Fig. 1. Acoustic modes in an optical fiber core: (a) radial mode, R0m; (b) torsional-radial mode, TR2m.

Fig. 2. Operation of the laser at the fundamental frequency. (a) Er-doped fiber laser. EDF, Er-doped fiber; LD, 1480 nm laser diode for the pump; POC1 and POC2, polarization controllers; OISO, optical isolator; WDM, wavelength division multiplexer; OUTPUT C, 80:20 output coupler. (b) Average laser output power versus pump power; inset: the RF linewidth versus pump power (370 Hz at 220 mW pump power). The rectangle indicates the interval where unstable mode-locking patterns have been observed. (c) The optical spectrum; inset: the same spectrum plotted using a linear scale: 0.2 nm is a bandwidth at the 3 dB level. (d) The train of pulses at the fundamental frequency; inset: time-resolved pulse.

Fig. 3. (a) Acousto-optical polarization-dependent locking of a high harmonics RF comb showing the 24th harmonic along with satellites of 23rd-,24th-, and 25th-harmonics tuning with the help of in-cavity POC2. (b) Emergence of the 293.16 MHz pulse train for positions 15, 16, 17, and 18 of POC2. (c) Evolution of the RF spectrum of the 293.16 MHz line for positions 15, 16, 17, and 18 of POC2. (d) The output SOPs for POC2 positions 15 and 18 (measurement resolution is 1 μs).

Fig. 4. Results of the numerical modeling. (a), (d), (g) The output power versus time for two linearly cross-polarized SOPs, Ix (blue line) and Iy (black), and total power, I=Ix+Iy (red); (b), (e), (h) spectrum of the oscillations; (c), (f), (i) trajectories on the Poincare sphere. Parameters: time is normalized to the roundtrip time and frequency Ω to the fundamental frequency; birefringence strengths, βL and βC, to the fiber length; (a)–(i) Ω=7,A0=0.1; ellipticity of the pump wave δ=0.5; (a)–(c) βL=2π/5, βC=0; (d)–(f) βL=2π/5, βC=2π2/5; (g)–(i) βL=2π/5, βC=2π4/5. The other parameters are found in Appendix C.

Fig. 5. Results of the numerical modeling. The difference as compared to Figs. 4(g)–4(i) is in the increased ellipticity of the pump wave δ=0.7.