US 5,636,059 AGranted

Cylindrical microlens external cavity for laser diode frequency control

AssigneeBlue Sky Research

InventorJames J. Snyder

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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.

Claims4

Dependent claims

A tunable laser comprising:

a laser diode having an optic axis and first and second axes orthogonal to said optic axis, wherein radiation from said laser diode expands more quickly along said first axis than along said second axis;
a microlens assembly comprising:
a first cylindrical microlens configured for collimating radiation emitted by said laser diode on said first axis, said first cylindrical microlens having a Iongitudinal axis along said second axis, wherein said first cylindrical microlens has a first optical surface and a second optical surface opposite said first optical surface, wherein said first optical surface is convex and is oriented for receiving radiation from said laser diode and wherein said second optical surface is flat and is oriented for receiving radiation from said first optical surface, said second optical surface for reflecting a portion of the radiation from said laser diode back through said first surface along said optic axis toward said laser diode;
a second cylindrical microlens spaced apart from said first microlens, orthogonal thereto, and configured for circularizing radiation incident from said first microlens;
a holder for holding said first cylindrical microlens and said second cylindrical microlens in said spaced apart arrangement to accomplish said circularization by said second microlens;
a translation element coupled to said laser diode and to said microlens assembly such that said microlens assembly can be translated along the optic axis relative to said laser diode, thereby changing the frequency of radiation emitted by said laser diode.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/386,312Filed 8 Feb 1995
Granted: 3 Jun 1997
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

H01S 5/14
Construction or shape of the optical resonator , e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or…:…
G02B 3/06
With non-spherical faces: with cylindrical or toric faces
G02B 6/4206
The coupling comprising intermediate optical elements, e.g. lenses, holograms: optical features
H01S 3/105
Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or…