Toshiya Fukuhisa

Low-noise 650-nm-band AlGaInP visible laser diodes with a highly doped saturable absorbing layer

Stable self-sustained pulsating and low-noise 650-nm-band AlGaInP visible laser diodes were demonstrated by adopting a novel structure, which has a highly doped saturable absorbing (SA) layer. Short carrier lifetime, which is indispensable for self-pulsation, was realized by applying high doping concentration to the p-type SA layer. 500-/spl mu/m-long devices with 51%/51% coated facets were fabricated, resulting in the threshold current of 75 mA at 20/spl deg/C. The temporal output power was measured at the average output power of 5 mW and the stable self-pulsation was observed up to an ambient temperature of 60/spl deg/C. Therefore, the relative intensity noise (RIN) was kept about -140 dB/Hz in temperature ranging from 20/spl deg/C to 60/spl deg/C. Since the refractive index difference could be kept large and the optical mode could be confined effectively, the astigmatism in this work was below 3 /spl mu/m at 5 mW against dc injection current. The lasers operated over 1350 h under the average output power of 5 mW at 60/spl deg/C.

Stable operation of self‐sustained pulsation in 650‐nm‐band AlGaInP visible lasers with highly doped saturable absorbing layer

Self‐sustained pulsating 650‐nm‐band AlGaInP visible lasers were fabricated by adopting a new structure, which has a highly doped saturable absorbing (HDSA) layer. Since the doping level and the thickness of the HDSA layer could be controlled accurately by using metalorganic vapor phase epitaxy growth technique, a stable operation of self‐sustained pulsation up to 60 °C was obtained. The lasers operated over 1350 h under the average output power of 5 mW at 60 °C. The relative intensity noise values were below −136 dB/Hz in the temperature ranging from 20–60 °C and remained unchanged after life test.

Monolithically Integrated Dual-Wavelength Self-Sustained Pulsating Laser Diodes with Real Refractive Index Guided Self-Aligned Structure

Monolithically integrated 780-nm-band and 650-nm-band self-sustained pulsating (SSP) lasers, which are desirable for simplified optical pickups in digital versatile disk (DVD) systems, have been developed for the first time. The real refractive index guided self-aligned (RISA) waveguide structure is adapted to reduce absorption loss in the current blocking layers. In order to obtain stable SSP, a saturable absorber formed in the active layer outside the current stripe, and a saturable absorbing layer above the active layer are utilized for the 780-nm-band and 650-nm-band laser diodes (LDs), respectively. Relative intensity noise less than -130 dB/Hz is maintained at temperatures of up to 80°C at an output power of 7 mW for the 650 nm band and 10 mW for the 780 nm band, which suggests that stable SSP operations have been realized.

Monolithically integrated 780-nm-band high-power and 650-nm-band laser diodes with real refractive index guided self-aligned structure

780-nm-band high-power and 650-nm-band laser diodes (LDs) with real refractive index guided self-aligned (RISA) structures are monolithically integrated for the first time. High-power and fundamental transverse mode operation at an output power of 100-mW continuous wave (CW) up to 80/spl deg/C is attained for the 780-nm-band LD. For the 650-nm-band LD, high temperature and fundamental transverse mode operation at an output power of 10-mW CW up to 80/spl deg/C is obtained.

High-Power 650-nm-Band AlGaInP Visible Laser Diodes Fabricated by Reactive Ion Beam Etching Using Cl2/N2 Mixture.

High-power 650-nm-band AlGaInP visible laser diodes having stable fundamental-transverse-mode at high temperatures were produced using electron cyclotron resonance reactive ion beam etching (ECR-RIBE). Epilayers were etched using a Cl2/N2 mixture gas, resulting in very smooth surfaces and symmetric laser mesas. Lasers that are 700-µm-long and 6%/80% coated were fabricated. The typical threshold current of these devices was as low as 46 mA at room temperature, and a stable fundamental-mode operation over 30 mW is obtained up to 70°C. The lasers operated for over 1000 h at 60°C under an output power of 25 mW, and their degradation rate was as low as lasers fabricated by the ordinary wet etching process.

Reduction of Aspect Ratio in 650 nm-Band Self-Sustained-Pulsing Lasers with Saturable-Absorbing Layer

650 nm-band self-pulsing lasers which exhibit an extremely low laser beam profile aspect ratio (2.6) and a small astigmatism (2 µm) were successfully demonstrated by optimizing the design of the layer structure. Low-noise self-pulsing lasers have been developed as a light source for optical disc systems. In the case of mounting the lasers on optical systems, a low aspect ratio and a small astigmatism are required in order to realize high optical coupling efficiency and good optical focusing characteristics. In this paper, we report a reduction of the aspect ratio while maintaining a small astigmatism in self-pulsing AlGaInP lasers with a saturable absorbing (SA) layer by optimizing the optical confinement and compressive strain in the SA layer. Simultaneously, a very low intensity noise characteristic up to 50° C was confirmed by stable self-sustained pulsation characteristics.

High-power red lasers for DVD-RAM drives

High-power (greater than 50 mW) and high-temperature (greater than 70 degrees Celsius) operation of 650 nm-band AlGaInP lasers are required as light sources for high-density and recordable optical disk memory systems. However, there remains the problems such as small band-offset in the conduction band and facet degradation in AlGaInP material system which limit the high-power and high-temperature operation. This paper presents new techniques in order to achieve such high performance lasers: Window-mirror structure and real index guided structure.

Low operating current and high temperature operation of 650 nm AlGaInP high power laser diodes with real refractive index guided self-aligned structure

Low operating current and high temperature operation has been achieved in 650 nm AlGaInP high power double quantum well laser diodes with a real refractive index guided self-aligned (RISA) structure. The attained operating current for 50 mW CW at 70/spl deg/C is as low as 98 mA, which is almost a half of the lowest value ever reported.