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25 Sep 2006

Volume 89, Issue 13, Articles (13xxxx)

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Appl. Phys. Lett. 89, 131108 (2006); http://dx.doi.org/10.1063/1.2356892 (3 pages)

Paul E. Barclay, Kartik Srinivasan, Oskar Painter, Benjamin Lev, and Hideo Mabuchi
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Effect of third-order dispersion on subpicosecond pulse propagation in photonic-crystal waveguides

Yu Tanaka, Haruhiko Kuwatsuka, Hitoshi Kawashima, Naoki Ikeda, Yoshimasa Sugimoto, Toshifumi Hasama, and Hiroshi Ishikawa

Appl. Phys. Lett. 89, 131101 (2006); http://dx.doi.org/10.1063/1.2357152 (3 pages)

Online Publication Date: 25 September 2006

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We have experimentally investigated the effects of dispersion on subpicosecond pulse propagation over two-dimensional (2D) photonic-crystal-slab line-defect waveguides by time domain measurements. Using a heterodyne detection technique, pulse shapes after propagating along the waveguide were recorded as cross-correlated traces. When the pulse central frequency approached the band edge of the guided mode, the pulses were temporally delayed and their shapes were found to be broadened asymmetrically; this effect originated from the group velocity dispersion (GVD), encompassing higher-order dispersion effects. Theoretical pulse shapes, including third-order dispersion (TOD), agreed well with the experimental results. When the group velocity (vg) reached 0.08c, c being the speed of light, we found a GVD of ∼ 5.0 ps2/mm and a TOD of ∼ 0.3 ps3/mm. Experimentally obtained vg, GVD, and TOD characteristics agreed well with those obtained from 2D plane-wave-expansion band calculations.
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42.82.Et Waveguides, couplers, and arrays
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Pockel’s coefficient enhancement of poled electro-optic polymers with a hybrid organic-inorganic sol-gel cladding layer

Christopher T. DeRose, Y. Enami, C. Loychik, R. A. Norwood, D. Mathine, M. Fallahi, N. Peyghambarian, J. D. Luo, A. K.-Y. Jen, M. Kathaperumal, and M. Yamamoto

Appl. Phys. Lett. 89, 131102 (2006); http://dx.doi.org/10.1063/1.2357157 (3 pages) | Cited 13 times

Online Publication Date: 25 September 2006

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Ultraefficient poling of electro-optic polymers is reported using an organically modified sol-gel cladding layer. This poling technique has resulted in a Pockel’s coefficient enhancement of up to a factor of 2.5, going from 26 pm/V when poled without a sol-gel cladding to 65 pm/V when optimally poled with a sol-gel cladding. The poling process directly applies to a previously reported hybrid electro-optic polymer/sol-gel waveguide modulator and may have applications in other poled polymer based devices.
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42.70.Jk Polymers and organics
78.20.Jq Electro-optical effects

Halftoning band gap of InAs/InP quantum dots using inductivelycoupled argon plasma-enhanced intermixing

D. Nie, T. Mei, C. D. Xu, and J. R. Dong

Appl. Phys. Lett. 89, 131103 (2006); http://dx.doi.org/10.1063/1.2357563 (3 pages) | Cited 4 times

Online Publication Date: 25 September 2006

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Inductively coupled argon plasma-enhanced intermixing of InAs/InP quantum dots grown on InP substrate is investigated. Intermixing is promoted by the near-surface defects generated by plasma exposure in annealing at a temperature of 600 °C for 30 s. The annealing results in a maximum differential band-gap blueshift of 106 nm but a thermal shift of only 10 nm. Band-gap halftones are obtained by controlling the amount of near-surface defects via wet chemical etching on the plasma-exposed InP cap layer. No degradation of quantum-dot crystal quality due to the process has been observed as evidenced by photoluminescence intensity.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing

High-performance 1.55 μm low-temperature-grown GaAs resonant-cavity-enhanced photodetector

