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16 Apr 2007

Volume 90, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 164102 (2007); http://dx.doi.org/10.1063/1.2728578 (3 pages)

Chaorong Li, Ailing Ji, and Zexian Cao
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Spatial refractive index sensor using whispering gallery modes in an optically trapped microsphere

Peter Zijlstra, Karen L. van der Molen, and Allard P. Mosk

Appl. Phys. Lett. 90, 161101 (2007); http://dx.doi.org/10.1063/1.2722695 (3 pages) | Cited 13 times

Online Publication Date: 16 April 2007

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The authors propose the use of an optically trapped, dye doped polystyrene microsphere for spatial probing of the refractive index at any position in a fluid. Using the dye embedded in the microsphere as an internal broadband excitation source the authors eliminated the need for a tunable excitation source. They measured the full width at half maximum and frequency spacing of the transverse electric and transverse magnetic resonances as a function of the refractive index of the immersion fluid. The authors achieved a sensitivity of 5×10−4 in refractive index, even when the exact size of the microsphere was not known.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Low temperature InP/Si wafer bonding using boride treated surface

Hui Huang, Xiaomin Ren, Wenjuan Wang, Hailan Song, Qi Wang, Shiwei Cai, and Yongqing Huang

Appl. Phys. Lett. 90, 161102 (2007); http://dx.doi.org/10.1063/1.2724922 (3 pages) | Cited 1 time

Online Publication Date: 16 April 2007

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An approach for InP/Si wafer bonding based on boride-solution treatment was presented. The bonding energy is higher than the InP fracture energy by annealing at 280 °C. An In0.53Ga0.47As/InP multiple-quantum-well (MQW) structure grown on InP was transferred onto Si substrate via the bonding process. X-ray diffraction and photoluminescence reveal that crystal quality of the bonded MQW was preserved. A thin B2O3–POx–SiO2 oxide layer of about 28 nm thick at the bonding interface was detected. X-ray photoelectron spectroscopy and Raman analyses indicate that the formation of oxygen bridging bonds by boride treatment is responsible for the strong fusion obtained at such low temperature.
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81.05.Ea III-V semiconductors
81.05.Cy Elemental semiconductors
81.07.St Quantum wells
81.65.-b Surface treatments
61.72.Cc Kinetics of defect formation and annealing
78.67.De Quantum wells

Fabrication and characterization of PbS/multiwalled carbon nanotube heterostructures

Dingshan Yu, Yujie Chen, Baojun Li, Xudong Chen, and Mingqiu Zhang

Appl. Phys. Lett. 90, 161103 (2007); http://dx.doi.org/10.1063/1.2723651 (3 pages) | Cited 10 times

Online Publication Date: 16 April 2007

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PbS quantum dots/multiwalled carbon nanotube (PbS/MWCNT) heterostructures were fabricated via a simple wet-chemical method. The structural and optical properties of as-prepared samples were characterized by transmission electron microscopy, x-ray diffraction, micro-Raman, and photoluminescence spectroscopies. It was found that the size, shape, and coverage density of the PbS quantum dots on the MWCNT can be controlled through varying synthesis conditions. Photoluminescence spectrum revealed that the emission of the PbS quantum dots was partially quenched when they were coupled to the MWCNT. This suggests that the photoinduced charge transfer may occur between the PbS and the MWCNT.
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81.16.Be Chemical synthesis methods
61.46.-w Structure of nanoscale materials
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.30.-j Infrared and Raman spectra
78.55.-m Photoluminescence, properties and materials

Optical modes in pyramidal GaAs microcavities

F. M. Weber, M. Karl, J. Lupaca-Schomber, W. Löffler, S. Li, T. Passow, J. Hawecker, D. Gerthsen, H. Kalt, and M. Hetterich

Appl. Phys. Lett. 90, 161104 (2007); http://dx.doi.org/10.1063/1.2723688 (3 pages) | Cited 8 times

Online Publication Date: 16 April 2007

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Pyramidal GaAs structures on top of GaAs/AlAs distributed Bragg reflectors are investigated as candidates for true three-dimensional cavities with potentially low mode volume and high quality-factor. Different types of single and coupled resonators with base lengths of a few microns are realized using a combination of molecular-beam epitaxy, electron-beam lithography, and wet chemical etching. Embedded InGaAs quantum dots are utilized as light sources to verify the resonator modes. Furthermore, a spatially localized emission through the pyramid facets indicates the future possibility of coupling cavity modes to optical fibers. This could be interesting within the context of single photon emitters.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors

High Q modes in elliptical microcavity pillars

D. M. Whittaker, P. S. S. Guimaraes, D. Sanvitto, H. Vinck, S. Lam, A. Daraei, J. A. Timpson, A. M. Fox, M. S. Skolnick, Y.-L. D. Ho, J. G. Rarity, M. Hopkinson, and A. Tahraoui

Appl. Phys. Lett. 90, 161105 (2007); http://dx.doi.org/10.1063/1.2722683 (3 pages) | Cited 13 times

Online Publication Date: 16 April 2007

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The degenerate fundamental mode of a microcavity pillar structure with circular cross section splits into two linearly polarized modes when the shape is changed to elliptical. The quality factor Q of these modes is very different. This letter demonstrates that the high Q mode provides better values of the figure of merit for strong coupling applications, Q/mathV), where V is the modal volume, compared to values obtainable in circular structures. The difference in Q is shown to be a consequence of the polarization dependence of the losses through the microcavity mirrors.
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42.79.Bh Lenses, prisms and mirrors

Unidirectional laser emission from π-conjugated polymer microcavities with broken symmetry

A. Tulek and Z. V. Vardeny

Appl. Phys. Lett. 90, 161106 (2007); http://dx.doi.org/10.1063/1.2723078 (3 pages) | Cited 14 times

Online Publication Date: 16 April 2007

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We report unidirectional laser emission from π-conjugated polymer microcavities with broken symmetry geometries such as spiral and microdisk containing a “line defect,” in comparison with plain microdisk cavity having isotropic emission. We found that the laser emission directionality contrast ratio is 8–10 and far field lateral divergence angle is 12°–15° for both broken symmetry geometries, with no significant increase in the laser threshold intensity. Fourier transform analysis of the laser emission spectra shows that unlike microdisks with line defect, the variation of light trajectories in the spiral microcavities leads to less defined laser modes.
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42.55.Sa Microcavity and microdisk lasers
42.60.By Design of specific laser systems
42.70.Jk Polymers and organics
42.30.Kq Fourier optics
42.70.Hj Laser materials

Surface plasmon enhanced photoluminescence of conjugated polymers

Hong-Ju Park, Doojin Vak, Yong-Young Noh, Bogyu Lim, and Dong-Yu Kim

Appl. Phys. Lett. 90, 161107 (2007); http://dx.doi.org/10.1063/1.2721134 (3 pages) | Cited 26 times

Online Publication Date: 17 April 2007

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To produce surface plasmons, silver nanostructures were fabricated using a thermal evaporation method and the surface plasmon wavelength was tuned via an annealing. These nanostructures were located between the indium tin oxide (ITO) and poly(3,4-ethylenedioxy thiophene)/poly(styrenesulfonate) for the coupling of the surface plasmon resonance with organic fluorophores. To prevent the quenching of emission, spacer was placed between the light emitting polymers and the ITO substrate. As a result, the authors were able to observe an increase in photoluminescence of conjugated polymers using the silver nanostructures.
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78.68.+m Optical properties of surfaces
78.55.Kz Solid organic materials
81.40.Gh Other heat and thermomechanical treatments
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Polarized laser emission from an anisotropic one-dimensional photonic crystal laser

Sun Woong Kim, Byoungchoo Park, and Y. P. Lee

Appl. Phys. Lett. 90, 161108 (2007); http://dx.doi.org/10.1063/1.2723677 (3 pages) | Cited 5 times

Online Publication Date: 17 April 2007

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The authors studied the laser emission from an anisotropic one-dimensional (1D) photonic crystal (PC) laser. An active medium layer, consisted of an epoxy resin doped with fluorescent dye, was sandwiched between two anisotropic 1D PC films. Efficient laser emissions were generated by optical pumping at relatively low lasing thresholds. The wavelengths of the emitted lasers were 611 and 618 nm, which correspond to the two split eigenmodes at the low-energy band edges due to the anisotropy of the PCs. The authors also demonstrated that the polarization of the lasing emission can be controlled by adjusting the birefringence of the PCs.
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42.55.Tv Photonic crystal lasers and coherent effects
42.60.By Design of specific laser systems
42.70.Qs Photonic bandgap materials
42.70.Hj Laser materials

