Generation of modulation-free pulses using an active fabry-perot

A high gain active medium, Nd:YAG, has been shown to act as an efficient intracavity etalon for the generation of modulation-free Q-switched pulses. The “active etalon” thus formed offers a distinct advantage of finesse variation by varying the active medium gain. The analysis and experimental verification is presented.     

Experimental study of high-power pulse side-pumped Nd:YAG laser

The paper reports on the characterization of a compact and simple side-pumped 0.538 J×100 Hz pulse Nd:YAG laser. A side-pumping configuration with 100 laser diode bars is used in the laser head. We also experimentally studied the laser performance of the diode-pumped Nd:YAG laser head in the free running and Q-switched operation under different repetition rates.     

Simple numerical control loop for stabilizing Nd:YAG and Nd:YLF single-mode oscillators

In order to get reliable and synchronisable smooth nanosecond range pulses, a high stability singlemode actively Q-switched laser oscillator has been developed which works with Nd:YAG or Nd:YLF. An electronic loop is used for longitudinal mode control. It is based on dual-mode beating detection and the design is mainly numerical. The system produces 10 pps jitter free pulses with ±2% amplitude stability and 100% singlemode spectral limitation. The method is equally suitable for producing repetitive dual-mode modulated pulses.     

Experimental study on passively Q-switched mode-locking diode-pumped Nd:KGW laser with Cr4+:YAG

A diode-pumped passively Q-switched and mode-locked Nd:KGW/Cr⁴⁺:YAG laser with different output couples is realized in a V-type folded cavity. About 85% modulation depth for the mode-locked pulses has been obtained. The repetition rate of the mode-locked pulses inside the Q-switched envelope was about 798 MHz.     

39.5% conversion of low-power Q-switched Nd:YAG laser radiation to 266 nm by use of a resonant ring cavity

A simple ring cavity consisting of mirrors reflecting at the second harmonic is used to generate the fourth harmonic of low-power Q-switched Nd:YAG laser pulses. A large beam waist of 1 mm minimized the effects of double refraction and thermal loading of the nonlinear crystals. By simulating the low-power pulses with a small portion of the output from a 30-Hz flash-lamp-pumped Q-switched Nd:YAG laser, we obtained IR-UV energy conversion as great as 39.5% to yield 84-mW average power at 266 nm from 213 mW of single-mode 1064-nm radiation.     

A study of the self-injected laser for subnanosecond pulse generation

We present a detailed analysis of the self-injected Nd:YAG laser which is capable of generating subnanosecond duration pulses with peak powers as high as 200 MW. The model predicts that pulses with durations much shorter than the electrical rise time of the electrooptical switch driver can be obtained. Application of this technique to a conventionally Q-switched Nd:YAG laser allowed us to obtain 550 ps pulses with 120 mJ in a very stable and reliable way.     

High-peak power,passively Q-switched,composite, all-poly-crystalline ceramics Nd:YAG/Cr<Superscript>4+</Superscript>:YAG laser and generation of 532-nm green light

Output performances of passively Q-switched, composite Nd:YAG/Cr⁴⁺:YAG lasers that consisted of bonded, all-poly-crystalline ceramics Nd:YAG and Cr⁴⁺:YAG are reported. Laser pulses at 1.06 μm with 2.5-mJ energy and 1.9-MW peak power are obtained from a 1.1-at % Nd:YAG/Cr⁴⁺:YAG ceramics that was quasi-continuous-wave (quasi-CW) pumped with a diode laser. Single-pass frequency doubling with LiB₃O₅ (LBO) nonlinear crystal at room temperature yielded green laser pulses at 532 nm of 0.36-mJ energy and 0.3-MW peak power, with a conversion efficiency of 0.27.     

A simple laser pulse tailoring/synchronization system for laser plasma interaction experiments

A system is described for accurately synchronizing pulses from single longitudinal mode Q-switched Nd: YAG oscillator (QSO) with those from a passively mode-locked Nd: YAG oscillator (MLO). Single mode operation is achieved by applying external negative feedback stabilization to the QSO to bring it into quasi-CW operation before Q-switching is triggered by the pulse from the MLO. The relative jitter between the peaks of the two pulses did not exceed 1 ns.     

Numerical Modelling of QCW-Pumped Passively Q-Switched Nd：YAG Lasers with Cr^4＋：yAG as Saturable Absorber

Passively Q-switched quasi-continuous-wave （QCW） diode-pumped Nd：YAG laser with Cr^4＋ ：YAG as saturable absorber is numerically investigated by solving the coupled rate equations. The threshold pump rate for passively Q-switched QCW-pumped laser is derived. The effects of the pump rate and pump-pulse duration on the laser operation characteristics are studied theoretically. The pump power range can be estimated according to the number of output pulses. The numerical simulation results are in good agreement with the experimental results.     

Tunable sub-100 femtosecond dye-laser pulses generated with a nanosecond pulsed pumping

Subpicosecond pulses at a fixed wavelength produced with a low-Q cavity dye laser pumped by a single, nanosecond laser (Q-switched Nd:YAG) are converted into tunable high-power sub-100 femtosecond pulses by generation, spectral selection, amplification and compression of a supercontinuum. The tunable, chirped, high-energy pulses obtained are compressed with a prism pair. Energies up to 50 J in sub-100 fs pulses were obtained in the 540 to 650 nm range using 40 mJ of the Nd: YAG-laser pumping pulses at 532 nm. The whole sub-100 fs system including the low-Q dye laser uses only one Nd:YAG laser as a pump source.     

