Podcasts about opcpa

Chirped pulse amplification in solid-state lasers is currently the method of choice for producing high-energy ultrashort pulses, having surpassed the performance of dye lasers over 20 years ago. The third generation of femtosecond technology based on short-pulse-pumped optical parametric chirped pulse amplification (OPCPA) holds promise for providing few-cycle pulses with terawatt-scale peak powers and kilowatt-scale-average powers simultaneously, heralding the next wave of attosecond and femtosecond science. OPCPA laser systems pumped by near-1-ps pulses support broadband and efficient amplification of few-cycle pulses due to their unrivaled gain per unit length. This is rooted in the high threshold for dielectric breakdown of the nonlinear crystals for even shorter pump pulse durations. Concomitantly, short pump pulses simplify dispersion management and improve the temporal contrast of the amplified signal. This thesis covers the main experimental and theoretical steps required to design and operate a high-power, high-energy, few-cycle OPCPA. This includes the generation of a broadband, high-contrast, carrier envelope phase (CEP)-stable seed, the practical use of a high-power thin-disk regenerative amplifier, its efficient use for pumping a multi-stage OPCPA chain and compression of the resulting pulses. A theoretical exploration of the concept and its extension to different modes of operation, including widely-tunable, high-power multi-cycle pulse trains, and ultrabroadband waveform synthesis is presented. Finally, a conceptual design of a field synthesizer with multi-terawatt, multi-octave light transients is discussed, which holds promise for extending the photon energy attainable via high harmonic generation to several kiloelectronvolts, nourishing the hope for attosecond spectroscopy at hard-x-ray wavelengths.

Wed, 27 Aug 2014 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/17400/ https://edoc.ub.uni-muenchen.de/17400/1/Skrobol_Christoph.pdf Skrobol, Christoph ddc:530, ddc:500, Fakultät für Physik

Few-cycle laser pulses are an important tool for investigating laser-matter interactions. Apart from the mere resolution used in time-resolved processes, owing to this approach table-top sources nowadays can reach the limits of the perturbative regime and therewith enable extreme nonlinear optics. In the visible domain, femtosecond technology over the last decades has quickly developed, in recent years leading to the routine generation of carrier-envelope phase (CEP) stable few-cycle laser pulses at high energies, using ubiquitous Ti:Sapphire amplifiers. Near to mid-infrared few-cycle pulses in contrast can be employed for investigating interactions in the tunneling regime. The ponderomotive potential of the infrared light field allows quivered charged particles to acquire large energies, leading to applications like the generation of isolated attosecond pulses in the water window. In this wavelength regime however, the required sources are yet to be demonstrated or at least matured. The best candidate for few-cycle pulses in this domain is optical parametric amplification. This work describes the development of an optical parametric chirped pulse amplifier (OPCPA), used to create CEP-stable few-cycle pulses in the near infrared (NIR). It covers all essential parts of the system. First the signal pulses are generated from ultrashort lasers using spectral broadening techniques in chapter 2. After compression of these white light continua, intra-pulse broadband difference frequency generation yields CEP stable infrared pulses spanning over more than one octave. A thin-disk-based pump laser provides ample pump energy (20 mJ) at pulse durations around 1.5 ps. Its characterization and optimization for OPCPA is performed in chapter 3. The high peak energy of this pump laser leads to the buildup of optical nonlinearities and consequently shows distinct influence on the OPCPA system performance. The synchronization of the OPCPA pump and seed laser system is the topic of chapter 4. This chapter is not limited to NIR systems, but demonstrates enhanced (actively stabilized) synchronization of the jitter between pump and seed pulses to σ = 24 fs, which later results in improved output stability. The NIR OPCPA centered at 2.1 μm is described in chapter 5. This combines the efforts of the previous chapters and describes the generation and characterization of 100 μJ sub-two-cycle CEP-stable pulses, the shortest published to date at this energy level. As a first prototype (cutting edge) experiment, CEP dependent sub-fs currents in a dielectric are generated in chapter 6 using the developed light source. The results compared well to visible few-cycle laser sources and demonstrate the usability of the OPCPA system (beyond the charac- terizations of chapter 5) for investigating sub-cycle carrier dynamics in dielectrics. For the same purpose, to generate the currently most broadband NIR continua at kHz repetition rates and mJ-level pulse energies, the OPCPA system is further boosted and efficiently broadened to three optical octaves using a hollow core fiber setup (described in chapter 7). The spectral phase is characterized and demonstrates self-compression in the NIR around 1.3 μm. The process provides CEP-stable sub-2-cycle pulses in this regime directly, the shortest and most powerful reported to date. Furthermore, the spectral broadening in the infrared shows enhanced low-order harmonic gen- eration and cross-phase-modulation as the dominant mechanism. Experimentally the limited influence on the driver bandwidth is investigated. It is found that the processes allow using more efficient many-cycle infrared sources to generate several-octave spanning, compressible continua in the future. Even partial compression of these would then provide NIR transients for high-field experiments.

