Record-high-Q AMTIR-1 microresonators for mid- to long-wave infrared nonlinear photonics

Abstract

AMTIR-1 chalcogenide glass has shown its potential for use in thermal imaging systems owing to its low refractive index, thermal resistance and high transparency across the infrared wavelength regime. Here we report a millimeter-scale high-Q whispering gallery mode microresonator made of AMTIR-1. The recorded Q-factor has reached $1.2\times10^7$ at 1550 nm, which is almost two-orders of magnitude higher than previously reported values. We characterize the thermal properties, where low thermal conductivity plays an important role in thermal resonance tuning. We further show that AMTIR-1 resonators support anomalous dispersion as well as a low absorption coefficient near the 7~\textmu m wavelength band, thus offering the possibility of providing suitable platforms for mid-infrared, long-wave infrared nonlinear optics including microresonator frequency comb generation.

Figures (5)

• Figure 1: (a) Schematic diagram of the experimental setup. (b) Photograph of an AMTIR-1 microresonator. (c) Sideview of the prism coupling system, where the resonator temperature is controlled with a thermoelectric cooler.
• Figure 2: (a) Observed transmission spectrum and (b) the Lorentzian fitting, yielding a loaded Q-factor of up to $1.2\times10^7$. The measured mode belongs to the TE modes.
• Figure 3: Reported Q-factors as a function of wavelength of microcavities made of AMTIR-1. WGM microcavity, ref. Singh2015, Photonic crystal (PhC) nanocavity, refs. Choi2007Lee2009Conteduca2015. The solid blue line denotes the absorption coefficient of AMTIR-1 (right axis), and the solid green line corresponds to the Q-factor calculated with the material absorption (left axis).
• Figure 4: (a, b) Simulated steady-state temperature distributions when the temperature of the aluminum base is increased from 291 K to 296 K for an AMTIR-1 resonator and an $\mathrm{MgF_2}$ resonator, respectively. (c) Resonance frequency shifts as a function of temperature change. Experimental results (filled circles) align with simulated results (solid lines) rather than theoretical predictions (dashed lines), especially in an AMTIR-1 resonator due to its low thermal conductivity.
• Figure 5: (a) Simulated dispersion $\beta_2$ of AMTIR-1 resonators for different FSRs and material dispersion. The curvature radius is 50 µ m. (b) Simulated optical spectrum and integrated dispersion $D_\mathrm{int}$ with a center wavelength of 7 µ m. Other parameters are as follows: $Q_\mathrm{int}=1\times10^7$, $Q_\mathrm{ext}=3\times10^7$ , $D_1/2\pi=20$ GHz, $D_2/2\pi=12.3$ kHz, $D_3/2\pi=-185$ Hz, $g=1.7\times10^{-3}$, and $P_\mathrm{in}=|A_\mathrm{in}|^2=500$ mW. (c) Evolution of intracavity power with and without the TO effect. The detuning is normalized by a half of the decay rate (i.e., $2\delta_0/\kappa_\mathrm{tot}$). The inset shows temporal waveforms of the MI (red) and DKS (blue) states.