Electrically Tunable Optical Nonlinearities in Graphene-Covered SiN Waveguides Characterized by Four-Wave Mixing

Abstract

We present a degenerate four-wave mixing experiment on a silicon nitride (SiN) waveguide covered with gated graphene. We observe strong dependencies on signal-pump detuning and Fermi energy, i.e. the optical nonlinearity is demonstrated to be electrically tunable. In the vicinity of the interband absorption edge (2|EF | ≈ ω) a peak value of the waveguide nonlinear parameter of ≈ 6400 m −1 W −1 , corresponding to a graphene nonlinear sheet conductivity |σ

Enhanced optical Kerr effect method for a detailed characterization of the third-order nonlinearity of two-dimensional materials applied to graphene

“…Graphene deposited on glass or silicon substrates is low pdoped, as shown, for example, in Ref. 15, where the chemical potential is evaluated between -0.3 eV and -0.2 eV. At those doping levels and the wavelength used in our experiments (1600 nm, orhω ≈ 0.8 eV) the nonlinear conductivity in Ref.…”

“…The thirdorder nonlinear optical response of graphene has been investigated by many groups, theoretically [2][3][4][5][6][7][8] , and experimentally [9][10][11][12][13][14][15] . More recently, other 2D materials have also been studied 16,17 .…”

Evaluation of graphene optical nonlinearity with photon-pair generation in graphene-on-silicon waveguides

“…Note that, in this work, we use the effective nonlinear refractive index n 2,eff for convenience to compare our results with the various previous works although the conventional nonlinear refractive index n 2 for three-dimensional materials cannot be defined for two-dimensional materials, as discussed in several theoretical papers [28,29,46]. As with the recent experimental works [13,31], the use of the two-dimensional nonlinear conductivity (or the two-dimensional nonlinear susceptibility defined in [46]) would be appropriate for future work. Figure 4(a) shows the net photon-pair generation rate at the output end of the GSWs as a function of pump peak power P p with the fixed graphene length L gr of 100 µm and the graphene position of (iii) fixed input-length II (L in = 0.15 mm).…”

Comment on “Graphene—A rather ordinary nonlinear optical material” [Appl. Phys. Lett. 104, 161116 (2014)]

“…5 The required electric field is then about three orders of magnitude smaller than the estimate $10 MV/cm obtained in Ref. 2.…”