Kilohertz high power extracavity KGW yellow raman lasers based on pulse LD side-pumped ceramic Nd: YAG

We report an efficient operation of a kilohertz nanosecond extracavity KGd(WO₄)₂ (KGW) crystal Raman yellow laser, which is pumped by a 532 nm lasers based on pulse laser diode (LD) side-pumped ceramic Nd: YAG, BBO electro-optical Q-switched and LBO crystal extracavity frequency doubling. With the 5 W, 10 ns and 1 kHz output power pumped at 532 nm, we obtained 2.58 W, 7.4 ns, 1 kHz second Stokes Raman laser output at 579.54 nm for 768 cm⁻¹ Raman shift of KGW crystal, corresponding to a conversion efficiency of 51.4%. By changing the KGW crystal orientation, we further obtained 3.18 W, 7.8 ns, 1 kHz Raman pulses at 588.33 nm for 901 cm⁻¹ Raman shift, corresponding to a conversion efficiency of 63.3%. The beam quality factors M² of 579.54 and 588.33 nm were (M _x−579.54² = 5.829, M _y−579.54² = 6.336) and (M _x−588.33² = 6.405, M _y−588.33² = 6.895), respectively.     

LD side-pumped 41 W high beam quality acousto-optical Q-switched single-rod Nd:YAG laser

We report a LD side-pumped high beam quality (M _x ² = 1.20 and M _y ² = 1.19) acousto-optic (AO) Q-switched single-rod Nd:YAG laser with a TEM₀₀-mode dynamic stable cavity. At the pump power of 600 W, 41 W TEM₀₀-mode 1064 nm laser was achieved with electro-optical conversion efficiency of 7%. The repetition rate and pulse width were 30 kHz and 102 ns, respectively with pulse energy of 1.4 mJ and peak power of 13 kW. Up to 24 W of 532 nm green laser was generated by external frequency doubling, corresponding to 59% optical conversion efficiency.     

885 nm LD end-pumped 22.7 W high beam quality electro-optical Q-switched Nd:YAG laser

We report an 885 nm laser diode (LD) end-pumped high beam quality (M _x ² = 1.322, M _y ² = 1.235) electro-optical Q-switched Nd:YAG laser with TEM₀₀-mode output for the first time. At the absorbed pump power of 59.5 W, a 22.7 W 1064 nm laser was achieved at 10 kHz repetition rate with optical-to-optical efficiency of 38.1%. The maximum pulse energy and shortest pulse width were 5.1 mJ and 14.5 ns at 2 kHz repetition rate, and the calculated peak power was 352 kW.     

30 W output of short pulse duration nanosecond green laser generated by a hybrid fiber-bulk MOPA system

We reported a 30 W average output power 532 nm green laser with 5 ns pulsed duration working at 80–100 kHz generated by a hybrid MOPA system. The hybrid MOPA system consisted of a fiber amplifier and two solid-state amplifiers producing 77 W 1064 nm at pulse repetition rates of 80–100 kHz. The IR-to-green optical conversion efficiency was 44.7% at the working point of 100 kHz. The beam quality of green laser was measured better than M ² < 1.6 in both orthogonal directions. Nanosecond 532 nm lasers with short pulsed duration could be practicable in silicon-based material processing in the Photovoltaic industry.     

High repetition rate intracavity frequency doubled LD side-pumped ceramic Nd:YAG green laser based on BBO electro-optical Q-switch

a high repetition rate and high power 532 nm green laser generated by intracavity frequency doubling of a 808 nm laser diode side-pumped ceramic Nd:YAG laser based on BBO electro-optical Q-switch has been demonstrated. in the simple V-folded cavity, the maximum green laser average power 32.6 W was obtained with a pulse width of 58.5 ns at a repetition rate of 10 kHz by using a LBO crystal for frequency doubling, corresponding to a conversion efficiency of 10.9% from diode pumping power to green laser power. An instability of 1.9% was measured over a period of 30 minutes and the beam quality factors were measured to be M _x ² = 3.55, M _y ² = 3.89 at the maximum output power.     

