Continuous wave and active Q-switched operation of Watt-level LED-pumped two-rod Nd,Ce:YAG laser

A high-performance LED-side-pumped two-rod Nd,Ce:YAG laser with continuous-wave(CW) and acousto–optical(A-O) Q-switched operation is demonstrated in this work. A symmetrically shaped flat–flat cavity with two identical LEDside-pumped laser modules is employed for power scalability. In the CW regime, the maximum output average power of laser at 1064 nm is 4.41 W, corresponding to a maximum optical conversion efficiency of 5.3% and a slope efficiency is 12.4%. In the active Q-switched regime, the pulse energy of laser reaches as high as 0.89 m J at a repetition rate of 800 Hz with a pulse width of 457.2 ns, the corresponding highest peak output power is 1.94 k W and the M~2 factor is measured to be about 8.8. To the best of the authors' knowledge, this is the first demonstration and the highest performance of a CW LED-side-pumped two-rod laser Nd,Ce:YAG with Watt-level output reported so far.

Passively Q-Switched Nd,Cr:YAG Laser Simultaneous Dual-Wavelength Operation at 946 nm and 1.3μm

A diode-end-pumped Q-switched high-efficiency Nd, Cr：YAG laser with simultaneous dual-wavelength emission at 946nm and 1.3μm is demonstrated. The maximum output power of 1.93 W with simultaneous dual-wavelength operation is achieved at an absorbed pump power of 13.32 W and an absorbed slope efficiency of 15.15%. The maximum optical-optical efficiency is 14.49% with pulse widths of 16.38ns at 946nm and 26.65ns at 1.3μm. A maximum total repetition rate of 43.25 kHz is obtained.

High-Power Passively Q-Switched Nd:YAG Laser at 1112 nm with a Cr^(4+):YAG Saturable Absorber

A high-power passively Q-switched Nd：YAG laser operating at lll2nm with Cr4＋：yAO as a saturable absorber is demonstrated. Under 808 nm diode-direct pumping, the maximum average output power of 2.73 W is achieved at the pump power of 16.65 W, corresponding to an optical-to-optical conversion efficiency of 16.4%. At the same time, the pulse width, pulse repetition rate, single pulse energy and peak power are 27.2ns, 9 kHz, 303.3#3 and 11.2kW, respectively. As far as we know, the result gives the highest average output power at 1112nm generated by an 808 nm diode-end-pumped Nd：YAG laser.

Efficient Passively Q-Switched Nd:YAG/Cr4+:YAG/LBO Microchip Laser

Performance of an LD-end-pumped passively Q-switched Nd： YA G/Cr4＋ ： YA G microchip laser operating at 1123 nm is studied. A maximum average output power of 517row with an optical-to-optical conversion efficiency of 12.6% and a slope efficiency of 25.8% is obtained under a pump power of 4.1 W. A minimum pulse width of 1.1 ns with a pulse repetition rate of 20.2kHz is obtained, and the corresponding pulse energy and peak power are 25.6μJ and 23.3kW, respectively. To our knowledge, the 23.3kW peak power is the highest among 1123nm lasers. Additionally, based on the 1123 nm laser, with LBO as the frequency doubler, a 288-mW green-yellow laser at 561 nm is successfully achieved.

Q-switched and Mode-locked Characteristics of Cr^(4+)∶YAG Crystal

The passively Q-switched and mode-locked（QML） characteristics in a diode-pumped Nd∶GdVO4 laser with Cr4+∶YAG saturable absorbers have been demonstrated. A maximum average output power of 710mW has been obtained in the QML laser. The maximum energy of a single Q-switched pulse is 52.5μJ, with the corresponding pulse width of 30ns and the peak power of 1.75kW, at the incident pump power of 7.75W. The repetition rates of the Q-switched envelope and the mode-locked laser pulse are 16.7kHz and 680MHz, respectively.

Efficient Nd:YVO4 laser in-band pumped by wavelength-locked 913.9-nm laser diode and Q-switch operation

An efficient 1064-nm Nd：YVO_4laser in-band pumped by a wavelength-locked laser diode（LD） at 913.9 nm was demonstrated. The maximum continuous wave（CW） output power of 23.4 W at 1064 nm was realized with the incident pump power of 40 W, corresponding to a total optical-to-optical efficiency of 58.5%. This is to the best of our knowledge the highest total optical-to-optical efficiency and output power of Nd：YVO_4laser in-band pumped by a 913.9-nm laser diode.The Q-switched operation of this laser was also investigated. Through a contrast experiment of pumping at 808 nm, the experimental results showed that an Nd：YVO_4laser in-band pumped by a wavelength-locked LD at 913.9 nm had excellent pulse stability and beam quality for high repetition rate Q-switching operation.

