Laser phase relative

There are two ways to collect FLIM data freqnency-domain or time-domain data acqnisition (Alcala et al. 1985 Jameson et al. 1984). Briefly, in freqnency domain FLIM, the fluorescence lifetime is determined by its different phase relative to a freqnency modulated excitation signal nsing a fast Fourier transform algorithm. This method requires a frequency synthesizer phase-locked to the repetition freqnency of the laser to drive an RF power amplifier that modulates the amplification of the detector photomultiplier at the master frequency plus an additional cross-correlation freqnency. In contrast, time-domain FLIM directly measures t using a photon connting PMT and card. 

In these WMS signals, the wavelength crosses the water absorption feature twice for each modulation cycle. Therefore, when water vapor is in the optical path, the amplitude modulation of the received laser power contains a periodic component having precisely twice the wavelength modulation frequency and fixed in phase relative to the wavelength modulation. 

Refractive index detector (RID) 1 x 10 7g 1 x 104 Universal, dependent on refractive index difference with mobile phase Relatively insensitive to flow fluctuations, but sensitive to temperature fluctuations nondestructive, cannot be used with gradient elution solvents must be degassed to avoid bubble formations laser-based Rl detectors offer higher sensitivity... 

Since partial laser phase coherence affects both the direct terms as well as the cross terms, the extent of control is dependent on the laser properties through the relative magnitudes of ( l( ulg) (c02g))l and (l i-(w ) 2)> =1,2. To expose the dependence on the coherence of the pump field denote the terms ckc jF u>jk)dq kj)(E) by a ]- and consider the ratio of the k / j term in Eq. (5.44) to the associated diagonal terms. That is, consider the contrast ratio ... 

A more complex analysis of the effect of laser phase diffusion has been appli fS the case of one-photon vs. three-photon absoiption (i.e., simultaneous absorption 3a)j and third-harmonic generation frqnt>t coi laser. As discussed in Section 3.3.2, current experiments vary the relative ph of two laser beams by passing co3 and co, through a gas. If the laser frequcnc somewhat unstable, then the relative phase of the two beams will acquire a fhtct y ing phase that is a source of phase loss in the system. The phase fluctuations q ... 

The role of the laser phase in controlling molecular dynamics was clear in the examples shown in Chapter 3, For example, in the one- vs. three-photon scenario the relative laser phase (3 — 3c/>,) enters directly into the interference term [see, e.g., Eq. (3.53)], as does the relative phase ((frl — (j>2) in the bichromatic control scenario [Eq. (3.19)]. These residts embody two useful general rules about the contribution of the laser phase to coherent control scenarios. The first is that the interference term contains the difference between the laser phase imparted to the molecule by one route, and that imparted to the molecule by an alternate route. Second, the phase imparted to the state Em) by a light field of the form ... 

The ratio Rqq, depends on a number of laboratory control parameters including f he relative laser intensities x, relative laser phase, and the ratio of e+1 and e via t. ... 

Figure 6.3 Contours of equal Na(3p) yield. Ordinate is the relative laser phase and abscissa y is the field intensity ratio x. Here for X0 = 623.367 nm, X+ = 603.491 nm, X = 644.596nm,. and t] = 1. (From Fig. 1, Ref. [206].) V...

Figure 6.8 Dependence of the real part of n(a>) on F2/l in N2 (in the superposition state described in the text) for different values of relative laser phase dtp. Here dtp = —njl (solid), dtp = 0 and n (dashed), and dtp = n/2 (dot-dash). (From Fig. 1, Ref. [213], where dtp was i " denoted S.)...

In order to produce surface-relief electro-optic gratings, Munakata et compared two fabrication methods of SRG inscription. In the first, the SRG was produced with an interference pattern of cw laser, with relatively modest intensities. The gratings so recorded were photo- and thermally erasable, and efficient writing was polarization dependent. In the second method, a phase mask was employed to provide the periodic intensity modulation of a pulsed laser, the 3rd-order harmonic (at 355 nm) of a Nd YAG laser. The SRG was produced with a single laser pulse, allowing a very short fabrication time (less than Is). The direshold for ablation was 500 mj/(em pulse), and the amplitude of the SRG increased with pulse energy. A depth of up to 300 rim could be achieved, leading to a smooth but not sinusoidal surface modulation. 

Conventional transmission absorption and CD spectra of the samples are given in Figures 6-8, where the positions of the laser lines relative to the absorption and CD bands are shown. Experimental data (for the compounds used) are given in Tables 1-5. Included in the tables are PAS magnitudes (Q), PACD values (aQ), photoacoustically determined g values (9pa) and the phases of the aQ signals (). Also included for comparison are the transmissions, Ae, and g values. 

Phase analysis light scattering (PALS) is a technique that is very similar to laser Doppler electrophoresis (LDE) and is used to measure the electrophoretic mobilities of colloidal particles. This technique is particularly suited to measurements of charged particles suspended in nonpolar media and sensitivity of the method is far superior to that which could be obtained by LDE measurements. It makes use of a cross-beam technique and offsets one of the laser beams relative to the other by several kEIz. ... 

The first example is a three-level A-type system coupled by bichromatic coupling and probe fields, which opens two Raman transition channels [60]. The phase dependent interference between the resonant two-photon Raman transitions depends on the relative phases of the laser fields either constructive interference or destructive interference between the two Raman channels can be obtained by controlling the laser phases. The second example is a four-level system coupled by two coupling fields and two probe fields, in which a double-ElT configuration is created by the phase-dependent interference between the three-photon and one-photon excitation processes, or equivalently two independent Raman transition channels [58,62]. We will provide theoretical analyses of the phase dependent quantum interference in the two multi-level atomic systems and present experimental results obtained with cold Rb atoms. The two systems provide basic platforms to study coherent atom-photon interactions and quantum state manipulations, and to explore useful applications of the phase-dependent interference in the multi-level atomic systems. 

A connnon teclmique used to enliance the signal-to-noise ratio for weak modes is to inject a local oscillator field polarized parallel to the RIKE field at the detector. This local oscillator field is derived from the probe laser and will add coherently to the RIKE field [96]. The relative phase of the local oscillator and the RIKE field is an important parameter in describing the optical heterodyne detected (OHD)-RIKES spectrum. If the local oscillator at the detector is in phase with the probe wave, the heterodyne mtensity is proportional to... 

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