Optical Parametric Amplifier Output Research Articles

Investigation of a widely-tunable subnanosecond BBO-based optical parametric amplifier

We report an experimental realization of a subnanosecond optical parametric amplifier (OPA) system in a beta barium borate (BBO) crystal pumped by the third harmonic of a passively Q-switched Nd:YAG microlaser system and seeded by the continuum generated in a photonic crystal fibre (PCF). It yields broadband continuous signal wavelength tunability in the visible spectrum range from 470 to 660 nm and the idler wavelength from 768 to 1450 nm. Besides the experimental data, the numerical simulation results of the BBO optical parametric amplifier are presented. The maximum output power of the subnanosecond BBO OPA is limited by laser induced damage in the BBO crystal by the pump radiation and seed radiation spectral power density. We also notice and discuss the effect of seed radiation on BBO OPA output radiation characteristics. The numerical simulations qualitatively agree with the experimental data.

Modulated Noncollinear Optical Parametric Amplifier Output Induced by Stimulated Raman Scattering

We studied spectra of the amplified signal from a noncollinear optical parametric amplifier (NOPA) based on a Ti:sapphire laser and BBO crystal gain medium. The signal shows characteristic structures with periodic intensity variations in the signal during the parametric amplification processes in a BBO crystal. This phenomenon is attributed to the stimulated Raman process excited by the pump pulse affected by the phase-matching condition of four-wave mixing. The effect of this stimulated Raman process on optical parametric amplification and on final pulse compression of the signal was analyzed. The results demonstrate that caution must be taken when constructing a NOPA. Specifically, great care must be taken not to use mirrors with non-uniform spectral reflectivity for obtaining a stable pulse in terms of both temporal and spectral shapes.

High conversion efficiency of an optical parametric amplifier pumped by 1 kHz Ti:Sapphire laser pulses for tunable high-harmonic generation.

We report that high-conversion efficiency of nearly 50% has been realized by combining a commercially available Ti:Sapphire femtosecond, 1 kHz laser system and an optical parametric amplifier (OPA). For an input energy of 2.2 mJ/pulse at 1 kHz and 35 fs duration, the total OPA output energy of the signal plus idler pulses is 1.09 mJ/pulse at a signal wavelength of 1310 nm. We found that the output beam profile is almost flat-top due to high gain saturation in the OPA. Using the signal pulse, we generate high-harmonics in gases and measure the velocity map images of photoelectrons ionized from argon gas as a function of the signal wavelength. We observe that in a particular range of the high-harmonic photon energy, a four-fold photoelectron angular structure is observed in the low kinetic energy region. Our results indicate that the output pulses with the high-conversion efficiency OPA and super Gaussian beam profile can be used for experiments requiring generation of tunable high-harmonics in the extreme ultra-violet region.

Phase stabilization of an attosecond beamline combining two IR colors.

We present a phase-stabilized attosecond pump-probe beamline involving two separate infrared wavelengths for high-harmonic generation (HHG) and pump or probe. The output of a Ti:sapphire laser is partly used to generate attosecond pulses via HHG and partly to pump an optical parametric amplifier (OPA) that converts the primary Ti:sapphire radiation to a longer wavelength. The attosecond pulse and down-converted infrared are recombined after a more than 20-m-long Mach-Zehnder interferometer that spans across two laboratories and separate optical tables. We demonstrate a technique for active stabilization of the relative phase of the pump and probe to within 450 as rms, without the need for an auxiliary continuous wave (cw) laser. The long-term stability of our system is demonstrated with an attosecond photoelectron streaking experiment. While the technique has been shown for one specific OPA output wavelength (1560 nm), it should also be applicable to other OPA output wavelengths. Our setup design permits tuning of the OPA wavelength independently from the attosecond pulse generation. This approach yields new possibilities for studying the wavelength-dependence of field-driven attosecond electron dynamics in various systems.

Optical parametric amplification of carrier-envelope phase-stabilized mid-infrared pulses generated by intra-pulse difference frequency generation.

We report on a wavelength-tunable optical parametric amplifier (OPA) from 2.7 to 3.8 μm seeded with carrier-envelope phase (CEP) stabilized pulses generated by intra-pulse difference frequency generation (DFG) using a commercial Yb:KGW chirped-pulse amplifier. The Yb:KGW laser's output pulses are spectrally broadened in two-stage multi-plate pulse compression from 0.8 to 1.25 μm, which are compressed down to a sub-two-cycle duration of 6.5 fs using chirp mirrors. CEP-stabilized mid-infrared pulses are produced in intra-pulse DFG of the spectrally broaden pulses around 1.03 μm and parametrically amplified in KTiOAsO4 crystals. The output energy and temporal duration of the OPA output pulses range from 31 to 56 μJ and from 102 to 203 fs, respectively. The root mean square value of their CEP errors is measured to be 101 mrad.