Q. Han, Z. C. Niu, L. H. Peng, H. Q. Ni, X. H. Yang, Y. Du, H. Zhao, R. H. Wu, and Q. M. Wang

Appl. Phys. Lett. 89, 131104 (2006); http://dx.doi.org/10.1063/1.2357916 (3 pages) | Cited 3 times

Online Publication Date: 25 September 2006

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A 1.55 μm low-temperature-grown GaAs (LT-GaAs) photodetector with a resonant-cavityenhanced structure was designed and fabricated. A LT-GaAs layer grown at 200 °C was used as the absorption layer. Twenty- and fifteen-pair GaAs/AlAs-distributed Bragg reflectors were grown as the bottom and top mirrors. A responsivity of 7.1 mA/W with a full width at half maximum of 4 nm was obtained at 1.61 μm. The dark current densities are 1.28×10−7 A/cm2 at the bias of 0 V and 3.5×10−5 A/cm2 at the reverse bias of 4.0 V. The transient response measurement showed that the photocarrier lifetime in LT-GaAs is 220 fs.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Bh Lenses, prisms and mirrors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Second harmonic generation in GaN/Al50Ga50N films deposited by metal-organic chemical vapor deposition

M. C. Larciprete, M. Centini, A. Belardini, L. Sciscione, M. Bertolotti, C. Sibilia, M. Scalora, A. Passaseo, and B. Potì

Appl. Phys. Lett. 89, 131105 (2006); http://dx.doi.org/10.1063/1.2357022 (3 pages) | Cited 7 times

Online Publication Date: 26 September 2006

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Second harmonic generation was observed experimentally from GaN/Al50Ga50N multilayers grown on sapphire substrate by means of the rotational Maker fringe technique at a fundamental beam wavelength of 1064 nm. From a single thick GaN layer (302 nm), the d33 of GaN was evaluated and compared to the nonlinear coefficient obtained from measurements on several thin multilayer samples. Results show that the process of growing several thin, alternating layers does not cause the deterioration of the effective nonlinear susceptibility, which is 4.82 pm/V for GaN and 1.20 pm/V for Al50Ga50N, consistent with known values obtained for thick substrates.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Fd III-V semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.65.An Optical susceptibility, hyperpolarizability

Optically induced linear electro-optic effects in ytterbium-doped strontium yttrium borate Sr3Y(BO3)3:Yb nanocrystallites incorporated into polymer matrices

J. Ebothé, I. V. Kityk, J. Kisielewski, T. Lukasiewicz, R. Diduszko, and A. Majchrowski

Appl. Phys. Lett. 89, 131106 (2006); http://dx.doi.org/10.1063/1.2357035 (3 pages)

Online Publication Date: 26 September 2006

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Yb-doped Sr3Y(BO3)3 nanocrystallites incorporated into polymethyl methacrylate matrices (4.5% by weight) were optically treated by coherent picosecond laser pulses at 1.34 and 0.67 μm. This composite exhibits a large effective electro-optic coefficient (up to 6.2 pm/V at 1040 nm wavelength). Decrease of the nanocrystallite size and increase of the Yb content lead to substantial enhancement of the effective electro-optic coefficient. For nanocrystallite sizes equal to about 5 nm, the coefficient increases from 2.2 pm/V (8% of Yb) up to 6.2 pm/V (20% of Yb). This material appears thus promising in application for the optically operated modulators.
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78.20.Jq Electro-optical effects
78.47.-p Spectroscopy of solid state dynamics
42.70.Jk Polymers and organics

Attitudinal manipulation of an optically trapped bacillary probe by controlling the distance between focal points for local dosing in cells

Toshiki Yasokawa, Ichirou Ishimaru, Yuki Nakagawa, Shigeki Kuriyama, Tsutomu Masaki, Seiji Nakai, Kaoru Takegawa, and Naotaka Tanaka

