Importance

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Abstract

This invention relates to a simple, compact, and robust, cylindrical microlens external cavity for laser diode frequency control. The microlens system makes possible a tunable laser diode that utilizes an orthogonal pair of collimating microlenses to form a short external cavity for longitudinal mode and frequency control. The resulting system generates a circular, collimated beam of single frequency, tunable laser radiation. A cylindrical microlens collimator has a powered surface that semi-collimates (i.e., collimates in one axis only) the light from a laser diode. This powered surface is placed so as to be the surface closest to the laser facet. A second lens surface opposite the powered surface, is located in the semi-collimated beam is planar. The second surface of the lens is flat and has a reflective coating. Hence, it provides feedback that is refocused (in one axis) onto the laser aperture. This leads to efficient light coupling back into the laser even if the reflectivity of the second surface is relatively low, and allows the use of lasers with only a single optical output. In another embodiment, a second microlens is used to circularize the beam from the first microlens and the pair of microlenses is mounted onto a translator so as provide frequency tuning of the laser diode.

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First Claim