Fig. 1. Energy levels and transition process of Kr (1s and 2p).

Fig. 2. Schematics of the experimental setup of a diode-pumped Kr* laser. BS, beam splitter; DM, dichroic mirror; OC, output coupler; LPF, long pass filter; PD, photodetector.

Fig. 3. Time-dependent number density of Kr* at different pressures.

Fig. 4. Spectrum of the output laser (877 and 892 nm) and the pump stray light (811 nm).

Fig. 5. Time-dependent traces for the voltage between two electrodes, the number density of Kr (1s₅) under discharge only and the laser intensity under 7.6 W pump power.

Fig. 6. Laser power of the Kr* laser with increasing pressure, under 7.6 W pump power.

Fig. 7. (a) Population distribution in Kr (2p) (the error bar represents standard deviation) and (b) population of Kr (2p₈, 2p₉ and 2p₁₀) versus pressure.

Fig. 8. Time-dependent traces of the number density of the 1s₅ and 1s₄ levels. (The oscillation in the figure is the noise of the discharge.)