Mary Masterman - Oklahoma Biological Survey - University of ...

Abstract
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Previously a low-resolution, classical spectrograph with a resolution of about 700 and a spectral range of about 200 nm was
constructed.
A Raman system was built for the above spectrograph. It used a green 532 nm laser to stimulate Stokes scattering in samples.
The laser beam was reflected off a dichroic mirror at an angle of 90°. A microscope objective then focused the laser beam onto the
sample and collimated the returning light. Light of the laser wavelength was filtered out by an interference filter that reduced the
laser signal by approximately 10 5 . A 50 mm f.l. lens then focused the waveshifted light on the entrance slit of the spectrograph.
Measured wavenumbers correlated well to those in published spectra. Difficulties included false spectral lines created by the
multimode laser and fluorescence in many samples.
A Littrow spectrograph was then constructed. A medium-format 200 mm lens was used as a combined collimation and camera
lens. A body, utilizing a diagonal mirror, connected the lens with the camera. The modular design facilitated interchanging of the
lens, camera, and grating holder with different models. An adjustable slit was created, with light entering through a standard SCTthread
adapter. The spectrograph could be mounted directly to the Raman head or used in other applications, including astronomy.
The F/4.8 spectrograph had a resolution of 6500 and a spectral range of 80 nm with a 1200 l/mm grating. The spectrograph was
tested with a consumer DSLR camera as well as a cooled CCD camera.