High-energy PPMgLN optical parametric oscillator pumped by a 1.064 μm E-O Q-Switched Nd:YAG laser

A high-energy PPMgLN optical parametric oscillator (OPO) pumped by a E-O Q-switched Nd:YAG laser working at 1.064 μm was successfully illustrated. A maximum output pulse energy of 3.4 mJ was obtained with a pump threshold of 1.5 mJ and a slope efficiency of 30% around room temperature. The OPO output signal and idler wavelength were 1552 and 3384 nm, respectively. The damage to the input surface of PPMgLN crystal was carefully observed with a damage threshold of 4.6 J/cm².     

Intracavity optical parametric oscillator at 1.57-μm wavelength pumped by passive Q-switched Nd：GdVO4 laser

A high-repetition-rate eye-safe optical parametric oscillator （OPO）, using a non-critically phase-matched KTP crystal intracavity pumped by a passively Q-switched Nd：GdVO4/Cr^4＋ ：YAG laser, is experimentally demonstrated. The conversion efficiency for the average power is 7% from pump diode input to OPO signal output and the slope efficiency is up to 10.3%. With an incident pump power of 7,3 W, the compact intracavity OPO （IOPO） cavity, operating at 15 kHz, produces an average power of 0.57 W at 1570 nm with a pulse width as short as 6 ns. The peak power at 1570 nm is higher than 6.3 kW.     

Travelling-wave 1.57-µm optical parametric oscillator driven by a pulsed multimode Nd3+:YAG laser

The generation properties of an optical parametric oscillator (OPO) with a three-mirror ring resonator have been investigated under conditions of a pulsed pump by multimode radiation from a Nd³⁺:YAG laser. KTP crystals were used as the OPO nonlinear medium. At pump energies up to 100 mJ, decreasing the diameter d of the Nd³⁺:YAG laser beam causes a decrease in OPO radiation divergence and an increase in the generation efficiency at λ = 1.571 μm despite a decrease in the differential efficiency. At d = 2.25 mm and a KTP crystal total length of 40 mm, the efficiency of the pump conversion to the signal-wave pulse reaches 36.5%. Based on the traveling-wave OPO, a compact, highly effective, eye-safe laser source radiating pulses of up to 35 mJ in energy, 11 nsec in duration, and 10 Hz in repetition rate at electrical pump energy of ≤ 8 J is developed. At the 86.5% level of the total pulse energy, the source-beam divergence does not exceed seven diffraction limits. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 516–523, July–August, 2008.     

Threshold characteristic of intracavity optical parametric oscillator pumped by all-solid-state Q-switched laser

We derive the threshold pump intensity for a singly resonant intracavity optical parametric oscillator (IOPO)based on a temporal coupled field model.Particular attention is paid to the dependence of the intracavity singly resonant OPO(SRO)threshold intensity on the signal wave output coupling.Meanwhile, a Nd:YAG laser pumped KTiOPO_4(KTP)IOPO for eye-safe laser output is studied experimentally. The experiment is performed with four signal wave output reflectivities of 60%,70%,80%,and 90%, respectively.The measured values are in good agreement with the theoretical results.With an output coupler reflectivity of 80%,a peak power of 70 kW at 1572 nm has been obtained at a repetition rate of 3.5 kHz.The pulse width is 4.9 ns.Such investigation is helpful to identifying suitable operational regime of low pump intensity.     

Electro-optically Q-switched high-repetition-rate1.73 μm optical parametric oscillator

We demonstrate a potassium titanyl phosphate-based optical parametric oscillator(OPO) emitting at 1729 nm.A maximum output power of 1.56 W at 1729.4 nm is obtained with an original fundamental laser power of5.48 W. The pulse with a pulse duration of 11.22 ns exceeds 3 m J at a 500 Hz repetition rate. To our knowledge this is the highest energy output of an OPO laser emitting around 1.73 μm operating at a 100 Hz order of magnitude. This laser is primarily used for bond-selective imaging of deep tissue, a promising way for diagnosing vulnerable plaques in live patients.     

Efficient all-solid-state mid-infrared optical parametric oscillator based on resonantly pumped 1.645 μm Er:YAG laser

We first report an all-solid-state tunable mid-infrared singly resonant optical parametric oscillator based on a 1532 nm laser diode resonantly pumped, Q-switched 1.645 μm Er:YAG laser. An MgO-doped periodically poled lithium niobate was used as the nonlinear material. At the pulse repetition frequency of 2 KHz, a maximum overall average output power of 0.95 W with pump power of 2.8 W was achieved, corresponding to a conversion efficiency of 34% and a slope efficiency of 38%. The temperature tuning was performed giving signal and idler ranges of 2.67 to 2.71 μm and 4.18 to 4.31 μm, respectively.     

