| 1. |
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| 2. |
- Hakkarainen, T., et al.
(författare)
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Imaging of interacting nano-objects with superlenses
- 2012
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Ingår i: Biomedical Optics, BIOMED 2012. - Washington, D.C. : Optical Society of America. - 9781557529428
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Konferensbidrag (refereegranskat)abstract
- Employing rigorous electromagnetic theory we show that near-field imaging of point-like objects with subwavelength resolution is achieveable with nanoslab superlenses. For a metallic lens the resolution is »λ/5, whereas for a metamaterial lens λ/10 is obtained. We also illustrate how the near-field interactions among the objects and the lens affect the imaging.
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| 3. |
- Hakkarainen, T., et al.
(författare)
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Near-field imaging of interacting nano objects with metal and metamaterial superlenses
- 2012
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14, s. 043019-
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Tidskriftsartikel (refereegranskat)abstract
- Employing rigorous electromagnetic theory we investigate optical the near-field imaging of two interacting dipole-like objects with metal and slightly lossy metamaterial nanoslab superlenses. Our analysis indicates that the dipole emission is suppressed by near-field interactions when the objects are close to the lens or each other. This strongly influences the image quality, in particular with objects of small size and high polarizability. The interference from two nearby objects also affects the resolution and subwavelength definition can only be obtained for objects with dipole moments predominantly orthogonal to the slab. Such an optimal imaging condition is achieved with excitation by total internal reflection. With simulations we show that in these circumstances, subwavelength resolutions of about lambda/5 for silver superlens and lambda/10 for metamaterial slab are reached.
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| 4. |
- Hakkarainen, T., et al.
(författare)
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Near-field imaging of point dipole with silver superlens
- 2010
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Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 101:4, s. 731-734
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Tidskriftsartikel (refereegranskat)abstract
- Making use of exact and quasistatic expressions for the field in near-field imaging of a point dipole by a thin silver slab, we calculate the point-spread function and the associated image resolution. We show that the resolution, which depends on the silver slab thickness and the dipole orientation, generally is better than the conventional diffraction limit and can be as high as lambda/8. The results substantially agree with recent theoretical and experimental studies on 2D objects.
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| 5. |
- Hassinen, T., et al.
(författare)
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Electromagnetic Hanbury Brown-Twiss phenomenon
- 2011
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Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. - 9780819487971
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Konferensbidrag (refereegranskat)abstract
- We analyze the classic Hanbury Brown-Twiss effect for thermal electromagnetic fields in space-frequency domain. We compare two different approaches and show that the normalized correlation of intensity fluctuations is fully characterized by the spectral electromagnetic degree of coherence, a result analogous to scalar analysis of the effect. Differences between the two approaches are discussed.
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| 6. |
- Hassinen, T., et al.
(författare)
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Hanbury Brown-Twiss effect with electromagnetic waves
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:16, s. 15188-15195
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Tidskriftsartikel (refereegranskat)abstract
- The classic Hanbury Brown-Twiss experiment is analyzed in the space-frequency domain by taking into account the vectorial nature of the radiation. We show that as in scalar theory, the degree of electromagnetic coherence fully characterizes the fluctuations of the photoelectron currents when a random vector field with Gaussian statistics is incident onto the detectors. Interpretation of this result in terms of the modulations of optical intensity and polarization state in two-beam interference is discussed. We demonstrate that the degree of cross-polarization may generally diverge. We also evaluate the effects of the state of polarization on the correlations of intensity fluctuations in various circumstances.
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| 7. |
- Jouttenus, T., et al.
(författare)
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Connection between electric and magnetic coherence in free electromagnetic fields
- 2005
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Ingår i: Physical Review E. - 1539-3755. ; 72:4
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Tidskriftsartikel (refereegranskat)abstract
- We introduce quantitative measures for the description of the electric and magnetic coherence in a stationary, random electromagnetic field at two points, in a volume, and in the Fourier space. These quantities are applied to free electromagnetic fields, and several theorems regarding the relationship between the two types of coherences in such fields are established. Fields which are statistically homogeneous, and those which, in addition, are statistically isotropic are considered separately. Furthermore, the connection between the electric and magnetic coherence is exemplified for some specific statistically homogeneous fields.
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| 8. |
- Kellock, H., et al.
(författare)
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Higher-order ghost imaging with partially polarized classical light
- 2011
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Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. - 9780819487971
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Konferensbidrag (refereegranskat)abstract
- Visibility, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) are quantities that characterize the quality of the image in ghost (or correlation) imaging. The visibility in quantum and classical ghost imaging with scalar light is known to improve as the order of imaging increases. Recently also electromagnetic ghost imaging has started to attract attention. In this work we analyze the effects of both the order of imaging and the degree of polarization (P) of the illumination on the image quality parameters. The source is a classical, partially polarized, random electromagnetic field obeying Gaussian statistics. The beam is split into several (N) parts which are directed either into the object or reference arms and the associated intensity correlations are calculated. When N > 2, more than one reference arm may exist which contributes to the background. We consider two different definitions for the visibility, as well as the SNR and CNR, and examine their attainable limiting values in second- and higher-order ghost imaging as a function of the degree of polarization. Both expressions of the visibility behave in a similar manner; they increase with the order of imaging and the degree of polarization. In second-order imaging the SNR decreases, due to increased noise, as P increases, while the CNR remains essentially constant. We emphasize that the exact numerical values depend on the definitions used and on the number of object arms in the setup.
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| 9. |
- Kellock, H., et al.
(författare)
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Temporal double- and triple-intensity correlation imaging with classical light
- 2010
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Ingår i: 2010 9th Euro-American Workshop on Information Optics, WIO 2010. - 9781424482276 ; , s. 5582500-
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Konferensbidrag (refereegranskat)abstract
- The second- and third-order temporal ghost imaging setups with classical light are discussed. The second-order scheme has a single reference arm with a temporal lens and dispersive elements, and an object arm containing an object surrounded by dispersive media. The third-order imaging setup contains two reference arms instead of one. Both setups have a temporally completely incoherent light source providing maximum resolution. The dependence of visibility and resolution of the images on system parameters is considered in both setups.
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| 10. |
- Saastamoinen, T., et al.
(författare)
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Electromagnetic coherence theory of laser resonator modes
- 2005
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Ingår i: Journal of the Optical Society of America a-Optics Image Science and Vision. - 1084-7529. ; 22:1, s. 103-108
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Tidskriftsartikel (refereegranskat)abstract
- A theory of open laser resonators is formulated within the framework of the electromagnetic coherence theory. It is shown that if only one Fox-Li mode contributes to the field at a given frequency. then the field at that frequency is necessarily completely coherent in view of the space- frequency, counterpart of the recently introduced degree of coherence of electromagnetic fields [Opt. Express 11, 1137 (2003)]. It is also shown that the relation between the number of Fox-Li modes and the new degree of coherence is analogous to the relation established in the scalar theory of laser resonator modes. Difficulties that arise with the formerly introduced visibility-based definition of the electromagnetic degree of coherence are briefly discussed.
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