Nonlinear optical interferometer

Abstract

The interferometer described, based on the second harmonic generation of light, is useful in the contouring of refractive objects with large variations in optical depth. The device is a real-time common-path self-referencing interferometer that yields interferograms in the visible with an equivalent wavelength of the order of 50 microm. We describe experiments that show that it can serve as a useful device. The key to the device is the use of Y-cut LiNbO(3) configured for surface acoustooptic applications rather than for conventional second harmonic applications. The crystals are noncritically phase matched by temperature control and are used with a repetitively pulsed Nd:YAG laser operating at 1.06 microm.

Diagnostics for steady state plasmas

“…The total round-trip phase will only be comparable often much smaller than the phase changes from mechanical vibrations. Vibration compensation in a two-colour scheme is mandatory [146][147][148]. Generating the second wavelength via harmonic generation by doubling the frequency is advantageous in case the optical path length changes by the plasma are smaller than those introduced by mechanical vibrations.…”

Optical interferometry

“…Second-harmonic interferometers produce a fringe pattern corresponding to the phase difference between two second harmonic waves generated at different points in the optical path from the original wave at the fundamental frequency. Optical systems that are analogues of the Fizeau, Twyman-Green and Mach-Zehnder interferometers have been described (Hopf et al 1980, Hopf andCervantes 1982). Figure 34 shows an interferometer using two frequency-doubling crystals that can be considered an analogue of the Mach-Zehnder interferometer.…”

Interferometric measurement of phase mismatch in potential second harmonic generators

“…Phase matching in crystals manifests itself through the linear property of refractive index. Alternative to the use in the generation of high power, short wavelength laser fields, some crystals with lower conversion efficiencies have been shown to be versatile diagnostic tools' as components of nonlinear optical interferometers as described in Chapter 3, (Hopf and Cervantes 1982). One version of this interferometer, the nonlinear Fizeau, is used with collimated laser beams to search for crystals to be used in interferometers a.t 1.32 \.1m.…”

“…In this dissertation we examine the use of one of these interferometers, the nonlinear Fizeau (NLF) to analyze possible phase matchable SHGs in a materials search. The NLF as well as some of the other nonlinear interferometers are described in detail in the dissertations of Cervantes (1982) and Liepmann (1983).…”