Spectral analysis of light is a classic scientific method with many applications and supports numerous techniques and tools. Recently, significant improvements have been made in miniaturized spectrometers, which analyze light. However, there are still challenges to overcome before these smaller spectrometers can be used widely.
Researchers at UC Santa Cruz are developing ultra-small but powerful spectrometers. These devices could be used for various purposes, like detecting diseases or observing distant stars. Because they are cheaper to produce, they can be more accessible and tailored to specific needs.
The researchers have created a new, highly efficient spectrometer that can measure light with a wavelength resolution of 0.05 nanometers. This resolution is about 1.6 million times smaller than a human hair and matches what more significant, more expensive spectrometers can achieve.
Professor Holger Schmidt, a leading expert in light detection technology, noted that this performance is very impressive and competitive with traditional, larger devices.
Miniaturizing spectrometers is an essential area of research because traditional spectrometers can be very large and expensive, sometimes the size of a three-story building. Smaller spectrometers often don’t perform as well or are hard and costly due to the need for precise nanofabrication.
The UC Santa Cruz researchers have developed a compact, high-performance device that avoids these costly manufacturing issues. Their spectrometer uses a miniature waveguide on a chip to guide light in specific patterns based on color.
A machine learning algorithm analyzes Data from the chip that interprets these light patterns to reconstruct images accurately. This “reconstructive” spectrometry method is effective because the algorithms can work with less precise data and continuously improve their performance.
As a result, the researchers can produce these chips using more straightforward and cheaper fabrication techniques, completing the process in hours instead of weeks. The lightweight chips were designed at UCSC and made at Brigham Young University in collaboration with Professor Aaron Hawkins and his students.
Hawkins said, “Compared to more sophisticated chip design, this only requires one photolithography mask, making the fabrication much easier and faster. Someone with basic capabilities could reproduce this and create a similar device tuned to their needs.”
The researchers believe their new technology can be used in many ways, but they are currently focusing on creating powerful tools for astronomy. Because these devices are cheaper, astronomers can customize them for their specific needs, unlike with large, expensive instruments.
They are working on using these chips with the Lick Observatory telescope, starting with studying light from stars and later exploring other space events. With high accuracy, these devices could help scientists learn about the atmospheres of exoplanets and dark matter in faint galaxies.
Thanks to UC Santa Cruz’s experience in adaptive optics, the team is collaborating on capturing faint light from distant stars and galaxies and analyzing it with a miniaturized spectrometer.
Professor of Astronomy and Astrophysics Kevin Bundy said, “When you try to put something on a telescope and get light through it, you always discover new challenges — it’s much harder than just doing it in the lab. The beauty of this collaboration is that we have a telescope, and we can try deploying these devices on the telescope with a good adaptive optics system.”
In addition to astronomy, the research team has shown that their tool can detect fluorescence, a noninvasive imaging method useful in medical fields like cancer screening and disease detection.
They also plan to develop the technology for Raman scattering analysis, which helps identify specific molecules, such as drugs in the body or environmental pollutants. This method is easy to use and doesn’t require heavy equipment, making it practical for fieldwork.
The researchers found that multiple compact waveguides can be placed together to enhance performance, with each chip measuring different light spectra for more detailed information. They demonstrated this with four waveguides but believed that hundreds could work together. This is the first device to use multiple chips in this way, and the team will continue to improve its sensitivity for even better results.
Journal Reference:
- Md Nafiz Amin, Vahid Ganjalizadeh, Tyler J. Adams, Porter B. Dixon, Zoe Weber, Matthew DeMartino, Kevin Bundy, Aaron R. Hawkins, Holger Schmidt; Multi-mode interference waveguide chip-scale spectrometer (invited). APL Photonics 1 October 2024; 9 (10): 100802. DOI: 10.1063/5.0222100
