The influence of optical design on the signal to noise characteristics of polarimeters.
A high-frequency modulation technique is employed to reduce the sensitivity of an instrument to flicker noise. A 5-mW He-Ne laser is used as the source to achieve a high signal to shot-noise ratio. The high-frequency modulator acts as the limiting noise-source in the particular apparatus used, as a result of residual static birefringence in the optical head. An analysis of the origin of the modulator noise is given. The apparatus is tested with l(+)-tartaric acid. A rotation detection limit of 3 x 10(-4) degree is achieved (signal to noise ratio of 3:1).
Kankare
J J
JJ
Department of Chemistry, University of Turku, SF 20500 Turku 50, Finland.
Stephens
R
R