Fig. 1. Theoretic relationship between the radius and the threshold of pump energy with a single crystal (dashed line), splicing crystals (dot line), and splicing crystals (solid line). The absorption coefficient is 0.94.

Fig. 2. Scheme of splicing crystals.

Fig. 3. Schematic of and .

Fig. 4. (a) Situation of spectral modulation (single-pass) at , ; the thickness of the crystal is 10 mm. (b) Sidelobes generated by spectral modulation.

Fig. 5. Schematic of the influence of thickness difference on the temporal profile.

Fig. 6. Theoretical relationship between the spot in the near field and the spot in the far field.

Fig. 7. Scheme of experiment: (a) measurement of the energy, spot in the near and the far fields, and spectra; (b) measurement of the autocorrelator trace; (c) photo of the splicing crystals.

Fig. 8. Spectrum of the seed: the dashed curve is the original spectrum; the dotted curve is the spectrum amplified by a single pass; the solid curve is the spectrum amplified by a single pass.

Fig. 9. Spectrum of the beam passed through the smaller crystals of the splicing crystals.

Fig. 10. Autocorrelation trace in the experiment: (a) original trace; (b) the trace of the splicing crystals.

Fig. 11. Spot of the extraction beam in the near field: (a) with soft-edge aperture; (b) without edge aperture, and (c) schematic of the soft-edge aperture.

Fig. 12. Spot of the extraction beam in the far field: (a) did not pass through the crystal, (b) passed through the crystal without the soft-edge aperture, and (c) passed through the crystal with the soft-edge aperture.