Efficient Diode-End-Pumped Actively Q-Switched Nd:YLF/SrWO4 Raman Laser

An efficient diode-end-pumped actively Q-switched Nd：YLF/SrW04 Raman laser is demonstrated. The fun- damental wave is 1047.0nm and the corresponding first-Stocks wave is 1158.7nm. With a pumping power of 10.5 W, the average output power of 2.2 W at 1158.7nm is obtained, with the corresponding optical conversion efficiency of 20.9%. At a repetition rate of 6 kHz, the pulse width of the Raman laser is 8. 7ns and the peak power is calculated to be 42.1 kW. The beam quality factors M2 in horizontal and vertical directions are 1.3 and 1.5, respectively.

Passively Q-Switched Nd:YVO_4 Laser Using a Gold Nanotriangle Saturable Absorber

A passively Q-switched Nd：YVO4 laser at 1064 nm is demonstrated based on a gold nanotriangle saturable absorber（GNT SA）.Under a pump power of 3.82 W,the maximum average output power of 218mW is achieved,corresponding to a slope efficiency of 12.9%.The minimum pulse width is 165ns and the maximum pulse repetition rate is 300kHz at the pump power of 3.48 W.Our results prove that the GNT SA is a promising saturable absorber for near-infrared lasers.

A Single-Longitudinal-Mode Passively Q-Switched Nd:YVO4 Laser Using Black Phosphorus Saturable Absorber

A black phosphorus (BP) saturable absorber (SA) solution with different concentrations (1.0 and 0.5 mg/ml) is fabricated with the liquid-phase exfoliation method. By using the BP-SA, a compact diode-pumped passively Q-switched Nd:YVO4 laser is demonstrated. One reflecting Bragg gratings is used as the output coupler for mode selection. By inserting those BP-SA solutions in the laser cavity, the maximum single longitude mode, Q-switched output powers of 126mW at 692.5 kHz and 149mW at 630.3 kHz are achieved at the pump power of 8.0 W, corresponding to the pulse durations of 144 ns and 196 ns, respectively. Moreover, longitudinal-mode characteristics of Q-switched output laser in different optical cavity lengths based on two-kind BP-SA solution concentrations are investigated. Our results show that BP-SA could also be developed as an effective SA for the Q-switched, single longitudinal mode pulse laser.

Efficient Diode-Pumped Actively Q-Switched Ceramic Nd:YAG/YVO4 Raman Laser Operating at 1657 nm

A diode-pumped actively Q-switched Raman laser is demonstrated, with YV04 employed as Raman active medium, based on a ceramic Nd：YAG laser operating at 1444nm. The first-stokes Raman generation at 1657nm is achieved. A maximum output power of as high as 612mW is obtained under a pump power of 20. 7 W and at a pulse repetition frequency rate of 20kHz, corresponding to an optical-to-optical conversion efficiency of 3%.

Diode-pumped Q-switched Extra-cavity Frequency-dou bled Nd∶YVO_4/KTP Green Laser

A diode-pumped acousto-op ti cal(A-O) Q-switched extra-cavity frequency-doubled Nd∶YVO_ 4/ KTP (KTiO PO_ 4) green laser formed with a simple plane-plane cavity has been demonst rated. With the incident pump power of 12.7 W, A-O Q-switched average output power at 1 064 nm was 3.81 W with a duration of 25 ns at a repetition rate of 20 kHz, extra-cavity frequency doubling with KTP as the nonlinear crystal y ielded the maximum output power of 1.92 W at 532 nm, the corresponding optical conversion efficiency from 1 064 nm to 532 nm light is 50.4%. The continuous -wave(CW) laser properties of diode-pumped Nd∶YVO_ 4 crystal operating at 1 064 nm have been studied. With the incident pump power of 25 W, the maximu m CW output power of 13.81 W was obtained with the corresponding optical conver sion efficiency of 55.24%.

