| 1. |
- Daniel, Salman, et al.
(författare)
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Dynamic control of optical transmission through a nano-slit using surface plasmons
- 2015
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 23:17, s. 22512-22519
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how the optical transmission by a directly illuminated, sub-wavelength slit in a metal film can be dynamically controlled by varying the incident beam's phase relative to that of a stream of surface plasmon polaritions which are generated at a nearby grating. The transmission can be smoothly altered from its maximum value to practically zero. The results from a simple model and from rigorous numerical simulations are in excellent agreement with our experimental results. Our method may be applied in all-optical switching.
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| 2. |
- Friberg, Ari T., et al.
(författare)
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Spectral elementary-coherence-function representation for partially coherent light pulses
- 2007
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Ingår i: Optics Express. - 1094-4087. ; 15:8, s. 5160-5165
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Tidskriftsartikel (refereegranskat)abstract
- A broad class of partially coherent non-stationary fields can be expressed in terms of the recently proposed independent-elementary-pulse model. In this work we first introduce a corresponding dual representation in the frequency domain and then extend this concept by considering shifted and weighted elementary spectral coherence functions. We prove that this method, which closely describes practical optical systems, leads to properly defined correlation functions. As an example, we demonstrate that our new model characterizes, in a natural way, trains of ultra-short pulses, affected by noise and timing jitter, emitted by usual modulators employed in telecom applications.
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| 3. |
- 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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| 4. |
- Iyer, Srinivasan, et al.
(författare)
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Impact of apexes on the resonance shift in double hole nanocavities
- 2010
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Ingår i: Optics Express. - 1094-4087. ; 18:1, s. 193-203
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Tidskriftsartikel (refereegranskat)abstract
- The transmission of light through metallic films with periodic double nanoholes is studied using vectorial three-dimensional finite element method. Special emphasis is given on understanding different transmission resonances arising in gold and silver films with periodic sub-wavelength holes of different shapes. The spectral shift of the hole-shape resonance resulting from a variation of the hole refractive index is analyzed for a double nanohole geometry in the transmission mode using numerical simulations. Specifically, the role of field enhancement at the apexes of the double nanohole in the sensing of medium within the hole cavity is pointed out and discussed. The presence of sharp apexes within the double nanoholes significantly improves the resonance sensitivity as compared to rectangular holes of comparable area. Impact of possible manufacturing errors on the overall sensitivity is also characterized. Robustness and a relatively simple fabrication procedure make these kinds of refractive index sensors practically attractive.
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| 5. |
- Iyer, Srinivasan, et al.
(författare)
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Transmission resonances in periodic U-shaped metallic nanostructures
- 2010
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Ingår i: Optics Express. - 1094-4087. ; 18:17, s. 17719-17728
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Tidskriftsartikel (refereegranskat)abstract
- The spectral response of crescent-like metallic nanostructures, a sub-class of U-shaped split-ring resonators, on a glass substrate at normal incidence is studied numerically. Also, the interpretation of transmission resonances arising from periodic conventional standard split-ring resonators with rectangular edges (SSRR) at normal incidence is revisited. In particular, we focus on one specific transmission resonance which is present for nano-crescents (NC) but absent in the case of SSRRs used for metamaterials. It is proposed that for a U-shaped metallic structure of arbitrary geometry, coupling of plasmonic eigen modes at all the surfaces of the three-dimensional structure is essential to be considered. The manner in which the coupling takes place between plasmonic modes at all the surfaces of the three-dimensional structure is what completely characterizes transmission resonances, and it is unique for each given resonance. (C) 2010 Optical Society of America
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| 6. |
- Jacobsen, Gunnar, et al.
