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14 Aug 2000

Volume 77, Issue 7, pp. 921-1064

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Reversible optical structuring of polymer waveguides doped with photochromic molecules

S. Lecomte, U. Gubler, M. Jäger, Ch. Bosshard, G. Montemezzani, P. Günter, L. Gobbi, and F. Diederich

Appl. Phys. Lett. 77, 921 (2000); http://dx.doi.org/10.1063/1.1288598 (3 pages) | Cited 20 times

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We show that polymeric films doped with the photochromic molecule 1,8a-dihydro-2(4-iodophenyl)-1,1-azulenedicarbonitrile can be reversibly structured by light. We discuss the relevant material properties of the photochromic molecule in solution as well as in polymer films and demonstrate light-induced waveguides at the telecommunication wavelength of 1.313 μm. © 2000 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.70.Jk Polymers and organics
78.66.Qn Polymers; organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Adaptive feedback control of ultrafast semiconductor nonlinearities

J. Kunde, B. Baumann, S. Arlt, F. Morier-Genoud, U. Siegner, and U. Keller

Appl. Phys. Lett. 77, 924 (2000); http://dx.doi.org/10.1063/1.1288603 (3 pages) | Cited 38 times

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We experimentally demonstrate that adaptive feedback optical pulse shaping can be used to control ultrafast semiconductor nonlinearities. The control scheme is based on an evolutionary algorithm, which directs the modulation of the spectral phase of 20 fs laser pulses. The algorithm has optimized the broadband semiconductor continuum nonlinearity measured in differential transmission experiments. Our results show that insight into light–semiconductor interaction is obtained from the optimum laser pulse shape even if the interaction is too complex to predict this shape a priori. Moreover, we demonstrate that adaptive feedback control can substantially enhance ultrafast semiconductor nonlinearities by almost a factor 4. © 2000 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.60.Fc Modulation, tuning, and mode locking
07.05.Dz Control systems

Reflective polarizer based on a stacked double-layer subwavelength metal grating structure fabricated using nanoimprint lithography

Zhaoning Yu, Paru Deshpande, Wei Wu, Jian Wang, and Stephen Y. Chou

Appl. Phys. Lett. 77, 927 (2000); http://dx.doi.org/10.1063/1.1288674 (3 pages) | Cited 47 times

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A reflective polarizer consisting of two layers of 190 nm period metal gratings was fabricated using nanoimprint lithography. Measurements with a He–Ne laser (wavelength=632.8 nm) showed that at normal incidence, this polarizer reflects light polarized perpendicular to the grating lines (transverse magnetic polarization) with a reflectance of 54%, but strongly absorbs parallel-polarized light (transverse electric polarization) with a reflectance of only 0.25%. The enhanced polarization extinction ratio of over 200 at this wavelength is possibly related to the resonance between the two layers of metal gratings. This polarizer is thin, compact, and is suited for integrated optical systems. © 2000 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer

All-solid-state electrochromic reflectance device for emittance modulation in the far-infrared spectral region

E. B. Franke, C. L. Trimble, M. Schubert, J. A. Woollam, and J. S. Hale

Appl. Phys. Lett. 77, 930 (2000); http://dx.doi.org/10.1063/1.1288810 (3 pages) | Cited 14 times

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All-solid-state electrochromic reflectance devices for thermal emittance modulation were designed for operation in the spectral region from mid- to far-infrared wavelengths (2–40 μm). All device constituent layers were grown by magnetron sputtering. The electrochromic (polycrystalline WO3), ion conductor (Ta2O5), and Li+ ion-storage layer (amorphous WO3), optimized for their infrared (IR) optical thicknesses, are sandwiched between a highly IR reflecting Al mirror, and a 90% IR transmissive Al grid top electrode, thereby meeting the requirements for a reversible Li+ ion insertion electrochromic device to operate within the 300 K blackbody emission range. Multicycle optical switching and emittance modulation is demonstrated. The measured change in emissivity of the device is to 20%. © 2000 American Institute of Physics.
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42.79.Fm Reflectors, beam splitters, and deflectors
65.90.+i Other topics in thermal properties of condensed matter (restricted to new topics in section 65)

Dipyrazolopyridine derivatives as bright blue electroluminescent materials

Y. T. Tao, E. Balasubramaniam, A. Danel, and P. Tomasik

Appl. Phys. Lett. 77, 933 (2000); http://dx.doi.org/10.1063/1.1288811 (3 pages) | Cited 48 times

