Second optical harmonic generation by a layered plasmon nanoparticle

The features of second harmonic generation by a spherical nanoparticle with a plasmon shell are theoretically studied. In the framework of the quasistatic perturbation theory, expressions for the oscillating at a doubled frequency induced dipole and quadrupole moments of a particle were obtained. The second harmonic radiation power was calculated, which showed the resonance nature of the dependence of power on the exciting wavelength. Moreover, the positions of the radiation power resonances significantly depend on the dielectric permittivity of the particle core and its size.

Получение терагерцового излучения в кристаллах InP : Fe за счет решеточной нелинейности второго порядка

In this paper, we experimentally demonstrate the generation of the second harmonic radiation of the gyrotron with an operating frequency of 263 GHz due to the second order lattice nonlinearity in indium phosphide crystals doped with ferrum. It is shown that the second harmonic radiation can be used for magnetospectroscopy of semiconductor nanostructures. We discuss the possibility of generating a difference frequency in these crystals when excited by two sources of the mid-IR range with a close wavelength.

Multipolar second-harmonic generation from high-Q quasi-BIC states in subwavelength resonators

We put forward the multipolar model which captures the physics behind linear and nonlinear response driven by high-quality (high-Q) supercavity modes in subwavelength particles. We show that the formation of such trapped states associated with bound states in the continuum (quasi-BIC) can be understood through multipolar transformations of coupled leaky modes. The quasi-BIC state appears with increasing the order of the dominating multipole, where dipolar losses are completely suppressed. The efficient optical coupling to this state in the AlGaAs nanodisk is implemented via azimuthally polarized beam illumination matching its multipolar origin. We establish a one-to-one correspondence between the standard phenomenological non-Hermitian coupled-mode theory and multipolar models. The derived multipolar composition of the generated second-harmonic radiation from the AlGaAs nanodisk is then validated with full-wave numerical simulations. Back-action of the second-harmonic radiation onto the fundamental frequency is taken into account in the coupled nonlinear model with pump depletion. A hybrid metal-dielectric nanoantenna is proposed to augment the conversion efficiency up to tens of per cent due to increasing quality factors of the involved resonant states. Our findings delineate novel promising strategies in the design of functional elements for nonlinear nanophotonics applications.

Генерация второй гармоники от тонкого цилиндрического слоя. III. Условия отсутствия генерации

More than 50 different combinations are given for parameters of the problem of second harmonic generation by a plane electromagnetic elliptically polarized wave from a thin optical layer on the surface of cylindrical particle, in which the generation from the lateral surface cannot be observed. Also, 18 combinations of parameters are found, in which generation from the end surfaces of the cylindrical particle is not observed. More than 30 problem parameter combinations are given, in which linearly polarized second harmonic radiation is generated from the side surface (or from the end surfaces). The combinations of problem parameters are indicated, at which generation from the entire surface of the cylindrical particle cannot be observed, and also parameter combinations at which the generation has linear polarization. A method is proposed for determining the anisotropy coefficients on the base of the properties above.

Получение второй гармоники излучения субтерагерцовых гиротронов при удвоении частоты в InP : Fe и ее использование для магнитоспектроскопии полупроводниковых структур

The possibility of obtaining intense terahertz radiation due to second-order lattice nonlinearity in indium-phosphide crystals doped with iron is discussed. As a source of radiation, subterahertz gyrotrons are considered. It is shown that the efficiency of frequency doubling can reach 3%, which opens up the possibility for developing a new generation of terahertz radiation sources. The possibility of applying second-harmonic radiation for the magnetospectroscopy of semiconductor structures with quasi-Dirac dispersion is demonstrated.

Boosting Second Harmonic Radiation from AlGaAs Nanoantennas with Epsilon-Near-Zero Materials

Enhancing the second harmonic conversion efficiency at the nanoscale is a critical challenge in nonlinear optics. Here we propose the use of epsilon-near-zero materials to boost the nonlinear radiation in the far field. Here, a comparison of the second harmonic behavior of a cylindrical AlGaAs nanoantenna placed over different semi-infinite layers is presented. In particular, we observed that the second harmonic generation is strongly enhanced and redirected by the simultaneous presence of a resonance at the fundamental wavelength and a low-permittivity condition in the substrate at the harmonic wavelength. Our results pave the way for a novel approach to enhance optical nonlinearities at the nanoscale.

Highly-Efficient Longitudinal Second-Harmonic Generation from Doubly-Resonant AlGaAs Nanoantennas

We design an asymmetric nonlinear optical nanoantenna composed of a dielectric nanodisc and an adjacent nanobar. The proposed composite structure made of AlGaAs exhibits resonant response at both the fundamental and doubled frequencies. Being driven by the strong magnetic dipole resonance at the pump wavelength and a high-quality mode at the harmonic wavelength, the efficient second-harmonic radiation is generated predominantly along the vertical directions under the normally incident plane-wave excitation.

Highly-efficient longitudinal second-harmonic generation from doubly-resonant AlGaAs nanoantennas

We design an asymmetric nonlinear optical nanoantenna composed of a dielectric nanodisk and an adjacent nanobar. The proposed composite structure made of AlGaAs exhibits resonant response at both the fundamental and doubled frequencies. Being driven by the strong magnetic dipole resonance at the pump wavelength and a high-quality mode at the harmonic wavelength, the efficient second-harmonic radiation is generated predominantly along the vertical directions under the normally incident plane-wave excitation.