Researchers are developing new methods to create extremely small yet powerful spectrometers, which can have applications ranging from disease detection to observing stars in faraway galaxies.
Spectrometers, a technology for analyzing light, originate from the time of the renowned 17th-century physicist Isaac Newton. These devices function by separating light waves into their individual colors—or spectra—to reveal insights into the properties of the objects being examined.
At UC Santa Cruz, scientists are working on innovative approaches to produce spectrometers that are not only compact but also highly efficient, making them suitable for a variety of uses, including medical diagnostics and astronomical observations. The economical manufacturing process makes these devices more readily available and adaptable for specific uses.
The research team, comprising UC Santa Cruz Professor of Electrical and Computer Engineering Holger Schmidt and Professor of Astronomy and Astrophysics Kevin Bundy, has published their findings in the respected journal APL Photonics.
The researchers showcase a groundbreaking spectrometer with an impressive wavelength resolution of 0.05 nanometers—approximately 1.6 million times thinner than a human hair, offering the same level of resolution as much larger devices that are 1,000 times their size.
“Essentially, this matches the performance of large, conventional, expensive spectrometers,” explained Schmidt, the lead author on the paper and a seasoned expert in light detection chip technology. “This is quite remarkable and highly competitive.”
Miniature devices
The miniaturization of spectrometers is an active research area since these instruments are vital in numerous fields but can range in size to that of a three-story building and carry hefty price tags. Nevertheless, smaller spectrometers typically do not perform at the same level as their larger counterparts, and they can be challenging and costly to manufacture due to the need for precise nanofabrication.
The UC Santa Cruz team has developed a device that achieves high performance without the expensive production methods typically involved. Their creation is a small, powerful waveguide affixed to a chip that directs light into specific patterns based on color.
Data from the chip is processed using a machine-learning algorithm that interprets the light wavelength patterns to reconstruct the image with remarkable accuracy—this technique is referred to as “reconstructive” spectrometry.
This approach ensures precise outcomes because the machine learning algorithms do not need exceptionally precise inputs to identify light patterns and can continuously enhance their performance by optimizing to the hardware.
Thus, the researchers can produce the chips using relatively simple and cost-effective manufacturing methods, with processes that take hours rather than weeks. The lightweight, compact chips were designed at UCSC and crafted and refined with the help of Professor Aaron Hawkins and his undergraduate team at Brigham Young University.
“This process is straightforward compared to more complex chip designs, requiring just one photolithography mask, which significantly simplifies and speeds up the fabrication,” Hawkins noted. “Someone with basic capabilities could reproduce this and create a similar device tailored to their needs.”
Reading the stars
The researchers foresee a plethora of potential applications for this technology, focusing initially on developing powerful tools for astronomy. Their reasonably priced devices would allow astronomers to customize them for specific research goals, a feat that is nearly impossible with larger instruments that can cost millions.
The research team aims to make these chips functional on the UC-operated Lick Observatory telescope, starting with capturing light from stars and later expanding to other astronomical phenomena. With such precision, astronomers could delve into understanding aspects like the atmospheric composition of exoplanets or exploring dark matter in faint dwarf galaxies. The low cost of these devices would facilitate their adaptation for researchers’ unique needs, which is often unattainable with traditional equipment.
Using UC Santa Cruz’s extensive experience in adaptive optics systems for astronomy, the researchers are collaborating to find effective methods to capture the faint light from distant celestial bodies and channel it into the miniaturized spectrometer.
“In astronomy, integrating a device onto a telescope and acquiring light through it presents unexpected challenges—it’s much more complex than lab work. The advantage of this collaboration is that we actually have a telescope, allowing us to test these devices with a robust adaptive optics system,” Bundy explained.
Uses for health and beyond
Aside from astronomy, the research also highlights the tool’s capability for fluorescence detection, a non-invasive imaging technique valuable for various medical applications, including cancer detection and identifying infectious diseases.
In the future, they plan to enhance the technology for Raman scattering analysis, which utilizes light scattering for identifying unique molecules—commonly employed in specialized tests to detect specific substances, such as drugs in the human body or environmental pollutants. Given its straightforward design, the device would be practical and sturdy for fieldwork.
The researchers also illustrate that compact waveguides can be arranged in tandem to improve the system’s performance, with each chip capable of measuring different spectra, thus providing additional data about the observed light. While they currently demonstrate the efficacy of four waveguides working together, Schmidt envisions a scenario with hundreds of chips operating simultaneously.
This is the first instance of using multiple chips concurrently in this manner. The research team will continue to refine the device’s sensitivity to achieve even higher spectral resolution.
