Quantum frequency goniometer utilizing frequency measurement of continuously tuned laser

Abstract

High-precision small-angle measurement holds critical significance in advanced manufacturing and scientific research. Optical methods are highly favored for their non-contact characteristic, high accuracy, and exceptional sensitivity, yet traditional optical methods have limitations in measurement range and resolution. Since frequency is the most precise physical quantity, the resolution of angle measurement can be greatly improved by converting it into frequency measurement. In this paper, we propose a quantum frequency goniometer (QFG), wherein angular displacement is converted into frequency shifts, enabling exceptionally high resolution due to the precise measurement of frequency. The QFG involves the interference filter (IF) for frequency selection and the corner cube array (CCA) for frequency continuous tuning compensation. Based on the sensitivity of laser frequency to changes in cavity length and the incident angle of the IF, the QFG can accurately detect minute angular rotations. Numerical calculations indicate that the QFG achieves a resolution of 10−4 arcsecond, with a measurable range extending beyond 5°. This resolution surpasses that of existing methods by an order of magnitude. Moreover, we conducted a preliminary experiment to evaluate the continuous oscillation characteristics of an IF-based external cavity diode laser in conjunction with the CCA-based resonator. The experimental results confirmed the ability of the QFG to output stable wavelengths with the rotation angle from −20° to 20°, thereby validating the feasibility of this innovative approach.