| 1. |
- Ehrich, Dorothee, et al.
(författare)
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Documenting lemming population change in the Arctic : Can we detect trends?
- 2020
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 49:3, s. 786-800
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Tidskriftsartikel (refereegranskat)abstract
- Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.
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| 2. |
- Parunova, Yulia, et al.
(författare)
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Potentially implantable biocathode with the function of charge accumulation based on nanocomposite of polyaniline/carbon nanotubes
- 2016
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Ingår i: Russian journal of electrochemistry. - : Springer. - 1023-1935 .- 1608-3342. ; 52:12, s. 1166-1171
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Tidskriftsartikel (refereegranskat)abstract
- A potentially implantable biocathode with the function of charge accumulation based on a nanobiocomposite including multiwall carbon nanotubes, polyaniline, and bilirubin oxidase is developed. The regularities of the functioning of the obtained electrode are studied in air-satd. phosphate buffer soln., pH 7.4 (PB), and also in phosphate buffer soln. contg. redox-active blood components (BMB). The open circuit potential of the biocathode is 0.33 and 0.08 V vs. the SCE in PB and BMB, resp.; it is completely restored after at least three self-charge/discharge cycles with connection to resistors with different resistance. Bioelectrocatalytic c.d. of oxygen redn. is 0.50 and 0.42 mA cm-2 with the residual activity of 78 and 60% of the initial value after 12 h of continuous operation in PB at 25°C and in BMB at 37°C, resp.
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| 3. |
- Sergeyev, Sergey V., et al.
(författare)
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Dissipative vector solitons with fast evolving states of polarization
- 2014
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Ingår i: Nonlinear Photonics, NP. - Washington, D.C. : OSA. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We report on a new vector model of an erbium doped fiber laser mode locked with carbon nanotubes. This model goes beyond the limitations of the previously used models based on either coupled nonlinear Schrödinger or Ginzburg-Landau equations. It results in a new family of vector solitons with fast evolving states of polarization experimentally observed in our previous papers.
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| 4. |
- Sergeyev, Sergey V., et al.
(författare)
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Vector solitons in mode locked fibre lasers
- 2014
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Ingår i: International Conference on Transparent Optical Networks. - : IEEE. - 9781479956005 - 9781479956012
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Konferensbidrag (refereegranskat)abstract
- We overview our recent results on polarisation dynamics of vector solitons in erbium doped fibre laser mode locked with carbon nanotubes. Our experimental and theoretical study revealed new families of vector solitons for fundamental and bound-state soliton operations. The observed scenario of the evolution of the states of polarisation (SOPs) on the Poincare sphere includes fast polarisation switching between two and three SOPs along with slow SOP evolution on a double scroll chaotic attractor. The underlying physics presents an interplay between effects of birefringence of the laser cavity and light induced anisotropy caused by polarisation hole burning.
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| 5. |
- Andoralov, Viktor, et al.
(författare)
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Biofuel cell based on microscale nanostructured electrodes with inductive coupling to rat brain neurons
- 2013
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; :3
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Tidskriftsartikel (refereegranskat)abstract
- Miniature, self-contained biodevices powered by biofuel cells may enable a new generation of implantable, wireless, minimally invasive neural interfaces for neurophysiological in vivo studies and for clinical applications. Here we report on the fabrication of a direct electron transfer based glucose/oxygen enzymatic fuel cell (EFC) from genuinely three-dimensional (3D) nanostructured microscale gold electrodes, modified with suitable biocatalysts. We show that the process underlying the simple fabrication method of 3D nanostructured electrodes is based on an electrochemically driven transformation of physically deposited gold nanoparticles. We experimentally demonstrate that mediator-, cofactor-, and membrane-less EFCs do operate in cerebrospinal fluid and in the brain of a rat, producing amounts of electrical power sufficient to drive a self-contained biodevice, viz. 7 μW cm−2 in vitro and 2 μW cm−2 in vivo at an operating voltage of 0.4 V. Last but not least, we also demonstrate an inductive coupling between 3D nanobioelectrodes and living neurons.
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| 6. |
- Andoralov, Victor, et al.
(författare)
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Octaheme nitrite reductase : The mechanism of intramolecular electron transfer and kinetics of nitrite bioelectroreduction.
- 2021
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 138
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Tidskriftsartikel (refereegranskat)abstract
- Detailed impedance and voltammetric studies of hexameric octaheme nitrite reductase immobilized on carbon-based nanomaterials, specifically nanotubes and nanoparticles, were performed. Well-pronounced bioelectrocatalytic reduction of nitrite on enzyme-modified electrodes was obtained. Analysis of the impedance data indicated the absence of long-lived intermediates involved in the nitrite reduction. Cyclic voltammograms of biomodified electrodes had a bi-sigmoidal shape, which pointed to the presence of two enzyme orientations on carbon supports. The maximum (limiting) catalytic currents were determined and, by applying the correction by the mixed kinetics equation, the Tafel dependences were plotted for each catalytic wave/each enzyme orientation. Finally, two schemes for the rate-limiting processes during bioelectrocatalysis were proposed, viz. for low- and high-potential orientations.
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| 7. |
- Baenas, Isabel, et al.
