Simultaneous amplification of sodium and fluorine Balmer-α lines

We report simultaneous amplification of H-like Na and F Balmer-α lines (wavelengths of 5.42 and 8.10 nm, respectively) with a gain–length product of ~4. A 30-J, 20-ps, 0.53-μm laser pulse was line focused onto a 6.3-mm-long, 50-μm-wide, and 400-nm-thick (NaF) stripe target at an irradiance of 5 × 1014 W/cm2. The time- and space-integrated gain coefficients measured with cross-calibrated on- and off-axis spectrometers are 5.9 cm−1 for both Na and F Balmer-α lines. The space-resolved on-axis spectrometers show that the spatial peak intensity of the F line is located 50–200 μm from the original target surface, while that of Na is 0–100 μm away, which agrees qualitatively with the hydrodynamic calculations. The fine-structure intensity ratio of an amplified F line was also measured with a high-resolution spectrometer with a resolving power of greater than 2100.