Optical Characterization of Metamaterials

Student Name: Hannah Murai Home Institution: Liberty University NNCI site: MONT @ Montana State University REU Principal Investigator: Dr. Wataru Nakagawa - Department of Electrical and Computer Engineering, Montana State University REU Mentor: Dr. Wataru Nakagawa - Department of Electrical and Computer Engineering, Montana State University Abstract: A polarimetric optical system's sensitivity to changing states of polarization affects the accuracy of its measurements. To quantify how accurately we can measure the changed state of polarization that is induced by a device under test (for example, a metamaterial), it is necessary to test the limits of the optical system in detecting any change in the state of polarization. The accuracy of our optical system in detecting small changes in the angle of polarization demonstrates its limitations for future measurements. We investigate our optical system's sensitivity to changes in the angle of linearly polarized light by utilizing the properties of a thin-film latching garnet Faraday rotator. This magneto-optic device can be used to non-reciprocally rotate the angle of polarization of linearly polarized light by nominally 45° at the operating wavelength of 1550 nm. We used a tunable diode laser to sweep the wavelength of the incident light from 1500 nm to 1580 nm to measure the Faraday rotation angle’s spectral dependence. We observed this dependence to be linear, achieving >5° change in Faraday rotation angle over the tested 80-nm wavelength range. This discovered relationship can be used to induce small changes in the Faraday rotation angle, thus allowing us to finely control the angle of polarization of the light transmitted by the Faraday rotator.