Ultra-compact spectrometer offers the capabilities of much larger devices

Ultra-compact spectrometer offers the capabilities of much larger devices
by Clarence Oxford
Los Angeles CA (SPX) Oct 24, 2024

Spectrometers, which analyze light by breaking it down into different spectra, have a long history dating back to the 17th century. Now, UC Santa Cruz researchers are pioneering ultra-compact versions of these devices that maintain powerful performance at a fraction of the size, paving the way for applications in fields ranging from disease detection to space observation. Not only are these devices highly effective, but they are also inexpensive to produce and can be customized for various specialized uses.

Led by UC Santa Cruz Professor Holger Schmidt and Professor Kevin Bundy, the research team published their findings in *APL Photonics*, showcasing a spectrometer capable of achieving a wavelength resolution of 0.05 nanometers - comparable to that of devices 1,000 times larger.

"That's essentially as good as a big, standard, expensive spectrometer," said Schmidt, highlighting the competitiveness of this compact design.

Advancing miniature spectrometers
Miniaturizing spectrometers has long been a challenge due to the complexity and cost of achieving high performance in small packages. UC Santa Cruz's solution circumvents this with a chip-based device that utilizes a waveguide to direct light and machine learning algorithms to interpret the data. This reconstructive spectrometry approach enables precise analysis of light without requiring the precise nanofabrication of other miniature devices, significantly lowering production costs and time.

The team collaborated with Professor Aaron Hawkins and his students at Brigham Young University to fabricate the chips using a simplified process that requires only a single photolithography mask. "Someone with some basic capabilities could reproduce this and create a similar device tuned to their own needs," explained Hawkins.

Applications in astronomy and beyond
Initially, the researchers are focusing on astronomy, where the affordability of these devices allows for specialization in research that would otherwise be prohibitively expensive with traditional large-scale instruments. They aim to integrate their technology into the UC-operated Lick Observatory telescope, enabling detailed studies of phenomena like exoplanet atmospheres and dark matter in dwarf galaxies.

"In astronomy, when you try to put something on a telescope and get light through it, you always discover new challenges," said Bundy. "The beauty of this collaboration is that we actually have a telescope, and we can try deploying these devices on the telescope with a good adaptive optics system."

The potential applications extend beyond space, with the team already demonstrating the device's use in medical imaging techniques like fluorescence detection. Future developments could include Raman scattering analysis, which would enable the detection of specific molecules, such as drugs or pollutants, making it an invaluable tool for environmental monitoring and medical diagnostics.

The researchers also showcased how combining multiple chips enhances system performance. By aligning several waveguides, they provide greater spectral data in their analyses. In their current study, four chips were combined, but Schmidt envisions scaling this to hundreds of chips for even more powerful spectral resolution.

Research Report:Multi-mode interference waveguide chip-scale spectrometer