Taiji Morimoto

High output power characteristics in broad‐channeled substrate inner stripe lasers

A high output power AlGaAs laser is newly developed in the spectral range of 770–780 nm. The laser has a double‐depth channel on the p‐GaAs substrate which forms a built‐in optical waveguide having a double effective refractive index/loss step. This novel waveguide is effective to make the fundamental lateral mode extremely stable; that is, up to 60 mW when the reflectivity of the front facet (Rf) is 0.12, and 100 mW when Rf is 0.04. cw threshold currents are 35–45 mA and external differential efficiencies are 0.6–0.8 mW/mA. Also, an astigmatic distance below 3 μm is obtained when Rf is more than 0.10.

Improvement of high-power characteristics of 780-nm AlGaAs laser diode by (NH4)2S facet treatment

Coherent cw operation has been obtained with a 10x4 array of Grating Surface Emitting (GSE) lasers consisting of 40 lasers and 50 emitting sections. The array is a GaAs quantum well device, grown on an A1GaAs substrate, operating at 861 nm to which the substrate is transparent. It is mounted p-down to metallized traces on a BeO slab to provide isolated electrical contacts and thermal contact to a simple chilled-water cooler. A single spectral line 0.5 A wide indicates coupling of the 40 laser sections. More detailed measurements on a section of an array containing ten laterally coupled lasers, 20 outputs, show that it is operating at a junction temperature of 30°C, has a line width of 0.1 5A, and a measured coherence of >75%. The expected wavelength stabilization with temperature due to the DBR grating is found, with a value of =0.6A/°C. An array of 4 longitudinally coupled lasers produced a line width of 130MHz and evidence of high coherence.

High-Power CW Operation in V-Channeled Substrate Inner-Stripe Lasers with “Torch”-Shaped Waveguide

High-power AlGaAs lasers with a waveguide pattern like a torch have been grown by a two-step liquid-phase epitaxy process. The waveguide pattern consists of a 6 µm-wide region about 220 µm long and a 10 µ-wide region about 20 µm long connected by a tapered region about 10 µm long. A stable fundamental transverse mode has been obtained of up to more than 200 mW output power in a 4%–95% coated device in the wavelength range of 830 nm. The lasers have extremely high reliability, and stable continuous operation for over 4000 hours has been confirmed at 50°C, 50 mW with no obvious degradation.

Stable single-longitudinal-mode operation in visible (AlGa)As semiconductor lasers coupled with a short external cavity

High stability of single longitudinal mode has been achieved in visible wavelength regions using V‐channeled substrate inner‐stripe lasers coupled with a short external cavity. The temperature dependence of the coupled‐gain peak coincided entirely with that of one longitudinal mode for lasers with external‐cavity lengths of 50–60 μm. As a result, a wide longitudinal‐mode locking range of 31 °C was obtained over 8 mW. This result is in good agreement with the theoretical calculation, in which the effect of the thermal expansion of the external‐cavity length is taken into account.