Study Of Extra Quantum Noise In Optical Detection And Optical Amplification

Optical detectors and optical amplifiers are two type of important quantum devices in modern scientific research,and the origin of their extra quantum noise is intrinsically connected to the principle of wave-particle duality in quantum physics.Due to their simpli-city in mathematical manipulations,the concept of single-mode field has been often used to deal with the problem of extra quantum noise in these devices.However,a“single-mode field”is neither a standard field?wave?nor a standard mode?particle?.According to the requirement by relativity,the commutator of any quantum field obeys the constraint of constant speed of light in relativity whereas the single-mode field does not.Thus,the concept of single-mode field inevitably faces some invincible difficulties in dealing with concrete physics problems for its shortcomings at the level of fundamental physics.In some recent researches,it has been pointed out that the concept of single-mode field is facing a theoretical dilemma in the quantum noise problem of phase-sensitive heterodyne detection.Due to the existence of image band vacuum mode?a single-mode field?,the heterodyne detector should suffer from extra quantum noise.However,as a phase-sensitive device,the heterodyne detector should be noise free according to the quantum theory of linear amplification.Similar cases also exist in the quantum-noise problem of optical amplifiers.In order to solve the these dilemma,the standard concept of quantum field has been used to study the noise characteristics in optical detection and optical amplification in this thesis.In the problem of extra quantum noise of optical detectors,we focus on the phase-sensitive heterodyne detection of two-mode squeezed state field.Though it is shown that the bichromatic-local-oscillator?BLO?phase-sensitive heterodyne detection of two mode squeezed states has 3 dB extra quantum noise by theoretical calculations based on the concept of single-mode field.According to the calculation based on the quantum theory of standard field and optical coherence,there is no extra quantum noise in the output photoelectric current created by a BLO phase-sensitive heterodyne detector.Also,we design and carry out an experiment to verify the validity of the two non-compatible results and no extra 3 dB quantum noise has been observed in the studied detector.This fact indicates that the quantum noise level of the BLO phase-sensitive heterodyne detector is the same as that of a monochromatic-local-oscillator phase-sensitive heterodyne detector,which approves the theoretical conclusion based on the standard quantum field.Moreover,only two types of amplifier can be predicted from the theory of linear amplifier based on the concept of single-mode field:phase-sensitive amplifier?PSA?and phase-insensitive amplifier?PIA?.However,by using the concept of quantum field,we discovered the exist of another type of amplifier,which is phase insensitive to the input signal while its output signal has a phase-sensitive noise.The quantum noise characteristic of this amplifier is beyond the theoretical scope that is based on the single-mode field.We calculate the amplifier?s quantum noise figure?NF?based on the concept of the standard quantum field,and the result shows that the value of its NF is 1?0 dB?.Thereafter an experiment has been designed and carried out to verify the theoretical results;the noise figure of the optical amplifier is 0.11_-:⁰_0.4.₇⁴² dB after considering the influence of beam mode mismatch and quantum efficiency,in agreement with theoretical calculation.Although the theory based on single-mode fields is successful in solving many problems in quantum optics,it still has many defects at the fundamental physics level,which leads to some unavoidable problems in the calculation of extra quantum noise in optical detection and amplification.In this thesis,the aforementioned problems are successfully solved by using the concept of standard quantum field and the theoretical conclusions are supported by experimental data.The origin of quantum noise in optical detection and optical amplification is more deeply understood through the study of this thesis.It is the quantum field of light,a continuum of infinite number of frequency modes,as a whole entity that gives rise to the quantum noise in optical detection.In contrast,a single-mode field is not an independent quantum field and contributes no observable quantum noise.Moreover,the related research results may find applications in the measurement of ultra-weak low-frequency optical signals,such as low-frequency gravitational wave detection.