Daijun Li

High efficiency 165 W near-diffraction-limited Nd:YVO 4 slab oscillator pumped at 880 nm

We demonstrate a compact, efficient Nd:YVO(4) stable-unstable hybrid slab oscillator that was partially end pumped at 880 nm. A maximum output power of 165 W at 1064 nm was obtained with an optical-to-optical efficiency from absorbed pump power to laser output of up to 60% and a slope efficiency of up to 66%. The beam propagation factors M(2) were 1.7 in the stable direction and 1.4 in the unstable direction without sidelobes.

Diode-end-pumped double Nd:YLF slab laser with high energy, short pulse width, and diffraction-limited quality

We have developed a novel electro-optic Q-switched diode-end-pumped solid slab laser that combines high energy, short pulse width, high repetition rates, and diffraction-limited beam quality. With two partially end-pumped Nd:YLF slabs and a 100 mm long off-axis positive branch stable-unstable oscillator, 24.2 mJ, 7.1 ns electro-optic Q-switched pulse at 1 kHz repetition rate with a beam quality of M(x)(2)=1.4 and M(y)(2)=1.3 was generated. The peak power reached 3.5 MW. Efficient external second-harmonic generation was achieved by use of lithium triborate with low peak-power intensity.

Diode-pumped efficient slab laser with two Nd:YLF crystals and second-harmonic generation by slab LBO.

We demonstrate a diode-pumped electro-optical Q-switched slab laser with a high optical efficiency, high pulse energy, and short pulse width with two Nd:YLF crystals inside one resonator. The single compact slab resonator can generate a 1D top-hat beam at both the far field and the near field. With a slab-geometry-design lithium triborate (LBO) crystal, efficient critical phase-matching second-harmonic generation for a 1D top-hat beam with multiple transverse modes is achieved.

Diode-end-pumped electro-optically Q-switched Nd:YLF slab laser

We report a very compact Nd:YLF slab laser that is end pumped by a quasi-continuous-wave diode stack. A hybrid resonator is used to generate high output power in a near-diffraction-limited beam (i.e., a beam propogation M2 factor of less than 1.2). A pulse energy of 14.3 mJ was obtained with a pulse width of 8.5 ns at a repetition rate of 500 Hz, which corresponds to a Q-switched peak power of 1.68 MW.

39.1 μJ picosecond ultraviolet pulses at 355 nm with 1 MHz repeat rate

Based on our reliable high-power picosecond laser source with high beam qualities, we designed a compact and efficient third harmonic generation scheme by cascading a frequency doubling and a sum frequency generation using LBO as the nonlinear material. A maximum output of 39.1 W with a repeat rate of 1 MHz at 355 nm was obtained, which implied a pulse energy of 39.1 μJ, which was the highest picosecond UV pulse energy with an all-solid-state setup so far. The total conversion efficiency from infrared to UV was up to 46%. And the output UV has excellent beam qualities with an M-square factor less than 1.1.

Compact multipass Nd:YVO4 slab laser amplifier based on a hybrid resonator

The design of a diode stack end-pumped multipass Nd:YVO4 slab laser amplifier based on a stable and off-axis positive-branch confocal unstable hybrid resonator was demonstrated. Without the use of active switching elements, the hybrid resonator of the amplifier permits high multipass amplification of Q-switched laser beams in a compact package. The pulse energy of 3.8mJ and pulse width of 5ns was obtained at a repetition of 1kHz with the amplification factor of 11. In cw operation, the maximum output power of 35.2W was obtained by amplifying the seeder power of 4W. The beam propagation factor M2 in both the cw and pulse models was under 1.3.

Diode end-pumped high-power Q -switched double Nd:YAG slab laser and its efficient near-field second-harmonic generation

We reported on an all-solid-state double Nd:YAG slab laser. The laser was based on two diode end-pumped Nd:YAG slabs and a stable-unstable hybrid resonator. A cw output of 189 W and an average Q-switched output of 169 W at 10 kHz with an M(2) factor of 1.5 in the slow direction and 1.7 in the fast direction were obtained. We demonstrated efficient near-field frequency doubling by imaging the one-dimensional top-hat near-field to a lithium triborate frequency doubler. We obtained 93 W green light at 10 kHz with a pulse width of 10.7 ns. The efficiency of second-harmonic generation was up to 57%.

Near-diffraction-limited green source by frequency doubling of a diode-stack pumped Q-switched Nd:YAG slab oscillator-amplifier system

A near-diffraction-limited, stable, 18 mJ green source with a pulse width of 16.7 ns was generated at a 1 kHz repetition rate by frequency doubling of diode stacks end-pumped electro-optically Q-switched slab Nd:YAG oscillator-amplifier system. The pump to green optical conversion efficiency was 10.7%. At the output energy of 15 mJ at 532 nm, the M2 factors were 1.3 and 1.7 in the unstable and stable directions, respectively. The energy pulse stability was approximately 0.8%.

Monolithic Nd:YVO4 slab oscillator-amplifier.

We report on a compact, efficient, and reliable monolithic Nd:YVO(4) slab oscillator-amplifier with an output power of 29.3 W in cw operation and an optical-to-optical efficiency of 24%. In electro-optically Q-switched operation, 28.8 W of average power at a repetition rate of 100 kHz with a pulse width of 15 ns was measured. The RMS stability of the pulse energy is better than 1.7%. The beam quality M(2) in both cw and pulse models was under 1.3.

Theoretical and experimental research on the polarization-coupled-input Raman oscillator

We present a polarization-coupled-input Raman oscillator, which is pumped by a 532 nm Q-switched hybrid resonator Nd:YVO(4) slab second harmonic generation laser. By the polarization-coupled method, the dichroic mirror is avoided and more than 98% of the 532 nm pump energy can be coupled into the Raman oscillator. Theoretical calculations and the experimental results show that the second Stokes effect is dramatically suppressed. With this method, the pure 559 nm (P(532)/P(559)<0.7% and P(589)/P(559)<0.1%) laser output can be achieved.