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29 Aug 2005

Volume 87, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 093109 (2005); http://dx.doi.org/10.1063/1.2035332 (3 pages)

J. Noborisaka, J. Motohisa, S. Hara, and T. Fukui
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Power splitters for waveguides composed by ultralow refractive index metallic nanostructures

V. F. Rodríguez-Esquerre, M. Koshiba, H. E. Hernández-Figueroa, and C. E. Rubio-Mercedes

Appl. Phys. Lett. 87, 091101 (2005); http://dx.doi.org/10.1063/1.2033132 (3 pages) | Cited 4 times

Online Publication Date: 22 August 2005

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The power splitting properties of metallic photonic crystal waveguides, where the mechanism of propagation is the total external reflection, are investigated. These waveguides are composed by an air core surrounded by a cladding formed by a periodic arrangement of metallic wires on square or triangular lattices. Power splitters can be achieved by modifying the geometry at the splitting region by introducing a reflecting structure in order to increase the transmission coefficient; some splitters based on these structures are analyzed by an efficient frequency domain finite element approach. The proposed concept may open the possibility to design more sophisticated devices based on these waveguides and splitters.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials
42.79.Fm Reflectors, beam splitters, and deflectors

Experimentally demonstrated filters based on guided resonance of photonic-crystal films

Chunchen Lin, Zhaolin Lu, Shouyuan Shi, Ge Jin, and Dennis W. Prather

Appl. Phys. Lett. 87, 091102 (2005); http://dx.doi.org/10.1063/1.2033134 (3 pages) | Cited 6 times

Online Publication Date: 22 August 2005

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We demonstrate a guided resonance filter based on photonic crystals (PhCs), which are fabricated in a high-permittivity material. The resulting spectra from a three-dimensional analysis of the structure and experimental measurement results show sharp dips and flattop transmissions. These provide promising properties in constructing sensitive and compact wavelength-selective devices, such as wavelength-division multiplexers.
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42.79.Ci Filters, zone plates, and polarizers
42.70.Qs Photonic bandgap materials
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.79.Wc Optical coatings
42.86.+b Optical workshop techniques

Silver halide single-mode fibers for the middle infrared

S. Shalem, A. Tsun, E. Rave, A. Millo, L. Nagli, and A. Katzir

Appl. Phys. Lett. 87, 091103 (2005); http://dx.doi.org/10.1063/1.2034102 (3 pages) | Cited 15 times

Online Publication Date: 22 August 2005

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There is an interest in single-mode fibers that are highly transparent in the middle infrared. Such fibers would be valuable for spectroscopy, interferometry, fiber lasers, and heterodyne detection. We developed core-clad fibers made of crystalline silver halides, with external diameter 900 μm, small core diameters (50–60 μm) and an extremely small difference ( ∼ 0.004) between the indices of refraction of the core and the clad. These fibers behaved as single-mode fibers at the wavelength 10.6 μm.
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42.81.Bm Fabrication, cladding, and splicing
42.81.Wg Other fiber-optical devices

Subwavelength imaging with opaque nonlinear left-handed lenses

Alexander A. Zharov, Nina A. Zharova, Ilya V. Shadrivov, and Yuri S. Kivshar

Appl. Phys. Lett. 87, 091104 (2005); http://dx.doi.org/10.1063/1.2034114 (3 pages) | Cited 24 times

Online Publication Date: 22 August 2005

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We consider a slab of a composite left-handed metamaterial with quadratic nonlinear response and discuss the properties of opaque nonlinear left-handed lens. We find the conditions when this left-handed flat lens can create, with a subwavelength resolution, an image of the second-harmonic field of the source being opaque for the fundamental frequency.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.25.Bs Wave propagation, transmission and absorption
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Qs Photonic bandgap materials

Enhanced optical transmission through metal films with rotation-symmetrical hole arrays

Qian-jin Wang, Jia-qi Li, Cheng-ping Huang, Chao Zhang, and Yong-yuan Zhu

Appl. Phys. Lett. 87, 091105 (2005); http://dx.doi.org/10.1063/1.2034120 (3 pages) | Cited 25 times

Online Publication Date: 22 August 2005

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The transmission of light through metal surface with subwavelength holes are influenced by many factors, and the rotational symmetry of hole arrays can be one of them. In this paper, we fabricated the hole lattices in metal films with different symmetry and measured the transmission spectra from the visible to near-infrared region. It is found that both the spectrum shape and the transmission efficiency are strongly dependent on the rotational symmetry. The spectrum shape is governed by the reciprocal vectors. And the higher is the symmetry order, the larger the peak efficiency. The results provide us with new insight into the unusual effect.
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78.66.Bz Metals and metallic alloys
78.40.Kc Metals, semimetals, and alloys
78.30.Er Solid metals and alloys

