In this thesis, strong optical feedback is utilized to realize broad-band wavelength tuning and to stabilize the frequency of a semiconductor diode laser in a grating-external-cavity (GEC) configuration. To reach the regime of strong optical feedback, the laser facet through which the feedback occurs has to be antireflection (AR) coated. Multi-layer AR coatings were designed using SiO2, Si3N4, SiOxNy, and a:Si for specific laser waveguide structures, and were fabricated by an electron cyclotron resonance, plasma enhanced, chemical vapor deposition (ECR-PECVD) system. The film thickness and refractive index were monitored by in situ ellipsometry during the deposition. This scheme permitted very low reflectivities, in the order of 5 x 10-4, to be readily and reproducibly obtained. The diode laser thus obtained was used in a strong feedback configuration. Light emitted from the coated facet was collimated and fed back onto the laser cavity after being reflected off a diffraction grating. The diffraction grating provides frequency selectivity, which is a desirable feature for obtaining a stable single longitudinal mode laser. The laser in this configuration oscillated in a single mode with a greater than 30 dB side mode suppression ratio and a wide tuning range. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25172 |
| Date | 08 1900 |
| Creators | Guo, Liqiang |
| Contributors | Cassidy, D. T., Mascher, P., Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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