Testing Lasers with a High-Resolution Spectrometer

A spectrometer with a sub-nanometer resolution that can see your laser's spectral fingerprint and watch it change colors.

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Spectrometry is the deconstruction of a light wave into its constituent colors. This class of tools range from simple prisms, to space telescopes. This particular spectrometer shines light through a grating and detects an interference pattern from path difference. This will separate the light based on wavelength.

Lens-Grating-Lens is a spectrometer configuration that collimates light from a slit or point source, sends that column of light through a holographic grating, then focuses the output on the grating onto a the detector. By illuminating as many lines as possible, and setting the second focal length very far, this spectrometer can detect the separation between laser harmonics.

Although lasers are accepted as monochromatic sources, the light they emit is spread among several harmonics across a band of visible light. Inside the semiconductor cavity of a laser diode, standing electromagnetic waves reflect internally until they emit out of the laser as in-phase light.


Video of a current sweep of the laser diode that shows the spectral lines move across the ccd matrix.

MPEG-4 Video - 13.86 MB - 08/20/2020 at 23:37



Contains file for laser cut components. Check bulkheads for alignment.

svg+xml - 16.35 kB - 08/20/2020 at 23:33


  • 1 × RaspberryPi Zero W Any Pi works as long as it accesses the camera
  • 1 × PiCamera
  • 1 × 8020 Aluminum Extruded Rail Including hardware (nuts and bolts)
  • 1 × 1.0 Diopter Welding Magnifying Lens Other focal lengths give different results
  • 1 × 1000 lines/mm holographic grating A cardboard grating cards

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