Hirohumi Kasada

Widegap II-VI compound optical modulators of ZnSe/ZnMgSSe asymmetric coupled quantum wells

We report on widegap II-VI compound short wavelength optical modulators of ZnSe/ZnMgSSe asymmetric coupled quantum wells (ACQWs). Effective mass approximated calculations have shown that ZnSe(50/spl Aring/)-ZnMgSSe(30/spl Aring/)-ZnSe(20/spl Aring/) ACQW exhibits weak Stark effect region (<40 kV/cm) and strong Stark effect region (>40 kV/cm). These simulations are experimentally confirmed by a p-i-n structure ACQW modulator grown by molecular beam epitaxy (MBE). The present device exhibits a low reverse bias operation (/spl sim/8 V) with modulation ratio(T/sub on//T/sub off/) of 1.08 at room temperature.

Deep defect center characteristics of wide-bandgap II-VI and III-V blue laser materials

Microscopic deep defect characteristics of the blue laser materials in the II-VI and III-V wide-bandgap semiconductors have been studied from the view point of the device performance and degradation. The deep defect centers, monitored by transient capacitance spectroscopy technique, have revealed quite different properties in electrical activity, defect density and carrier injection enhanced generation of the defects for the two different wide-bandgap blue laser materials.

Very high power line-selective CO2 laser with (line-selective) unstable resonator

By replacing the conventional (non line-selective) unstable resonator, we succeeded in developing the very high power line-selective (line-tunable) CO2 laser as a pumping source for high power molecular gas (e.g.NH3) lasers in the infrared and far-infrared regions.The experiments were performed by using the very high power CO2 laser (4A unit of Lekko VIII) at The Institute of Laser Engineering, Osaka University.The output power of 9R(30)9.22µ m line from the developed CO2 laser, for instance, exceeded 0.5GW/pulse (50J/pulse with pulse width of 100nsec).