Hole escape processes detrimental to photoluminescence efficiency in a blue InGaN multiple-quantum-well diode under reverse bias conditions

T. Inoue, K. Fujiwara, and J. K. Sheu

Appl. Phys. Lett. 90, 161109 (2007); http://dx.doi.org/10.1063/1.2723683 (3 pages) | Cited 1 time

Online Publication Date: 17 April 2007

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Photoluminescence (PL) properties of a blue In0.3Ga0.7N multiple-quantum-well (MQW) diode with an additional n+-doped In0.18Ga0.82N electron reservoir layer (ERL) have been investigated at 20 K as a function of reverse bias under indirect barrier excitation. A PL intensity ratio of MQW/ERL is observed to be significantly quenched by increasing the reverse field due to electron-hole separation and carrier escape, in spite of observed blueshifts, when the excitation power is decreased by two orders of magnitude. The PL intensity reduction suggests that the hole escape process plays an important role for determination of the PL efficiency under the reverse bias.
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85.30.Kk Junction diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Enhanced light extraction of GaN-based light-emitting diodes by using textured n-type GaN layers

Hyunsoo Kim, Jaehee Cho, Jeong Wook Lee, Sukho Yoon, Hyungkun Kim, Cheolsoo Sone, Yongjo Park, and Tae-Yeon Seong

Appl. Phys. Lett. 90, 161110 (2007); http://dx.doi.org/10.1063/1.2724903 (3 pages) | Cited 18 times

Online Publication Date: 17 April 2007

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The authors report on the enhancement of the light extraction efficiency of GaN-based light-emitting diodes (LEDs) via the texturing of n-type layers. Compared with standard LEDs, LED fabricated with the textured n-type layers produced a significant improvement in the output power, depending on the reflectivity of the n electrode, the etch-pit size, and the chip dimension. The textured LEDs were found to yield the output power enhancement as high as 54%. However, it was also found that the electrical property of the textured LEDs can be degraded when the size of the etch pits is too large, indicating that a well-controlled texturing process is required for the realization of high-efficiency LEDs.
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85.60.Jb Light-emitting devices
81.65.Cf Surface cleaning, etching, patterning

Coherence properties of high-β elliptical semiconductor micropillar lasers

S. Ates, S. M. Ulrich, P. Michler, S. Reitzenstein, A. Löffler, and A. Forchel

Appl. Phys. Lett. 90, 161111 (2007); http://dx.doi.org/10.1063/1.2724908 (3 pages) | Cited 10 times

Online Publication Date: 17 April 2007

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The authors report complementary investigations on the coherence properties of spontaneous and stimulated emission from (In,Ga)As/GaAs quantum-dot-based high-quality semiconductor micropillar cavities. Low temperature microphotoluminescence measurements on an elliptically shaped micropillar revealed a clear polarization splitting (ΔE ∼ 45 μeV) of its fundamental mode. Full conformity is found with an oscillatory behavior observed in corresponding g(1)(τ) first-order field correlation measurements. In addition, power-dependent g(1)(τ) series on a single polarization component of the lasing mode have systematically revealed a strong coherence time increase from τc ∼ 25 to  ∼ 430 ps, which traces the change of emission characteristics from thermal to coherent light.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Sa Microcavity and microdisk lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Influence of unsymmetrical periodicity on extraordinary transmission through periodic arrays of subwavelength holes

Xi-Feng Ren, Guo-Ping Guo, Yun-Feng Huang, Zhi-Wei Wang, and Guang-Can Guo

Appl. Phys. Lett. 90, 161112 (2007); http://dx.doi.org/10.1063/1.2724914 (3 pages) | Cited 8 times

Online Publication Date: 17 April 2007

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Quadrate hole array is explored to study the influence of unsymmetrical periodicity on extraordinary optical transmission through periodic arrays of subwavelength holes. It is found that the transmission efficiency of light and the ratio between transmission efficiencies of horizontal and vertical polarized light can be continuously tuned by rotating the quadrate hole array. The authors can calculate out the transmission spectra (including the heights and locations of peaks) for any rotation angle θ with a simple theoretical model.
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78.66.Bz Metals and metallic alloys
78.68.+m Optical properties of surfaces
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Experimental determination of the band gap dependence of Auger recombination in InGaAs/InP multiple quantum well lasers at room temperature

