Preparation and Properties of SiO Antireflection Coatings for GaAs Injection Lasers with External Resonators

Improved techniques for the preparation of single-layer SiO antireflective coatings are discussed in detail. We infer from our results that the reflectivity of diode end surfaces is reduced to below 1% over a broad wavelength band using lambda/4 coatings. The use of lambda/4 rather than 3lambda/4 coatings minimizes losses in the coatings and maximizes the bandwidth over which the coating provides low reflectivity. The suppression of internal mode structure in external cavity GaAs laser spectra by the use of antireflection coatings is demonstrated for the first time. Coating degradation was not a serious problem in room temperature external cavity laser operation.