LD-pumped single-frequency passively Q-switched green laser

A LD-pumped single-frequency passively Q-switched Nd: YVO₄/KTP/Cr:YAG green laser is presented. Cr:YAG plays the double role of a passive Q-switch and a Brewster plate. With 900 mW incident pump laser, single-frequency passively Q-switched green laser with average power of 86 mW, pulse width of 14.7 ns, repetition rate of 140.8 kHz and peak power of 41.6 W is obtained. Measurement shows that the pulse amplitude and period between pulses are stable within ±1.5%.     

Intracavity optical parametric oscillator pumped by passively Q-switched Nd:YLF laser

We report on a passively Q-switched end pumped Nd:YLF laser including a noncritically phase-matched KTP singly resonant intracavity optical parametric oscillator (IOPO-KTP). For the Q-switching operation we have used Cr:YAG saturable absorber. The optimized passively Q-switched Nd:YLF laser without IOPO generated linearly polarized pulses of 11.5 ns and 1.07 mJ at 1047 nm. The conversion efficiency of the optimized Q-switched pulse energy at 1047 nm to 1547 nm of a signal approached about 47%. For optimizing both Nd:YLF laser and IOPO we have numerically solved a theoretical model. We have achieved 1.6-ns duration pulses at 1547 nm with energy of 0.5 mJ and peak power of above 300 kW. The beam quality was excellent (M² ≈1).     

Diode end-pumped passively Q-switched Nd:YAG ceramic laser with Cr4+:YAG saturable absorber

We report on a diode end-pumped passively Q-switched Nd:YAG ceramic laser. By using a Cr⁴⁺:YAG single crystal with an 80% initial transmission as the saturable absorber, stable Q-switched pulses with a 126-μJ pulse energy, a 12-ns pulse width, and an 8.4-kHz pulse repetition rate have been obtained. The Q-switching performance of the laser under different saturable absorption strengths and output couplings was experimentally investigated.     

Diode pumped Nd:YAG laser repetitively Q-switched with Cr4+:YAG

Based on the rate equations of passively Q-switched solid state lasers, the performance of laser at a fixed pump power can be optimized through the proper choice of output coupler and the low-intensity transmission of saturable absorber. A simple expression for optimizing these two parameters is derived in this paper. We also demonstrate the performance of an efficient diode-pumpe Cr⁴⁺:YAG passively Q-switched Nd:YAG laser to generate a high-repetition-ate, high-peak power 1064 nm laser pulses, which providing pulses peak power > 10 kW with high repetition rate up to 150 kHz, and the pulse width as short as 6.8 ns.     

Diode-end-pumped Nd:YAGLaser with Cr4+:YAG as Passive Q-switch

A diode-end-pumped Nd:YAG laser is passively Q-switched by using Cr4+:YAG as saturable absorber. When CW pumped with a laser diode which the maximum power is 550 mW, the laser produces pulses of 24 ns duration at 1064 nm, with an energy of 26 μJ.     

外延单片式激光二极管抽运被动调Q微激光器

基于液相外延工艺,实现了一种结构新颖的单片式被动调Q微片激光器。采用了在激光介质Nd3 ∶YAG表面直接液相外延生长一层具有饱和吸收特性的Cr4 ∶YAG膜的微谐振腔的结构,由于是同质外延生长过程,能够确保饱和吸收体与增益介质间(Nd3 ∶YAG/Cr4 ∶YAG)良好的界面特性。采用光纤耦合激光二极管,在激光二极管输出为1W的抽运条件下,实现了峰值功率近千瓦、稳定重复频率在4kHz以上、脉宽1.8ns、TEM00单横模式、波长1.064μm的调Q脉冲序列输出。在对新型单片式微激光器的性能报道的基础上,阐述了外延单片式结构及其相应工艺的潜在优势。     

激光二极管列阵侧面泵浦Nd：YLF激光器

报道准连续６０Ｗ激光二极管列阵侧面泵浦Ｎｄ：ＹＬＦ固体激光器的研究结果，当器件的动转重复频率为３０Ｈｚ时，得到４．４ｍＪ的１．０４７μｍ激光输出，光－光转换效率达到１８．３％，斜率效率达２４．４％。声光和电光调Ｑ，得到能量为２．２ｍＪ，脉宽分别为５０ｎｓ和３０ｎｓ的脉冲输出。     

The potential use of plume imaging for real-time monitoring of laser ablation cleaning of stonework

In this work, the potential of plume imaging was investigated as a real-time monitoring technique for the control of the laser cleaning process in cultural heritage objects with emphasis on encrusted stonework. Optical pulses generated by Nd:YAG laser were used to remove a high absorbing layer of crust from the surface of a lower absorbing marble substrate. Two regimes of operation have been employed for laser cleaning test, Q-switched ns mode, and short free running μs mode. Laser induced breakdown spectroscopy (LIBS) was also employed to study the stratigraphy of the cleaned surfaces, and thus to confirm the validity of the suggested monitoring technique. The tests proved the prospective of introducing plume imaging techniques as a straightforward and inexpensive tool for the real-time monitoring of laser ablation and the determination of the critical point for a safe surface cleaning intervention.     

正反馈选模和调Q技术

把一个由GaAs光电导开关和激光腔中的普克尔盒组成的正反馈回路,用于YAG激光器中,选单纵模和调Q,获得了稳定可靠的单纵模调Q脉冲.     

Synchronization of a mode-locked Nd:YAG — Argon ion laser system

A Q-switched active-passive Nd : YAG laser and a c.w. argon ion laser were simultaneously mode-locked using a common R.F. oscillator. Jitter between the output pulses of the two lasers was measured at 18 ps (RMS) and was highly dependent on the modulation depth of the YAG mode-locker. Intensity fluctuations of the argon laser led to significant phase shift between the laser output pulses.