A radio frequency tagging continuous-wave optical spectrometer with megahertz refreshing rate

• Main Authors: Ren, Xiaojing, Hsieh, Chao-Mao, Malik, Mohammad O. A., Su, Joshua Weiming, Liu, Quan
• Other Authors: School of Chemical and Biomedical Engineering
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Electrical and electronic engineering; Beat Signal Measurements; Fourier Transform
• Online Access: https://hdl.handle.net/10356/170744
• Institution: Nanyang Technological University

Optical spectrometers capable of fast spectral measurements are useful in many fields spanning from industrial manufacturing to scientific research. However, conventional spectrometers, especially those applicable to continuous-wave light measurements, are limited in speed due to the need of taking multiple measurements sequentially and/or direct current (dc) detection that are subject to noise influence. We report a new radio frequency (RF) tagging spectrometer, which breaks these limitations and dramatically accelerates measurements. In this new spectrometer, an acousto-optic deflector (AOD) is used to encode the intensity at each wavelength to the amplitude of a different beat RF signal. As a result, all RF signals can be summed up and detected simultaneously by a fast single-channel detector. The spectrum is obtained by taking the Fourier transform of the summed RF signal. The spectrometer is evaluated by measuring both multiline and broadband light sources with a speed up to 1 MHz as well as light scattering spectra with a speed of 64 kHz. With the ability to select wavelengths by programming the driving RF signal, the spectrometer offers great flexibility to detect part of a spectrum that contains most useful information with an unprecedented speed limit up to multiple megahertz.