Nitride based semiconductor laser device with oxynitride protective coatings on facets
One facet and the other facet of a nitride based semiconductor laser device are respectively composed of a cleavage plane of (0001) and a cleavage plane of (000 1 ). Thus, the one facet and the other facet are respectively a Ga polar plane and an N polar plane. A portion of the one facet and a portion of the other facet, which are positioned in an optical waveguide, constitute a pair of cavity facets. A first protective film including oxygen as a constituent element is formed on the one facet. A second protective film including nitrogen as a constituent element is formed on the other facet.
1. A nitride based semiconductor laser device comprising:
a nitride based semiconductor layer having an optical waveguide extending in a substantial [0001] direction and having one facet composed of a substantial (0001) plane and the other facet composed of a substantial (000-1) plane as a pair of cavity facets;
a first protective film provided on said one facet and including oxygen as a constituent element; and
a second protective film provided on said other facet and including nitrogen as a constituent element,
wherein the intensity of laser light emitted from said one facet is higher than the intensity of laser light emitted from said other facet,
said first protective film further includes nitrogen as a constituent element, the first protective film's oxygen composition ratio being higher than the nitrogen composition ratio, and
said second protective film further includes oxygen as a constituent element, the second protective film's nitrogen composition ratio being higher than the oxygen composition ratio.
2. The nitride based semiconductor laser device according to claim 1 , wherein
each of a portion of said one facet and a portion of said other facet in said optical waveguide has unevenness, and
the depth of a first recess in said one facet is smaller than the depth of a second recess in said other facet.
3. The nitride based semiconductor laser device according to claim 1 , further comprising
a dielectric multilayer film formed on said one facet and including said first protective film,
wherein said dielectric multilayer film includes an oxynitride film and an oxide film that are laminated in this order from said one facet, the oxygen composition ratio is higher than the nitrogen composition ratio in said oxynitride film, and said first protective film is said oxynitride film.
4. The nitride based semiconductor laser device according to claim 1 , further comprising
a dielectric multilayer film formed on said one facet and including said first protective film,
wherein said dielectric multilayer film includes a first oxynitride film, a second oxynitride film, and an oxide film that are laminated in this order from said one facet, the oxygen composition ratio is higher than the nitrogen composition ratio in said first oxynitride film, the nitrogen composition ratio is higher than the oxygen composition ratio in said second oxynitride film, and said first protective film is said first oxynitride film.
5. The nitride based semiconductor laser device according to claim 1 , further comprising
a dielectric multilayer film formed on said other facet and including said second protective film,
wherein said dielectric multilayer film includes an oxynitride film and an oxide film that are laminated in this order from said other facet, the nitrogen composition ratio is higher than the oxygen composition ratio in said oxynitride film, and said second protective film is said oxynitride film.
6. The nitride based semiconductor laser device according to claim 1 , further comprising
a dielectric multilayer film formed on said other facet and including said second protective film,
wherein said dielectric multilayer film includes a first oxynitride film, a second oxynitride film, and an oxide film that are laminated in this order from said other facet, the nitrogen composition ratio is higher than the oxygen composition ratio in said first oxynitride film, the oxygen composition ratio is higher than the nitrogen composition ratio in said second oxynitride film, and said second protective film is said first oxynitride film.
7. The nitride based semiconductor laser device according to claim 1 , wherein said first protective film includes at least one of AlO X N Y , SiO X N Y and TaO X N Y , where X>Y.
8. The nitride based semiconductor laser device according to claim 1 , wherein said second protective film includes at least one of AlO X N Y , SiO X N Y and TaO X N Y , where X<Y.