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21 Oct 2002

Volume 81, Issue 17, pp. 3119-3293

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Optical speedup at transparency of the gain recovery in semiconductor optical amplifiers

T. P. Hessler, M.-A. Dupertuis, B. Deveaud, J.-Y. Emery, and B. Dagens

Appl. Phys. Lett. 81, 3119 (2002); http://dx.doi.org/10.1063/1.1516634 (3 pages) | Cited 5 times

Online Publication Date: 15 October 2002

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Experimental demonstration of optical speedup at transparency (OSAT) has been performed on a 1 mm long semiconductor optical amplifiers (SOA). OSAT is a recently proposed scheme that decreases the recovery time of an SOA while maintaining the available gain. It is achieved by externally injecting into the SOA the beam of a separate high power laser at energies around the transparency point. Even though the experimental conditions were not optimal, a beam of 100 mW decreases the recovery time by a third when it is injected in the vicinity of the material transparency point of the device. This acceleration of the device response without detrimental reduction of the gain is found to be effective over a broad wavelength window of about 20 nm around transparency. The injection of the accelerating beam into the gain region is a less efficient solution not only because the gain is then strongly diminished but also because speeding is reduced. This originates from the reduction of the amplified spontaneous emission power in the device, which counterbalances the speeding capabilities of the external laser beam. Another advantage of the OSAT scheme is realized in relatively long SOAs, which suffer from gain overshoot under strong current injection. Simulations show that OSAT decreases the gain overshoot, which should enable us to use OSAT to further speedup the response of long SOAs. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

Three-dimensional photonic crystals for optical wavelengths assembled by micromanipulation

Kanna Aoki, Hideki T. Miyazaki, Hideki Hirayama, Kyoji Inoshita, Toshihiko Baba, Norio Shinya, and Yoshinobu Aoyagi

Appl. Phys. Lett. 81, 3122 (2002); http://dx.doi.org/10.1063/1.1515117 (3 pages) | Cited 27 times

Online Publication Date: 15 October 2002

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We have established a profitable fabrication technique for three-dimensional (3D) photonic crystals for optical wavelengths. In our method, two-dimensional photonic plates, which serve as unit parts for 3D structures, are prepared by the semiconductor nanofabrication technique. Then, these plates are assembled into 3D structures by micromanipulation. Accurate lamination of the plates is assured by linking fiducial holes of neighboring plates with matching microspheres. With this technique, we have succeeded in fabricating 3D photonic crystals with one to four layers of woodpile structures. From scanning electron microscope observation of the crystals, the periodic error was determined to be within 50 nm. The optical properties of the crystals indicate existence of the photonic band gap at the expected wavelength of 3–4 μm. © 2002 American Institute of Physics.
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81.16.-c Methods of micro- and nanofabrication and processing
42.82.Cr Fabrication techniques; lithography, pattern transfer
06.60.Sx Positioning and alignment; manipulating, remote handling
42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.07.-b Nanoscale materials and structures: fabrication and characterization
42.86.+b Optical workshop techniques

Red-emitting electroluminescent devices based on osmium-complexes-doped blend of poly(vinylnaphthalene) and 1,3,4-oxadiazole derivative

Xuezhong Jiang, Alex K. Y. Jen, Brenden Carlson, and Larry R. Dalton

Appl. Phys. Lett. 81, 3125 (2002); http://dx.doi.org/10.1063/1.1514401 (3 pages) | Cited 35 times

Online Publication Date: 15 October 2002

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Efficient red electrophosphorescence was achieved from double-layer light-emitting devices using osmium (Os)-complexes-doped blend of poly(vinylnaphthalene) (PVN) and 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PVN:PBD) as the emitting layer. Blending PVN with PBD greatly suppresses the electromer emission of PVN. The PVN:PBD blend emanates a short-wavelength electroluminescence emission peaking at around 375 nm, which overlaps well with the absorption spectra of the Os complexes and ensures very efficient energy transfer to the Os-complex dopants. The best external quantum efficiency of the double-layer devices was 2.2%, with a photometric efficiency of 1.9 cd/A. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics

Harmonic frequency locking in a semiconductor laser with delayed negative optoelectronic feedback

F. Y. Lin and J. M. Liu

Appl. Phys. Lett. 81, 3128 (2002); http://dx.doi.org/10.1063/1.1516238 (3 pages) | Cited 8 times

Online Publication Date: 15 October 2002

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The locking states of a delayed negative optoelectronic feedback system are studied experimentally. Harmonic locking is observed in this system. Instead of locking to the frequency of the delay loop, the pulsing frequency of the system locks to a harmonic of the loop frequency. Moreover, a period-adding route of the locking states is found and locking states of Farey fractions up to order 17 are reported. The plot of the rotation number of the locking states shows a Devil’s staircase structure. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Fully transparent, organic light-emitting electrochemical cells

T. Ouisse, M. Armand, Y. Kervella, and O. Stéphan

Appl. Phys. Lett. 81, 3131 (2002); http://dx.doi.org/10.1063/1.1516610 (3 pages) | Cited 10 times

Online Publication Date: 15 October 2002

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We report the fabrication and performance of fully transparent, organic blue light-emitting electrochemical cells (OLECs), in which both the anode and cathode are made of indium tin oxide. The active layer is a blend of polyfluorene with long and flexible alkyl side chains grafted on the 9,9 position and of a molten salt. Two identical spin-coated active layers are laminated together at high temperature to form the OLECs. The electroluminescence threshold is around 3.3 V and the light intensity exceeds 10 μW/cm2 at 5 V. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
82.47.-a Applied electrochemistry

Photonic pseudo-gap-based modification of photoluminescence from CdS nanocrystal satellites around polymer microspheres in a photonic crystal