N. F. Massé, A. R. Adams, and S. J. Sweeney

Appl. Phys. Lett. 90, 161113 (2007); http://dx.doi.org/10.1063/1.2722041 (3 pages) | Cited 8 times

Online Publication Date: 17 April 2007

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The band gap dependencies of the threshold current and its radiative component are measured using high pressure techniques. Detailed theoretical calculations show that the band gap dependence of the internal losses plays a significant role in the band gap dependence of the radiative current. Temperature dependence measurements show that the radiative current accounts for 20% of the total threshold current at room temperature. This allows us to determine the pressure dependence of the non-radiative Auger recombination current, and hence to experimentally obtain the variation of the Auger coefficient C with band gap.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Carrier-envelope phase stabilized 5.6 fs, 1.2 mJ pulses

Hiroki Mashiko, Christopher M. Nakamura, Chengquan Li, Eric Moon, He Wang, Jason Tackett, and Zenghu Chang

Appl. Phys. Lett. 90, 161114 (2007); http://dx.doi.org/10.1063/1.2724919 (3 pages) | Cited 40 times

Online Publication Date: 17 April 2007

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The authors report the generation of 1.2 mJ pulses with a duration of 5.6 fs from a neon filled hollow-core fiber seeded with carrier-envelope phase stabilized 2.2 mJ, 25 fs pulses. The carrier-envelope phase after the fiber was measured by a second, out-loop f-to-2f interferometer. With seed pulse power locked, the carrier-envelope phase of the two-cycle pulses is controlled to a standard deviation of 370 mrad. The peak power of the carrier-envelope phase stabilized pulses, 0.2 TW, is twice that previously generated. The significance of seed pulse energy stability for carrier-envelope phase stabilization of few-cycle laser pulses is demonstrated.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.81.Cn Fiber testing and measurement of fiber parameters

Dichromatic InGaN-based white light emitting diodes by using laser lift-off and wafer-bonding schemes

Y. J. Lee, P. C. Lin, T. C. Lu, H. C. Kuo, and S. C. Wang

Appl. Phys. Lett. 90, 161115 (2007); http://dx.doi.org/10.1063/1.2722672 (3 pages) | Cited 16 times

Online Publication Date: 18 April 2007

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An InGaN-based dual-wavelength blue/green (470 nm/550 nm) light emitting diode (LED) with three terminal operations has been designed and fabricated by using sapphire laser lift-off and wafer-bonding schemes. The device is equivalent to a parallel connection of blue and green LEDs; thus the effective electrical resistance of the device could be reduced. The luminous efficiency is 40 lm/W at 20 mA, accompanied by a broad electroluminescence emission with a combination of blue and green colors. This monolithically integrated dichromatic lighting structure has great potential in the application of the solid-state lighting.
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85.60.Jb Light-emitting devices
42.62.-b Laser applications
85.30.-z Semiconductor devices

Two-photon-induced three-dimensional optical data storage in CdS quantum-dot doped photopolymer

Xiangping Li, Craig Bullen, James W. M. Chon, Richard A. Evans, and Min Gu

Appl. Phys. Lett. 90, 161116 (2007); http://dx.doi.org/10.1063/1.2724902 (3 pages) | Cited 16 times

Online Publication Date: 18 April 2007

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The authors demonstrate three-dimensional erasable bit optical data storage in a quantum-dot doped photopolymer under two-photon excitation by a near-infrared femtosecond pulsed laser beam. It is shown that the photorefractive polymer consisting of poly(vinyl carbazole), ethyl carbazole, 4-(diethylaminobenzylidene)-malononitrile, and CdS quantum dots exhibits the changes not only in refractive index but also in fluorescence. Such a photosensitivity provides a multimode readout mechanism. In particular, the use of S rich surface quantum dots not only allows the two-photon-induced bit optical data storage with greater contrast but also expands the margin between permanent and erasable recording thresholds.
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42.79.Vb Optical storage systems, optical disks
42.70.Ln Holographic recording materials; optical storage media
42.70.Jk Polymers and organics
42.70.Gi Light-sensitive materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Cathodoluminescence spectroscopy and imaging of GaN/(Al,Ga)N nanocolumns containing quantum disks

