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9 Feb 1998

Volume 72, Issue 6, pp. 627-747

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Existence of two-dimensional absolute photonic band gaps in the visible

A. Barra, D. Cassagne, and C. Jouanin

Appl. Phys. Lett. 72, 627 (1998); http://dx.doi.org/10.1063/1.120827 (3 pages) | Cited 16 times

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Using the plane wave method, we study two two-dimensional structures that possess absolute photonic band gaps: the triangular and the graphite photonic crystals. We compare their convenience in achieving photonic crystals which inhibit the propagation of visible electromagnetic waves. We show that this is very difficult to obtain with a triangular structure because its gap is too narrow and its dimensions are too small to be fabricated. On the contrary, wider gaps and larger dimensions that can easily be etched makes graphite a much more appropriate structure. © 1998 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
77.22.Ch Permittivity (dielectric function)

One-way image transmission through a thick dynamic distorter without a reference beam

Jiasen Zhang, Huitian Wang, Shin Yoshikado, and Tadashi Aruga

Appl. Phys. Lett. 72, 630 (1998); http://dx.doi.org/10.1063/1.120828 (3 pages) | Cited 2 times

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We demonstrated a method to perform one-way image transmission through a dynamic distorter without a reference beam. In this method, a photorefractive four-wave mixing configuration was used to pick up the reconstructed image from the image-bearing signal beam, which acted as an erase beam. The fluctuation period of the dynamic distorter must be much shorter than the response time of the nonlinear material. Reconstructed images with high-fidelity have been obtained. Because use of a reference beam is unnecessary this method is simpler and more effective. © 1998 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.30.Va Image forming and processing
78.20.-e Optical properties of bulk materials and thin films

Stabilization of two diode laser wavelengths using photorefractive gratings

Changxi Yang, S. Yokoyama, T. Honda, and K. Seta

Appl. Phys. Lett. 72, 633 (1998); http://dx.doi.org/10.1063/1.120829 (3 pages) | Cited 3 times

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We propose to demonstrate a method of stabilizing the wavelengths of two diode lasers through the use of two photorefractive volume gratings. The two photorefractive gratings recorded at a visible line from an argon ion laser in one LiNbO3 crystal are designed to be Bragg matched for the counterpropagating reflections at infrared wavelengths. The two diode lasers are stabilized at the center wavelengths of the counterpropagating reflections of the two gratings. The stabilized wavelengths and the synthetic wavelength exhibit good short- and long-term stabilities. By using photorefractive crystal, we can effectively control the separation of the stabilized wavelengths. The thermal stability of the photorefractive gratings and the thermal stability of the synthetic wavelength are discussed. © 1998 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.20.-e Optical properties of bulk materials and thin films
42.79.Dj Gratings
42.55.Px Semiconductor lasers; laser diodes

Exciplex formation at the organic solid-state interface: Yellow emission in organic light-emitting diodes using green-fluorescent tris(8-quinolinolato)aluminum and hole-transporting molecular materials with low ionization potentials

Koji Itano, Hiromitsu Ogawa, and Yasuhiko Shirota

Appl. Phys. Lett. 72, 636 (1998); http://dx.doi.org/10.1063/1.120826 (3 pages) | Cited 79 times

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The bilayer organic light-emitting diodes using green-fluorescent tris(8-quinolinolato)aluminum (Alq3) as an emitting material and hole-transport materials with low ionization potentials, 1,3,5-tris(3-methylphenylphenylamino)triphenylamine and 4,4′,4″-tris[bis(4-tert-buthylbiphenyl4-yl)amino]triphenylamine, emitted bright yellow light instead of green light. The yellow emission is attributed to exciplex formation at the solid interface between Alq3 and the hole-transport material. The exciplex formation was evidenced by the measurement of the photoluminescence spectra and lifetimes of the mixture of an equimolar amount of Alq3 and each of the hole-transport materials. The emission color can be tuned by varying the applied voltage. © 1998 American Institute of Physics.
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73.61.Ph Polymers; organic compounds
78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds
85.60.Jb Light-emitting devices
78.40.Me Organic compounds and polymers

200 MHz optical signal modulation from a porous silicon light emitting device

M. Balucani, S. La Monica, and A. Ferrari

Appl. Phys. Lett. 72, 639 (1998); http://dx.doi.org/10.1063/1.120830 (2 pages) | Cited 5 times

