Search

A yellow continuous wave with beam quality M2 = 4.6 and output power of 4.8 W at 589 nm is generated by intracavity sum-frequency mixing of 1064 nm and 1319 nm radiations of a Nd:YAG laser. To achieve high beam quality at high power, thermally near-unstable flat–flat resonators with two-rod birefringence compensation are designed to obtain the large fundamental mode size inside the Nd:YAG rods and the same beam width inside the KTP crystal. The optimal intracavity power ratio of both 1064 nm and 1319 nm beams is also considered. The output power fluctuation of the yellow laser remains less than 5% in four hours.

We demonstrate the improvements of both beam quality and thermal depolarization loss of an all-solid-state heat-capacity Nd:YAG laser with repetition rate of 50 Hz, for the first time to our best knowledge, compared with the conventional steady-state laser. The beam quality of the heat-capacity laser has been improved three times higher than the conventional steady-state laser within the lasing periods of 60 s. The depolarization loss caused by thermo-optical effects which is definitely considerable in steady-state Nd:YAG laser has almost not been observed under heat-capacity operation. Design and operations of the all-solid-state heat-capacity Nd:YAG laser with average output power of 25 W with repetition 50 Hz are also studied with the optical-to-optical efficiency of 33.3%.

An efficient acousto-optically Q-switched extracavity frequency-doubled 532nm laser based on a diode-end-pumped master oscillator power amplifier (MOPA) is demonstrated. With a type I non-critically phase-matched LBO, 26W of average power at 532nm in a near diffraction limited mode at a repetition rate of 30kHz was generated under 43W pump power of 1064nm Nd:YVO4 laser, which correspond to a frequency-doubling conversion efficiency of 60%.

A compact diode-side-pumped Tm:YAG laser is presented, which can output 51 W of cw power at 2.02μm. The Tm:YAG rod is side pumped by nine diode arrays with the central wavelength of 783nm and the with bandwidth of about 2.5 nm at 25° C. To decrease the thermal effect on the both ends and dissipate the heat effectively, one composite Tm:YAG rod with the undoped YAG end caps and the screw threads on the side surface of the rod is used as the laser crystal. The maximum optical-to-optical conversion efficiency of the 2.02-μm laser output is 14.2%, with a slope efficiency of 26.8%.

A simplified n- ZnO/ p- Si heterojunction has been prepared by growing n- type ZnO rods on p- type silicon wafer through the chemical vapour deposition method. The reflectance spectrum of the sample shows an independent absorption peak at 384 nm, which may be originated from the bound states at the junction. In the photoluminescence spectrum a new emission band is shown at 393 nm, besides the bandedge emission at 380 nm. The electroluminescence spectrum of the n- ZnO/ p- Si heterojunction shows a stable yellow luminescence band centred at 560 nm, which can be attributed to the emission from trapped states. Another kind of discrete ZnO rod has also been prepared on such silicon wafer and is encapsulated with carbonated polystyrene for electroluminescence detection. This composite structure shows a weak ultraviolet electroluminescence band at 395 nm and a yellow electroluminescence band. These data prove that surface modification which blocks the transverse movement of carriers between neighbouring nanorods plays important roles in the ultraviolet emission of ZnO nanorods. These findings are vital for future display device design.

A folded four-mirror cavity with a composite Nd:YAG rod is optimized to obtain high efficient cw 473 nm blue output. The laser could operate stably in the region of the thermal-lens focal length from 20 mm to 70 mm. LBO is used for intracavity frequency doubling of the 946 nm transition of Nd:YAG and the optimum LBO length is investigated. A maximum output power of 2.1 W in the blue spectral range at 473 nm is achieved with 30-mm-long LBO, corresponding to an optical conversion efficiency of 9.1%.

A 17.7 W average power output at 355 nm by the third harmonic generation (THG) of 1064 nm light has been obtained with the nonlinear optical crystal CsB3O5 (CBO). The fundamental light source is a diode-pumped Nd:YAG laser with a pulse duration of 70 ns and a repetition rate of 7 kHz. A CBO crystal cut for type-II PM angles is used in the experiment. The THG energy conversion efficiency with CBO is twice as large as that with LBO. As a THG crystal, CBO has better performance than that of LiB3O5 crystal (LBO).

