| 摘要 |
PURPOSE:To obtain a dielectric multi-layer protective film of low and high reflectivity useable over a wide wavelength range by constructing the film such that there are alternately superimposed two kinds of dielectric films of a TiO2 or ZnS film of a high reflectivity first dielectric film and an Al2O3 film of a low reflectivity second dielectric film. CONSTITUTION:There is applied to a semiconductor laser chip 1 of oscillation wavelength lambda=7800Angstrom and of an equivalent refractive index 3.4 at an end surface thereof. A TiO2 film 2 having refractive index 2.2 is evaporated by lambda/4 thickness on a cleavage surface of the chip 1, and further an Al2O3 film 3 of refractive index 1.6 is evaporated by lambda/4 thickness on the resulting TiO2 film 2. Likewise, such a combination of the TiO2 film 4 and the Al2O5 film 5 is evaporated, repeatedly two times in all. For the control of the film thickness, a crystal resonator type film thickness monitor is employed to control the time of opening and closing a shutter of an evaporation source containing evaporation targets of Al2O3 and TiO2. Herein, for the evaporation of the TiO2 film, high purity O2 is introduced, and the refractive index is controlled by controlling oxygen partial pressure and an evaporation rate. |
