Efficient diode-pumped Nd:YVO4 continuous-wave laser at 1.34 μm

We report a high-power continuous-wave(cw) diode-pumped efficient 1.34 μm Nd:YVO₄ laser. The laser properties of a low Nd³⁺-doped concentration of the Nd:YVO₄ crystal operating at 1.34 μm formed with a simple plane-concave cavity have been demonstrated. With the incident pump power of 22 W, an output power of 8.24 W was obtained, giving an optical conversion efficiency of 37.5% and slope efficiency of 40%. The thermal effects of cw end-pumped solid-state lasers were studied.     

Laser output power over 5 W at 1.06 μm for Nd:GdVO4 single crystal

In this paper, we report the polarization absorption spectra from 400 to 850 nm, polarization emission spectra from 1050 to 1100 nm and laser properties of an Nd:GdVO₄ crystal. An output power of up to 5.29 W at 1.06 μm has been achieved with a 3×3×3 mm Nd:GdVO₄ crystal sample when it is pumped by a cw laser diode.     

1.3414 μm Nd:YAP pulse laser in Q-switched mode

In this paper, a flash-lamp pumped 1.3414 μm Nd:YAP Q-switched pulse laser are presented. The experimental results for about 45 ns of pulse duration and more than 300 mJ of output energy have been obtained and discussed.     

热效应对高功率b轴Nd+CrNd:YAP连续激光器输出的影响

本文在文献[1]的基础上提出了含有椭圆折射率分布介质谐振腔的设计方法。分析了b轴_Nd+Cr^Nd:YAP连续激光器中热效应对激光横向场分布,输出偏振方向以及输出功率的影响。考虑了这种影响后,已从φ5.8×111mm的Nd:YAP棒和φ6.4×100mm的Nd+Cr:YAP棒中得到了163W和152W的输出,器件效率分别为2.26％和2.11％,输出激光的退偏度为1/2900 关键词：     

射频超导腔加速性能的改进

为提高超导加速腔的加速梯度和Q值，改进了薄膜型超导腔的加速性能。研究证明，对于铜铌溅射腔，在无氧铜衬底和铌膜之间加入NbN 层可以提高铌膜的超导转变温度，改善晶格结构；对纯铌超导腔提出了改进方法，在传统的纯铌超导腔表面制备多层的超导-绝缘-超导复合膜可以屏蔽Nb腔表面的界面场，提高超导腔的临界磁场，从而提高了铌腔的加速梯度。     

A compact 1.06/1.32/2.94 μm pulsed laser for dentistry

A three-wavelength pulsed laser for dental application is developed. The laser houses the Nd:YAG resonator (1.06/1.32 μm) for soft-tissue treatment and Er:YAG resonator (2.94 μm) for caries removal and fits and fissure treatment. Two heads share the cooling unit and two identical high-voltage power supply modules in order to achieve compactness. The Nd:YAG laser has 10 W at 1.06 μm and 7 W at 1.32 μm with a pulse duration of 100 μs. An Er:YAG laser of 2.94 μm has 3.5 W, 20 Hz and a pulse duration of 250 μs. The beams are delivered through fibers and the laser size is 75×55×32.5 cm.     

Investigation on achieving the diode-pumped weak line laser at 1.3 μm

In this paper, a continuous-wave (CW) diode-side-pumped Nd:YAlO₃ (Nd:YAP) laser operating at the weak line of 1339 nm has been achieved and investigated. The output of the 1339 nm laser was realized based on the polarization selection and reasonable transmittance design. The relationship between the output powers and resonator lengths of the 1339 nm Nd:YAP laser has been studied and the optimum resonator length was adopted to improve the output power. As high as 31.3 W output power of the a-axis polarized 1339 nm laser has been obtained at the pumping power of 555 W with the optical-optical and slope efficiencies to be 5.6% and 13%, respectively. This work will provide an effective way to obtain the weak line lasers for potential applications in spectroscopy, coherent terahertz generation, etc.     

Optimal design for a diode-pumped high-power high-efficiency high-beam-quality laser

We have demonstrated and analyzed a high-power high-efficiency high-beam-quality continuous-wave (cw) Yb:YAG laser, which is directly pumped into the upper lasing level by a fiber-coupled laser diode with a center wavelength of 969 nm. To achieve high efficiency and high beam quality simultaneously, we carried out a series of comparing experiments by changing the laser-medium length and pump-beam waist radius. From the cw Yb:YAG laser with a 5.0-at.%-Yb³⁺-doped and 5-mm-long crystal, an output power of 19.0 W has been obtained for a pump-beam waist radius of 138 μm. The maximum slope efficiency and optical-to-optical conversion efficiency are 78.9% and 55.3%, respectively. The M² factors of the laser beam are 1.33 in the vertical direction and 1.82 in the horizontal direction.     

