Control of the spectral dependence of the output signal of a reflection interferometer with a noninverted instrumental function

The optical scheme of a simple resonator is transformed into a sequence of local interferometers. The phase length of a local interferometer is determined by the optical thickness of the thin-film dielectric coating on the surface of one of the mirrors. The spectral characteristic of the instrumental function is formed by parameter fitting. The experimental results are presented.     

A reflection interferometer with a noninverted response function based on a phase grating

It is shown that the inclusion of a simple phase grating in the optical scheme of a resonator provides the possibility of performing spectral investigations in reflected light with characteristics of a Fabry-Perot interferometer. The response function of the interferometer is examined, and experimental results are presented.     

Limiting instrumental function of the Fabry-Perot interferometer

Journal of Applied Spectroscopy -     

Fabry-Perot interferometer with diffraction-scattered reflection of light

The incorporation of a phase grating into the optical system of a Fabry-Perot interferometer makes it possible to transform the incident beam of light so that the major part of energy in the reflected wave is contained in the side lobes in the far-field diffraction pattern and radiation in the zero order of diffraction along the optical axis is suppressed. Experimental results are presented, which are obtained with a grating produced by evaporating a thin-layer dielectric coating onto the input mirror of the interferometer.     

Characteristics of a three-mirror interference system with a noninverted response function in reflected light

It is demonstrated that a reflection interferometer with optical properties of a three-mirror system in transmitted light can be created by including a phase grating in the structure of an input mirror. The response function is determined, a technique for the selection of parameters for the formation of spectral characteristics of the reflection coefficient is considered, and results of calculations are presented.     

Nonlocal Andreev reflection in a three-terminal Aharonov-Bohm interferometer

We theoretically report a nonlocal Andreev reflection in an Aharonov-Bohm interferometer, which is a three-terminal normal metal/superconductor (NS) mesoscopic hybrid system. It is found that this nonlocal Andreev reflection is sensitive to the systematic parameters, such as the bias voltages, the quantum dot levels, and the external magnetic flux. If we set the chemical potential of one normal metal lead equal to zero, the electronic current in the lead results from two competing processes: the quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero electronic current signals unambiguously the existence of this nonlocal Andreev reflection.     

Spin-dependent Andreev reflection in a three-terminal Aharonov-Bohm interferometer with coherent indirect coupling

Within the framework of non-equilibrium Green’s functions, we investigate the spin-dependent Andreev reflection (AR) in a three-terminal Aharonov-Bohm interferometer with double quantum dot, taking account of the coherent indirect coupling via the superconducting reservoir. It is found that the time-reversal symmetry is broken by the crossed Andreev reflection (CAR) process, and moreover that the spin-value effect of the linear conductance, the spin-polarised AR current, and a pure spin current can be generated by means of the normal AR and the CAR. Expressions for the AR conductances (the transport coefficients) governing the AR properties of this system are derived analytically. The effect of the coherent indirect coupling on the conductance, the Andreev reflected tunneling magnetoresistance (ARTMR), and the spin-related current in the presence of the AR are amply analyzed. Our results indicate that the optimal properties of this system can be realised by tuning the external parameters.     

Enhanced phase sensitivity with a nonconventional interferometer and nonlinear phase shifter

We propose a theoretical scheme of an enhanced phase sensitivity by introducing a nonlinear phase shifter to the nonconventional interferometer consisting of a balanced beam splitter (BBS) and an optical parameter amplifier (OPA), a modified nonlinear interferometer (MNI). Then we use coherent state and even coherent state as inputs and homodyne detection at one output port of the MNI for phase sensitivity, both without and with photon losses. We find that the nonlinear phase shifter can not only improve phase sensitivity, but also significantly resist the decoherence from photon losses. In comparison to both the BBS+OPA scheme with linear phase shifter and the traditional Mach–Zehnder interferometer with nonlinear one, the phase sensitivity of the MNI scheme shows the best performance. It is interesting that the nonlinear phase shifter can stimulate potential of the OPA, although there is no improvement in signal-to-noise ratio beyond standard quantum limit for the BBS+OPA scheme with a linear phase shifter.     

