Visible Ultrashort Pulse Pr³⁺:YLF Lasers

Pr³⁺:YLF is a new solid-state laser medium that emits on multiple lines in the visible region of the spectrum (figure 1). Stark spliting of the spectal lines (figure 2) produces many transitions We have demonstrated lasing on 14 new lines, in addition to the 6 previously known transitions. The laser may be operated on multiple lines simultaneously. Some of these lines can support short pulses, and we have Kerr-lens mode-locked Pr:YLF for the first time.

Figure 1: Laser lines of Pr:YLF, superimposed on its fluorescence spectrum (grey)

Figure 2: Pump and laser transitions of Pr:YLF

The cavity layout for Kerr-lens mode-locking is shown in figure 3. We pump the Pr:YLF crystal from both sides with an argon-ion laser, and use a shaker to start the KLM. Alternatively, a liquid or solid-state slow saturable absorber may be used to start the mode-locking process. Self-starting KLM has also been demonstrated.

Figure 3: Cavity scheme of Kerr-lens mode-locked Pr:YLF laser

One of the transitions (³P₀ - ³H₆ at 613 nm) has a linewidth of ~1 nm, which is broad enougth to support sub-picosecond pulses. We have mode-locked this transition to produce pulses as short as 400 fs (figure 4).

Figure 4: Autocorrelation and spectrum of the shortest pulses produced

Relevant publications

Y. P. Tong, J. M. Sutherland, P. M. W. French, J. R. Taylor, A. V. Shestakov and B. H. T. Chai: 'Self-starting kerr-lens mode-locked femtosecond Cr4+:YAG and picosecond Pr3+:YLF solid-state lasers', Optics Letters, 21, pp.644-646 (1996)

S. Ruan, J. M. Sutherland, P. M. W. French, J. R. Taylor and B. H. T. Chai: 'Kerr-lens mode-locked visible transitions of a Pr:YLF laser', Optics Letters, 20, pp.1041-1043 (1995)

J. M. Sutherland, P. M. W. French, J. R. Taylor and B. H. T. Chai: 'Visible continuous-wave laser transitions in Pr3+:YLF and femtosecond pulse generation', Optics Letters, 21, pp.797-799 (1996)