Tunable Nd,La:SrF2 laser and passively Q-switched operation based on gold nanobipyramids saturable absorber

A novel Nd, La：SrF_2 disordered crystal is prepared, and its continuous-wave wavelength tuning operation is performed for the first time. Employing a surface plasmon resonance（SPR） based gold nanobipyramids（G-NBPs） saturable absorber,we obtain a compact diode-pumped passively Q-switched Nd, La：SrF_2 laser. The stable Q-switched pulse operates with the shortest pulse duration of 1.15 μs and the maximum repetition rate of 41 k Hz. The corresponding single pulse energy is 2.24 μJ. The results indicate that G-NBPs could be a promising saturable absorber applied to the diode-pumped solid state lasers（DPSSLs）.

Diode-pumped Doubly Q-switched Nd∶YAG Laser with Acoustic-optical Modulator and Cr^(4+)∶YAG Saturable Absorber

A diode-pumped doubly Q-switched Nd∶YAG laser operating at 1064nm both with an acoustic-optical(AO)modulator and Cr4+∶YAG saturable absorber in the cavity is demonstrated.At the incident pump power of 11.8W the laser can generate stable 8ns pulse with the peak power of 23.6kW at a 10kHz repetition rate.The pulse temporal profile is more symmetric and shorter compared with that of passively Q-switched lasers with only AO-active and Cr4+∶YAG.A reasonable analysis is developed to explain the experimental results theoretically.

Diode Pumped High Peak Power Quasi Q-Switched and Passively Q-Switched Nd:YVO₄Lasers at 1064 nm and 532 nm using Cr:YAG and KTP crystals

Diode end-pumped solid-state lasers have the potential to yield high quality laser beams with high efficiency for laser range finding and warning receiver applications as well as day and night military laser designation systems. In this paper we presents theoretical calculations using Advanced Dynamics Professional LASCAD software and experimental studies for a high power pigtailed fiber diode laser module of 8 W operating at 808 nm with a specially designed high efficiency cooling system, end pumped high-efficiency Nd:YVO4 laser of 3 × 3 × 10 mm rod and overall cavity length of 44 mm. To the best of our knowledge a self Q-switching effects was generated in Nd:YVO4 laser by changing the cavity dimensions and the position of the intracavity KTP crystal at certain regime of operation for the first time, in which the cavity length is reduced to be 30 mm and the distance between Nd:YVO4 rod and KTP crystal is only 1mm. Self Q-switched laser pulse at 532 nm with high peak power of 96 W, pulse width of 88 ns at FWHM and repetition rate of 400 kHz was achieved. Experimental studies of a passive Q-switched Nd:YVO4 laser using Cr:YAG crystal with three different transmissions of 30%, 40% and 70% were investigated. Passive Q-switched laser pulse at 1064 nm and narrow line width of less than 1.5 nm with highest peak power of nearly 18 kW, short pulse width of less than 4 ns at FWHM and higher repetition rate of 45 kHz using Cr:YAG with transmission of 30% was achieved for the first time.

Simulation of Diode-Pumped Q-Switched Nd:YAG Laser Generating Eye-Safe Signal in IOPO Environment

Numerical simulation of diode-pumped Q-switched Nd:YAG laser leading to the generation of eye-safe signal in singly resonant Intracavity Optical Parametric Oscillator (IOPO) is presented. Starting from rate equations, the time dependent laser equations have been solved numerically, whereas the space-dependent OPO equations analytically. Our results show that 1.4 J diode laser (810 nm) pulse with 200 msec width, delivers 30 mJ Nd:YAG laser (1064 nm) pulse with 5 n-second width. This Nd:YAG laser further generates 9 mJ eye safe signal (1570 nm) pulse with 2.5 n-second width.

脉冲Nd:YAG激光照射对实验性大鼠慢性牙周炎的作用

目的：探讨脉冲Nd：YAG激光照射对大鼠实验性牙周炎牙周临床指标及牙周组织中一氧化氮（NO）含量的影响。方法：健康Sprague—Dawley大鼠共64只，随机分为8组，正常对照组（N组），药物对照治疗组（D组），牙周炎阳性对照组（P组），其余5组按照给予不同剂量激光照射治疗。末次治疗15d后测量牙周临床指标牙龈指数（GI），牙槽骨吸收值ABL（Alver bone loss），菌斑指数（plaque index，PLI），采用分光光度仪测定大鼠牙周组织中NO的含量。结果：各剂量组ABL、NO值较未照射组（P组）显著降低（P〈0．05）。1．5～2．0W 20pps剂量组激光照射后牙周指数均较P组显著降低（P〈0.05），与D组无显著差异。结论：在1．5～2．0W 20pps剂量范围内，采用脉冲Nd：YAG激光牙周袋内照射能有效改善牙周指数，降低实验大鼠牙周组织中NO含量，耗到治疗牙周书的作用。