(författare)
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Impact of COVID-19 Lockdown in Eating Disorders : A Multicentre Collaborative International Study
- 2022
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Ingår i: Nutrients. - : MDPI AG. - 2072-6643. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Background. The COVID-19 lockdown has had a significant impact on mental health. Patients with eating disorders (ED) have been particularly vulnerable. Aims. (1) To explore changes in eating-related symptoms and general psychopathology during lockdown in patients with an ED from various European and Asian countries; and (2) to assess differences related to diagnostic ED subtypes, age, and geography. Methods. The sample comprised 829 participants, diagnosed with an ED according to DSM-5 criteria from specialized ED units in Europe and Asia. Participants were assessed using the COVID-19 Isolation Scale (CIES). Results. Patients with binge eating disorder (BED) experienced the highest impact on weight and ED symptoms in comparison with other ED subtypes during lockdown, whereas individuals with other specified feeding and eating disorders (OFSED) had greater deterioration in general psychological functioning than subjects with other ED subtypes. Finally, Asian and younger individuals appeared to be more resilient. Conclusions. The psychopathological changes in ED patients during the COVID-19 lockdown varied by cultural context and individual variation in age and ED diagnosis. Clinical services may need to target preventive measures and adapt therapeutic approaches for the most vulnerable patients.
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| 8. |
- Baitenov, Adil, 1994-
(författare)
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Light propagation and photonic functionalization of semi-ordered material (transparent wood)
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Investigating novel materials requires understanding their chemical and optical properties, which allows for finding their uses through functionalization by chemical modification. In this thesis, we are focusing on a material with high anisotropic scattering - transparent wood. This biocomposite material has a hierarchical structure ranging from nanometer to hundreds of micrometers scale, and natural ordering, which is between perfectly ordered and fully random structure. Optical transparency in the visible range and the unique structure of transparent woods show good potential for functionalization. Due to complex structure and nonhomogenous chemical composition, not all characterization methods are fitting. While relatively straightforward properties like transmittance and haze can be measured using known techniques, but additional investigation was required to understand light behavior and measure other properties. In this work, the modeling method for investigation of light propagation and estimation of the effective refractive index of transparent wood for a deeper understanding of a material. Transparent wood has shown excellent host properties, capable of holding high concentrations of Rhodamine 6G laser dye without aggregate formation. In this dissertation, we present the analysis of the host properties of transparent wood and show that the dye forms statistical energy traps at high concentrations of dye. By doping transparent wood with active dye and pumping it with SHGNd:YAG green laser, the optical gain within the active media can be achieved. The feedback in this optical system is occurring via scattering on fiber walls, showing behavior similar to random lasers. However, due to the semi-ordered structure and wave-guiding effect of transparent wood, the transparent wood laser is referred to as a ”quasi-random laser”. The lasing emission can be further enhanced by the introduction of an external cavity, virtually expanding the active media allowing more lasing modes to be resolved, and increasing laser power.This work demonstrates the characterization of transparent wood optical and chemical properties and develops a computational model that can be used for further investigation of light behavior in semi-ordered anisotropic media. The functionalization of transparent wood is demonstrated by the introduction of a quasi-random laser and modification of that laser is presented.
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| 9. |
- Blank, Vladimir D., et al.
(författare)
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High-pressure polymerized phases of C60
- 1998
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Ingår i: Carbon. - 0008-6223 .- 1873-3891. ; 36:4, s. 319-343
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- Data from recent experimental studies of C60 under high pressures are collected and analyzed, concentrating on the polymerized states where covalent intermolecular bonds have been formed through treatment of molecular C60 at high pressures and temperatures at or above room temperature. We give an overview of the observed phase transformations and the structures of metastable polymeric phases, both crystalline and disordered, as analyzed under ambient conditions, and we present and discuss a pressure-temperature diagram showing which synthesis conditions result in which final phases in the pressure range up to 20 GPa (200 kbar) and at temperatures up to 2300 K. The physical properties of the various phases are discussed whenever enough data are available. The pressure-temperature stability limits for C60 and the conditions for the transformation of C60 into graphite, diamond and chaoite-type carbon are derived.
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| 10. |
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| 11. |
- Bogdanov, Sergey, et al.
(författare)
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Physics insight into “The Canterbury Tales” Chronotope
- 2015
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Ingår i: Physics Education. - : IOP Publishing. - 0031-9120 .- 1361-6552. ; 50:4, s. 462-467
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Tidskriftsartikel (refereegranskat)abstract
- Many students regard physics as an isolated, sophisticated and perhaps a boring branch of science. Meanwhile, physics is embedded in most events and issues of society, culture and everyday life. To find and include such relevant contexts is one of the challenges for every physics teacher. Here we present our findings, which concern the classic The Canterbury Tales by Geoffrey Chaucer. Some important questions are still open and disputed, such as the dates of events in the story. In particular, physics can provide a method for an approximate estimation of the dates and places of the events in the tales. This paper provides some of the details.
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| 12. |
- Chagtai, Tasnim, et al.
