Volume Bragg gratings for spectral and coherent beam combining in MWIR spectral region

ABSTRACT: The objective of the proposed research is to develop a new type of volume holographic elements that can operate in mid IR spectral region. To achieve this goal, research will be directed to a photo-thermo-refractive (PTR) glass which provides a photo-thermo-induced refractive index change while being transparent in the spectral range from 3 to 5 um, and to demonstration of the feasibility of fabrication of volume Bragg gratings from such glass for laser beam control and fine filtering in receivers. As a risk mitigation effort, a research will be extended to direct writing of volume gratings in several optical glasses that are transparent in mid IR spectral region. BENEFIT: Creation of holographic optical elements with low losses and high tolerance to laser radiation would be extremely beneficial for military application in the mid-IR spectral region because it would enable a dramatic increase in brightness of mid IR laser sources without an increase in weight, size, and energy consumption. Such diffraction gratings will provide unprecedented fine spectral and angular selection for both transmitters and receivers. This will enable development of high power, compact and robust lasers operating in the mid-IR window of transparency which should find wide applications for both DoD (effective missile sensor counter measures, night vision, and remote sensing) and commercial (micromachining and medical) needs.