Research Group and Collaborators Successfully Develop Visible-Light Vector Spectrum Analyzer

Research Content 

As the primary spectral band for human visual perception, visible light has played a central role in scientific exploration and technological development since the dawn of civilization. Currently, cutting-edge fields such as augmented reality/virtual reality (AR/VR), biosensing, and atomic, molecular and optical (AMO) physics have placed unprecedented demands on the precise manipulation and measurement of visible light. Particularly in optical atomic clock research, many key transition frequencies lie within the visible-light range. High-precision measurement of these frequencies not only contributes to breakthroughs in fundamental physics research but also is  profoundly transforming modern positioning and navigation systems.

Figure 1: Applications of integrated photonics from visible to near-infrared bands. 

In recent years, with the rapid development of visible-light integrated photonics technology, chip-scale optical atomic clocks featuring miniaturization, light weight, and low power consumption have become a research hotspot, promising to enable high-precision frequency metrology technology in broader application scenarios. However, efficient characterization of such chip-scale devices remains a formidable challenge, with the greatest bottleneck being the lack of measurement techniques and instruments that simultaneously offer wide spectral bandwidth and high spectral resolution.

Addressing this critical challenge, the research team innovatively designed and developed a novel vector spectrum analyzer featuring wide spectral coverage of 518-541 nm and 766-795 nm, with frequency resolution reaching 161 kHz. The system is based on external-cavity diode lasers (ECDLs), combined with broadband chirped periodically poled lithium niobate (CPLN) waveguides for second-harmonic generation (SHG), achieving high-power, narrow-linewidth, mode-hop-free continuous-wave tunable laser output in the visible spectrum. Simultaneously, the system introduces hyperfine structures of alkali metal atoms and iodine molecules as frequency references, enabling high-precision frequency calibration at the MHz level.

This instrument not only fills the technical gap in broadband vector spectral measurement for visible-light integrated devices but also pioneers several key applications. For example, leveraging this system, the research team completed, for the first time, cross-octave dispersion characterization of microresonators from near-infrared to visible light, precisely determining the positions of dispersive waves—of significant importance for phase-matching design in applications such as on-chip octave-spanning optical frequency combs, supercontinuum generation, and nonlinear frequency conversion. Furthermore, the instrument can resolve low-repetition-rate optical frequency comb structures that traditional spectrum analyzers struggle to distinguish, with a frequency resolution of 3 MHz, meeting the measurement requirements of advanced systems such as high-precision optical communications, microwave frequency synthesis, and laser frequency stabilization.

 Figure 2: Cross-octave microresonator dispersion measurement. 

This research achievement not only demonstrates the most advanced vector spectral measurement capability in the visible-light band but also provides crucial support for the realization of chip-scale optical atomic clocks. Against the backdrop of growing global demand for high-precision, low-power, and easily deployable time and frequency standards—particularly in strategic fields such as space navigation, geodetic surveying, and quantum precision measurement—optical atomic clock solutions based on photonic chips are receiving widespread attention. This achievement provides the "measurement eye" required for constructing such systems, promising to significantly enhance the design efficiency, testing reliability, and engineering maturity of integrated optical devices.

Publication Information 

Baoqi Shi, a Ph.D. student jointly trained by Shenzhen International Quantum Academy and University of Science and Technology of China, and Ming-Yang Zheng, Associate Researcher at Jinan Institute of Quantum Technology, are co-first authors of the paper. Researcher Liu Junqiu is the corresponding author. Key collaborators also include Professor Zhang Qiang from Jinan Institute of Quantum Technology, Associate Professor Wang Anting from University of Science and Technology of China, and Researcher Liang Wei at Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences. This work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, Guangdong Province, and Shenzhen Municipality.

A hyperfine-transition-referenced vector spectrum analyzer for visible-light integrated photonics,  Nature Communications  16, 7025 (2025). Original link: https://www.nature.com/articles/s41467-025-61970-0