Abstract: A semiconductor laser device having a waveguide constructed in a stack of layers including, on a substrate transparent and having a refractive index ns for laser light, a first clad layer of a refractive index nc1, a second clad layer of a refractive index nc2, a third clad layer of a refractive index nc3, a first conductivity type guide layer of a refractive index ng, an active quantum well layer, a second conductivity type guide layer, a second conductivity type clad layer, and a second conductivity type contact layer deposited in this order, wherein the waveguide has an effective refractive index ne, and a relationship of nc2<(nc1, nc3)<ne<(ns, ng) is satisfied.

Abstract: A second harmonic generation laser system comprising: a non-linear frequency converting medium; and an external cavity pump laser that produces optical energy at a single mode and at a single frequency and that is disposed to provide the optical energy to the non-linear frequency converting medium.

Abstract: A solid-state laser crystal constituting a laser-diode-excited solid-state laser apparatus or an optical fiber constituting a fiber laser apparatus or fiber laser amplifier is doped with one of Ho3+, Sm3+, Eu3+, Dy3+, Er3+, and Tb3+ so that a laser beam is emitted from the solid-state laser crystal or the optical fiber, or incident light of the fiber laser amplifier is amplified, by one of the transitions from 5S2 to 5I7, from 5S2 to 5I8, from 4G5/2 to 6H5/2, from 4G5/2 to 6H7/2, from 4F3/2 to 6H11/2, from 5D0 to 7F2, from 4F9/2 to 6H13/2, from 4F9/2 to 6H11/2, from 4S3/2 to 4I15/2, from 2H9/2 to 4I13/2, and from 5D4 to 7F5. The above solid-state laser crystal or optical fiber is excited with a GaN-based compound laser diode.

Abstract: A semiconductor laser diode capable of achieving an improvement in kink level and an improvement in catastrophic optical damage (COD) level. The semiconductor laser diode includes a first-conductivity type semiconductor substrate, a first-conductivity type clad layer formed over the substrate, an active layer formed over the first-conductivity type clad layer, a second-conductivity type clad layer formed over the active layer, and provided with a ridge, and a light confining layer formed on the second-conductivity type clad layer, and made of a first-conductivity type semiconductor material, the light confining layer including higher-order mode absorption layers having an energy band gap lower than optical energy produced in the active layer, and refractive index control layers having a refractive index lower than that of the higher-order mode absorption layers. The higher-order mode absorption layers and refractive index control layers are laminated in an alternate manner.