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In this paper, we investigated the impact of the linewidth of a QCW pulsed sodium laser on the brightness performance of a generating sodium laser guide star by using the numerical simulation tool PRS. We compared the field test results with the simulation results for two TIPC’s 30W class sodium guide star lasers and found the results are in good agreement which proves the tool can be used for prediction. Then, we used the tool to study the influence of D2b repumping and different linewidths from 10MHz to 1GHz on the coupling efficiency and the photon return flux. For the TIPC’s QCW pulsed solid-state laser, when the on-sky power density is 1 W/m2, the coupling efficiency is 79.6 (photons/s/W/(atoms/m2)) without D2b repumping, however, the value is up to 213.3 (photons/s/W/(atoms/m2)) with 15% D2b enabled and is increased by 168% than the value without D2b; when the power density reaches 10 W/m2, the coupling efficiencies without D2b and with 15% D2b are 66.6 and 233.6 (photons/s/W/(atoms/m2)), respectively. The results show that for the QCW pulsed laser, D2b repumping is necessary. With D2b enabled, if the spectral linewidth is too wide or too narrow, the photon return flux will be adversely affected. The return flux of 60MHz is 52.5% higher than that of 1GHz, while the return flux of 300MHz is 37.8% higher than that of 10 MHz when the laser power is 100W.

A sub-pm linewidth high beam quality microsecond (μs) Ti:sapphire laser was reported, which was end-pumped by a frequency-doubled 1064 nm Nd:YAG laser. By inserting three birefringent plates tuner and one etalon into the cavity of the Ti:sapphire laser, a ∼ 0.8 pm linewidth at 819.710 nm was achieved with a maximum output power of 3 W operating at a high repetition rate of 500 Hz with pulse width of ∼25 μs. The beam quality factor M2 was measured to be ∼1.14. The wavelength could be finely tuned from 819.699 to 819.718 nm with tuning resolution of 0.76 pm. To the best of our knowledge, this is the first demonstration on the μs pulse Ti:sapphire laser at 819.710 nm with narrow linewidth and high beam quality simultaneously. Such μs 819.710 nm laser could be used to efficiently generate a polychromatic laser guide star together with a 589 nm laser for the tip-tilt correction of ground-based telescopes.

We demonstrated a high brightness narrow-linewidth microsecond (μs) pulse green laser from second harmonic generation (SHG) of a master oscillator power amplifier (MOPA) laser system. The oscillator was a quasi-continuous wave pulsed diode-side-pumped 1064 nm Nd:YAG laser with an average output power of 45.2 W and a beam quality factor of M2 = 1.21, operating at a pulse repetition frequency of 500 Hz with a ∼160 μs of pulse duration. After a two-stage amplifier, the fundamental output power of MOPA system was increased up to 198 W. Using a type-I lithium triborate nonlinear crystal, the maximum SHG output power of 78.4 W at 532 nm was obtained with a linewidth of 0.54 pm and a beam quality factor M2 less than 1.61. The brightness of the green light was as high as 1.08 × 1010 W/cm2 sr. This is, to the best of our knowledge, the highest brightness solid state light source for the narrow-linewidth μs pulse green lasers at 532 nm.

We demonstrated a compact high-efficiency 100-W-level, narrow-linewidth, quasi-continuous-wave (QCW) diode-side-pumped Nd:YAG laser with a linearly polarized TEM00 mode. Spatial hole-burning elimination and narrow-linewidth laser output were realized by a twisted-mode cavity and an etalon, respectively. The resonator was based on a thermally near-unstable cavity design with dual-rod birefringence compensation convex–convex structure. A 100.4-W linear polarized 1064-nm laser was achieved with a 340-W pump power, corresponding to an optical-to-optical conversion efficiency of 29.5%. The wavelength of the laser was tunable from 1064.22634 to 1064.68071 nm while stably maintaining a beam quality of M2 = 1.22 and a linewidth of ~240 MHz. The laser was operated at a repetition rate of 500 Hz with 160- $\mu \text{s}$ pulse duration. To the best of our knowledge, this represents the highest average-power and the highest brightness for narrow-linewidth QCW microsecond pulse 1064-nm lasers.

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.

In this letter, a high pulse energy and high beam quality 819.7 nm Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. At incident pump energy of 774 mJ, the maximum output energy of 89 mJ at 819.7 nm with a pulse width of 100 μs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, this is the highest pulse energy at 819.7 nm with pulse width of hundred microseconds for a Ti:sapphire laser. The beam quality factor M 2 is measured to be 1.18. This specific wavelength with the high pulse energy and high beam quality at 819.7 nm is a promising light source to create a polychromatic laser guide star together with a home-made 589 nm laser via exciting the sodium atoms in the mesospheric atmosphere.

A void-free bonding technique was demonstrated for a large slab Nd: YAG crystal with a bonding surface dimension of ∼ 160 m m × 70 m m . By using the novel fluxless oxide layer removal technology, the indium-oxide barrier problem was resolved. With the help of electrochemical-polished indium solder and a plasma-cleaned heat sink, the solderability of the indium was enhanced; in particular, the contact angle of the solder was improved from 51° to 31°. With the largest-bonding-size slab, a single-slab laser created a maximum output power of 7.3 kW under an absorbed pump power of 12.8 kW, corresponding to an optical to optical efficiency of 57% and a slope conversion of 67.8%. By detecting the wavefront of the interferometer before and after bonding, the RMS of wavefront was 0.192 λ and 0.434 λ ( λ = 633 n m ), respectively. To the best of our knowledge, this is the largest void-free bonding size for a laser slab and the highest output power achieved from a single-slab crystal laser oscillator.

