Yasuyuki Bessho

High-Power, 790 nm, Eight-Beam AlGaAs Laser Array with a Monitoring Photodiode

A high-power, 790 nm, eight-beam individually addressable AlGaAs laser array on 50 µm centers with a monitoring photodiode has been developed for high-speed data transfer in optical memory systems. The maximum output power of each element is over 80 mW. When eight elements are simultaneously operated at 20 mW in APC (Automatic Power Control) mode using the one-beam monitoring control, the total light output variation is less than 7% at a heatsink temperature between 10 and 50°C.

Fundamental transverse mode 100-mW semiconductor laser with high reliability

A 100 mW high-power AlGaAs laser with the current-blocking regions near the facets and a long cavity length has been developed. The length and the channel width of the current-blocking region, and cavity length were examined in order to obtain a high-output power. As a result, a stable fundamental transverse mode operation is obtained up to 180 mW, and maximum output power is 230 mW under CW operation. Stable operation under 100 mW of output power was confirmed for more than 2000 hours at 60 C.

High-Power Blue-Violet Laser Diode Fabricated on a GaN Substrate

We have successfully fabricated blue-violet laser diodes, consisting of nitride-based semiconductors, with both high-power and low-noise characteristics on GaN substrates. These laser diodes have a ridge waveguide structure with a dielectric current blocking layer. By improving the crystal quality of the grown materials and optimizing the optical confinement in the device, a kink level as high as 250 mW has been achieved. Optimized optical confinement is also assumed to result in far field patterns without any additional peaks. In addition to this, since the threading dislocation density at the active layer below the ridge portion is reduced to less than 105cm-2, these laser diodes have been operating reliably for more than 1000 h with a light output power of 100 mW at 60°C under pulsed operation. We have also confirmed that these laser diodes have a noise level as low as -130 dB/Hz, which meets the requirement for practical use, for a light output power of 5 mW. These laser diodes are expected to enable dual layer recording in nextgeneration, large-capacity optical disc systems using blue-violet laser diodes.

High-power blue-violet laser diodes for next-generation optical disc systems

High-power and low-noise characteristics are strongly required for blue-violet laser diodes in practical application to next generation optical disc systems. We have successfully fabricated blue-violet laser diodes meeting these requirements. These laser diodes have a ridge waveguide structure with a dielectric current blocking layer. Improving the crystal quality of the grown materials on a GaN substrate and optimizing the optical confinement in the emission layer have achieved a kink level as high as 250 mW. Optimized optical confinement is also assumed to result in a good beam profile with no fringe. In addition to this, since the threading dislocation density at the emission layer below the ridge portion is reduced to less than 10 5cm-2, these laser diodes have been operating reliably for more than 1000 h with a light output power of 100 mW at 60 °C under pulsed operation. This light output power makes it possible to realize dual layer recording systems. We have also confirmed that these laser diodes have a noise level as low as -130 dB/Hz for a light output power of 5 mW.

A smart model HD DVD/DVD/CD compatible pickup head

We have proposed a compatible pickup for HD DVD/DVD/CD systems, which uses a blue/red/IR multi beam laser unit and a single sensor unit. The optical path of the DVD system is aligned to that of the HD DVD system to share one sensor area. Experimental results confirm the practicality of the proposed pickup

Fundamental transverse-mode 150-mW semiconductor laser for an SHG light source

A highly reliable, 150 mW high-power semiconductor laser that oscillates at a wavelength of 860 nm has been developed. This device has a 0.7 jim thick p-cladding layer, a 900 jim long cavity length, and current-blocking regions near the cavity facets for high output power and high reliability. Stable, fundamental transverse mode and single longitudinal mode operation were obtained up to 230 mW, and the maximum output power was 350 mW under CW operation. Stable operation under 150 mW at 50°C was confirmed for more than 2000 hrs.

100 mW, Four-beam Individually Addressable Monolithic ALGaAs Laser-diode Arrays

Four-beam individually addressable monolithic AlGaAs laser-diode arrays have been developed in which each laser element can emit over 100 mW of output power in single-mode operation. The structural features of this laser include current-blocking regions near the facets and a long cavity length to obtain higher power, as well as a cBN heatsink and a 70 micrometers - thick laser chip to improve thermal crosstalk between laser elements. The maximum output power of each laser element is about 200 mW and the lasing wavelength is about 834 nm. Thermal crosstalk between 100 micrometers -spaced neighboring elements is only 1.0% at 100 mW.