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7 Feb 2011

Volume 98, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 063101 (2011); http://dx.doi.org/10.1063/1.3551574 (3 pages)

Y. Z. He, H. Li, P. C. Si, Y. F. Li, H. Q. Yu, X. Q. Zhang, F. Ding, K. M. Liew, and X. F. Liu
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Intersubband gain without global inversion through dilute nitride band engineering

Mauro F. Pereira, Jr. and Stanko Tomić

Appl. Phys. Lett. 98, 061101 (2011); http://dx.doi.org/10.1063/1.3552204 (3 pages) | Cited 1 time

Online Publication Date: 7 February 2011

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We investigate the possibility of interconduction band gain without global inversion by engineering the conduction band effective masses so that the upper lasing subband has an effective mass considerably smaller than the lower lasing subband that could not be obtained in conventional III-V materials. We recover the expected dispersive gain shape for similar masses and contrasting results if the effective masses characterizing the relevant subbands are very different.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Multifrequency terahertz lasing from codoped silicon crystals

S. G. Pavlov, R. Eichholz, N. V. Abrosimov, B. Redlich, and H.-W. Hübers

Appl. Phys. Lett. 98, 061102 (2011); http://dx.doi.org/10.1063/1.3553769 (3 pages) | Cited 3 times

Online Publication Date: 7 February 2011

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Stimulated terahertz emission in the range from 4.5 to 6.4 THz has been realized from a single silicon crystal doped by two hydrogen-like donor centers, phosphorus and antimony, when pumped by midinfrared radiation from a free electron laser. Intracenter as well as Raman lasing has been observed. Simultaneous laser emission from both donors occurs when the pump photon energy is sufficient for photoionization of the antimony donors. The laser processes of both donors are not influenced by each other. Therefore the codoping approach can be extended to other group-V donors including more than two dopants in a single crystal.
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42.50.Pq Cavity quantum electrodynamics; micromasers
42.55.Ye Raman lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Tunable single mode lasing from an on-chip optofluidic ring resonator laser

Wonsuk Lee, Hao Li, Jonathan D. Suter, Karthik Reddy, Yuze Sun, and Xudong Fan

Appl. Phys. Lett. 98, 061103 (2011); http://dx.doi.org/10.1063/1.3554362 (3 pages) | Cited 6 times

Online Publication Date: 8 February 2011

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Single mode lasing from the polydimethylsiloxane based on-chip coupled optofluidic ring resonator (OFRR) with the lasing threshold of a few μJ/mm2 is demonstrated using the Vernier effect. The single mode operation is highly stable even at high pump energy densities. The effect of the OFRR size and coupling strength on the single mode emission is investigated, showing that the excessive coupling results in incomplete side mode suppression. Tuning of the lasing wavelength is achieved by modifying the dye solution.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Sa Microcavity and microdisk lasers
42.82.Gw Other integrated-optical elements and systems
47.85.Np Fluidics
42.60.Fc Modulation, tuning, and mode locking

Ultrashort pulses characterization by nonlinear diffraction from virtual beam

A. S. Aleksandrovsky, A. M. Vyunishev, A. I. Zaitsev, A. A. Ikonnikov, and G. I. Pospelov

Appl. Phys. Lett. 98, 061104 (2011); http://dx.doi.org/10.1063/1.3554370 (3 pages) | Cited 6 times

Online Publication Date: 8 February 2011

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Noncollinear frequency doubling in a random nonlinear photonic crystal of strontium tetraborate via nonlinear diffraction from virtual beam is investigated. This effect is shown to be useful for ultrashort pulses characterization in broad spectral range. Nonlinear photonic crystals of strontium tetraborate are a promising medium for ultrafast diagnostics in short-wavelength applications.
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42.70.Mp Nonlinear optical crystals
42.70.Qs Photonic bandgap materials
42.25.Fx Diffraction and scattering
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Electroluminescence from amorphous-SiNx:H/SiO2 multilayers using lateral carrier injection

L. Kamyab, Rusli, M. B. Yu, L. Ding, and G.-Q. Lo

Appl. Phys. Lett. 98, 061105 (2011); http://dx.doi.org/10.1063/1.3553778 (3 pages) | Cited 1 time