High-power end-pumped CW Nd:GdVO4 laser formed with a flat–flat cavity

Formed with a flat–flat resonator, a diode-laser-array end-pumped CW Nd:GdVO₄ laser at 1.06 μm, capable of generating 8.6 W of TEM₀₀ output power with optical conversion efficiency of 43% and slope efficiency of 48%, has been developed. The laser beam was nearly diffraction limited, with the beam quality factor measured to be M²=1.22. Under the conditions of multi-mode operation, the laser was able to produce 11.2 W of low-order transverse mode radiation (M²<2) at the incident pump power of 22 W, giving an optical conversion efficiency of 51%, and a slope efficiency of 55%.     

Q-switched NYAB laser end-pumped by a high-power diode-laser array

A diode-laser array end-pumped acousto-optically Q-switched NYAB laser operating at both 1.06 and 0.53 μm has been demonstrated. An average output power of 1.3 W at 1.06 μm at a pulse repetition frequency (PRF) of 60 kHz was obtained with an optical conversion efficiency of 18.1% and a slope efficiency of 21.3%. At the incident pump power of 6.1 W, the 1.06 μm shortest laser pulse was reached at PRF of 20 kHz with FWHM width measured to be 32 ns, yielding a largest pulse energy of 30 μJ, and a highest peak power of 938 W. The attainable maximum average green power was found to be 185 mW, with an optical conversion efficiency of 3%.     

Recent progress in the development of type II interband cascade lasers

Type-II interband cascade lasers combine the advantage of an interband optical transition with interband tunneling to enable the cascading of type-II quantum well active regions as is done in type-I quantum cascade laser. The relatively high radiative efficiency resulting from interband optical transitions translates into very low-threshold current densities, and when combined with the high quantum efficiency of cascade lasers, this diode laser design has the potential to operate under cw conditions at room temperature with high output power. Experimental results have already demonstrated some of this potential including high differential external quantum efficiency (>600%), high peak output power (6 W/facet at 80 K), high cw power conversion efficiency (>17% at 80 K), and operation at 300 K under pulsed conditions. Recent work aimed at reducing device thermal resistance and increasing cw operating temperature is reviewed including the demonstration of significant reductions in thermal resistance (averaging 25 K/W or 40% for 1-mm-long devices), 80 K cw operation at 3.4 μm with high-power conversion efficiency (23%) and high differential external quantum efficiency (532%), and cw operation up to 214 K.     

Rotating-disk diode-pumped continuous-wave Nd:YAG laser

Continuous-Wave (CW) diode-laser-pumped experiments using rotating Nd: YAG disk(s) have been performed in the input-power range of 1–6 W and rotation-speed range of 0–25 Hz. With a single Nd: YAG disk in the laser cavity, about 1.56 W of output power at 1.06 µm due to the Nd³⁺ (⁴ F _3/2–⁴ I _11/2) transition at an absorbed input power of 4.2 W has been observed, leading to an optical-to-optical conversion efficiency of over 37% and slope efficiency of 52% using 7.5% transmission output coupler. The laser output power has been observed to decrease by either increasing the number of Nd:YAG disks in the cavity or increasing the rotation speed of the disk(s).     

High-power, continuous-wave, singly resonant optical parametric oscillator based on MgO:sPPLT

We report a high-power, widely tunable, cw singly resonant optical parametric oscillator (OPO) based on MgO:sPPLT. The OPO is pumped in the green by a cw diode-pumped Nd:YVO(4) laser at 532 nm and can provide continuously tunable output across 848-1430 nm. Using a 30 mm crystal and double-pass pumping, an oscillation threshold of 2.88 W has been obtained, and single-pass idler powers in excess of 1.51 W have been generated over 1104-1430 nm for 6W of pump power at an extraction efficiency of 25.2% and photon conversion efficiency of 56.7%.     

6.2 W laser-diode end-pumped continuous-wave Nd:YALO3 laser at 1.34 μm

We report a compact and efficient LD end-pumped linearly polarized Nd:YAP laser operating at 1.34 μm. The laser system with different crystal lengths, output couplers and cavity types were compared. Based on optimizing of the pump system and laser cavity, 6.2 W laser radiation at 1341.4 nm with c-axis polarized was achieved, corresponding to an optical conversion efficiency of about 24.8% with respect to the incident pump power. The laser threshold was only about 1.3 W and the optical slope efficiency was up to 27.2%.     