Q开关Nd：YAG激光治疗褐青色痣术后皮肤修复应用胶原贴冷敷膜的效果观察

目的观察胶原贴冷敷膜对Q开关Nd：YAG激光治疗褐青色痣术后皮肤修复的效果。方法将126例褐青色痣患者通过随机数字表法分为观察组和对照组，每组各63例。观察组于术后外敷胶原贴冷敷膜；对照组仅单纯使用冰敷。术后随访1周，观察两组间皮肤修复情况及患者主观疼痛程度。结果观察组的皮肤修复速度及患者主观疼痛感受均明显优于对照组，组间比较差异有统计学意义（P〈0．05），观察组未出现过敏等不良反应。结论Q开关Nd：YAG激光治疗褐青色痣术后应用胶原贴冷敷膜可有效促进皮肤修复，改善患者疼痛程度。

Efficient corner-pumped Nd:YAG/YAG composite slab laser

A corner-pumped type is a new pumping type in the diode-pumped all-solid-state lasers, which has the advantages of high pump efficiency and favourable pump uniformity. A highly efficient corner-pumped Nd：YAG/YAG composite slab laser is demonstrated in this paper. The maximal continuous-wave output power of the 1064 nm laser is up to 18.57 W with a slope efficiency and an optical-to-optical conversion efficiency of 44.9% and 39.8%, respectively. Inserting an acousto-optic Q-switch in the cavity, the highest average output power of the quasi-continuous wave 1064 nm laser of 6.73W is obtained at a repetition rate of 9.26 kHz. The experimental results show that a corner-pumped type is a kind of feasible schedules in the design of diode-pumped all-solid-state lasers with low or medium output powers.

Experimental study of electro-optical-switched pulsed Nd:YAG laser

We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd：YAG laser. We ex- perimentally study and compare the performance of the pulsed Nd：YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configu- ration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.

Induction of oxidative stress in human aqueous and vitreous humors by Nd:YAG laser posterior capsulotomy

AIM： To evaluate whether the Q-switched Nd：YAG laser treatment applied in routine capsulotomy elicits oxidative stress in aqueous and vitreous humors. METHODS： Thirty-six patients who had to undergo a 25 gauge pars plana vitrectomy due to vitreoretinal disorders were enrolled, 15 of them underwent a Q-switched Nd：YAG laser capsulotomy 7 d before vitrectomy due to posterior capsule opacification（PCO）（Nd：YAG laser group） while the remaining 21 patients were not laser treated before vitrectomy（no Nd：YAG laser group）. Samples of the aqueous and vitreous humors were collected during vitrectomy from all patients for the assessment of oxidative parameters which were compared between the Nd：YAG laser group and no Nd：YAG laser group. Thiobarbituric acid reactive substances（TBARS）, a product of membrane lipid peroxidation, nitrite levels, the antioxidative activities of SOD and catalase, the 4-HNE-protein conjugate formation, indicating structural modifications in proteins due to lipoperoxidation, were assessed in aqueous and vitreous samples. RESULTS： In the human vitreous humor TBARS levels are significantly higher in the Nd：YAG laser group compared to the no Nd：YAG laser group and importantly, there is a significant correlation between the TBARS levels and the total energy of Nd：YAG laser used during capsulotomy.Moreover the anti-oxidative activities of SOD and catalase were significantly decreased by Nd：YAG laser treatment, both in aqueous and vitreous humors. In accordance with the TBARS data and anti-oxidative enzyme activities, significantly higher levels of proteins were conjugated with the lipoperoxidation product 4-HNE in the aqueous and vitreous humors in the Nd：YAG laser-treated group in comparison to no Nd：YAG laser group. CONCLUSION： These data, clearly suggest that any change that Q-switched Nd：YAG photo disruption may cause in the aqueous and vitreous compartments, resulting in a higher level of oxidative damage might be of considerable clinical significance particularly by accelerating the aging of the anterior and posterior segments of the eye and by worsening the intraocular pressure, the uveal, the retinal（especially macular） pathologies.