Abstract
We use pump-probe spectroscopy and continuous wave cross-phase and cross-amplitude modulation measurements to study the optical nonlinearity of a hydrogenated amorphous silicon (a-Si:H) nanowire waveguide, and we compare the results to those of a crystalline silicon waveguide of similar dimensions. The a-Si:H nanowire shows essentially zero instantaneous two-photon absorption, but it displays a strong, long-lived non-instantaneous nonlinearity that is both absorptive and refractive. Power scaling measurements show that this non-instantaneous nonlinearity in a-Si:H scales as a third-order nonlinearity, and the refractive component possesses the opposite sign to that expected for free-carrier dispersion.
Highlights
Hydrogenated amorphous silicon (a-Si:H) is a promising material for optical processing in integrated silicon photonics
Films of a-Si:H can be deposited at low temperatures using plasma-enhanced chemical vapor deposition (PECVD), which means the material is back-end-of-the-line compatible with standard complementary-metaloxide-semiconductor (CMOS) fabrication techniques
We present a systematic study of the non-instantaneous nonlinearity of an aSi:H nanowire waveguide using several experimental techniques
Summary
Hydrogenated amorphous silicon (a-Si:H) is a promising material for optical processing in integrated silicon photonics. Over the past several years, many groups have studied the nonlinear properties of a-Si:H in waveguide geometries [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. The suitability of a waveguide for nonlinear optical processes is usually characterized by its nonlinear figure-of-merit (FOM), which is composed of the ratio of the real part to the imaginary part of its third-order nonlinear susceptibility [18]. We follow the convention FOM ≡ γR/ (4πγI), where γ is the waveguide’s complex nonlinear parameter given by γ
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