Noncollinear Optical Parametric Amplifier Research Articles

Ultrafast laser system based on noncollinear optical parametric amplification for laser spectroscopy

We report the experimental demonstration of transform-limited sub-6 fs pulses at an optimal central wavelength by a tunable noncollinear optical parametric amplification (NOPA) source. Meanwhile, a white light continuum in the near-infrared (NIR) range from 900 to 1100 nm is also successfully generated by focusing the unconverted 800 nm beam during NOPA generation on a sapphire rod. Both visible-pump/visible-probe and visible-pump/NIR-probe experiments are realized using the same laser system. As examples, ultrafast photo-induced exciton dynamics inside two kinds of materials are investigated by the visible-pump/visible-probe and visible-pump/NIR-probe spectroscopy, respectively.

An innovative Yb-based ultrafast deep ultraviolet source for time-resolved photoemission experiments.

Time- and angle-resolved photoemission spectroscopy is a powerful technique to study ultrafast electronic dynamics in solids. Here, an innovative optical setup based on a 100-kHz Yb laser source is presented. Exploiting non-collinear optical parametric amplification and sum-frequency generation, ultrashort pump (hν = 1.82 eV) and ultraviolet probe (hν = 6.05 eV) pulses are generated. Overall temporal and instrumental energy resolutions of, respectively, 85 fs and 50 meV are obtained. Time- and angle-resolved measurements on BiTeI semiconductor are presented to show the capabilities of the setup.

Numerical evaluation of ultrabroadband parametric amplification in YCOB

The technique of optical parametric chirped pulse amplification has the potential to generate high-energy few-cycle pulses at high repetition rates, thanks to its high fidelity and ultrabroadband capability. The biaxial nonlinear crystal yttrium calcium oxyborate (YCOB) exhibits a favorable set of optical and thermal properties for these purposes. We evaluate numerically the performance of this crystal as the nonlinear medium in a parametric amplifier for a wide range of phase-matching parameters. We explore optimized ultrabroadband noncollinear optical parametric amplification by operating at phase-matching angles outside the principal planes.

High passive CEP stability from a few-cycle, tunable NOPA-DFG system for observation of CEP-effects in photoemission.

The investigation of fundamental mechanisms taking place on a femtosecond time scale is enabled by ultrafast pulsed laser sources. Here, the control of pulse duration, center wavelength, and especially the carrier-envelope phase has been shown to be of essential importance for coherent control of high harmonic generation and attosecond physics and, more recently, also for electron photoemission from metallic nanostructures. In this paper we demonstrate the realization of a source of 2-cycle laser pulses tunable between 1.2 and 2.1 μm, and with intrinsic CEP stability. The latter is guaranteed by difference frequency generation between the output pulse trains of two noncollinear optical parametric amplifier stages that share the same CEP variations. The CEP stability is better than 50 mrad over 20 minutes, when averaging over 100 pulses. We demonstrate the good CEP stability by measuring kinetic energy spectra of photoemitted electrons from a single metal nanostructure and by observing a clear variation of the electron yield with the CEP.

High power burst-mode optical parametric amplifier with arbitrary pulse selection

We present results from a unique burst-mode femtosecond non-collinear optical parametric amplifier (NOPA) under development for the optical - x-ray pump-probe experiments at the European X-Ray Free-Electron Laser Facility. The NOPA operates at a burst rate of 10 Hz, a duty cycle of 2.5% and an intra-burst repetition rate of up to 4.5 MHz, producing high fidelity 15 fs pulses at a center wavelength of 810 nm. Using dispersive amplification filtering of the super-continuum seed pulses allows for selectable pulse duration up to 75 fs, combined with a tuning range in excess of 100 nm whilst remaining nearly transform limited. At an intra-burst rate of 188 kHz the single pulse energy from two sequential NOPA stages reached 180 µJ, corresponding to an average power of 34W during the burst. Acousto- and electro-optic switching techniques enable the generation of transient free bursts of required length and the selection of arbitrary pulse sequences inside the burst.

