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- Arwin, Hans, 1950-, et al.
(författare)
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Total internal reflection ellipsometry : principles and applications
- 2004
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Ingår i: Applied Optics. - 0003-6935 .- 1539-4522. ; 43:15, s. 3028-3036
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Tidskriftsartikel (refereegranskat)abstract
- A concept for a measurement technique based on ellipsometry in conditions of total internal reflection is presented. When combined with surface plasmon resonance (SPR) effects, this technique becomes powerful for monitoring and analyzing adsorption and desorption on thin semitransparent metal films as well as for analyzing the semitransparent films themselves. We call this technique total internal reflection ellipsometry (TIRE). The theory of ellipsometry under total internal reflection combined with SPR is discussed for some simple cases. For more advanced cases and to prove the concept, simulations are performed with the Fresnel formalism. The use of TIRE is exemplified by applications in protein adsorption, corrosion monitoring, and adsorption from opaque liquids on metal surfaces. Simulations and experiments show greatly enhanced thin-film sensitivity compared with ordinary ellipsometry.
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| 2. |
- Bennett, J. M., et al.
(författare)
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Test of Opticlean strip coating material for removing surface contamination
- 2000
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Ingår i: Applied Optics. - 0003-6935 .- 1539-4522. ; 39:16, s. 2737-2739
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Tidskriftsartikel (refereegranskat)abstract
- The strip coating material, Opticlean, which has been reformulated, has been shown to remove 1-5-mu m-diameter particles as well as contamination remaining from previous drag wipe cleaning on a used silicon wafer. In addition, no residue that produced scattering was found on a fresh silicon wafer when Opticlean was applied and then stripped off. The total integrated scattering technique used for the measurements could measure scattering levels of He-Ne laser light as low as a few ppm (parts in 106), corresponding to a surface roughness of <1 Angstrom rms.
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| 3. |
- Enejder, Annika, 1969, et al.
(författare)
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Influence of cell shape and aggregate formation on the optical properties of flowing whole blood
- 2003
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Ingår i: Applied Optics. - : The Optical Society. - 2155-3165 .- 0003-6935 .- 1539-4522. ; 42:7, s. 1384-1394
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Tidskriftsartikel (refereegranskat)abstract
- We studied the influence of shape and secondary, or intercellular, organization on the absorption and scattering properties of red blood cells to determine whether these properties are of any practical significance for optical evaluation of whole blood and its constituents. A series of measurements of transmittance and reflectance of light from bovine blood in a flow cuvette was conducted with a 650-900-nm integrating sphere at shear rates of 0-1600 s(-1), from which the influence of cell orientation, elongation, and aggregate formation on the absorption (mu(a)) and the reduced scattering coefficients could be quantified. Aggregation was accompanied by a decrease of 4% in mu(s)' compared with the value in randomly oriented single cells. Increasing the degree of cell alignment and elongation as a result of increasing shear rate reduced mu(s)' by 6% and mu(a) by 3%, evaluated at a shear rate of 1600 s(-1). Comparison with T-matrix computations for oblate- and prolate-shaped cells with corresponding elongation and orientation indicates that the optical properties of whole blood are determined by those of its individual cells, though influenced by a collective scattering factor that depends on the cell-to-cell organization. We demonstrate that cell morphological changes must be taken into consideration when one is conducting whole blood spectroscopy. (C) 2003 Optical Society of America.
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| 4. |
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| 5. |
- Fällman, Erik, et al.
(författare)
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Influence of a glass-water interface on the on-axis trapping of micrometer-sized spherical objects by optical tweezers
- 2003
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Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 42:19, s. 3915-3926
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Tidskriftsartikel (refereegranskat)abstract
- A systematic study of the influence of a glass-water interface on the on-axis trapping of micrometer-sized spherical objects by optical tweezers is presented. The ways in which the escape force and the trapping position, as well as the stiffness of the trap, depend on the focusing depth, the numerical aperture, and the degree of overfilling of the objective entrance pupil are investigated. It is concluded, among other things, that objectives with the highest numerical aperture and the use of large degrees of overfilling do not always provide the optimum trapping conditions at finite depths.
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| 6. |
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| 7. |
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| 8. |
- Kluczynski, Pawel, et al.
(författare)
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Background signals in wavelength-modulation spectrometry by use of frequency-doubled diode-laser light : II Experiment
- 2001
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Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 40:6, s. 794-805
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Tidskriftsartikel (refereegranskat)abstract
- In an accompanying paper [Appl. Opt. 40, 783-193 (2001)], we predict the existence of background signals from a frequency-doubled wavelength-modulated diode-laser system. We now demonstrate and characterize various nf harmonics of such background signals from a system producing light in the 422-nm region by use of a single-pass KNbO3 crystal with respect to the modulation amplitude, the laser center frequency, and the crystal temperature. It is demonstrated that 2f detection is plagued by considerably larger amounts of background signal than is detection at other higher, even harmonics. This result implies that 4f or 6f detection is often to be preferred in comparison with 2f detection when frequency-doubled wavelength-modulation spectrometry (WMS) is to be used. This preference is illustrated by the detection of Ca in an acetylene-air flame. It is also shown that the background signals have a much stronger dependence on the modulation amplitude than do the analytical signals. This difference implies that the optimum detectability for frequency-doubled WMS is often reached for modulation amplitudes lower than those normally used. An analysis of the effect of a finite temperature stability of the doubling crystal on the drift of the background signals as well as on the detectability is included. The results verify the theoretical description given in our accompanying paper.
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| 9. |
- Kluczynski, Pawel, et al.
(författare)
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Background signals in wavelength-modulation spectrometry with frequency-doubled diode-laser light : I Theory
- 2001
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Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 40:6, s. 783-793
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Tidskriftsartikel (refereegranskat)abstract
- Various types of background signals appear when wavelength-modulated (WM) diode-laser light is frequency doubled. We present a theoretical analysis of such background signals in terms of a previously derived formalism for WM spectrometry that is based on a Fourier series. Explicit expressions for various nf harmonics of the background signals are derived. The analysis shows that 2f detection will be plagued by significant background signals when frequency-doubled WM diode-laser light is used. It also demonstrates that 4f and 6f detection will experience background signals but not, however, to the same extent as 2f detection. The analysis illustrates clearly how the various nf harmonics of the background signals depend on entities such as modulation amplitude, associated intensity modulation, dispersion of the frequency-doubling material, laser power, and detuning. The background signals can take both positive and negative values, depending on the relation between these entities. Guidelines for how to minimize these background signals are given.
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| 10. |
- Kluczynski, Pawel, et al.
(författare)
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Characterization of background signals in wavelength-modulation spectrometry in terms of a Fourier based theoretical formalism
- 2001
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Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 40:6, s. 770-782
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Tidskriftsartikel (refereegranskat)abstract
- The detectability of wavelength-modulation (WM) diode-laser spectrometric techniques is frequently limited by various background signals. A new theoretical formalism for WM spectrometry, based on Fourier analysis and therefore capable of handling a variety of phenomena including the characterization and the analysis of analytical as well as background WM signals, was recently presented [Appl. Opt. 38, 5803 (1999)]. We report a detailed characterization of WM background signals from multiple reflections between pairs of surfaces in the optical system that act as etalons and from the associated intensity modulation in terms of this new formalism. The agreement between the background signals from a thin glass plate and those predicted by the formalism is good, which verifies the new Fourier analysis-based formalism.
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