Method and apparatus for optimizing the output characteristics of a tunable external cavity laser

摘要

The invention increases the tuning range of a laser (14) by altering the output coupler (16) reflectivity. In a first embodiment of the invention, the tuning range of an external cavity laser (27, 14, 24, 26) is increased by applying a substantially spectrally flat reflective coating (64, 66, 68) to the front facet (16) of a semiconductor laser (14) which has higher reflectivity than the uncoated front facet. In addition to increasing the tuning range, the increased reflectivity of the front facet reduces the laser threshold current for all laser wavelengths. In a second embodiment of the invention, various complex coatings (70, 72) were applied to the output coupler (40) to generate reflective characteristics that change according to wavelength. The complex coatings (40) enhance reflectance at the edges of the laser tuning curve without adversely affecting the output power at the center wavelengths. This further increases the tuning range of the laser while simultaneously maintaining high output power for each selected output wavelength. IMAGE