Efficient 1.8 μm KTiOPO4 optical parametric oscillator pumped within an Nd:YAG/SrWO4 Raman laser

A 1.8?μm optical parametric oscillator (OPO) based on a noncritically phase-matched KTiOPO4 crystal is demonstrated. OPO and stimulated Raman scattering techniques are successfully combined in an acousto-optically Q-switched Nd:YAG/SrWO4 Raman laser. The device efficiently realizes three steps of conversion: from a laser diode wavelength of 808?nm to the fundamental wavelength of 1064?nm; next, to the Stokes wavelength of 1180?nm; and finally to the OPO signal wavelength of 1810?nm. With an incident diode power of 7.2?W and a pulse repetition rate of 15?kHz, an average signal power of 485?mW is obtained with a diode-to-signal conversion efficiency of 6.75%. The beam quality factors (M2) of the signal wave in both horizontal and vertical directions are measured to be 1.7±0.2. The numerical output power results of the system, the thermal lensing, and the stability parameter of the cavity are also discussed.     

A 1.54 μm Er glass laser pumped by a 1.064 μm Nd:YAG laser

Laser oscillation in Er-glass, co-doped with Yb sensitiser, has been achieved by pumping with the 1.064 μm output of a Nd:YAG laser.     

High-peak-power passively Q-switched 1.3 μm Nd:YAG/V~(3+):YAG laser pumped by a pulsed laser diode

We demonstrate a high-pulse-energy, short-pulse-width passively Q-switched(PQS) Nd:YAG∕V3t:YAG laser at 1.3 μm, which is end-pumped by a pulsed laser diode. During the PQS regime, a maximum total output pulse energy of 3.3 m J is obtained under an absorbed pump pulse energy of 21.9 m J. Up to 400 μJ single-pulse energy is realized with the shortest pulse width of 6.16 ns and a pulse repetition frequency of 34.1 k Hz,corresponding to a peak power of 64.9 k W. The high-energy laser pulse is operated in the dual wavelengths of 1319 and 1338 nm, which is a potential laser source for THz generation.     

Performance evaluation of ZnGeP_2 optical parametric oscillator pumped by a Q-switched Tm,Ho:GdVO_4 laser

A doubly resonant ZnGeP_2(ZGP)optical parametric oscillator(OPO)pumped by a novel Tm.Ho:GdVO_4 laser was demonstrated.Cryogenic Tm(5 at.-%),Ho(0.5 at.-%):GdVO_4 laser with high pulse repetition frequency(PRF)of 10 kHz at 2.05μm was employed as pumping source of ZGP OPO.The 15-mm-long ZGP crystal,55°cut forⅠ-type phase-matching with low absorption coefficient less than 0.05 cm~(-1)at 2 #m, was placed in a plano-plano cavity with resonator length of 30 mm.The ZGP OPO generated a total combined output power of 1.2 W at 3.75 and 4.52μm under pumping power of 5.3 W,corresponding to slope efficiency of 40% from incident 2-μm laser power to mid-infrared(Mid-IR)output.A widely tunable range from 3.0 to 6.5μm was achieved by changing the crystal angle only 3.5°.     

Efficient intracavity optical parametric oscillator with diode side-pumped electro-optic Q-switched laser

An efficient intracavity single-resonant optical parametric oscillator (OPO) at 1.571-μm eye-safe range using a non-critically phase-matched KTP crystal is reported. The OPO is excited by a diode side-pumped electro-optic Q-switched Nd:YAG laser at 1.064μm. Signal pulse of 97 mJ and 3.56 ns is obtained under the input electric energy of 2.3 J, corresponding to a slope efficiency of 4.2%, and a repetition rate range of 1-30 Hz.     

Resonantly pumped 1.645 μm high repetition rate Er:YAG laser Q-switched by a graphene as a saturable absorber

A fiber laser resonantly pumped 1.645 μm passively Q-switched Er:YAG laser is reported. Graphene on a silicon carbide was used as the saturable absorber for the Q-switching. The pulse energy of the 1.645 μm Q-switched Er:YAG laser was 7.05 μJ, with a pulse repetition rate of 35.6 kHz and an average output power of 251 mW.     

