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We present a compact ultrafast source tunable from 2 µm to 3.5 µm with60 nJ pulses at 50 kHz repetition rate producing wideband spectra by adiabatic differencefrequency generation supporting close to single-cycle pulses.

Dissertation, Universität Hamburg, 2019; Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 172 pp. (2019). = Dissertation, Universität Hamburg, 2019, The coherent synthesis of pulses from Optical Parametric Amplifiers (OPAs) offers the possibility to realize field-controlled electromagnetic waveforms with sub-cycle durations, widely scalable in energy and spectral bandwidth.Here we demonstrate a fully functional prototype of a mJ-level two channel parametric waveform synthesizer, which is ready to be upgraded to three channels. The synthesized field, whose bandwidth covers more than 2 octaves, from ~500 nm to ~2200 nm, can be compressed to a non-sinusoidal sub-cycle waveform close to the transform-limit.The long term stable operation of such a complex laser source is achieved, for the first time, by means of a sophisticated optical and mechanical design of the whole OPA system, along with targeted improvements made to the commercial pump laser.A new seeding scheme based on multiple supercontinua, further scalable to the mid-IR, leads to excellent phase stability among the different OPA channels and to a simplified dispersion management scheme.A detailed study, both theoretical and experimental, of the couplings among different pulse parameters during the parametric amplification, unveiled novel details of the Carrier-Envelope-Phase (CEP) stabilization process via OPA, and guided the design of the CEP-controlled seeding front-end.A simplified two-dimensional spectral shearing interferometry setup, where the ancillary pulses are obtained by spectral filtering the pump pulses, has been developed to easily characterize the spectral phase of the ultrabroadband pulses from each channel, overcoming the limitation of second-harmonic-based methods.Furthermore, ad-hoc nonlinear optical techniques have been deployed to observe the most relevant synthesis parameters such as the CEP of the seeding pulses and the relative phase among the different channels outputs. Jointly with a newly developed control system, this allows to stabilize and to control the observed synthesis parameters in an orthogonal fashion.The precise control on the synthesized electric field is finally proven by the generation of high-harmonics in gases, where a continuum spanning over 50 eV of bandwidth can be obtained for suitable values of the carrier-envelope phase and relative phase among the two channels. The on-going attosecond streaking experiments will allow to fully characterize the synthesized waveforms and the attosecond pulses that can be generated.The parametric waveform synthesizer presented in this thesis demonstrates the feasibility to realize scalable high-energy multi-octave spanning sources with sub-cycle duration, that will allow to gain waveform control in strong-field light-matter interactions., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

An all in-line multi-phase detector allows to fully stabilize and control the optical waveform generated by a multi-channel, multi-stage parallel parametric waveform synthesiyzer at the experimental point. Stable HHG continuous spectra proof the short and long term stability of the synthesized waveform.

We present, to the best of our knowledge, the rst functional passively CEP-stable parametric waveform synthesizer generating custom-sculptured sub-cycle pulses with millijoule level energy. Our source delivers pulses with 0.65 optical cycles in duration centered at 1.8 µm and 600 µJ in energy. A shot-to-shot stable waveform can be synthesized over hours enabling novel prospects in attosecond pulse generation and attosecond spectroscopy.

82. Jahrestagung der DPG und DPG-Frühjahrstagung der Sektion Atome, Moleküle, Quantenoptik und Plasmen, DPG-SAMOP, Erlangen, Germany, 4 Mar 2018 - 9 Mar 2018, Coherent light-field synthesis is a promising route to scale the bandwidthof optical parametric amplifiers beyond one octave. Our visionis to create custom-tailored sub-cycle optical waveforms opening upunprecedented prospects for precision control of strong-field interactions,for the generation of intense isolated attosecond pulses and forattosecond pump-probe spectroscopy. We present our system based onthree OPA channels each featuring a three stage amplification chaindelivering a combined bandwidth of more than two octaves (500 nm -2.2 𝜇m) allowing for sub-cycle electric field transients with pulse durationsbelow 1.9 fs and millijoule-level pulse energies. The sub-cyclepulse duration allows for immediate isolated attosecond generation andthe synthesized non-sinusoidal waveforms are expected to significantlyenhance the HHG efficiency for bright isolated attosecond pulses. Thesystem is a challenging approach with respect to CEP-stable ultrabroadbandseed generation, timing synchronization, more than twooctavewide dispersion management and sufficient long term stabilityof the setup based on more than 20 non-linear crystals.

