Toshitami Hara

Asymmetric dual quantum well laser---wavelength switching controlled by injection current

We have performed the first experiment on a novel laser diode, the lasing wavelength of which can be switched with increasing current. Wavelength switching over 13 nm under continuous operation, as well as lasing at dual wavelengths, has been achieved for the first time.

Wide‐range wavelength tuning of an asymmetric dual quantum well laser with inhomogeneous current injection

A new asymmetric dual quantum well laser diode with a segmented contact is proposed. With inhomogeneous current injection, the lasing wavelength can be changed quasi‐continuously over 22 nm, which is much wider than any tuning range previously reported. To achieve such wide‐range tuning, it is found to be essential that the length of the cavity and each segment (and the mirror reflectivity) of the laser diode should be within an optimized range. In the asymmetric dual quantum well laser diode structure used in the present experiment, in particular, the cavity length should be such that light of a shorter wavelength lases under homogeneous excitation.

A self-consistent analysis of DH lasers over the gain-guiding and index-guiding regions

Ridge waveguide double heterostructure (DH) lasers are theoretically investigated over the gain-guiding and the index-guiding regions. To determine the lasing mode profiles, the spatial variations of the complex refractive index (the gain-guiding and the anti-index-guiding effects) caused by the distribution of injected carriers, as well as the index-guiding effect due to the ridge waveguide, are self-consistently taken into account. From the self-consistent results for the carrier distribution and the lasing mode profiles, various static properties such as the threshold current, lasing of higher lateral modes, and the astigmatism are obtained as functions of the distance between the active layer and the base of the ridge. The results show a gradual transition from the index-guiding to the gain-guiding regions, and the anti-index-guiding effect is found to play an important role in the latter region.

Coloration in a WO3 film

The electrical coloration in WO3 films in practical fabrication originates at the interface between WO3 and CaF2 and migrates towards the cathode. The rate of migration is higher than 1.4×10−9 cm2/V sec.