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9 Dec 2002

Volume 81, Issue 24, pp. 4499-4663

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Highly-bright white organic light-emitting diodes based on a single emission layer

C. H. Chuen and Y. T. Tao

Appl. Phys. Lett. 81, 4499 (2002); http://dx.doi.org/10.1063/1.1528736 (3 pages) | Cited 81 times

Online Publication Date: 3 December 2002

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A very bright white organic light-emitting diode (OLED) was fabricated with a thin layer of 4-{4-[N-(1-naphthyl)-N-phenylaminophenyl]}-1,7-diphenyl-3,5-dimethyl-1,7-dihydro-dipyrazolo [3,4-b;4′3′-e]pyridine (PAP-NPA) doped with rubrene as the source of the white emission. Thus, with a simple three-layer structure of ITO/NPB(40 nm)/PAP-NPA:0.5% rubrene(20 nm)/TPBI(40 nm)/Mg:Ag, a white light with Commission Internationale de l’Eclairage (CIE) coordinates of (0.31, 0.33) were generated. The device gave a maximum brightness of ∼42 000 cd/m2 at 14 V, and maximum luminance efficiencies of 2.92 lm/W at 6.5 V and 6.11 cd/A at 7.0 V. The CIE coordinates stayed virtually constant when the voltage increased from 8 to 12 V. Furthermore, with a two-layer structure of ITO/PAP-NPA:0.4%rubrene(40 nm)/TPBI(40 nm)/Mg:Ag, the device also reached a stable white color with maximum brightness of ∼37 000 cd/m2 and maximum luminance efficiencies of 2.51 lm/W at 6.5 V and 5.57 cd/A at 8.5 V. The stability of the white color is attributed to the confinement of charge recombination zone in a single layer. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.60.Pg Display systems

Si-based omnidirectional reflector and transmission filter optimized at a wavelength of 1.55 μm

Hyun-Yong Lee, Hisao Makino, Takafumi Yao, and Akinori Tanaka

Appl. Phys. Lett. 81, 4502 (2002); http://dx.doi.org/10.1063/1.1524291 (3 pages) | Cited 44 times

Online Publication Date: 3 December 2002

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Omnidirectional (omni-) reflector and transmission filter optimized at a wavelength of 1.55 μm have been realized using Si/SiO2 one-dimensional photonic crystals (1D PCs). Photonic band structures in the PCs with and without a defect layer have been also analyzed. The 1D PCs fabricated have very large omnidirectional photonic band gaps (omni-PBGs), and their measured reflectance spectra are in very good agreement with the calculated results. The omni-PBG in a six-pair Si/SiO2 1D PC (no defect layer, a filling factor η=0.406) exists in a normalized frequency range of 0.223–0.297. Introducing a defect layer generates a defect state in the PBG, and it behaves like electronic impurity levels in the gap with a change in thickness of the defect layer (dD). A six-pair Si/SiO2 1D PC with the structure parameters of η=4.060, dH (Si thickness)=95.3 nm, dL (SiO2 thickness)=234.9 nm, and dD = 2.336⋅dH could act as a 1.55 μm-transmission filter for normal incidence light. © 2002 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.70.Qs Photonic bandgap materials

Light-induced absorption changes in In-doped congruent LiNbO3

Steven Sunarno, Yasuo Tomita, and Guoquan Zhang

Appl. Phys. Lett. 81, 4505 (2002); http://dx.doi.org/10.1063/1.1526165 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2002

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We investigate visible and near-infrared light-induced absorption changes caused by intrinsic defect centers in congruently melting and reduced LiNbO3:In with a single-shot picosecond pulse at 532 nm. It is found that the dark decay dynamics of optically induced shallow centers strongly depend on In concentrations. Two types of optically induced shallow centers having dark decay time constants on the orders of milliseconds and tens of microseconds are observed in LiNbO3 doped with In below the damage-resistant threshold concentrations. Only one of the two types is observed in LiNbO3 doped with In above it. The origin of these shallow centers is also discussed. © 2002 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Ha Other nonmetallic inorganics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.30.Hv Other nonmetallic inorganics
42.70.Gi Light-sensitive materials