Appl. Phys. Lett. 89, 131107 (2006); http://dx.doi.org/10.1063/1.2357922 (3 pages) | Cited 1 time

Online Publication Date: 26 September 2006

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Technology for the attitudinal manipulation of medical equipment for local dosing to single living cells is presented. The authors developed a “juggling probe” which can manipulate a bacillary probe with multiple degrees of freedom and high accuracy without physical contact by using light pressure. With this technology, the authors cause two beams to focus on the probe from both the top and bottom faces. When the two focal points coincide, the probe becomes trapped immediately in a stable fixed attitude. Furthermore, the probe remains at rest in an arbitrary tilted attitude simply by controlling the distance between the two focal points.
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87.80.Cc Optical trapping
87.17.-d Cell processes
42.62.Be Biological and medical applications
87.63.L- Visual imaging

Integration of fiber-coupled high-Q SiNx microdisks with atom chips

Paul E. Barclay, Kartik Srinivasan, Oskar Painter, Benjamin Lev, and Hideo Mabuchi

Appl. Phys. Lett. 89, 131108 (2006); http://dx.doi.org/10.1063/1.2356892 (3 pages) | Cited 43 times

Online Publication Date: 27 September 2006

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Micron scale silicon nitride (SiNx) microdisk optical resonators are demonstrated with Q = 3.6×106 and an effective mode volume of 15(λ/n)3 at near-visible wavelengths. A hydrofluoric acid wet etch provides sensitive tuning of the microdisk resonances, and robust mounting of a fiber taper provides efficient fiber optic coupling to the microdisks while allowing unfettered optical access for laser cooling and trapping of atoms. Measurements indicate that cesium adsorption on the SiNx surfaces significantly red detunes the microdisk resonances. Parallel integration of multiple (10) microdisks with a single fiber taper is also demonstrated.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
42.81.Qb Fiber waveguides, couplers, and arrays
37.10.De Atom cooling methods
37.10.Gh Atom traps and guides

Polymeric distributed feedback lasers by room-temperature nanoimprint lithography

Elisa Mele, Andrea Camposeo, Ripalta Stabile, Pompilio Del Carro, Francesca Di Benedetto, Luana Persano, Roberto Cingolani, and Dario Pisignano

Appl. Phys. Lett. 89, 131109 (2006); http://dx.doi.org/10.1063/1.2357116 (3 pages) | Cited 18 times

Online Publication Date: 27 September 2006

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Room temperature nanoimprinting lithography is used to realize a distributed feedback laser by direct dry pressing of the conjugated polymer (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]). The laser device exhibits emission at 630 nm with a pump threshold of 25 μJ/cm2 and a polarization contrast of the emitted light as large as 0.91. Therefore, room temperature nanoimprint lithography turns out to be very effective for producing stable patterns on light-emitting polymers for the one-step fabrication of nanopatterned optoelectronic devices.
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42.55.Px Semiconductor lasers; laser diodes
42.70.Jk Polymers and organics
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
42.60.By Design of specific laser systems

InSb/AlxIn1−xSb quantum-well light-emitting diodes with high internal quantum efficiencies

B. I. Mirza, G. R. Nash, S. J. Smith, M. K. Haigh, L. Buckle, M. T. Emeny, and T. Ashley

Appl. Phys. Lett. 89, 131110 (2006); http://dx.doi.org/10.1063/1.2357558 (3 pages) | Cited 5 times

Online Publication Date: 27 September 2006

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The properties of InSb/AlxIn1−xSb quantum-well light-emitting diodes have been investigated as a function of temperature from 300 to 15 K. Over the whole range, the peak emission occurred at significantly higher energies than the band gap of InSb but below the band gap of the AlxIn1−xSb barriers, confirming that emission is from the quantum wells. Maximum internal quantum efficiencies of 65% and 85% were measured at 15 K for diodes containing 40 and 20 nm quantum wells, respectively.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Generation of highly directional beam by k-space filtering using a metamaterial flat slab with a small negative index of refraction