Uwe Jahn, Jelena Ristić, and Enrique Calleja

Appl. Phys. Lett. 90, 161117 (2007); http://dx.doi.org/10.1063/1.2724913 (3 pages) | Cited 2 times

Online Publication Date: 18 April 2007

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Using spatially resolved cathodoluminescence spectroscopy, the authors have measured the spectral and spatial distribution of the luminescence intensity of GaN/(Al,Ga)N nanocolumns containing quantum disks. The optical emission of the quantum disk and of the thick (Al,Ga)N layer in the columns were clearly identified. The disk spectra of single columns are as broad as 80 meV. A significant contribution to this broadening is probably due to the laterally inhomogeneous strain distribution within the disks. The optical emission of the thick (Al,Ga)N layer in the columns is spread out over a wide spectral range of several 100 meV, which is caused by an inhomogeneous incorporation of Al along the growth direction of the columns.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.60.Hk Cathodoluminescence, ionoluminescence

All-optical bistable switching in curved microfiber-coupled photonic crystal resonators

Myung-Ki Kim, In-Kag Hwang, Se-Heon Kim, Hyun-Joo Chang, and Yong-Hee Lee

Appl. Phys. Lett. 90, 161118 (2007); http://dx.doi.org/10.1063/1.2724921 (3 pages) | Cited 16 times

Online Publication Date: 18 April 2007

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The authors report low-power optical bistability under continuous wave pumping conditions in five-cell photonic crystal linear resonators containing InGaAsP quantum wells, by employing the fiber-coupling technique. The threshold bistable power is measured to be 35 μW at the normalized detuning of −1.724. Owing to the high band-edge nonlinearities of quantum wells and the efficient fiber coupling, minimal instability is observed. In addition, all-optical switching is demonstrated with switching energy less than 75.4 fJ.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.81.Qb Fiber waveguides, couplers, and arrays
42.70.Qs Photonic bandgap materials

Enhancing the photomixing efficiency of optoelectronic devices in the terahertz regime

Subrahmanyam Pilla

Appl. Phys. Lett. 90, 161119 (2007); http://dx.doi.org/10.1063/1.2724924 (3 pages)

Online Publication Date: 18 April 2007

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A method to enhance the photomixing efficiency by reducing the transit time of majority of carriers in photomixers and photodetectors to <1 ps is proposed. Enhanced optical fields associated with surface plasmon polaritons coupled with velocity overshoot phenomenon results in net decrease of transit time of carriers. As an example, model calculations demonstrating >280× (or ∼ 2800 and 31.8 μW at 1 and 5 THz, respectively) improvement in terahertz power generation efficiency of a photomixer based on low temperature grown GaAs are presented.
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42.82.Gw Other integrated-optical elements and systems
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
84.40.-x Radiowave and microwave (including millimeter wave) technology

Tunable ferroelectric photonic crystals based on porous silicon templates infiltrated by sodium nitrite

Tatyana V. Murzina, Fedor Yu. Sychev, Irina A. Kolmychek, and Oleg A. Aktsipetrov

Appl. Phys. Lett. 90, 161120 (2007); http://dx.doi.org/10.1063/1.2724928 (3 pages) | Cited 18 times

Online Publication Date: 18 April 2007

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Ferroelectric photonic band-gap (PBG) structures are fabricated by the infiltration of sodium nitrite into the nanoporous silicon templates composed by the electrochemical etching of n-type silicon. Reversible spectral tuning of the PBG and of the microcavity mode up to 15 nm is attained in the temperature interval from 50 to 165 °C due to the temperature changes of the refractive index of sodium nitrite in nanoporous silicon matrix. Optical second-harmonic generation measurements prove the ferroelectric state of the composed nanocomposite PBG structures.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.80.-e Ferroelectricity and antiferroelectricity
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Low Vπ modulators containing InGaAsP/InP microdisk phase modulators

Andrew Stapleton, Stephen Farrell, Zhen Peng, Seung-June Choi, Louis Christen, John O’Brien, P. Daniel Dapkus, and Alan Willner

