Fig. 1. The experimental setup for direct generation of femtosecond vortex arrays. PCS, pump coupling system; IM, input mirror; HR, high-reflection mirror; OC, output coupler; SESAM, semiconductor saturable absorber mirror; CCD, charge-coupled device camera.

Fig. 2. Evolution of the vortex laser with pump power. (a) Output power of TEM₀₀; (b) output powers of LG_0,1 and TVA. QML, Q-switch mode locking; CWML, CW mode locking.

Fig. 3. (a1), (b1), (c1) Experimental intensity distributions; (a2), (b2), (c2) experimental interference patterns; (a3), (b3), (c3) simulated intensity distributions; (a4), (b4), (c4) simulated interference patterns; (a5), (b5), (c5) simulated phase distributions of TEM₀₀, LG_0,1, and TVA, respectively.

Fig. 4. Characteristics of the mode-locked pulses of TEM₀₀, LG_0,1, and TVA, respectively. (a1)–(c1) Pulse sequences on 100 ns and 2 ms time scales, respectively. (a2)–(c2) The autocorrelation traces depicted with black points represent the experimental data, while the red lines correspond to the sech² fitting curves. a.u. represents arbitrary unit.

Fig. 5. (a) Wavelengths of the mode-locked TEM₀₀, LG_0,1, and TVA lasers; (b) radio-frequency spectrum of the mode-locked TVA laser. RBW, resolution bandwidth.