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The light emission frequency response of an extremely stable Schottky (Al-porous silicon) light emitting device is presented. The construction steps, critical for device stability, are also presented. The device, when it is reverse biased in breakdown conditions, shows a white light emission visible in normal daylight. The emission mechanism is supposed to be the radiative transition of hot electrons generated in the breakdown process. The optical signal modulation has been measured up to 200 MHz and a simple electrical model is presented in order to explain the dynamic behavior of the device. The device speed seems to be limited by the junction capacitance rather than by an intrinsic physical limit of the emission mechanism. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
42.79.Hp Optical processors, correlators, and modulators
77.22.Jp Dielectric breakdown and space-charge effects
72.20.Ht High-field and nonlinear effects
85.30.De Semiconductor-device characterization, design, and modeling

730-nm-emitting Al-free active-region diode lasers with compressively strained InGaAsP quantum wells

A. Al-Muhanna, J. K. Wade, L. J. Mawst, and R. J. Fu

Appl. Phys. Lett. 72, 641 (1998); http://dx.doi.org/10.1063/1.120831 (3 pages) | Cited 9 times

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0.73-μm-emitting, Al-free active-region, strained (Δa/a ≈ 1.4%) InGaAsP single-quantum-well diode lasers have been grown by low-pressure metal–organic chemical-vapor deposition. A broad waveguide laser design with In0.5(Ga0.5Al0.5)0.5P cladding layers is utilized to achieve a large effective transverse spot size (d/Γ = 0.433 μm) and to minimize carrier leakage from the active region. Threshold current densities of 514 A/cm2 (100-μm-wide stripe, L = 1 mm), external differential quantum efficiencies of 60%, and characteristic temperature coefficients for the threshold current, T0, and external differential quantum efficiency characteristic temperature, T1, have values of 72 and 153 K, respectively. Continuous wave output powers of 1.4 W are obtained from facet-coated (90%/10%) devices operating at 735 nm. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.60.Pk Continuous operation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.05.Ea III-V semiconductors
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Time-domain measurement of intersubband oscillations in a quantum well

James N. Heyman, Roland Kersting, and Karl Unterrainer

Appl. Phys. Lett. 72, 644 (1998); http://dx.doi.org/10.1063/1.120832 (3 pages) | Cited 34 times

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We report time-domain measurements of electron intersubband oscillations in quantum wells. We use an interferometric technique to measure the change in the profile of a few-cycle THz pulse due to propagation through a modulation-doped Al0.3Ga0.7As/GaAs multiple quantum well structure (10×510 Å wells). From this data we obtain the absorption and the index of refraction due to electrons in the quantum well, and due to the GaAs substrate. Unlike existing studies of coherent charge oscillations of electrons and holes in heterostructures excited by ultrashort pulses of band-gap light, our all-THz measurements quantitatively determine the linear optical properties of the quantum well electrons. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Acoustic focusing associated with excimer laser ablation of the cornea

S. Siano, R. Pini, F. Rossi, R. Salimbeni, and P. G. Gobbi

Appl. Phys. Lett. 72, 647 (1998); http://dx.doi.org/10.1063/1.120834 (3 pages) | Cited 2 times

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Focusing, as well as diffraction effects experienced by the stress wave produced by the argon–fluoride excimer laser ablation of corneal tissue have been studied in artificial and real eye samples. The evolution of the laser-induced acoustic front was imaged by means of fast shadowgraphy in an artificial eye model, while the absolute temporal profile of the pressure transient along the optical axis was directly measured in enucleated porcine eyes by a needle hydrophone inserted into the eyeball. Observations pointed out that the finite size of the acoustic source gave rise to diffraction effects during propagation, as the development of a negative tensile phase in the pulse shape, while the spherical shape of the acoustic source produced focusing of the wave front, causing pressure enhancements up to a factor of 3 in real eyes. The implications to surgical laser procedures as photorefractive keratectomy are discussed. © 1998 American Institute of Physics.  
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42.62.Be Biological and medical applications
87.50.Y- Biological effects of acoustic and ultrasonic energy
42.66.-p Physiological optics
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues

Photoconductivity of an inorganic/organic composite containing dye-sensitized nanocrystalline titanium dioxide

M. Kocher, T. K. Däubler, E. Harth, U. Scherf, A. Gügel, and D. Neher

Appl. Phys. Lett. 72, 650 (1998); http://dx.doi.org/10.1063/1.120835 (3 pages) | Cited 18 times

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The photophysical properties of solid films of an inorganic/organic composite composed of dye-sensitized nanocrystalline titanium dioxide (TiO2) particles, a conjugated polymer, and a [60] fullerene derivative have been investigated. Large charge collection efficiencies of up to 10% at a field of only 10 V/μm were observed. The photoaction spectrum of the composite is interpreted in terms of three major contributions: a weak photocurrent due to the absorption of photons by the polymer, photogeneration of charges involving the fullerene, and a broad region below the onset of the polymer absorption which involves photophysical processes in the dye-loaded TiO2 nanoparticles. © 1998 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
73.61.Wp Fullerenes and related materials
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