| 摘要 |
PURPOSE:To realize edge reflectivity of (21+ or -3)% easily and stably, and to prevent the effect of return beams by bringing the wavelength of laser beams to lambda and forming an edge-face protective film consisting of an Al2O3 film having optical length or lambda/4 and an SiO2 film being shaped onto the Al2O3 film and having optical length of lambda/4 onto a laser-beam outgoing edge face. CONSTITUTION:The film thickness of an Al2O3 film 3 and an SiO2 film 4 in a semiconductor laser is set so that optical length obtained by l=n.d (n represents a refractive index and d a film thickness) is brought to lambda/4. Consequently, not only the peak value of edge reflectivity is reduced but also there are the small peaks of the gradients of each curve A-C within a range of (21+ or -3)%. Accordingly, even when the film thickness of the Al2O3 film constituting an edge-face protective film 2 is dispersed and dispersion of approximately + or -10% is generated from predetermined lambda/4 in the optical length of the Al2O3 film, the range of the film thickness of the SiO2 film 4 for attaining (21+ or -3)% aiming at edge reflectivity exists extending over a wide range. Especially when the film thickness of the SiO2 film 4 is set within a range of + or -20% to 1/1.45Xlambda/4 shown in X, the dispersion of the film thickness of the Al2O3 film 3 within approximately 10% can be compensated positively, and edge reflectivity of (21+ or -3)% can be realized easily and stably, thus stably conducting laser oscillation operation.
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