Masahiro Kume

Picosecond blue light pulse generation by frequency doubling of a gain‐switched GaAlAs laser diode with saturable absorbers

Picosecond blue light pulse generation by frequency doubling of a gain‐switched GaAlAs laser diode in a proton‐exchanged MgO:LiNbO3 waveguide is reported. High‐peak fundamental pulse power of 1.23 W is obtained by employing a laser diode with saturable absorbers. Blue light pulse of 7.88 mW maximum peak power and 28.7 ps pulse width is generated in the form of Cherenkov radiation.

Low operating current self‐sustained pulsation GaAlAs laser diodes with a real refractive index guided structure

We have developed a new real refractive index guided GaAlAs laser which satisfies both low operating current and low noise characteristics by self‐sustained pulsation. The structure has a planar active layer and a GaAlAs optical confinement layer which give large saturable absorber, and small internal loss. As a result, as operating current as low as 19.7 mA at an output power of 3 mW is obtained under self‐sustained pulsation, leading to a relative intensity noise level less than −135 dB/Hz.

Continuous room‐temperature operation of a 759‐nm GaAlAs distributed feedback laser

The first continuous wave (cw) operation at room temperature of a GaAlAs short‐wavelength distributed feedback (DFB) laser is reported. The cw operation at a wavelength of 759 nm was realized by use of the buried twin‐ridge substrate (BTRS) structure which has an excellent current confinement efficiency in the active region. The hybrid liquid phase epitaxy and the metalorganic chemical vapor deposition growth technology were used for the fabrication of short‐wavelength GaAlAs DFBu2009BTRS lasers.

Monolithic high‐power dual‐wavelength GaAlAs laser array

Monolithic integration of high‐power GaAlAs lasers is demonstrated. The new dual‐wavelength laser array is implemented by integrating a twin‐ridge substrate laser and a terraced substrate laser by the one‐step liquid phase epitaxy technique. Both lasers integrated on a GaAs chip continuously operated at the power output as high as (30+30) mW in single longitudinal modes with a wavelength separation of 31 nm.

High power single mode operation of long cavity GaAlAs lasers with nonabsorbing mirror buried twin ridge substrate structure

We have newly developed a 350 μm long cavity GaAlAs laser with nonabsorbing mirror buried twin ridge substrate structure, in order to obtain highly reliable high power single mode operation. It is found that the long cavity stabilizes lateral mode at powers higher than conventional maximum values because the carrier density is reduced to well suppress spatial hole‐burning effect. The fundamental spatial mode operation is confirmed up to 210 mW and the maximum output power as high as 380 mW is obtained. The lifetime at 100 and 200 mW at 25u2009°C are expected to be 170u2009000 and 24u2009000 h, respectively, from the aging test results.

Reduction of feedback‐induced noise by high‐reflectivity facet coating in single longitudinal mode semiconductor lasers

The feedback‐induced noise in single longitudinal mode semiconductor lasers is suppressed over a wide range of feedback light intensity by high‐reflectivity facet coatings. A relative intensity noise value was as low as −140 dB/Hz under 1% optical feedback in the GaAlAs lasers with high‐reflective (0.75) facets.

High-power GaAlAs single-element lasers with nonabsorbing mirrors

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.