Appl. Phys. Lett. 90, 161121 (2007); http://dx.doi.org/10.1063/1.2728035 (3 pages) | Cited 1 time

Online Publication Date: 18 April 2007

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The authors have demonstrated a low switching voltage modulator comprised of a 12 μm radius indium phosphide (InP)-based optical microdisk phase modulator in an external Mach-Zehnder interferometer. The chip-scale phase modulator operated with a measured Vπ of 0.6 mV.
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42.79.Hp Optical processors, correlators, and modulators
42.82.Gw Other integrated-optical elements and systems

Power enhancement in chemical oxygen-iodine lasers by iodine predissociation via corona/glow discharge

A. Katz, Z. Dahan, V. Rybalkin, K. Waichman, B. D. Barmashenko, and S. Rosenwaks

Appl. Phys. Lett. 90, 161122 (2007); http://dx.doi.org/10.1063/1.2728740 (3 pages) | Cited 12 times

Online Publication Date: 19 April 2007

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The gain and power in a supersonic chemical oxygen-iodine laser (COIL) are enhanced by applying dc corona/glow discharge in the transonic section of the secondary flow in the supersonic nozzle, dissociating I2 prior to its mixing with O2(1Δ). The loss of O2(1Δ) consumed for dissociation is thus reduced, and the consequent dissociation rate downstream of the discharge increases, resulting in up to 80% power enhancement. The implication of this method for COILs operating beyond the specific conditions reported here is assessed.
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42.55.Ks Chemical lasers
42.60.By Design of specific laser systems

Enhanced red electroluminescence from a polycrystalline diamond film/Si heterojunction structure

Xingbo Liang, Lei Wang, Xiangyang Ma, Dongsheng Li, Peihong Cheng, Deren Yang, Jun Chen, and Takashi Sekiguchi

Appl. Phys. Lett. 90, 161123 (2007); http://dx.doi.org/10.1063/1.2730584 (3 pages)

Online Publication Date: 19 April 2007

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Strongly enhanced red electroluminescence (EL) was realized at room temperature (RT) from a polycrystalline diamond film (PDF)/n−-Si heterojunction fabricated by direct chemical vapor deposition of PDF on silicon substrate. The red EL peaks featuring fairly narrow linewidth ( ∼ 12 nm) were obtained when the device was under sufficient reverse bias with the positive voltage applied on the silicon substrate. Cathodoluminescence spectra measured from 77 K to RT suggested that the enhanced red EL peaks originated from the neutral vacancy induced intrinsic defects of the PDF rather than the Si-related centers. The carrier transport mechanism of the PDF/n−-Si heterojunction was elucidated based on the proposed energy band diagram of the PDF/n−-Si heterojunction.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.60.Fi Electroluminescence
78.60.Hk Cathodoluminescence, ionoluminescence
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.J- Point defects and defect clusters

Enhancing or suppressing self-focusing in nonlinear photonic crystals

Xiaofang Yu, Xunya Jiang, and Shanhui Fan

Appl. Phys. Lett. 90, 161124 (2007); http://dx.doi.org/10.1063/1.2724905 (3 pages)

Online Publication Date: 19 April 2007

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The authors show that the effect of self-focusing can be controlled by exploiting spatial dispersion effects in a photonic crystal. In the positive refraction region, the critical field value for self-guiding can be significantly reduced. In the negative refraction region, the self-focusing effect can be completely suppressed in spite of a positive Kerr coefficient.
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42.70.Qs Photonic bandgap materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Neodymium doped sol-gel tapered waveguide amplifier

Asher Peled, Menachem Nathan, Alexander Tsukernik, and Shlomo Ruschin

Appl. Phys. Lett. 90, 161125 (2007); http://dx.doi.org/10.1063/1.2730577 (3 pages) | Cited 3 times

Online Publication Date: 20 April 2007

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The authors report the design, fabrication, and study of a fully monolithic solid-state amplifier based on a neodymium doped sol-gel tapered rib waveguide with a thin guiding layer of 360 nm. Signal (1064 nm) and pump (803 nm) light were coupled into and out of the amplifier by grating couplers. A gain of 4.8 dB (3.75 dB net internal gain) was obtained from a 1 cm long device.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.79.Gn Optical waveguides and couplers
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