ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    First-order polarization-activated optical transitions in smecticC and planar nematic liquid crystals (1989)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 11 (1989), S. 385-392 
    Details
    ISSN: 0392-6737
    Keywords: Liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto È stato mostrato che, quando un fascio di luce laser interagisce con campioni di cristallo liquido smetticoC o nematico con allineamento planare, è possibile ottenere transizioni del primo ordine della polarizzazione della luce di uscita in funzione della polarizzazione della luce incidente. Queste transizioni danno luogo a cicli di isteresi e bistabilità ottica intrinseca, senza l'intervento di feed-back esterni né di campi statici di polarizzazione. È stato risolto esattamente, in condizioni stazionarie, un sistema di equazioni differenziali nonlineari che governa l'evoluzione del direttore molecolare e dello stato di polarizzazione della luce lungo il campione. I risultati ottenuti sono indipendenti dai valori delle costanti ottiche e meccaniche dei campioni di cristallo liquido. L'intensità della luce per cui si ottengono fenomeni di bistabilità ottica varia da 10 kW/cm2 a 1 MW/cm2 circa.
    Abstract: Резюме Показывается, что поляризация, активированная внутренней ортической биустойчивостью, может быть получена в жидких кристаллах типа смектика-C и типа плоского неиатика без резонатора с внешней обратной связью. Доказывается, что, в принципе, возникают переходы первого порядка, независимо от постоянных жидких кристаллов. Интенсивность света, необходимая для получения оптической биустойчивости, находится в области от 10 кВт/см2 до 1 МВт/м2.
    Notes: Summary It is shown that polarization-activated intrinsic optical bistability (OB) may be obtained in smecticC or planar nematic liquid crystals without external feed-back resonator. First-order transitions for twist are proved to occur, in principle, irrespective of the liquid-crystal material constants. The light intensity, needed to obtain OB, ranges from 10 kW/cm2 to 1 MW/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02450988
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Optical Freedericksz transitions in twisted planar nematics (1988)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 10 (1988), S. 313-322 
    Details
    ISSN: 0392-6737
    Keywords: Orientational order of liquid crystals ; electric and magnetic field effects of order
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è studiata la propagazione di un fascio di luce polarizzata ellitticamente che incide normalmente su un campione di cristallo liquido nematico planare «twisted», cioè nel quale l'angolo α fra la direzione delle molecole nel piano di ingresso della luce e quella nel piano di uscita è≠O. È stato derivato un sistema non lineare di equazioni differenziali che governa l'evoluzione del direttore molecolare e dello stato di polarizzazione della luce. Questo sistema è stato risolto analiticamente nel limite di piccole variazioni intorno a soluzioni corrispondenti allo stato imperturbato. Si è dimostrato che transizioni di Freedericksz ottiche sono possibili solo se la luce incidente si trova in un particolare stato di polarizzazione. I risultati ottenuti sono peculiari dell'interazione ottica e non sono riconducibili al fenomeno della riorientazione molecolare indotta su campioni di questo tipo da campi statici, elettrici o magnetici.
    Abstract: Резюме Мы исследуем распространение эллипчески поляриэованного светового пучка, падаюшего номально на пленку эакрученного нематического жидкого кристалла. Выводится система нелинейных дифференциальиых уравнений для молекулярного директора и поляриэации светового пучка. Полуенная система решается аналитчески в пределе малЫх воэмущений относительно решений для стционарнЫх состояний, которЫе соответствуют не-переориентированному обраэцы. МЫ докаэЫваем, что оптические перехоые фредерикса воэможиы только для частично поляриэованного состояния падаюшего света. Исследуется пороповое поведение как функция интенсвности света и упла эакручивания между молекуляриыми директорами на стенках обраэца. Полученные реэультаты являются характерными для оптического вэаимодействия и не имеют аналога при молекулярной переориентации, индуцрованной в такой системе d.c. полями.
