Equipment:

The Burleigh wavemeter measures wavelengths of incident light using an internal Michelson interferometer.  The Michelson interferometer splits the incident wavelength with a partially silvered mirror.  The split beam travels down two separate paths, one fixed and one variable.  At the end of each path is a mirror that reflects light and recombines such that the single beam output is a superposition of the two wavelengths.   As the variable path length is changed, the superposition demonstrates either destructive or constructive interference depending on the variable path length.  A path length of nl/2  results in constructive interference because the light travels a length of 2L, as it goes back and forth along the length of the path, to end up in phase with the other beam along the fixed path.  As the position of the mirror varies, a sine wave is created as the signal alternates between constructive and destructive interference.  The data that resulted from the stepping of the mirror was sent as a digital output to an oscilloscope.  The time scale on the oscilloscope represents the changing path length of the variable mirror in the wavemeter.  Calibration was achieved knowing that the fringe spacing is l/2 for a single mode oscillation for 55mA at 636.78nm.   We used this calibration to look at our beats in the analysis (see data).

The above diagram shows both experimental set-ups used.  The first did not include the spectrometer; the light from the laser was incident on the side of the wavemeter.  For the second, the spectrometer intercepted and received the laser light for scanning. 

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