Spectroscopic analysis is one of the most widely used analytical tools across both scientific research and industry. Miniaturization of spectroscopic systems enables a wide range of handheld, portable, and integrated applications, where minimizing size, weight, cost, and power consumption are essential. Prof. Zongyin Yang, is dedicated to miniaturizing spectroscopic light sources and detectors. He contributed valuable advancements in this field, such as inventing the world’s smallest spectrometer, developing the widest wavelength-tunable nanolaser, and being the first to propose synthesis methods for bandgap-graded semiconductors.
Figure 1 Summary of Zongyin’s research works
1. Invented the world's smallest spectrometer
Spectrometers serve as detectors for spectroscopic systems. Conventional spectrometers typically rely on a combination of bulky dispersive optics, long optical path lengths, detector arrays, and movable parts. These designs face fundamental limitations due to adverse effects of shrinking their optical components or path lengths. There are certain scientific and technical challenges that need to be addressed for minimizing spectrometers.
Innovation: Zongyin proposed a new paradigm for the miniaturization of spectrometers, where light dispersion and detection are carried out in an individual nanomaterial structure, representing a platform unmatched in both simplicity and its compact design. Zongyin has published two papers in Science as the first author in the field of miniaturization of spectrometers (one is a research paper and the other one is a review). Zongyin demonstrated the world's smallest spectrometer based on the proposed principles. The active element of the spectrometer, where light is both detected and spectrally resolved, is scaled down to a single compositionally graded nanowire, just hundreds of nanometers in diameter and tens of micrometers long. This is smaller than the diameter of human hair. The system functions without any complex optics or filters; incident spectra are reconstructed from spectral response functions and photocurrents are measured using a series of electrodes along the nanowire. Despite having such a simple structure, the device is capable of accurate monochromatic and broadband light reconstruction, as well as spectral imaging from centimeter-scale image planes down to lensless, single-cell scale in-situ mapping. This spectrometer concept could open novel opportunities for almost any miniaturized spectroscopic application, including lab-on-a-chip systems, drones, implants, and wearable devices.
Figure 2 (a) shows photographs and micrographs of a nanowire spectrometer. The size of the sensor is tens of microns only, and the dimensions of the packaged chip are less than 1 cm. Figure 2 (b) illustrates the working principle of the nanowire spectrometer. Figure 2 (c) displays the cover of the microspectrometer review paper. It was the first that classified the miniaturized spectrometers into four categories: dispersion optics, narrow-band filters, Fourier transform and computational spectrum.
As the first author, Zongyin wrote in 2021 a review on microspectrometers for Science. This article standardized the terminology, reviewed the development, and proposed opportunities in microspectroscopy. This article has attracted considerable attention from academia and industry.
The University of Cambridge reported this research on its homepage under the title "Nanowires replace Newton’s famous glass prism." This research work is introduced in many books, such as "Computer vision".
Zongyin further developed and commercialized miniaturized spectrometers and produced spectral cameras that can be integrated into smartphones. A wide range of applications can benefit from such a spectral camera, including non-destructive food and drug testing, biological testing, health diagnostics, and camouflage recognition.
As the first author, Zongyin wrote in 2021 a review on microspectrometers for Science. This article standardized the terminology, reviewed the development, and proposed opportunities in microspectroscopy. This article has attracted considerable attention from academia and industry.
The University of Cambridge reported this research on its homepage under the title "Nanowires replace Newton’s famous glass prism." This research work is introduced in many books, such as "Computer vision".
Zongyin further developed and commercialized miniaturized spectrometers and produced spectral cameras that can be integrated into smartphones. A wide range of applications can benefit from such a spectral camera, including non-destructive food and drug testing, biological testing, health diagnostics, and camouflage recognition.
Figure 3 shows the technical improvement and commercialization of miniature spectrometers. Figure 3 (a) specifies the development from the first-generation nanowire spectrometer reported in Science to the thin-film spectral cameras, which was a major leap in spectral resolution and sensitivity. Figure 3 (b) indicates the tests done using a Huawei P9 mobile phone to realize line-scan spectral imaging.
In addition to the innovation in the field of spectroscopic detection, Zongyin has made several breakthroughs in other parts of the spectroscopic system.
2. Developed nanolasers with the world's widest tunable wavelength range
Innovation: Wavelength-tunable laser can perform as spectroscopic light source. Zongyin proposed the use of bandgap-graded semiconductor materials as variable laser gain and demonstrated the world's widest wavelength-tunable nanolasers. This research was published in the prestigious scientific journal Nano Letters with Zongyin as the first author. A review in Nature Reviews Materials cited and evaluated this work, "This is an important method for realizing wide-spectrum tunable nanolasers." This tunable laser not only has a wide, adjustable range, but also has a small footprint. In addition, it can be used in optical communications, the military, and for environmental monitoring.
Figure 4 displays a schematic diagram of (a–e) wavelength-tunable nanolasers by cutting off the bandgap-graded nanowires. Figure 4(f) shows continuous wavelength-tunable nanolasers.
3. Proposed synthesis methods for bandgap-graded semiconductors
Innovation: Bandgap-graded semiconductor materials lay the research foundation for miniaturized spectrometer and wavelength-tunable nanolasers. Zongyin initiated two methods to synthesize bandgap-graded materials: the source-moving and substrate-moving synthesis. The methods and results were published in the respected journals Nano Letters and Journal of the American Chemical Society with Zongyin as the first author.
Figure 5a and 5c display schematic diagrams of source-moving and substrate-moving synthesis methods, respectively.