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16 Jul 2001

Volume 79, Issue 3, pp. 281-445

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Optical metastability of subband gap (2.2 eV) yellow luminescence in GaN

Y. C. Chang, A. E. Oberhofer, J. F. Muth, R. M. Kolbas, and R. F. Davis

Appl. Phys. Lett. 79, 281 (2001); http://dx.doi.org/10.1063/1.1381417 (3 pages) | Cited 11 times

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Optical metastability has been studied in undoped GaN films grown on SiC substrates having a previously deposited AlN buffer layer. Brief exposures to a higher intensity ultraviolet light resulted in temporary changes in the optical properties of the GaN layer. The photoinduced changes created high contrast patterns on samples that could be observed under an optical microscope with lower intensity ultraviolet excitation. The subband gap yellow photoluminescence peak at 2.2 eV increased significantly after the patterns were created. This change slowly returned (hours) to its initial value at room temperature. The retention time decreased to a few seconds at temperatures above 100 °C. The data showed that a 1.34 eV thermal activation energy exists, which suggests that the cause of these metastable properties is related to the subband gap yellow luminescence. © 2001 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.20.At Surface states, band structure, electron density of states

Indium tin oxide thin films grown on flexible plastic substrates by pulsed-laser deposition for organic light-emitting diodes

H. Kim, J. S. Horwitz, G. P. Kushto, Z. H. Kafafi, and D. B. Chrisey

Appl. Phys. Lett. 79, 284 (2001); http://dx.doi.org/10.1063/1.1383568 (3 pages) | Cited 58 times

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Transparent conducting indium tin oxide (ITO) thin films were grown by pulsed laser deposition (PLD) on flexible polyethylene terephthalate (PET) substrates. The structural, electrical, and optical properties of these films were investigated as a function of substrate deposition temperature and background gas pressure. ITO films (200 nm thick), deposited by PLD on PET at 25 °C and 45 mTorr of oxygen, exhibit high optical transparency (∼87%) in the visible (400–700 nm) with a low electrical resistivity of 7×10−4 Ω cm. ITO films grown by PLD on PET were used as the anode contact in organic light-emitting devices. A luminous power efficiency of ∼1.6 lm/W was achieved at 100 cd/m2, slightly higher than that (∼1.5 lm/W) measured for the control device based on a sputter-deposited ITO on glass. © 2001 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
85.60.Jb Light-emitting devices

Er3+ photoluminescence properties of erbium-doped Si/SiO2 superlattices with subnanometer thin Si layers

Yong Ho Ha, Sehun Kim, Dae Won Moon, Ji-Hong Jhe, and Jung H. Shin

Appl. Phys. Lett. 79, 287 (2001); http://dx.doi.org/10.1063/1.1383802 (3 pages) | Cited 9 times

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The effect of the Si layer thickness on the Er3+ photoluminescence properties of the Er-doped Si/SiO2 superlattice is investigated. We find that the Er3+ luminescence intensity increases by over an order of magnitude as the Si layer thickness is reduced from 3.6 nm down to a monolayer of Si. Temperature dependence of the Er3+ luminescence intensity and time-resolved measurement of Er3+ luminescence intensity identify the increase in the excitation rate as the likely cause for such an increase, and underscore the importance of the Si/SiO2 interface in determining the Er3+ luminescence properties. © 2001 American Institute of Physics.
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78.55.Ap Elemental semiconductors
71.55.Cn Elemental semiconductors
81.05.Cy Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
73.21.Cd Superlattices
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
78.47.-p Spectroscopy of solid state dynamics

Modified Mach–Zender laser interferometer for probing bulk acoustic waves

G. G. Fattinger and P. T. Tikka

Appl. Phys. Lett. 79, 290 (2001); http://dx.doi.org/10.1063/1.1385340 (3 pages) | Cited 12 times

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This letter reports the usage of a modified Mach–Zehnder interferometer for visualization of the mechanical vibrations of high-frequency, bulk-mode, thin-film resonators. The setup is capable of detecting frequencies from 30 kHz up to 12 GHz with an amplitude down to less than 10 pm, which means a dynamic range above 80 dB. The achieved lateral resolution of the measured field image is more than 300 nm. Due to a new phase stabilizing system phase sensitive measurements are possible, additionally bringing up the possibility of establishing a tremendous measurement speed of up to 5 million points/h. This setup can be applied to bulk acoustic wave development in order to provide information such as material parameters, to verify theoretical models and to learn about device behavior which cannot be done using only electrical measurement tools. © 2001 American Institute of Physics.
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07.10.-h Mechanical instruments and equipment
43.58.-e Acoustical measurements and instrumentation

Continuous-wave self-pumped optical parametric oscillator based on Yb3+-doped bulk periodically poled LiNbO3 (MgO)

J. Capmany, D. Callejo, V. Bermúdez, E. Diéguez, D. Artigas, and L. Torner

Appl. Phys. Lett. 79, 293 (2001); http://dx.doi.org/10.1063/1.1383567 (3 pages) | Cited 11 times

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We present experimental evidence of continuous-wave self-pumped parametric oscillation in Yb3+-doped periodically poled lithium niobate co-doped with MgO. A single bulk crystal of periodically poled lithium niobate containing Yb3+ laser-active ions performs as a singly resonant parametric oscillator generating a signal wave at 1360 nm. The optical parametric oscillator is intracavity pumped by the laser emission at 1063 nm produced by the Yb3+ ions in the crystal. The whole system is end pumped at 980 nm. © 2001 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
77.80.-e Ferroelectricity and antiferroelectricity

Formation dynamics of diffraction gratings in reactive liquid crystals

P. A. Kossyrev and G. P. Crawford

Appl. Phys. Lett. 79, 296 (2001); http://dx.doi.org/10.1063/1.1385343 (3 pages) | Cited 6 times

