Abstract

A new technique of integrating a miniaturized 3-D optical systems into a single block of crystal by locally recorded photorefractive holograms is proposed. Through nonvolatile photorefractive holographic recording in doubly doped LiNbO₃ crystal, many holographic optical elements can be integrated into a single photorefractive crystal and a integrated optical systems with the advantages of solid-state and multifunction can be realized. In this paper, the basic idea of 3-D Photorefractive integration of optical systems is introduced. Then the technique of nonvolatile photorefractive holograms in doubly doped LiNbO₃ crystals is investigated experimentally and theoretically, mainly including the principles of nonvolatile recording and its optimization. Four kinds of doubly doped LN crystals in the same doping system, they are LiNbO₃:Fe:Mn, LiNbO₃:Ce:Mn, LiNbO₃:Ce:Cu and LiNbO₃:Fe:Cu, are demonstrated for nonvolatile recording. Among the four crystals, three kinds of light-induced effects are observed, and they are photochromic effect, bleaching effect and no-sensitization effect. According to these three effects, a two-step and a three-step recording/fixing schemes are proposed to record nonvolatile photorefractive holograms. As examples of integrated 3-D optical systems, both Mach-Zehnder optical interferometer and DWDM switch-matrices are designed.

© 2003 Optical Society of America