Vacuum laser-driven acceleration by two slits-truncated Bessel beams

D. Li and K. Imasaki

Appl. Phys. Lett. 87, 091106 (2005); http://dx.doi.org/10.1063/1.2035870 (3 pages) | Cited 2 times

Online Publication Date: 23 August 2005

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An approach of vacuum acceleration by two laser Bessel beams is presented in this letter. With elaborate arrangement, the two Bessel beams are truncated by a set of special annular slits to form consecutive acceleration field in the electron traveling direction. Therefore, the electron of a certain initial energy can be accelerated in the whole interaction region without experiencing deceleration even though the phase-slippage occurs. Furthermore, the Bessel beam can provide a rather long distance for the effective interaction between the electron and the laser field due to its “diffraction-free” property, resulting in improvement of the energy exchange.
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42.62.-b Laser applications
29.27.-a Beams in particle accelerators

Persistent spectral hole burning in europium-doped sodium tellurite glass

Chandra R. Pulluru, Rajamohan R. Kalluru, B. Rami Reddy, Tatyana A. Konovalova, and Lowell D. Kispert

Appl. Phys. Lett. 87, 091107 (2005); http://dx.doi.org/10.1063/1.2035884 (3 pages) | Cited 3 times

Online Publication Date: 23 August 2005

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We have prepared sodium tellurite glasses doped with europium. Emission intensity of the europium-doped glass is at least 500× more than that of the undoped glass. Fluorescence features exhibited dependence on the pump laser wavelength. Persistent spectral hole burning was observed in the math→math transition of Eu3+. Multiple hole burning was possible even if the chemicals were melted in ambient air to make the glass. The hole burning mechanism is also explained. Electron spin resonance measurements confirmed the existence of defect centers.
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42.70.Ce Glasses, quartz
42.65.-k Nonlinear optics
78.55.Hx Other solid inorganic materials
78.55.Qr Amorphous materials; glasses and other disordered solids
76.30.Kg Rare-earth ions and impurities
61.72.up Other materials

Electrically injected spin-polarized vertical-cavity surface-emitting lasers

M. Holub, J. Shin, S. Chakrabarti, and P. Bhattacharya

Appl. Phys. Lett. 87, 091108 (2005); http://dx.doi.org/10.1063/1.2035329 (3 pages) | Cited 22 times

Online Publication Date: 24 August 2005

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We report the design, fabrication, and characterization of an electrically injected, spin-polarized, vertical-cavity surface-emitting laser. We have demonstrated spin injection from the ferromagnetic semiconductor (Ga,Mn)As into In0.2Ga0.8As/GaAs quantum wells, spin transport across a distance of ∼ 0.25 μm for temperatures ranging from 80 to 105 K, and spin detection through optical polarization measurements with coherent light emission. Controlled switching between right- and left-elliptically polarized modes is achieved with a maximum degree of circular polarization of 4.6% measured at 80 K.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
42.86.+b Optical workshop techniques

Li- and Er-codoped ZnO with enhanced 1.54 μm photoemission

Zhen Zhou, Toshitaka Komori, Tatsuya Ayukawa, Hiroshi Yukawa, Masahiko Morinaga, Atsushi Koizumi, and Yoshikazu Takeda

Appl. Phys. Lett. 87, 091109 (2005); http://dx.doi.org/10.1063/1.2035867 (3 pages) | Cited 34 times

Online Publication Date: 24 August 2005

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Lithium ions were introduced into Er-doped ZnO specimens, and the codoping effect was investigated on the photoluminescence (PL) spectra around 1.54 μm. It was found that the Li addition increased the PL intensity by about 90 times at most, and also the strongest peak position shifted from 1.534 μm to 1.539 μm. The enhancement in the PL intensity could be attributed to the modification of the local symmetry and structure around Er3+ by Li ions. The Li ions can be introduced easily into the Er-doped ZnO and other semiconductor hosts, and is therefore a very useful element in the practical fabrication of the optoelectronic devices.
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78.55.Et II-VI semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.72.uj III-V and II-VI semiconductors