Highly efficient H-β Fraunhofer line optical parametric oscillator pumped by a single-frequency 355 nm laser

A highly efficient laser system output at the H-β Fraunhofer line of 486.1 nm has been demonstrated. A high pulse energy single-frequency hybrid 1064 nm master oscillator power amplifier was frequency-tripled to achieve355 nm laser pulses, which acted as the pump source of the beta barium borate nanosecond pulse optical parametric oscillator. With pump energy of 190 mJ, the laser system generated a maximum output of 62 mJ blue laser pulses at 486.1 nm, corresponding to conversion efficiency of 32.6%. The laser spectrum width was measured to be around 0.1 nm, being in conformity with the spectrum width of the solar Fraunhofer line.     

8.30 μm singly resonant ZnGeP2 optical parametric oscillators pumped by a Tm,Ho:GdVO4 laser

A single resonator 8.30 μm ZnGeP₂ (ZGP) optical parametric oscillators (OPO) was reported in the paper. The OPO was pumped by a 10.2-W Tm,Ho:GdVO₄ laser at 8 kHz in a Q-switch mode, a 170-mW idler was obtained at 8.30 μm, and the output power of the idler and signal wave was 1.0 W, corresponding to an optical-optical conversion efficiency of 10.3% and a slope efficiency of 20.9%. Tm,Ho:GdVO₄ laser was pumped by a 30-W fiber-coupled laser diode (LD) at the center wavelength of 801 nm. The output wavelength of Tm,Ho:GdVO₄ laser was at 2.05 μm, and the energy per pulse of 1.28 mJ in 18 ns was achieved at 8 kHz with the peak power of 71.1 kW.     

Q-switched mode-locking with Cr4+ : YAG in a diode pumped Nd : GdVO4 laser

We have demonstrated passively Q-switched mode-locking in a laser-diode-pumped Nd:GdVO₄ laser with an intracavity Cr⁴⁺:YAG saturable absorber. At a pump power of 19.4 W, the Q-switched mode-locked laser produced an average output power of 3.22 W, and the repetition rates of the Q-switched envelope and the mode-locked laser pulse were 227 kHz and 144 MHz, respectively. The duration of the mode-locked pulse was within the sub-nanosecond range. PACS 42.55.Xi; 42.60.Fc; 42.60.Gd; 42.55.Rz     

Passively Q-switched and mode-locked 1.3 μm Nd:YAG laser with Co:LMA saturable absorber

An xenon-lamp-pumped passively Q-switched and mode-locked (QML) Nd:YAG laser with Co:LMA saturable absorber at 1.3 μm is realized in a straight cavity. The modulation depth of mode locking pulse has reached 100%. The pulse energy and the pulse width of QML laser have been measured. The pulse width of the mode-locking laser is estamated to be 940 ps.     

Passively Q-switched 1.32-μm Nd:YAG laser with a V:YAG saturable absorber

By using a new saturable absorber V³⁺:YAG, a flash-lamp-pumped passively Q-switched Nd:YAG laser at 1.32 μm has been realized. The single-pulse energy and the pulse width of the output laser versus the pump energy are measured. With a cavity length of 440 mm and a pump energy of 43.4 J, the obtained single-pulse output energy and pulse width are 10 mJ and 86.9 ns, respectively, corresponding to a peak power of 115 kW.     

Nanosecond high-pulse energy 1.57 μm KTA optical parametric amplifier with time delay

An efficient two-stage KTi OAO4 optical parametric amplifier(OPA) system with walk-off-compensating alignment is designed. By introducing an extra time delay between the pump pulse and the signal pulse, this OPA architecture is capable of obtaining high optical conversion efficiency and high signal gain simultaneously.Finally, a maximum gain of 98 at the 1.57 μm wavelength is obtained with the signal beam quality of M2 around5.6. The efficiency of the optical conversion from 1.064 to 1.57 μm is around 26%.     

High-peak-power, high-repetition-rate intracavity optical parametric oscillator at 1.57μm

We report a high-peak-power, high-repetition-rate diode-side-pumped Nd:YAG Q-switched intracavity optical parametric oscillator (IOPO) at 1.57μm with a type-Ⅱnon-critically phase-matched x-cut KTP crystal. The average power of 1.15 W at 1.57μm is obtained at 4.3-kHz repetition rate. The peak power of the pulses amounts to 33.4 kW with 8-ns duration. The average conversion efficiency from Q-switched 1.064-μm-wavelength input power to OPO signal output power is up to 10.5%.