Abstract: A self-frequency-doubler laser element having a three-dimensional optical waveguide includes a first transparent insulating substrate having both a DFB grating and a grating reflector formed on one side of the DFB grating, a Nd.sup.3+ -ion-doped thin glass film laid over the first transparent insulating substrate, a thin nonlinear optical film laid over the thin glass film, a second transparent insulating substrate laid over the thin nonlinear optical film, and a thin reflecting film laid over the second transparent insulating substrate, wherein the following conditions are satisfied: nf-ng=0.01 to 0.05, and nf and ng are greater than ns and nc, where ns, ng, nf, and nc are the refractive indices of the first transparent insulating substrate, the thin glass film, the thin nonlinear optical film, and the second transparent insulating substrate, respectively.