TECHNIQUE TO DISCRIMINATE AGAINST AMBIENT AND SCATTERED LASER LIGHT IN RAMAN SPECTROMETRY

摘要

Raman scattering, while a powerful and versatile technique, relies of the detection of weak signals. Detecting the signal can be difficult if there is interference, especially if the interference comes from scattered stray light of the laser used to generate the Raman signal. Described here is a frequency modulation technique in combination with heterodyne detection that simultaneously rejects interference from ambient light as well as from scattered stray laser light. This provides a means to detect Raman signal and discriminate against scattered light without using an expensive and bulky spectrometer.

主权项

1. A Raman spectrophotometer comprising:
a tunable laser; a wavelength modulation controller coupled to the laser, wherein the wavelength modulation controller modulates the tunable laser frequency; a measurement region optically coupled to the tunable laser, wherein a sample is disposed in the measurement region; a signal collection region optically coupled to the measurement region, wherein the signal collection region collects scattered light from the measurement region; a filter optically coupled to the signal collection region, wherein the filter selectively transmits light of a predetermined wavelength; and a heterodyne detection system, wherein the heterodyne detection system comprises a lock-in amplifier, electrically coupled to the wavelength modulation controller, wherein the lock-in amplifier is synchronized with the modulation of the tunable laser by the wavelength modulation controller.