A CW seeded femtosecond optical parametric amplifier

1 Introduction Optical parametric amplification (OPA) based on femtosecond Ti:sapphire regen-erative amplifiers has been widely adopted in wavelength extension of ultrashort opticalpulses[1]. While BBO-based femtosecond optical parametric amplifiers have alreadycommercialized, the tuning range of such an 800 nm-pumped OPA is typically between1.15 μm and 2.6 μm due to the limited transparent range of BBO. From application’spoint of view, ultrashort pulses near 1 μm and between 3 and 4 …     

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-efficiency mid-infrared laser from synchronous optical parametric oscillation and amplification based on a single MgO:PPLN crystal

This paper presents a specially designed optical parametric oscillator (OPO) which achieved high-efficiency mid-infrared laser of 2.83 μm. The cascaded nonlinear interactions of OPO and optical parametric amplifier (OPA) were simultaneously realized in a single MgO:PPLN crystal. The signal oscillation of 1.70 μm was used to pump a secondary parametric process that resulted in amplification of the idler laser of 2.83 μm. When the MgO:PPLN crystal with a grating period of 31.2 μm was pumped by a 1.064 μm laser and operated at 148°C, the quasi-phase-matching of both OPO and OPA could be simultaneously achieved. Average output power of 7.68 W at 2.83 μm was obtained for 25 W of pump at 7 kHz. The power conversion efficiency of 2.83 μm laser was 30.7%, which was evidently higher than common OPOs.     

Pulsed optical parametric oscillators with intracavity optical parametric amplification: a critical study

It is known that the idler conversion efficiency of optical parametric oscillators (OPOs) can be increased by adding a second nonlinear crystal in the cavity. This crystal is pumped by the signal and acts as an optical parametric amplifier (OPA) for the idler. However, this technique unavoidably increases the oscillation threshold because of additional losses and increased build-up time due to cavity lengthening. In this paper, we investigate both theoretically and experimentally the benefits and drawbacks of this so called OPO–OPA configuration versus the singly resonant OPO (SRO) configuration. Calculations are found to be in agreement with an experimental study of a SRO and an OPO–OPA operating near 3.4 μm both pumped by a 90-mJ 27-ns Nd:YAG laser. Our study reveals that the OPO–OPA needs to be driven at least two times above threshold to produce more idler energy than the SRO. In addition, near 3 μm the OPO–OPA is particularly efficient given that the difference frequency wave generated in the second crystal is also output coupled. PACS 42.65.Yj; 42.65.Sf     

Amplification assisted optical parametric oscillator in the mid-infrared region

We demonstrate a high efficiency mid-infrared laser source based on optical parametric oscillator (OPO) assisted by an intracavity optical parametric amplification (OPA). The OPA-assisted-OPO scheme was realized in one piece of commensurable dual-periodic superlattice in which the signal light generated from the OPO process serves as the pump light for the OPA process. A maximum output power of 508 mW at 3.92 μm was achieved under a pump power of 2.85 W at 1.064 μm. The pump-to-idler conversion efficiency is 17.8% and the slope efficiency is 23.8%, and the enhancements of them are 58.9% and 67.6%, respectively, comparing with the standard OPO scheme.     

Tri-wavelength laser with Nd:CLTGG crystal

Continuous-wave (CW) and passively Q-switched operations of laser diode-end-pumped Nd:CLTGG laser at 1.06 μm was demonstrated for the first time. The laser spectrum was found to be tri-wavelength, with respective wavelengths of 1058.4, 1060.5, and 1065.5 nm for both CW and passive Q-switching regime. The highest CW output power of 2.6 W was obtained with an optical-optical conversion efficiency of 13.9% and a slope efficiency of 17.1%. In the passive Q-switching regime, the highest output power, shortest pulse width, largest pulse energy and highest peak power were achieved as 242 mW, 45.8 ns, 1.65 μJ and 0.4 kW, respectively. The passively Q-switched tri-wavelength laser should have the potential to be used for terahertz radiation generation.     

Diode-pumped Nd:YGG continuous-wave laser at 1.33 μm

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet (Nd:YGG) crystal continuous wave (CW) laser at 1.33 μm for the first time to our knowledge. At an incident pump power of 18.5 W, as high as 3.09 W of CW output power at 1.33 μm is achieved. The slope efficiency with respect to the incident pump power was 21.3%, and the fluctuation of the output power was better than 2.8% in the given 4 h. The beam quality factor M² is 1.14 and 1.16 for tangential direction and sagittal direction, respectively.     

High power,continuous wave,singly resonant OPO based on MgO:PPLN

A continuous wave (CW), extra-cavity singly resonant optical parametric oscillator (SRO) has been demonstrated. The SRO was based on 5% Magnesium-Oxide doped periodically-poled Lithium Nio-bate (MgO:PPLN) pumped by a Yb fiber laser centered at 1064.7 nm. The SRO was able to generate light with idler wavelengths ranging from 2.9 to 4.1 μm. For a pump power of 15 W, the idler output power varied from 7.54 W at 3.03 μm to 1.04 W at 4.05 μm. The oscillation thresholds were 2.0 W at idler wavelength 3.03 μm and 7.0 W at 4.05 μm.     

