Hiroki Naito

Low-Noise and High-Power GaAlAs Laser Diodes with a New Real Refractive Index Guided Structure

We demonstrate for the first time a real refractive index guided GaAlAs laser structure that has both very low-noise characteristics at a low output power (reading mode) and a stable fundamental transverse mode up to a high power level (writing mode) sufficient for optical read-write systems. The low-noise characteristics are realized by self-sustained pulsation which is induced by large saturable absorbers outside a stripe, and the high power is achieved by using a thin active layer which confines the optical flux very loosely. In order to optimize the device parameters, numerical simulation of the structure is proposed with consideration of interaction between optical field and carrier diffusion under gain nonlinearity and carrier diffusion taken into account. The calculated results are verified experimentally. The lasers showed relative intensity noise level less than -135 dB/Hz under 0-20% optical feedback and output power higher than 60 mW.

Two-dimensional analysis of self-sustained pulsation for narrow-stripe AlGaAs lasers

Self-sustained pulsation in narrow stripe geometry AlGaAs laser diodes is investigated numerically and experimentally. By taking account of the time-dependent two-dimensional optical field, carrier spreading in the cladding layers, and multilongitudinal modes, we succeeded in clarifying the mechanism for the pulsation. Fluctuation of the optical field plays an important role in forming saturable absorption. The numerical analysis clearly shows that our newly proposed real refractive index-guided structure is very suitable for a pulsation laser in which the optical field distribution and current spreading can be independently controlled. Furthermore, me show that the new structure gives much lower threshold current than that of a conventional loss-guided structure. These predicted advantages of the real refractive index-guided structure are verified experimentally with good agreement. >

800 mW peak-power self-sustained pulsation GaAlAs laser diodes

We have developed a high-power self-sustained pulsation laser by using a multiple-quantum-well real refractive index guided self-aligned (RISA) structure that allows formation of large saturable absorbers outside a stripe region. As a result, a peak power as high as 800 mW was obtained in the laser with the stripe width of 1.0 /spl mu/m. >

A high-power short-pulse laser diode for waveguide second harmonic generation

Abstract This paper describes successful development of a high-power short-pulse i.r. laser diode, together with numerical analyses giving a clear understanding of the operation. The novel aspect of the present laser diode is that a saturable absorber is incorporated for gain switching into the buried-twin-ridge substrate (BTRS) structure which allows a high-stability fundamental spatial mode operation. Peak powers as high as 1.23 W and pulse widths as narrow as 34.1 ps have been obtained in an efficient gain-switching operation with the high mode stability. The experimental observations are well-explicable by the numerical analyses in substantial respects. We also report picosecond-pulse blue-light generation which has been attained by applying the frequency doubling technique to the above laser in a LiNbO3 waveguide.

Multi-longitudinal-mode two-dimensional analysis of self-sustained pulsating laser diodes

Summary form only given. The structural dependence of self-sustained pulsation in AlGaAs laser diodes is quantitively analyzed for the first time, with the incorporation of the two-dimensional distribution of carriers and photons into the multi-longitudinal-mode rate equations.

800 mW peak power self-sustained pulsation GaAlAs laser diodes

We have developed a self-sustained pulsation laser whose peak power is as high as 0.8 W for the first time, by using a new multiple-quantum-well (MQW) real refractive index guided structure with large saturable absorber.

Power independent degradation of high power GaAlAs lasers with nonabsorbing-mirrors

The reliability of high-power single-mode GaAlAs lasers with nonabsorbing mirrors was investigated in detail. The lasers were tested at various output powers and temperatures. The results indicate that the degradation of the lasers is depen- dent not on the output power, but only on the operating current and temperature. The thermal activation energy of the degra- dation rate is estimated to be 0.85 eV, from which the lifetime under 100 mW operation at 25°C is expected to exceed 100 000 h.