Liquid-crystal beam steering device with a photopolymer prism

Jae-Hong Park and Iam Choon Khoo

Appl. Phys. Lett. 87, 091110 (2005); http://dx.doi.org/10.1063/1.2035869 (3 pages) | Cited 3 times

Online Publication Date: 24 August 2005

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We report on liquid-crystal (LC) beam steering device with a photopolymer prism produced by ultraviolet exposure. The method for producing the prism is based on the diffusion process of the prepolymer during photopolymerization. No chemical etching is needed. Our LC device gives complete single-order diffraction and a controllable steering over ∼ 1° with an applied ac voltage of 5 V. The experimental data, together with the simulation results with respect to electrical steering properties, are presented.
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42.79.Kr Display devices, liquid-crystal devices
42.79.Bh Lenses, prisms and mirrors
42.70.Jk Polymers and organics

Two-color pump–probe experiments on silicon inverse opals

C. Becker, S. Linden, G. von Freymann, M. Wegener, N. Tétreault, E. Vekris, V. Kitaev, and G. A. Ozin

Appl. Phys. Lett. 87, 091111 (2005); http://dx.doi.org/10.1063/1.2035873 (3 pages) | Cited 17 times

Online Publication Date: 24 August 2005

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We present time-resolved pump–probe experiments in a transmission geometry using off-resonant excitation on very high-quality silicon inverse opals. We show that the nonlinear optical response can drastically be modified by tempering of the sample. The as-grown samples are dominated by an absorptive response with recovery times as short as one picosecond. For the tempered samples, both the relaxation and the scattering times increase, leading to a prominent dispersive response. Based on simple calculations using the Drude model, we estimate corresponding refractive index changes as large as Δn = −0.5+i0.07.
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78.47.-p Spectroscopy of solid state dynamics
42.65.-k Nonlinear optics
42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Thermal annealing of magneto-optical (Cd,Mn)Te waveguides for optical isolators with wider operational wavelength range

M. C. Debnath, V. Zayets, and K. Ando

Appl. Phys. Lett. 87, 091112 (2005); http://dx.doi.org/10.1063/1.2037196 (3 pages) | Cited 2 times

Online Publication Date: 25 August 2005

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We obtained significant improvement of magneto-optical performance by thermal annealing of the graded-index Cd1−xMnxTe waveguide. For a waveguide annealed at 425 °C, complete mode conversion was achieved in a wavelength range between 710 and 735 nm, which is an expansion of more than eight times that of a waveguide without annealing. The annealed waveguide also showed very low optical loss of 0.2 dB/cm and a high magneto-optical figure-of-merit of more than 1000 deg/dB/kG. In addition, an isolation ratio of more than 20 dB was obtained at λ = 715–735 nm in magnetic fields, H = 1.6–5.1 kG. This result is an important step toward achieving a practical integrated optical isolator.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
85.70.Sq Magnetooptical devices
61.72.Cc Kinetics of defect formation and annealing
42.79.Ry Gradient-index (GRIN) devices

Optical diffraction of second-harmonic signals in the LiBO2-Nb2O5 glasses induced by self-organized LiNbO3 crystallites

B. Harihara Venkataraman, N. Syam Prasad, K. B. R. Varma, Vincent Rodriguez, Mario Maglione, R. Vondermuhll, and J. Etourneau

Appl. Phys. Lett. 87, 091113 (2005); http://dx.doi.org/10.1063/1.2037198 (3 pages) | Cited 17 times

Online Publication Date: 25 August 2005

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The nanocrystallites ( ≈ 3 nm) of LiNbO3, evolved in the (100−x)LiBO2-xNb2O5 (5 ⩽ x ⩽ 20, in molar ratio) glass system exhibited intense second-harmonic signals in transmission mode when exposed to infrared (IR) light at λ = 1064 nm. The second-harmonic waves were found to undergo optical diffraction which was attributed to the presence of self-organized submicrometer-sized LiNbO3 crystallites that were grown within the glass matrix along the parallel damage fringes created by the IR laser radiation. Micro-Raman studies carried out on the laser-irradiated samples confirmed the self-organized crystallites to be LiNbO3.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Ce Glasses, quartz
78.30.Hv Other nonmetallic inorganics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Simulation and testing of a graded negative index of refraction lens

R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, M. A. Thompson, M. H. Tanielian, and D. R. Smith

Appl. Phys. Lett. 87, 091114 (2005); http://dx.doi.org/10.1063/1.2037202 (3 pages) | Cited 30 times

