Simple method to evaluate coupling functions at antireflection-coated diode facets facing grating reflectors of long external cavities

The spectral content of the reflected light from a grating, positioned at a distance much longer than the diode length to form an external-cavity semiconductor laser, has been studied. The analytical expressions derived show that the coupling coefficient at the antireflection (AR)-coated diode facet facing the extended cavity can be divided into two factors, of which one is due to the off-overlapping between the centers of the diode mode and its reflected counterpart, and the other is due to the alteration of the wave vector after being dispersed by the grating.<
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