Shaping of picosecond pulses for pumping optical parametric amplification

The use of temporally shaped pump pulses for optical parametric chirped-pulse amplification can increase the efficiency and suppress possible spectral distortions in this process. With this goal in mind a novel method for shaping narrowband picosecond pulses has been developed. The method is based on the pulse stacking principle, where replicas of the incoming pulse are created in a specially designed four-beam interferometer. The replicas are recombined with appropriate relative delays. The interferometer design allows for a unique flexibility in varying the pulse shape, since all relevant degrees of freedom, such as relative intensities and delays between the pulse replicas are independently adjustable. Here we describe the design of our device in detail and report on the experimental demonstration of its pulse-shaping capabilities. PACS 42.65.Yj; 42.65.Re; 42.81.Gs     

Intense tunable picosecond pulses generated by parametric amplification in β-BaB2O4

Amplified spontaneous emission of a dye cell is parametrically amplified in barium betaborate (BBO) crystals. Pumping the system by the third harmonic of a Nd:YAG laser a tuning range from 3500 to 25080 cm^–1 is accessible with energy conversion efficiencies of several percent. Properties of ultrashort light pulses in the visible and UV spectral range are presented. A spectral width of 10 cm^–1 and a pulse duration of approximately 20 ps are measured.     

Optical parametric amplification of a shaped white-light continuum

Phase-locked two-color sub-40-fs double pulses in the visible are produced by noncollinear parametric amplification of white light tailored in a pulse shaper with a liquid-crystal mask. The carrier phase between the pulses is conserved during the amplification process and can be adjusted, as can the temporal separation and the center of wavelengths of the pulses.     

Tunable, high-power, narrow-band picosecond IR radiation by optical parametric amplification in KTP

We report on an optical parametric amplifier (OPA) based on two potassium titanyl phosphate (KTP) crystals in a walk-off compensating geometry. An Nd:YLF regenerative amplifier at a 1-kHz repetition rate serves as the pump source. The seed beam is delivered by a synchronously pumped frequency-stabilized optical parametric oscillator (OPO) based on periodically poled lithium niobate (PPLN). At pump intensities of about 7 GW/cm² large amplification factors of more than 10⁴ were achieved, resulting in pulse energies of more than 450 μJ and 350 μJ for the signal and idler pulses, respectively, at a 1-kHz repetition rate. In the saturation regime the time–bandwidth product increases from two to three times the Fourier limit, with a pulse duration of 105 ps and a bandwidth of 12.7 GHz at the highest intensities employed. Received: 2 November 2001 / Published online: 14 March 2002     

Tunable mid-infrared optical parametric oscillator with intracavity parametric amplification based on a dual-grating PPLN crystal

Intracavity amplification of the idler radiation of a nanosecond optical parametric oscillator (OPO) is achieved within a single dual-grating PPLN crystal composed of a uniform-grating section followed by a fan-out grating section. While all the OPO wavelength-tuning capabilities are preserved, this configuration leads to a 60?% increase of the 4-??m idler power and a significant beam quality improvement when compared to a conventional singly resonant OPO.     

ps参量放大效应

本文报道用0.53μm波长超短脉冲序列泵浦角度调谐的LiNbO_3参量晶体,获得1%单程参量放大能量转换效率,并在0.8～1.6μm范围测得参量信号光和空载光波长调谐曲线.     

Tunable,narrow-band picosecond radiation in the mid-infrared by difference frequency mixing in GaSe and CdSe

We report on the generation of tunable, narrow-band picosecond laser pulses in the mid-IR at 1 kHz repetition rate. An optical parametric oscillator (OPO) seeded optical parametric amplifier (OPA) delivers signal and idler pulses with energies of several hundred microjoule tunable between 1.56 and 3.24 m. Difference frequency mixing of the OPA signal and idler waves permits the generation of mid-IR radiation between 3 and 24 m. The laser system therefore permits full coverage of the wavelength range between 1.6 and 24 m. Conversion efficiencies greater than 50% and pulse energies up to 40 J are obtained with GaSe. PACS 42.65.Re; 42.65.Yj; 42.72.Ai     

Octave phase matching for optical parametric amplification of single-cycle pulses in the mid-infrared range

Analysis of optical properties of mid-infrared-transparent nonlinear crystals reveals octave phase matching for a highly efficient optical parametric amplification of single-cycle electromagnetic field waveforms within the 3- to 12-μm wavelength range, recently demonstrated in experiments.     

