Grating Spectrometer (GS)

A grating spectrometer, or grating-based spectrometer, is a simple diffractive system for discriminating and detecting different wavelengths (spectrum) of a broadband light. The simplicity of the system comes with the cost of a limited spectral bandwidth and spectral resolution; however, for specific applications can be a good candidate. The following figure shows a simplified example of a grating spectrometer. The output beam of a broadband source (a Supercontinuum Source in this case) is coupled to a multipass cell containing the gas sample to increase the interaction length between the sample and the light, increasing the detection sensitivity of the system. Afterward, the beam is aligned to a reflection diffraction grating, which diffracts different wavelengths of the beam into different directions. Finally, a single photodetector is used to detect the light. By rotating the grating, different parts of the spectrum reach the detector, and the spectrum of the source and the sample gases can be recorded sequentially. The grating-based spectrometers in our group are applied in several systems, among which are the automated gas detection systems deployed at fruit storage facilities [1,2].

Set-up of a grating spectrometer.

References

1. K. E. Jahromi, Q. Pan, A. Khodabakhsh, C. Sikkens, P. Assman, S. M. Cristescu, P. M. Moselund, M. Janssens, B. E. Verlinden, and F. J. M. Harren, "A Broadband Mid-Infrared Trace Gas Sensor Using Supercontinuum Light Source: Applications for Real-Time Quality Control for Fruit Storage," Sensors 19(10), 2334 (2019).
2. K. E. Jahromi, M. Nematollahi, R. Krebbers, M. A. Abbas, A. Khodabakhsh, and F. J. M. Harren, "Fourier transform and grating-based spectroscopy with a mid-infrared supercontinuum source for trace gas detection in fruit quality monitoring," Opt. Express 29(8), 12381–12397 (2021).