The petawatt field synthesizer (PFS) is a high-power optical parametric chirped-pulse amplification (OPCPA) system under development, which aims at generating fewcycle pulses with high energies of several Joule. The availability of light pulses with these unique parameters will enable an efficient generation of even shorter attosecond pulses with significantly higher photon flux than achievable today [1]. Not only the real-time observation, but also the control of charge transfer in molecular systems will become feasible for the first time [2]. The technique for realizing the ambitious PFS specifications is short-pulse pumped OPCPA in mm-thin crystals. The reduced crystal thickness allows for ultra-broadband amplification. The pump-pulse duration is reduced to a picosecond—compared to 100 ps to nanosecond pump-pulse duration in conventional high power OPCPA systems. The shortened pulse duration facilitates higher pump intensities whereby an efficient amplification in the mm-thin crystals is achieved. The demonstration of this novel scheme in the PFS project will allow its use in the extreme light infrastructure (ELI)[3]—a pan-European high-power laser project. Based on the PFS technology for the front end, the ELI will generate exawatt peakpower pulses and therefore facilitate the study of laser-matter interaction in an unprecedented intensity range [4]. This work describes the CPA-aspects of a suitable chirped pulse amplification (CPA) pump laser for the PFS OPCPA system. The diode-pumped Yb:YAG amplifiers up to an energy of 300 mJ (at 1030 nm) are presented in combination with the dispersion management. The application of spectral-amplitude shaping in conjunction with an Yb:glass amplifier with broader bandwidth than Yb:YAG enables an unprecedented bandwidth of 3.5nm in the Yb:YAG amplifier at this energy level. Simulations show that a similar bandwidth can be maintained for the full amplifier system. The pulses with 200 mJ could be compressed to 900 fs, close to the transform limit. Later changes in the stretcher increase the bandwidth more and compression down to 740 fs is demonstrated. To date, these are the highest peak power pulses generated in Yb:YAG. For the application as OPCPA pump, the so generated pulses are frequency doubled in a DKDP crystal. Another key aspect of this work is the synchronization of the OPCPA pump and signal pulses. In spite of optical synchronization of both pulses, a large timing fluctuation between these pulses is measured at the first OPCPA stage. The high accuracy jitter measurement setup and a series of measurements, which showed that the stretcher/compressor setup is the main source of jitter, are presented. Theoretical investigations yield that the optical delay in a compressor is orders of magnitude more sensitive to angle changes compared to free space propagation. This makes the stretcher and compressor extremely sensitive for timing jitter caused by turbulent air or mechanical instabilities. This novel insight helped us to significantly reduce the jitter to 100 fs and to demonstrate the feasibility of the PFS concept with first broad-band OPCPA experiments.

The scheme of short-pulse pumped optical parametric chirped-pulse amplification (OPCPA) offers a promising route towards a completely new regime of ultra-high power few-cycle pulse generation, which reaches well beyond the limits of the conventional laser technology. In this approach, the gain bandwidth limitations of conventional laser amplification are circumvented by using thin OPA crystals in a non-collinear pump-signal geometry (NOPA), while the high gain and pulse energies are ensured by the intense pumping and large crystals sizes. The Petawatt-Field-Synthesizer (PFS) project at the Max Planck Institute of Quantum Optics (Garching, Germany), aims at delivering waveform-controlled few-cycle laser pulses with PW-scale peak power based on few-ps pumped OPCPA. This work focuses on the development of a frontend light source for the PFS system to deliver optically synchronized seed pulses for the OPCPA beam-line and the pump laser. Methods of generating the broadband near-infrared seed pulses for the OPCPA chain by spectral broadening using few-cycle pulses, and idler generation using NOPA are presented. Concepts of stretching both seed pulses, for the pump and the OPCPA, in time and their recompression after amplification are discussed. A detailed experimental and theoretical investigation of timing jitter between the pump and seed pulses in our system is presented. The experimental demonstration of shortpulse-pumped non-collinear OPCPA in a DKDP crystal is presented showing an ultrabroad gain bandwidth in the visible-near infrared, which supports sub-two optical cycle pulse duration.

Fri, 1 Feb 2008 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/8006/ https://edoc.ub.uni-muenchen.de/8006/1/Tavella_Franz.pdf Tavella, Franz ddc:500, ddc:530, Fakultät für Phy

In this work, optical pulse amplification by parametric chirped-pulse amplification (OPCPA) has been applied to the generation of high-energy, few-cycle optical pulses in the near-infrared (NIR) and infrared (IR) spectral regions. Amplification of such pulses is ordinarily difficult to achieve by existing techniques of pulse amplification based on standard laser gain media followed by external compression. Potential applications of few-cycle pulses in the IR have also been demonstrated. The NIR OPCPA system produces 0.5-terawatt (10 fs, 5 mJ) pulses by use of noncollinearly phase-matched optical parametric amplification and a down-chirping stretcher and upchirping compressor pair. An IR OPCPA system was also developed which produces 20-gigawatt (20 fs, 350 uJ pulses at 2.1 um. The IR seed pulse is generated by optical rectification of a broadband pulse and therefore it exhibits a self-stabilized carrier-envelope phase (CEP). In the IR OPCPA a common laser source is used to generate the pump and seed resulting in an inherent sub-picosecond optical synchronization between the two pulses. This was achieved by use of a custom-built Nd:YLF picosecond pump pulse amplifier that is directly seeded with optical pulses from a custom-built ultrabroadband Ti:sapphire oscillator. Synchronization between the pump and seed pulses is critical for efficient and stable amplification. Two spectroscopic applications which utilize these unique sources have been demonstrated. First, the visible supercontinuum was generated in a solid-state media by the infrared optical pulses and through which the carrier-envelope phase (CEP) of the driving pulse was measured with an f-to-3f interferometer. This measurement confirms the self-stabilization mechanism of the CEP in a difference frequency generation process and the preservation of the CEP during optical parametric amplification. Second, high-order harmonics with energies extending beyond 200 eV were generated with the few-cycle infrared pulses in an argon target. Because of the longer carrier period, the IR pulses transfer more quiver energy to ionized free electrons compared to conventional NIR pulses. Therefore, higher energy radiation is emitted upon recombination of the accelerated electrons. This result shows the highest photon energy generated by a laser excitation in neutral argon.