    Notes: Summary We study the propagation of an elliptically polarized light beam normally incident onto a twisted nematic liquid-crystal film. A set of nonlinear differential equations for the molecular director and the polarization of the light beam is derived; it is solved analytically in the limit of small perturbations around the steady-state solutions that represent the nonreoriented sample. We prove that optical Freedericksz transitions are possible only for a particular polarization state of the incident light. The threshold behaviour is studied as a function of the light intensity and of the twist angle between the molecular directors at the sample walls. The results are characteristic of the optical interaction and have no analogue in the molecular reorientation induced on such a system by d.c. fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02450121
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    AC conductivity of porous silicon: A fractal and surface transport mechanism? (1996)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 1187-1196 
    Details
    ISSN: 0392-6737
    Keywords: Optoelectronic devices ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary In this paper we report on the frequency dependence of the AC conductivity of porous silicon in the range 10 Hz-100 kHz. Two types of testing devices have been fabricated on three different series of samples formed electrochemically using as a starting materialptype,n −-type andn +-type silicon substrates. For frequencies less than 20-40 kHz the conductivity is found to follow a sublinear frequency dependence. This behaviour is typical of a carrier transport mechanism determined by an anomalous diffusion process. At higher frequencies we find that surface states influence the transport mechanism. This suggests a double-channel transport mechanism: one related to porous-silicon “volume” properties and the other more connected to the “surface” itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02464696
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    A new approach to global stability analysis of one-dimensional continuous dissipative systems (1990)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 31 (1990), S. 2105-2115 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: It is proved by a direct construction that symmetry-breaking instabilities in one-dimensional dissipative continuous systems can be studied in terms of a suitable function G whose minima correspond to stable steady states of the system, while other extremal points correspond to unstable states. The existence of such a function is proved for a large class of continuous dissipative physicochemical systems in one spatial dimension. The function G is exact, in the sense that it is obtained by taking into account all nonlinear terms in the evolution equations of the system. Since in some respect this function has properties similar to the Ginzburg–Landau function widely used in second-order phase transitions, it is called the nonlinear Ginzburg–Landau function (NLGLF) of the system. The NLGLF may be useful for studying the global stability under symmetry-breaking conditions as well as the character (first and second order) of the transitions between different steady states. The construction of the NLGLF usually requires simple numerical or analytical calculations. A specific example, taken from the physics of liquid crystals, has been worked out analytically in the present paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528663
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Role of guest-host intermolecular forces in photoinduced reorientation of dyed liquid crystals (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9783-9793 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An experimental study of the photoinduced molecular reorientation of dyed liquid crystals for a set of guest-host combinations is reported. We find large variations in the magnitude of the effect for different dyes but also for different hosts, with polar hosts resulting often significantly more effective than nonpolar ones. The data are interpreted in terms of a kinetic mean-field model for the dye molecule rotational dynamics and interaction with the liquid crystal host. The results point to a significant variation of guest-host intermolecular forces upon photoinduced electronic excitation of dye molecules. This force variation is reflected in a variation of dye molecule physical parameters such as the rotational friction coefficient and the orientational mean-field energy. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475276
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Polarization effects in the optical reorientation of freely suspended smectic-C liquid-crystal films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1269-1274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A linearly polarized laser beam propagating in a freely suspended smectic-C liquid-crystal film can induce reorientation of the molecular director. A theoretical model is presented which, unlike previous works, takes into account the effects of the polarization changes of the light into the sample. Despite the nonlinearity of the problem, an analytical solution is found. The stability analysis of the trivial solutions has also been carried out. A physical interpretation of the results, some of which are unexpected on the basis of the old models, is given in terms of angular momentum conservation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348907
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Nonresonant Kerr effect in microporous silicon: Nonbulk dispersive behavior of below band gap χ(3)(ω) (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5564-5570 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Although in recent years resonant optical nonlinearities in quantum confined silicon generated significant interest, no experimental work has been dedicated to the nonresonant regime, which is the range of interest for optical switching applications. In this article we report a systematic investigation on the different types of optical nonlinearities which can be activated in quantum-sized silicon. In particular, original measurements of nonresonant nonlinear refraction (Kerr effect) are reported at different wavelengths, spanning the infrared middle-gap range. The dispersive scaling rule and values of the nonlinear refractive index are clearly incompatible with those of three-dimensional semiconductors. Hence the quantum confined density of states plays a key role in determining the frequency dispersion of the nonresonant third-order susceptivity χ(3)(ω). Also, this suggests the need of further investigation of the influence of quantum-size effects (and related density of states modifications) on below-gap χ(3). © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467606
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Interferometric technique for the determination of thermal nonlinearities in semiconductor glasses
    Amsterdam : Elsevier
    Optics Communications 70 (1989), S. 502-508 
    Details
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0030-4018(89)90373-8
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Experimental investigation of lateral wave contribution to the shift of a reflected beam at surface plasmon resonance
    Amsterdam : Elsevier
    Optics Communications 96 (1993), S. 221-224 
    Details
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0030-4018(93)90264-6
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Detection of surface electromagnetic waves by reflected intensity distribution measurements
    Amsterdam : Elsevier
    Optics Communications 46 (1983), S. 284-289 
    Details
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0030-4018(83)90006-8
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...