Semiconductor laser apparatus with isolator.

摘要

A laser diode (2) is mounted on a block (101) forming part of a base structure (1). The diode is hermetically sealed within a cap (3) provided with a window (4) for the emission of light. The p-n junction plane of the laser diode (2) is parallel to the vertical surface on which it is mounted and light is emitted through an end surface of the diode in a direction normal to the window (4). In order to prevent return light from disturbing the diode and creating noise, the window (4) is formed of magneto-optical material which is magnetically saturated by an external annular magnet (5). The thickness of the window (4) is such that the plane of polarization of the emitted light is rotated 45 DEG by Faraday rotation. A further 45 DEG rotation is imposed on any returning light so that there is a 90 DEG rotation relative to the plane in which the laser diode (2) is active. In other embodiment the magneto-optical material is deposited on the inside of a glass window or on the end surface of the diode.