A comparative analysis between the fundamental and second cyclotron harmonics of gyrotron backward-wave oscillators (gyro-BWOs) is presented. The simulation results reveal that nonlinear field contraction is a common feature for both harmonic interactions. Besides, the electron transit angle, used to characterize the axial modes of the fundamental harmonic TE11 mode at the start-oscillation con...

We study the effective second-harmonic generation (SHG) susceptibility in graded metallic films by invoking the local field effects exactly and further numerically demonstrate that graded metallic films can serve as a novel optical material for producing a broad structure in both the linear and the SHG response and an enhancement in the SHG signal.

Second harmonic generation (SHG) has been developed in our laboratories as a high-resolution nonlinear optical imaging microscopy for cellular membranes and intact tissues. SHG shares many of the advantageous features for microscopy of another more established nonlinear optical technique: two-photon excited fluorescence (TPEF). Both are capable of optical sectioning to produce three-dimensional...

In this work, we study theoretically the operation of long surface acoustic wave reflectors, comprising a large number of electrodes, at the fundamental and second harmonic frequencies on the 128 LiNbO3 substrate for various electrode thicknesses and metallization ratios. Numerical simulations utilizing tailored test structures and time gating indicate that the reflectivity of the second-harmon...

Fabio Antonio Bovino1, Maria Cristina Larciprete2, Concita Sibilia2 Maurizio Giardina1, G. Váró3 and C. Gergely4 1Quantum Optics Lab Selex-Sistemi Integrati, Genova, Italy 2Department of Basic and Applied Sciences in Engineering, Sapienza University, Rome, 3Institute of Biophysics, Biological Research Center, Hungarian Academy of Sciences, Szeged, 4Montpellier University, Charles Coulomb Labora...

The mid-infrared spectral region can be covered by quantum cascade (QC) semiconductor lasers, where the emission wavelength is tailored by bandstructure engineering. For a detailed review on QC lasers see Ref. [1]. Their emission energy is well below the band gaps of the hosting material system. Typical GaAs QC lasers operate in the mid-infrared regime with corresponding energies of ~100 meV, w...

We present a new type of soliton, found in models characterized by opposing dispersions and competing nonlinearities at fundamental and second harmonics. They are isolated solitary waves, existing at discrete values of the propagation constant inside the system’s continuous spectrum. We show analytically, and verify by simulations, that the fundamental solitons are linearly stable. They can be ...

Chiral spectroscopic study: The intensities of second harmonic generation chiral spectroscopy are obtained from the dispersion of the nonlinear optical susceptibility components, as a function of wavelength for helicenbisquinone thin films (see figure). A single formalism fits all the data simultaneously, and the findings constitute an important milestone towards the development of a new experi...

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