Design and fabrication of diffractive microlens arrays on Si substrates for 128 X 128 PtSi infrared focal plane arrays

128X128 diffractive microlens array was designed by considering the correlative optical and processing parameters for 3-5 mu m wavelength range with a microlens diameter of 50 mu m.. The lens f number and array pitch are f/2.5 and 50 mu m, respectively: The diffractive microlens arrays were fabricated on the surface of Si substrates by successive photolithography and Ar+ ion-beam-etching technique. The practical processes and fabrication method were discussed. The optical characteristics and the surface relief structure of the 128X128 Si diffractive microlens array were measured.