A high power and high efficiency laser head with five dual-line diode arrays for the side-pumped Nd:YAG rod is developed. By mounting two laser heads of this kind and a quartz 90-degree rotator into a thermally-near-unstable symmetrical flat–flat resonator, a continuous-wave power output of 1157W at 1064nm is obtained with a beam quality factor M2 of ~39. To the authors' knowledge, this is the highest power output at 1064 nm for the diode-side-pumped two-rod Nd:YAG laser.

By using a diode-side-pumped Q-switched Nd:YAG rod laser based on a thermally-near-unstable flat-flat resonator, an intracavity-frequency-doubled green beam generation is investigated. Output power 140 W is obtained at a repetition rate of 10 kHz and a pulse width of 110 ns. The green beam quality factors M-x(2) and M-y(:)2 which are measured by a laser beam analyser, are 10.65 and 10.85, respectively. at output, power of 124 W.

We report the generation of high-power red light radiation of 11.2 W in a LiB3O5(LBO) crystal with intra-cavity frequency doubling of two compact and simple side-pumped Nd:YAG laser modules under a repetition rate of 3.5 kHz. The pulse width of output is about 180±20 ns. The beam quality of the M2 value is 15±3 in both the directions. This excellent laser performance demonstrates that the Nd:YAG laser with LBO intracavity frequency doubling is an promising method for generating red light with high brightness.

We report on an all-solid-state high-power quasi-continuous blue light source by the frequency doubling of a signal wave from an optical parametric oscillator (OPO). A 50-mm-long LiB3O5 (LBO) crystal is used for the OPO, which is pumped by a diode-pumped Nd:YAG green laser (10 kHz, 50 ns). Tunable blue emission in a new nonlinear crystal BiB3O6 (BiBO) is obtained with a wavelength range from 450 to 495 nm. The average power of the signal output is as high as 9.3 W from 924 to 970 nm. The maximum output of the blue laser with the second harmonic walk-off compensation is 1.3 W average power at 470 nm for 6.2 W of OPO signal light at 940 nm.

We report the tunable mid-infrared generation with a periodically poled LiNbO3 (PPLN). Using an all-solid-state-pumped Nd:YVO4 laser as the pump source and a PPLN nonlinear crystal with grating periods of 28.2-30.8 mum, we have achieved wavelength conversion in the 2.90-4.05 mum spectral range by period tuning. The use of confocal cavity design has brought a compact, all-solid-state configuration with an average output powers of idler up to similar to 200 m W. The maximum power of 277 mW was obtained at the wavelength of 3.35 mum.

Six output wavelengths from violet to infrared have been observed simultaneously from an all-solid-state laser pumped optical parametric oscillator in a periodically poled lithium niobate crystal. The output wavelengths can be tuned by varying the quasi-phase matched period and/or temperature. The pump laser is a diode-pumped passive Q-switched Nd:YVO4 laser operated at 1064 nm. Using a crystal with a 29.9 µm grating period, we measured six wavelengths at 448, 515, 532, 630, 773 and 1546 nm and obtained efficient output. We explain the multiwavelength generation by multiwave coupling theory. This phenomenon may have novel applications in photonic devices.

A 33W 589 nm sodium beacon laser with the linewidth of 0.4 GHz and the beam quality of M2 = 1.2 is achieved by sum-frequency mixing 1064 nm and 1319 nm quasi-continuous-wave (QCW) diode-pumped Nd:YAG lasers with a LBO crystal. The repetition rate of the laser is 500 Hz with the pulse width of 120 μs. Compared with the continuous-wave (CW) sodium beacon laser, the QCW microsecond-pulse sodium beacon laser can provide a gatable pulse format to eliminate the interference of atmospheric Rayleigh scattering and reduce stretching phenomenon of the imaging spot for sodium guide star, so the better correction effect can be achieved by using the adaptive optics system with the microsecond-pulse laser. A microsecond-pulse sodium beacon laser prototype is developed to generate a sodium laser guide star which is observed by the 1.8m telescope in Yunnan province.

