation with linear light output-current characteristics and single longitudinal mode oscillation have been obtained.     

Low-threshold current density InGaAsP/InP injection lasers with three-layer-waveguide double heterostructure (jth?0.5 kA/cm2 at 300 K)

Double heterostructure InGaAsP/InP lasers with a three-layer waveguide (or `separate-confinement? DH) have been prepared by the LPE method with a thin active layer. A decrease in threshold current density has been observed up to 512 A/cm2 in a four-sided cleaved diode at room temperature. CW operation of broad-area diodes is obtained in the pumping current range up to 2.5 A. Calculations of threshold current density for these laser structures are presented.     

Embedded-stripe GaAs-GaAlAs double-heterostructure lasers with polycrystalline GaAsP layers--I: Lasers with cleaved mirrors

We report a new type of embedded stripe laser in which low-order mode CW oscillation is successfully attained at room temperature. In order to achieve lateral current confinement, a high-resistivity polycrystalline GaAsP layer is formed around the mesa stripe by selective vapor-phase growth technology. It turns out that a stable single-mode operation is attained at an injected current up to several times the threshold value.