Magnetooptical isolator for free space and waveguide applications operating at 0.4-5 um

The laser sources emitting from short to long infrared wavelengths are used for environmental sensing, metrology and clinical diagnosis, LADAR applications. The second atmospheric window between 3-5 um is crucial where a large number of gases, e.g. methane, nitric oxide, carbon mono-dioxide or formaldehyde, can be detected. Due to the presence of very strong fundamental stretching modes of O-H, C-H and N-H bonds that are up to orders of magnitude stronger than the overtones in the near-IR, detection limits down to sub-ppb concentrations can be obtained. One of the necessary components for such measurements is optical isolator. However, there are no commercially available devices for this spectral range. The main objective of the current proposal is to create an optical isolator for 3-5 um that could be used in laser applications. The technical approach is to develop a vitreous material that is transparent in mid IR spectral region and can accept high concentration of ions that increase magnetooptical constant. Dependence of magnetooptical sensitivity on different dopants will be studied, a technology of fabrication of mid IR transparent magnetooptical glass will be developed and optical isolation in 3-5 um region will be demonstrated in bulk and fiber geometries.