(författare)
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Gain of 1q as a prognostic biomarker in Wilms Tumors (WTs) treated with preoperative chemotherapy in the International Society of Paediatric Oncology (SIOP) WT 2001 trial : A SIOP renal tumours biology consortium study
- 2016
-
Ingår i: Journal of Clinical Oncology. - 0732-183X. ; 34:26, s. 3195-3203
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Wilms tumor (WT) is the most common pediatric renal tumor. Treatment planning under International Society of Paediatric Oncology (SIOP) protocols is based on staging and histologic assessment of response to preoperative chemotherapy. Despite high overall survival (OS), many relapses occur in patients without specific risk factors, and many successfully treated patients are exposed to treatments with significant risks of late effects. To investigate whether molecular biomarkers could improve risk stratification, we assessed 1q status and other potential copy number biomarkers in a large WT series. Materials and Methods: WT nephrectomy samples from 586 SIOP WT 2001 patients were analyzed using a multiplex ligation-dependent probe amplification (MLPA) assay that measured the copy number of 1q and other regions of interest. Results: One hundred sixty-seven (28%) of 586 WTs had 1q gain. Five-year event-free survival (EFS) was 75.0% in patients with 1q gain (95% CI, 68.5% to 82.0%) and 88.2% in patients without gain (95% CI, 85.0% to 91.4%). OS was 88.4% with gain (95% CI, 83.5% to 93.6%) and 94.4% without gain (95% CI, 92.1% to 96.7%). In univariable analysis, 1q gain was associated with poorer EFS (P < .001; hazard ratio, 2.33) and OS (P = .01; hazard ratio, 2.16). The association of 1q gain with poorer EFS retained significance in multivariable analysis adjusted for 1p and 16q loss, sex, stage, age, and histologic risk group. Gain of 1q remained associated with poorer EFS in tumor subsets limited to either intermediate-risk localized disease or nonanaplastic localized disease. Other notable aberrations associated with poorer EFS included MYCN gain and TP53 loss. Conclusion: Gain of 1q is a potentially valuable prognostic biomarker in WT, in addition to histologic response to preoperative chemotherapy and tumor stage.
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| 13. |
- Dong, Lin, et al.
(författare)
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Spatial light modulator as a reconfigurable intracavity dispersive element for tunable lasers
- 2010
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Ingår i: Central European Journal of Physics. - : Walter de Gruyter GmbH. - 1895-1082 .- 1644-3608. ; 8:2, s. 228-234
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Tidskriftsartikel (refereegranskat)abstract
- An improved approach for narrow-band wavelength selection in tunable lasers is described. To provide the tunability, a reconfigurable diffractive optical element (DOE) based on a programmable spatial light modulator (PSLM) is applied. With a proper choice of the phase transfer function of the PSLM, the device can be used as a dispersive intra-cavity component for precise tuning within the lasing spectral band of a solid-state dye laser. The suggested design allows avoiding the mechanical movement of any cavity components. The tunability performance and simulation are demonstrated using the Fourier optics method.
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| 14. |
- Dyakov, Sergey, et al.
(författare)
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Optical properties of silicon nanocrystals covered by periodic array of gold nanowires
- 2016
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950. ; 93:20
-
Tidskriftsartikel (refereegranskat)abstract
- Extinction and photoluminescence spectra are experimentally and theoretically studied for a periodic array of gold nanowires deposited on top of a dielectric substrate containing silicon nanocrystals. Quasiguided modes are observed in the substrate resulting in modification of optical properties of silicon nanocrystals. Our calculations of extinction and photoluminescence spectra are in good agreement with experimental results. The periodicity provides a powerful tool for achieving a high photoluminescence outcoupling efficiency of silicon nanocrystals.
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| 15. |
- Fernández-Aranda, Fernando, et al.
(författare)
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COVID Isolation Eating Scale (CIES) : Analysis of the impact of confinement in eating disorders and obesity—A collaborative international study
- 2020
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Ingår i: European Eating Disorders Review. - : Wiley. - 1072-4133 .- 1099-0968. ; 28:6, s. 871-883
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Tidskriftsartikel (refereegranskat)abstract
- Confinement during the COVID-19 pandemic is expected to have a serious and complex impact on the mental health of patients with an eating disorder (ED) and of patients with obesity. The present manuscript has the following aims: (1) to analyse the psychometric properties of the COVID Isolation Eating Scale (CIES), (2) to explore changes that occurred due to confinement in eating symptomatology; and (3) to explore the general acceptation of the use of telemedicine during confinement. The sample comprised 121 participants (87 ED patients and 34 patients with obesity) recruited from six different centres. Confirmatory Factor Analyses (CFA) tested the rational-theoretical structure of the CIES. Adequate goodness-of-fit was obtained for the confirmatory factor analysis, and Cronbach alpha values ranged from good to excellent. Regarding the effects of confinement, positive and negative impacts of the confinement depends of the eating disorder subtype. Patients with anorexia nervosa (AN) and with obesity endorsed a positive response to treatment during confinement, no significant changes were found in bulimia nervosa (BN) patients, whereas Other Specified Feeding or Eating Disorder (OSFED) patients endorsed an increase in eating symptomatology and in psychopathology. Furthermore, AN patients expressed the greatest dissatisfaction and accommodation difficulty with remote therapy when compared with the previously provided face-to-face therapy. The present study provides empirical evidence on the psychometric robustness of the CIES tool and shows that a negative confinement impact was associated with ED subtype, whereas OSFED patients showed the highest impairment in eating symptomatology and in psychopathology.
