V. Pasiskevicius

First-order type II quasi-phase-matched UV generation in periodically poled KTP

Type II quasi-phase matching was employed for first-order frequency doubling of a single-longitudinal-mode Ti:sapphire laser in periodically poled KTP with a domain-inverted period of 9.01 mum . In a single-pass configuration, 0.44 mW of UV power at 398.8 nm was generated for an input of 780 mW, corresponding to a normalized conversion efficiency of 0.09%W(-1) cm(-1) . The nonlinear coefficient d(24) = 2.82 pm/V was deduced from the measurements. The larger grating period for the type II quasi-phase-matched second-harmonic-generation process than for type I quasi-phase matching, lowers the fabrication constrains in the short-wavelength region and increases the acceptance bandwidth.

Efficient nanosecond optical parametric oscillators based on periodically poled KTP emitting in the 1.8–2.5-µm spectral region

The use of periodically poled KTiOPO(4) as a gain medium in efficient nanosecond optical parametric oscillators pumped by a flash-lamp-pumped Q-switched Nd:YAG laser is demonstrated. Parametric radiation in the 1.8-2.5-mu m spectral region was achieved when the crystal temperature was tuned from 10 to 100 degrees C. A maximum total output energy of 1.8 mJ was obtained at a pump level of 3.5 mJ. Stable operation was achieved, with conversion efficiencies reaching 50%. No gray tracking or laser damage was observed, even for pump intensities of 450MW/cm(2).

Laser performance of Yb:GdCa4O(BO3)3 compared to Yb:KGd(WO4)2 under diode-bar pumping

A study of Yb:GdCOB under diode-bar pumping has been performed and the results are compared, experimentally and theoretically, with Yb:KGW in the same cavity. An output power of 7.3 W and a slope efficiency of 57.4% were obtained. Self-frequency-doubling experiments are also discussed.

Simultaneous second-harmonic generation with two orthogonal polarization states in periodically poled KTP

Simultaneous generation of second-harmonic light with orthogonal polarizations in the blue spectral region is demonstrated by use of typeII and typeI quasi-phase matching for the nonlinear coefficients d(33) , d(24) , and d(32) in periodically poled KTP. The second-harmonic power ratio in both polarization states can be tuned by the fundamental polarization and (or) the periodically poled KTP temperature. Femtosecond pulse frequency-doubling efficiencies of as much as 39.5% W (-1) and 8.1% W (-1) are demonstrated in 7-mm periodically poled KTP for typeI and typeII processes, respectively. The efficiency limitations caused by various effects of the group-velocity mismatch are discussed.

Noncollinear frequency conversion in the PPKTP

Summary form only given. Noncollinear interaction in birefringence phase-matched nonlinear crystals is usually used for the tuning of the output wavelength and group-velocity matching in short pulse optical parametric generators. The output beam shaping in travelling wave optical parametric generator (TOPG) with bulk crystal pumped by a Bessel beam in multiple noncollinear phase matching geometry has been demonstrated. In periodically poled KTiOPO/sub 4/ (KTP) (PPKTP) the effective nonlinear coefficients are several times larger than in the case of birefringence phase-matching. So relatively low parametric generation threshold has been demonstrated recently. We have investigated the second harmonic (SH) generation in PPKTP crystal pumped by Bessel beam in multiple noncollinear phase matching geometry.

Efficient femtosecond traveling-wave optical parametric amplification in periodically poled KTiOPO/sub 4/

Summary form only given. Group velocity mismatch (GVM) which determines the nonlinear interaction length in ultrafast parametric processes limits the useful length of the nonlinear medium and increases threshold of the parametric process. Quasi-phase-matched nonlinear materials provide higher nonlinear coefficients d/sub eff/ in noncritical interaction and can potentially offset the GVM-related increase in threshold. We report on the experiments of a seeded traveling wave optical parametric amplifier (OPA) based on periodically poled KTiOPO/sub 4/ (PPKTP) with femtosecond pumping near 800 nm.

Diode-pumped 1.54 /spl mu/m Er-Yb:GdCOB lasers

We present the investigation of longitudinally pumped microchip Yb-Er lasers based on new crystalline medium GdCa/sub 4/O(BO/sub 3/)/sub 3/. The main potential advantage of these crystals over Er-Yb glasses is the higher thermal conductivity, which may lead to higher thermal damage threshold. The advantage of GdCa/sub 4/O(BO/sub 3/)/sub 3/ (GdCOB) over YCOB is its lower melting point are discussed.

Passive Q-Switching at 1.54 mm of a Er-Yb:GdCa4O(BO3)3 Laser with a Co :MgAl2O4 Saturable Absorber

A train of Q-switched pulses is formed in a diode-pumped microchip laser consisting of an Er-Yb:GdCa4O(BO3)3 active and a Co2+:MgAl2O4 passive elements. The pulses durations were in the range of 1.6-6 ns.

Generation of 100-kW-level pulses at 1.53 um in the diode-pumped Er-Yb:glass laser-PPKTP optical parametric amplifier system

We report on the use of a compact Er-Yb:glass laser Q-switched by an AOM for seeding two-stage optical parametric amplifier realized in a single PPKTP crystal. We have generated 5 ns long pusles with a pulse energy exceeding 0.5 mJ. The parametric signal generation efficiency in the second amplification stage was 27%, while the pump depletion reached 39%. The two-stage OPA peak power gain was 30.1 dB for the seeding peak powers of 100W, while the gain reached 81 dB for the lowest seed peak powers of 0.7 mW. The OPA generated a diffraction-limited signal beam while maintaining the original spectral width of the seen.

Simultaneous UV generation with two orthogonal polarization states in periodically poled KTP

Simultaneous UV generation with two orthogonalpolarization states in periodically poled KTP