Full company details
MKS Ophir
Unit of MKS Instruments Inc.
Light & Measurement
3050 North 300 West
North Logan, UT 84341
United States
Phone: +1 435-753-3729
Fax: +1 435-753-5231
Toll-free: +1 866-755-5499
Working in the Basement: Measuring Signals Below the Noise Floor with a Lock-In Amplifier
Author: Shimon Elstein, Senior Physicist, Ophir
Friday, January 26, 2018
Measuring optical signals in the femtowatt (10-15) to nanowatt (10-9) range can be a daunting task. Signal levels
this low are lost in typical detector noise levels and swamped by background light. The noise floor for
photodiode detectors operated with a small bandwidth (~10 Hz) is on the order of 1 picowatt (10-12). Further
narrowing of the bandwidth by filtering or averaging will only provide a small additional reduction in the noise
level. In order to achieve significant improvements in noise rejection we need to turn to a lock-in amplifier. Here’s how.
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