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| 16. |
- Innocenti, Nicolas, 1986-, et al.
(författare)
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External field enhancement in coupled polymer microcavities - New options for integrated photonic components
- 2009
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Ingår i: European Conference on Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. - 9781424440795
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Microcavities are key components for integrated optical devices and systems. In this paper, enhancement of the resonance electric field outside a pair of coupled polymeric microcavities of hexagonal shape is investigated. Using numerical simulation, enhancement of outside-cavity field has been demonstrated in different sections of the coupled cavity system depending on particular design. Resonance frequencies are in visible part of electromagnetic spectrum. In reported simulations rigorous models based on solving Maxwell equations for propagating electromagnetic field in polymeric materials commonly used in nano-imprinting lithography is demonstrated.
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| 17. |
- Jacobsen, Gunnar, et al.
(författare)
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Phase noise influence in long-range coherent optical OFDM systems with delay detection, IFFT multiplexing and FFT demodulation
- 2012
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Ingår i: Journal of optical communications. - : Walter de Gruyter GmbH. - 0173-4911 .- 2191-6322. ; 33:4, s. 289-295
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the influence of dispersion induced phase noise for CO-OFDM systems using FFT multiplexing/IFFT demultiplexing techniques (software based). The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) including - for the first time to our knowledge - in explicit form the effect of equalization enhanced phase noise (EEPN). This, in turns, leads to an analytic BER specification. Numerical results focus on a CO-OFDM system with 10-25 GS/s QPSK channel modulation. A worst case constellation configuration is identified for the phase noise influence and the resulting BER is compared to the BER of a conventional single channel QPSK system with the same capacity as the CO-OFDM implementation. Results are evaluated as a function of transmission distance. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. For a total capacity of 400 (1000) Gbit/s, the transmission distance to have the BER < 10-2 for the worst case CO-OFDM design is less than 800 and 460 km, respectively, whereas for a single channel QPSK system it is less than 1400 and 560 km.
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| 18. |
- Jacobsen, Gunnar, et al.
(författare)
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Study of EEPN mitigation using modified RF pilot and Viterbi-Viterbi based phase noise compensation
- 2013
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Ingår i: Optics Express. - : Optical Society of American (OSA). - 1094-4087. ; 21:10, s. 12351-12362
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Tidskriftsartikel (refereegranskat)abstract
- We propose - as a modification of the optical (RF) pilot scheme -a balanced phase modulation between two polarizations of the optical signal in order to generate correlated equalization enhanced phase noise (EEPN) contributions in the two polarizations. The method is applicable for n-level PSK system. The EEPN can be compensated, the carrier phase extracted and the nPSK signal regenerated by complex conjugation and multiplication in the receiver. The method is tested by system simulations in a single channel QPSK system at 56 Gb/s system rate. It is found that the conjugation and multiplication scheme in the Rx can mitigate the EEPN to within 1/2 orders of magnitude. Results are compared to using the Viterbi-Viterbi algorithm to mitigate the EEPN. The latter method improves the sensitivity more than two orders of magnitude. Important novel insight into the statistical properties of EEPN is identified and discussed in the paper.
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| 19. |
- Kalashnikov, Vladimir, et al.
(författare)
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Multi-scale polarisation phenomena
- 2016
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Ingår i: LIGHT-SCIENCE & APPLICATIONS. - : CHINESE ACAD SCIENCES. - 2047-7538 .- 2095-5545. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Multi-scale methods that separate different time or spatial scales are among the most powerful techniques in physics, especially in applications that study nonlinear systems with noise. When the time scales (noise and perturbation) are of the same order, the scales separation becomes impossible. Thus, the multi-scale approach has to be modified to characterise a variety of noise-induced phenomena. Here, based on stochastic modelling and analytical study, we demonstrate in terms of the fluctuation-induced phenomena and Hurst R/S analysis metrics that the matching scales of random birefringence and pump-signal states of polarisation interaction in a fibre Raman amplifier results in a new random birefringence-mediated phenomenon, which is similar to stochastic anti-resonance. The observed phenomenon, apart from the fundamental interest, provides a base for advancing multi-scale methods with application to different coupled nonlinear systems ranging from lasers (multimode, mode-locked, random, etc.) to nanostructures (light-mediated conformation of molecules and chemical reactions, Brownian motors, etc.).
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| 20. |
- Kalashnikov, Vladimir, et al.
(författare)
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Stochastic phenomena in a fiber Raman amplifier
- 2017
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Ingår i: Annalen der Physik. - : Wiley-VCH Verlag. - 0003-3804 .- 1521-3889. ; 529:1-2
-
Tidskriftsartikel (refereegranskat)abstract
- The interplay of such cornerstones of modern nonlinear fiber optics as a nonlinearity, stochasticity and polarization leads to variety of the noise induced instabilities including polarization attraction and escape phenomena harnessing of which is a key to unlocking the fiber optic systems specifications required in high resolution spectroscopy, metrology, biomedicine and telecommunications. Here, by using direct stochastic modeling, the mapping of interplay of the Raman scattering-based nonlinearity, the random birefringence of a fiber, and the pump-to-signal intensity noise transfer has been done in terms of the fiber Raman amplifier parameters, namely polarization mode dispersion, the relative intensity noise of the pump laser, fiber length, and the signal power. The obtained results reveal conditions for emergence of the random birefringence-induced resonance-like enhancement of the gain fluctuations (stochastic anti-resonance) accompanied by pulse broadening and rare events in the form of low power output signals having probability heavily deviated from the Gaussian distribution. (Figure presented.).
