Gradient-index microlens formed by ion-beam sputtering

This paper describes the fabrication and characteristics of a gradient-index microlens by using a low-stress, high-transmittance film that is deposited by ion-beam sputtering. The key techniques in forming this film are sputtering with N(2) gas, performing ion-beam irradiation during deposition, and stabilizing the deposition acceleration current. An integrated device consisting of the microlens and a laser diode is demonstrated. The focusing spot size is 2 microm x 3 microm at a distance of 11 microm from the lens facet.