Switchable organic electroluminescence

Xi-Cun Gao, De-Chun Zou, Katsuhiko Fujita, and Tetsuo Tsutsui

Appl. Phys. Lett. 81, 4508 (2002); http://dx.doi.org/10.1063/1.1528738 (3 pages) | Cited 13 times

Online Publication Date: 3 December 2002

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The vacuum deposited amorphous organic thin film melamine cyanurate (MC) is found to possess an electrical switching property. The as-fabricated fresh thin film is at a semiconductor state and shows a rectification property in a range of several voltages. Under a higher applied voltage, the resistance of the film changes to a lower value, and shows linearity in its current–voltage relationship. After the application of a negative driving voltage for no more than 100 s, the MC film returns from the resistor state to the semiconductor state with a higher impedance. Based on this reproducible switching phenomenon, a type of voltage-controlled switchable organic electroluminescence device was fabricated by inserting the MC layer between the anode indium tin oxide (ITO) and the hole transport layer N,N′-bis (3-methylphenyl)-N,N′-diphenyl-benzidine (TPD). In the forward driving voltage scan (for example, increasing the driving voltage from 0 to 16 V), the impedance is higher and the current density is lower; then the scan is backward (decreasing the driving voltage from 16 to 0 V), the impedance becomes lower and the current density becomes higher. Corresponding to the two different current density states at the same driving voltage, the device luminance also reaches two different states, one is lower and another is higher. This transition from a high (ON) to low luminance (OFF) renders a prototype to realize a switchable organic electroluminescence. © 2002 American Institute of Physics.
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78.60.Fi Electroluminescence
81.05.Gc Amorphous semiconductors
78.66.Qn Polymers; organic compounds
73.61.Ph Polymers; organic compounds
72.60.+g Mixed conductivity and conductivity transitions
85.60.Jb Light-emitting devices
72.80.Ng Disordered solids
73.61.Jc Amorphous semiconductors; glasses
78.66.Jg Amorphous semiconductors; glasses
72.80.Le Polymers; organic compounds (including organic semiconductors)
73.40.Ei Rectification

Two-color hologram multiplexing from the colored state in stoichiometric LiNbO3:Tb,Fe

Myeongkyu Lee, Hideki Hatano, Satoru Tanaka, Takashi Yamaji, Kenji Kitamura, and Shunji Takekawa

Appl. Phys. Lett. 81, 4511 (2002); http://dx.doi.org/10.1063/1.1528283 (3 pages) | Cited 1 time

Online Publication Date: 3 December 2002

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We have performed two-color hologram multiplexing in stoichiometric LiNbO3:Tb,Fe, which exhibits a photochromic effect. One hundred angle-multiplexed holograms of nearly equivalent strength have been recorded from the colored state by use of 850 nm recording beams and a 436 nm gating light. The stored holograms were highly resistant against erasure during continuous readout. It was estimated that 80 million readouts with a bit rate of 1 Gbit/s is possible before the diffracted signal intensity decays to half of its initial value. © 2002 American Institute of Physics.
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42.40.Ht Hologram recording and readout methods
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Dropping of electromagnetic waves through localized modes in three-dimensional photonic band gap structures

Mehmet Bayindir and E. Ozbay

Appl. Phys. Lett. 81, 4514 (2002); http://dx.doi.org/10.1063/1.1528733 (3 pages) | Cited 23 times

Online Publication Date: 3 December 2002

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We experimentally demonstrate trapping and dropping of photons through localized cavity modes in three-dimensional layer-by-layer photonic crystal structures. By creating acceptor- and donor-like cavities which are coupled to a highly confined waveguide (HCW), we drop selected frequencies from the waveguide mode. Tunability of the demultiplexing structures can be achieved by changing the properties of cavities and the coupling between the cavity and the HCW. © 2002 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
84.40.Az Waveguides, transmission lines, striplines
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Measurements of α-factor in 2–2.5 μm type-I In(Al)GaAsSb/GaSb high power diode lasers

L. Shterengas, G. L. Belenky, A. Gourevitch, J. G. Kim, and R. U. Martinelli

Appl. Phys. Lett. 81, 4517 (2002); http://dx.doi.org/10.1063/1.1528291 (3 pages) | Cited 6 times

