Optical spectroscopy of Er:YSGG laser crystal

Er:YSGG single crystals with good optical quality were grown by Czochralski method. X-ray diffraction (XRD) measurements show that the crystal lattice parameters of the 30 at.% Er³⁺-doped YSGG crystal were a=b=c=12.4640±0.0065 Å, α=β=γ=90°. The doping concentration of Er³⁺ in YSGG was calculated. The absorption spectrum and photoluminescence spectra of Er:YSGG crystal were studied at room temperature. Based on Judd-Ofelt (J-O) theory, the J-O intensity parameters Ω_t (t=2, 4, 6), the experimental and theoretical oscillator strengths were calculated using the absorption spectrum. The intensity parameters Ω_t (t=2,4,6) obtained to be Ω₂=0.23×10⁻²⁰ cm², Ω₄=0.86×10⁻²⁰ cm², Ω₆=0.37×10⁻²⁰ cm², respectively. With these intensity parameters, the line strengths, oscillator strengths, transition probabilities, fluorescence branching ratios and radiation lifetimes were calculated. The photoluminescence spectra and excitation spectrum of Er:YSGG were measured and studied.     

Efficient passively Q-switched operation of a diode-pumped Nd:GGG laser with a Cr:YAG saturable absorber

The continuous-wave (cw) and passive Q-switching operation of a diode-end-pumped gadolinium gallium garnet doped with neodymium (Nd:GGG) laser at 1062 nm was realized. A maximum cw output power of 6.9 W was obtained. The corresponding optical conversion efficiency was 50.9%, and the slope efficiency was determined to be 51.4%. By using Cr⁴⁺:YAG crystals as saturable absorbers, Q-switching pulse with average output power of 1.28 W, pulse width of 4 ns and repetition rate of 6.2 kHz were obtained. The single-pulse energy and peak power were estimated to be 206 μJ and 51.6 kW, respectively. The conversion efficiency of the output power from cw to Q-switching operation was as high as 84.7%.     

Efficient diode-pumped passively Q-switched laser with Nd:YAG/Cr:YAG composite crystal

Diffusion bonded Nd:YAG/Cr:YAG composite laser crystal has been employed to perform a compact diode-pumped passively Q-switched laser. At the incident pump power of 3.3 W and pulse repetition rate of 16.3 kHz, the maximum average output of 592 mW has been obtained, corresponding to an optical-to-optical conversion efficiency of 18%. Stable passively Q-switched operation with peak power of 6.5 kW and pulse duration of 6 ns was also achieved. It has been experimentally revealed that Nd:host/Cr:YAG composite structure is a promising material for compact cost-effective Q-switched laser sources with high-peak power and short pulse duration. In addition, thermal lens effect (TLE) in the active medium and its impact on the Q-switched laser performance have been analyzed.     

Efficient mechanically Q-switched diode side pumped Nd:YAG laser using a rotating prism and mirror combination

In this paper the construction of a mechanically Q-switched diode side pumped Nd:YAG laser system is described. It consists of a 50 cm long plane-plane resonator Q-switched with a combination of a rotating prism and a mirror. With an optical to optical efficiency of 25% Q-switched pulses (@1064) of 48 mJ and 8 ns are obtained at a rep-rate of 30 Hz with an output in near TEMoo mode. At a peak power of 6 MW the M ² value is found to be 1.92. The laser is frequency doubled and then tested on a 50 ??m thick tantalum foil which results in circular holes of diameter 13 ??m in it.     

Cr3+,Yb3+,Er3+共掺磷酸盐铒玻璃转镜调Q激光性质研究

研究了Cr3+,Yb3+,Er3+共掺磷酸盐铒玻璃转镜调Q激光性质.三种Er2O3掺杂浓度的激光实验结果表明,在Er2O3名义掺杂浓度为0.5wt%时,玻璃的综合激光性质最好,重复频率为0.1Hz时,它的激光阈值功率为14.5mJ,最大输出能量为9.6mJ,斜率效率为0.55%.在同种实验条件下,比较了Cr14和Kigre公司生产的QE-7S激光性质参数,实验表明,前者激光阈值功率稍低,而后者的斜率效率和最大输出功率略高.     

