Chuan Guo

High-power QCW microsecond-pulse solid-state sodium beacon laser with spiking suppression and D2b re-pumping.

A 65 W quasi-continuous-wave microsecond-pulse solid-state sodium beacon laser tuned to the sodium D2a line has been developed with a linewidth of 0.3 GHz, beam quality of M2=1.38, and pulse width of 120 μs at a repetition rate of 500 Hz by sum-frequency mixing 1319 and 1064 nm diode-pumped Nd:YAG master-oscillator power-amplifier systems. The laser wavelength stability is less than ±0.15 GHz through feedback controlling. The laser spiking due to relaxation oscillations is suppressed by inserting frequency doublers in both 1319 and 1064 nm oscillators. Sodium D2b re-pumping is accomplished by tuning the frequency of the electro-optic modulator with the right D2a-D2b offset. A bright sodium laser guide star with a photon return of 1820 photons/cm2/s was achieved with the laser system when a 32 W circular polarized beam was projected to the sky during our field test at the Xinglong Observatory.

Wavelength Switchable High-Power Diode-Side-Pumped Rod Tm: YAG Laser around 2µm

We report a high-power diode-side-pumped rod Tm:YAG laser operated at either 2.07 or 2.02 µm depending on the transmission of pumped output coupler. The laser yields 115W of continuous-wave output power at 2.07 µm with 5% output coupling, which is the highest output power for all solid-state 2.07 μm cw rod Tm:YAG laser reported so far. With an output coupler of 10% transmission, the center wavelength of the laser is switched to 2.02 μm with an output power of 77.1 W. This is the first observation of high-power wavelength switchable diode-side-pumped rod Tm:YAG laser around 2 µm.

Spiking suppression of high power QCW pulse 1319 nm Nd:YAG laser with different intracavity doublers

We describe the results of our efforts in suppressing spiking of a high power, high beam quality 1319 nm Nd:YAG microsecond-pulse laser with three different intracavity frequency doublers. The 1319 nm laser is generated by a quasi-continuous-wave diode-pumped Nd:YAG ring laser system. One potassium titanyl phosphate (KTP), two KTPs and one lithium triborate (LBO) as frequency doublers are installed in the ring resonator and tested, respectively. At 800 Hz repetition rate, with a pulse width of 100 µs, performances of spiking suppression for each case are observed. The average output power are 23.6 W, 22.7 W and 23.4 W with beam quality factors of M 2 = 2.21, 1.28 and 1.25 for one KTP, two KTPs and one LBO, respectively. The corresponding brightness are 270 MW/(cm2sr), 780 MW/(cm2sr) and 860 MW/(cm2sr). With better beam quality, higher brightness, and easier maintainability, the LBO is the best option of the three. A laser rate equation model including the insertion loss of the doubler is applied for theoretical analysis of the output temporal pulse shape and power, and the simulated results agree well with the experimental data.

A High-Pulse-Energy High-Beam-Quality Tunable Ti:Sapphire Laser Using a Prism-Dispersion Cavity*

A high-pulse-energy high-beam-quality tunable Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. Using a fused-silica prism as the dispersion element, a tuning range of 740–855 nm is obtained. At an incident pump energy of 774 mJ, the maximum output energy of 104 mJ at 790 nm with a pulse width of 100 μs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, it is the highest pulse energy at 790 nm with pulse width of hundred micro-seconds for an all-solid-state laser. The linewidth of output is 0.5 nm, and the beam quality factor M 2 is 1.16. The high-pulse-energy high-beam-quality tunable Ti:sapphire laser in the range of 740–855 nm can be used to establish a more accurate and consistent absolute scale of second-order optical-nonlinear coefficients for KBe2BO3F2 measured in a wider wavelength range and to assess Millers rule quantitatively.

Frequency Stabilization of a Microsecond Pulse Sodium Guide Star Laser with a Tilt- and Temperature-Tuned Etalon

A frequency stabilization approach is introduced for the microsecond pulse sodium beacon laser using an intra-cavity tilt- and temperature-tuned etalon based on a computer-controlled feedback system connected with a fast high-precision wavelength meter. The frequency stability of the sodium beacon lasers is compared with and without feedback loop controlling. The output wavelength of the laser is locked to the sodium D-2 alpha absorption line (589.159 nm) over 12 h with the feedback loop controlling technology. As a result, the sodium laser guide star is successfully observed by the telescope of National Astronomical Observatories at Xinglong. This approach can also be used for other pulses and continuous-wave lasers for the frequency stabilization.

High-Power High Beam Quality Narrow-Linewidth Quasicontinuous Wave Microsecond Pulse 1064-nm Nd:YAG Amplifier

We demonstrated a high average power, high beam quality, narrow linewidth, quasicontinuous wave (QCW) diode-pumped 1064-nm Nd:YAG amplifier. A narrow-linewidth QCW pulse Nd:YAG oscillator was employed as the seed laser, providing a maximum average power of 53.4 W at a pulse repetition frequency of 500 Hz and pulse width of 108 μS with a beam quality factor M2 = 1.21. After that, a two-stage double-pass Nd:YAG amplifier was performed. The amplifier delivers a maximum output power of 238 W with a linewidth of 0.4 pm and a tunable range of 119.3 pm. The beam quality was measured to be M2 = 1.65. To the best of our knowledge, this represents the highest average power and the highest brightness for a narrow-linewidth QCW microsecond pulse 1064-nm laser.