Online Publication Date: 8 February 2011

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We report the observation of photoluminescence and electroluminescence from amorphous-SiNx:H/SiO2 multilayer structures. An effective method of current injection has been implemented for electrical excitation of these structures whereby the electric field is applied parallel to the plane of the multilayers. Compared to conventional electrical injection with current flowing normal to the plane of multilayers, this method has greatly improved the current density. Such structures are promising candidate as Si based light source for Si optoelectronics technology.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
73.40.-c Electronic transport in interface structures
78.55.Hx Other solid inorganic materials
78.60.Fi Electroluminescence

Terahertz/optical sum and difference frequency generation in liquids

Thomas Feil and S. J. Allen

Appl. Phys. Lett. 98, 061106 (2011); http://dx.doi.org/10.1063/1.3552964 (3 pages) | Cited 1 time

Online Publication Date: 9 February 2011

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A high-sensitivity setup for the observation of χ(2)-based, terahertz/optical, sum and difference frequency generation in liquids is presented. It relies on launching wavefront modulated terahertz radiation into a liquid traversed by an optical beam. Phase matching and polarization selection rules can be tuned to support three wave mixing via either chiral allowed electric dipole processes or higher order quadrupole/magnetic dipole processes. Under nonresonant excitation, hyperpolarizabilities from quadrupole/magnetic dipole processes are measured. Since this approach does not require terahertz transmission through macroscopic thicknesses of water, it has the potential to open a new window on the terahertz dynamics of water solvated molecules.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.An Optical susceptibility, hyperpolarizability
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Two-color terahertz response in bilayer graphene nanoribbons with spin-orbit coupling

Junfeng Liu, Bo Wang, Zhongshui Ma, and C. Zhang

Appl. Phys. Lett. 98, 061107 (2011); http://dx.doi.org/10.1063/1.3555631 (3 pages) | Cited 1 time

Online Publication Date: 10 February 2011

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We demonstrate that spin-orbit coupling can give rise to a strong terahertz response in metallic armchair bilayer graphene nanoribbons. The combination of the interlayer coupling and the spin-orbit coupling leads to double resonant optical response in the low frequency regime. The frequency separation of the two excitations is tunable with a gate voltage.
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78.70.Gq Microwave and radio-frequency interactions
78.67.Wj Optical properties of graphene
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.22.Pr Electronic structure of graphene

Germanium-tin p-i-n photodetectors integrated on silicon grown by molecular beam epitaxy

J. Werner, M. Oehme, M. Schmid, M. Kaschel, A. Schirmer, E. Kasper, and J. Schulze

Appl. Phys. Lett. 98, 061108 (2011); http://dx.doi.org/10.1063/1.3555439 (3 pages) | Cited 15 times

Online Publication Date: 10 February 2011

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GeSn heterojunction p-i-n diodes with a Sn content of 0.5% are grown with a special low temperature molecular beam epitaxy. The Sn incorporation in Ge is facilitated by a very low temperature growth step in order to suppress Sn surface segregation. Diodes with sharp doping transitions are realized as double mesa structures with a diameter from 1.5 up to 80 μm. An optical responsivity of these GeSn diodes of 0.1 A/W at a wavelength of λ = 1.55 μm is measured. In comparison with a pure Ge detector the optical responsivity is increased by factor of 3 as a result of Sn caused band gap reduction.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
61.72.uj III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Direct gap electroluminescence from Si/Ge1−ySny p-i-n heterostructure diodes

R. Roucka, J. Mathews, R. T. Beeler, J. Tolle, J. Kouvetakis, and J. Menéndez

Appl. Phys. Lett. 98, 061109 (2011); http://dx.doi.org/10.1063/1.3554747 (3 pages) | Cited 13 times

Online Publication Date: 11 February 2011

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Electroluminescence spectra from Si/Ge1−ySny heterostructure diodes are reported. The observed emission is dominated by direct gap optical transitions and displays the expected compositional dependence of the peak energy. Weaker indirect gap emission is also observed, and their energies are consistent with a closing of the indirect-direct separation as the Sn concentration is increased. The intensity of the EL spectra shows a superlinear dependence on the injection current, which is modeled using a Van Roosbroeck–Shockley expression for the emission intensity. The model assumes quasiequilibrium conditions for the electrons populating the different valleys in the conduction band of Ge.
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85.30.Kk Junction diodes
85.60.Jb Light-emitting devices

