- Some novel properties of one-layer inorganic As 50 Se 50 photoresists are demonstrated. The photosensitivity of the photoresists increases drastically (1000 times and more) upon exposure to short intense light pulses. The exposure characteristics can be changed from steep to gently sloped ones. The photoresists can be used effectively in both negative and positive modes. Combination of these properties with good optical properties such as a high refractive index, high transparency in the IR and high resolution, makes As 50 Se 50 photoresists attractive for application in nonconventional optics. Close packed spherical and cylindrical microlens arrays for IR based on the As 50 Se 50 photoresists are fabricated and tested. The advantage of this technique is in the elimination of thermal reflow and plasma etching that are commonly used. © 1997 American Vacuum Society.