Spectrometers are widely used for applications such as chemical analysis, remote sensing, quality control, environmental monitoring, spaceborne measurements, and optical measurements. Most spectrometers are based on using dispersive elements such as prisms, gratings, or etalons. These spectrometers typically have moving parts that induce spurious readings due to vibrations, and have limited use due to their limited spectral range and resolution capabilities, which in turn limit their use when needed for portable field applications.

The vibration-insensitive, robust spectrometer for remote applications.

Acousto-optical tunable filters (AOTFs) are very powerful tools that can be used in many spectroscopic applications, including absorption, emission, fluorescence, Raman, and laser-induced breakdown spectroscopy (LIBS) measurement instruments, and inside a traditional or fiber laser cavity for choosing and tuning frequency of light radiation. They are lightweight, compact, and very useful for field-portable applications. They have no moving parts, are all solid-state construction, require low power, and are insensitive to vibrations. They have high spectral resolution, large field of view, and high throughput. They offer high-speed tuning and scanning of wavelengths, and have reliable and reproducible operation under computer control.

An ongoing problem in using spectrometers in more applications is their miniaturization. The size of a spectrometer is limited by their required precision and accuracy of measurements because of existing relationships between optical spectral resolution, spectral range of a spectrometer, and its inherent physical dimensions. The optical spectral resolution of commonly manufactured spectrometers is proportional to their dimensions. This is an important limitation for miniaturization of spectrometers that generally cannot be circumvented. Unfortunately, since precise spectrometers for use in environmental analysis are often bulky, costly, and expensive to transport and install, many known and important applications of spectrometers remain unimplemented due to cost and/or inconvenience.

Thus, there is a need for a portable AOTF spectrometer system that is relatively less expensive compared to currently available systems that can be produced and packaged for field handheld use by non-experts.

An AOTF-based spectrometer was developed that can be used for a variety of spectroscopy applications including absorption, emission, fluorescence, Raman, and laser-induced breakdown spectroscopy.

The spectrometer is electronically tunable with no moving parts, lightweight, compact, and very useful for field-portable applications. Its solid-state construction means it can operate with low power, it is insensitive to vibrations, and it runs under computer control. Moreover, it can provide high spectral resolution.

The AOTF spectrometer has several advantages over alternative spectrometer designs based on filter wheels, diffraction gratings, and Michelson interferometers. It is small, fast, reliable, and can be used for applications such as chemical process control, medical diagnostics, spectral radiometry, and real-time composition analysis in a production/manufacturing environment. This instrument fulfills an essential requirement for next-generation spectroscopic instruments.

Military and commercial applications include detection of chemical and biological agents, medical and pharmaceutical applications, production and manufacturing control, and environmental sensing applications.

For more information, contact Dr. Brian Metzger at This email address is being protected from spambots. You need JavaScript enabled to view it.; 406-994-7782.

Tech Briefs Magazine

This article first appeared in the December, 2018 issue of Tech Briefs Magazine.

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