Setup for measuring the optical propagation time in matter

TL;DR

This paper presents a simple, accurate, and fast method for measuring optical propagation time in matter using a lock-in amplifier, improving precision and ease over traditional techniques.

Contribution

The paper introduces a novel setup employing a lock-in amplifier for optical time-of-flight measurements, enhancing accuracy and operational simplicity.

Findings

Feasibility confirmed through primary experiments

Potential for high-speed, precise measurements of light velocity and refractive index

Advantages include easy sample preparation and rapid measurement process

Abstract

Optical propagation time in matter could reveal fruitful information, such as the velocity of light and the sample's refractive index. In this paper, we build a simple and robust setup for measuring the optical propagation time in matter for a known distance, the system uses high frequency square signal as the signal carrier, and a lock-in amplifier is employed to obtain the phase difference between the reference square signal and the other one penetrating the sample, in this way the optical time of flight in matter can be obtained by a background subtraction process. Primary experimental result confirms the feasibility of the newly proposed measuring theory, which can be used to measure easily in high-speed the speed of light and the refractive index of optical transparent material, compared with the currently popular measuring technique using oscilloscope, potential advantage of our proposed method employing lock-in amplifier is that high accuracy are promising, and in contrast with the presently most popular method for measuring the sample's refractive index based on the minimum deviation angle, superiority of our suggested method is the easy preparation of the sample, the convenient operability and the fast measuring speed.