We demonstrate a diode-side-pumped continuous wave (CW) Nd:YAG laser at 1123 nm with over 100 W's output power and good beam quality. The resonator adopts convex-convex structure working in a thermally near unstable cavity. By precise coating design a single 1123 nm wavelength is delivered. Under the pumped power of 870 W, an output power of 106.5 W is obtained, corresponding to an optical-optical conversion efficiency of 12.2%. The beam quality of M(2) factor is measured to be 5.6. To the best of our knowledge, this is the highest output power with good beam quality for 1123 nm CW Nd:YAG laser.

Output power of 1.1 W and linewidth of 0.7 GHz and beam quality of M2 = 1.2 yellow beam was generated by sum-frequency mixing 1064 nm and 1319 nm radiations of quasi-continuous-wave diode-pumped Nd:YAG lasers inside a pair of KTP crystals. The narrow linewidth 1064 nm and 1319 nm beams were realized by inserting solid etalons in the three-mirrors ring resonators. The wavelength of yellow laser was adjusted and controlled by the control of etalon angle and temperature. To achieve the high beam quality at the average power, thermally near-unstable resonators with two-rod birefringence compensation were designed and employed in the 1064 nm and 1319 nm ring lasers. The high sum-frequency efficiency was obtained by using a pair of KTP crystals with a walk-off-compensated configuration. The power of the diffraction-limited, narrow linewidth and precise-tunability yellow laser was reached to 1.1 W by mixing the 1064 nm beam of 7.5 W and the 1319 nm beam of 3.2 W.

The 1319 nm lasers have important applications in the fields of optical fiber communication, laser medical treatment and laser color display. The Nd:YAG laser pumped by 808 nm laser diode is an efficient alternative to achieving 1319 nm laser output. In recent years, direct pump technology using 885 nm laser diodes has become more promising due to the dramatically reduced thermal effect and improved optical conversion efficiency. Quasi-continuous sodium beacon laser with microsecond pulse duration generated by the sum-frequency of 1319 nm and 1064 nm lasers can provide a gatable pulse format to eliminate the interference of atmospheric Rayleigh scattering and mitigate the spot elongation of sodium guide star to improve imaging accuracy. However, relaxation oscillation in the microsecond pulse could cause the damage to the nonlinear crystal and reduce the efficiency of sum-frequency generation. It is effective to suppress the relaxation by taking advantage of second harmonic generation, in which a nonlinear crystal is utilized to reduce the pulse peaks with higher intensity. In this paper, we demonstrate a high-power relaxation-oscillation-free quasi-continuous microsecond pulse 1319 nm laser by using the dual-end 885 nmdiode-pumped three-mirror ring-cavity. Intra-cavity etalon and customized mirror coating are employed to prevent the 1064 nmand 1338 nmline of Nd:YAG laser crystal from oscillating. A power tuning device, including a thin-film polarizer and a halfwave plate is implemented as the output mirror of ring cavity, which enables continuous adjustment of the out coupling ratio. The output power of the 1319 nm polarized laser is 22.5 W pumped by 150 W 885 nm laser diode. The repetition rate is 800 Hz and pulse width is 150 s. The corresponding optical conversion efficiency is 15%. The beam quality factor M2 is measured to be Mx2= 1.35 and My2=1.24. By precisely adjusting the temperature of etalon viz. adjusting refractive index as well as thickness of the etalon material, laser wavelength is tuned from 1318.888 nm to 1319.358 nm, corresponding to a tunable range of 470 pm and tuning accuracy of 0.7 pm. A 1319 nm frequency doubling crystal KTiOPO4 (5 mm5 mm15 mm, = 59:8 and ϕ = 0) is inserted into the cavity to suppress the relaxation oscillation. The pulse waveform quickly reaches a smooth regime, followed by a pulse spike at the initial stage and the loss of laser output power is only 1%. It is proved that it can be efficiently suppressed by inserting a frequency doubling crystal with negligible power loss. In conclusion, this paper provides a practical and effective technical means for achieving the high-power relaxation-oscillation-free quasi-continuous 1319 nm laser with microsecond pulse duration.