Y. Lin, J. Zhang, E. H. Sargent, and E. Kumacheva

Appl. Phys. Lett. 81, 3134 (2002); http://dx.doi.org/10.1063/1.1515881 (3 pages) | Cited 51 times

Online Publication Date: 15 October 2002

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We report the combination of microsphere self-organization to form a photonic crystal, providing spectrally and angularly dependent electromagnetic structural resonances; with nanocrystal growth in situ on microsphere surfaces, providing optical functionalization with spectral control achieved through the quantum size effect. We demonstrate this material system using CdS nanocrystals coating the surfaces of poly(methyl methacrylate)–poly(methacrylic acid) (PMMA–PMAA) micrometer spheres. The in situ synthesis of the CdS nanocrystals on the surface of the PMMA/PMAA microspheres preserves the propensity of the hybrid microspheres to form ordered colloid arrays. Luminescence from surface states ensures that light is emitted at energies significantly below the absorption edge of the emitting species. Transmission and photoluminescence measurements reveal the interaction of the photonic stop band with photoluminescence from the nanocrystals. © 2002 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
42.70.Jk Polymers and organics
73.22.-f Electronic structure of nanoscale materials and related systems

A possible mechanism for enhanced electrofluorescence emission through triplet–triplet annihilation in organic electroluminescent devices

Chimed Ganzorig and Masamichi Fujihira

Appl. Phys. Lett. 81, 3137 (2002); http://dx.doi.org/10.1063/1.1515129 (3 pages) | Cited 29 times

Online Publication Date: 15 October 2002

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We demonstrate here that luminance increased more than linearly with an increase in current density of tris(8-hydroxyquinoline) aluminum (Alq3)-based electroluminescent (EL) devices and the EL efficiency reached ∼5 cd A−1 at 250 mA cm−2 when electron and hole injection was well balanced. The luminance–current curves were well fitted with a combination of a linear and a quadratic function of the current. The quadratic component can be attributed to additional singlet excited state (1Alq3∗) formation through triplet–triplet (T–T) annihilation of triplet excited states (3Alq3∗). The requirement of the well-balanced charge injection implies that the long-lived 3Alq3∗ was quenched efficiently by energy transfer to excess and colored Alq3−⋅ anion or Alq3+⋅ cation radicals in the emission zone when the charge injection was unbalanced. The short-lived 1Alq3∗ was not quenched appreciably. © 2002 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
71.35.-y Excitons and related phenomena
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Cascaded electro-optic scanning of laser light over large angles using domain microengineered ferroelectrics

David A. Scrymgeour, Alok Sharan, Venkatraman Gopalan, Kevin T. Gahagan, Joanna L. Casson, Robert Sander, Jeanne M. Robinson, Fikri Muhammad, Premanand Chandramani, and Fouad Kiamilev

Appl. Phys. Lett. 81, 3140 (2002); http://dx.doi.org/10.1063/1.1516232 (3 pages) | Cited 22 times

Online Publication Date: 15 October 2002

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We present a device concept based on cascaded electro-optic deflection in a domain microengineered ferroelectric chip. In our design, large deflection angles are achieved by cascading several smaller scanners in a single ferroelectric chip, such that each successive scanner stage builds upon the deflection of the previous stage. We demonstrate the basic concept using a two-stage device fabricated in a single crystal wafer of ferroelectric LiTaO3. By operating the device using a specially designed programmable multichannel driver that provides ±1.1 kV per stage, a total scan angle of 25.4° at 5 kHz was demonstrated. Even larger angles of deflection are possible with additional scanner stages. © 2002 American Institute of Physics.
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42.79.Ls Scanners, image intensifiers, and image converters
78.20.Jq Electro-optical effects
77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Super-resolution digital holographic imaging method

Cheng Liu, Zhigang Liu, Feng Bo, Yong Wang, and Jianqiang Zhu

Appl. Phys. Lett. 81, 3143 (2002); http://dx.doi.org/10.1063/1.1517402 (3 pages) | Cited 40 times

Online Publication Date: 15 October 2002

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A method to realize super-resolution digital holographic imaging is demonstrated experimentally. By placing a grating in front of the specimen, more object waves can reach the charge-coupled devices target during the recording of a digital hologram, and the image reconstructed from the digital hologram has a resolution over the diffraction limit of the ordinary holographic system. This method overcomes the crucial drawback of digital holography, and may find many applications in three-dimensional digital imaging and microscopy. © 2002 American Institute of Physics.
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42.40.Jv Computer-generated holograms
42.30.Wb Image reconstruction; tomography
42.79.Pw Imaging detectors and sensors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Room-temperature 2.5 μm InGaAsSb/AlGaAsSb diode lasers emitting 1 W continuous waves

J. G. Kim, L. Shterengas, R. U. Martinelli, G. L. Belenky, D. Z. Garbuzov, and W. K. Chan

Appl. Phys. Lett. 81, 3146 (2002); http://dx.doi.org/10.1063/1.1517176 (3 pages) | Cited 43 times

Online Publication Date: 15 October 2002

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We have characterized 2.5-μm-wavelength InGaAsSb/AlGaAsSb/GaSb two-quantum-well diode lasers that emit 1 W continuous waves from a 100-μm-wide aperture at a temperature of 12 °C. The threshold current density is 250 A/cm2, and the external quantum efficiency near threshold is 0.36. The wall–plug efficiency reaches a maximum of 12% at a current of 2 A. Operating in the pulsed-current mode, the devices output nearly 5 W at 20 °C. These lasers exhibit internal losses of about 4 cm−1 and differential series resistances of about 0.1 Ω. A broad-waveguide design lowers internal losses, and highly doped transition regions between the cladding layers and the GaSb reduces series resistance. © 2002 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.)
42.79.Gn Optical waveguides and couplers
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