High-energy Q-switched operation of a fiber-laser-pumped Er:YAG laser

A high-energy Q-switched Er:YAG laser in-band pumped by an Er,Yb co-doped fiber laser is reported. A simple two-mirror multi-mode resonator incorporating an electro-optic Q-switch and a multi-Brewster-plate polarizer was employed, together with a simple compensation scheme to reduce the depolarization loss due to thermally induced stress birefringence in the Er:YAG crystal at high pump powers. The laser yielded Q-switched pulses at 1617 nm with 30.5-mJ pulse energy and <20-ns pulse duration (FWHM) at 20-Hz repetition rate, corresponding to a peak power of >1.5 MW for 55 W of pump power at 1532 nm. The prospects for further improvement in Q-switched performance are discussed.     

Changes in dental enamel oven heated or irradiated with Er,Cr:YSGG laser. Analysis by FTIR

This study evaluated the change that occurs in dental enamel under action of oven heating or Er,Cr:YSGG laser irradiation aiming to obtain a structure more resistant to demineralization. Enamel powder was obtained from bovine teeth. Samples were subjected to oven heating at temperatures of 200, 400, 600, 800, and 1000°C or during laser irradiation with energy densities of 7.53, 10.95, and 13.74 J/cm². The infrared thermography was used to measure the surface temperature generated in the solid samples of enamel during lasers irradiation. The samples were analyzed by Fourier transform infrared spectroscopy (FTIR), which shows changes on enamel oven heated or laser irradiated, due to treatments, related to carbonates, adsorbed water and hydroxyl content. These compositional effects were more evident in lased samples. These changes may alter the material properties such as its solubility, and decrese of demineralization that is important for caries prevention.     

Excellent stability of laser passively Q-switched with a retroreflecting corner cube prism

A miniature Cr⁴⁺:YAG Q-switched, repetitive operation, conductive cooling Nd:YAG laser with a retroreflecting corner cube prism is demonstrated. The corner cube prism which is insensitive to misalignment in any direction makes it useful for the laser to adapt to the violent change of ambient temperature and also makes the laser cavity insensitive to the variation of thermal lens of the crystal. The laser has excellent stability of the average output pulse energy and the threshold voltage under different ambient temperature of −40, 25, and 55°C.     

Q-switched Ti:Er:LiNbO3 waveguide laser

Q-switched operation of a Ti:Er:LiNbO3 waveguide laser has been achieved with up to 2.4 W pulse peak power (0.18J) at 2kHz repetition frequency with an intracavity Mach–Zehnder-type amplitude modulator. A theoretical model has been developed to describe the laser operation. Good agreement between numerical and experimental results has been achieved. Significant potential for improvement is predicted.     

Efficient diode-end-pumped dual-wavelength Nd, Gd:YSGG laser

We demonstrate a dual-wavelength laser based on a new laser material-Nd, Gd:YSGG, or Nd:GYSGG for short-for the first time to our knowledge. Besides its attractive properties such as antiradiation, high segregation coefficient, etc., this kind of laser crystal also shows excellent laser performance. For continuous-wave operation, the maximum output power is 10.1 W with the absorbed power of 18.45 W at 808 nm, corresponding to the slope efficiency of nearly 60%. The maximum single pulse energy and peak power reach 277 μJ and 4.6 kW (60 ns) when the absorbed pump power is 11.4 W for acousto-optic Q-switched operation.     

Determination of ablation threshold of dental hard tissues irradiated with Er:YAG and Er,Cr:YSGG lasers

We evaluate the ablation thresholds of Er:YAG and Er,Cr:YSGG laser for enamel and dentin.A total of 140 dental slices is evenly divided into two groups:the dentin group and the enamel group.Dental tissues are irradiated with either an Er:YAG laser or an Er,Cr:YSGG laser with pulse widths in the order of 100 μs.The laser fluence is increased gradually until the ablation crater is formed.The laser ablation threshold is calculated using probit analysis.The ablation thresholds of the Er:YAG laser for dentin and enamel range from 2.88 to 3.36 J/cm2 and from 2.94 to 3.8 J/cm2,respectively,and the ablation thresholds of the Er,Cr:YSGG laser for dentin and enamel range from 2.92 to 4.2 J/cm2 and from 4.93 to 5.66 J/cm2,respectively.     

Tunable electrooptically Q-switched RF excited CO2 waveguide laser with two channels

A tunable electrooptically Q-switched RF excited waveguide CO₂ laser with two channels is presented. Q-switched pulses have been obtained from one of the channels. The peak power is 300 W and the pulse width is 140 ns. CW laser output has been obtained from the other channel, which can been tuned by a PZT. The short-term heterodyne stability can be up to 10⁻⁹.     

