A silicon nitride (SiN<sub>x</sub>) membrane diffractive optical element (DOE) designed to exhibit beam-splitting and focusing behavior at visible wavelengths has been fabricated and tested. Since the fabrication process is based on silicon micromachining technology, the DOE is easily integrated with a laser diode chip and a photodiode chip on a silicon substrate to function as the hologram-laser-photodiode unit for use in the pickup head of a CD or DVD system. The SiN<sub>x</sub> film is deposited with low-pressure chemical-vapor deposition and the free-standing membrane is formed by KOH etching. The transmissive DOE showed a high diffraction efficiency (>20% for a binary-phase-level element). The experimental evaluation was in good agreement with the designed and modeled predictions.
© 2003 Optical Society of America
Chien Chieh Lee, Yu Cheng Chang, Chih Ming Wang, Jenq Yang Chang, and Gou Chung Chi, "Silicon-based transmissive diffractive optical element," Opt. Lett. 28, 1260-1262 (2003)