Feedback-measurement–induced anticorrelation between in-loop photocurrent fluctuation and amplifier dark noise

¹ Laboratory for Quantum Optics, Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences - Shanghai 201800, P. R. China
² Department of Physics, Suzhou University - Suzhou, Jiangsu 215006, P. R. China
³ Department of Physics, Florida International University - Miami, Florida 33199, USA
⁴ Department of Electronics, Peking University - Beijing 100871, P. R. China

Received: 8 August 1999
Accepted: 22 November 1999

Abstract

Suppression of in-loop photocurrent fluctuation below the amplifier dark noise was observed in both a negative-feedback light-emitting diode (LED) and a laser diode (LD). We use a new semiclassical model to analyze the squeezed mechanism of the in-loop photocurrent noise mentioned above and find that there is a feedback-measurement–induced anticorrelation effect between the measured photocurrent fluctuation and the amplifier dark noise, which results in the suppression of the in-loop photocurrent fluctuation below the amplifier dark noise. Our theoretical analysis gives the correlation coefficient between the photocurrent fluctuation and amplifier noise, and also yields the squeezed spectrum of the in-loop intensity fluctuation according to our experimental results.