Tunable mid-infrared,high-energy femtosecond laser source for glyco-protein structure analysis

We have developed a 6–12 μm mid-infrared (MIR) femtosecond laser source for glyco-protein structure analysis. The MIR femtosecond laser pulses are generated by a differential frequency generation (DFG) configuration with a combination of Ti:sapphire based regeneratively amplified femtosecond laser pulses (780 nm, 160 fs, 1 mJ) and a β-BaB₂O₄ (BBO) based optical parametric amplifier (OPA). The MIR pulse energy exceeds 4.5 μJ, where a glyco-protein molecule has resonant absorption lines due to the vibrational–rotational transitions. The pulse width is estimated to be less than 1 ps according to the cross correlation measurement between the two OPA output pulses. Using the MIR femtosecond laser pulses, we demonstrated photo-dissociation of the sialyl Lewis X (sLeX) proton added ion, which is the first time to the best of our knowledge. PACS 42.65.Re; 42.62.-b; 42.60.-b; 42.65.-k; 87.50     

Efficient continuous wave and Q-switched operation of a dual-end-pumped <Emphasis Type="Italic">c</Emphasis>-cut Tm:YAP laser

An efficient continuous wave (CW) and Q-switched c-cut Tm:YAP laser is reported in this letter. With the dual-end-pumped convex-concave resonator, CW output power up to 13.6 W at 1.99 μm was obtained under a total incident pump power of 50 W. The corresponding slope efficiency was 34.3% and conversion efficiency was 27.2%. The active Q-switched operation of the laser had an average output power of 12.5 W at 10 kHz pulse repetition frequency, with a minimum pulse width of 126 ns. With 6 kHz pulse repetition frequency, the maximum pulse energy of 1.6 mJ was obtained. In addition, using the Tm:YAP laser as a pumping source for gain-switched Cr:ZnSe laser, as much as 4 W output power in the wavelength range of 2.5–2.6 μm was obtained.     

1653 nm光参量放大器及在甲烷遥测方面的应用

基于掺氧化镁的周期性极化铌酸锂（MgO:PPLN）晶体,研究了连续波种子光注入结构的光参量放大器(OPA)。采用重复频率为10 kHz、最大平均输出功率为6 W的1064 nm高频脉冲激光作为抽运源,晶体的极化周期为31.02 m,在119 ℃工作温度下,将连续分布式反馈激光器（DFB）作为种子注入,在1652.3 nm处得到最大平均功率为125 mW的OPA信号光输出,量子转换效率为7.47％。实验通过改变注入种子光波长,实现了信号光nm级范围的调谐输出。信号光通过10 m外甲烷气池,观察到其光谱强度明显下降,初步验证了信号光在甲烷遥测领域的可行性。与用种子光直接检测相比,信号光强度更高,检测距离及灵敏度均有较大优势。     

High-performance,continuous-wave quantum-cascade lasers operating up to 85°C at <Emphasis Type="Italic">λ</Emphasis>∼8.8 μm

High-temperature, high-power, and continuous-wave (CW) operation of quantum-cascade lasers with 35 active/injector stages at λ∼8.85 μm above room temperature is achieved without using a buried heterostructure. At this long wavelength, the use of a wider ridge waveguide in an epilayer-down bonding scheme leads to a superior performance of the laser. For a high-reflectivity-coated 21 μm×3 mm laser, the output power of 237 mW and the threshold current density of 1.44 kA/cm² at 298 K under CW mode are obtained with a maximum wall-plug efficiency of 1.7%. Further improvements were observed by using a 4-mm-long cavity. The device exhibits 294 mW of output power at 298 K and it operates at a high temperature, even up to 358 K (85°C). The full widths at half-maximum of the laser beam in CW operation for the parallel and the perpendicular far-field patterns are 25°and 63°, respectively.     

Fabrication and characterization of 1.55 μm single transverse mode large diameter electrically pumped VECSEL

We report on the design, fabrication, and characterization of InP-based 1.55 μm wavelength large diameter (50 μm) electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs). The hybrid device consists of a half vertical cavity surface emitting laser (1/2-VCSEL) structure assembled with a concave dielectric external mirror. The 1/2-VCSEL is monolithically grown on InP substrate and includes a semiconductor Bragg mirror and a tunnel junction for electrical injection. Buried (BTJ) and ion implanted (ITJ) tunnel junction electrical confinement schemes are compared in terms of their thermal and electrical characteristics. Lower thermal resistance values are measured for BJT, but reduced current crowding effects and uniform current injection are evidenced for ITJ. Using the ITJ technique, we demonstrate Room-Temperature (RT) continuous-wave (CW) single transverse mode laser operation from 50-μm diameter EP-VECSEL devices. We show that the experimental laser optical output versus injected current (L–I) curves are well-reproduced by a simple analytical thermal model, consistent with the thermal resistance measurements performed on the 1/2-VCSEL structure. Our results indicate that thermal heating is the main mechanism limiting the maximum CW output power of 50-μm diameter VECSELs, rather than current injection inhomogeneity.     

