Integrated-optic devices in lithium niobate: technology and applications

Abstract

Integrated-optic devices in LiNbO3 are reviewed with emphasis on fabrication technologies (titanium indiffusion, proton exchange) including the critical areas of outdiffusion, fabrication tolerances, and stability, further on fibre coupling, packaging and on the application of these devices in the field of optical communications.

Integrated optics Pockels cell high-voltage sensor

“…The noise induced in the device is believed to be mostly due to the optical damage caused by the photo-refractive effect in the waveguide [51, p. 5]. It is reported [51] that in order to keep the photo-refractive effect negligible when working with 633 nm light, the optical power through the waveguides should not exceed a few micro-Watts. This was obviously not the case for our devices; optical powers over 200 AW passed through some of these waveguides operating with Ao = 670 nm light.…”

“…Because the laser can, and should, be kept on at all times in applications such as high voltage metering, the original drift can be over-looked as long as the stabilized bias is close to its intended value of 90°. Moreover, this drift depends mainly on the wavelength and on the optical power [51], [53]. It should be negligible for lower optical powers or longer wavelengths.…”

“…Since the first fabrication of optical waveguides in LiNbO3 by the in-diffusion of 31 titanium in 1974 [43], this technology is seen by some [51] as being the most successful in realizing high-quality waveguides in a substrate material, which has excellent optical properties. The high status of integrated optic devices in lithium niobate may be characterized by intensity modulators with a 3 dB electrical bandwidth up to 18 GHz [44], complex switch-arrays with 64 switches integrated on one substrate [45], high-speed lowinsertion-loss PSK modulators for coherent systems [46], and fibre coupled devices with insertion loss figures less than 1 dB [47].…”