We report the operation of a β-BaB2O4 (BBO) optical parametric oscillator (OPO) broadly tunable in the visible and the near infrared. Quantum efficiency of 22.7% for the signal and 34.1% for the idler corresponding to the total energy conversion efficiency of 25.9% has been achieved. The maximum average output power and the maximum output energy reached 220mW and 22mJ/pulse, respectively. By changing the matching angle of the OPO, the output wavelength was continuously scanned throughout 425-2144nm.

By employing a thermally near-unstable cavity design with two-rod birefringence compensation, average power of 218 W with beam quality of M2 = 20.2 was achieved by intracavity frequency doubling a diode-pumped Nd:YAG laser.

We demonstrate an all-solid quasi-continuous-wave (QCW) narrow-band source tunable to sodium D-2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal. The 1064 nm and 1319 nm lasers are produced from two diode side-pumped Nd:YAG master oscillator power amplifier (MOPA) laser systems, respectively. A 33 W output of 589 nm laser is obtained with beam quality factor M-2 = 1.25, frequency stability better than +/- 0.2 GHz and linewidth less than 0.44 GHz. A prototype 589 nm laser system is assembled, and a sodium laser guided star has been successfully observed in the field test.

A tunable picosecond narrow band β-BaB2O4 (BBO) superluminescent optical parametric self-amplification (OPSA) pumped by the third harmonic of an actively-passively mode-locked Nd:YAG laser has been demonstrated. The output wavelength of the OPSA was tunable from 406.6nm to 2777nm. The maximum energy conversion efficiency was 11%. The maximum peak power of the visible output was as high as 13MW.

We have investigated the generation of highly-efficient blue light in critically type-I phase-matched LiB3O5 (LBO) with intracavity frequency doubling of diode-pumped Nd:YAG laser. A maximum output power of 502 mW at 473 nm blue light was obtained and the overall optical-to-optical efficiency is up to 11.2%. To the best of our knowledge, this is the highest conversion efficiency for 473 mm output using a diode pumped Nd:YAG laser through LBO.

The ultraviolet beam at 266 nm was obtained by fourth harmonic generation of 1064 nm Nd:YAG laser radiation through a nonlinear crystal K2Al2B2O7 (KABO). The fundamental frequency of a flash-lamp pumped Nd:YAG laser was doubled in a β-Ba2B2O4 crystal to generate a second harmonic output at the wavelength of 532 nm, and then doubled again in the KABO crystal to generate the fourth harmonic output at 266 nm. The optical conversion efficiency from 532 to 266 nm was investigated for the first time, and 13% was achieved.

This paper demonstrated a high power and high beam quality diode-pumped 1319-nm Nd:YAG master oscillator-power amplifier laser system. A thermally near-unstable resonator with four-rod birefringence compensation flat-flat cavity was adopted as the master oscillator. A solid etalon was inserted in the unidirectional ring resonator to compress the laser linewidth. Under a repetition rate of 500 Hz and pulse width of 160 μs, the master oscillator delivers an average output power of 16.8 W at 1319 nm with linear polarisation, beam quality factor M2 = 1.16 and linewidth of 3.2 GHz. A double-pass power amplifier with two amplifier stages was employed for higher power scaling and the output power was amplified to be 25.9 W with M2 = 1.43.

A high-efficiency high-power Nd:YAG laser under 885nm laser diode (LD) pumping is demonstrated. The laser crystal is carefully designed, and the overlapping between the pump modes and the laser modes is optimized. The maximum output power at 1064 nm is 87W under the absorbed pump power 127.7W, corresponding to a slope efficiency of 72.4% and an optical-optical efficiency of 68.1%. The optical-optical efficiency is 58.4% for the pump power emitted directly from the LD. To our best knowledge, this is the maximal optical-optical conversion efficiency obtained for the LD end-pumped Nd:YAG lasers so far.

