Photoinduced generation of the second harmonic in centrosymmetric media

Dianov, Evgenii M; Starodubov, D.S.

doi:10.1070/qe1995v025n05abeh000371

Cited by 39 publications

(46 citation statements)

References 10 publications

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“…This third-order response at the second-harmonic frequency can be seen as an effective secondorder polarization based on an effective second-order nonlinearity, as given by [38] …”

Section: Discussionmentioning

confidence: 99%

“…This nonlinear DC current density possesses a spatial periodicity set by the wavenumber mismatch between the fundamental and second-harmonic fields (∆k = 2k(ω) − k(2ω)). The current density leads to a spatial redistribution of electrons between long-lived intra-band trap sites [38,39,44], which is the origin for generating an effective second-order nonlinearity. An equivalent picture is the creation of a nonlinear conduction via multi-photon excitation of electrons into the conduction band.…”

Section: Discussionmentioning

confidence: 99%

“…The temporal fit function was derived by Balakirev et al [33] for the CPGE in glass. The first observations of the CPGE in guided optics were made with phosphor-doped silica fibers [29,30,[36][37][38] and several phenomenological models were proposed [33,[39][40][41][42].…”

Section: Discussionmentioning

confidence: 99%

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Photo-induced second-order nonlinearity in stoichiometric silicon nitride waveguides

et al. 2017

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Abstract:We report the observation of second-harmonic generation (SHG) in stoichiometric silicon nitride waveguides grown via low-pressure chemical vapor deposition (LPCVD). Quasirectangular waveguides with a large cross section were used, with a height of 1 µm and various different widths, from 0.6 to 1.2 µm, and with various lengths from 22 to 74 mm. Using a mode-locked laser delivering 6-ps pulses at 1064 nm wavelength with a repetition rate of 20 MHz, 15% of the incoming power was coupled through the waveguide, making maximum average powers of up to 15 mW available in the waveguide depending on the waveguide cross section. Second-harmonic output was observed with a delay of minutes to several hours after the initial turn-on of pump radiation, showing a fast growth rate between 10 −4 to 10 −2 s −1 , with the shortest delay and highest growth rate at the highest input power. After this first, initial build-up (observed delay and growth), the second-harmonic became generated instantly with each new turn-on of the pump laser power. Phase matching was found to be present independent of the used waveguide width, although the latter changes the fundamental and second-harmonic phase velocities. We address the presence of a second-order nonlinearity and phase matching, involving an initial, power-dependent build-up, to the coherent photogalvanic effect. The effect, via the third-order nonlinearity and multiphoton absorption leads to a spatially patterned charge separation, which generates a spatially periodic, semi-permanent, DC-field-induced second-order susceptibility with a period that is appropriate for quasi-phase matching. The maximum measured second-harmonic conversion efficiency amounts to 0.4% in a waveguide with 0.9 × 1 µm 2 cross section and 36 mm length, corresponding to 53 µW at 532 nm with 13 mW of IR input coupled into the waveguide. The maximum equivalent χ (2) -susceptibility amounts to 3.7 pm/V, as retrieved from the measured conversion efficiency.

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“…This third-order response at the second-harmonic frequency can be seen as an effective secondorder polarization based on an effective second-order nonlinearity, as given by [38] …”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Photo-induced second-order nonlinearity in stoichiometric silicon nitride waveguides

et al. 2017

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“…A reversible spatially periodic change of the optical anisotropy was produced in glass by two focused mutually coherent beams at the fundamental (U)) and doubled (2a) frequencies of a pulsed YAG:Nd3 laser ( 2=l,O8m ).This change is accompanied by a modulation of refractive index ( An-gratings ) and an appearing of the second-order polarizability ( 2,6 The angle between the axes of the beams was chosen so that the Bragg diffraction condition on the photoinduced index grating would be satisfied for the beam at the fundamental frequency. In so doing, the fundamental beam diffracted effectively on the An-grating.…”

Section: Parametric Amplification Of the Subharmonic In Photoinduced mentioning

confidence: 99%

“…The feature of the hotoinduced is its sign-changing periodic change in space.The half-period of is equal to the coherence length of waves which had engendered this grating. Such circumstances was used widely for effective photoinduced second harmonic generation ( PSHG ) in waveguides 2,6 Other possible phenomenon, the amplification of subharinonic of light in glass with photoinduced anisotropy, was not still investigated.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced amplification of a subharmonic of light and photoelectric instability in glass

1999

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Generalized Coherent Photogalvanic Effect in Coherently Seeded Waveguides

Yakar

Nitišs

et al. 2022

Laser & Photonics Reviews

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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‐order susceptibility (χ(2)). The inscribed grating automatically results in quasi‐phase‐matching between the interfering beams. Theoretical and experimental studies, considering the degenerate case of second‐harmonic generation, show significant conversion efficiency enhancements. However, the link between the theory and experiment is not fully established such that general guidelines and achievable conversion efficiency for a given material platform are still unclear. In this work, the phenomenological model of coherent photogalvanic effect in optical waveguides is theoretically analyzed. This model predicts the existence of non‐degenerate sum‐frequency generation quasi‐phase‐matching gratings, which is confirmed experimentally for the first time. Furthermore, the time dynamics of the space‐charge grating inscription in coherent photogalvanic process is formulated. Based on the developed theoretical equations, the material parameters governing the process for stoichiometric silicon nitride are extracted. The results obtained provide a basis to compare the performances and potentials of different platforms. This work not only supplements the theory of coherent photogalvanic effect, but also enables us to identify critical parameters and limiting factors for the inscription of χ(2) gratings.

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Photoinduced generation of the second harmonic in centrosymmetric media

Cited by 39 publications

References 10 publications

Photo-induced second-order nonlinearity in stoichiometric silicon nitride waveguides

Photo-induced second-order nonlinearity in stoichiometric silicon nitride waveguides

Photoinduced amplification of a subharmonic of light and photoelectric instability in glass

Generalized Coherent Photogalvanic Effect in Coherently Seeded Waveguides

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