Single-mode quantum cascade lasers based on a folded Fabry-Perot cavity

Peter Q. Liu, Xiaojun Wang, Jen-Yu Fan, and Claire F. Gmachl

Appl. Phys. Lett. 98, 061110 (2011); http://dx.doi.org/10.1063/1.3554757 (3 pages) | Cited 2 times

Online Publication Date: 11 February 2011

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We demonstrate single-mode quantum cascade lasers employing a folded Fabry-Perot cavity consisting of two straight sections connected by a semicircular section in a “hairpin” shape. These folded cavity lasers emitting at ∼ 4.5 μm are fabricated with identical processes as those for plain Fabry-Perot ridge lasers, and show a strong suppression of the comb of Fabry-Perot cavity modes, leading to tunable single-mode emission with up to 27 dB side mode suppression ratio and a single-mode operating current range of up to 60% above the threshold current when operated in pulsed mode; single-mode emission is achieved from 80 to ∼ 240 K.
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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
42.60.Fc Modulation, tuning, and mode locking

Nondiffracting kagome lattice

Martin Boguslawski, Patrick Rose, and Cornelia Denz

Appl. Phys. Lett. 98, 061111 (2011); http://dx.doi.org/10.1063/1.3554759 (3 pages) | Cited 4 times

Online Publication Date: 11 February 2011

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We introduce a generalized approach to generate an elementary nondiffracting beam, whose transverse intensity is distributed corresponding to a two-dimensional kagome structure. Furthermore, we present an effective experimental implementation via a computer controlled phase controlling spatial light modulator in combination with a specific Fourier filter system. Intensity and phase analysis of the kagome lattice beam accounts for an experimental wave field implementation. Altogether, the examined wave field may be a fundament for the fabrication of large two-dimensional photonic crystals or photonic lattices in kagome symmetry using miscellaneous holographic matter structuring techniques.
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42.79.Hp Optical processors, correlators, and modulators
42.30.Kq Fourier optics
42.79.Ci Filters, zone plates, and polarizers

A terahertz pulse emitter monolithically integrated with a quantum cascade laser

David Burghoff, Tsung-Yu Kao, Dayan Ban, Alan Wei Min Lee, Qing Hu, and John Reno

Appl. Phys. Lett. 98, 061112 (2011); http://dx.doi.org/10.1063/1.3553021 (3 pages) | Cited 6 times

Online Publication Date: 11 February 2011

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A terahertz pulse emitter monolithically integrated with a quantum cascade laser (QCL) is demonstrated. The emitter facet is excited by near-infrared pulses from a mode-locked Ti:sapphire laser, and the resulting current transients generate terahertz pulses that are coupled into an electrically isolated QCL in proximity. These pulses are used to measure the gain of the laser transition at ∼ 2.2 THz, which clamps above threshold at ∼ 18 cm−1 and has a full width at half-maximum linewidth of ∼ 0.67 THz. The measurement also shows the existence of absorption features at different biases that correspond to misalignment of the band structure and to absorption within the two injector states. The simplicity of this scheme allows it to be implemented alongside standard QCL ridge processing and to be used as a versatile tool for characterizing QCL gain media.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.82.-m Integrated optics
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Measurement of the valence band structure in dielectric films by a focused ion beam

Han S. Uhm, Young J. Hong, Eun H. Choi, and Do Y. Kim

Appl. Phys. Lett. 98, 061501 (2011); http://dx.doi.org/10.1063/1.3554433 (3 pages) | Cited 4 times

Online Publication Date: 9 February 2011

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The measured profile of the energy distribution of electrons emitted from dielectric films due to the Auger neutralization of incoming ions is rescaled to facilitate the Auger self-convolution, which illustrates the details of the valence band. As an application for this research scheme, the properties of the valence band in MgO layers are investigated in terms of the measured Auger self-convolution, indicating that the state density is a decaying function of the energy deviation from the band of ε0 = 7.63 eV, although a numerical calculation shows a spiky structure of the state density in the valence band.
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71.20.Ps Other inorganic compounds
73.20.At Surface states, band structure, electron density of states
77.55.-g Dielectric thin films
79.20.Hx Electron impact: secondary emission

