# 5.1: Pre-lab Exercises

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## Electro-optic, Acousto-optic and Photorefractive Light Modulation

The Pre-Lab Exercises must be completed BEFORE entering the Lab. In your lab notebook record data, explain phenomena you observe, and answer the questions asked. Remember to answer all questions in your lab notebook in a neat and orderly fashion. No data are to be taken on these laboratory sheets. Tables provided herein are simply examples of how to record data into your laboratory notebooks. Expect the in-lab portion of this exercise to take about 4 hours. You may do Exercises 5.1 – 5.3 this week and Exercise 5.4 next week.

### PL5.1 - Get Prepared to Start the Laboratory Exercises

Read the entire laboratory handout, and be prepared to answer questions before, during and after the lab session. Determine all the equations and constants that may be needed in order to perform all the laboratory exercises. Write them all down in your laboratory notebook before entering the Lab. This will ensure that you take all necessary data while in the Lab in order to complete the lab write-up. This preparatory work will also count toward your Lab Exercise grade. In the electro-optic light modulation exercise we will be setting up an optical (wireless) communications system (see Exercise 5.26). If you have a CD-player and a CD you would like to use as an input source of music for transmission over the laser beam, bring it with you on Lab day.

### PL5.2 (optional)

In exercise 5.24, you are asked to perform an optical communication system demonstration. For this exercise, you will be using a beam modulated in spatial frequency (the light will sweep back and forth across a distant screen at the same frequency as an audio signal input). However, using this form of spatial light modulation is not conducive to high-fidelity audio (since a detector is very small in comparison to the size of the beam swath – you will hear a series of clicks instead of a clear, smooth audio waveform from the detector/speaker assembly). Using optical components that you are already familiar with, describe (mathematically if necessary) how to convert the spatial frequency modulation into an amplitude-only modulation. Design the system that replaces the black box below.

This page titled 5.1: Pre-lab Exercises is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by David Dunmeyer (MIT OpenCourseWare) .