Fig. 1. (a) Microscope image of TMF; (b) and (c) transverse modal intensity of HE^x₁₁ and HE^y₁₁ modes; (d)–(g) transverse modal intensity of TE01, HE21e, HE21o, and TM01 modes; (h) experimental configuration for measuring the transmission spectra of AIFG; (i)–(k) spectral tunability of AIFG with three separated resonance peaks, corresponding to the coupling between HE^x/y₁₁ and TE01, HE21e/o, TM01 modes, respectively.

Fig. 2. Experimental configuration for examining the generation and SRS of the nanosecond CVBs in the TMF.

Fig. 3. (a) Typical pulse train of the nanosecond pulse with repetition frequency of 10 Hz, and the inset is the temporal width of the nanosecond pulse with a rising edge of ∼10 ns; transmission spectra of AIFG (blue curves) with three separated resonance peaks corresponding to the mode conversion between HE11 and (b) HE21, (c) TM01, and (d) TE01 to coincide with the lasing spectrum (green curves) of the nanosecond pulse with central wavelength of 1064 nm.

Fig. 4. Modal intensity distributions of (a₁) HE^x₁₁, (b₁) HE^y₁₁, (a₂) TM01, and (b₂) TE01; mode intensity distributions of (a₃)–(a₆) TM01 and (b₃)–(b₆) TE01 by rotating P. (c) Lasing spectra of the nanosecond pulse with transverse modal intensity distributions of HE^x/y₁₁, TM01, and TE01.

Fig. 5. (a) SRS spectra pumped using the nanosecond pulse with HE^x₁₁, when the average pump power is set as P = 0.66, 0.76, 0.85, 0.95, and 1.05 mW, respectively. Inset is the relationship between the pump power and the intensity of the first-order Stokes shift component. (b) SRS spectra pumped via the nanosecond pulse with HE^x₁₁ (pink curve) and TM01/TE01 (green curve), respectively.

Fig. 6. Modal intensity distributions of (a₁) TM01 and (b₁) TE01 of the first-order Stokes shift component of the SRS spectrum, respectively; polarization distribution examinations of (a₂)–(a₅) TM01 and (b₂)–(b₅) TE01 modes by rotating the P.