Photonics Research, Volume. 11, Issue 6, 917(2023)
Hundredfold increase of stimulated Brillouin-scattering bandwidth in whispering-gallery mode resonators Editors' Pick
Fig. 1. (a) Illustration of the regular backward SBS in a straight path, where the phase velocity of the acoustic wave
Fig. 2. (a) Schematic of the experimental setp. CW laser, single-frequency tunable pump laser; EDFA, erbium-doped fiber amplifier; VOA, variable optical attenuator; FPC, fiber polarization controller; FOC, fiber optical circulator; PD, photodetector; FRI, fiber ring interferometer; FG, function generator; ESA, electrical spectrum analyzer; OSA, optical spectrum analyzer; OSC, digital oscilloscope; PC, computer; DAQ card, data acquisition card; WGMR, WGM resonator. Inset, a photograph of the fiber coupled WGMR setup. (b) Spectra of two WGMs (i), (ii) showing reflected signals due to Rayleigh scattering. (c) Spectra of WGMs showing the increased reflected signal due to SBS in the mode (ii). (d) Step-by-step data acquisition of the transmitted and reflected signals as the pump frequency is scanned across modes (i) and (ii) from the blue side, covering a spectral range of about 0.52 GHz. The total number of scan steps is 1500. (e) Corresponding optical spectra recorded in each of the 20 steps. (f) Optical spectra for the Step B 35 (left) and the Step B 65 (right) showing the FWM and SBS signals in mode (i) and mode (ii), respectively.
Fig. 3. (a) Transmission and reflection spectra of WGMs when the pump frequency is scanned from the blue side across a spectral range of 2.82 GHz. Inset, the corresponding spectra when the scan range is reduced to cover mode 1. (b) RF beatnote spectra from ESA when the pump frequency is continuously scanned across one single mode and the Stokes signal of SBS is monitored on OSA. The RBW of ESA is set to 5 MHz for fast capturing the RF beatnotes. (c) The backward optical spectrum when the pump scanning is stopped and the frequency of the pump is self-thermally locked to mode 1. Inset, the corresponding transmission and the reflected signal spectra. (d) Corresponding RF beatnote spectrum of the reflected signal showing a 3 dB linewidth of 10 kHz. Note that the beat of adjacent longitudinal modes corresponding to one FSR of about 37 GHz is out of range for both the fast PD and the handheld ESA.
Fig. 4. (a) Experimentally observed SBS frequency shift values for
Fig. 5. Brillouin–Kerr frequency comb generation in
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Guoping Lin, Jingyi Tian, Tang Sun, Qinghai Song, Yanne K. Chembo. Hundredfold increase of stimulated Brillouin-scattering bandwidth in whispering-gallery mode resonators[J]. Photonics Research, 2023, 11(6): 917
Category: Lasers and Laser Optics
Received: Jan. 3, 2023
Accepted: Mar. 28, 2023
Published Online: Jun. 8, 2023
The Author Email: Guoping Lin (guoping.lin@hit.edu.cn)