Title

Acquiring First-Order Coherence Measurements for a HeNe Gas Laser Using a Michelson Interferometer

Document Type

Oral Presentation

Campus where you would like to present

Ellensburg

Event Website

https://digitalcommons.cwu.edu/source

Start Date

15-5-2019

End Date

15-5-2019

Abstract

A HeNe laser was used as a source in a Michelson interferometer apparatus to develop a process for making quantitative coherence measurements of the laser light. While investigating these measurements, interesting phenomena were observed that appeared to be associated with multiple wavelengths of light. When scanning the length of the interferometer arm, an interference pattern that correlated with the 14 cm length of the laser cavity was found. A periodic shift between almost complete constructive and destructive interference occurred every 14 cm down the arm, but was absent in between. We attempted detection of a beat frequency from the laser which yielded no results until a polarizer was placed in front of the laser, and at two angles perpendicular to each other the polarizer almost completely extinguished the laser light. To see the beat frequency required the polarizer to be 45 degrees relative to these polarization angles of the light. The beat frequency and polarizer adjustments therefore showed two different wavelengths and polarizations of light coming from the laser which alternate periodically, suggesting that the laser was scanning between two orthogonally polarized wavelengths as it operated. The rate at which the laser flipped between wavelengths was strongly correlated with the rate of shift in the interference pattern, providing strong evidence for their relationship with the coherence measurements.

Faculty Mentor(s)

Michael Braunstein

Department/Program

Physics

JensenJe Acquiring First-Order Coherence Measurements on a HeNe Laser D.pptx (121538 kB)
Slides for SOURCE 2019 presentation Jensen

Additional Files

JensenJe Acquiring First-Order Coherence Measurements on a HeNe Laser D.pptx (121538 kB)
Slides for SOURCE 2019 presentation Jensen

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May 15th, 12:00 AM May 15th, 12:00 AM

Acquiring First-Order Coherence Measurements for a HeNe Gas Laser Using a Michelson Interferometer

Ellensburg

A HeNe laser was used as a source in a Michelson interferometer apparatus to develop a process for making quantitative coherence measurements of the laser light. While investigating these measurements, interesting phenomena were observed that appeared to be associated with multiple wavelengths of light. When scanning the length of the interferometer arm, an interference pattern that correlated with the 14 cm length of the laser cavity was found. A periodic shift between almost complete constructive and destructive interference occurred every 14 cm down the arm, but was absent in between. We attempted detection of a beat frequency from the laser which yielded no results until a polarizer was placed in front of the laser, and at two angles perpendicular to each other the polarizer almost completely extinguished the laser light. To see the beat frequency required the polarizer to be 45 degrees relative to these polarization angles of the light. The beat frequency and polarizer adjustments therefore showed two different wavelengths and polarizations of light coming from the laser which alternate periodically, suggesting that the laser was scanning between two orthogonally polarized wavelengths as it operated. The rate at which the laser flipped between wavelengths was strongly correlated with the rate of shift in the interference pattern, providing strong evidence for their relationship with the coherence measurements.

https://digitalcommons.cwu.edu/source/2019/Oralpres/17