Tunable narrowband fiber laser with feedback based on whispering gallery mode resonances of a cylindrical microresonator

Abstract

Narrowband filtering based on whispering gallery modes of a slightly tapered cylindrical optical microresonator was used to implement a tunable narrowband erbium-doped fiber laser. The laser can be set to emit a single longitudinal cavity mode (single frequency), although the laser cavity is a few meters long. In the single-frequency regime the laser can emit a maximum power of 0.380 mW with a linewidth <35 kHz and a signal-to-noise ratio exceeding 50 dB. Tunability is achieved by sliding the excitation point along the microcylinder. A tuning range of 1.16 nm is demonstrated.

Controling the coupling properties of active ultrahigh-Q WGM microcavities from undercoupling to selective amplification

“…In particular, it has been demonstrated that they can find applications in very sensitive sensing23, microwave signal generation45 or optical processing67891011, narrow-band and high-contrast optical filtering1213 or high-coherence optical sources1415161718. Although huge technological progresses have been done in chip-compatible integrated optics19, crystalline millimeter size WGM resonators obtained by thorough cleaning and polishing steps provide the highest resonance quality2021 with Q-factors up to 10 11 .…”

Analysis of whispering gallery modes resonators: wave propagation and energy balance models

“…Microresonators based on WGM exhibit high Q factors, probably the highest ever reported, which makes them particularly attractive for different applications as narrowband spectral filtering [1], single-frequency lasers [2], generation of frequency combs [3], and sensing [4]. In particular, azimuthal WGM resonances of optical fibers have been demonstrated to be useful for the characterization of optical fibers: thermal effects in active fibers [5], fiber diameter fluctuations [6,7], UV-induced losses [8], and Pockels' coefficients [9].…”

Tunable Narrow-Linewidth Ring Laser Based on the Polarization Conversion in a Tapered Fiber-Coupled Whispering Gallery Mode Resonator

“…Considering the development of the whispering gallery mode (WGM) resonators in recent years [9][10][11][12], they have been widely used in the configuration of narrow-linewidth lasers due to their high Q-factor, which can be up to 10 5 times larger than that of the FP cavity. The lasers developed include stimulated lasers [10,13], WGM resonator lasers [14,15], and various ring lasers [6,16]. Due to the advantages of relative lower cost and good tunability, ring lasers attract more attention among researchers.…”

“…The ADF filter based on the WGM includes at least two channels: one is through the channel, which usually provides the band-reject feature, and the other is the drop channel, which provides the band-pass feature. The channels could be either two individual waveguides [15,16,18,19] or two modes in one waveguide [20][21][22][23]. Note that a waveguide has to be calibrated with the WGM within hundreds of nanometers to achieve high coupling efficiency.…”