Online Publication Date: 3 December 2002

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Spectra of the linewidth enhancement factor (α) of room-temperature-operated high-power 2–2.5 μm In(Al)GaAsSb/GaSb type-I quantum-well (QW) lasers were measured using Hakki–Paoli technique. Values of α at threshold were in the range 2.5 to 4 for all devices under study. Devices emitting 1 W cw power at λ = 2.5 μm have 1.5%–1.6% compressively strained QW active region and the lowest α equal to 2.5. Measured average filament spacings in near field are in rough agreement with predictions given by experimental α-factor values. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Supermode-noise suppression using a nonlinear Fabry–Pérot filter in a harmonically mode-locked fiber ring laser

Donghui Zhao, Yicheng Lai, Xuewen Shu, Lin Zhang, and Ian Bennion

Appl. Phys. Lett. 81, 4520 (2002); http://dx.doi.org/10.1063/1.1528732 (3 pages) | Cited 4 times

Online Publication Date: 3 December 2002

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A simple efficient method for stabilizing a harmonically mode-locked fiber ring laser is proposed. In this method, a linear optical filter and a nonlinear Fabry–Pérot filter in which the refractive index is optical intensity dependent are located in the laser cavity. The linear filter is used to select a fixed lasing wavelength, and the Fabry–Pérot filter introduces a negative all-optical feedback mechanism that is able to suppress pulse-to-pulse amplitude fluctuations in the laser cavity. The scheme was experimentally demonstrated using a fiber Bragg grating as the linear filter and a laser diode biased below threshold as the nonlinear Fabry–Pérot, and stable harmonically mode-locked pulses with a supermode noise suppression ratio >55 dB were obtained. © 2002 American Institute of Physics.
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42.60.Mi Dynamical laser instabilities; noisy laser behavior
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Wd Fiber lasers
42.79.Ci Filters, zone plates, and polarizers
42.60.Fc Modulation, tuning, and mode locking
42.79.Dj Gratings
42.60.By Design of specific laser systems

Transverse mode-locking in microcavity lasers

R. Gordon, A. P. Heberle, and J. R. A. Cleaver

Appl. Phys. Lett. 81, 4523 (2002); http://dx.doi.org/10.1063/1.1528287 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2002

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We experimentally demonstrate mode-locking between the transverse modes of a laser. A vertical-cavity surface-emitting laser with evenly-spaced transverse modes is shown to emit a train of 2.1±0.1 ps pulses with an 11 ps repetition rate and a timing jitter of 235±30 fs. Transverse mode-locking in microcavity lasers has potential to improve the compactness, stability, integrability, repetition rate tunability, and efficiency of ultrafast optical communication sources. © 2002 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Red, green, and blue upconversion luminescence of trivalent-rare-earth ion-doped Y2O3 nanocrystals

Daisuke Matsuura

Appl. Phys. Lett. 81, 4526 (2002); http://dx.doi.org/10.1063/1.1527976 (3 pages) | Cited 160 times

Online Publication Date: 3 December 2002

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Trivalent-rare-earth ion-doped Y2O3 nanocrystals have been synthesized, and their photoluminescence properties have been studied under 980 nm laser diode excitation. The crystallite size estimated by x-ray diffractometry and scanning electron microscopy was about 30–40 nm. In Yb3+ and Tm3+ codoped Y2O3 nanocrystals, the bright blue emissions near 450 and 480 nm have been noticeable due to the 1D2–3F4 and 1G4–3H6 transitions of Tm3+, respectively. The bright green emissions of Er3+ doped Y2O3 nanocrystals appeared near 530 and 550 nm were assigned to the 2H11/2–4I15/2 and 4S3/2–4I15/2 transitions of Er3+, respectively. The ratio of the intensity of green luminescence to that of red luminescence has decreased with an increase of concentration of Yb3+ in Er3+ doped Y2O3 nanocrystals. In sufficient quantities of Yb3+ to Er3+, the bright red emission near 660 nm has been predominant due to the 4F9/2–4I15/2 transition of Er3+. The primary color components are in these red, green, and blue emissions, from which a wide spectrum of colors, including white, would be produced by appropriate mixing them. © 2002 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
71.55.Ht Other nonmetals
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