Beam profile rectangular

Note, however, that this is only true for 1 and infinitely extended plane waves, where the different reflected partial waves completely overlap. If the incident wave is a laser beam with the finite diameter D, the different reflected partial beams do not completely overlap because they are laterally shifted hy A = b cos a with b = 2d tan p (Fig. 4.42). For a rectangular intensity profile of the laser beam, the fraction A/D of the reflected partial amplitudes does not overlap and cannot interfere destructively. This means that, even for maximum transmission, the reflected intensity is not zero but a background reflection remains, which is missing in the transmitted light. For small angles O, one obtains for the intensity loss per transit due to reflection [4.36] for a rectangular beam profile... 

Grewell et al [4] applied their 2-D qirasi-steady-state model to laser transmission micro-welduig of plastics. The specimens were assttmed to be semi-infinite with temperature-independent properties. In their earlier studies, Mayboudi et al [5] developed a 2-D thermal model for LTW of urrfiUed PA6 in T-like joint geometry. Their model assumed heat conduction in the direction along the beam travel was negligible and assumed a simplified representation of the laser beam profile as rectangular in... 

Examples are given of the use of extruded PE foam sections in conjunction with other polymeric materials in the production of triangular, semicircular, rectangular and trapezoidal profiles, e.g. beam-like structures in which the rigid support may be of GRP. The foam can be bonded with thermally-fusible adhesives or two-sided self adhesive tape affixed to the foam prior to fabricating. A standard range of the foam prodncts is available, but other types can be tailor-made. 

Fig. 3.20. Signals of fluorescence kinetics representing fly-through relaxation of an optically depopulated initial level (a) rectangular profile of the beam (b) limited Gaussian profile (c) unlimited Gaussian profile (d) experimentally registered signal. Values of the non-linearity parameter Bwpvp/ro are shown in brackets.

Kerth et al. (214) reported excimer laser (308 nm) projection lithography obtained with a modified full-field scanning projection system (Perkin-Elmer M500). The modifications included an anamorphic optical system for transforming the nearly collimated rectangular excimer laser beam into the arc shape. They obtained images of l- xm lines with nearly vertical (85 ) wall profiles. 

Naturally, this function corresponds to a rectangular profile centered on the beam s axis, the width of this rectangle being equal to the angle subtended between the slit and the goniometer s center. We saw that diffractometers generally include several slits, placed before or after the sample. 

P = 1 kW at A. = 600 nm illuminates sample in a cell at p = 1 mbar and T = 300 K. A rectangular intensity profile is assumed with a laser-beam cross section of 1 cm. Which fraction of all IV,- in the absorbing lower level /> is excited when the laser is tuned to a weak absorbing transition /) k) with the absorption cross section... 

Note For larger diameters of the oven hole A, the density profile n(x) of the molecular beam is no longer rectangular but decreases gradually beyond the limiting angles 6 = . For A > > y, the absorption profile is then altered compared to that in (4.9), while for A > y the difference is negligible because the Lorentzian profile is dominant in the latter case [388]. 

A collimated effusive molecular beam with a rectangular density profile behind the collimating aperture has a thermal velocity distribution at T = 500 K. Calculate the intensity profile a oS) of an absorption line, centered at two for molecules at rest, if the beam of a weak tunable monochromatic laser crosses the molecular beam under 45° against the molecular beam axis... 

Kazoe et al. recently measured the proton concentration profile in a 2-D rectangular subnanochannel, 410 imi in width and 405 nm in depth, using STED fluorescein [46]. Since the detection volume is small, the signal to noise ratio (S/N) is relatively low. In order to increase S/N, two methods have been used. First, since the fluorescent intensity is also affected by the excitation intensity of laser beam and concentration of fluorescent dye and there can be a nonuniform distributimi of fluorescein imis within the EDL near the wall because of electrostatic potential in... 

When PMMA was ablated in an atmosphere of nitrogen and in methanol, the channels were rectangular. On the other hand, when the ablation was under water, the profile was wedge shaped. This change in channel geometry was attributed to the change in the path of the laser beam through the water [11],... 

This example can be applied to an atom that traverses a laser beam with a rectangular intensity profile (Fig. 3.19a). The oscillator amplitude x(t) is proportional to the field amplitude E = Eo r) cos cot. If the interaction time T = d/v s small compared to the damping time 7 = l/y, the oscillation amplitude can be regarded as constant during the time T. The full halfwidth of the absorption line is then = S.bvfd Su v/d. 

Fig. 3.19a,b. Transition probability J (co) of an atom traversing a laser beam (a) with a rectangular intensity profile /(jc) and (b) with a Gaussian intensity profile for the case y< /T = vld. The intensity profile I((o) of an absorption line is proportional to P(co)... 

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