Movable Optical Frequency Ruler with Optical Activity

Abstract

Optical frequency rulers (OFR) are suggested for use as optical wavelength or frequency references for spectra manipulation or unknown wavelength measurement. In the past, complicated mechanisms that are not easy to utilize were used to make OFR, such as a double-slits with a high-speed fluid or an external circuit to control the liquid crystal birefringence. This work introduces a simple structure to produce an OFR, which should be easier to implement. It utilizes quartz block optical activity and two polarizers. Because of the strong wavelength dependence of the rotatory power, each wavelength component in the spectrum experiences a different amount of polarization angle rotation. Some components whose angles are perpendicular to that of the analyzer are filtered out and naturally form the OFR’s ticks. The numerical results show that those spectral ticks can be moved to higher or lower wavelengths by rotating the analyzer’s angle. This scheme provides another possibility for creating movable OFR with the merit of easy usage.