Towards High-Energy Few-Cycle Optical Vortices with Minimized Topological Charge Dispersion

A simple approach to generate high-energy few-cycle optical vortices with minimized topological charge dispersion is introduced. By means of numerical simulations it is shown that, by leveraging the intrinsic properties of optical parametric chirped pulse amplification (OPCPA), clean transfer of topological charge from a high energy narrowband pump pulse to a broadband idler is feasible under certain particular conditions, enabling the generation of high-energy few-cycle vortex pulses with extremely low topological charge dispersion

Numerical study of spatiotemporal distortions in noncollinear optical parametric chirped-pulse amplifiers

During amplification in a noncollinear optical parametric amplifier the spatial and temporal coordinates of the amplified field are inherently coupled. These couplings or distortions can limit the peak intensity, among other things. In this work, a numerical study of the spatiotemporal distortions in BBO-based noncollinear optical parametric chirped-pulse amplifiers (NOPCPAs) is presented for a wide range of parameters and for different amplification conditions. It is shown that for Gaussian pump beams, gain saturation introduces strong distortions and high conversion efficiency always comes at the price of strong spatiotemporal couplings which drastically reduce the peak intensity even when pulse fronts of the pump and the signal are matched. However, high conversion efficiencies with minimum spatiotemporal distortions can still be achieved with flat-top pump beam profiles

Efficient High-Power Ultrashort Pulse Compression in Self-Defocusing Bulk Media

Peak and average power scalability is the key feature of advancing femtosecond laser technology. Today, near-infrared light sources are capable of providing hundreds of Watts of average power. These sources, however, scarcely deliver pulses shorter than 100fs which are, for instance, highly beneficial for frequency conversion to the extreme ultraviolet or to the mid-infrared. Therefore, the development of power scalable pulse compression schemes is still an ongoing quest. This article presents the compression of 90 W average power, 190 fs pulses to 70 W, 30 fs. An increase in peak power from 18 MW to 60 MW is achieved. The compression scheme is based on cascaded phase-mismatched quadratic nonlinearities in BBO crystals. In addition to the experimental results, simulations are presented which compare spatially resolved spectra of pulses spectrally broadened in self-focusing and self-defocusing media, respectively. It is demonstrated that balancing self-defocusing and Gaussian beam convergence results in an efficient, power-scalable spectral broadening mechanism in bulk material

Multi-watt, multi-octave, mid-infrared femtosecond source

Spectroscopy in the wavelength range from 2 to 11 mu m (900 to 5000 cm(-1)) implies a multitude of applications in fundamental physics, chemistry, as well as environmental and life sciences. The related vibrational transitions, which all infrared-active small molecules, the most common functional groups, as well as biomolecules like proteins, lipids, nucleic acids, and carbohydrates exhibit, reveal information about molecular structure and composition. However, light sources and detectors in the mid-infrared have been inferior to those in the visible or near-infrared, in terms of power, bandwidth, and sensitivity, severely limiting the performance of infrared experimental techniques. This article demonstrates the generation of femtosecond radiation with up to 5 W at 4.1 mu m and 1.3 W at 8.5 mu m, corresponding to an order-of-magnitude average power increase for ultrafast light sources operating at wavelengths longer than 5 mu m. The presented concept is based on power-scalable near-infrared lasers emitting at a wavelength near 1 mu m, which pump optical parametric amplifiers. In addition, both wavelength tunability and supercontinuum generation are reported, resulting in spectral coverage from 1.6 to 10.2 mu m with power densities exceeding state-of-the-art synchrotron sources over the entire range. The flexible frequency conversion scheme is highly attractive for both up-conversion and frequency comb spectroscopy, as well as for a variety of time-domain applications

Optical parametric master oscillator and power amplifier for efficient conversion of high-energy pulses with high beam quality

We describe a system for parametric conversion of high-energy, Q-switched laser pulses from 1.064 µm to 2.1 µm in KTiOPO4. High beam quality and efficiency are obtained by use of a two-stage system: An optical parametric oscillator (OPO) pumped by a narrow beam with 8 mJ of energy, generates 1.9 mJ of signal energy for seeding an optical parametric amplifier (OPA). With 500 mJ pump energy, different OPA configurations produce up to 138 mJ signal energy with M^2 ≈ 2.3

Ultrafast Pulse Compression in Bulk with > 20 Times Spectral Broadening Factor from a Single Stage

We introduce the combination of multi-pass cell and multi-plate spectral broadening. We demonstrate the compression of 110-μJ pulses from 900-fs to 60-fs in a single stage and report broadening to 38-fs transform-limit by nonlinear mode-matching