IR polarimetry using compact circular polarized IR antennas integrated with InGaAsSb Nano-load

The imaging polarimetry can measure the polarization status of the scene in addition to the intensity and color which the traditional imager can detect. The polarization information can show the surface roughness and shading of target material and the distinct contrast image which is uncorrelated with intensity and color (J. S. Tyo, D. L. Goldstein, D. B. Chenault, and J. Straw, Appl. Opt, 45, 5453-5469). Detecting the circular polarization (CP) is a key factor for the IR imaging polarimetry. The traditional IR imagers to detect CP have implemented a quarter-wave plate integrated with a linear polarizer (K. A. Bachman, J. J. Peltzer, P. D. Flammer, T. E. Furtak, R. T. Collins, and R. E. Hollingsworth, Opt. Express, 20(2), 1308-1319). Instead of the traditional polarization plates, antennas with different polarizations loaded with the IR detectors can be used to measure the polarization of the received IR signals. The spiral antenna has been introduced as a typical antenna structure for CP in IR frequency regime (F. J. Gonzalez, B. Ilic, J. Alda, and G. D. Boreman, IEEE J. Sel. Topics Quantum Electron., 11, 117-120). However the structure requires the multiple circular or rectangular turns and thus it would require much space within a polarimetric detector cell.