DEVELOPMENT, JUSTIFICATION, AND APPLICATIONS OF A MIDINFRARED POLARIZATION-DIVISION INTERFEROMETER

We report the development of a polarization-division interferometer (P DI) for the mid-infrared region. This interferometer uses a self-desig ned beamsplitter constructed in-house from a BaF2 polarizer and a matc hing substrate. In conjunction with a linear polarizer in front of the source and two roof-top mirrors, one in each arm of the interferomete r, the PDI divides the input beam into two orthogonal linear polarizat ion components, recombines them for interference at the beamsplitter, and directs the output beam at 90 degrees to the direction of the inpu t beam. Light exiting the interferometer is manipulated entirely with lenses, to avoid polarization distortions that are inherent to the ref lecting surfaces of the mirrors. Details of the instrumental design fo r this mid-infrared PDI are presented. The performance of the PDI is e valuated by measuring the circular dichroism of alpha-pinene and camph or and the linear dichroism of oriented polypropylene and polystyrene. These measurements establish the utility of the PDI to measure transm ission, circular dichroism, and linear dichroism spectra simultaneousl y without need for any additional components. The dichroic multiplex a dvantage (ability to measure dichroism in the entire mid-infrared regi on from a single measurement) and throughput advantage are demonstrate d.