Online Publication Date: 25 August 2005

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A gradient index (GRIN) lens using a negative index of refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable index of refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the index of refraction gradient required for a given focal length. An electromagnetic code was then used to design the required ring and wire unit cells. Finally, the index of refraction was approximated using ten discrete steps in an effective medium simulation for the GRIN lens that agreed with the experimental measurements.
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42.79.Bh Lenses, prisms and mirrors
42.79.Ry Gradient-index (GRIN) devices
42.87.-d Optical testing techniques
42.15.Eq Optical system design
42.15.Dp Wave fronts and ray tracing
42.86.+b Optical workshop techniques

InGaAsN/GaAs quantum-well lasers using two-step and nitride passivation growth

Pei-Chin Chiu, Nien-Tze Yeh, Chao-Chi Hong, Tung Po Hsieh, Yao-Tsong Tsai, Wen-Jeng Ho, and Jen-Inn Chyi

Appl. Phys. Lett. 87, 091115 (2005); http://dx.doi.org/10.1063/1.2037857 (3 pages) | Cited 1 time

Online Publication Date: 25 August 2005

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The optical properties of InGaAsN QW grown on AlGaAs/GaAs cladding layers were investigated. Al contamination in the quantum well due to the memory effect is responsible for the degradation of optical quality. We propose a growth method to reduce the Al contamination by growth interruption and dimethylhydrazine passivation. This approach improves the optical properties as well as simplifies the growth processes significantly as compared to the reported methods.
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42.55.Px Semiconductor lasers; laser diodes
81.65.Rv Passivation
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Bound-to-bound midinfrared intersubband absorption in carbon-doped GaAs/AlGaAs quantum wells

Oana Malis, Loren N. Pfeiffer, Kenneth W. West, A. Michael Sergent, and Claire Gmachl

Appl. Phys. Lett. 87, 091116 (2005); http://dx.doi.org/10.1063/1.2037859 (3 pages) | Cited 4 times

Online Publication Date: 25 August 2005

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Bound-to-bound intersubband absorption in the valence band of modulation-doped GaAs quantum wells with digitally alloyed AlGaAs barriers was studied in the midinfrared wavelength range. A high-purity solid carbon source was used for the p-type doping. Strong narrow absorption peaks due to heavy-to-heavy hole transitions are observed with out-of-plane polarized light, and weaker broader features with in-plane polarized light. The heavy-to-heavy hole transition energy spans the spectral range between 206 to 126 meV as the quantum well width is increased from 25 to 45 Å. The experimental results are found to be in agreement with calculations of a six-band k∙p model taking into account the full band structure of the digital alloy.
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78.67.De Quantum wells
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
71.15.-m Methods of electronic structure calculations
61.72.uj III-V and II-VI semiconductors

Optical tuning of three-dimensional photonic crystals fabricated by femtosecond direct writing

Dennis McPhail, Martin Straub, and Min Gu

Appl. Phys. Lett. 87, 091117 (2005); http://dx.doi.org/10.1063/1.2037862 (3 pages) | Cited 14 times

Online Publication Date: 25 August 2005

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In this letter, we report on an optically tunable three-dimensional photonic crystal that exhibits main gaps in the 3–4 μm range. The photonic crystal is manufactured via a femtosecond direct writing technique. Optical tuning is achieved by a luminary polling technique with a low-power polarized laser beam. The refractive index variation resulting from liquid-crystal rotation causes a shift in the photonic band gap of up to 65 nm with an extinction of transmission of up to 70% in the stacking direction. Unlike other liquid-crystal tuning techniques where a pregenerated structure is infiltrated, this optical tuning method is a one-step process that allows arbitrary structures to be written into a solid liquid-crystal-polymer composite and leads to a high dielectric contrast.
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42.70.Qs Photonic bandgap materials
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.62.-b Laser applications
42.86.+b Optical workshop techniques
42.70.Df Liquid crystals

Surface plasmon enhanced photon drag in metal films

Arvind S. Vengurlekar and Teruya Ishihara

Appl. Phys. Lett. 87, 091118 (2005); http://dx.doi.org/10.1063/1.2037851 (3 pages) | Cited 5 times

Online Publication Date: 26 August 2005

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We report a significantly enhanced photon drag effect (PDE) in a Au thin film at the surface plasmon resonance when the film is mounted in the Kretschmann-Raether geometry. The PDE is observed in the form of an electrical direct current induced by optical excitation. We discuss a model to describe how excitation of surface plasmons may give rise to a current in the Au thin film.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Bz Metals and metallic alloys
73.61.At Metal and metallic alloys
73.50.Pz Photoconduction and photovoltaic effects
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Photoluminescence in erbium doped amorphous silicon oxycarbide thin films

