Microlens fabrication by selective oxidation of composition-graded digital alloy AlGaAs

We have fabricated refractive microlenses using selective oxidation of composition-graded digital alloy AlGaAs. The chirped short period superlattice of GaAs-AlAs was used to grade the composition of AlGaAs along the growth direction for a reproducible and controllable composition and oxidation profile. The oxidized profile of linearly composition-graded digital alloy AlGaAs shows a circular convex lens shape. The focused spot pattern of the beam at the focal point of the fabricated circular buried microlens reveals the strong focusing function of the microlens. Circular buried microlenses with mesa diameter of 20 μm exhibited focal length of 28-33 μm and a focused spot diameter of 4.0-6.4μm, which are varied by oxidation time.