Precision Measurement of Material and Optical Properties Using Interferometry

Team Members

Yang SangUk

Zhang ShunYang

Xu Zifang

List of Apparatus

Light source: 780nm laser diode (GH0781RA2C SHARP diode) with LT230-B collimation tube

Optics: optical isolator (Thorlabs IO-3D-780-VLP), beamsplitter, two 25.4mm broadband dielectric mirrors (BB1-E02-10)

Salt water of different concentrations in a transparent container (for determining the refractive index of solutions of different concentrations)

Powermeter

Introduction

Idea

We will be constructing an interferometer as a tool for precision measurement. One primary objective is to determine the refractive index of the solutions of different salt concentrations by analyzing the resulting shift in interference fringes. Additionally, the thermal expansion of the metal sample will be measured by monitoring changes in the optical path length as the temperature of the sample varies. The project will highlight the relationship between wave optics and measurable physical parameters and illustrate the advantages of high-precision experimental technique.

Experiment setup & procedures

A basic Michelson interferometer will be constructed for the experiment.

Procedure:

1. Construct the Michelson interferometer and verify the presence of interference fringes.

OI: optical isolator; M: mirror; BS: beam splitter; PM: powermeter

Oscilloscope Measurement without Sample (Low Pass Filter applied)

Oscilloscope Measurement with Intentional Noise created (Without Sample)

2. Refractive index measurement Place the test solution in one arm of the interferometer. Gradually vary the solution concentration by adding either distilled water or a higher-concentration solution to the container, and observe the resulting changes in the interference pattern.

3. Thermal expansion measurement To investigate the thermal expansion of the mirror, slowly heat one of the mirrors using a heating resistor. The temperature will be monitored with a thermocouple. Record how the interference pattern changes as the temperature increases.

References

[To be added]