Growth and laser properties of Nd:Ca4YO(BO3)3 crystal

Nd:Ca₄YO(BO₃)₃ (Nd:YCOB) crystal was grown by the Czochralski method, and its structure was measured by using a four circle X-ray diffractometer. The transparent spectrum from 200 to 2600 nm was measured at room temperature. The fluorescence spectrum near 1.06 μm showed that the main emission wavelength of Nd:YCOB crystal was centered at 1060.8 nm. Laser output at 1.06 μm has been demonstrated when it was pumped by a Ti:sapphire laser at the wavelength of 794 nm, the highest output power was 68 mW under pumping power of 311 mW, the pumping threshold was 163 mW and slope efficiency was 46.9%. The self-frequency doubled green light has been observed when it was pumped by a Ti:sapphire or a laser diode (LD). A 14.5 mm Nd:YCOB crystal sample cut at (θ, φ)=(90°, 33°) was used for type I second-frequency generation (SHG) of the 1.06 μm laser pulse. The SHG conversion efficiency was 22%.     

High-power, high-efficiency cw diode-pumped Tm:YAP laser emitting at 1.99?μm

We elaborate a high-power, high-efficiency cw Tm:YAP laser dual-end-pumped by the laser diode. With 41.9?W pumping power, we obtain a maximum cw output power of 14.7?W at 1988?nm with a slope efficiency of 43.8%, corresponding to an optical conversion efficiency of 35.1%. At the maximum laser output, we measure a beam quality of M ²?~?1.9.     

Oscillation conditions of cw simultaneous dual-wavelength Nd：YAG laser for transitions 4F3／2-4I9／2 and 4F3／2-4I11／2

The operating condition of a cw simultaneous dual-wavelength Nd:YAG laser for both {}^4F_{3/2}-{}^4I_{9/2} (quasi-three-level system) and {}^4F_{3/2}-{}^4I_{11/2}(four-level system) transitions is studied. According to this condition, the cw simultaneous dual-wavelength at 1.06μm and 946 nm in Nd:YAG crystal has been realized experimentally through an adaptive coating design of the cavity mirrors. A total power output of 2.5W of the dual-wavelength at 946nm and 1.06μm has been achieved with an optical conversion efficiency 14.3%. The experimental results are in good agreement with the theoretical analysis.     

Efficient frequency upconversion of coherent radiation from 10.26 to 1.187 μm in a GaSe crystal

Frequency upconversion of laser pulses at 10.26 μm to those at 1.187 μm was achieved in the presence of Nd:YAG laser pulses based on difference-frequency generation in a 10 mm-long GaSe crystal. The highest power conversion efficiency for the parametric conversion was determined to be 20.9%, corresponding to the photon conversion efficiency of 2.42%. This value is two orders of magnitude higher than the highest value reported on GaSe in the literature. The saturation of the output power at 1.187 μm as the input power at 10.26 μm was increased, due to the back conversion, i.e. 1.187 μm + 10.26 μm → 1.064 μm, was clearly evidenced. Such a parametric process has potential for achieving sensitive detections of mid-infrared radiation.     

1.6 W of TEM00 cw output at 1.06 μm from Nd:CNGG laser end-pumped by a fiber-coupled diode laser array

In this paper we demonstrated and analyzed a high-power cw Nd:CNGG laser end-pumped by a fiber-coupled diode laser array in a convex–concave-type cavity. TEM₀₀ mode output power of 1.63 W was obtained with 27% optical-to-optical conversion efficiency and slope efficiency of 44.5%. Thermal lensing and its variation with the incident pump power for this crystal have been measured. The coefficient for pump power induced diffraction losses of Nd:CNGG crystal have also been estimated for this laser configuration.     

LD-pumped actively Q-switched Nd:GdVO4/KTP red laser

LD-pumped actively Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP red laser has been introduced. A maximum red average output power of 0.78 W at 671 nm was obtained at pulse-repetition frequency (PRF) of 15 kHz and the optical conversion efficiency was 6.5%. At the incident pump power of 12 W, the shortest laser pulse occurred at PRF of 15 kHz. Its full-width at half-maximum and the highest peak power were measured to be 35.8 ns and 3.38 kW. The largest single pulse energy of 56.3 μJ was achieved at PRF of 10 kHz. The influence factors on the Q-switched Nd:GdVO₄/KTP red laser have been discussed.