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26 Nov 2007

Volume 91, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 222101 (2007); http://dx.doi.org/10.1063/1.2815931 (3 pages)

H. T. Wang, B. S. Kang, F. Ren, S. J. Pearton, J. W. Johnson, P. Rajagopal, J. C. Roberts, E. L. Piner, and K. J. Linthicum
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1.58 μm InGaAs quantum well laser on GaAs

I. Tångring, H. Q. Ni, B. P. Wu, D. H. Wu, Y. H. Xiong, S. S. Huang, Z. C. Niu, S. M. Wang, Z. H. Lai, and A. Larsson

Appl. Phys. Lett. 91, 221101 (2007); http://dx.doi.org/10.1063/1.2803756 (3 pages) | Cited 15 times

Online Publication Date: 26 November 2007

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We demonstrate the 1.58 μm emission at room temperature from a metamorphic In0.6Ga0.4As quantum well laser grown on GaAs by molecular beam epitaxy. The large lattice mismatch was accommodated through growth of a linearly graded buffer layer to create a high quality virtual In0.32Ga0.68As substrate. Careful growth optimization ensured good optical and structural qualities. For a 1250×50 μm2 broad area laser, a minimum threshold current density of 490 A/cm2 was achieved under pulsed operation. This result indicates that metamorphic InGaAs quantum wells can be an alternative approach for 1.55 μm GaAs-based lasers.
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42.55.Px Semiconductor lasers; laser diodes
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Highly efficient and compact photonic wire splitters on GaAs

Ch. Schuller, S. Höfling, A. Forchel, C. Etrich, T. Pertsch, R. Iliew, F. Lederer, and J. P. Reithmaier

Appl. Phys. Lett. 91, 221102 (2007); http://dx.doi.org/10.1063/1.2814042 (3 pages) | Cited 3 times

Online Publication Date: 26 November 2007

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Symmetrical optical power T-splitters were fabricated using miniaturized 90° bends with a curvature radius of 2 μm and a high transmittance of almost 99% per bend. A constant excess loss of only 1.4 dB was achieved at a photonic wire width of 450 nm over the wide wavelength range from 1.50 to 1.58 μm. The dependence of the transmittance on the width of the photonic wires of the T-splitter was investigated experimentally and theoretically, and good agreement between experiments and three-dimensional finite-difference time-domain simulations was obtained.
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42.79.Fm Reflectors, beam splitters, and deflectors
42.82.Cr Fabrication techniques; lithography, pattern transfer

Nitride based laser diodes on substrates with patterned AlN mask

Marcin Sarzyński, Marcin Kryśko, Grzegorz Targowski, Grzegorz Kamler, Jarosław Domagała, Robert Czernecki, Adam Libura, Piotr Perlin, and Michał Leszczyński

Appl. Phys. Lett. 91, 221103 (2007); http://dx.doi.org/10.1063/1.2817594 (3 pages) | Cited 1 time

Online Publication Date: 26 November 2007

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We report on electrical and optical properties of InGaN violet laser diodes, grown on high-pressure grown, almost dislocation free GaN substrates. In these structures, mechanical strain has been reduced by a partially relaxed AlN mask with stripe shaped windows. The dislocation density of the mask was 1010/cm2. In the window areas, where we located the laser stripes, the dislocation density was below 3×106/cm2. We fabricated three types of laser diodes with aluminum composition in the cladding of 8%, 13%, and 16%. All devices remained crack-free. The laser threshold current decreased with increasing Al composition in the cladding.
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42.55.Px Semiconductor lasers; laser diodes
42.82.Cr Fabrication techniques; lithography, pattern transfer
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Omnidirectional photonic band gap in polymer photonic crystal slabs

Jan Hendrik Wülbern, Markus Schmidt, Manfred Eich, Uwe Hübner, Richard Boucher, F. Marlow, and W. Volksen

Appl. Phys. Lett. 91, 221104 (2007); http://dx.doi.org/10.1063/1.2817331 (3 pages) | Cited 5 times

Online Publication Date: 26 November 2007

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In this letter, we report on the experimental observation of a complete in-plane photonic band gap for transverse-electric-like polarized modes in a polymer photonic crystal slab with a triangular array of holes. We performed transmission measurements on two-dimensional photonic crystal slabs in both principal directions of the triangular lattice. For a propagation distance of 40 lattice constants, the transmission was effectively suppressed regardless of propagation direction below −15 dB over a bandwidth of 65 nm. The experimental results are in excellent agreement with theoretical predictions obtained from band diagram calculations and finite integration time domain techniques.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Light focusing via Rowland concave surface of photonic crystal