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| 21. |
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| 22. |
- Leong, Miu Yoong, et al.
(författare)
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Dimensioning BCH Codes for Coherent DQPSK Systems With Laser Phase Noise and Cycle Slips
- 2014
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 32:21, s. 3446-3450
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Tidskriftsartikel (refereegranskat)abstract
- Forward error correction (FEC) plays a vital role in coherent optical systems employing multi-level modulation. However, much of coding theory assumes that additive white Gaussian noise (AWGN) is dominant, whereas coherent optical systems have significant phase noise (PN) in addition to AWGN. This changes the error statistics and impacts FEC performance. In this paper, we propose a novel semianalytical method for dimensioning binary Bose-Chaudhuri-Hocquenghem (BCH) codes for systems with PN. Our method involves extracting statistics from pre-FEC bit error rate (BER) simulations. We use these statistics to parameterize a bivariate binomial model that describes the distribution of bit errors. In this way, we relate pre-FEC statistics to post-FEC BER and BCHcodes. Our method is applicable to pre-FEC BER around 10(-3) and any post-FEC BER. Using numerical simulations, we evaluate the accuracy of our approach for a target post-FEC BER of 10(-5). Codes dimensioned with our bivariate binomial model meet the target within 0.2-dB signal-to-noise ratio.
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| 23. |
- Leong, Miu Yoong, et al.
(författare)
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Dimensioning RS codes for mitigation of phase noise induced cycle slips in DQPSK systems
- 2014
-
Ingår i: Asia Communications and Photonics Conference, ACP. - Washington, D.C. : Optical Society of America. - 9781557528520
-
Konferensbidrag (refereegranskat)abstract
- We present a semi-analytical method for dimensioning Reed-Solomon codes for coherent DQPSK systems with laser phase noise and cycle slips. We evaluate the accuracy of our method for a 28 Gbaud system using numerical simulations.
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| 24. |
- Leong, Miu Yoong, et al.
(författare)
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Interleavers and BCH Codes for Coherent DQPSK Systems With Laser Phase Noise
- 2015
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 27:7, s. 685-688
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Tidskriftsartikel (refereegranskat)abstract
- The relatively high phase noise of coherent optical systems poses unique challenges for forward error correction (FEC). In this letter, we propose a novel semianalytical method for selecting combinations of interleaver lengths and binary Bose-Chaudhuri-Hocquenghem (BCH) codes that meet a target post-FEC bit error rate (BER). Our method requires only short pre-FEC simulations, based on which we design interleavers and codes analytically. It is applicable to pre-FEC BER similar to 10(-3), and any post-FEC BER. In addition, we show that there is a tradeoff between code overhead and interleaver delay. Finally, for a target of 10(-5), numerical simulations show that interleaver-code combinations selected using our method have post-FEC BER around 2x target. The target BER is achieved with 0.1 dB extra signal-to-noise ratio.
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| 25. |
- Leong, Miu Yoong, et al.
(författare)
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Low-complexity BCH codes with optimized interleavers for DQPSK systems with laser phase noise
- 2017
-
Ingår i: Photonic network communications. - : Springer Science and Business Media LLC. - 1387-974X .- 1572-8188. ; 33:3, s. 328-333
-
Tidskriftsartikel (refereegranskat)abstract
- The presence of high phase noise in addition to additive white Gaussian noise in coherent optical systems affects the performance of forward error correction (FEC) schemes. In this paper, we propose a simple scheme for such systems, using block interleavers and binary Bose-Chaudhuri-Hocquenghem (BCH) codes. The block interleavers are specifically optimized for differential quadrature phase shift keying modulation. We propose a method for selecting BCH codes that, together with the interleavers, achieve a target post-FEC bit error rate (BER). This combination of interleavers and BCH codes has very low implementation complexity. In addition, our approach is straightforward, requiring only short pre-FEC simulations to parameterize a model, based on which we select codes analytically. We aim to correct a pre-FEC BER of around . We evaluate the accuracy of our approach using numerical simulations. For a target post-FEC BER of , codes selected using our method result in BERs around 3 target and achieve the target with around 0.2 dB extra signal-to-noise ratio.
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| 26. |
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| 27. |
- Maes, Dirk, et al.