High performance Cr4+:YAG Q-switched CW diode pumped Nd:YAG laser

This paper reports the operation of a Cr4+:YAG Q-switched CW diode laser pumped Nd:YAG at 1064nm. The laser performances resulted in 167 μ J, 21ns pulses at 10kHz, and 1.67W power output. When intracavity polarized, stable amplitude (fluctuations <±1%), TEM00, 153 μ J pulses were generated allowing 50% SHG in KTP. This revised version was published online in November 2006 with corrections to the Cover Date.     

All fiber MOPA laser-pumped,continuous-wave,mid-infrared,singly-resonant optical parametric oscillator based on periodically poled MgO-Doped LiNbO<Subscript>3</Subscript>

We report a continuous-wave (CW) mid-infrared singly resonant optical parametric oscillator (SRO) based on periodically poled MgO-doped LiNbO₃ (PPMgLN) pumped by a high power, single frequency fiber laser in master oscillator-power amplifier (MOPA) configuration at 1.064 μm. Using four-mirror ring OPO cavities, at the PPMgLN’s grating period of 30.5 μm and the temperature of 23°C, we achieved the maximum idler output power of 7.2 W at 3.4 μm when the pump power was 52.8 W. The total power-conversion efficiency from the pump to the idler in this experiment is about 13.6%, and corresponds to ∼44% of quantum-limited performance.     

Planar laser-induced fluorescence imaging of carbon monoxide using vibrational (infrared) transitions

We report a new imaging diagnostic suitable for measurements of infrared-active molecules, namely infrared planar laser-induced fluorescence (IR PLIF), in which a tunable infrared source is used to excite vibrational transitions in molecules and vibrational fluorescence is collected by an infrared camera. A nanosecond-pulse Nd:YAG-pumped KTP/KTA OPO/OPA system is used to generate 12 mJ of tunable output near 2.35 μm which excites the 2ν band of carbon monoxide (CO); fluorescence resulting from excited CO is collected at 4.7 μm by using an InSb focal plane array. Quantitative, high-SNR PLIF imaging of gas-phase CO is demonstrated at a 10-Hz acquisition rate with a minimum detection limit of 1350 ppm at 300 K. Received: 30 July 1999 / Published online: 16 September 1999     

A 200 W diode-side-pumped CW 2 μm Tm:YAG laser with water cooling at 8°C

A water-cooled 785 nm diode-side-pumped high-power CW Tm:YAG laser system at 2 μm is reported. 200 W output power is achieved with cooling water running at 8°C. As far as we know, this is the highest output power for a diode-pumped all solid-state 2 μm Tm:YAG laser. The output corresponds to optical-to-optical conversion efficiency of 11.2%, with a slope efficiency of about 22.8%. To make the system structure simple, only deionized water is used as the coolant instead of alcohol- or glycol-water mixture or the liquid nitrogen in the reported high-power Tm rod laser experiments, which were performed at low temperature near the freezing point of water, or even below.     

Continuous wave,singly resonant MgO:PPLN OPO pumped by a Nd:YVO<Subscript>4</Subscript>/YVO<Subscript>4</Subscript> ring laser

A continuous wave (CW), extra-cavity singly resonant optical parametric oscillator (SRO) has been demonstrated. The SRO is based on 5% magnesium-oxide doped periodically-poled lithium niobate (MgO:PPLN) pumped by a CW Nd:YVO₄/YVO₄ ring laser centered at 1064.4 nm. The nonlinear crystal temperature is kept at 120.0 ± 0.1°C and a domain period of 30 μm is used in this experiment. When the pump power is 11 W, an output power of 2.0 W at the idler wavelength of 3.479 μm has been obtained from the OPO. The optical-optical conversion efficiency is about 18.2%, and the slope efficiency is about 20.8%.     

基于单个BBO晶体载波包络相位稳定的高效率光参量放大器

基于单个BBO非线性晶体,利用非共线光参量放大技术,研究了载波包络相位稳定的高效率可调谐近红外脉冲产生.以载波包络相位稳定的飞秒激光放大系统产生的白光作为种子光,注入一个二类匹配的二级光参量放大器,在1350 nm波段获得抽运-信号光34%的转换效率.利用f—2f光谱相干测量技术,放大脉冲载波包络相位的抖动30 min内小于137 mrad.该方法提供了一种简单高效的载波包络相位稳定的红外脉冲产生技术.     

Diode-pumped continuous wave and Q-switched operation of Nd:LuAG crystal

The continuous wave (CW) and passively Q-switched performances of Nd:LuAG crystal were demonstrated. With a laser diode as pump source, the CW output power of 2.18 W was obtained under the pump power of 4.62 W, corresponding to the optical conversion efficiency of 47.2% and the slope efficiency of 52.2%. For Q-switching experiments, the shortest pulse width, largest pulse energy, and highest peak power were measured to be 12 ns, 50.6 μJ, and 4.21 kW, respectively.