Optical frequency combs (OFC’s) is well-known as a frequency “ruler”, which can measure time and frequency with highest accuracies. The combination of highly stable and efficient OFC’s and the extremely compact nanophotonic devices would shrink the millions-dollars table-top system into a cost-effective cm3-size cube, and open an amazingly wide range of new sciences and technologies. In addition, the quantum version of optical frequency combs is an emerging technique for multidimensional entangled photon generations, linear quantum photonic processor, quantum spectroscopy and sensing beyond classical limits. Our group will focus on solving the outstanding challenges in this field: 1) integration of high-energy modelocked pulse lasers 2) fully stabilized frequency comb sources 3) efficient nonlinear conversion to ultraviolet and mid-IR wavelengths.
Previous work in the mid-IR (also see refs in integrated optoelectronic platform):
Mid-infrared frequency combs have broad applications in molecular spectroscopy and chemical and biological sensing. We combine the extreme compactness of integrated nonlinear devices with cost-effective silicon photonics, for broadband mid-IR sensing applications.
We demonstrated the first and the broadest coherent mid-infrared frequency comb in a silicon microresonator. The comb state can be electrically tuned via control of free carrier lifetime [1]. Based on this platform, we demonstrated two different types of mid-IR microcomb-based spectroscopy, dual-comb spectroscopy [2], and scanning comb spectroscopy [3] which are suitable for condensed phase study and trace gas sensing, respectively. we combined dual-comb technique with microfluidic technology for ultrafast detection of liquid flow dynamics [4]. Furthermore, we have explored the potential of gas-sensing using two coupled cavities, relaxing the demand of on-chip pump lasers [5]. Finally, we show that silicon photonics can achieve low-loss propagation further up to 6 μm [6]. This work represents a novel direction for interdisciplinary research, and is a significant advancement to the fields of optical frequency combs, nanotechnology and spectroscopic instrumentation. With continued progress of quantum cascade laser and mid-IR instrumentation such as detectors and digitizers, we envision a spectroscopy lab-on-a-chip that could realize real-time fingerprinting with label-free and high-throughput detection of trace molecules.
Ref: M. Yu, et al., “Gas-phase microresonator-based comb spectroscopy without an external pump laser,” ACS Photonics 5, 2780 (2018).
Related publication:
[1] M. Yu, et al., “Soliton modelocked mid-infrared frequency comb in silicon microresonators,” Optica 3, 854 (2016).
[2] M. Yu, et al., “Silicon-chip-based mid-infrared dual-comb spectroscopy,” Nature Commun. 9, 1869 (2018).
[3] M. Yu, et al., “Microresonator-based high-resolution gas spectroscopy,” Opt. Lett. 42, 4442 (2017). – Editor’s Pick
[4] M. Yu, et al., “Microfluidic mid-infrared spectroscopy via microresonator-based dual-comb source,” Opt. Lett. 44, 4259-4262 (2019).
[5] M. Yu, et al., “Gas-phase microresonator-based comb spectroscopy without an external pump laser,” ACS Photonics 5, 2780 (2018).
[6] S. Miller, M. Yu, et al., “Low-loss silicon platform for broadband mid-infrared photonics,” Optica 4, 707 (2017).