Holograms have been constructed in photopolymer materials which give bright, low-noise images. These holograms are of the volume type and have no surface variations in all but a few special cases. They are constructed in virtually real time and in situ, requiring no processing. Materials sensitive to both uv and blue-green radiation have been used. In this paper, the mechanism of hologram formation is examined. Experimental results on sensitivity, spatial frequency response, particle scattering noise, and nonlinearities are discussed. A few holographic applications of the material are presented.

Volume-phase holographic (VPH) gratings show great potential as an alternative dispersing element to the classical surface-relief (SR) gratings presently used in most astronomical spectrographs. We present an introduction to this technology and give the results of an evaluation of three di †erent VPH gratings : a 300 line mm~1 grating optimized at 1064 nm, a 1200 line mm~1 grating optimized at 532 nm, and a 2400 line mm~1 grating optimized for operation at 532 nm.

A diffraction grating technology based upon volume-phase holograms shows promise of enhanced performance for many applications in astronomical spectroscopy over classical surface-relief grating technology. We present a discussion of the underlying physics of a volume-phase grating, give some theoretical performance characteristics, present performance data for a real volume-phase grating, and discuss some potential applications for this grating technology.

been proposed. The interrogation system has the peculiarities of small size, low power consumption, and high accuracy. Experimental results show that the interrogation can be used to interrogate the FBG sensors with wavelength bandwidth of 42 nm, SNR of 43dB, wavelength accuracy of Ϯ10 pm, and wavelength ability of Ϯ15 pm. The interrogation system based on the InGaAs linear image sensor is easy to be integrated and has a good prospect for smart sensing.

We demonstrate pulse stretching and compression in a high-repetition-rate chirped-pulse Ti:sapphire regenerative amplifier, using high-efficiency holographic transmission gratings. A quantitative dispersion measurement technique is developed to characterize dispersion of the system to the third order. After recompression with third-order dispersion compensation, 3.1-microJ 85-fs, nearly transform-limited pulses are obtained.