Very high sensitivity electrically modulated Si-photodiode in photovoltaic-mode as phase-sensitive detector of light power

In this work we propose a new approach based on the electrical self-modulation of Si-photodiode (Si-PD) operating in photovoltaic mode as a high-sensitivity phase detector of light power variations. This novel technique shows much better performances with respect to the conventional amplitude measurement of light power employing lock-in amplifier technique. In particular, our solution allows to detect phase variations, between a reference signal and that one generated by the Si-PD as a function of the light impinging on it, by performing an electrical modulation through an AC excitation signal, without a DC reverse biasing. In this way, the optoelectronic apparatus is notably simplified making the system suitable for portable sensor applications. Experimental results demonstrate a very high settable sensitivity of phase variations, with respect to light power changes as a function of Si-PD operating conditions, reaching values up to 255 degree/μW.