Dual-wavelength membrane-based diffractive optical element with extended depth-of-focus for optical pickup head

Abstract

An improved structure and optimization method for a high-numerical-aperture application for optical pickup heads that uses a low-stress silicon-nitride-membrane-based diffractive optical element to generate dual-wavelength pseudo-Bessel beams is described in this paper. The dual-wavelength membrane-type diffractive optical element with an extended focal depth for next-generation optical pickup applications has been demonstrated. The theoretical simulation and fabrication results detailing the resolution, longer depth-of-focus and diffractive efficiency are presented for the newly designed membrane diffractive optical element (DOE). This implies that the problems of disc vibration as well as the assembly and optical alignment of the many elements are solved.