Highly collimated electron beams from double-gate field emitter arrays with large collimation gate apertures

P. Helfenstein, E. Kirk, K. Jefimovs, T. Vogel, C. Escher, H.-W. Fink, and S. Tsujino

Appl. Phys. Lett. 98, 061502 (2011); http://dx.doi.org/10.1063/1.3551541 (3 pages) | Cited 7 times

Online Publication Date: 9 February 2011

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Electron collimation in field emitter arrays with electron extraction gate and collimation gate electrodes is studied with the goal to develop a high-brightness high current cathode. Using metallic field emitter arrays prepared by the molding method, we fabricated a stacked double-gate device with the two gates differing in diameter by a process utilizing focused-ion beam milling. We measured the field-emission beam characteristics and demonstrated a reduction of the emission angle by a factor of 7.1±0.8 with minimal emission current decrease under collimating conditions, resulting in a current density increase by a factor of 13.9±1.0.
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85.45.Db Field emitters and arrays, cold electron emitters
82.45.Fk Electrodes
81.20.Wk Machining, milling

Experimental demonstration of Smith–Purcell radiation enhancement by frequency multiplication in open cavity

V. L. Bratman, A. E. Fedotov, and P. B. Makhalov

Appl. Phys. Lett. 98, 061503 (2011); http://dx.doi.org/10.1063/1.3554435 (3 pages) | Cited 3 times

Online Publication Date: 10 February 2011

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The excitation of a low-frequency surface wave can provide coherent high-frequency Smith–Purcell radiation due to the frequency multiplication effect. The use of an open cavity allows an additional power increase due to the induced nature of the radiation. A radiation source based on these effects is experimentally demonstrated at a frequency of about 190 GHz.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
84.30.Ng Oscillators, pulse generators, and function generators
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InN/InGaN multiple quantum wells emitting at 1.5 μm grown by molecular beam epitaxy

J. Grandal, J. Pereiro, A. Bengoechea-Encabo, S. Fernández-Garrido, M. A. Sánchez-García, E. Muñoz, E. Calleja, E. Luna, and A. Trampert

Appl. Phys. Lett. 98, 061901 (2011); http://dx.doi.org/10.1063/1.3552195 (3 pages) | Cited 4 times

Online Publication Date: 7 February 2011

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This work reports on the growth by molecular beam epitaxy and characterization of InN/InGaN multiple quantum wells (MQWs) emitting at 1.5 μm. X-ray diffraction (XRD) spectra show satellite peaks up to the second order. Estimated values of well (3 nm) and barrier (9 nm) thicknesses were derived from transmission electron microscopy and the fit between experimental data and simulated XRD spectra. Transmission electron microscopy and XRD simulations also confirmed that the InGaN barriers are relaxed with respect to the GaN template, while the InN MQWs grew under biaxial compression on the InGaN barriers. Low temperature (14 K) photoluminescence measurements reveal an emission from the InN MQWs at 1.5 μm. Measurements as a function of temperature indicate the existence of localized states, probably due to InN quantum wells’ thickness fluctuations as observed by transmission electron microscopy.
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68.65.Fg Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.21.Fg Quantum wells
78.55.Cr III-V semiconductors
78.67.De Quantum wells
68.55.ag Semiconductors

An analytical model of strain isolation for stretchable and flexible electronics

H. Cheng, J. Wu, M. Li, D.-H. Kim, Y.-S. Kim, Y. Huang, Z. Kang, K. C. Hwang, and J. A. Rogers

Appl. Phys. Lett. 98, 061902 (2011); http://dx.doi.org/10.1063/1.3553020 (3 pages) | Cited 3 times

Online Publication Date: 7 February 2011

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One important aspect of stretchable electronics design is to shield the active devices from strains through insertion of a soft layer between devices and substrate. An analytical model is established, which gives linear dependence of strain isolation on the reciprocal of strain-isolation layer thickness, and the reciprocal of device and substrate stiffness. Strain isolation is also linearly proportional to the shear modulus of strain-isolation layer and square of device length.
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85.30.De Semiconductor-device characterization, design, and modeling