Alejandro Martínez, Miguel A. Piqueras, and Javier Martí

Appl. Phys. Lett. 89, 131111 (2006); http://dx.doi.org/10.1063/1.2357861 (3 pages) | Cited 4 times

Online Publication Date: 27 September 2006

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The authors show how a flat slab made of a metamaterial engineered to have a small negative index of refraction can be used to reshape radiation emitted from an isotropic source and produce a highly directional output beam. The slab makes a filtering of high transverse wave vectors of the input diverging beam. The predicted phenomenon is demonstrated at microwave frequencies using a two-dimensional photonic crystal made of alumina rods. Simulations using the finite-difference time-domain method support the experiments.
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42.70.Qs Photonic bandgap materials
42.79.Ci Filters, zone plates, and polarizers

Critical electric field for maximum tunability in nonlinear dielectrics

E. K. Akdogan and A. Safari

Appl. Phys. Lett. 89, 131112 (2006); http://dx.doi.org/10.1063/1.2357919 (3 pages) | Cited 2 times

Online Publication Date: 27 September 2006

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The authors develop a self-consistent thermodynamic theory to compute the critical electric field at which maximum tunability is attained in a nonlinear dielectric. They then demonstrate that the stored electrostatic free energy functional has to be expanded at least up to the sixth order in electric field so as to define the critical field, and show that it depends solely on the fourth and sixth order permittivities. They discuss the deficiency of the engineering tunability metric in describing nonlinear dielectric phenomena, introduce a critical field renormalized tunability parameter, and substantiate the proposed formalism by computing the critical electric field for prototypical 0.9Pb(Mg1/3,Nb2/3)–0.1PbTiO3 and Ba(Ti0.85,Sn0.15)O3 paraelectrics.
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77.22.Ch Permittivity (dielectric function)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
65.40.G- Other thermodynamical quantities
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems

Extraordinary transmission in a narrow energy band for metallic gratings with converging-diverging channels

A. Battula and S. C. Chen

Appl. Phys. Lett. 89, 131113 (2006); http://dx.doi.org/10.1063/1.2357037 (3 pages) | Cited 9 times

Online Publication Date: 28 September 2006

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Transmission metallic gratings with narrow and deep slits having the shape of converging-diverging channel (CDC) can exhibit enhanced transmission resonances for wavelengths larger than the periodicity of the grating. Using finite element method, the authors show that, by varying the gap size at the throat of CDC, the spectral locations of the transmission resonance bands can be shifted close to each other and have high transmittance in a very narrow energy band. Also, the proposed shape can lead to almost perfect transmittance for any desired wavelength by carefully optimizing the metallic material, gap at the throat of CDC, and grating parameters.
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42.79.Dj Gratings
42.70.Qs Photonic bandgap materials

Subband electronic temperatures and electron-lattice energy relaxation in terahertz quantum cascade lasers with different conduction band offsets

Miriam S. Vitiello, Gaetano Scamarcio, Vincenzo Spagnolo, Chris Worrall, Harvey E. Beere, David A. Ritchie, Carlo Sirtori, Jesse Alton, and Stefano Barbieri

Appl. Phys. Lett. 89, 131114 (2006); http://dx.doi.org/10.1063/1.2357042 (3 pages) | Cited 3 times

Online Publication Date: 28 September 2006

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The electronic temperatures of the conduction subbands, the local lattice temperature, and the electron-lattice energy relaxation times (τE) in bound-to-continuum GaAs/AlxGa1−xAs quantum cascade lasers, operating at 2.9 and 2 THz, are reported. This information has been gathered from the analysis of microprobe photoluminescence spectra collected during device continuous wave operation. We find that the electronic distributions in both the active region and the injector are thermalized and that all subbands share the same electronic temperature. The efficiency of electron cooling increases with the conduction band offset.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Wide-angle, low-voltage electro-optic beam deflection based on space-charge-controlled mode of electrical conduction in KTa1−xNbxO3

