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Second-harmonic generation (SHG, also called frequency doubling) is a nonlinear optical process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons (equivalently, twice the frequency and half the wavelength), that conserves the coherence of the excitation. It is a special case of sum-frequency generation (2 photons), and more generally of harmonic generation.
A waveguide is a structure that guides waves, such as sound (acoustic waveguide), light (optical waveguide), radio waves (radio-frequency waveguide) or other electromagnetic waves, with minimal loss of energy by restricting the transmission of energy to one direction. Without the physical constraint of a waveguide, wave intensities decrease according to the inverse square law as they expand into three-dimensional space. There are different types of waveguides for different types of waves.
An optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. Common types of optical waveguides include optical fiber waveguides, transparent dielectric waveguides made of plastic and glass, liquid light guides, and liquid waveguides. Optical waveguides are used as components in integrated optical circuits or as the transmission medium in local and long-haul optical communication systems.
We report the inscription of quasi-phase-matching gratings in silicon nitride waveguides for backward second-harmonic-generation enabled by all-optical poling, therefore, circumventing the difficultie
2022
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All-optical poling leads to an effective second-order nonlinearity (chi((2))) in centrosymmetric materials without the need for sophisticated fabrication techniques or material processing, through the
SPIE-INT SOC OPTICAL ENGINEERING2021
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The coherent photogalvanic effect leads to the generation of a current under the absorption interference of coherent beams and allows for the inscription of space-charge gratings leading to a second-o