Rapid-scan nonlinear time-resolved spectroscopy over arbitrary delay intervals

Femtosecond dual-comb lasers have revolutionized linear Fourier-domain spectroscopy by offering a rapid motion-free, precise and accurate measurement mode with easy registration of the combs beat note in the RF domain. Extensions of this technique found already application for nonlinear time-resolved spectroscopy within the energy limit available from sources operating at the full oscillator repetition rate. Here, we present a technique based on time filtering of femtosecond frequency combs by pulse gating in a laser amplifier. This gives the required boost to the pulse energy and provides the flexibility to engineer pairs of arbitrarily delayed wavelength-tunable pulses for pump-probe techniques. Using a dual-channel millijoule amplifier, we demonstrate programmable generation of both extremely short, fs, and extremely long (>ns) interpulse delays. A predetermined arbitrarily chosen interpulse delay can be directly realized in each successive amplifier shot, eliminating the massive waiting time required to alter the delay setting by means of an optomechanical line or an asynchronous scan of two free-running oscillators. We confirm the versatility of this delay generation method by measuring chi^(2) cross-correlation and chi^(3) multicomponent population recovery kinetics

Numerische und experimentelle Charakterisierung eines kryogen-gekühlten mehrgängigen Yb:CaF2 Laser-Verstärkers

Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersPresent thesis is dedicated to study and realization of cryogenically cooled solid-state multi-pass (MP) Yb3+:CaF2 laser amplifier. Within the scope of the thesis specific design questions as active medium choice, thermal behavior of the amplifier, pumping setup, as well as experimental results of the measurements of the amplifier performance will be considered. We have implemented MP scheme seeded by regenerative preamplifier stage and pumped with InGaAs diode laser stack, which can produce up to 200 W average power of pump radiation. Regenerative amplifier, developed during past years in Ultrafast Laser Group at Photonics Institute [Pugzlys, 2009] is capable of delivering up to 10 mJ energy in 500 ps broadband pulses with ~12 nm bandwidth at FWHM. In the framework of this work we aimed to reach 100 mJ output pulse energy at 100 Hz frequency. We provide extensive characterization of implemented MP amplifier, which includes small-signal gain measurement, output energy measurements, output pulse cross-section and spectrum measurements. We address the challenge of beam narrowing during amplification process and offer a solution to resolve it. Achievement of 100 mJ output pulse energy with spectral band of ~12 nm at FWHM at 50 Hz repetition rate is confirmed. We conduct numerical modelling of heat dissipation in the Yb:CaF2 crystal thermally bonded with blank CaF2 slabs. Thermal behavior of bonded structure is studied in dependence on the thickness of undoped regions and active area. Heat distribution in the case of double-sided pump is compared to the case of single-sided pump.7

Generation of phase-stable sub-mJ ultrashort laser pulse bursts with extremely high scalable pulse number

We demonstrate generation of bursts that consist of up to 40 ultrashort pulses with 10 μJ pulse energy, 250 fs pulse duration and an ultrashort tunable spacing, from picoseconds to nanoseconds, corresponding to a terahertz intraburst repetition rate. This was achieved by the build-up of a novel thermally-stable sub-mJ Vernier Regenerative Amplifier (RA), whose round-trip detuning is similar to its master oscillator round-trip time. The RA includes two cavities pumped from a common diode, and is able to provide for either 2 bursts (one burst out of each cavity), or for one burst and a synchronous reference pulse for characterization

Programmable generation of terahertz bursts in chirped-pulse laser amplification

Amplified bursts of laser pulses are sought for various machining, deposition, spectroscopic and strong-field applications. Standard frequency- and time-domain techniques for pulse division become inadequate when intraburst repetition rates reach the terahertz (THz) range as a consequence of inaccessible spectral resolution, requirement for interferometric stability, and collapse of the chirped pulse amplification (CPA) concept due to the loss of usable bandwidth needed for safe temporal stretching. Avoiding the burst amplification challenge and resorting to a lossy post-division of an isolated laser pulse after CPA leaves the limitations of frequency- and time-domain techniques unsolved. In this letter, we demonstrate an approach that successfully combines amplitude and phase shaping of THz bursts, formed using the Vernier effect, with active stabilization of spectral modes and efficient energy extraction from a CPA regenerative amplifier. As proof of concept, the amplified bursts of femtosecond near-infrared pulses are down-converted into tunable THz-frequency pulses via optical rectification.Comment: 7 pages, 5 Figure

Generation of a single UV pulse from a near-IR pulse burst

Date of Conference: 25-29 June 2017 in Munich, GermanySummary form only given. High harmonic generation (HHG) requires high peak-power laser sources. Most of the well-known high peak power lasers are operating in the near-IR wavelength region. Recently it was demonstrated that HHG can be effectively phase matched in the soft X-ray region by using very high intensity UV lasers and multiply charged ions [1]. High average and high peak power UV sources operating around and below 280 nm are required for many other applications, such as ablation in ophthalmology, materials processing and photoelectron spectroscopy. Due to lack of ultrafast high peak power lasers operating in UV, generation of ultrashort UV pulses is possible by up-converting frequency of near-IR laser. This can be done by cascaded harmonic generation in nonlinear crystals with efficiency higher than 40% [2]. However, to obtain high pulse energies in UV region, high energy IR pump is necessary. This becomes increasingly difficult for femtosecond laser pulses because of the optical damage problem in CPA systems. Very high pulse stretching rates in the CPA become unfeasible due to the limited size of dispersive optics. Alternatively, the intensity in the laser cavity can be decreased by using a pulse burst which effectively increases the pulse duration. Therefore, this approach is also suitable for increasing energy throughput in fiber delivery and fiber post compression schemes [3]. © 2017 IEEE

Multi-millijoule Few-Optical-Cycle Pulses in Mid-IR: Scaling Power, Energy and Wavelength

We discuss prospects of the generation of high power mid-IR pulses by analyzing soliton self-compression of multi-mJ 4-μm pulses and the development of few-optical-cycle 6-μm optical parametric amplifier. Scalability of pump lasers is addressed

Direct time-domain shaping of high-energy femtosecond pulses at THz burst frequencies

We generate fully controllable fs multimillijoule pulse bursts with the energy handling, throughput efficiency and frequency resolution substantially exceeding that achievable in spatial-light-modulator and interferometric techniques. The demonstrated proof-of-concept experiments include coherent control of nitrogen-ion emission via multiple-pulse excitation and generation of tunable narrowband THz pulses via optical rectification