Pavel Malevich

High energy and average power femtosecond laser for driving mid-infrared optical parametric amplifiers

We have developed the first (to our knowledge) femtosecond Tm-fiber-laser-pumped Ho:YAG room-temperature chirped pulse amplifier system delivering scalable multimillijoule, multikilohertz pulses with a bandwidth exceeding 12 nm and average power of 15 W. The recompressed 530 fs pulses are suitable for broadband white light generation in transparent solids, which makes the developed source ideal for both pumping and seeding optical parametric amplifiers operating in the mid-IR spectral range.

Ultrafast-laser-induced backward stimulated Raman scattering for tracing atmospheric gases

By combining tunable broadband pulse generation with the technique of nonlinear spectral compression we demonstrate a prototype scheme for highly selective detection of air molecules by backward stimulated Raman scattering. The experimental results allow to extrapolate the laser parameters required for standoff sensing based on the recently demonstrated backward atmospheric lasing.

Multi-millijoule few-cycle mid-infrared pulses through nonlinear self-compression in bulk

The physics of strong-field applications requires driver laser pulses that are both energetic and extremely short. Whereas optical amplifiers, laser and parametric, boost the energy, their gain bandwidth restricts the attainable pulse duration, requiring additional nonlinear spectral broadening to enable few or even single cycle compression and a corresponding peak power increase. Here we demonstrate, in the mid-infrared wavelength range that is important for scaling the ponderomotive energy in strong-field interactions, a simple energy-efficient and scalable soliton-like pulse compression in a mm-long yttrium aluminium garnet crystal with no additional dispersion management. Sub-three-cycle pulses with >0.44 TW peak power are compressed and extracted before the onset of modulation instability and multiple filamentation as a result of a favourable interplay between strong anomalous dispersion and optical nonlinearity around the wavelength of 3.9 μm. As a manifestation of the increased peak power, we show the evidence of mid-infrared pulse filamentation in atmospheric air.

Parametric amplification of 100 fs mid-infrared pulses in ZnGeP 2 driven by a Ho:YAG chirped-pulse amplifier

We report on the parametric generation of 100 fs sub-6-cycle 40 μJ pulses with the center wavelength at 5.2 μm using a 1 ps 2.1 μm pump laser and a dispersion management scheme based on bulk material. Our optically synchronized amplifier chain consists of a Ho:YAG chirped-pulse amplifier and white-light-seeded optical parametric amplifiers providing simultaneous passive carrier-envelope phase locking of three ultrashort longwave pulses at the pump, signal, and idler wavelengths corresponding, respectively, to 2.1, 3.5, and 5.2 μm. We also demonstrate bandwidth enhancement and efficient control over nonlinear spectral phase in the regime of cascaded χ2 nonlinearity in ZnGeP2.

Stimulated Raman gas sensing by backward UV lasing from a femtosecond filament

We perform a proof-of-principle demonstration of chemically specific standoff gas sensing, in which a coherent stimulated Raman signal is detected in the direction anticollinear to a two-color laser excitation beam traversing the target volume. The proposed geometry is intrinsically free space as it does not involve back-scattering (reflection) of the signal or excitation beams at or behind the target. A beam carrying an intense mid-IR femtosecond (fs) pulse and a parametrically generated picosecond (ps) UV Stokes pulse is fired in the forward direction. A fs filament, produced by the intense mid-IR pulse, emits a backward-propagating narrowband ps laser pulse at the 337 and 357 nm transitions of excited molecular nitrogen, thus supplying a counter-propagating Raman pump pulse. The scheme is linearly sensitive to species concentration and provides both transverse and longitudinal spatial resolution.

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.

High-Repetition-Rate Multi-Millijoule Femtosecond 2.1 μm Ho:YAG Laser

Femtosecond Ho:YAG room-temperature CPA system delivering scalable multi-mJ multi-kHz pulses with a bandwidth exceeding 12 nm and average power of 15 W is presented. Broadband white light generation with the recompressed 530-fs pulses is demonstrated.

Femtosecond 3-mJ 5-kHz cw-pumped Ho:YAG CPA

We demonstrate the first femtosecond Tm-fiber-pumped Ho:YAG room-temperature CPA system delivering scalable multi-mJ multi-kHz pulses with a bandwidth exceeding 12 nm and the average power of 15 W. The output is partially recompressed to 530 fs FWHM.

Modeling and iterative pulse-shape control of optical chirped pulse amplifiers

Abstract In this paper, we present an iterative learning algorithm for pulse-shape control applications of optical chirped pulse amplifiers for ultra-short, high-energy light pulses. For this, we first introduce a general nonlinear and infinite-dimensional mathematical model of chirped pulse amplifiers. By reducing the complexity of this detailed model and reformulating the control task, we are subsequently able to apply inversion-based iterative learning control to track desired output pulses. Using the reduced model to estimate both internal states and unknown parameters yields a fast and simple way of consistently estimating the input–output behavior without relying on a calibrated system model. The effectiveness of the resulting adaptive algorithm is finally illustrated with simulation scenarios on an experimentally validated mathematical model.

Identifikation und Simulation optischer Verstärker für ultra-kurze Laserpulse

Zusammenfassung Die Beschreibung optischer Pulsverstärker für ultra-kurze Laserpulse resultiert in mathematisch aufwendigen, verteilt-parametrischen Modellen, deren detaillierte Modellierung und adaptive Regelung unlängst präsentiert wurde. In diesem Beitrag werden nun Aspekte der Identifikation geeigneter Parameter betrachtet, um ein gemessenes Eingangs-Ausgangs-Verhalten möglichst gut nachbilden zu können. Dazu werden effiziente Simulationsmodelle präsentiert, die den numerischen Aufwand – besonders bei hohen Wiederholraten und der dadurch auftretenden starken Verkopplung aufeinanderfolgender Pulse – in handhabbaren Grenzen halten.