Selective control of polarized emission from patterned GaN/AlN quantum dot ensembles on Si(111)

O. Moshe, D. H. Rich, B. Damilano, and J. Massies

Appl. Phys. Lett. 98, 061903 (2011); http://dx.doi.org/10.1063/1.3554371 (3 pages) | Cited 3 times

Online Publication Date: 9 February 2011

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GaN/AlN quantum dots (QDs) were grown by the Stranski–Krastanov method on Si(111). The thermal expansion coefficient mismatch between the Si substrate and GaN/AlN film leads to an additional biaxial tensile stress of 20–30 kbar in the III-nitride film, which we have selectively modified by etching a cross-hatched pattern into the as-grown sample. The results show that a suitable choice of stripe orientation and width from ∼ 2 to 10 μm can create regions of in-plane uniaxial stress that enable a selective and local control of the polarized luminescence from ensembles of QDs which were probed with cathodoluminescence.
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81.07.Ta Quantum dots
78.67.Hc Quantum dots
78.60.Hk Cathodoluminescence, ionoluminescence
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems

Metamagnetic phase transformation in Mn50Ni37In10Co3 polycrystalline alloy

Zhigang Wu, Zhuhong Liu, Hong Yang, Yinong Liu, and Guangheng Wu

Appl. Phys. Lett. 98, 061904 (2011); http://dx.doi.org/10.1063/1.3554423 (3 pages) | Cited 7 times

Online Publication Date: 9 February 2011

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This letter reports on an alloy design of Mn50Ni37In10Co3 based on the principle of Mn-Mn ferromagnetic coupling via Co doping. The alloy is shown to exhibit a metamagnetic martensitic transformation and a high saturation magnetization of 118 emu/g in its austenitic state. The transformation generates a large magnetization difference of 89 emu/g, more than 200% of what is reported in the literature for similar alloys. A complete magnetic field induced martensitic transformation was achieved at 170 K. Such a high magnetization difference provides a strong driving force for magnetic-field-induced transformation, making this material a promising candidate for magnetic actuation applications.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.30.Kf Martensitic transformations
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys

The enhanced binding energy for biexcitons in InAs quantum dots

Yasuaki Masumoto, Seitaro Yoshida, Michio Ikezawa, Shinichi Tomimoto, and Yoshiki Sakuma

Appl. Phys. Lett. 98, 061905 (2011); http://dx.doi.org/10.1063/1.3554425 (3 pages)

Online Publication Date: 9 February 2011

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We observed that the biexciton binding energy in InAs quantum rhombic disks (QRDs) is enhanced by twice compared with that for InAs quantum dots (QDs) so far reported around 1.24 μm nearby the telecommunication wavelength. The heterodyne-detected four-wave-mixing detected the exciton-biexciton quantum beat superposed on photon echo decay, giving the biexciton binding energy of 3.4 meV to 3 monolayer (ML) InAs QRDs and 4.1 meV to 4 ML InAs QRDs, respectively. The largest biexciton binding energy of 4.1 meV in InAs QDs is ascribed to increased electron-hole overlap in confined geometry with a minimized strain distribution.
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73.21.La Quantum dots
78.67.Hc Quantum dots
71.35.-y Excitons and related phenomena
78.47.jm Quantum beats
78.47.jf Photon echoes
62.23.Eg Nanodots

Phonon deformation potentials in wurtzite GaN and ZnO determined by uniaxial pressure dependent Raman measurements

G. Callsen, J. S. Reparaz, M. R. Wagner, R. Kirste, C. Nenstiel, A. Hoffmann, and M. R. Phillips

Appl. Phys. Lett. 98, 061906 (2011); http://dx.doi.org/10.1063/1.3554434 (3 pages) | Cited 4 times

Online Publication Date: 9 February 2011

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We report the phonon deformation potentials of wurtzite GaN and ZnO for all zone center optical phonon modes determined by Raman measurements as a function of uniaxial pressure. Despite all the structural and optical similarities between these two material systems, the pressure dependency of their vibrational spectra exhibits fundamental distinctions, which is attributed to their different bond ionicities. In addition, the LO-TO splitting of the A1 and E1 phonon modes is analyzed which yields insight into the uniaxial pressure dependency of Born’s transverse effective charge eT∗.
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78.30.Fs III-V and II-VI semiconductors
81.40.Vw Pressure treatment
62.20.F- Deformation and plasticity
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
81.40.Lm Deformation, plasticity, and creep