Spyros Gallis, Mengbing Huang, Harry Efstathiadis, Eric Eisenbraun, Alain E. Kaloyeros, Ei Ei Nyein, and Uwe Hommerich

Appl. Phys. Lett. 87, 091901 (2005); http://dx.doi.org/10.1063/1.2032600 (3 pages) | Cited 15 times

Online Publication Date: 22 August 2005

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Photoluminescence (PL) in Er-doped amorphous silicon oxycarbide (a-SiCxOy:Er) thin films, synthesized via thermal chemical vapor deposition, was investigated for carbon and oxygen concentrations in the range of 0–1.63. Intense room-temperature PL was observed at 1540 nm, with the PL intensity being dependent on the carbon and oxygen content. The strongest PL intensity was detected for a-SiC0.53O0.99:Er when pumped at 496.5 nm, with ∼ 20 times intensity enhancement as compared to a-SiO2:Er. Broadband excitation in the visible was observed for a-SiC0.53O0.99:Er. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses suggest that the formation of Si–C–O networks plays an important role in enhancing the Er optical activity in a-SiCxOy:Er films.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
78.66.Nk Insulators
78.55.Qr Amorphous materials; glasses and other disordered solids
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
79.60.Dp Adsorbed layers and thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth

Plasma hydrogenation of strained Si/SiGe/Si heterostructure for layer transfer without ion implantation

Lin Shao, Yuan Lin, J. K. Lee, Q. X. Jia, Yongqiang Wang, M. Nastasi, Phillip E. Thompson, N. David Theodore, Paul K. Chu, T. L. Alford, J. W. Mayer, Peng Chen, and S. S. Lau

Appl. Phys. Lett. 87, 091902 (2005); http://dx.doi.org/10.1063/1.2032602 (3 pages) | Cited 18 times

Online Publication Date: 22 August 2005

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We have developed an innovative approach without the use of ion implantation to transfer a high-quality thin Si layer for the fabrication of silicon-on-insulator wafers. The technique uses a buried strained SiGe layer, a few nanometers in thickness, to provide H trapping centers. In conjunction with H plasma hydrogenation, lift-off of the top Si layer can be realized with cleavage occurring at the depth of the strained SiGe layer. This technique avoids irradiation damage within the top Si layer that typically results from ion implantation used to create H trapping regions in the conventional ion-cut method. We explain the strain-facilitated layer transfer as being due to preferential vacancy aggregation within the strained layer and subsequent trapping of hydrogen, which lead to cracking in a well controlled manner.
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81.05.Cy Elemental semiconductors
81.65.-b Surface treatments
61.72.uf Ge and Si
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.J- Point defects and defect clusters
52.77.-j Plasma applications
68.35.Ct Interface structure and roughness

Growth of high-quality ZnMgO epilayers and ZnO/ZnMgO quantum well structures by radical-source molecular-beam epitaxy on sapphire

S. Sadofev, S. Blumstengel, J. Cui, J. Puls, S. Rogaschewski, P. Schäfer, Yu. G. Sadofyev, and F. Henneberger

Appl. Phys. Lett. 87, 091903 (2005); http://dx.doi.org/10.1063/1.2034113 (3 pages) | Cited 51 times

Online Publication Date: 22 August 2005

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We report on a specific growth procedure combining low-temperature growth of ZnMgO and postgrowth annealing at intermediate temperatures. Despite the large lattice misfit induced by the sapphire substrate, layer-by-layer growth is accomplished up to the phase-separation limit found at a c-lattice constant of 0.5136 nm and Mg mole fraction of 0.40. The procedure allows us to grow quantum wells with atomically smooth interfaces in a wide range of structural designs exhibiting prominent emission features up to room temperature.
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81.05.Dz II-VI semiconductors
81.07.St Quantum wells
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Hf II-VI semiconductors
78.67.De Quantum wells
61.72.Cc Kinetics of defect formation and annealing
61.66.Fn Inorganic compounds
64.75.-g Phase equilibria

Ultrahigh strength and high ductility of bulk nanocrystalline copper

Khaled M. Youssef, Ronald O. Scattergood, K. Linga Murty, Joseph A. Horton, and Carl. C. Koch

