A joint research team including National University of Defense Technology, National University of Singapore and Hunan Normal University innovatively improved the sensitivity of displacement sensing by introducing losses in a macroscopic F-P optical resonator. This innovative approach, which leverages non-Hermitian exceptional points, addresses the longstanding challenge of achieving high sensitivity and high signal-to-noise ratio in traditional lossless optical nano-displacement sensors. This breakthrough paves the way for new advancements in optical ultra-precision measurement and sensing. The research paper, titled "Single-cavity loss-enabled nanometrology", was published online on July 17, 2024, in Nature Nanotechnology (DOI: 10.1038/s41565-024-01729-8).
Conceptual Diagram of Loss-Enhanced Cavity Nano-Measurement
High-precision nano-displacement detection technology is crucial for applications such as semiconductor manufacturing and weak force sensing. Traditional optical nano-measurement techniques typically rely on nano-fabrication, external reference beams, or complex post-processing methods, all of which are based on lossless optical systems. Generally, loss is considered the enemy of optical precision measurement, which could diminish the resolution and signal-to-noise ratio of optical systems. This research takes an unconventional approach by intentionally introducing loss and utilizing non-Hermitian exceptional point effects. This method not only achieves a two-order-of-magnitude enhancement in optical response to displacement but also ensures an increase in the signal-to-noise ratio of more than five times. Furthermore, this device, in contrast to traditional system, does not require an external reference beam and employs a compact design with a single light source and single cavity, significantly simplifying optical design and fabrication. This research provides new avenues and platforms for the advancement of high-precision nano-displacement measurement technology.
(a) Schematic of the Experimental System (b) Displacement Response of a Conventional Hermitian Cavity (c) Displacement Response of a Non-Hermitian Enhanced System
The College of Advanced Interdisciplinary Studies of National University of Defense Technology, is the first and corresponding author institution for the article. Ph.D. students Xu Jipeng and Mao Yuanhao from NUDT are co-first authors and Professor Zhu Zhihong and Professor Liu Ken serve as co-corresponding authors.
Written by: Xu Jipeng, Mao Yuanhao
Photo by: Xu Jipeng