A comparative study of photoluminescence of Zn-polar and O-polar faces in single crystal ZnO using moment analysis

Aishi Yamamoto, Yuta Moriwaki, Ken Hattori, and Hisao Yanagi

Appl. Phys. Lett. 98, 061907 (2011); http://dx.doi.org/10.1063/1.3554722 (3 pages) | Cited 2 times

Online Publication Date: 9 February 2011

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We report on differences in photoluminescence (PL) spectra between Zn-polar and O-polar faces in single crystal ZnO. The PL intensity ratios of one phonon to two phonon replicas of free-excitons in the two polar faces were found to be the same. This result clearly indicates that exciton-phonon coupling strengths in both faces are the same. From moment analysis, however, the relative PL intensity of the zero-phonon free-excitons in the O-polar face was larger than that in the Zn-polar face. We propose that the opposite band bending at the two polar faces causes the difference in the PL properties.
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78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
63.20.kk Phonon interactions with other quasiparticles

Triaxial stress distributions in Cu/low-k interconnect features

Conal E. Murray, Paul R. Besser, E. Todd Ryan, and Jean L. Jordan-Sweet

Appl. Phys. Lett. 98, 061908 (2011); http://dx.doi.org/10.1063/1.3549876 (3 pages) | Cited 3 times

Online Publication Date: 9 February 2011

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The distribution of triaxial stresses within single damascene Cu/organosilicate interconnect structures as a function of linewidth, ranging from 45 to 250 nm, was measured using x-ray diffraction. Least-squares minimization techniques were employed to determine the volume-averaged stress tensors of the Cu features. Longitudinal Cu stress values increased for linewidths below 100 nm, while transverse stresses decreased with decreasing linewidth below 100 nm due to the interplay between the Cu microstructure and the feature geometry. Large tensile out-of-plane stresses were observed in all of the lines demonstrating the constraint imposed by the barrier layers that encapsulate the Cu.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
77.55.Bh Low-permittivity dielectric films

Observation of tunneling of slow and fast electromagnetic modes in coupled periodic waveguides

Sangwoo Ha, Andrey A. Sukhorukov, Andrei V. Lavrinenko, Ilya V. Shadrivov, David A. Powell, and Yuri S. Kivshar

Appl. Phys. Lett. 98, 061909 (2011); http://dx.doi.org/10.1063/1.3553785 (3 pages) | Cited 3 times

Online Publication Date: 9 February 2011

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We report the experimental observation of tunneling of slow and fast electromagnetic modes in coupled periodic waveguides shifted longitudinally by half of modulation period. According to the symmetry analysis, such a coupler supports two electromagnetic modes with exactly matched slow or fast group velocities but different phase velocities for frequencies close to the edge of the photonic band. We confirm the predicted properties of the modes by directly extracting their dispersion and group velocities from the near-field measurements using specialized Bloch-wave spectral analysis method.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
84.40.Az Waveguides, transmission lines, striplines

Carrier dynamics between delocalized and localized states in type-II GaAsSb/GaAs quantum wells

M. Baranowski, M. Syperek, R. Kudrawiec, J. Misiewicz, J. A. Gupta, X. Wu, and R. Wang

Appl. Phys. Lett. 98, 061910 (2011); http://dx.doi.org/10.1063/1.3548544 (3 pages) | Cited 1 time

Online Publication Date: 10 February 2011

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The carrier dynamics in type-II GaAsSb/GaAs quantum well (QW) is investigated by time-resolved photoluminescence at low temperature. A detailed analysis of the experimental data reveal a complex carrier relaxation scenario involving both delocalized and localized states. We show that the QW emission is controlled by the dynamics of the band bending effect, related to temporal changes in the spatial charge separation near the GaAsSb/GaAs heterointerface, whereas localized states play a significant role in the carrier relaxation/redistribution between QW states.
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73.21.Fg Quantum wells
78.47.jd Time resolved luminescence
78.55.Cr III-V semiconductors
78.67.De Quantum wells
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