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.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this article, the ellipticity dependence of harmonic generation in a thin layer of neon gas at an intensity of ${10}^{15}$ W/${\mathrm{cm}}^{2}$ and a wavelength of 7540 \AA{} was observed.
Abstract: We report observations of the ellipticity dependence of harmonic generation in a thin layer of neon gas at an intensity of ${10}^{15}$ W/${\mathrm{cm}}^{2}$ and a wavelength of 7540 \AA{} We observe a markedly different ellipticity dependence and polarization for harmonic energies below and above the ionization potential of neon (2156 eV) The ellipticity dependence of the higher harmonics can be understood in terms of free-bound transitions of ionizing electrons within the first cycle of the fundamental subsequent to tunnel ionization, while other mechanisms must be invoked to explain the characteristics of the lower harmonics
87 citations
TL;DR: In this article, the effects of laser beam quality and linewidth on the second-harmonic generation efficiency were investigated using a Yb-doped fiber laser, and a quasiphase matching in periodically poled Mgdoped stoichiometric lithium tantalate at room temperature was achieved.
Abstract: Single-pass second-harmonic generation of 7W continuous wave of 542nm radiation with 35.4% efficiency was achieved by quasiphase matching in periodically poled Mg-doped stoichiometric lithium tantalate at room temperature. The effects of laser beam quality and linewidth on the second-harmonic generation efficiency were investigated using a Yb-doped fiber laser.
87 citations
TL;DR: In this article, a tripling configuration was used in which the fundamental beam was incident upon the first of two KDP Type II crystals linearly polarized at an angle of tan−1 1/√2 to the ordinary direction.
87 citations
TL;DR: In this paper, the authors revisited the mechanism of high-harmonic generation from solids by comparing HHG in laser fields with different ellipticities but a constant maximum amplitude, and they showed that the cutoff of HHG is strongly extended in a circularly polarized field.
Abstract: We revisit the mechanism of high-harmonic generation (HHG) from solids by comparing HHG in laser fields with different ellipticities but a constant maximum amplitude. It is shown that the cutoff of HHG is strongly extended in a circularly polarized field. Moreover, the harmonic yield with large ellipticity is comparable to or even higher than that in the linearly polarized field. To understand the underlying physics, we develop a reciprocal-space-trajectory method, which explains HHG in solids by a trajectory ensemble from different ionization times and different initial states in the reciprocal space. We show that the cutoff extension is related to an additional preacceleration step prior to ionization, which has been overlooked in solids. By analyzing the trajectories and the time-frequency spectrogram, we show that the HHG in solids cannot be interpreted in terms of the classical recollision picture alone. Instead, the radiation should be described by the electron-hole interband polarization, which leads to the unusual ellipticity dependence. We propose a new four-step model to understand the mechanism of HHG in solids.
87 citations
TL;DR: In this article, the nonzero transition dipole phase (TDP) was shown to lead to the appearance of even harmonics in high-order harmonic spectra from solid materials driven by single-color multicycle laser fields.
Abstract: High-order harmonic spectra from solid materials driven by single-color multicycle laser fields sometimes contain even harmonics. In this work we attribute the appearance of even harmonics to the nonzero transition dipole phase (TDP) when the solid system has broken symmetry. By calculating the harmonic efficiency from graphene and gapped graphene by using the semiconductor Bloch equations under the tight-binding approximation, we demonstrate the role of the TDP, which has been ignored for a long time. When the crystal has inversion symmetry, or reflection symmetry with the symmetry plane perpendicular to the laser polarization direction, the TDP can be neglected. Without such symmetry, however, the TDP will lead to the appearance of even harmonics. We further show that the TDP is sensitive to the crystal geometry. To extract the structure information from the harmonic spectra of a solid the TDP cannot be ignored.
87 citations