Koichiro Nakamura, Jun Miyazu, Masahiro Sasaura, and Kazuo Fujiura

Appl. Phys. Lett. 89, 131115 (2006); http://dx.doi.org/10.1063/1.2357335 (3 pages) | Cited 17 times

Online Publication Date: 28 September 2006

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An electro-optic beam deflector with unprecedented performance is demonstrated. A full deflection angle of 250 mrad ( = 14.3°) has been achieved by applying only ±250 V to a 0.5-mm-thick KTa1−xNbxO3 crystal with a short interaction length of 5.0 mm. The operating principle is investigated and the origin of the deflection phenomenon is attributed to a nonuniform electric field induced by space-charge-controlled electrical conduction in the crystal.
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42.79.Fm Reflectors, beam splitters, and deflectors
42.70.-a Optical materials
77.22.Jp Dielectric breakdown and space-charge effects
78.20.Jq Electro-optical effects

Dissociation processes of singlet and triplet excitons in organic photovoltaic cells

Zhihua Xu, Yue Wu, and Bin Hu

Appl. Phys. Lett. 89, 131116 (2006); http://dx.doi.org/10.1063/1.2357584 (3 pages) | Cited 15 times

Online Publication Date: 28 September 2006

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The dissociation processes of singlet and triplet excitons are studied based on fluorescent aluminum (III) 8-hydroxyquinoline (Alq3) and phosphorescent fac-tris-(2-phenylpyridine) iridium [Ir(ppy)3] molecules. We find that phosphorescent Ir(ppy)3 shows a more efficient photovoltaic response as compared to fluorescent Alq3. The short-circuit photocurrent action spectra and magnetic-field-dependent photocurrents reveal that the triplet excitons dissociate directly into free charge carriers at the metal-electrode interface while the singlet excitons experience bulk dissociation through polaron-pair states. This interface dissociation of triplet excitons forms a mechanism for phosphorescent organic materials to yield efficient photovoltaic responses.
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85.60.-q Optoelectronic devices
71.35.-y Excitons and related phenomena
71.38.-k Polarons and electron-phonon interactions

Modified local environment and enhanced near-infrared luminescence of Sm3+ in chalcohalide glasses

Zhiyong Yang, Gao Tang, Lan Luo, and Wei Chen

Appl. Phys. Lett. 89, 131117 (2006); http://dx.doi.org/10.1063/1.2357939 (3 pages) | Cited 14 times

Online Publication Date: 28 September 2006

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Near-infrared luminescence properties of Sm3+ in Ge–Ga–Se and GeSe2–Ga2Se3–CsI glasses were studied and the local environments of Sm3+ were investigated. Strong 1.24 and 1.49 μm fluorescence bands with respective bandwidths of 48 and 60 nm were observed. About 540 μs fluorescence lifetimes were obtained for the two emissions. As CsI was introduced to Ge–Ga–Se glasses, the luminescence properties were greatly enhanced, especially when I/Ga ratio reaches 1. This enhancement can be attributed to decreased local phonon mode which dominates the multiphonon relaxation. The Sm3+-doped GeSe2-based chalcohalide glasses can be promising materials for optical fiber amplifiers operating at 1.22–1.28 and 1.46–1.53 μm bands.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.55.Qr Amorphous materials; glasses and other disordered solids
63.50.-x Vibrational states in disordered systems

High operating temperature split-off band infrared detectors

A. G. U. Perera, S. G. Matsik, P. V. V. Jayaweera, K. Tennakone, H. C. Liu, M. Buchanan, G. Von Winckel, A. Stintz, and S. Krishna

Appl. Phys. Lett. 89, 131118 (2006); http://dx.doi.org/10.1063/1.2358106 (3 pages) | Cited 8 times

