Electro-optic light modulation and THz generation in locally plasma-activated silicon nanophotonic devices

Matheisen, Christopher; Waldow, Michael; Chmielak, Bartos; Sawallich, Simon; Wahlbrink, T.; Bolten, Jens; Nagel, M.; Kurz, H.

doi:10.1364/oe.22.005252

Cited by 9 publications

(6 citation statements)

References 26 publications

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“…Further work [52] has shown that effective χ (2) increases with the reduction of the waveguide dimensions, which can also be explained by the increased mode penetration into the silicon nitride cladding. It was further shown in [53] that the nonlinearity can be activated by the formation of Si-Br bonds during an HBr dry etching process, and we predict a similar effect for SiN bonds. Finally, the fact that χ (2) has been observed in SiN waveguides that are naturally strained [19][20][21][22][23] also serves to confirm our explication.…”

Section: Discussionsupporting

confidence: 75%

On the origin of the second-order nonlinearity in strained Si–SiN structures

et al. 2015

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The development of efficient low-loss electro-optic and nonlinear components based on silicon or its related compounds, such as nitrides and oxides, is expected to dramatically enhance silicon photonics by eliminating the need for non-CMOS-compatible materials. While bulk Si is centrosymmetric and thus displays no second-order (χ (2) ) effects, a body of experimental evidence accumulated in the last decade demonstrates that when a strain gradient is present, a significant χ (2) and Pockels coefficient can be observed. In this work we connect a straingradient-induced χ (2) with another strain-gradient-induced phenomenon, the flexoelectric effect. We show that even in the presence of an extremely strong strain gradient, the degree by which a nonpolar material like Si can be altered cannot possibly explain the order of magnitude of observed χ (2) phenomena. At the same time, in a polar material like SiN, each bond has a large nonlinear polarizability, so when the inversion symmetry is broken by a strain gradient, a small (few degrees) re-orientation of bonds can engender χ (2) of the magnitude observed experimentally. It is our view therefore that the origin of the nonlinear and electro-optic effects in strained Si structures lies in not in the Si itself, but in the material providing the strain: the silicon nitride cladding.

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Section: Discussionsupporting

confidence: 75%

On the origin of the second-order nonlinearity in strained Si–SiN structures

et al. 2015

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“…The nonlinear susceptibility of graphene [4] is both strong-per atom it is orders of magnitude higher than that of common gapped semiconductors and metals-and controllable by the chemical potential [5,6], which can be tuned by an external gate voltage [7,8] or chemical doping [9]. With the possibilities it offers for integration in siliconbased optical integrated circuits, graphene is an exciting new candidate for enhancing nonlinear optical functionalities in silicon-based on-chip optical devices, such as on-chip broadband light sources, electro-optic modulators [10,11], optical switches [12][13][14], and optical transistors [15,16]. In realizing some of these devices [14], the presence of second-order optical nonlinearities, especially second harmonic generation (SHG), is a key requirement.…”

Section: Introductionmentioning

confidence: 99%

Third-order nonlinearity of graphene: Effects of phenomenological relaxation and finite temperature

2015

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We investigate the effect of phenomenological relaxation parameters on the third-order optical nonlinearity of doped graphene by perturbatively solving the semiconductor Bloch equation around the Dirac points. An analytic expression for the nonlinear conductivity at zero temperature is obtained under the linear dispersion approximation. With this analytic formula as a starting point, we construct the conductivity at finite temperature and study the optical response to a laser pulse of finite duration. We illustrate the dependence of several nonlinear optical effects, such as third harmonic generation, Kerr effects and two photon absorption, parametric frequency conversion, and two-color coherent current injection, on the relaxation parameters, temperature, and pulse duration. In the special case where one of the electric fields is taken as a dc field, we investigate the dc-currentand dc-field-induced second-order nonlinearities, including dc-current-induced second harmonic generation and difference frequency generation.

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“…In the development of integrated graphene-based photonic devices, the presence of a second order nonlinearity is important for realizing various essential building blocks, such as fast and compact electro-optic modulators [20,21], optical switches [22][23][24], and optical transistors [25,26]. In many of these device implementations the second-order process being exploited is second harmonic generation (SHG).…”

Section: Introductionmentioning

confidence: 99%

DC current induced second order optical nonlinearity in graphene

2014

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We calculate the dc current induced second harmonic generation in doped graphene using the semiconductor Bloch equations under relaxation time approximations. We find that the maximum value of the effective second order susceptibility appears when the fundamental photon energy matches the chemical potential. For a surface current density 1.1 × 10(3) A/m and a relaxation time at optical frequencies of 13 fs, the effective second order susceptibility χeff(2);xxx can be as large as 10(-7)m/V for h̄ω = 0.2 eV or 10(-8) m/V for h̄ω = 0.53 eV.

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Electro-optic light modulation and THz generation in locally plasma-activated silicon nanophotonic devices

Cited by 9 publications

References 26 publications

On the origin of the second-order nonlinearity in strained Si–SiN structures

On the origin of the second-order nonlinearity in strained Si–SiN structures

Third-order nonlinearity of graphene: Effects of phenomenological relaxation and finite temperature

DC current induced second order optical nonlinearity in graphene

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