(författare)
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Integrating national Red Lists for prioritising conservation actions for European butterflies
- 2019
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Ingår i: Journal of Insect Conservation. - : Springer Science and Business Media LLC. - 1366-638X .- 1572-9753. ; 23:2, s. 301-330
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Tidskriftsartikel (refereegranskat)abstract
- Red Lists are very valuable tools in nature conservation at global, continental and (sub-) national scales. In an attempt to prioritise conservation actions for European butterflies, we compiled a database with species lists and Red Lists of all European countries, including the Macaronesian archipelagos (Azores, Madeira and Canary Islands). In total, we compiled national species lists for 42 countries and national Red Lists for 34 of these. The most species-rich countries in Europe are Italy, Russia and France with more than 250 species each. Endemic species are mainly found on the Macaronesian archipelagos and on the Mediterranean islands. By attributing numerical values proportionate to the threat statuses in the different national Red List categories, we calculated a mean Red List value for every country (cRLV) and a weighted Red List value for every species (wsRLV) using the square root of the country’s area as a weighting factor. Countries with the highest cRLV were industrialised (NW) European countries such as the Netherlands, Belgium, the Czech Republic and Denmark, whereas large Mediterranean countries such as Spain and Italy had the lowest cRLV. Species for which a Red List assessment was available in at least two European countries and with a relatively high wsRLV (≥ 50) are Colias myrmidone, Pseudochazara orestes, Tomares nogelii, Colias chrysotheme and Coenonympha oedippus. We compared these wsRLVs with the species statuses on the European Red List to identify possible mismatches. We discuss how this complementary method can help to prioritise butterfly conservation on the continental and/or the (sub-)national scale.
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| 28. |
- Milinsky, Alexey, et al.
(författare)
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Determination of the amount of heat for partially elastic impact using the smartphone
- 2021
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Ingår i: Физика: фундаментальные и прикладные исследования, образование.. - Blagoveshchensk : Амурский государственный университет. - 9785934933761 ; , s. 144-147
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Konferensbidrag (refereegranskat)abstract
- The article presents a creative experimental task for students to determine the amount of heat with a partially elastic impact. The experiment is carried out using a smartphone, which makes the experiment simple and convenient for conducting at home
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| 29. |
- Osipov, Evgeny, et al.
(författare)
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Effect of the L499M mutation of the ascomycetous Botrytis aclada laccase on redox potential and catalytic properties
- 2014
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Ingår i: Acta Crystallographica Section D. - : International Union of Crystallography. - 0907-4449 .- 1399-0047. ; 70:11, s. 2913-2923
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Tidskriftsartikel (refereegranskat)abstract
- Laccases are members of a large family of multicopper oxidases that catalyze the oxidn. of a wide range of org. and inorg. substrates accompanied by the redn. of dioxygen to water. These enzymes contain four Cu atoms per mol. organized into three sites: T1, T2 and T3. In all laccases, the T1 copper ion is coordinated by two histidines and one cysteine in the equatorial plane and is covered by the side chains of hydrophobic residues in the axial positions. The redox potential of the T1 copper ion influences the enzymic reaction and is detd. by the nature of the axial ligands and the structure of the second coordination sphere. In this work, the laccase from the ascomycete Botrytis aclada was studied, which contains conserved Ile491 and nonconserved Leu499 residues in the axial positions. The three-dimensional structures of the wild-type enzyme and the L499M mutant were detd. by X-ray crystallog. at 1.7 Å resoln. Crystals suitable for X-ray anal. could only be grown after deglycosylation. Both structures did not contain the T2 copper ion. The catalytic properties of the enzyme were characterized and the redox potentials of both enzyme forms were detd.: E 0 = 720 and 580 mV for the wild-type enzyme and the mutant, resp. Since the structures of the wild-type and mutant forms are very similar, the change in the redox potential can be related to the L499M mutation in the T1 site of the enzyme.
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| 30. |
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| 31. |
- Pang, Xiaodan, Dr., et al.
(författare)
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Experimental Evaluation of Impairments in Unrepeatered DP-16QAM Link with Distributed Raman Amplification
- 2017
-
Ingår i: Photonics. - : MDPI AG. - 2304-6732. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- The transmission impairments of a Raman amplified link using dual-polarization 16-quadrature amplitude modulation (DP-16QAM) are experimentally characterized. The impact of amplitude and phase noise on the signal due to relative intensity noise (RIN) transfer from the pump are compared for two pumping configurations: first-order backward pumping and bi-directional pumping. Experimental results indicate that with increased Raman backward pump power, though the optical signal-to-noise ratio (OSNR) is increased, so is the pump-induced amplitude and phase noise. The transmission performance is firstly improved by the enhanced OSNR at a low pump power until an optimum point is reached, and then the impairments due to pump-induced noise start to dominate. However, the introduction of a low pump power in the forward direction can further improve the system's performance.
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| 32. |
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| 33. |
- Pang, Xiaodan, Dr., et al.
(författare)
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Experimental Evaluation of Noise Impairments in Unrepeated Distributed Raman Amplified DP-16QAM SSMF Links
- 2015
-
Ingår i: Progress In Electromagnetics Research Symposium Abstracts. - 9781934142295 ; , s. 131-131
-
Konferensbidrag (refereegranskat)abstract
- Unrepeated fiber transmissions over hundreds of kilometers span with advanced modulation formats and DSP-based coherent detection schemes are considered as a potential candidate to meet the distance and capacity requirements in certain application scenarios where render amplification sites between terminals are impractical due to geographic, commercial or security constrains [1]. Distributed Raman fiber amplifier (DFRA) ensuring a relatively constant power distribution of the optical signals along links can effectively improve the system OSNR and fiber nonlinearity tolerance, therefore is widely adopted in unrepeated transmission solutions. To date, unrepeated transmissions of 30 Gbaud DP-QPSK over 444 km [2], single and dual carrier 28 Gbaud DP-16QAM over 240 km [3, 4] have been demonstrated by using Raman amplification with large effective area fibers (LEAF). In this paper we report on a systematic experimental characterization of both the amplitude and phase impairments of the received signal induced by a bidirectional Raman pump at 1455 nm with an evaluation of the coherent transmission performances of a 28 Gbaud DP-16QAM signal in a standard single mode fiber (SSMF). The Raman induced amplitude and phase noise on the received 1550 nm signal is directly measured and the discussions around the operational rules and limitations are presented considering the inter-relation between pump power, signal OSNR and induced noise. Furthermore, performances of different carrier phase recovery algorithms, including decision-directed phase-locked-loop (DDPLL) [5], blind phase search (BPS) [6] and a two-stage QPSK partitioning [7] with variable filtering implementations in the DSP routine are investigated taking into account the specific noise profile of the received signal.
