Carnahan, Jon W.
M.S. (Master of Science)
Department of Chemistry
Monochromator; Acoustooptics; Light deflectors
Acousto-optic deflectors (AOD) have the ability to change the direction of light passing through a transparent medium according to Bragg interactions. Acoustic waves are launched from transducers and travel through the medium. The acoustic waves act as a synthesized "grating" within the AOD. A beam of light is introduced to the acoustic medium, and interaction between the light beam and acoustic waves results in diffraction. Most work with AODs has been to modulate the direction of a laser beam. This work focuses on the application of an AOD as the dispersion element of a monochromator. Advantages to this system include rapid random access of wavelengths, rapid scanning and ruggedness due to lack of moving parts. Fundamental characterizations in terms of light dispersion, light beam spreading and angular acoustic spreading are investigated. Wavelength access range and spectral bandpass measurements were performed. Theoretical calculations to determine wavelength access range yield 267 nm. The data presented show wavelength access range of 100 ran. The discrepancy in values may be explained by decreased diffraction efficiency at lower applied frequencies and optical difficulties including focusing and Bragg angle requirements. Theoretical calculations to determine spectral bandpass produce values of 3 to 5 nm. The experimental spectral bandpass values averaged 60 to 80 nm. Factors that contribute to the large bandpass include light beam and acoustic wave "spreading," and low groove density within the acoustic medium. Presently, the AOD possesses many qualities useful in spectroscopy, but does not exhibit dispersion adequate for use in a monochromator where moderate resolution requirements are necessary.
Herrmann, Denise L., "Characterization studies of an acousto-optic deflector as a dispersion element of a monochromator" (1991). Graduate Research Theses & Dissertations. 1763.
vii, 70 pages
Northern Illinois University
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