Optical Pulse Compression and Very High-Speed Light Beam Scanning Using Guided-Wave Acoustooptic Bragg Diffraction*

Abstract

It has been shown that guided-wave planar acoustooptic (AO) beam deflectors of large bandwidth and high diffraction efficiency can be realized in LiNbO3 substrates, (1,2) and that such AO beam deflectors are suited for a number of applications in wideband optical communications and information processing. (3) In fact, some encouraging results have already been demonstrated in the experiments involving spectrum analysis(3,4) and convolution of wideband rf signals(5) as well as deflection/switching of a light beam at moderate-speed.(3) In this paper we report research progress on further utilization of such AO beam deflectors for optical pulse compression and very high-speed light beam scanning. In order to carry out a number of additional studies including a more detailed experiment on spectrum analysis and the two new experiments just mentioned, we have recently fabricated a very wideband deflector in a Y-cut LiNbO3 Ti-diffused waveguide. This deflector employs a three-element tilted-array transducer with the center frequencies of 275, 432 and 648 MHz, and has a measured deflector bandwidth of 500 MHz. This bandwidth represents the largest that has been achieved thus far. Using the AO Bragg diffraction of a He-Ne laser guided-light beam from the surface acoustic waves generated by a linear FM rf (chirp) waveform, we have achieved a compression ratio of 200 in the optical pulse compression experiment and a scanning rate of 125 x 106 spots/sec for 50 spots in the beam scanning experiment. The detailed results of these two experiments will be reported. We will discuss means for further utilization of this wide­band deflector to obtain a much larger compression ratio and a much higher scanning rate. We will also discuss some potential applications of the resulting devices in wideband optical communications and data processing.