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Using in situ diffraction measurements of diffraction grating formation in a single component reactive mesogen system, the anisotropy in the diffusion constants is determined. The data are well explained by a diffusion model, which accounts for the density modulation due to shrinkage upon photopolymerization with interfering laser beams. © 2001 American Institute of Physics.
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42.79.Dj Gratings
42.70.Df Liquid crystals
82.35.Ej Nonlinear optics with polymers
82.50.Nd Control of photochemical reactions
82.50.Hp Processes caused by visible and UV light

Modulation of light radiation during input into waveguide by resonance excitation of surface plasmons

N. A. Janunts and Kh. V. Nerkararyan

Appl. Phys. Lett. 79, 299 (2001); http://dx.doi.org/10.1063/1.1385798 (3 pages) | Cited 9 times

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The process of transfer of energy of a surface plasmon polariton between modes located on two surfaces of a metal layer is studied. It is shown that this process strongly depends on the refractive indices of dielectrics surrounding the metal layer. The possibilities of high-speed optical signal modulation, based on this phenomenon, are discussed. © 2001 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Hp Optical processors, correlators, and modulators
78.68.+m Optical properties of surfaces
42.82.Bq Design and performance testing of integrated-optical systems
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Optically pumped integrated absorber 3.4 μm laser with InAs-to-InGaAsSb type-II transition

R. Kaspi, A. Ongstad, C. Moeller, G. C. Dente, J. Chavez, M. L. Tilton, and D. Gianardi

Appl. Phys. Lett. 79, 302 (2001); http://dx.doi.org/10.1063/1.1385581 (3 pages) | Cited 12 times

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We report optically pumped lasing at λ∼3.4 μm from an integrated absorber structure in which the electrons confined in the InAs quantum wells recombine with holes in adjacent InGaAsSb layers to provide the gain. This type-II laser exhibits an estimated photon-to-photon conversion rate of ∼24% at 85 K. The self-consistent empirical pseudopotential method calculations suggest that Coulomb attraction can lead to a strong enhancement in carrier overlap, and the resulting small shift in transition energy is consistent with that observed. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Efficient and stable dye laser action from modified dipyrromethene BF2 complexes

A. Costela, I. García-Moreno, C. Gómez, F. Amat-Guerri, and R. Sastre

Appl. Phys. Lett. 79, 305 (2001); http://dx.doi.org/10.1063/1.1385185 (3 pages) | Cited 13 times

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We report on the lasing action of modified dipyrromethene BF2 complexes in air-equilibrated liquid solutions. All recent dyes share a common chromophore core and were dissolved in apolar, polar nonprotic, and polar protic solvents. When pumped transversely at 534 nm, nearly solvent-independent laser emission was obtained with efficiencies well over 40% in most cases. Highest lasing efficiency was 59%. Under continuous ultraviolet irradiation some of these dyes demonstrated improved photostability as compared with commercial dye pyrromethene 567. © 2001 American Institute of Physics.
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42.55.Mv Dye lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

White-light electroluminescence from soluble oxadiazole-containing phenylene vinylene ether-linkage copolymer

Yuh-Zheng Lee, Xiwen Chen, Ming-Chih Chen, Show-An Chen, Jui-Hung Hsu, and Wunshain Fann

Appl. Phys. Lett. 79, 308 (2001); http://dx.doi.org/10.1063/1.1385586 (3 pages) | Cited 65 times

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We report a promising oxadiazole-containing phenylene vinylene ether-linkage copolymer, which can emit nearly white light from a single-layer light-emitting diode. The emission spectrum is composed of a red component originating from the new excited dimer in addition to the blue-green component from an individual lumophore and excimer. This excited dimer is formed under a strong electric field inside the diode and cannot be produced by photoexcitation, which is different from the excimer or exciplex that is often found both in photoluminescence and electroluminescence, and it is termed the “electromer.” © 2001 American Institute of Physics.
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42.70.Jk Polymers and organics
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Speed enhancement in a photorefractive multiple-quantum-well modulator by pulsed illumination

A. K. Abeeluck, P. Heinz, and E. Garmire

Appl. Phys. Lett. 79, 311 (2001); http://dx.doi.org/10.1063/1.1385797 (3 pages)

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A factor-of-four increase in the operating speed of a high-resolution low-temperature-grown photorefractive multiple-quantum-well (PRMQW) spatial light modulator is reported. This is achieved by shining a spatially uniform erasing pulse from a light-emitting diode (LED) on the device that is driven by a single-sided applied voltage. The erasing pulse is turned on briefly during the off-voltage cycle while a grating is written during the on-voltage cycle using a continuous-wave laser diode. The dependence of the change in diffraction efficiency on the frequency of the applied voltage, on the timing and duration of the LED pulse, and on the intensities of the LED and of the pump beams has been investigated. Our results are relevant to applications of PRMQW modulators where both high spatial resolution and fast operating speed are required. © 2001 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.25.Fx Diffraction and scattering
42.79.Dj Gratings

All-optical diode in a periodically poled lithium niobate waveguide

Katia Gallo, Gaetano Assanto, Krishnan R. Parameswaran, and Martin M. Fejer

Appl. Phys. Lett. 79, 314 (2001); http://dx.doi.org/10.1063/1.1386407 (3 pages) | Cited 75 times

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We have demonstrated a guided-wave all-optical diode based on engineered quasiphase Matching in a LiNbO3 channel waveguide. For input peak powers beyond 1.5 W at 1.55 μm, the device exhibited a spatially nonreciprocal response, leading to optical isolation with contrasts as high as 90% at 3.1 W, in agreement with theoretical predictions. © 2001 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
42.70.-a Optical materials
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