A versatile femtosecond stimulated Raman spectroscopy setup with tunable pulses in the visible to near infrared

We demonstrate a versatile and efficient setup to perform femtosecond stimulated Raman spectroscopy (FSRS). Technical innovations are implemented to achieve the wavelength tunability for both the picosecond narrowband Raman pump pulse and femtosecond broadband Raman probe pulse. Using a simplified one-grating scheme in a home-built second harmonic bandwidth compressor followed by a two-stage noncollinear optical parametric amplifier, we tune the Raman pump pulse from ca. 480 to 750 nm. To generate the suitable Raman probe pulse in tandem, we rely on our recently demonstrated broadband up-converted multicolor array technique that readily provides tunable broadband laser sidebands across the visible to near-infrared range. This unique setup has unparalleled flexibility for conducting FSRS. We measure the ground-state Raman spectra of a cyclohexane standard using tunable pump-probe pairs at various wavelengths across the visible region. The best spectral resolution is ∼12 cm−1. By tuning the pump wavelength closer to the electronic absorption band of a photoacid pyranine in water, we observe the pre-resonantly enhanced Raman signal. The stimulated Raman gain of the 1627 cm−1 mode is increased by over 15 times.

Sub-10-fs pulses tunable from 480 to 980 nm from a NOPA pumped by an Yb:KGW source.

We describe two noncollinear optical parametric amplifier (NOPA) systems pumped by either the second (515 nm) or the third (343 nm) harmonic from an Yb:KGW source. Pulse durations as short as 6.8 fs are readily obtained by compression with chirped mirrors. The availability of both the second and third harmonics for NOPA pumping allows for gap-free tuning from 520 to 980 nm. The use of an intermediate NOPA to generate seed light at 780 nm extends the tuning range of the third harmonic pumped NOPA toward 450 nm.

Two MHz tunable non collinear optical parametric amplifiers with pulse durations down to 6 fs

We report on the development of a 2 MHz non collinear optical parametric amplifier (NOPA) for high repetition rate time resolved X-ray or optical spectroscopy. Our modular and very flexible device is pumped by the second and third harmonics of a commercial femtosecond Ytterbium-doped fiber laser. The amplified pulses are tunable from 520 nm to 1000 nm with pulse durations between 15 and 30 fs over the full tuning range. The same setup is also suitable for broadband amplification and we demonstrate the generation of 6 fs pulses at a central wavelength of 850 nm as well as the generation of a broadband spectrum supporting 4.2 fs transform limited pulse duration at a central wavelength of 570 nm. Very high stability and compactness is achieved thanks to an optimized mechanical design.

Sub-20 fs μJ-energy pulses tunable down to the near-UV from a 1 MHz Yb-fiber laser system.

Optical parametric amplifiers render widely tunable ultrashort pulses, but for full spectral coverage, complex mixing schemes are needed. In particular, the blue and near-UV part of the spectrum is not directly reached with the 800 nm pump from Ti:sapphire systems or the 1030 nm pump of Yb-based lasers. We combine third harmonic pumping at 343 nm with seeding by a second harmonic (SH) pumped continuum to tune a noncollinear optical parametric amplifier down to 395 nm. Together with a SH pumped branch, the full range from 395 to 970 nm is covered with 20 fs pulse length or less. Pulse energies up to the μJ-level with an average power of up to 200 mW at 200 kHz and 480 mW at 1 MHz are achieved. With additional frequency doubling, the full range down to 210 nm is reached without gap. Two-photon absorption in the amplifier crystal is discussed as the critical issue in UV-pumped systems.

Broadband picosecond radiation source based on noncollinear optical parametric amplifier

Amplification of broadband radiation of modeless dye laser by a noncollinear optical parametric amplifier based on a KTP crystal has been implemented upon pumping by second-harmonic pulses of a Nd : YAG laser. Pulses with a bandwidth of , a duration of and an energy of have been obtained at the centre wavelength of .

