Raman spectroscopy using multiple excitation wavelengths

Inventors

Chai, Ming • Yang, Wei • Lieber, Chad • Yang, Miao • Zhang, Charlie

Assignees

BaySpec Inc

Abstract

Raman spectrometers are provided that illuminate a sample with two or more different beams of light, each characterized by a different primary frequency. Scattered light from the sample is separated into multiple Raman spectra, one for each primary frequency. The multiple Raman spectra can be evaluated individually, or they can be added together to form a composite spectrum that is then evaluated.

Core Innovation

The invention relates to a Raman spectroscopy system in which multiple beams of light illuminate the same spot on a sample. Each beam has a spectral linewidth centered on a different frequency, and the system produces Raman spectra associated with each incident beam. The illumination system directs a first beam along a first optical path and a second beam along a different second optical path, so that multiple excitation frequencies are applied to the same sample location.

The detection system receives scattered light and produces multiple Raman spectra, one spectrum for each beam of light incident on the sample. The detection system includes a first optical detector and a second optical detector, in which the first optical detector comprises a silicon-based detector and the second optical detector comprises an indium-gallium-arsenide detector. Scattered light is separated by spectra separator optics into Raman spectra attributable to different excitation frequencies and detected via the corresponding detectors.

The system supports Raman results that can be matched to Raman spectra libraries and enables fluorescence reduction for substance identification by using difference-spectrum processing such as Shifted Excitation Raman Difference Spectroscopy (SERDS). Raman spectra can be combined by addition to form a composite spectrum or combined by subtraction to form a difference spectrum or a derivative spectrum, and the simultaneous multi-wavelength acquisition supports analysis of rapidly changing samples.

Claims Coverage

The independent claim includes three inventive features spanning illumination of the same sample spot with multiple excitation frequencies, producing multiple Raman spectra, and separating detection between two detectors.

The claim centers on illuminating the same sample spot with multiple excitation beams at different central frequencies and using a detection system configured to generate multiple Raman spectra, with detection separated across a silicon-based detector and an indium-gallium-arsenide detector.

Stated Advantages

Documented Applications