Semiconductor laser element having end-facet protection layer which includes unoxidized or unnitrided first sublayer formed on end facet and second sublayer produced by oxidizing or nitriding the surface of the first sublayer

摘要

A semiconductor laser element includes: a stack of layers having resonator facets; and at least one protection layer formed on at least one of the resonator facets. Each of the at least one protection layer includes at least first, second, and third sublayers. The first sublayer is formed nearest to the stack among the at least first, second, and third sublayers, and made of a material not containing oxygen (or nitrogen) as a constituent element. The second sublayer is made of an oxide (or nitride) produced by oxidizing (or nitriding) a portion of the first sublayer. The third sublayer is formed farthest from the stack among the at least first, second, and third sublayers, and made of an oxide (or nitride). The thickness d 2 of the second sublayer and the total thickness d 1 of the first and second sublayers satisfy a relationship, 0.1<=d 2 /d 1 <=0.9.