Holographic Fabry-Perot spectrometer.
We propose a spectrum analyzer based on the properties of a hologram recorded with the field transmitted by a Fabry-Perot etalon. The spectral response of this holographic Fabry-Perot spectrometer (HFPS) is analytically investigated in the paraxial approximation and compared with a conventional Fabry-Perot etalon of similar characteristics. We demonstrate that the resolving power is twice increased and the free spectral range (FSR) is reduced to one-half. The proposed spectrometer could improve the operational performance of the etalon because it can exhibit high efficiency and it would be insensible to environmental conditions such as temperature and vibrations. Our analysis also extends to another variant of the HFPS based on holographic multiplexing of the transmitted field of a Fabry-Perot etalon. This device increases the FSR, keeping the same HFPS performance.
A Volume Holographic Sol‐Gel Material with Large Enhancement of Dynamic Range by Incorporation of High Refractive Index Species
Improved performance of volume holographic sol-gel materials-refractive index modulations in the 10^2 range, diffraction efficiencies near 100 %, and low levels of noise scattering-are reported that arise from the incorporation of Zr-based high refractive index species capable of diffusing from dark to bright fringes of the interference pattern (see figure).
Latent-imaging photopolymer systems.
A new high-resolution latent-imaging photopolymer system is reported for recording thick refractive-index patterns such as volume phase holograms and grating devices. A photosensitive polymerization initiator is chemisorbed on the surfaces of a porous glass matrix (average pore diameter 4 nm). The latent image is recorded by exposing the sensitized glass such that the initiator is selectively destroyed in the desired pattern. During this step, there are only small changes in the optical properties of the material, thus preventing interactions between the image being written and the optical fields writing it. The image is then developed by filling the matrix with a suitable monomer mixture and using a uniform optical exposure to initiate polymerization. During the development step, the spatially modulated initiator concentration, which constitutes the latent image, leads to a corresponding modulation of the refractive index of the polymer, and increases in the amplitude of the image of as much as a factor of 50 (Deltan up to 3 x 10(-4)) have been observed.