David Meyer Braun

US Patent:

54348749, Jul 18, 1995

Filed:

Oct 8, 1993

Appl. No.:

8/134424

Inventors:

Julie E. Fouquet - San Carlos CA
David M. Braun - Santa Rosa CA

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

H01S 310

US Classification:

372 20

Abstract:

The invention increases the tuning range of a laser by altering the output coupler reflectivity. In a first embodiment of the invention, the tuning range of an external cavity laser is increased by applying a substantially spectrally flat reflective coating to the front facet of a semiconductor laser 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 were applied to the output coupler to generate reflective characteristics that change according to wavelength. The complex coatings 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.