Topic
High harmonic generation
About: High harmonic generation is a research topic. Over the lifetime, 11694 publications have been published within this topic receiving 222650 citations. The topic is also known as: HHG.
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TL;DR: In this paper, the authors tested the high-order harmonics generation (HHG) capability of bulk sapphire as a solid EUV emitter operating with moderate nJ-energy laser pulses obtained directly from an oscillator.
Abstract: Coherent extreme-ultraviolet (EUV) radiation produced by means of high-order harmonics generation (HHG) from intense laser pulses is used for various ultrafast pump–probe experiments. In this study, we test bulk sapphire as to its HHG capability as a new solid EUV emitter operating with moderate nJ-energy laser pulses obtained directly from an oscillator. Specifically, the high bandgap of sapphire (∼9 eV) permits EUV harmonics at wavelengths up to ∼60 nm for laser intensities of 1.31 TW cm–2 when irradiated by 12 fs pulses at 800 nm. The EUV output exceeds 107 photons per second without causing drastic thermal damage due to the high heat dissipation capabilities of bulk sapphire. In addition, the free-space EUV propagation can be steered by shaping the bulk surface without requiring extra grazing incidence mirrors. All these experimental findings prove the feasibility of using bulk sapphire as a desktop EUV source for relevant metrological applications.
57 citations
TL;DR: In this paper, Cireasa et al. showed that using two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields.
Abstract: Chiral discrimination with high harmonic generation (cHHG method) has been introduced in the recent work by R Cireasa et al (2015 Nat. Phys. 11 654-8). In its original implementation, the cHHG method works by detecting high harmonic emission from randomly oriented ensemble of chiral molecules driven by elliptically polarized field, as a function of ellipticity. Here we discuss future perspectives in the development of this novel method, the ways of increasing chiral dichroism using tailored laser pulses, new detection schemes involving high harmonic phase measurements, and concentration-independent approaches. Using the example of the epoxypropane molecule CH3CHCH2O (also known as 1,2-propylene oxide), we show theoretically that application of two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields. We also describe how one can introduce a new functionality to cHHG: concentration-independent measurement of the enatiomeric excess in a mixture of randomly oriented left-handed and right-handed molecules. Finally, for arbitrary configurations of laser fields, we connect the observables of the cHHG method to the amplitude and phase of chiral response, providing a basis for reconstructing wide range of chiral dynamics from cHHG measurements, with femtosecond to sub-femtosecond temporal resolution.
57 citations
TL;DR: In this article, an attosecond ionization gating is achieved using a few-cycle laser pulse in combination with its second harmonic, which can be used for EWP measurements as efficiently as a 50-as pulse, allowing one to measure a wide range of ultrafast dynamics not normally accessible before.
Abstract: An attosecond ionization gating is achieved using a few-cycle laser pulse in combination with its second harmonic. With this gating, the generation of the electron wave packet (EWP) is coherently controlled, and an isolated EWP of about 270 as is generated. An isolated broadband attosecond extreme ultraviolet pulse with a bandwidth of about 75 eV can also be generated using this gating, which can be used for EWP measurements as efficiently as a 50-as pulse, allowing one to measure a wide range of ultrafast dynamics not normally accessible before.
57 citations
TL;DR: In this article, the second harmonic generation was observed in a GaAs waveguide having a grating etched in one interface, where phase matching occurs when β2−2β1−ϑ=0, where ϑ=2π/Λ is the wave vector of the grating.
Abstract: Using a tunable laser operating near 2 μm, second harmonic generation was observed in a GaAs waveguide having a grating etched in one interface. Phase matching occurs when β2−2β1−ϑ=0, where ϑ=2π/Λ is the wave vector of the grating of period Λ and β1 and β2 are the fundamental and harmonic wave vectors.
57 citations
TL;DR: In this article, the role of optical chirality (OC) in the generation of attosecond pulses has been explored and a tricircular pump with tunable ellipticity has been proposed.
Abstract: Optical chirality (OC)-one of the fundamental quantities of electromagnetic fields-corresponds to the instantaneous chirality of light. It has been utilized for exploring chiral light-matter interactions in linear optics, but has not yet been applied to nonlinear processes. Motivated to explore the role of OC in the generation of helically polarized high-order harmonics and attosecond pulses, we first separate the OC of transversal and paraxial beams to polarization and orbital terms. We find that the polarization-associated OC of attosecond pulses corresponds approximately to that of the pump in the quasimonochromatic case, but not in the multichromatic pump cases. We associate this discrepancy with the fact that the polarization OC of multichromatic pumps vary rapidly in time along the optical cycle. Thus, we propose new quantities, noninstantaneous polarization-associated OC, and time-scale-weighted polarization-associated OC, and show that these quantities link the chirality of multichromatic pumps and their generated attosecond pulses. The presented extension to OC theory should be useful for exploring various nonlinear chiral light-matter interactions. For example, it stimulates us to propose a tricircular pump for generation of highly elliptical attosecond pulses with a tunable ellipticity.
57 citations