Search

Wavelength- and angle-multiplexed holographic Bragg gratings are used as a highly sensitive wavelength sensor. An absolute wavelength accuracy as high as 0.3 pm has been demonstrated with gratings recorded in an Fe-doped LiNbO/sub 3/ photorefractive crystals of dimension of 5/spl times/5/spl times/4 (mm/sup 3/). This technique provides a simple and accurate solution to laser wavelength measurement in applications such as wavelength division multiplexed (WDM) fiber-optic networks, precision interferometry, Doppler spectroscopy, and others.

Existing imaging spectrometers are based either on precision-ruled diffraction gratings or thin holographic gratings. Both rely on angular dispersion of the gratings and require sufficient length (1 m) to achieve high (i.e., subangstrom) resolution. As a result, these devices are bulky, expensive, and inconvenient in field conditions. Volume Bragg gratings, on the other hand, rely on spectral selectivity of thick holograms that produce a single diffraction order and suppress all higher orders. This means that long paths are not necessary to achieve high spectral resolution, which depends on the thickness of the grating instead.