Accurate measurements of refractive indices for dielectrics in an undergraduate optics laboratory for science and engineering students

Abstract

Based on our novel method recently published in the Am. J. Phys. 77 337-43 (2009) for finding precise values of the indices of refraction for dielectrics from measurements of the polarized light reflected by the surface, in this paper we propose an improved technique for finding Brewster angles with a better precision, of 0.001 • , using the same relative inexpensive optical equipment provided by the PASCO Scientific company and a simpler setup. The goal is to implement our procedure in a 3 h optics laboratory for undergraduate students using two different laser-dielectric systems. As compared to our previous work, now we eliminate the random fluctuations of the experimental time-dependent reflectance by controlling the irradiation time on the dielectric surface (and thus avoiding the overheating of the surface) and by using lasers which are stable during the data acquisition process. Also, in the present experiment, we use a computer-based filtering procedure of the experimental reflectance during the data acquisition process for increasing the precision of the measurements at any angle of incidence.

A New Optoelectronic Switch: The Dielectric of a Capacitor Illuminated with a Laser Radiation

“…Hence we have to process data collected only between 10 to 15 seconds. Our technique allows finding Brewster angles with a precision of 0.001˚ which is 100 times better [4] than measurements using similar equipment [3].…”

“…For stability purposes, throughout the experiment we have collected raw data for at least 15 seconds following the conclusions previously published by Hsu and Bahrim in [4]. Figure 3 shows a test case for the variation of the angular value with the stability of the reflectance detected.…”

Measuring the refractive index and thickness of a thin film: an optical polarization experiment

“…Fresnel reflection equations describe the amplitude reflection coefficients of p-and s-polarized light. There are quite a number of elegant experimental projects that introduce the topic, such as: investigating the Fresnel reflection [1][2][3], measuring the Brewster angle of a sample, and calculating the refractive index [4][5][6]. In our laboratory, after studying the Fresnel reflection and measuring the Brewster angle, students are given a sample of thin film and they are required to determine the refractive index and thickness of the film using the same apparatus.…”