We report a stable high power and high beam quality diode-side-pumped cw green laser from intracavity frequency-doubled Nd:YAG laser with KTP. By using a L-shaped concave-convex resonator, designed with two Nd: YAG rods birefringence compensation, a large fundamental mode size in the laser crystal and a tight focus in the nonlinear crystal could be obtained simultaneously. The green laser delivers a maximum 532nm output power of 23.2 W. Under 532nm output power of 20.9 W, the beam quality factor is measured to be 4.1, and the fluctuation of the output power is less than 1.4% in an hour.

We have developed a high power tunable single-frequency 1064 nm quasi-continuous-wave laser oscillator-amplifier system. By controlling precisely the temperature of etalon in the three-mirror ring traveling-wave oscillating cavity viz. adjusting refractive index and thickness of material to tune laser wavelength, 13.2 W 1064 nm single-frequency quasi-continuous-wave oscillating light with tunable range of 58 GHz is obtained, at repetition rate of 1 kHz and duty ratio of 10%. After the laser beam from the oscillator transfers through the amplifier with two laser heads, the output of the oscillator is amplified to be 44 W and the beam quality factor M2 is measured to be 1.58.

This paper reports a high-power all-solid-state yellow laser based on intracavity KTP crystal sum-frequency generation. In order to achieve high output power，three key techniques are used：Firstly，the system is designed to operate in a pulsed mode to increase the beam quality and optical-to-optical conversion efficiency under the same pump level. Secondly，thermal near-unstable resonator design and two-rod birefringence compensation is used to acquire large fundamental mode size in Nd：YAG rod. Thirdly，by optimizing an L-shaped co-folding-arm plane-concave symmetrical cavity，the two fundamentals have a high spatial overlap in the sum-frequency crystal and satisfy the power ratio requirement. As a result of the applications of these techniques，a quasi-continuous-wave yellow laser with output power of 7.6W and repitition frequency of 1.1kHz is obtained. To the best of our knowledge，this is the highest yellow laser output power produced by an intracavity sum-frequency Nd：YAG laser.

A high-average-power and high-beam-quality diode-side-pumped solid-state Q-switched laser was developed by use of low concentration Nd:YAG crystals with thermally near-unstable resonator design and two-rod birefringence compensation technology. Two orthogonal acousto-optic Q-switches were used to sustain fully holding of the pump gain. The 1064 nm quasi-continuous-wave average output power of 258 W at pump power of 1116 W was achieved with the beam quality factor M2～15.5 at a repetition rate of 10 kHz and a pulse width of 64 ns, corresponding to a peek power of 0.4GW and an optical-to-optical conversion efficiency of 23.1%.

A special prism coupling technique with the KBe2BO3F2 crystal is adopted to produce deep ultraviolet light including the fourth harmonic from an Nd:YAG laser, for which a conversion efficiency as high as 10% has been obtained.

We report here a diode pumped Nd∶YVO4 laser emitting at 1342 and 671nm.A maximum output power of 1.75W at 1342nm was obtained under an incident pump power of 5.45W,with an optical-to-optical conversion efficiency of up to 32.1%.With a type Ⅰ noncritically phase-matched LBO crystal as the intracavity frequency doubler,over 500mW of 671nm light was obtained at 6W of incident pump power,the optical-optical conversion efficiency being 8.3%.The output power fluctuates less than 5% while the temperature change of the LBO crystal oven was maintained ±0.5℃ at the phase-matched temperature.

High power tunable UV laser radiation from 2750A to 3200A has been obtained by second-harmonic generation in a β-BaB2O4 crystal. A maximum frequency doubling efficiency of 41% and a UV output power of 3.7MW have been obtained.

High power tunable UV coherent radiation has been achieved by sum-frequency generation (SFG) in β-BaB2O4 (BBO) crystal. The maximum output power obtained is about 3MW (near 368nm) and 0.75MW (near 222.5nm)

We suggest a new efficient method of laser tuning: the principle of tuning and amplification by self-injection. By this means, the influence of tuning elements on the laser output power is reduced to a minimum, that is, the tuning efficiency can approach 1. This provides a possibility for laser outputs of both high power and narrow bandwidth to be obtained with one laser oscillator. The theoretical and experimental results are given.