Vaclav Kubecek

Generation of extended pulse trains of minimum duration by passive negative feedback applied to solid-state Q-switched lasers

Intracavity self-focusing in a thin two-photon absorber acts, in combination with pinholes, as an efficient power and energy limiter in flashlamp (pulsed) and arc lamp (CW) pumped actively passively mode-locked crystalline Nd-doped lasers. Power limiting by the intracavity two-photon absorber is exploited to create the condition for optimum pulse compression in the saturable absorber. Additional pulse shortening is due to the elimination of the pulse tail by self-defocusing in the nonlinear crystal. Extracavity and intracavity measurements, as well as three-dimensional computer simulations, give a complete understanding of the pulse evolution in the cavity, including the two mechanisms of pulse shaping and compression. >

High-power diode-pumped picosecond Nd 3+ :YVO 4 laser

A diode-pumped Nd(3+):YVO(4) laser passively mode locked by a nonlinear mirror based on second-harmonic generation has been developed. Pumping with a fiber-coupled 10-W diode array, we generated nearly diffraction limited, linearly polarized 11-ps pulses at 1064nm, with average power of 2.7 W at a 150-MHz repetition rate. Pulses as short as 7.9 ps were measured with reduced output power (1.35 W) by optimal focusing in the nonlinear crystal.

Tunable, high-energy, mid-infrared, picosecond optical parametric generator based on CdSiP 2

We report a tunable, high-energy, single-pass optical parametric generator (OPG) based on the nonlinear material, cadmium silicon phosphide, CdSiP(2). The OPG is pumped by a cavity-dumped, passively mode-locked, diode-pumped Nd:YAG oscillator, providing 25 µJ pulses in 20 ps at 5 Hz. The pump energy is further boosted by a flashlamp-pumped Nd:YAG amplifier to 2.5 mJ. The OPG is temperature tunable over 1263-1286 nm (23 nm) in the signal and 6153-6731 nm (578 nm) in the idler. Using the single-pass OPG configuration, we have generated signal pulse energy as high as 636 µJ at 1283 nm, together with idler pulse energy of 33 µJ at 6234 nm, for 2.1 mJ of input pump pulse energy. The generated signal pulses have durations of 24 ps with a FWHM spectral bandwidth of 10.4 nm at central wavelength of 1276 nm. The corresponding idler spectrum has a FWHM bandwidth of 140 nm centered at 6404 nm.

Active–passive mode-locked Nd:YAG laser with passive negative feedback

Stationary ultrashort light pulses of 10-psec duration and with an energy of 10 μJ per pulse were obtained from an active-passive mode-locked Nd:YAG laser by using a two-photon absorption limiter (GaAs) inserted into the resonator. The stability of energy in the steady-state part of the pulse train, containing approximately 90 pulses, is better than ±1.5%. The dynamics of the pulse-shortening mechanism are described, and it is shown that maximum pulse compression is reached after only approximately 10 round trips.

Long-period fiber grating as wavelength selective element in double-clad Yb-doped fiber-ring lasers

Cladding-pumped ytterbium-doped fiber lasers belong presently among the most attractive high-power laser sources for wavelengths around 1060 nm. While the most typical configuration of the fiber laser cavity is linear Fabry-Perot arrangement with fiber Bragg gratings (FBGs), for some applications the ring cavity is preferable as it offers higher stability when unidirectional operation is enforced with fiber optic isolator [1]. Indeed, Yb doped fiber lasers are prone to the so-called sustained self pulsing that in the case of highly Yb-doped fiber (YDF) may lead to relatively stable self-Q-switched operation [2]. Occurrence of this phenomenon complicates investigation of laser configurations that use other Q-switching mechanism possibly allowing for more stable operation, other repetition rate and peak power, etc

2-μm wavelength, high-energy Ho:YLF chirped-pulse amplifier for mid-infrared OPCPA

A 2-μm wavelength laser delivering up to 39-mJ energy, ∼10  ps duration pulses at 100-Hz repetition rate is reported. The system relies on chirped pulse amplification (CPA): a modelocked Er:Tm:Ho fiber-seeder is followed by a Ho:YLF-based regenerative amplifier and a cryogenically cooled Ho:YLF single pass amplifier. Stretching and compressing are performed with large aperture chirped volume Bragg gratings (CVBG). At a peak power of 3.3 GW, the stability was <1%  rms over 1 h, confirming high suitability for OPCPA and extreme nonlinear optics applications.

Experimental demonstration of novel end-pumping method for double-clad fiber devices

We present experimental demonstration of an end-pumping scheme based on splicing the multimode pump and single-mode signal fibers directly to a double-clad fiber with a tailored cross section. The method is used to pump a double-clad, erbium- and ytterbium-doped, fiber ring laser. The efficiency of the end-pumping method is tested by determining the slope efficiencies of the fiber ring laser and the fiber laser in a Fabry-Perot configuration. Comparable slope efficiencies are found when both laser configurations have similar output coupler ratios. The developed pumping scheme and double-clad fiber can find applications in cost-effective power fiber amplifiers and lasers.

Pulsed and continuous-wave laser operation of TGT-grown Nd,Y-codoped :SrF2 single crystal

In this letter we present laser properties of temperature gradient technique (TGT) grown Nd,Y : SrF2 crystals with Nd3+ concentrations of 0.4, 0.65 and 0.8 at% and Y3+ concentration of 10 at%. The noncoated crystal samples, 3.1 or 5 mm long, were pumped by the 796 nm laser diode matching the Nd,Y : SrF2 absorption peak. In the pulsed pumping regime (pulse-duration 2 ms, frequency 10 Hz), maximum average output power of 75 mW (corresponding to peak power of 3.75 W) was obtained with slope efficiency as high as 51% and optical-to-optical efficiency of 42% with respect to the absorbed pump power. The output beam spatial profile was nearly Gaussian in both axes, oscillations started at the wavelength of 1057 nm. At higher pumping levels, the second emission line at 1051 nm appears corresponding to our fluorescence measurements. Wavelength tuning using a birefringent filter from 1048 to 1070 nm is probably given by the crystal-field splitting of the 4F3/2 manifold in Nd3+. True-continuous-wave laser operation was also successfully obtained at lower pumping levels with maximum output power of 380 mW and slope efficiency of 28% at the wavelength of 1057 nm.

Practical source of 50 ps pulses using a flashlamp pumped Nd:YAG laser and passive all-solid-state pulse control

Abstract We demonstrated that a simple flashlamp pumped Nd:YAG laser, with the insertion of solid state passive elements, can be made a source of trains (and single pulse) of high power picosecond pulses with accurate pulse to pulse reproducibility. The combination of passive negative feedback using GaAs together with Cr:YAG as saturable absorber in an actively mode-locked Nd:YAG laser led to stabilizing and stretching of the pulse train to 150 ns and compression of individual pulses from 83 ps to 48 ps. Cavity dumping resulted in single pulses at energies of 300 μJ with a nearly Gaussian spatial profile at a repetition rate of 5 Hz.

Mode locking of a Nd:YAlO 3 laser at the 1.34-μm transition by a second-harmonic nonlinear mirror

A second-harmonic nonlinear mirror formed by a LiIO(3) frequency doubler and a dichroic output mirror is employed to mode lock the 1.34-microm transition of a pulsed Nd:YAlO(3) laser. Pulses of 15-ps duration are reliably generated simultaneously at 1.34 and 0.67 microm.