Ultraprecision machining of diffraction optical elements on soft semiconductor crystal

Diamond turning was used to generate microstructures on monocrystalline InSb. Different diffractive optical elements were machined (sinusoidal phase grating, continuous-phase Fresnel lens, and stepwise-phase Fresnel lens); the height of all features is in the micrometer range. The concept of transition pressure value was applied in order to demonstrate that it is possible to generate microstructures in rotational parts made of brittle semiconductors which can serve as the first-generation shim by employing electroforming process aiming for mass production of plastic optical parts. Results indicated that the aspect ratio suitable to sculpt microstructures by mechanical material removal processes applied to semiconductor crystals is directly related to its transition pressure value. Micro-Raman spectroscopy has been used to probe the phase transformation after machining and the recrystallization state after annealing.