(författare)
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EEPN and CD study for coherent optical nPSK and nQAM systems with RF pilot based phase noise compensation
- 2012
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Ingår i: Optics Express. - 1094-4087. ; 20:8, s. 8862-8870
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Tidskriftsartikel (refereegranskat)abstract
- A radio frequency (RF) carrier can be used to mitigate the phase noise impact in n-level PSK and QAM systems. The systems performance is influenced by the use of an RF pilot carrier to accomplish phase noise compensation through complex multiplication in combination with discrete filters to compensate for the chromatic dispersion (CD). We perform a detailed study comparing two filters for the CD compensation namely the fixed frequency domain equalizer (FDE) filter and the adaptive least-mean-square (LMS) filter. The study provides important novel physical insight into the equalization enhanced phase noise (EEPN) influence on the system bit-error-rate (BER) versus optical signal-to-noise-ratio (OSNR) performance. Important results of the analysis are that the FDE filter position relative to the RF carrier phase noise compensation module provides a possibility for choosing whether the EEPN from the Tx or the LO laser influences the system quality. The LMS filter works very inefficiently when placed prior to the RF phase noise compensation stage of the Rx whereas it works much more efficiently and gives almost the same performance as the FDE filter when placed after the RF phase noise compensation stage.
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| 7. |
- Jacobsen, Gunnar, et al.
(författare)
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Receiver implemented RF pilot tone phase noise mitigation in coherent optical nPSK and nQAM systems
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:15, s. 14487-14494
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a novel method for extracting an RF pilot carrier signal in the coherent receiver is presented. The RF carrier is used to mitigate the phase noise influence in n-level PSK and QAM systems. The performance is compared to the use of an (ideal) optically transmitted RF pilot tone. As expected an electronically generated RF carrier provides less efficient phase noise mitigation than the optical RF. However, the electronically generated RF carrier still improves the phase noise tolerance by about one order of magnitude in bit error rate (BER) compared to using no RF pilot tone. It is also found, as a novel study result, that equalization enhanced phase noise - which appears as correlated pure phase noise, amplitude noise and time jitter - cannot be efficiently mitigated by the use of an (optically or electrically generated) RF pilot tone.
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| 8. |
- Lindberg, J., et al.
(författare)
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Spectral analysis of resonant transmission of light through a single sub-wavelength slit
- 2004
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Ingår i: Optics Express. - 1094-4087. ; 12:4, s. 623-632
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the spectral properties of resonant transmission of light through a sub-wavelength slit in a metal film. We show that the enhanced transmission can be understood in terms of interfering surface-wave-like modes propagating in the slit. We characterize the effect of geometrical and material properties of the slit on the transmission spectrum. Furthermore, we show that the wavelength of the transmission resonance strongly depends on the surrounding medium. This effect may be utilized in sensors, imaging, and the detection of, e.g. biomolecules.
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| 9. |
- Ricciardi, Sebastien, et al.
(författare)
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Thermally induced wavelength tunability of microcavity solid-state dye lasers
- 2007
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Ingår i: Optics Express. - 1094-4087. ; 15:20, s. 12971-12978
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Tidskriftsartikel (refereegranskat)abstract
- Wavelength tunability of a microcavity solid-state dye laser is modeled and demonstrated by simulations making use of the finite element method. We investigate the application of two phenomena, thermoelastic expansion of the microcavity material and thermo-induced change of the refractive index, to tune the microcavity mode frequencies by a variation of the effective optical path. An optimized size of the laser microcavity is defined depending on the operation wavelength bandwidth and the glass transition temperature of the gain material.
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| 10. |
- Saastamoinen, Kimmo, et al.
(författare)
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Spatial coherence measurement of polychromatic light with modified Young's interferometer
- 2013
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Ingår i: Optics Express. - 1094-4087. ; 21:4, s. 4061-4071
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Tidskriftsartikel (refereegranskat)abstract
- Partial spatial coherence is a fundamental concept in optical systems. Theoretically, the normalized mutual coherence function gives a quantitative measure for partial spatial coherence regardless of the spectral nature of the radiation. For narrowband light the degree of spatial coherence can be measured in terms of the fringe modulation in the classic Young's two-pinhole interferometer. Though not commonly appreciated, with polychromatic radiation this is not the case owing to the wavelength dependence of diffraction. In this work we show that with a modified two-beam interferometer containing an achromatic Fresnel transformer the degree of spatial coherence is again related to the visibility of intensity fringes in Young's experiment for any polychromatic light. This result, which is demonstrated both theoretically and experimentally, thus restores the usefulness of the two-pinhole interferometer in the measurement of the spatial coherence of light beams of arbitrary spectral widths.
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