The polychromatic laser guide star (PLGS) is one of the solutions proposed to measure the differential atmospheric tip-tilt. A watts-level microsecond pulse all solid state laser source with two wavelengths at 589 and 819.7 nm are developed to perform a proof-of-concept on-sky test for what is believed to be the first time. By sum-frequency of 1319 and 1064 nm, a 44 W maximum average output power at 589.159 nm is generated with the pulse width of ~90 μs at 500 Hz, the linewidth of 0.46 pm, and the beam quality of M2 = 1.50. Meanwhile, a 2.4 W average output power is achieved operating at 819.710 nm with the pulse width of ~25 μs at 500 Hz, the linewidth of 0.8 pm, and beam quality factor of M2 = 1.20, which is end-pumped by a frequency-doubled 1064 nm Nd:YAG laser. Moreover, double resonant fluorescence in sodium cell with two step excitation of sodium atom from 3S1/2 to 3D5/2 via 3P3/2 level is observed clearly by tuning the wavelength of 589 and 819.7 nm beams. In the proof-of-principle experiment, it is preliminarily verified that this laser system is expected to be applied to the sky experiment.

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.

We propose and demonstrate a new approach to scale the average output power with narrow linewidth and good beam quality simultaneously for a 1319 nm laser. A polarization and sequence pulsed beam combining technology is developed to add two lasers. Each laser is based on a quasi-continuous-wave diode-pumped Nd:YAG master-oscillator power-amplifier system. One provides output power of 81 W with s-polarization, M 2 = 1.49, and a repetition rate of 500 Hz. Another also operates at 500 Hz, but delivers power of 78 W with M 2 = 1.47 and p-polarization. After combination, a maximum average power of 156 W with beam quality of M 2 = 1.5 is achieved, corresponding to a combining efficiency of 98.1%. The combined beam has a 1 kHz repetition rate with 120 μs pulse duration and ~0.3 GHz linewidth. To the best of our knowledge, this is a record-high output power for the solid-state 1.3 μm lasers. All results indicate the technique of polarization beam in conjunction with sequence pulsed beam combining not only allows the scaling of the laser power while maintaining narrow linewidth and good beam quality, but also is an effective approach for increasing the pulse repetition rate.

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.

We demonstrated a high-average-power, narrow-linewidth, quasi-continuous-wave diode-side-pumped 1319 nm Nd:YAG twisted-mode laser oscillator with a linearly polarized TEM00 mode. The resonator is based on a symmetrical convex–convex structure with a two-rod configuration for birefringence compensation, working in a thermally near-unstable cavity. With an optimum cavity length of 940 mm, a 39.4 W linear polarized 1319 nm laser is obtained with a good beam quality of M 2 = 1.21 and a linewidth of ~250 MHz, and the corresponding brightness is as high as 1.55 GW cm−2. The laser is operated at a repetition rate of 500 Hz and pulse duration of 150 µs. To the best of our knowledge, this is the highest output power 1319 nm laser with narrow-linewidth from diode-pumped Nd:YAG lasers, and is the first report on the twisted-mode laser operation at the 1.3 µm region.

We demonstrate a compact, high-power, quasi-continuous-wave (QCW) end-pumped 1319 nm Nd:YAG slab amplifier laser with good beam quality. The laser is based on a QCW pulse Nd:YAG master oscillator and Nd:YAG slab amplifier with multi-pass zigzag architecture. The amplifier operates at a pulse repetition frequency of 500 Hz and pulse width of ∼105 μs, delivering a maximum output power of 51.5 W under absorbed pump power of 217.8 W and corresponding to an extraction efficiency of 14.2%. The beam quality factor is measured to be Mx2=1.61 and My2=1.81 in the orthogonal directions. To the best of our knowledge, this is the first compact, high-power, high-beam-quality QCW Nd:YAG amplifier at 1319 nm based on a multi-pass zigzag slab structure.

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 Miller's rule quantitatively.

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.

We demonstrated a high average power, narrow-linewidth, quasi-CW diode-pumped Nd:YAG 1064 nm laser with near-diffraction-limited beam quality. A symmetrical three-mirror ring cavity with unidirectional operation elements and an etalon was employed to realize the narrow-linewidth laser output. Two highly efficient laser modules and a 90° quartz rotator for birefringence compensation were used for the high output power. The maximum average output power of 62.5 W with the beam quality factor M(2) of 1.15 was achieved under a pump power of 216 W at a repetition rate of 500 Hz, corresponding to the optical-to-optical conversion efficiency of 28.9%. The linewidth of the laser at the maximum output power was measured to be less than 0.2 GHz.

A low-timing-jitter high-power semiconductor saturable absorber mirror mode-locked picosecond (ps) 1063 nm Nd:GdVO4 master oscillator power amplifier is presented. Using a single-pass Nd:GdVO4 amplifier, an amplified laser with 21.5 W output power and 8.3 ps pulsewidth was achieved at 250 MHz repetition rate. Employing a servo control, an average RMS timing jitter of ∼222 fs was realized. This laser can be used as a drive laser for photocathode injectors in free-electron lasers.

We report a high power high beam quality quasi-continuous-wave (QCW) diode-end-pumped Nd:YAG slab amplifier at 1319 nm. The strongest 1064 nm parasitic oscillation has been successfully suppressed by reasonable coating design. In a five-pass configuration, the amplifier yields a 42.3 W linearly polarized 1319 nm output at repetition rate of 1 kHz with pulse duration of 75 μs and beam quality factors of Mx2 = 1.13 and My2 = 2.16 in the orthogonal directions. The fluctuation of the amplifier output power is measured to be ±0.6 %. Furthermore, a computational model of QCW pulse amplification is employed to examine the amplification process.