Experimental validation of nonlinearity suppression for an inverse-layer-type silicon photodiode and its prediction based on theoretical modeling.

The spectral nonlinearity of an inverse-layer-type silicon (Si) photodiode (PD) in the visible region was investigated. As expected by theoretical calculation, supralinearity and saturation of the Si PD, which are key factors of nonlinearity, were suppressed by applying a reverse voltage above 30 V. Experimentally observed nonlinear behavior depending on the reverse bias was compared to a theoretical model describing supralinearity, including the inner parameters of the Si PD, and these comparison results were in agreement.

Titanium-based transition-edge photon number resolving detector with 98% detection efficiency with index-matched small-gap fiber coupling.

We have realized a high-detection-efficiency photon number resolving detector at an operating wavelength of about 850 nm. The detector consists of a titanium superconducting transition edge sensor in an optical cavity, which is directly coupled to an optical fiber using an approximately 300-nm gap. The gap reduces the sensitive area and heat capacity of the device, leading to high photon number resolution of 0.