What is it about?
Many experiments need multiple lasers. Sometimes we only need to stabilize the frequencies so that the laser frequency doesn't move around. Other times we need to both controllably and repeatably change the frequency of the lasers. This paper describes a technique to both stabilize and control the frequency of two laser beams to a single device (an optical cavity). We discuss the basic theory as well as limitations and methods to overcome those limitations.
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Why is it important?
Many spectroscopy experiments require us to controllably scan the frequency of a laser over a large frequency range. A common method for doing this is something called dual frequency modulation, which uses an optical cavity as a frequency reference point. This method works well when you are trying to stabilize and control a single laser beam; it allows the frequency scanning of a laser to half of the free spectral range of the cavity. Trying to use this technique for independently stabilizing and controlling the frequency of two laser beams introduces a lot of issues. This paper talks about those issues and how to design your experiment to minimize or eliminate many of these issues.
Perspectives
Admittedly, the technique described in the paper is really only useful to those who are doing multi-photon spectroscopy. However, we also wrote this paper with the intent that the contents be extremely accessible to young scientists. As an example, the paper steps through the math for single, dual, and triple frequency modulation with the intent that the steps and explanations be accessible to undergraduate and early career graduate students. Many young scientists are curious about how one expands a complex exponential as a series of Bessel functions. This is the first paper I know of that tells the reader this is the Jacobi–Anger expansion allowing them to Google and learn more. The entire paper was written with this intent.
Will Williams
Smith College
Read the Original
This page is a summary of: Pulsed triple frequency modulation for frequency stabilization and control of two lasers to an optical cavity, Review of Scientific Instruments, August 2020, American Institute of Physics,
DOI: 10.1063/5.0010085.
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