| 1. |
- Eriksson, Emma, 1980, et al.
(författare)
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Optical manipulation and microfluidics for studies of single cell dynamics
- 2007
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Ingår i: Journal of Optics. A, Pure and applied optics. - 1464-4258 .- 1741-3567 .- 1361-6617. ; 9:8, s. 113-121
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Tidskriftsartikel (refereegranskat)abstract
- Most research on optical manipulation aims towards investigation and development of the system itself. In this paper we show how optical manipulation, imaging and microfluidics can be combined for investigations of single cells. Microfluidic systems have been fabricated and are used, in combination with optical tweezers, to enable environmental changes for single cells. The environment within the microfluidic system has been modelled to ensure control of the process. Three biological model systems have been studied with different combinations of optical manipulation, imaging techniques and microfluidics. In Saccharomyces cerevisiae, environmentally induced size modulations and spatial localization of proteins have been studied to elucidate various signalling pathways. In a similar manner the oxygenation cycle of single red blood cells was triggered and mapped using Raman spectroscopy. In the third experiment the forces between the endoplasmic reticulum and chloroplasts were studied in Pisum sativum and Arabidopsis thaliana. By combining different techniques we make advanced biological research possible, revealing information on a cellular level that is impossible to obtain with traditional techniques.
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| 2. |
- Blomstedt, K., et al.
(författare)
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Effective degree of coherence : general theory and application to electromagnetic fields
- 2007
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Ingår i: Journal of Optics. A, Pure and applied optics. - : IOP Publishing. - 1464-4258 .- 1741-3567. ; 9:10, s. 907-919
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Tidskriftsartikel (refereegranskat)abstract
- The concept of overall or effective degree of coherence has proven useful and insightful in the scalar theory of light. In this paper we extend the concept to fields represented over arbitrary vector (Hilbert) spaces. We show that the effective degree of coherence remains unaltered by scaled unitary mappings, which describe for instance many physical interactions. In the context of random, vector-valued electromagnetic fields the invariance implies that the effective degree of coherence assumes the same value in commonly used representation spaces. Thereby, in contrast to the local degree of coherence, this quantity can be taken as an intrinsic property of the electromagnetic wave field. In particular, the effective degree of coherence does not change when the field is scattered by a lossless medium and it can be determined from the far-field pattern. Hence the effective degree of coherence of electromagnetic fields is readily measurable.
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| 3. |
- Petermann, Ingemar, et al.
(författare)
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Tunable and programmable optical bandpass filter
- 2007
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Ingår i: Journal of Optics. A, Pure and applied optics. - : IOP Publishing. - 1464-4258 .- 1741-3567. ; 9:11, s. 1057-1061
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a novel tunable and programmable optical bandpass filter with a transmission peak less than 5 pm wide that is tunable over 18.5 nm. The number of transmission windows within the stop band, as well as each window's position and strength, is set by applying a heat profile to a chirped fibre Bragg grating with the aid of a thermal printer head comprising a 640 pixel array. It is shown that the width of a transmission peak formed by local heating is mainly determined by the refractive index modulation depth and chirp rate and not by the width of the heated region.
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| 4. |
- Rahachou, Aliaksandr, et al.
(författare)
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Light propagation in nanorod arrays
- 2007
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Ingår i: Journal of optics. A: Pure and applied optics. - : IOP Publishing. - 1464-4258 .- 1741-3567. ; 9:3, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- We study the propagation of TM- and TE-polarized light in two-dimensional arrays of silver nanorods of various diameters in a gelatin background. We calculate the transmittance, reflectance and absorption of arranged and disordered nanorod arrays and compare the exact numerical results with the predictions of the Maxwell–Garnett effective-medium theory. We show that interactions between nanorods, multipole contributions and formations of photonic gaps affect strongly the transmittance spectra that cannot be accounted for in terms of the conventional effective-medium theory. We also demonstrate and explain the degradation of the transmittance in arrays with randomly located rods as well as the weak influence of their fluctuating diameter. For TM modes we outline the importance of the skin effect, which causes the full reflection of the incoming light. We then illustrate the possibility of using periodic arrays of nanorods as high-quality polarizers.
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| 5. |
- Sergeyev, Sergey V., et al.
(författare)
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Polarization-dependent gain and gain fluctuations in a fiber Raman amplifier
- 2007
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Ingår i: Journal of Optics. A, Pure and applied optics. - : IOP Publishing. - 1464-4258 .- 1741-3567. ; 9:12, s. 1119-1122
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Tidskriftsartikel (refereegranskat)abstract
- We report a new vector model of a fiber Raman amplifier with a randomly varying birefringence. We find that the analysis of gain fluctuations and polarization-dependent gain can be used for measurements of beat and birefringence correlation lengths and the polarization mode dispersion value on a long single-mode fiber. Results are consistent with a standard technique based on differential group delay measurements.
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| 6. |
- Xiao, Sanshui, et al.
(författare)
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Theoretical study of the transmission properties of a metallic film with surface corrugations
- 2007
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Ingår i: Journal of Optics. A, Pure and applied optics. - : IOP Publishing. - 1464-4258 .- 1741-3567. ; 9:4, s. 348-351
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Tidskriftsartikel (refereegranskat)abstract
- Transmissions through a metallic film at near-infrared wavelengths with different surface corrugations on both sides are systemically studied. The calculations are performed by the three-dimensional finite-different time-domain method. Calculated results show that the transmissions are strongly dependent on the surface structures. Compared with other structures, the transmission for a film periodically drilled by cross air grooves are relatively larger. Transmission is enhanced more with symmetric conditions on both layers than the asymmetric case. The enhanced transmission can be explained by a competition between the absorption in the metal and enhanced transmission due to coupled surface plasmon resonance.
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