High gain and high spatial resolution optical parametric amplification imaging under continuous-wave laser irradiation

This paper presents a novel design for non-collinear optical parametric amplification imaging where an intense ultrashort light pulse chain is used to pump and thereby amplify a continuous-wave (CW) illuminating laser. The setup needs no temporal synchronization between the pump and the CW signal, so it is simple and compact. This design allows us to realize optical imaging for different spectral demands by flexibly changing the CW (tunable) illuminating laser sources, meanwhile with high gain and broad spatial bandwidth, by using an ultrashort pulse laser system as pump. Experimentally, a wavelength-shifted image is achieved with optical gain up to 106 and a two-dimensional space-bandwidth product of more than 20 000 based on this design.

Visualization of high-order dispersion for compression of few-cycle pulses

We present a visually intuitive method for higher-order dispersion compensation based on multi-photon interpulse interference pulse scans. The dispersion values obtained from these scans are fed back as a correction to an acousto-optical programmable dispersive filter to compensate residual higher-order dispersions up to fifth order. This method is applied to the dispersion management of a non-collinear optical parametric chirped-pulse amplifier. A grism-pair stretcher is designed based on a global dispersion balance which provides a large stretching factor and supports a spectral bandwidth of up to 320 nm. It is implemented in a two-stage three-pass non-collinear optical parametric chirped-pulse amplifier and stretches 6-fs seed pulses to about 80 ps from 700 to 1,000 nm. The amplified pulses are compressed by material dispersion. Pulses of less than 10-fs duration with a pulse energy of 125 μJ are obtained at 20-kHz repetition rate.

Carrier-envelope phase passively stabilized near-infrared laser pulses from a dual-frequency pumped noncollinear optical parametric amplifier

By inversing the signal and idler in a two-stage noncollinear optical parametric amplifier which is, respectively, pumped by the second harmonic and fundamental wave of femtosecond Ti:sapphire laser at repetition rate of 1 kHz, the carrier-envelope phase (CEP) passively stabilized pulses with a tunable wavelength from 1.1 to 1.6 μm are obtained with maximum energy of 95 μJ at 1.3 μm under the pump energy of 500 μJ. The CEP jitter of pulses is 108 mrad measured by an f-2f interferometer. This work demonstrates a new way to efficiently generate tunable near-infrared femtosecond laser pulses with self-stabilized CEP.

SNR improvement based on non-collinear OPCPA with angular spectral dispersion in BBO crystal

The characteristics of the signal-to-noise ratio (SNR) improvement based on non-collinear optical parametric chirped pulse amplification (OPCPA) with angular spectral dispersion (ASD) was revealed and investigated. The angular dispersion formula was derived theoretically and the effects of crystal length, pump peak intensity, noise characteristics and angular dispersion on the SNR improvement and conversion efficiency were discussed. Furthermore, by optimizing the critical parameters, 35% conversion efficiency and more than 3 orders of magnitude of SNR improvement were achieved for the chirped signal pulse with a central wavelength of 800nm, pumped by 532nm in presented amplification scheme with BBO crystal.

Vibrational Dynamics of Interfacial Water by Free Induction Decay Sum Frequency Generation (FID-SFG) at the Al2O3(1120)/H2O Interface.

The dephasing dynamics of a vibrational coherence may reveal the interactions of chemical functional groups with their environment. To investigate this process at a surface, we employ free induction decay sum frequency generation (FID-SFG) to measure the time that it takes for free OH stretch oscillators at the charged (pH ≈ 13, KOH) interface of alumina/water (Al2O3/H2O) to lose their collective coherence. By employing noncollinear optical parametric amplification (NOPA) technology and nonlinear vibrational spectroscopy, we showed that the single free OH peak actually corresponds to two distinct oscillators oriented opposite to each other and measured the total dephasing time, T2, of the free OH stretch modes at the Al2O3/H2O interface with a sub-40 fs temporal resolution. Our results suggested that the free OH oscillators associated with interfacial water dephase on the time scale of 89.4 ± 6.9 fs, whereas the homogeneous dephasing of interfacial alumina hydroxyls is an order of magnitude slower.