High-power picosecond mid-infrared optical parametric amplifier for infrared Raman spectroscopy

A high-power (50-MW), kilohertz, picosecond, mid-IR optical parametric amplifier that is pumped by an amplified Ti:sapphire laser and also produces a fixed-frequency visible pulse is described. Mid-IR pulse energies of 40-55 microJ with 0.6-0.8-ps durations and 35-cm (-1) bandwidths are reported in the 3650- 2800-cm (-1) range. The combination of picosecond mid-IR and visible pulses is useful for two-color spectroscopies, which require simultaneous time and frequency resolution. To illustrate the above, we present vibrational relaxation data for the polyatomic molecule nitromethane, using time-resolved infrared Raman spectroscopy.     

Efficiency-enhanced picosecond mid-infrared optical parametric downconversion based on a cascaded optical superlattice

We demonstrate an efficiency-enhanced picosecond(ps) mid-infrared radiation via optical parametric downconversion. Based on a ceiscaded periodically poled MgO-doped stoichiometric lithium tantalate crystal(MgO:sPPLT), a tandem optical parametric oscillation-optical parametric amplification(OPO-OPA) process is achieved. Compared with a single OPO process, the conversion efficiency obtains an enhancement of 71%.     

Femtosecond ultraviolet pulses generated using noncollinear optical parametric amplification and sum frequency mixing

We demonstrate the generation of ultraviolet 33-fs pulses with a shot-to-shot energy fluctuation of less than 3% using sum frequency mixing of visible pulses of a noncollinear optical parametric amplifier with sub-40-fs pulses of a 1-kHz Ti:sapphire-amplified system. The pulses are transform-limited (ΔνΔτ=0.36) and tunable in the range from 315 nm to 355 nm with energy above 1 μJ (2.6 μJ at 330 nm). Received: 21 July 2000 / Published online: 8 November 2000     

Broadband non-collinear double QPM optical parametric amplification in mid-infrared wave

The properties of optical parametric amplification (OPA) based on non-collinear double quasi-phase matching (NDQPM) with single periodically poled KTP (PPKTP) have been investigated theoretically. The NDQPM includes two different non-linear processes: one is optical parametric generation (OPG) and the other is difference frequency generation (DFG). The investigation of our numerical simulation focuses on the gain bandwidth of dependence upon non-collinear angle, grating period and crystal temperature. At a certain non-collinear angle and grating period with fixed temperature, there exists a broadest gain bandwidths of output mid-infrared pulse at 526 nm pump wavelength and certain signal wavelength in PPKTP. These are an optimal values of non-collinear angles and grating period. By accurately tuning the non-collinear angle or temperature near the optimal non-collinear angle, broadband mid-infrared tuning is obtained and an optimal operation of NDQPM can be realized. In this paper, the solutions of the coupled equations of the cascaded processes were discussed, and the spatial-temporal frequency (STF) band of the output idler pulse is analyzed by taking angular dispersion of amplified pulse beam into account. The idler pulse with a certain angular dispersion can improve the OPA bandwidth significantly. So, optical parametric chirped-pulse amplification can be realized in this configuration. For a broadband NDQPM both the acceptance angles and the acceptance temperature are smaller and the gain bandwidth is sensitive to non-collinear angles and temperature, it is important to control the precision of the non-collinear angles and the temperature in experiment.     

Phase-locked white-light continuum pulses: toward a universal optical frequency-comb synthesizer

We demonstrate that two white-light continuum pulses that are independently generated by phase-locked ultrashort laser pulses are locked in phase and show surprisingly clear and stable Young interference fringes. The experiment shows that the two generated continua emit essentially in phase and that random phase jitter can remain negligible. This result is not only of interest for studies of nonlinear field-matter interactions but also suggests that such white-light continuum pulses can be used to realize a broad frequency comb for absolute frequency measurements from the IR to the UV.     

