Etsuji Omura

High-efficiency and high-power laser diodes for CD-R/RW and DVD-RAM/RW

As light sources of CD-R/RW and DVD-RAM/RW, highly efficient high-power 785 nm (AlGaAs) and 660 nm (AlGaInP) lasers are demonstrated, respectively. A real-refractive-index waveguide with small internal loss is applied to both the lasers in order to reduce the operating current by improvement of the external differential quantum efficiency. The mirror degradation level is increased by reduction of the optical power density and/or a non-optical-absorbing effect of the window-mirror. As a result, the 785 nm window- mirror with AlGaAs current blocking layer has showed stable transverse mode operation up to 250 mW (kink level: over 300 mW at CW) with the high slope efficiency of 1.1 W/A. Reliable 140 mW-CW and 180 mW-pulse operation has been realized at 70 - 75 degree(s)C. As for a 660 nm laser with the window-mirror, the operation current at 70 mW is reduced by 40% due to the high slope efficiency (1.08 W/A) resulting from the low-loss ridge-waveguide. The lateral mode is well stabilized up to 70 mW by the effect of the narrow ridge stripe formed by a dry etching technique. Reliable 70 degree(s)C, 70 mW pulse (duty cycle: 50%) operation with a low operating current of around 120 - 140 mA has been achieved. In addition, the lasers have operated for over 1000 hours even at 70 degree(s)C, 80 mW.

High-power TQW AlGaAs laser with new inner-stripe structure

An approach to mass-production of triple quantum well lasers with a buried-ridge, loss-guided inner-stripe structure is demonstrated, using a large-scale metalorganic chemical vapor deposition. The lasers obtained from nine epi-wafers grown at one time show the uniform characteristics. In regard to high-power characteristics, the fundamental transverse mode up to 100mW and the maximum output power of - 170mW are realized at room temperature. Even at 95 C, the light output power of 100mW is obtained. The lasers have been operating over 1000 hours without failure at 6O C, 50mW. To realize the further uniformity and reproducibility of the laser characteristics, we have Introduced a newly developed etching method with an etching stop layer in the ridge formation.

Highly reliable 1.3 μm AlGaInAs FP lasers with low power penalty under uncooled 10Gbps operation at 85°C

We have realized highly reliable 1.3 μ m AlGaInAs FP lasers with low power penalty of 1.4dB at 10Gbps and 85°C. The MTTF was estimated over 1.5×105 hours and no deterioration of COD level was observed during the life test.

High-coupled-power 0.98-μm narrow-beam laser diodes

Kink-free, high coupled power of 148 mW into a single mode fiber has been realized by narrowing the vertical beam divergence in 0.98 micrometers laser diodes. It has been found that the high-refractive index GaAs layers have crucial influence on the far field patterns as well as lasing spectrum, since the GaAs is transparent to the emission wavelength of 0.98 micrometers .

Wavelength tunable 4-element laser array

A wavelength tunable 4-element laser array is fabricated with high performances suitable for the frequency division multiplexing (FDM) system. The array consists of four 1 .55 j.m DFB(distributed feedback) PPIBH (p-substrate partially inverted buried heterostructure) lasers with beam spacing of 125 jim. The lasing wavelength is tuned by changing the ratio of input currents to the two electrodes. The lasing frequency of the array can be allocated with a frequency interval of 10 GHz. An FM efficiency as large as 1 GHz/mA and a flat FM response with variation less than 3 dB in the modulation frequency range from 20 kHz to 1 GHz have been realized. An electrical crosstalk is less than -30 dB up to 800 MHz.

Low threshold current coplanar vertical injection laser diode for optoelectronic integrated circuits

A low threshold coplanar vertical injection laser diode (CPVI-LD) has been newly developed utilizing impurityinduced disordering of a single quantum well. The threshold current as low as 13 mA has been realized in CW operation. The behavior of Si and Zn solid phase diffusion is precisely investigated for the realization of the CPVJ-LD.

Recent progress of 10Gb/s laser diodes for metropolitan area networks

We have proved that short cavity length and large optical feedback structure can improve the relaxation oscillation frequency (fr) of 1.3mm directly modulated LDs for 10Gb/s operation. By this improvement, 1.3mm InGaAsP l/4 phase shifted distributed-feedback LDs (l/4 DFB-LDs) and 1.3mm AlGaInAs Fabry-Perot (FP)-LDs successfully revealed excellent transmission with small power penalty of 0.6dB at 70 oC for +40ps/nm wavelength dispersion and 1.5dB at 85oC for +10ps/nm one, respectively. It has been also proved that 1.55mm electro-absorption modulator integrated with DFB-LDs (EAM DFB-LDs) with MQW absorption layers are more suitable for 100km transmission than those with bulk ones, which originates from the difference of extinction curves. Transmission characteristics using 100km SMF of 1.55mm EAM DFB-LD with an MQW absorption layer has been realized with power penalty of 1.3dB. These devices can cover all optical lines of various distances in metropolitan area networks.

High-power and highly reliable operation of all-MOCVD-grown 1.48-um diode lasers

High output power and long-term stable operation have been realized in all-MOCVD grown 1.48 micrometers buried heterostructure lasers. For the purpose of high power operation, a diode with a cavity length of 1800 micrometers was mounted junction down. This diode shows the maximum output power of 310 mW at 25 degree(s)C, cw. A preliminary aging test is being carried on at a temperature of 50 degree(s)C with a constant light output of 100 mW for the diodes with cavity length of 900 micrometers and junction up configuration. Long-term stable operation over 3000 hrs and the estimated MTTF of 2.4 X 105 hrs at 50 degree(s)C, 100 mW have been realized. As another advantage of the all-MOCVD process, the uniformity of the laser characteristics is also demonstrated. Lasers with a cavity length of 900 micrometers in junction-up configuration are assembled from a processed 2-inch wafer.

A long-wavelength InGaAs/AlGaInAs MQW laser fabricated by Zn-diffusion induced disordering

The authors have fabricated a long-wavelength InGaAs/AlGaInAs MQW (multiple quantum well) laser in which optical confinement and carrier confinement are produced by disordering of the MQW. Pulsed oscillation at room temperature has been attained in this disordered system. It is believed that the lattice matched disordering of the InGaAs/AlGaInAs MQW structure is a promising technique for realizing a long-wavelength planar-type laser structure and other optoelectronic devices such as OEICs (optoelectronic integrated circuits).<<ETX>>

Long-wavelength lasers and detectors fabricated on InP/GaAs superheteroepitaxial wafer

InGaAsP laser diodes and InGaAs photodiodes grown on GaAs substrates have been reviewed. The laser diodes exhibit low threshold current of 31 mA and high slope efficiency of 0.2 W/A which are comparable with the diodes grown on InP substrates. The InGaAs photodiodes also show the comparable characteristics with the photodiodes grown on InP substrates. A GaAs MESFET and an InGaAs photodiode have been monolithically integrated. This receiver OEIC has sensitivity of -28.1 dBm at transmission rate of 622 Mb/s with a bit error rate of 10-9.