A 111-Cut Si Hemisphere Two-Photon Response Photodetector

Properties of two-photon response in a 111-cut nearly-intrinsic Si hemisphere photodetector are studied. The measured photocurrent of the photodetector responding to the 1.32 µm continuous wave laser shows a quadratic dependence on the coupled optical power and is saturated with the bias voltage. Also, the photocurrent is independent of polarization. Such properties are in good agreement with the theory of two−photon absorption. The isotropic photocurrent generated from the 111-cut Si hemisphere is compared to the anisotropic one induced in the 110-cut Si sample and the ratio of χ_xxxx /χ_xxyy for silicon performing at 1.32 µm is calculated to be 2.4 via the fitted function of the anisotropic photocurrent from the 110-cut sample.