Diffractive phase elements by electron-beam exposure of thin As2S3 films

Variable-dose electron-beam exposure of thin amorphous As2S3 films is studied as a potential fabrication technique of index-modulated diffractive optical elements for the near infrared. The relationship between the electron dose and the phase delay is determined using a coarse grating structure, which eliminates the influence of volume diffraction and proximity effects. The effective refractive index change is determined by comparing experimental and calculated zeroth- and first-order diffraction efficiencies, taking into account the small but detectable surface modulation.