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Very bright blue organic light emitting diodes were fabricated using highly fluorescent dipyrazolopyridine derivatives, 4-(4-substituted phenyl)-1,7-diphenyl-3,5-dimethyl-1,7dihydrodipyrazolo[3,4-b,4′,3′-e]pyridine (PAP–X, X�CN, Ph, and OMe), as emitter by doping the dye in an electron-transporting host, 2,2′,2″-(1,3,5-benzenetriyl)tris-[1-phenyl-1H-benzimidazole] (TPBI). Two hole-transporting layers, 4,4′-bis[N-(1-naphthyl-1-)-N-phenyl-amino]-biphenyl (NPB) and 4,4′-dicarbazolyl-1,1′-biphenyl (CBP) were used to achieve the emission from PAP–X. The devices with a general configuration of indium tin oxide/NPB/CBP/TPBI:PAP(2%)/Mg:Ag showed a bright blue emission. The PAP–CN-based device is exceptionally good, with a brightness of 11 200 cd/m2 at 14.2 V and the peak external quantum efficiency of 3.2%. The efficiency is the highest for the blue emission. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

Pyramid-shaped pixels for full-color organic emissive displays

Yang Yang and Shun-Chi Chang

Appl. Phys. Lett. 77, 936 (2000); http://dx.doi.org/10.1063/1.1288675 (3 pages) | Cited 5 times

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Organic electroluminescent emissive displays are composed by pixels consisting red-green-blue (RGB) light-emitting diodes (LEDs) in a planar arrangement. When operated, these RGB LEDs are biased independently to produce the required color. In this manuscript, we describe a promising pixel structure, the pyramid-shaped pixel (PSP) for the integration of organic light-emitting diodes (OLEDs) in full-color organic emissive displays. The RGB light-emitting diodes are constructed on the walls of the pyramid structure. When operated, the RGB LEDs emit photons through the base of the pyramid structure, hence these RGB LEDs share the same emissive area to produce the required color. The PSP structure offers the advantage of being a full color emissive pixel comprising of individual RGB OLEDs with very high resolution. In addition, pyramid pixel does not require shadow mask to pattern the organic materials during the vacuum deposition process. © 2000 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems

Optical properties and laser characteristics of highly Nd3+-doped Y3Al5O12 ceramics

Ichiro Shoji, Sunao Kurimura, Yoichi Sato, Takunori Taira, Akio Ikesue, and Kunio Yoshida

Appl. Phys. Lett. 77, 939 (2000); http://dx.doi.org/10.1063/1.1289039 (3 pages) | Cited 56 times

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Diode-pumped laser oscillation in highly Nd3+-doped polycrystalline Y3Al5O12 (YAG) ceramics has been demonstrated. The Nd:YAG ceramics are highly transparent; the loss of a 2.3 at. % neodymium-doped ceramic is as low as that of a 0.9 at. % Nd:YAG single crystal. The high doping of Nd3+ ions realizes large pump absorption; a 6.6 at. %-doped ceramic has an absorption coefficient of 60.4 cm−1 at 808 nm. The same concentration quenching parameter is obtained between the Nd:YAG ceramics and Nd:YAG single crystals. A laser using an 847-μm-thick 3.4 at. % Nd:YAG ceramic as a gain medium operates at 2.3 times higher output power than the same laser with a 719-μm-thick 0.9 at. % Nd:YAG single-crystal gain medium. © 2000 American Institute of Physics.
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42.70.Hj Laser materials
42.55.Rz Doped-insulator lasers and other solid state lasers
78.30.Hv Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials
78.40.Ha Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Design of thin-film photonic crystal waveguides

E. Silvestre, J. M. Pottage, P. St. J. Russell, and P. J. Roberts

Appl. Phys. Lett. 77, 942 (2000); http://dx.doi.org/10.1063/1.1289061 (3 pages) | Cited 8 times

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We present numerical designs for single-mode leak-free photonic crystal waveguides exhibiting strongly anisotropic spatial and temporal dispersion. These structures may be produced quite simply by drilling regular arrays of holes into thin films of high refractive index, and permit the realization of highly compact optical elements and wavelength division multiplexing devices. © 2000 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.82.Bq Design and performance testing of integrated-optical systems
42.70.Qs Photonic bandgap materials
42.15.Eq Optical system design

Time-dependence of luminescence of nanoparticles of Eu2O3 and Tb2O3 deposited on and doped in alumina

A. Gedanken, R. Reisfeld, L. Sominski, Z. Zhong, Yu. Koltypin, G. Panczer, M. Gaft, and H. Minti

Appl. Phys. Lett. 77, 945 (2000); http://dx.doi.org/10.1063/1.1289068 (3 pages) | Cited 24 times

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Nanoparticles of Eu2O3 and Tb2O3 have been prepared using ultrasound radiation and were deposited sonochemically on microspherical alumina particles. In a different sonochemical reaction Eu2O3 and Tb2O3 were doped into nanophased alumina particles. For both systems the decay times of the fluorescence was measured. The luminescence of the alumina substrate was found to be much shorter than that of the rare-earth oxides. Differences between the decay times of the deposited and doped materials are accounted for by the stronger guest-host interaction and absence of concentration quenching in the doped material. © 2000 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.47.-p Spectroscopy of solid state dynamics
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.66.Nk Insulators
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