Homodyne detection

Since optical fields oscillate too quickly for direct detection, they are measured in quadrahire —as photons (see below). There are two ways to achieve quadrahire. One is homodyne detection in which the new field is measured at... 

Returning to the original pump-probe RRS, it is a simple matter to complete the 4WM WMEL diagrams for any proposed RRS. Usually RRS experiments are of the frill quadrature sort, both spontaneous RRS as well as homodyne detected femtosecond RRS. The latter fit most pump-probe configurations. 

Clip acts in phase (the same Fourier component) with the first action of cii to produce a polarization that is anti-Stokes shifted from oi (see fV (E) and IFj (F) of figure B 1.3.2(b)). For the case of CSRS the third field action has frequency CO2 and acts in phase with the earlier action of CO2 (W (C) and IFj (D) of figure Bl.3.2 (b). Unlike the Class I spectroscopies, no fields in CARS or CSRS (or any homodyne detected Class II spectroscopies) are in quadrature at the polarization level. Since homodyne detected CRS is governed by the modulus square of hs lineshape is not a synmretric lineshape like those in the Class I... 

For homodyne detection, the TR-CRS intensity (for Lorentzian Raman lines) is of the fomi [115]... 

In frequency-domain FLIM, the optics and detection system (MCP image intensifier and slow scan CCD camera) are similar to that of time-domain FLIM, except for the light source, which consists of a CW laser and an acousto-optical modulator instead of a pulsed laser. The principle of lifetime measurement is the same as that described in Chapter 6 (Section 6.2.3.1). The phase shift and modulation depth are measured relative to a known fluorescence standard or to scattering of the excitation light. There are two possible modes of detection heterodyne and homodyne detection. 

In the simplest (homodyne) detection scheme one measures the time-integrated intensity of the field generated by the sample in a given direction ky ... 

One excellent way to increase the S/N ratio is to tune the detector to the exact same frequency v as the source (using a lock-in amplifier, also known as a phase-sensitive detector or as homodyne detection) and also to discriminate the phase

rc/2 or (3/2)n. This can be used to discriminate up to 60 dB. 

In a homodyne detection scheme, such as in the stimulated photon echo experiments described in the next paragraph, the detector measures the t-integrated intensity of the square of the third-order polarization... 

In the experimental section of this chapter we will present spectra obtained using both homodyne and heterodyne detection methods. The total homodyne detected signal is expressed as... 

The expressions that can be used in the analysis of the measured autocorrelation response C(r) are given below for the case of heterodyne and homodyne detection. Homodyne detection applies to the case where the interface does not contribute to the scattering. Heterodyne detection applies to cases where the interface itself contributes significantly to the scattering (perhaps due to roughness). 

Re F stands for the real part of the function F. The function fcs(r) models a slowly varying background, which is usually present in all of the measurements. The constant background term B is measured by the autocorrelator using special time bins with extra delay. / () is the intensity of the local oscillator (may represent scattering due to the interface itself) the term 2/S0// 0 indicates the relative amount of particle-scattered light and reference scattered photons and should not exceed 0.1 for heterodyne detection. The quantity / is an instrumental constant, a value around 0.5 indicating a reasonably optimized system for homodyne detection. 

The analysis methods in Fig. 3 can be used to fit scattering data in the form of G,2). (21, or (l 1 ACFs. Each of these forms has advantages and disadvantages with respect to data analysis. Most DLS experiments employ homodyne detection and therefore measure G(2) = A (2). We can fit homodyne C(2) data with a functional form derived from a combination of Eqs. (26) and (46) ... 

Other applications that were recently demonstrated with photorefractive polymers include homodyne detection of ultrasonic surface displacements using two-wave mixing [115]. With the development of new photorefractive polymers with response times in the millisecond range, numerous optical processing techniques can be performed at video rates. Image amplification and novelty filtering at video rates were demonstrated recently [116]. All-optical processing techniques compete with computational methods. Therefore, it is important that photorefractive polymers exhibit faster response times in the future. 

First, let us show that the operational phase concepts can naturally be embedded in the general scheme of quantum estimation theory [66,67] as was done by Hradil, Zawisky, and others [68-71]. Let us consider the eight port homodyne detection scheme [63,72] with four output channels numbered by indices 3,4,5,6, where the actual values of intensities are registered in each run. Assume that these values fluctuate in accordance with some statistics. The mean intensities are modulated by a phase parameter 0... 

The squeezing mode experiments were carried out using the homodyne detection scheme with scattering angles within 20° of either the reflected beam ( q=60°) or the transmitted beam. A small region of 4° around either the transmitted or reflected beam was excluded because here a gradual, but not exactly reproducible, transition from homodyne to heterodyne detection is observed. 

The assumption that y/ is a Gaussian random variable leads to the prediction that If can be obtained from If. Homodyne detection then gives precisely the same information as heterodyne detection. 

A.B. Thompson, E.M. Sevick-Muracka, Near-infrared fluorescence contrast-enhanced imaging with intensified charge-coupled device homodyne detection measurement precision and accuracy, J. Biomed. Opt. 8, 111-120 (2003)... 

The variation of the translational diffusion coefficient measured at 20°C by homodyne detection at angles from 5 to 40 of ChSO -Na when the ionic strength is... 

The autocorrelation function C(t) is the product of the intensity at a given time and a delayed value of the intensity averaged as a function of delay time (r). For monodisperse particle systems in homodyne detection mode (heterodyne spectroscopy allows detection of light at much lower intensities than homodyne), C(t) is a single decaying exponential defined as ... 

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