914 nm LD end-pumped 31.8 W high beam quality E-O Q-switched Nd:YVO4 laser without intracavity polarizer

We report a 914 nm LD end-pumped high power, high beam quality (M _x ² = 1.378, M _y ² = 1.287) electro-optical Q-switched Nd:YVO₄ laser with TEM₀₀-mode output. At the absorbed pump power of 67.6 W, a 31.8 W 1064 nm Q-switched laser with 43 ns pulse duration was achieved at 100 kHz repetition rate, corresponding to an optical-to-optical efficiency of 47%. The maximum pulse energy and shortest pulse width were 1.67 mJ and 18.5 ns at 10 kHz, and the calculated peak power was 90.3 kW. To the best of our knowledge, this is the highest Q-switched output power ever obtained for a Nd:YVO₄ oscillator pumped at 914 nm.     

High-power passively Q-switched Nd:YVO<Subscript>4</Subscript> UV laser at 355 nm

We report on an efficient high-power passively Q-switched UV laser at 355 nm. We take into account the second threshold criterion and the thermal-lensing effect to design and realize a compact reliable passively Q-switched Nd:YVO₄ laser with Cr⁴⁺:YAG as a saturable absorber. At an incident pump power of 16.3 W, the average output power at 1064 nm reaches 6.2 W with a pulse width of 7 ns and a pulse repetition rate of 56 kHz. Employing the developed passively Q-switched laser to perform the extra-cavity harmonic generations, the maximum average output powers at 532 nm and 355 nm are up to 2.2 W and 1.62 W, respectively.     

Simultaneous Generation of Multi-Wavelength Laser from Nd:YAG Crystals in a Cruciform Cavity

A cruciform cavity is presented for multi-wavelength laser generation. On the basis of considering the optimal power ratio and good spatial overlap of the two fundamental beams, the maximum output power of 589 nm laser reaches 3.5 W when the pumping power of Nd：YAG A and Nd：YAG B are 311.5 W and 261.8 W, respectively. At the same time, the other wavelength lasers are also obtained with the output power distribution of 2.5 W at 66Onto, 15 W at 532nm, lOOmW at 1319nm and 240mW at 1064nm. The corresponding beam quality factors are M^2 x = 4.93, M^2 y = 5.01 at 589nm, M^2z = 4.51, M^2 y = 4.85 at 660hm, and M^2 x = 4.12, M^2 y = 3.96 at 532nm, respectively. The instabilities of the three visible lights are measured, which are also less than 2% within three hours.     

KGW 晶体外腔式高功率579 nm喇曼黄光激光器

报道了579 nm高功率KGd(WO₄)₂喇曼晶体外腔式喇曼黄光激光器的输出特性.基于808 nm脉冲激光二极管侧面泵浦Nd:YAG陶瓷、腔内BBO电光晶体同步延迟调Q和Ⅰ类临界相位匹配的LBO晶体腔外倍频方案,并通过外腔式KGW晶体Ng轴二阶斯托克斯喇曼频移,获得了579.54 nm黄光激光输出.当脉冲信号重复频率为1 kHz、532 nm泵浦光最高平均功率为5.02 W、脉冲宽度为10.1 ns时,获得了最高平均功率2.58 W、脉冲宽度7.4 ns、峰值功率348.6 kW的579.54 nm二阶斯托克斯喇曼黄光激光输出;532 nm至579.54 nm的光-光转化效率为51.4%、斜率效率为54.8%,光束质量因子M_x-579.54²=5.829、M_y-579.54²=6.336,输出功率不稳定性小于±2.35%.实验表明:外腔式喇曼结构能够高效地获得喇曼黄光,具有很高的光-光转化效率及良好的功率稳定性,并通过脉冲LD结合同步延迟电光调Q可获得高重复频率、高平均功率、窄脉冲宽度和高峰值功率的黄光激光输出.     

Highly efficient third-harmonic generation with electro-optically Q-switched diode-end-pumped Nd:YVO4 slab laser

We have achieved efficient third-harmonic generation (THG) with an electro-optically Q-switched diode-end-pumped slab laser by cascading second-harmonic and sum-frequency generation in a lithium triborate (LBO) crystal. The high conversion efficiency, short pulse length and high pulse energy is the characteristic of the output 355 nm light. An average power of 11.1 W at a repetition rate of 10 kHz was achieved. The pulse energy is 1.1 mJ and the pulse length is 5 ns. The peak power of pulse is 0.22 MW. The conversion efficiency from 1064 nm to 355 nm reached 44.4% which is to our knowledge the highest conversion efficiency. Furthermore, the 355 nm light is near TEM₀₀ mode. The beam quality is M² < 1.5. In this paper, the experimental setup, results and the factors which can affect the conversion efficiency are discussed.     

Compact diode-side-pumped Nd:YVO<Subscript>4</Subscript> laser in grazing-incidence configuration

The analysis of compact CW diode-side-pumped grazing-incidence-geometry Nd:YVO₄ laser designs is presented. An output power of 5 W (λ=1064 nm) was produced at 17 W of diode pump (conversion efficiency of 30%) in single transverse TEM₀₀ mode operation at high laser beam quality (M_x ²≈1.05 and M_y ²≈1.01). The resonator geometry was analyzed by applying generalized 4×4 matrix modeling of the spatial mode size, including the impact on the laser operation of cavity astigmatism and a thermal lens in the laser slab. The simplicity and compactness of the laser cavities allow their use for technological applications. Received: 31 July 2002 / Published online: 22 January 2003 RID="*" ID="*"Corresponding author. Fax: +44-20/7594-7744, E-mail: m.damzen@ic.ac.uk     

Generation of CdS clusters using laser ablation: the role of wavelength and fluence

The formation of cationic clusters in the laser ablation of CdS targets has been investigated as a function of wavelength and fluence by mass spectrometric analysis of the plume. Ablation was carried out at the laser wavelengths of 1064, 532, 355, and 266 nm in order to scan the interaction regimes below and above the energy band gap of the material. In all cases, the mass spectra showed stoichiometric Cd _n S _n ⁺ and nonstoichiometric Cd _n S _n−1⁺, Cd _n S _n+1⁺, and Cd _n S _n+2⁺ clusters up to 4900 amu. Cluster size distributions were well represented by a log-normal function, although larger relative abundance for clusters with n=13, 16, 19, 34 was observed (magic numbers). The laser threshold fluence for cluster observation was strongly dependent on wavelength, ranging from around 16 mJ/cm² at 266 nm to more than 300 mJ/cm² at 532 and 1064 nm. According to the behavior of the detected species as a function of fluence, two distinct families were identified: the “light” family containing S₂⁺ and Cd⁺ and the “heavy” clusterized family grouping Cd₂⁺ and Cd _n S _m ⁺. In terms of fluence, it has been determined that the best ratio for clusterization is achieved close to the threshold of appearance of clusters at all wavelengths. At 1064, 532, and 355 nm, the production of “heavy” cations as a function of fluence showed a maximum, indicating the participation of competitive effects, whereas saturation is observed at 266 nm. In terms of relative production, the contribution of the “heavy” family to the total cation signal was significantly lower for 266 nm than for the longer wavelengths. Irradiation at 355 nm in the fluence region of 200 mJ/cm² has been identified as the optimum for the generation of large clusters in CdS.     

Near IR laser light visualizators using nonlinear GaSe and other layered crystallites

Two methods of preparation of the devices for visualization of pulsed and continuous near-IR (near infrared) are described and the results of conversion of pulsed and continuous IR (800–1360 nm) laser radiation into the visible range of spectra (400–680 nm) by using a transparent substrate covered with the particles (including nanoparticles) of effective nonlinear materials of GaSe _x S_{1 − x} (0.2 ≤ x ≤ 0.8) are presented. Converted light can be detected in transmission or reflection geometry as a visible spot corresponding to the real size of the incident laser beam. Developed device structures can be used for checking if the laser is working or not, for optical adjustment, for visualization of distribution of laser radiation over the cross of the beam and for investigation of the content of the laser radiation. Low energy (power density) limit for visualization of the IR laser pulses with 2–3 ps duration for these device structures are: between 4.6–2.1 μJ (3 × 10⁻⁴−1 × 10⁻⁴ W/cm²) at 1200 nm; between 8.4–2.6 μJ (4.7 × 10⁻⁴−1.5 × 10⁻⁴ W/cm²) at 1300 nm; between 14.4–8.1 μJ (8.2 × 10⁻⁴–4.6 × 10⁻⁴ W/cm²) at 1360 nm. Threshold damage density is more than 10 MW/cm² at λ = 1060 nm, pulse duration τ = 35 ps. The results are compared with commercially existing laser light visualizators.     

High-repetition-rate high-beam-quality 43 W ultraviolet laser with extra-cavity third harmonic generation

High-power, high-repetition-rate extra-cavity third harmonic generation of 355 nm with high beam quality has been developed. The acoustic-optical Q-switched Nd:YVO₄ MOPA laser including 2- and 4-stage amplifiers was used as the IR source. With the extra-cavity frequency conversion of LBO crystals, 30.2 W TEM₀₀-mode 355 nm UV laser was obtained with a 2-stage amplifier MOPA laser, and the optical-to-optical (1064 nm to 355 nm) conversion efficiency was up to 30%. Enhanced 43 W TEM₀₀ UV laser at 60 kHz was achieved with a 4-stage amplifier MOPA IR laser, and pulse duration was 10.7 ns corresponding to the peak power as high as 67 kW, with single pulse energy of 0.72 mJ. The optical–optical efficiencies from IR and diodes to UV were 28% and 10% respectively.     

High-power diode-pumped Tm:YLF slab laser

A 2% Tm³⁺-doped LiYF₄(Tm:YLF) slab is double-end-pumped by two laser diode stacks. The pumped volume has a rectangular cross section. The Tm:YLF laser produced 148 W of continuos-wave output at 1912 nm in a beam with M _x ²≈199 and M _y ²≈1.7 for 554 W of incident pump power. The slope efficiency with respect to the incident pump power was 32.6%, and the optical-to-optical efficiency was 26.7%.     

Single-frequency operation of a laser diode side-pumped Q-switched Tm:YAG laser using seeding injection technique

A laser diode (LD) side-pumped 2 μm single-frequency Q-switched Tm:YAG laser was demonstrated. The laser was injection seeded by a CW single frequency Tm:YAG laser with a twisted-mode cavity. The maximum single-frequency pulse energy was 16.3 mJ, with a pulse width of 570 ns and a pulse repetition rate of 10 Hz. The linewidth of the 2 μm single-frequency Q-switched laser was 0.68 MHz, measured by using the optical heterodyne technique. The M ² of the laser beam was measured to be 1.09 and 1.03 for x direction and y direction, respectively.     

High-energy single longitudinal mode 1 ns all-solid-state 266 nm lasers

A single longitudinal mode (SLM) short pulse high energy all-solid-state ultraviolet laser is demonstrated in this paper. Through the use of a master oscillator power amplifier (MOPA) architecture, we have been able to provide high-energy outputs with the combination of short pulses, good beam quality and SLM typically produced by a 1064 nm Nd:YAG laser. The passively Q-switched SLM Nd:YAG laser in a twisted-mode cavity is operated as the seed source. After the seed is amplified by a double-pass pre-amplifier and a single-pass main-amplifier, the 100 μJ, 1064 nm, ∼1 ns seeding pulse was amplified up to 400 mJ energy in the total pulse train. Using a KTP crystal for second-harmonic generation and a CLBO for fourth-harmonic generation, we successfully obtained a short pulse, high energy ultraviolet laser of 266 nm, with the output energy of 108 mJ, pulse width 1 ns and M²<5. PACS 42.65.Ky; 42.72.Bj; 42.60.Da     

High power composite Nd:YAG/YAG zigzag dual-slab laser oscillator

We report a high power zigzag slab laser oscillator employing two composite Nd:YAG/YAG slab in the cavity. The CW laser output with the power of 401 W was achieved from the oscillator with the optical-optical efficiency of 32.6%. The beam quality is estimated as M _x ² ≈ 10, M _y ² ∼ 50 in the slab width and thickness direction, respectively.     

All-solid-state Nd:Gd<Subscript>0.18</Subscript>Y<Subscript>0.82</Subscript>VO<Subscript>4</Subscript>-LBO green laser at 532 nm

We report a continuous-wave (CW) coherent green radiation at 532 nm by intracavity frequency doubling generation of 1064 nm Nd:Gd_0.18Y_0.82VO₄ laser. With incident pump power of 18.2 W, output power of 1.08 W at 532 nm has been obtained using a 5 mm-long KTP crystal. The optical conversion efficiency was up to 5.9%. At the output power level of 1.08 W, the output stability is better than 5%. The beam quality M² values were equal to 1.26 and 1.12 in X and Y directions, respectively.     

Nd:GdVO<Subscript>4</Subscript> slab laser with line-shaped end-pumping profile operating at 912 nm

A continuous-wave laser with line-shaped end-pumping profile operating at 912 nm is presented. The maximum output power of 7.82 W is obtained, with a slop efficiency of 24.7% and beam quality factors of M _x ² ∼ 20, M _y ² ∼ 1.3. To the best of our knowledge, this is the first laser diode bar directly pumped Nd:GdVO₄ slab laser based on the quasi-three-level ⁴ F _3/2 → ⁴ F _9/2 transition in neodymium. Furthermore, we disclose that the experimental setups can be improved by inserting a plano-concave cylindrical lens in the cavity to form a new quasi-concentric resonator to improve die mode-matching in x-direction.