Online Publication Date: 29 September 2006

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Heterojunction interfacial work function internal photoemission detectors were used to demonstrate infrared response originating from hole transitions between light/heavy hole bands and the split-off (spin-orbit) band. A GaAs/AlGaAs heterojunction with a threshold wavelength of ∼ 20 μm indicated an operating temperature of 130 K for split-off response in the range of 1.5–5 μm with a peak D* of 1.0×108 Jones. Analysis suggests that practical devices with optimized parameters are capable of achieving room temperature operation with higher specific detectivity. Possible approaches to tailor the threshold for the split-off response to different wavelength ranges using different materials such as phosphides and nitrides are also discussed.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Blue-green small-signal gain and saturation in a luminescent polymer gain medium

Takeyuki Kobayashi, Michael Flämmich, Grace Jordan, Rebekah D’Arcy, Manuel Rüther, Werner J. Blau, Yasuhiro Suzuki, and Toshikuni Kaino

Appl. Phys. Lett. 89, 131119 (2006); http://dx.doi.org/10.1063/1.2348738 (3 pages) | Cited 13 times

Online Publication Date: 29 September 2006

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The authors study the optical gain and saturation behavior in a blue-green-emitting luminescent polymer gain medium. Based on the results of amplified spontaneous emission measurements, the gain coefficients, the gain-length product, and the corresponding small-signal gain are determined. By the use of the variable stripe length method, large net gain coefficients of up to 106±6 cm−1 have been measured under nanosecond photopumping. The large gain has favorable implications for the development of short wavelength lasers and amplifiers. Their study shows that a small-signal gain of 19 dB is achievable with a very compact optical amplifier with a 400 μm length.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.-v Laser optical systems: design and operation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Efficient beaming from photonic crystal waveguides via self-collimation effect

Donghua Tang, Lixue Chen, and Weiqiang Ding

Appl. Phys. Lett. 89, 131120 (2006); http://dx.doi.org/10.1063/1.2354428 (3 pages) | Cited 25 times

Online Publication Date: 29 September 2006

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Emission behavior of a subwavelength photonic crystal (PC) W1 waveguide covered by a self-collimation PC to the exit surface is investigated using finite-difference time-domain method. When the thickness and the relative position of the covering PC is designed appropriately, highly efficient beaming emission is obtained. The authors analyze the numerical results and attribute the beaming effect to the interference of the multiple self-collimation beams excited by the waveguide. This simple structure may find its potential applications in integrated optical circuits.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers

Visible quantum cutting through downconversion in green-emitting K2GdF5:Tb3+ phosphors

Te-Ju Lee, Li-Yang Luo, Eric Wei-Guang Diau, Teng-Ming Chen, Bing-Ming Cheng, and Chien-Yueh Tung

Appl. Phys. Lett. 89, 131121 (2006); http://dx.doi.org/10.1063/1.2358193 (3 pages) | Cited 42 times

Online Publication Date: 29 September 2006

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Visible quantum cutting under excitations at 212 and 172 nm in a green-emitting phosphor K2GdF5:Tb3+ (11%) via a downconversion mechanism is investigated. The authors measured the vacuum ultraviolet (VUV) excitation and emission spectra and proposed mechanisms to rationalize the quantum-cutting effect. One short-UV or one VUV photon absorbed by Tb3+ is split into multiple visible photons emitted by Tb3+ through cross relaxation and direct energy transfer. Calculations indicate an optimal quantum efficiency as great as 189% for this phosphor.
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78.40.Ha Other nonmetallic inorganics
42.50.-p Quantum optics

Phase-matched nondegenerate four-wave mixing in one-dimensional photonic crystals

C. Becker, M. Wegener, S. Wong, and G. von Freymann

Appl. Phys. Lett. 89, 131122 (2006); http://dx.doi.org/10.1063/1.2358295 (3 pages) | Cited 7 times

