Rare-earth-doped LiNbO 3 waveguide amplifiers and lasers

Abstract

Rare earth doping (above all by Nd3+ and Er3+) mainly of silica-based optical fibers has been applied to develop fiber optical amplifiers and lasers of excellent properties [1-3]. Moreover, it can also be an attractive method to fabricate active devices on the planar substrates of integrated optics. In particular, rare earth doping of LiNbO3 will significantly increase the potential of this material allowing a monolithic integration of optical amplifiers, lasers, modulators and other active and passive devices on the same substrate. Furthermore, by taking advantage of the excellent electro-optical, acousto-optical and nonlinear optical properties of LiNbO3 [4] in combination with the rare earth induced optical gain, new devices of very attractive features can be developed, e.g. by incorporating a phase or intensity modulator in the cavity of a waveguide laser, mode-locking or Q-switching will be easily possible to generate short or intensive optical pulses. The integration of a tunable acousto-optical or electro-optical wavelength filter in the waveguide cavity will lead to a tunable laser. A wavelength filter in combination with an optical amplifier will allow to modify the overall gain characteristics and to suppress unwanted noise. Also nonlinear optical effects as second harmonic generation e.g. can be exploited in a very efficient manner, taking advantage of the resonantly enhanced laser field in the waveguide cavity. Furthermore, optical bistability and intensity-dependent switching seem to be possible in particular with Er-doped devices.