Resonance-enhanced spectral funneling in Fabry–Perot resonators with a temporal boundary mirror

Abstract

A temporal boundary refers to a specific time at which the properties of an optical medium are abruptly changed. When light interacts with the temporal boundary, its spectral content can be redistributed due to the breaking of continuous time-translational symmetry of the medium where light resides. In this work, we use this principle to demonstrate, at terahertz (THz) frequencies, the resonance-enhanced spectral funneling of light coupled to a Fabry–Perot resonator with a temporal boundary mirror. To produce a temporal boundary effect, we abruptly increase the reflectance of a mirror constituting the Fabry–Perot resonator and, correspondingly, its quality factor in a step-like manner. The abrupt increase in the mirror reflectance leads to a trimming of the coupled THz pulse that causes the pulse to broaden in the spectral domain. Through this dynamic resonant process, the spectral contents of the input THz pulse are redistributed into the modal frequencies of the high-Q Fabry–Perot resonator formed after the temporal boundary. An energy conversion efficiency of up to 33% was recorded for funneling into the fundamental mode with a Fabry–Perot resonator exhibiting a sudden Q-factor change from 4.8 to 48. We anticipate that the proposed resonance-enhanced spectral funneling technique could be further utilized in the development of efficient mechanically tunable narrowband terahertz sources for diverse applications.

Linear and phase controllable terahertz frequency conversion via ultrafast breaking the bond of a meta-molecule

“…The electric tuning offers a more accessible method to control the output of the converted waves, which has significance for the application of the time-varying metasurface. In recent work, the highly efficient linear frequency conversion at the temporal boundary was experimentally demonstrated, which was attributed to the high Q factor of the resonant cavity 42 . We also found that the loss of metasurface is a crucial factor affecting the conversion efficiency (see Supplementary Notes 10 – 12 for details).…”

“…It was theoretically proposed that phase control can be used for wavefront engineering of the converted waves. In recent work, efficient frequency conversion, as well as phase coherence of the converted waves, has been observed experimentally by ultrafast modulation of structural dispersion in the waveguide 41 or loss in the Fabry–Perot cavity 42 . Despite the progress, a chip-compatible planar frequency converter with a high conversion efficiency and phase control is highly desired to advance the practical applications.…”

Linear Terahertz Frequency Conversion in a Temporal‐Boundary Metasurface

“…Using the exquisite design of metasurfaces, Q ‐boosting metasurfaces were proposed to break time‐bandwidth limitations and enhance the nonlinear optical responses. [ 36 ] The potential applications in photon storage [ 22 ] and spectrum compression [ 42 ] could be realized by an instantaneous change of the resonator properties. Furthermore, although our results concentrate on terahertz regime, the conclusion is universal and applicable to infrared and shorter wavelength regime.…”

Progress and realization platforms of dynamic topological photonics

“…In fact, the researches on DP are quite broad, including the dynamic evolution process of optical system [35,36] and physical system in time domain, such as synthetic dimension [37][38][39] and gauge field. [40] As for the photonic devices, DP is also widely studied in waveguide systems, [41][42][43] resonant cavity systems, [44][45][46] photonic crystal systems, [47][48][49] exciton systems. [50][51][52] Fig.…”