Online Publication Date: 29 September 2006

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The authors report on nondegenerate four-wave mixing in the near infrared using a one-dimensional chalcogenide-glass based photonic crystal. For 76 lattice constants, they find a 3.5-fold enhancement of the mixing signal with respect to the optimum-thickness bulk chalcogenide film. The key is the ability to tailor the dispersion relation of light in the photonic crystal, allowing for phase matching. Numerical calculations agree well with the experiments.
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42.70.Qs Photonic bandgap materials
42.70.Ce Glasses, quartz
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Surface plasmon coupling in hexagonal textured metallic microcavity

H. L. Tam, K. F. Li, K. W. Cheah, J. B. Xia, R. Huber, W. H. Wong, and Y. B. Pun

Appl. Phys. Lett. 89, 131123 (2006); http://dx.doi.org/10.1063/1.2347110 (3 pages) | Cited 3 times

Online Publication Date: 29 September 2006

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The coupling of surface plasmons to the photonic modes in hexagonal textured metallic microcavity was studied. The modified photonic modes enable efficient coupling with the luminescence source in the microcavity. Hexagonal photonic crystal lattice has higher folding symmetry providing more channels for surface plasmon coupling in different in-plane directions, i.e., more isotropic light extraction profile than one—or two-dimensional gratings. Results show that strong coupling between surface plasmon modes and the waveguide mode in the microcavity has led to angle-selective enhanced light extraction and it was as much as 12 times more light extracted compare to planar microcavity.
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42.82.Gw Other integrated-optical elements and systems
42.70.Qs Photonic bandgap materials

Mirror tunnel microscope

Aydogan Ozcan, Alberto Bilenca, Brett E. Bouma, and Guillermo J. Tearney

Appl. Phys. Lett. 89, 131124 (2006); http://dx.doi.org/10.1063/1.2356321 (3 pages) | Cited 2 times

Online Publication Date: 29 September 2006

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A microscope paradigm, which the authors term the “mirror tunnel microscope” (MTM), is described. The MTM uses a low numerical aperture (NA) lens together with parallel mirrors positioned between the lens plane and the object plane to provide a relatively simple means for digital wide-field microscopy. In MTM, the mirror tunnel acts as a spatial periodic-bandpass filter, which creates low-resolution, bandpassed versions of the object function in the image plane. However, each low-resolution image formed by the MTM carries a unique band of spatial frequencies. Coherent addition of the phase and amplitude of the spatial frequency information contained in each of these low-resolution images enhances the effective NA of the lens without decreasing field of view. To demonstrate the proof of principle, they have utilized a two-mirror MTM to reconstruct an image of a pinhole. Along the axis perpendicular to the mirrors, the image was reconstructed with higher resolution, commensurate with an effective fivefold NA increase. Initial results indicate that MTM is a promising method for wide-field digital microscopy.
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07.60.Pb Conventional optical microscopes
42.79.Bh Lenses, prisms and mirrors
42.30.Va Image forming and processing
42.30.Wb Image reconstruction; tomography

Gain structure optimization of vertical external cavity surface emitting laser at 920 nm

Jaeryung Yoo, Kisung Kim, Sangmoon Lee, Seongjin Lim, Gibum Kim, Junyoun Kim, Soohaeng Cho, Junho Lee, Taek Kim, and Yongjo Park

Appl. Phys. Lett. 89, 131125 (2006); http://dx.doi.org/10.1063/1.2356327 (3 pages) | Cited 7 times

Online Publication Date: 29 September 2006

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The authors have optimized a resonant gain structure of a 920 nm vertical external cavity surface emitting laser. They found that long saturated carrier lifetime in shallow quantum well (QW) under a high injection level restricted the laser performance. An insertion of nonabsorbing layer in the middle of barrier layers with multi-QWs was very effective to reduce the saturated carrier lifetime and, therefore, to enhance the laser performance. With the optimized gain structure, which had ten periods of triple InGaAs QWs with Al0.3Ga0.7As nonabsorbing layers in the middle of GaAs barriers, they achieved 4.9 W output power at 10 °C.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
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