CLEO Pacific Rim, CLEO-PR, Hong Kong, China, 29 Jul 2018 - 3 Aug 2018, We present high-harmonic generation (HHG) driven with a sub-cycle mJ-levelparametric waveform synthesizer. The HHG yield and spectral shape can be controlled byvarying the carrier-envelope phase and the relative phase in the synthesizer channels.

CLEO Pacific Rim, CLEO-PR, Hong Kong, China, 29 Jul 2018 - 3 Aug 2018, Nearly transform-limited, carrier-envelope phase stable, 3.4 fs pulses with centralwavelength of 1.8 mm are generated via parametric waveform synthesis. The mJ-level energy,at 1 kHz repetition rate, allows for waveform-controlled bright high-harmonic generation.

Ultrafast Phenomena, UP2018, Hamburg, Germany, 15 Jul 2018 - 20 Jul 2018, We report on an optical synthesis of two compressed channels from our parametric waveformsynthesizer, leading to a 0:6 mJ 4:4 fs pulse (3:6 fs transform limited) with a central wavelengthof 1:8 mm, corresponding to 0:74-cycles.

82. Jahrestagung der DPG und DPG-Frühjahrstagung der Sektion Atome, Moleküle, Quantenoptik und Plasmen, DPG-SAMOP, Erlangen, Germany, 4 Mar 2018 - 9 Mar 2018, To manipulate electronic dynamics in their inherent time scale, ultrashortlaser sources delivering pulse durations below one optical cycleare being developed. Pulse characterization methods have to keeppace with the ultrabroad bandwidth of sub-cycle pulses. We presentour compact version of 2DSI, capable of characterizing a variety ofbroadband sources. The ancillary pulses can be derived by the pumplaser allowing to measure even low energy pulses within a short time.Moreover the possibility to upconvert or downconvert the fundamentalspectrum permits to measure in the visible range a large varietyof sources spanning from the IR to the UV. The two-dimensional datatrace allows for direct graphical evaluation of group delay and pulsestability. This gives the opportunity to monitor the spectral phasein realtime for > 1KHz rep. rate systems. 2DSI measurements of atwo-color driven hollow core fibre, an OPA synthesizer and an octavespanning Ti:sapphire oscillator, proof the capability to characterizeultrabroadband pulses with energies from few nJs to mJs level.

CLEO Pacific Rim, Singapore, Singapore, 31 Jul 2017 - 4 Aug 2017, We review our recent developments in parametric pulse synthesis , pumped by Ti:sapphire or Yb - doped solid - state laser amplifiers . We concentrate o n seed generation via white light generation and adiabatic frequency conversion, and show the amplified spec tra and energies

Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR, Singapore, Singapore, 31 Jul 2017 - 4 Aug 2017, We present a highly automated front-end of a Ti:Sa-based optical waveform synthesizer capable of driving multiple supercontinua with stable and controlled carrier-envelope phases. The remarkable CEP-stability of 217 mrad rms singleshot will allow shot-to-shot and long-term stable waveform synthesis.

Optics express 25(4), 3052 - 3068(2017). doi:10.1364/OE.25.003052, We introduce a simple all-inline variation of a balanced optical cross-correlator (BOC) that allows to measure the arrival time difference (ATD), over the full Nyquist bandwidth, with increased common-mode rejection and long-term stability. An FPGA-based signal processing unit allows for real-time signal normalization and enables locking to any setpoint with an unprecedented accuracy of 0.07% within an increased ATD range of more than 400 fs, resulting in attosecond resolution locking. The setup precision is verified with an out-of-loop measurement to be less than 80 as residual jitter paving the way for highly demanding applications such as parametric waveform synthesizers., Published by OSA, Washington, DC

6th International Conference on Attosecond Physics, ATTO 2017, Xi'an, China, 2 Jul 2017 - 7 Jul 2017, Intraband and interband dynamics generating high-order harmonics in solids exhibit qualitatively different responses to driver-pulse ellipticity, enabling ellipticity-based harmonic cutoff extension. Ab-initio calculations and experiments demonstrate generation of circularly polarized harmonics from single-color pulses.