Two-stage optical parametric amplifier of a low energy nanosecond pulses

A two-stage optical parametric amplifier (OPA) design that provides over −5 × 107 gain at 1053 nm is presented. Noise level of the parametric amplifier in the signal wave propagation direction was 2 × 10−6 from the signal level. The parasitic parametric oscillation under intense pump wave and its contribution to the OPA output was measured to be less than 8%.

Generation of high-order harmonic continuum with two-hump-structure infrared laser pulse

We experimentally investigate the high-order harmonic generation in argon gas cell driven by a multi-cycle broadband infrared laser pulse from a tunable optical-parametric-amplifier (OPA) source. The generation of high-order harmonic continuum with the cut-off photon energy up to 110 eV is observed by tuning the chirp of the 800-nm laser pulse which pumps OPA source. The generation of harmonic continuum is understood in terms of the two-hump structure of the OPA output spectrum and the optimal relative phase of the two humps. The demonstrated scheme is of importance for the generation of extreme ultraviolet (XUV) continuum at higher photon energy region.

Ground demonstration of trace gas lidar based on optical parametric amplifier

We report on the development effort of a nanosecond-pulsed optical parametric amplifier (OPA) for remote trace gas measurements for Mars and Earth. The OPA output has ∼500 MHz linewidth and is widely tunable at both near-infrared and mid-infrared wavelengths, with an optical-optical conversion efficiency of up to ∼39% . Using this laser source, we demonstrated open-path measurements of CH 4 (3291 and 1652 nm), CO 2 (1573 nm), H 2 O (1652 nm), and CO (4764 nm) on the ground. The simplicity, tunability, and power scalability of the OPA make it a strong candidate for general planetary lidar instruments, which will offer important information on the origins of the planet's geology, atmosphere, and potential for biology.

Carrier-envelope phase offset for pulses from a tunable optical parametric amplifier

The carrier-envelope phase (CEP) characteristics of the tunable infrared laser pulses from a noncollinear optical parametric amplifier (OPA) with passively stabilized CEP are investigated experimentally. We compare the CEP fluctuation of different wavelength outputs from the OPA which is seeded by the idler pulse of a difference frequency generation (DFG) process. It is found that when the OPA output is tuned to a longer wavelength, the CEP fluctuation becomes less sensitive to the jitter of laser intensity and the phase mismatch, and therefore more stable CEP for the longer wavelength output pulses is realized.

Quantum properties of a spatially-broadband traveling-wave phase-sensitive optical parametric amplifier

We present the quantum theory of a spatially-multimode traveling-wave phase-sensitive optical parametric amplifier (OPA) pumped by a beam with arbitrary spatial profile. By using Green's functions of the classical OPA, we derive the normally-ordered quadrature correlators at the OPA output, which provide complete quantum description of the phase-sensitive OPA and enable determination of its independently-squeezed eigenmodes. Two analytically treatable examples of plane-wave pump and infinite spatial bandwidth of the crystal are discussed in detail.

Generation of 20 fs, 20 MW pulses in the near-infrared by pulse compression using a large-mode-area all-silica photonic band-gap fiber

Spectral broadening in the regime of normal dispersion in a large-mode-area all-silica photonic band-gap fiber (PBGF) is shown to enable compression of an optical parametric amplifier output with a peak power of 3 MW, a central wavelength of 1140 nm, and an initial pulse width of about 200 fs to a minimum pulse width of 20 fs, corresponding to a maximum peak power of 20 MW. The spectral bandwidth of the PBGF output generated in our experiments is sufficient to support compression to a two-cycle pulse width.

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.

Tunable high harmonic generation with an optical parametric amplifier

A high-intensity 1014 W/cm2 optical parametric amplifier (OPA) was developed to generate tunable infrared pulses for high harmonic generation (HHG). The HHG experiments with xenon and argon gases using the OPA output were performed with a kHz gas valve. The tunable nature of the OPA led to tunable HHG, resulting in a source of fully tunable coherent XUV radiation from 0.22 μm to the HHG cutoff. Compared with the conventional 800 nm (Ti:sapphire) driving field, increasing the driving wavelength by an OPA also significantly extended the cutoff photon energy of the HHG.

A high-flux entanglement source based on a doubly resonant optical parametric amplifier

A 532 nm pumped type-II phase-matched, doubly resonant KTP optical parametric amplifier (OPA) was operated near frequency degeneracy to yield an inferred downconverted photon pair production rate of 1.7×106 s-1 at a pump power of 100 µW. The OPA output consisted of three components: narrowband doubly resonant mode pairs; narrowband singly resonant mode pairs for which either the signal or idler was resonant with the cavity and broadband nonresonant mode pairs. Under frequency-degenerate operation, the broadband nonresonant mode pairs were polarization triplet states. We observed quantum interference between the orthogonally polarized photons of the triplet states when they were analysed with a polarizer set at 45° relative to the OPA's output polarizations, leading to reduced coincidence counts.