Appl. Phys. Lett. 87, 091904 (2005); http://dx.doi.org/10.1063/1.2034122 (3 pages) | Cited 115 times

Online Publication Date: 22 August 2005

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We have synthesized artifact-free bulk nanocrystalline copper samples with a narrow grain size distribution (mean grain size of 23 nm) that exhibited tensile yield strength about 11 times higher than that of conventional coarse-grained copper, while retaining a 14% uniform tensile elongation. In situ dynamic straining transmission electron microscope observations of the nanocrystalline copper are also reported, which showed individual dislocation motion and dislocation pile-ups. This suggests a dislocation-controlled deformation mechanism that allows for the high strain hardening observed. Trapped dislocations are observed in the individual nanograins.
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81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.46.-w Structure of nanoscale materials

Intersubband transitions in proton irradiated InGaAs/GaAs multiple quantum dots

Ying Chao Chua, E. A. Decuir, M. O. Manasreh, and B. D. Weaver

Appl. Phys. Lett. 87, 091905 (2005); http://dx.doi.org/10.1063/1.2035877 (3 pages) | Cited 1 time

Online Publication Date: 24 August 2005

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The optical absorbance spectra of the intersubband transition in 3 MeV proton irradiated In0.3Ga0.7As/GaAs multiple quantum dot samples, cut from the same wafer, were investigated as a function of irradiation dose. The intensity of the intersubband transition is observed to decrease as the irradiation dose is increased. The behavior of the intersubband transition in irradiated In0.3Ga0.7As/GaAs multiple quantum dot samples is compared to those of intersubband transitions in irradiated GaAs/AlGaAs and InGaAs/InAlAs multiple quantum well samples. The intersubband transition absorbance spectrum was completely depleted in a multiple quantum dot sample irradiated with 5×1014 cm−2. Post-irradiation thermal annealing was performed on the latter sample where thermal annealing recovery of the depleted intersubband transition was not observed. Instead, a broadband with a peak at 5 μm is observed after annealing the sample at 500 °C for 15 min. The absence of the broadband in an unirradiated sample that was subject to the same annealing conditions suggests that this band may be related to irradiation-induced defects.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
78.67.De Quantum wells
78.30.Fs III-V and II-VI semiconductors

Super-elastic titanium alloy with unstable plastic deformation

Y. L. Hao, S. J. Li, S. Y. Sun, C. Y. Zheng, Q. M. Hu, and R. Yang

Appl. Phys. Lett. 87, 091906 (2005); http://dx.doi.org/10.1063/1.2037192 (3 pages) | Cited 51 times

Online Publication Date: 24 August 2005

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Here we report a non-toxic β-type titanium alloy exhibiting unstable elastic and plastic deformation behavior. Elastic instability leads to remarkable elastic softening, i.e., the decrease of incipient Young’s modulus with slight pre-straining. In spite of partial recovery during room-temperature aging, a stable modulus of 33 GPa matching that of human bone can be maintained. Plastic instability causes highly-localized deformation which is very effective in grain refinement but contributes little to strength. We thus obtain soft nanostructured metallic materials (NMMs): The flow stress increases by only ∼ 5.5% as coarse grains are reduced to below 50 nm, in contrast with several times increase for previously-reported NMMs.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity
62.20.F- Deformation and plasticity

Subwavelength imaging by a flat cylindrical lens using optimized negative refraction

Zhaolin Lu, Caihua Chen, Christopher A. Schuetz, Shouyuan Shi, Janusz A. Murakowski, Garrett J. Schneider, and Dennis W. Prather

Appl. Phys. Lett. 87, 091907 (2005); http://dx.doi.org/10.1063/1.2035317 (3 pages) | Cited 11 times

Online Publication Date: 25 August 2005

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We experimentally demonstrate subwavelength imaging by a “flat cylindrical” lens using negative refraction. A two-dimensional photonic crystal whose dispersion at the second band provides group velocity opposite to the phase velocity for electromagnetic waves is employed to realize the flat lens, and the working frequency is chosen so that the effective refractive index is approximately equal to −1.0. Experiment demonstrated the imaging of a point source in both amplitude and phase in the millimeter-wave regime. By measuring the field distributions in the object plane and image plane, we observed amplification of evanescent waves and subwavelength size image. The image of two incoherent sources with subwavelength distance showed two resolvable spots, which served to further verify subwavelength resolution.
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42.79.Bh Lenses, prisms and mirrors
42.70.Qs Photonic bandgap materials
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