Holography-based wavefront sensing.

We describe a modal wavefront sensing technique of using multiplexed holographic optical elements (HOEs). The phase pattern of a set of aberrations is angle multiplexed in a HOE, and the correlated information is obtained with a position sensing detector. The recorded aberration pattern is based on an orthogonal basis set, the Zernike polynomials, and a spherical reference wave. We show that only two recorded holographic patterns for any particular aberration type are sufficient to allow interpolated readout of aberrations to lambda/50. In this paper, we demonstrate the capability of detecting errors between +/-2lambda PV for each orthogonal set at rates limited only by the speeds of the detection electronics, which could be up to 1 MHz. We show how we take advantage of the unavoidable intermodal and intramodal cross talks in determining the type, amplitude, and orientation of the wavefront aberrations.

Polymer relaxations determined by use of a temporally and thermally stable interferometer.

We describe a phase-controlled, highly stable interferometer that is ideal for use in long-time and high-temperature studies. We recorded output intensity variations of <0.2% for over 6 h at temperatures up to 150 degrees C. The setup was used to study in situ the temperature and frequency characteristics of a thin polymer film composed of 4-dimethylamino-4?-nitrostilbene doped into poly(methyl methacrylate). The mobility of the dopant molecules, which governed the electro-optic property of the film, was used to probe the dye-doped polymer's rheology. We demonstrate one application of the interferometer in probing both the alpha and the beta relaxations of the polymer.

Improved interferometer studies of linear electro-optic effects of dye-doped polymers.

The basic Mach-Zehnder interferometer was modified for use in in situ temperature-dependent linear electro-optic (LEO) measurements of thin films of 4-dimethylamino-4?-nitrostilbene (DANS) doped into poly(methyl methacrylate) (PMMA). Optimum interferometer phase stability was possible because of an incorporated electronic feedback system. Film thickness variation was compensated for to obtain more accurate LEO coefficient measurements and thus the second-order susceptibility. Moreover, both the alpha relaxation associated with the glass transition, T(g), and beta relaxation associated with the secondary transition occurring below T(g) of PMMA + 2 wt.% DANS was obtained.