Monday, February 20, 2006

Week of 1-23-06

The following project tasks were completed this week:

Using the method discovered the previous week, high frequency sinusoidal modulation was achieved using an optical chopper wheel. It should be noted however, that a true sinusoid was not obtained, rather, a close approximation to ideal modulation was achieved. The sinusoidal approximation was sufficient between approximately 30 – 100Hz. Testing was done by using an argon laser operating at 488nm and picking up the modulated beam signal using a Newport detector and an oscilloscope. The results of these initial modulation tests indicated that using the chopper wheel is a viable option for high frequency modulation, but was not feasible for lower frequency modulation of approximately 10Hz.

Methods for low frequency modulation were further investigated. John Korah of Colorlink was contacted to follow up on a question previously asked regarding their liquid crystal (LC) attenuators. John mentioned that for our application, a device could be built specifically to achieve our modulation needs using a LC retarder device, a component of many of their optical attenuators. I suggested that John and Colorlink’s product engineer Gary Sharp meet with Dr. Blair at a conference in San Jose that they would all be attending the week of the 30th so Dr. Blair could see the device John was describing and be able to confirm that it would work in our application.


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