Effects on Polychromatic Integral Diffraction Efficiency for Dual-wavebands Harmonic Diffractive Optical Elements

摘要

Harmonic diffractive optical elements (HDOEs) can make multiple-wavebands imaged on the same image plane, which have be widely used in the infrared imaging optical systems. The mathematical model of effects on diffraction efficiency and polychromatic integral diffraction efficiency (PIDE) caused by single point diamond turning processing for dual-wavebands harmonic diffractive optical elements have been set up. And the expressions on diffraction efficiency and PIDE by machining errors including micro-structure heights and widths have been deduced. In order to make the maximum PIDE value over the dual-wavebands, the machining errors should be designed and distributed. Based on the above analysis, the dual-waveband harmonic diffractive optical elements used in 3.7μm-4.3μm and 8.7μm-8.7μm wavebands have been analyzed and simulated with MATLAB software on the two conditions including the oblique incidence and general incident distributions for the machining errors, which can be directly used to evaluate broadband hybrid diffractive-reflective optical systems imaging quality. Through the relationship between PIDE and machining errors of dual-wavebands HDOEs, the optical modulation transfer function can be analyzed. The results can be applied to dual band imaging optical systems for controlling the harmonic diffractive optical element processing and machining errors as well as the incident angle design for the hybrid diffractive-reflective optical systems.