JPS6447082A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To improve the S/N ratio of an optical pulse signal without lowering a transfer speed by forming a multilayered film constituting a multilayered film interference filter on an exit surface, through which light emitted from a light emitting semiconductor element such as an LED or an LD is derived, by providing on the exit surface comprising a material of the refractive index of ns, an anti-reflection coating composed of a set of a first layer of the refractive index of nz and of the optical depth of lambda/2 and of a second layer of the refractive index of n1 and the optical depth of lambda/4. CONSTITUTION:A lambda/2 layer 5 and lambda/4 layer 3 are stacked repeatedly on an exit surface 2 of an edge emission type LD1. The lambda/2 layer 5 is made for example of titanium oxide (TiO2) of the refractive index n2=2.35, and the lambda/4 layer 3 of SiO2 of the refractive index n1=1.46. Multilayered films 2.5 formed on the exit surface 2 function as interference filters which can reduce the spectral width of output light of the LD1 transmitting those multilayered films to about several to several hundreds of Angstrom narrower than the half spectral width of about 1400Angstrom in the prior art end surface emission type LD1 only including the lambda/4 layer 3 formed therein. Additionally, the lambda/2 layer 5 does not affect the reflectance of the lambda/4 layer 3, thus substantially without changing the output light intensity of the LD1.