Matsushita Electric Industrial Co., Ltd.

Yoshihiro Kino

Nobuaki Furuya

Hiroshi Miyama

Naoki Takenaka

Masaaki Ohshima

Noriyuki Hirayama

Mitsuru Asanuma

A semiconductor laser comprising in the direction parallel to a junction on both sides of a stripe-shaped active layer of double-hetero structure a semi-insulating current blocking layer which has a refractive index smaller than that of the active layer and of which the resistance is increased by doping of an impurity.

Semiconductor lasers

In a conventional surface acoustic wave ring filter, a time-compensation element in the form of a thin strip is additionally provided for either retarding or accelerating one of the surface acoustic waves which transmit along different transmission lines, thereby the phases of two surface acoustic waves received by a single output converter included in the filter are matched with each other resulting in the improvement in the output signal characteristics.

Surface acoustic wave filter

A ghost signal erasing system for television receivers in which a variable delay element utilizing the propagation of an elastic surface wave is used. The variable delay element includes a piezoelectric substrate, a plurality of first interdigitated electrode pairs formed on the substrate and a plurality of second interdigitated electrode pairs also formed on the substrate. An elastic surface wave produced by applying a video i-f signal to the first interdigitated electrode pairs is propagated along the surface of the piezoelectric substrate and taken up at the second interdigitated electrode pairs as a delayed a-c signal. By switching the first and second interdigitated electrode pairs to change the combination thereof, various delay times are obtained.

Ghost signal erasing system

A spinel-type oxide exhibiting a cooperative Jahn-Teller effect shows an extraordinary reduction of sound velocity therethrough at temperatures near the Jahn-Teller phase transition temperature thereof. The sound velocity and effective temperature range can be varied over wide ranges by using a solid solution of such an oxide and another spinel-type oxide not exhibiting the Jahn-Teller effect. NiCr.sub.2 O.sub.4 and ZnCr.sub.2 O.sub.4 are particularly advantageous as the former and latter oxides, respectively.

Growing community of inventors

Kawasaki, Japan

Yoshihiro Kino