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| 34. |
- Pankratov, Dmitry, et al.
(författare)
-
A comparative study of biocathodes based on multiwall carbon nanotube buckypapers modified with three different multicopper oxidases
- 2013
-
Ingår i: Electroanalysis. - : Wiley-VCH Verlagsgesellschaft. - 1040-0397 .- 1521-4109. ; 25:5, s. 1143-1149
-
Tidskriftsartikel (refereegranskat)abstract
- 14 Single- and multi-walled carbon nanotubes from different sources were characterized in detail, and the characteristics obtained were carefully analyzed. The carbon material with the highest capacitance, and also other superior properties ("Taunit-M" from "NanoTechCenter", Russia), was chosen for further modification and fabrication of buckypaper based electrodes. These electrodes were biomodified with plant and fungal laccases, as well as fungal bilirubin oxidase. The designed biocathodes were studied in simple buffers and also in a complex physiol. fluid (human serum). Biocathodes based on immobilized fungal laccase were bioelectrocatalytically inactive in chloride contg. media at neutral pH. In spite of the quite high current densities realized using biodevices based on plant laccase and fungal bilirubin oxidase, the limited thermal stability of the enzymes renders the biocathodes inadequate for practical applications in implanted situations.
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| 35. |
- Pankratov, Dmitry, et al.
(författare)
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Impact of surface modification with gold nanoparticles on the bioelectrocatalytic parameters of immobilized bilirubin oxidase
- 2014
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Ingår i: Acta Naturae. - : Park Media Ltd. - 2075-8251. ; 6:1, s. 102-106
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Tidskriftsartikel (refereegranskat)abstract
- We unveil experimental evidence that put into question the widely held notion concerning the impact of nanoparticles on the bioelectrocatalytic parameters of enzymatic electrodes. Comparative studies of the bioelectrocatalytic properties of fungal bilirubin oxidase from Myrothecium verrucaria adsorbed on gold electrodes, modified with gold nanoparticles of different diameters, clearly indicate that neither the direct electron transfer rate (standard heterogeneous electron transfer rate constants were calculated to be 31±9 s-1) nor the biocatalytic activity of the adsorbed enzyme (bioelectrocatalytic constants were calculated to be 34±11 s-1) depends on the size of the nanoparticles, which had diameters close to or larger than those of the enzyme molecules.
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| 36. |
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| 37. |
- Popov, Oleg, 1959-, et al.
(författare)
-
Att studera energiomvandlingar med hjälp av en smarttelefon
- 2021
-
Ingår i: LMNT-nytt. - : Föreningen för lärarna i matematik, naturvetenskap och teknik (LMNT). - 1402-0041. ; :2, s. 34-36
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Artikeln presenterar en kreativ experimentell uppgift för elever att bestämma mängden värme som produceras under en oelastisk stöt. Experimentet utförs med hjälp av en smartphone, vilket gör att resultatet har en hög precision. Tydlig visualisering och tillgänglighet när det gäller använd utrustning visar på ämnesdidaktiska fördelar.
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| 38. |
- Popov, Oleg, 1959-, et al.
(författare)
-
Developing toools for mobile learning to enhance science teachers´professional competence
- 2021
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Ingår i: Физика: фундаментальные и прикладные исследования, образование. - Blagoveshchensk : Амурский государственный университет. - 9785934933761 ; , s. 150-153
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Konferensbidrag (refereegranskat)abstract
- Raising quality of science specialists and science education is a major priority around the globe. Another important global educational focus is promoting sustainable development. Use of modern mobile learning tools and teaching approaches shows great promises for teacher education in fulfilling these goals. This paper presents theoretical foundations and some practical solutions how smartphones as handheld computers can assist mobile learning (m-learning) in geographically distributed settings. The developmental work is conducted within the framework of InterMobile project that is presented in the paper where also some expected and achieved outcomes outlined.
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| 39. |
- Popov, Sergei, et al.
(författare)
-
Efficiency enhancement in a microcavity solid-state dye laser with Bragg grating reflectors
- 2010
-
Ingår i: Central European Journal of Physics. - : Walter de Gruyter GmbH. - 1895-1082 .- 1644-3608. ; 8:2, s. 202-206
-
Tidskriftsartikel (refereegranskat)abstract
- Bragg grating reflectors placed along microcavity facets can improve the efficiency of a polymer dye laser built with such a microcavity. The impact of different reflector designs on the mode pattern and resonance frequencies of the microcavity is numerically simulated and analyzed. This rigorous physical model is based on solving the Maxwell equations and includes such material properties as absorption, dispersion, fluorescence and optical gain. In certain cases, an asymmetrical layout of the reflectors can be more preferable than the pair of reflectors located on opposite sides of the microcavity as it is implemented for typical design.
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| 40. |
- Popov, Sergei, et al.
(författare)
-
Even-mode generation in microcavity dye laser
- 2007
-
Ingår i: ICONO 2007: Coherent And Nonlinear Optical Phenomena. - : SPIE. - 9780819468864 ; , s. M7292-M7292
-
Konferensbidrag (refereegranskat)abstract
- A solid-state dye laser with a microcavity whose size is comparable to the lasing wavelength is modeled by means of the finite element method. The position of the pumping source affects the lasing mode spectrum. In comparison with a single point source at the edge of the cavity, a random distribution of excitation sources in the central gain part of the microcavity leads to depletion of odd longitudinal modes and to higher output efficiency of the laser radiation in even modes. The simulation results are explained by simple physical considerations.
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| 41. |
- Popov, Sergei, et al.
(författare)
-
External near-field resonance in coupled microcavities : mode enhancement and applications
- 2010
-
Ingår i: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010. - 9781424471119 ; , s. 90-91
-
Konferensbidrag (refereegranskat)abstract
- Interference of the near optical field caused by evanescent waves leaking a coupled microcavity enhances the optical field between the cavity sections. This enhancement can be used for design of microcavity lasers with outside-cavity modes and for various sensors, for example, to precisely detect the direction of incident wavefront.
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| 42. |
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| 43. |
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| 44. |
- Popov, Sergei, et al.
(författare)
-
Mode suppression in a microcavity solid-state dye laser
- 2007
-
Ingår i: Journal of the European Optical Society-Rapid Publications. - : European Optical Society. - 1990-2573. ; 2, s. 07203-
-
Tidskriftsartikel (refereegranskat)abstract
- A solid-state dye laser with a microcavity whose size is comparable to the lasing wavelength, is modeled by means of the finite element method. The position of the pumping source affects the lasing mode spectrum. In comparison with a single point source at the edge of the cavity, a random distribution of excitation sources in the central gain part of the microcavity leads to suppression of odd longitudinal modes and to higher output efficiency of the laser radiation in even modes. The modeling and simulation results are explained by simple physical considerations.
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| 45. |
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| 46. |
- Popov, Sergei, et al.
(författare)
-
Terahertz Near-field Imaging : Rigorous Model for Interpreting "Antenna approach"
- 2009
-
Ingår i: 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS 2009. - Washington, D.C. : IEEE. - 9781424451845 ; , s. 3027-3028
-
Konferensbidrag (refereegranskat)abstract
- Classical Mie theory fails to explain high resolution of a terahertz imaging system exploiting scattering of the near-field radiation. Reported numerical model confirms the feasibility of an antenna model which proves the enhanced resolution.
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| 47. |
- Ricciardi, Sebastien, et al.
(författare)
-
Thermally induced wavelength tunability of microcavity solid-state dye lasers
- 2007
-
Ingår i: Optics Express. - 1094-4087. ; 15:20, s. 12971-12978
-
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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| 48. |
- Ricciardi, Sébastien, et al.
(författare)
-
Thermo-tuning and energy redistribution in microcavity solid-state dye lasers
- 2008
-
Ingår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY. - Bristol : IOP PUBLISHING LTD.
-
Konferensbidrag (refereegranskat)abstract
- Wavelength tunability of a microcavity solid-state dye laser is modeled by the finite element method (FEM). We investigate the combination of thermoelastic expansion and thermo-optic effects to tune the microcavity resonant wavelength. An optimized size of the laser microcavity is defined depending on the operation wavelength bandwidth and the glass temperature of the gain material. We also report a new effect of mode depletion specific to our microcavity and excitation scheme.
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| 49. |
- Ricciardi, Sebastien, et al.
(författare)
-
Tunable microcavity solid-state dye laser for biometrics applications
- 2007
-
Ingår i: ICONO 2007: Coherent And Nonlinear Optical Phenomena. - : SPIE. - 9780819468864 ; , s. N7292-N7292
-
Konferensbidrag (refereegranskat)abstract
- Wavelength tunability of a microcavity solid-state dye laser is modeled by means of the finite element method. We investigate the application of two phenomena, thermoelastic expansion of the microcavity material and thermo-induced change of refractive index, in order to tune microcavity mode frequencies by the variation of the effective optical path. An optimized size of the laser microcavity is defined depending on the operation wavelength bandwidth and the glass temperature of the gain material.
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| 50. |
- Rosa, Pawel, et al.
(författare)
-
Unrepeatered 64QAM over SMF-28 using Raman Amplification and Digital Backpropagation
- 2017
-
Ingår i: Asia Communications and Photonics Conference, ACP. - : OSA - The Optical Society. - 9781943580347
-
Konferensbidrag (refereegranskat)abstract
- Unrepeatered transmission over SMF-28 fibre is investigated using Raman based amplification. Experiments and simulations demonstrate a transmission up to 200 km (41 dB) span length using 28Gbaud 64 QAM modulation employing digital back propagation in DSP. © OSA 2017.
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