Generation of Femtosecond Laser Pulse at 1053 nm with Contrast of 10−11 by Optical-Parametric Amplification

A high contrast 1053 nm femtosecond laser pulse with free background is demonstrated based on non-collinear optical-parametric amplification (NOPA). By permuting the signal and idler in two stages of NOPAs, 48.2 fs, 62 μJ laser pulse at 1053 nm with contrast ratio of 2.3 × 10−11 is obtained within the time scale of sub-5 ps. The beam quality factors M2 for tangential and sagittal directions are 1.59 and 1.30, respectively. This work not only proves a feasible way to generate a clean femtosecond laser pulse but can also be employed as an ideal frontend for ultrashort ultrahigh intensity Nd:glass-based laser systems.

Generation of multi-color carrier-envelope phase locked pulse with continuous color tunability

Several methods exist to lock carrier envelope phase (CEP), which is generally not locked in common laser systems. Our previous work succeeded passive lock of CEP by using a technique of non-collinear optical parametric amplifier. In the present work, we have proposed and demonstrated two schemes to generate multi-color CEP-locked beams using the non-collinear optical parametric amplifier. In the first scheme, spatial filter in the spatially dispersed seed light was used to generate three-color CEP-locked pulse demonstrating its arbitral color tunability. In the second scheme, parabolic chirp was introduced on the seed pulse to generate two color CEP-locked pulses with continuous color tunability.

Generation of sub-30-fs microjoule mid-infrared pulses for ultrafast vibrational dynamics at solid/liquid interfaces

We describe temporal compression of ultrabroadband, few microjoule mid-infrared (mid-IR) pulses from a noncollinear optical parametric amplifier (NOPA) employed in a sum-frequency generation (SFG) vibrational spectroscopic system, operating in total-internal-reflection geometry. The propagation of the mid-IR beam through optical materials results in a significant temporal chirp at the probed interface, which is analyzed and corrected by properly managing the total dispersion of materials introduced into the mid-IR beam path. By employing the simultaneous spatial and temporal focusing of the broadband infrared pulses at the probed interface, we achieve a sub-50-fs full width at half-maximum (FWHM) for the instrument response function, measured via SFG cross correlation of the ultrashort mid-IR pulses with an ultrashort (~30 fs) near-IR pulse from a synchronized, independently tunable NOPA. From the SFG cross-correlation FWHM, we extract a sub-30-fs mid-IR pulse duration, making it a suitable SFG spectroscopic system to investigate vibrational dynamics in hydrogen-bonded systems at interfaces.

Carrier-envelope phase stable few-cycle pulses at 400 kHz for electron-ion coincidence experiments

Coincident electron-ion detection after photoionization in a "reaction microscope" is a very powerful tool to study atomic and molecular dynamics. However, the implementation of this tool in the field of attosecond science has so far been rather limited, due to the lack of high repetition rate laser sources capable of delivering few-cycle pulses with sufficient energy per pulse. In this article, the development of a Non-collinear Optical Parametric Amplifier (NOPA) capable of delivering Carrier-Envelope Phase (CEP) stable pulses with sub-6 fs duration and pulse energies in the few-µJ range is presented. The potential of combining the high repetition rate source and a reaction microscope operating at this high frequency is demonstrated in a proof-of-principle experiment on strong field ionization of Ar atoms.

Ultrabroadband few-cycle infrared pulse generation from a noncollinear optical parametric amplifier based on bulk niobate crystals

We describe a near-IR two-stage noncollinear optical parametric amplifier (NOPA) pumped at 800 nm that employs bulk congruent lithium niobate [LiNbO3 (c-LNB)] and bulk potassium niobate [KNbO3 (KNB)] crystals. Noncollinear phase matching in these materials allows for generation of pulses as broad as 2900 cm−1 (∼78 THz) centered in the near-IR at ∼1300 nm. In the particular geometry described here, the LNB crystal amplifies the white-light seed continuum, and the KNB crystal further amplifies the broadband near-IR pulses. Use of pulse-front matching at both nonlinear optical crystals allows for improvement of the spatiotemporal profile of the amplified ultrabroadband signal pulses and their compression to ≤22 fs. Because of the relatively high nonlinear coefficients of these crystals, we achieve overall amplification efficiencies >7% in two consecutive NOPA stages.