Broadband Mid-Infrared Frequency Comb in Integrated Chalcogenide Microresonator

Mid-infrared (MIR) frequency combs based on integrated photonic microresonators (micro combs) have attracted increasing attention in chip-scale spectroscopy due to their high spectral resolution and broadband wavelength coverage. However, up to date, there are no perfect solutions for the effective generation of MIR micro combs because of the lack of proper MIR materials as the core and cladding of the integrated microresonators, thereby hindering accurate and flexible dispersion engineering. Here, we have firstly demonstrated a MIR micro comb generation covering from 6.94 & mu;m to 12.04 & mu;m based on a sandwich-integrated all-ChG microresonator composed of GeAsTeSe and GeSbSe as the core and GeSbS as cladding. The novel sandwich microresonator is proposed to achieve a symmetrically uniform distribution of the mode field in the microresonator core, precise dispersion engineering, and low optical loss, which features a wide transmission window, high Kerr nonlinearity, and hybrid-fabrication flexibility on a silicon wafer. A MIR Kerr frequency comb with a 5.1 & mu;m bandwidth has been numerically demonstrated, assisted by dispersive waves. Additionally, a feasible fabrication scheme is proposed to realize the on-demand ChG microresonators. These demonstrations characterize the advantages of integrated ChG photonic devices in MIR nonlinear photonics and their potential applications in MIR spectroscopy.

Automated summary

In this study, a sandwich-integrated all-ChG microresonator was used to demonstrate a mid-infrared (MIR) microcomb generator covering a wavelength range from 6.94μm to 12.04μm. The novel microresonator features a symmetrically uniform distribution of the mode field, precise dispersion engineering, and low optical loss, offering a wide transmission window, high Kerr nonlinearity, and hybrid-fabrication flexibility on a silicon wafer. Numerical simulations successfully demonstrated a MIR Kerr frequency comb with a bandwidth of 5.1μm, assisted by dispersive waves. A feasible fabrication scheme for on-demand ChG microresonators was also proposed. These findings highlight the advantages of integrated ChG photonic devices in MIR nonlinear photonics and their potential applications in MIR spectroscopy.