Detection of weak optical signals

Changchang Zhang, Zhaolu Wang, Wenjuan Shi +4 more

Yin Zhang, Guowei Li, Junbo Wang +1 more

Spectral analysis technology in optical signal detection can obtain the spectral characteristics of matter according to the wavelength or frequency information of the optical signal. Commonly used spectral analysis techniques include grating spectrometer, Fourier transform infrared spectrometer (FTIR), Raman spectrometer, etc. In order to improve the measurement of optical signal, due to the limitation of detector detection bandwidth and system noise and external interference, this paper proposes an optical signal estimation scheme based on weak measurement method. Moreover, compared with the original weak measurement scheme, the detection time of the new scheme proposed in this paper breaks through the limitation of Nyquist sampling theorem, has the performance advantage of resisting aliasing interference, and can effectively improve the signal-to-noise ratio of the system by extending the detection time. This paper presents a new weak measurement theory scheme for optical signals. Theoretical research studies show that the scheme can estimate the amplitude and phase of the optical signal and recover the time domain by setting the dynamic phase factor with time for the previous or post-selection process. Because the detection time of the scheme is not limited by the Nyquist sampling theorem, the new scheme has the performance advantage of anti-aliasing interference, which effectively solves the limitation of the detector detection bandwidth in the original scheme.

Vladimir P Bykov

Detection of light is one of the most fundamental physical processes playing a very important role in both nature and technology. In nature, this process underlies vision, thus providing an opportunity to perceive the world around us. Numerous photodetectors in technology allow the quantification of the detection of optical signals, expanding the spectrum of detected radiation. The problem of detecting optical signals by optical methods themselves was first formulated apparently by Bloembergen [1]. However, this idea has not been adequately developed. In paper [2] it was shown that the signal-to-noise ratio could be improved by using nonlinear radiation detectors in which the signal transformation begins from an absorption transition. It was shown in papers [3] that photocounts appear in conventional photodetectors due to the strong Coulomb instability of a weak electron current produced in the detector by a signal being detected. This suggests that in detectors, instead of free electrons, the electrons that are bound in atoms, ions, or molecules can be used, where they are well stabilized by a strong Coulomb field of nuclei. Below a possible scheme for detecting weak optical signals by laser means is described. At present microcavities are created which can be used in the Bloembergen scheme, providing the passage from spontaneous to stimulated effect, thereby substantially improving the scheme.

Kumar

Frank Schlawin

A. Asghari Nejad, Hassan Randjbar Askari, Hamid Reza Baghshahi

Entanglement between optical fields and microwave signals can be used as a quantum optical sensing technique to detect received microwave signals from a low-reflecting object which is encompassed by a bright thermal environment. Here, we introduce and analyze an optomechanical system for detecting weak reflected microwave signals from an object of low reflectivity. In our system, coupling and consequently entanglement between microwave and optical photons are achieved by means of a plasmonic wave. The main problem that can be moderated in the field of quantum optical sensing of weak microwave signals is suppressing the destructive effect of high temperatures on the entanglement between microwave signals and optical photons. For this purpose, we will show that our system can perform at high temperatures as well as low ones. It will be shown that the presence of the plasmonic wave can reduce the destructive effect of the thermal noises on the entanglement between microwave and optical photons. Also, we will show that the optomechanical interaction is vital to create an appropriate entanglement between microwave and optical photons.