Tunable ultraviolet source from fifth and seventh harmonic generated by mid-infrared pulses filamentation in air

The seventh harmonic generation by tunable mid-infrared femtosecond pulses filamentation in air is observed first time. Pumped by a focused mid-infrared pulses, which pulse duration is ～50 fs and wavelength is tunable from 1300 to 2000 nm, the tunable region of the fifth and seventh harmonic generation can cover the near ultraviolet region from 180 to 400 nm.     

High-temporal-quality injector generated by optical parametric amplification with hollow-core-fiber compression

We demonstrate a 100 μJ, <10 fs, high-temporal-contrast injector. The experimental setup is based on an optical parametric amplification system followed by a standard hollow-core-fiber compressor and a frequency-doubling crystal. Pulses near 800 nm with FWHMs of about 160 nm are generated. More than 11 orders of magnitude of the contrast ratio, which is limited by the measurement device, are obtained over a large temporal range extending from <1 ps ahead of the main pulse. The broad spectral bandwidth and the high contrast of this device make it a good front-end injector for a few-cycle, high-power laser system.     

High-peak power multi-wavelength picosecond pulses generated from a BaWO4 Raman-seeded optical parametric amplifier

We report the generation of high-peak power multi-wavelength picosecond laser pulses using optical parametric amplification (OPA) in BBO seeded with pulses generated in a 5-mm length BaWO₄ crystal by stimulated Raman scattering of 18-ps laser pulses at 532 nm. The maximum output energy of the amplified first-Stokes component at 559.7 nm was about 1.76 mJ. The corresponding maximum peak power, pulse duration and spectral line width were measured to be 117.3 MW, 15 ps and 18.0 cm⁻¹, respectively. The multi-wavelength picosecond laser pulses were in the visible and near infrared ranges. Using this Raman-seeded OPA technique, the beam quality of the stimulated Raman scattering pulses can be improved.     

Near-infrared continuum generation of femtosecond and picosecond pulses in doped optical fibers

We report broad continuum generation in GeO₂-doped silica fibers induced by femtosecond and picosecond pulses generated by novel high-power laser sources. Over 0.5 W of average power in a broad-band picosecond continuum is generated in the near-infrared part of the spectrum from 800 to 1500 nm. PACS 42.60.By; 42.55.Xi; 42.65.Wi; 42.81.Qb     

Laser-diode-seeded single and double stage femtosecond optical parametric amplification in the mid-infrared

Tunable mid-infrared pulses are generated with a MgO:LiNbO₃-based traveling-wave optical parametric amplifier in single and double stage operation regime pumped by a 1-kHz Ti:sapphire regenerative amplifier system. For the first time to our knowledge a pulsed laser diode is successfully used in the femtosecond regime as a compact seed source at the signal wavelength where the tunability of the generated idler pulses can be realized by tuning the seed wavelength. Almost transform limited mid-infrared pulses as short as 130 and 160 fs with pulse energies as high as 5 and 15 J are produced near 3.5 m by the single and double stage scheme, respectively. The pulse to pulse fluctuations in both cases do not exceed 2% which corresponds to the stability of the pump source.     

Generation of high-energy self-phase-stabilized pulses by difference-frequency generation followed by optical parametric amplification

We produce ultrabroadband self-phase-stabilized near-IR pulses by a novel approach where a seed pulse, obtained by difference-frequency generation of a hollow-fiber broadened supercontinuum, is amplified by a two-stage optical parametric amplifier. Energies up to 20 microJ with a pulse spectrum extending from 1.2 to 1.6 microm are demonstrated, and a route for substantial energy scaling is indicated.     

90 GW peak power few-cycle mid-infrared pulses from an optical parametric amplifier

We demonstrate a compact 20 Hz repetition-rate mid-IR OPCPA system operating at a central wavelength of 3900 nm with the tail-to-tail spectrum extending over 600 nm and delivering 8 mJ pulses that are compressed to 83 fs (<7 optical cycles). Because of the long optical period (～13 fs) and a high peak power, the system opens a range of unprecedented opportunities for tabletop ultrafast science and is particularly attractive as a driver for a highly efficient generation of ultrafast coherent x-ray continua for biomolecular and element specific imaging.