QCW diode-pumped 654 W AO Q-switched Nd:YAG rod oscillator-amplifier laser

A diode laser-pumped acoustic-optic Q-switched Nd:YAG master-oscillator power amplifier laser is presented. The laser is quasi continuously pumped at 1.1 kHz with a pulse width of 172 μs, and the ultrasonic frequency of the AO Q-switcher is set at a higher value (53 kHz). The master oscillator is designed as a thermally near-unstable-resonator, which presents an average output power of 48 W with a beam quality value of M² = 1.41 and a Q-switching pulse duration of 121 ns. The maximum average power of the MOPA system is 654 W, and the beam quality is M² = 6.     

Efficient Cr:ZnSe laser with a volume Bragg grating

An efficient and narrow linewidth Cr:ZnSe laser pumped by Tm,Ho:GdVO₄ laser with a volume Bragg grating (VBG) is reported. The Cr:ZnSe laser operated at 2580 nm with emitting linewidth (FWHM) about 0.8 nm. Using the volume Bragg grating, 3.57 W of output was achieved under total incident pump power of 13.1 W, corresponding to optical-to-optical conversion efficiency of 27.3%. By use of conventional mirror, 4.11 W of output was achieved the same incident pump power and the optical-to-optical conversion efficiency is 31.4%.     

Efficient passively Q-switched Yb:LuAG microchip laser

An efficient passively Q-switched Yb:LuAG microchip laser with Cr4+:YAG as saturable absorber was demonstrated for the first time to our knowledge. Slope efficiencies of 40% and 28% were measured for the initial transmission of Cr4+:YAG, T(0)=95% and 90%, respectively. Laser pulses with a pulse energy of 19 microJ and a pulse width of 610 ps at the repetition rate of 12.8 kHz were achieved for T(0)=90%; the corresponding peak power of over 31 kW was obtained. The lasers oscillated at two or three longitudinal modes owing to the broad emission spectra of Yb:LuAG and mode selection by Cr4+:YAG thin plate acting as an intracavity etalon.     

Efficient 1645-nm Er:YAG laser

We report a resonantly fiber-laser-pumped Er:YAG laser operating at the eye-safe wavelength of 1645 nm, exhibiting 43% optical efficiency and 54% incident slope efficiency and emitting 7-W average power when repetitively Q switched at 10 kHz. To our knowledge, this is the best performance (conversion efficiency and average power) obtained from a bulk solid-state Q-switched erbium laser. At a 1.1-kHz pulse repetition frequency the laser produces 3.4-mJ pulses with a corresponding peak power of 162 kW. Frequency doubling to produce 822.5-nm, 4.7-kW pulses at 10 kHz was performed to demonstrate the laser's utility.     

Q-switched Er:YAG lasers resonantly pumped by Erbium fiber laser

The study describes efficient, acousto-optic Q-switching of Er:YAG laser at the 1645 nm eye-safe wavelength. For longitudinal pumping at wavelength 1532 nm, linear-polarized 10 W Erbium fiber laser radiation was used. The investigated Er:YAG crystals were 25 and 40 mm long and their Erbium concentration was 0.20 and 0.25%, respectively. For giant pulse generation, a fused silica acousto-optic modulator was inserted inside the Er:YAG laser oscillator. For a maximum incident pump power of 7.95 W, pulse energy up to 4.1 mJ was generated with pulse duration 34 ns at 500-Hz repetition rate; the corresponding peak power was 119 kW.     

Resonantly pumped Q-switched Er:GdVO4 laser

We describe a Q-switched Er:GdVO₄ laser resonantly pumped by a MgO-doped periodically poled LiNbO₃ optical parametric oscillator （MgO: PPLN OPO） at 1536 nm. In continuous-wave lasing, the maximum output power is 1.14 W with an incident pump power of 4.7 W and a slope efficiency of 27%. In Q-switched operation, 1.1 mJ of output pulse energy is achieved at 200 Hz. The upper-state lifetime at different pulse repetition frequencies is also calculated.     

Tunable 7 12-microm optical parametric oscillator using a Cr,Er:YSGG laser to pump CdSe and ZnGeP(2) crystals

A CdSe optical parametric oscillator (OPO) pumped by a 2.79-mum , Cr, Er:YSGG laser yielded a 59% signal-plus-idler slope efficiency (eta), a total idler output of 1.2-2.4mJ between 8.5 and 12.3 mum , and an idler beam that was 2.2-2.5 times the diffraction limit. A ZnGeP(2) OPO operated with a lower threshold, eta = 29% , and a forward idler output of 0.7-2.4 mJ from 6.9 to 9.9 microm . The signal and idler bandwidths were typically 4 cm(-1) for each OPO.