Ultimate sensitivity of heterodyne spectrometers

Low noise heterodyne receivers are now used in a large variety of instruments such as radiotelescopes, far infrared laser side bands spectrometers, supersonic nozzle beams Fourier transform spectrometers, lidars or plasmas diagnostics devices. Numerous papers have been devoted to the analysis of heterodyne receivers in the attempt to reach ultimate performances. These previous papers usually retain the restrictive hypothesis of vanishingly small signal powers. Such a condition occurs only in a restrictive number of applications, radioastronomic systems being probably among the most representative examples. Spectroscopic instruments operate usually in a different regime. The signal to be detected consists of a small variation in the source power. The absolute value of this source power largely depends on the available technology in the spectral range of interest. The purpose of this paper is to analyze the behavior of heterodyne detection in the general case. The results apply to a large category of systems including spectroscopic instruments. The influence of crucial parameters such as source power and predetection bandwidth is analysed in details. The theory is experimentally tested on an example of ultra low noise receiver designed for far infrared laser side bands spectroscopy. Some numerical calculations are proposed, illustrating methods for an optimal sizing of receiver's predetection bandwidth and the estimation of ultimate sensitivity of spectrometers.     

Dual-modulation fiber Fabry-Perot interferometer with double reflection for slowly-varying displacements

This Letter describes a dual-amplitude modulation technique incorporated into a double reflection extrinsic-type fiber Fabry-Perot interferometer to measure periodic, nonperiodic as well as quasi-static displacements. The modulation scheme simultaneously maintains the interference signal pair in quadrature and provides a reference signal for displacements inferior to a quarter of the source wavelength. The control and phase demodulation of the interferometer carried out via software enable quasi-real-time measurement and facilitates sensor alignment. The sensor system can be exploited in the low frequency range from 10(-3) to ～500 Hz and has a resolution better than 2.2 nm, targeting applications in geophysics.     

Quasiparticle interferometer controlled by quantum-correlated andreev reflection

We propose a quasiparticle interferometer for experimentally confirming the predicted phase interaction between a quasiparticle and a superconducting state at the superconductor- normal-metal (S-N) interface. The phase interaction is caused by Andreev reflection. The proposed interferometer consists of a Josephson junction and a Y-junction composed of normal electron waveguides. In the setup, the phase interaction due to Andreev reflection affects the resistance across the end of a waveguide and an electrode of the Josephson junction. Thus the amount of supercurrent flowing through the Josephson junction can control the resistance.     

高灵敏度色散型慢光干涉仪的仿真研究

设计了一种基于慢光介质色散特性的新型干涉装置,研究其物理过程,证明利用慢光介质可以有效提高干涉仪的光谱灵敏度,并且光谱灵敏度与慢光介质的群折射率成正比。同时,进一步具体分析慢光介质GaAs的色散特性,给出研究色散型慢光干涉仪的一般性方法,并证明使用慢光介质GaAs在近红外区域可以提高光谱灵敏度2倍左右。     

Nonlocal Andreev reflection and spin current in a three-terminal Aharonov--Bohm interferometer

This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov--Bohm interferometer. It is found that the electronic current and spin current are sensitive to systematic parameters, such as the gate voltage of quantum dots and the external magnetic flux. The electronic current in the normal metal lead results from two competing processes: quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero spin-up electronic current (or spin-down electronic current) signals the existence of nonlocal Andreev reflection, and the presence of zero electronic current results in the appearance of pure spin current.     

Negativity of Wigner function and phase sensitivity of an SU(1,1) interferometer

Both the negativity of Wigner function and the phase sensitivity of an SU(1,1) interferometer are investigated in this paper. In the case that the even coherent state and squeezed vacuum state are input into the interferometer, the Heisenberg limit can be approached with parity detection. At the same time, the negativity volume of Wigner function of detection mode comes entirely from the input state and varies periodically with the encoding phase. In addition, the negativity volume of Wigner function is positively correlated with the phase sensitivity of the SU(1,1) interferometer. The positive correlation may mean that the non-classicality indicated by negative Wigner function is a kind of resource that can verify some related research results of phase estimation.     

Double-grating interferometer with a one-to-one correspondence with a Michelson interferometer

We describe a double-grating interferometer that has a one-to-one correspondence with a Michelson interferometer. The half spatial periods of the gratings are equivalent to the wavelengths of the interferometer. The widths of the interference fringes can be changed easily. The intensity distribution of the interference pattern is independent of the wavelength of the light source used. The surface profile of an object can be measured because two interference beams can coincide precisely on the image plane of the object. The measuring range is much larger than that of a Michelson interferometer.     

Experimental intensity patterns obtained from a 2D shearing interferometer with adaptable sensitivity

The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques.