Coupling of emitters to surface plasmons investigated by back focal plane microscopy

Current efforts in the field of plasmonics towards device integration and miniaturization require detailed knowledge about the coupling between surface plasmons and emitters. In this work coupling between surface plasmon polaritons and different emitter systems has been investigated by the technique of back focal plane imaging. To develop a deeper understanding of the interaction phenomena the studies focused on single emitters in elementary plasmonic configurations that allow for an analytical description. The first part of the thesis reports on the successful demonstration of surface plasmon polaritons launched by a single dipolar carbon nanotube emitter on a metal thin film after local optical excitation. Leakage radiation microscopy images, recorded in the back focal plane of a microscope objective, could be modeled successfully and contained the propagation length and direction of surface plasmon polaritons. Corresponding real-space images revealed plasmon propagation away from the single dipolar plasmon source. The polarization behavior of surface plasmon polaritons launched by single carbon nanotubes was found to be radial as predicted by theoretical calculations. Remote excitation of single walled carbon nanotube excitons via propagating surface plasmons is demonstrated in the second part. A scanning aperture probe was used as source for propagating surface plasmons with fine controllability over excitation position and propagation direction. It was raster scanned in close proximity over a single carbon nanotube located on a metal film while recording the emission response from the nanotube. The carbon nanotube showed an emission response while the aperture plasmon source was still far away from the nanotube position. Theoretical modeling of the excited surface plasmon fields confirmed that the nanotube maps the surface plasmons locally with sub-diffraction resolution. In the last part, radiation channels in the vicinity of a plasmonic nanowire were investigated. Radiation patterns of a coupled system of rare earth nanocrystals and silver nanowires in the back focal plane revealed that the emission in the vicinity of a nanowire can be approximately described by two emission channels that can be calculated analytically: Dipolar emission, also observed in the absence of the nanowire, and leakage radiation from the nanowire. The latter can be calculated using an antenna-resonator model that considers the air-dielectric interface on which the nanowire is deposited and the position of excitation along the nanowire. Fitting of the experimentally observed patterns provides estimates for the branching ratio between the two emission channels and further enable the determination of the plasmon wave-vector supported by the nanowires

Antenna-enhanced Optoelectronic Probing of Carbon Nanotubes

We report on the first antenna-enhanced optoelectronic microscopy studies on nanoscale devices. By coupling the emission and excitation to a scanning optical antenna, we are able to locally enhance the electroluminescence and photocurrent along a carbon nanotube device. We show that the emission source of the electroluminescence can be point-like with a spatial extension below 20 nm. Topographic and antenna-enhanced photocurrent measurements reveal that the emission takes place at the location of highest local electric field indicating that the mechanism behind the emission is the radiative decay of excitons created via impact excitation

Etika

Publikacijoje nagrinėjamos svarbiausios etikos problemos: etikos statusas, gėrio samprata, privalėjimo, dorybių, vertybių, laisvės, laimės ir kt. klausimai. Pagrindiniais etikos klausimais laikomi privalėjimo ir gėrio klausimai. Kritikuojamos eudemonistinės etikos sistemos, laimę siejančios su malonumu. Gėris apibūdinamas kaip dorybės vertybių turinys, kuris pats savaime yra vertingas. Aptariama Aristotelio vertybių samprata: dorybė yra dviejų vertybių sintezė. Vertybių problemos raida etikoje prasidėjo su F. Nietzsche ir tik XX a. pradžioje ši problematika sėkmingai plėtojama M. Schelerio veikaluose. Pristatomas vertybių reliatyvumo principas. Dorovės vertė nukreipta į asmenį dvejopa prasme – kaip į subjektą (aktyviai) ir kaip į objektą (pasyviai). Dorovės vertybės skiriasi nuo gėrybių vertės – pastarosios susiję su daiktais. Kategorinis imperatyvas susijęs tik su elementariųjų normų dorove. Pateikiama vertybių hierarchija (malonumų, gėrybių, vitalinės, dorovinės vertybės), gėris apibrėžiamas kaip aukštesniųjų vertybių teleologija. Aptariama I. Kanto laisvės samprata, analizuojamos laisvės problemos antinomijos. Teigiama, kad valios laisvė yra galima tik pozityviam protui

Kantas (sisteminis išdėstymas)

Publikuojamame N. Hartmanno straipsnio vertime glaustai išdėstyti I. Kanto filosofijos esminiai požymiai, kurie susiję su pažinimo raidos aiškinimu filosofijoje. Vaidingumo dėlei pateikta keletas schemų: transcendentalinės sąmonės, transcendentalinio idealizmo, kategorijų, sprendinių lentelės, reiškinių ir daiktų savaime sąveikos ir žmogaus padėties pasaulyje. Transcendentalinė estetika grindžiama tuo, kad erdvė ir laikas yra laikomi aprioriniais mūsų pojūčių principais. Spręsdamas kategorijų objektyvaus galiojimo problemą I. Kantas remiasi žmogiškąja subjekto sfera, kurią jis vadina empirine sąmone arba empiriniu subjektu. Kiekviename pažinimo akte vyksta trejopa sintezė: įvairių jutiminių įspūdžių sintezė stebinyje, reprodukcijos sintezė vaizduotėje, atpažinimo sintezė sąvokoje. Aptariamos substancijos ir priežastingumo kategorijos, analizuojamos grynojo proto antinomijos, I. Kanto ontologinio Dievo buvimo įrodymo kritika, tikslingumo samprata, žmogaus, kaip dorovinės esybės, pozicija pasaulyje. Pateikiamas dvejopas sprendimo galios apibrėžimas: ji yra apibrėžiančioji ir reflektuojančioji

Coupling of emitters to surface plasmons investigated by back focal plane microscopy

Current efforts in the field of plasmonics towards device integration and miniaturization require detailed knowledge about the coupling between surface plasmons and emitters. In this work coupling between surface plasmon polaritons and different emitter systems has been investigated by the technique of back focal plane imaging. To develop a deeper understanding of the interaction phenomena the studies focused on single emitters in elementary plasmonic configurations that allow for an analytical description. The first part of the thesis reports on the successful demonstration of surface plasmon polaritons launched by a single dipolar carbon nanotube emitter on a metal thin film after local optical excitation. Leakage radiation microscopy images, recorded in the back focal plane of a microscope objective, could be modeled successfully and contained the propagation length and direction of surface plasmon polaritons. Corresponding real-space images revealed plasmon propagation away from the single dipolar plasmon source. The polarization behavior of surface plasmon polaritons launched by single carbon nanotubes was found to be radial as predicted by theoretical calculations. Remote excitation of single walled carbon nanotube excitons via propagating surface plasmons is demonstrated in the second part. A scanning aperture probe was used as source for propagating surface plasmons with fine controllability over excitation position and propagation direction. It was raster scanned in close proximity over a single carbon nanotube located on a metal film while recording the emission response from the nanotube. The carbon nanotube showed an emission response while the aperture plasmon source was still far away from the nanotube position. Theoretical modeling of the excited surface plasmon fields confirmed that the nanotube maps the surface plasmons locally with sub-diffraction resolution. In the last part, radiation channels in the vicinity of a plasmonic nanowire were investigated. Radiation patterns of a coupled system of rare earth nanocrystals and silver nanowires in the back focal plane revealed that the emission in the vicinity of a nanowire can be approximately described by two emission channels that can be calculated analytically: Dipolar emission, also observed in the absence of the nanowire, and leakage radiation from the nanowire. The latter can be calculated using an antenna-resonator model that considers the air-dielectric interface on which the nanowire is deposited and the position of excitation along the nanowire. Fitting of the experimentally observed patterns provides estimates for the branching ratio between the two emission channels and further enable the determination of the plasmon wave-vector supported by the nanowires

Žmogaus padėtis pasaulyje

Straipsnyje nagrinėjamos žmogaus sąmonės formos, žmogiškosios veiklos savitumo aspektai. Žmogui būdingi transcendentalūs aktai ir įvairialypė veikla. Žmogaus norai, valios veiksmai, savęs suvokimas bei įvairūs rūpesčiai peržengia jo sąmonės ribas. Sąmonės dėka žmogus išsivaduoja iš gyvuliškųjų poreikių nelaisvės, dirbdamas jis kuria kultūrą. Žmogaus dvasia perkuria daiktų pasaulį pagal savo tikslus, to negali pati gamta. Žmogaus pranašumas yra ne ontinis, o tik pažintinis, jam būdingas sąmoningas prisitaikymas ir tikslingas vertinimas. Vertybės yra orientuotos į konkrečią būtybę, jomis ji save teigia ir tokiu pavidalu dalyvauja realiame pasaulyje. Žmogus yra vertybių kūrėjas ir vienintelis jų suvokėjas bei įgyvendintojas. Jei vertybės galėtų realizuotis pačios savaime, tai žmogus būtų nereikalingas

Laiškai V. Sezemanui

Publikuojami du N. Hartmanno laiškai V. Sezemanui ir vienas – jo žmonai. Pateikiamas tekstas originalo (vokiečių) kalba ir jo vertimas į lietuvių kalbą. Laiškuose teiraujamasi dėl straipsnio vertimo filosofiniam žurnalui, supažindinama su filosofinių tekstų jubiliejinės rinktinės sudarymo problemomis, išreiškiamos asmeninės simpatijos ir linkėjimai, dalijamasi mokslinio darbo rūpesčiais, aktualiais sprendžiamais filosofiniais klausimais, pripažįstama didelė bendravimo su V. Sezemanu intelektualinė nauda

In-plane remote photoluminescence excitation of carbon nanotube by propagating surface plasmon

In this work, we demonstrate propagating surface plasmon polariton (SPP) coupled photoluminescence (PL) excitation of single-walled carbon nanotube (SWNT). SPPs were launched at a few micrometers from individually marked SWNT, and plasmon-coupled PL was recorded to determine the efficiency of this remote in-plane addressing scheme. The efficiency depends upon the following factors: (i) longitudinal and transverse distances between the SPP launching site and the location of the SWNT and (ii) orientation of the SWNT with respect to the plasmon propagation wave vector (k SPP). Our experiment explores the possible integration of carbon nanotubes as a plasmon sensor in plasmonic and nanophotonic devices

Enhancing and redirecting carbon nanotube photoluminescence by an optical antenna

We observe the angular radiation pattern of single carbon nanotubes' photoluminescence in the back focal plane of a microscope objective and show that the emitting nanotube can be described by a single in-plane point dipole. The near-field interaction between a nanotube and an optical antenna modifies the radiation pattern that is now dominated by the antenna characteristics. We quantify the antenna induced excitation and radiation enhancement and show that the radiative rate enhancement is connected to a directional redistribution of the emission