E. H. Khoo, A. Q. Liu, T. H. Cheng, J. Li, and D. Pinjala

Appl. Phys. Lett. 91, 221105 (2007); http://dx.doi.org/10.1063/1.2815914 (3 pages) | Cited 5 times

Online Publication Date: 27 November 2007

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This letter investigates the focusing characteristics of lightwaves emitted from photonic crystal waveguide aperture using a concave corrugated surface. Based on Rowland’s theory, the concave structure is applied to the photonic crystal output surface. The field distribution pattern of the emitted lightwaves demonstrates the focusing effect. The focusing distance agrees with Rowland’s theory. By optimizing the surface structures, the focused beam has a full wave at half maximum width of 1.6a. This suggests that the concave corrugated surface could substitute conventional optical lens for focusing and coupling subwavelength devices. Similarly, by inverting the surface structures, the lightwaves splits at the same focusing location.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
42.79.Bh Lenses, prisms and mirrors

ZnO nanoparticle size-dependent excitation of surface Raman signal from adsorbed molecules: Observation of a charge-transfer resonance

Zhihua Sun, Bing Zhao, and John R. Lombardi

Appl. Phys. Lett. 91, 221106 (2007); http://dx.doi.org/10.1063/1.2817529 (3 pages) | Cited 9 times

Online Publication Date: 28 November 2007

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By observing the Raman intensity of several molecules (4-mercaptopyridine and 4-mercaptobenzoic acid) adsorbed on the surface of ZnO nanocrystals as a function of particle size in the range of 18–31 nm diameter, we show that a large increase in intensity is observed near 28 nm. This is an indication of a size-dependent charge-transfer resonance. We interpret this effect as due to formation of a charge-transfer complex between a surface-bound exciton and the adsorbed molecule.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.30.Jw Organic compounds, polymers
68.43.Mn Adsorption kinetics
71.70.-d Level splitting and interactions
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.47.Fg Semiconductor surfaces

Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using SiO2/polystyrene microlens arrays

Yik-Khoon Ee, Ronald A. Arif, Nelson Tansu, Pisist Kumnorkaew, and James F. Gilchrist

Appl. Phys. Lett. 91, 221107 (2007); http://dx.doi.org/10.1063/1.2816891 (3 pages) | Cited 34 times

Online Publication Date: 28 November 2007

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Improvement of light extraction efficiency of InGaN quantum wells light emitting diodes (LEDs) using SiO2/polystyrene microspheres was demonstrated experimentally. The utilization of SiO2/polystyrene microlens arrays on InGaN quantum wells LEDs, deposited via rapid convective deposition, allows the increase of the effective photon escape cone and reduction in the Fresnel reflection. Improvement of output power by 219% for InGaN quantum wells LEDs emitting at peak wavelength of 480 nm with SiO2/polystyrene microspheres microlens arrays was demonstrated.
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85.60.Jb Light-emitting devices

Controlling four-wave and six-wave mixing processes in multilevel atomic systems

Yanpeng Zhang, Utsab Khadka, Blake Anderson, and Min Xiao

Appl. Phys. Lett. 91, 221108 (2007); http://dx.doi.org/10.1063/1.2817744 (3 pages) | Cited 6 times

Online Publication Date: 29 November 2007

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We experimentally demonstrate that four-wave mixing (FWM) and six-wave mixing (SWM) processes can be selectively turned on and off in a close-cycled four-level atomic system. Under certain laser beam configuration, the FWM and SWM processes can be made to coexist with similar signal amplitudes and transmit through the same electromagnetically induced transparency window in such folded four-level atomic system. By introducing an additional pumping laser beam connecting to the fifth energy level, both FWM and SWM signals can be greatly enhanced.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Planar photonic crystals infiltrated with nanoparticle/polymer composites

Savaş Tay, Jayan Thomas, Babak Momeni, Murtaza Askari, Ali Adibi, Peter J. Hotchkiss, Simon C. Jones, Seth R. Marder, Robert A. Norwood, and N. Peyghambarian

Appl. Phys. Lett. 91, 221109 (2007); http://dx.doi.org/10.1063/1.2817964 (3 pages) | Cited 9 times

Online Publication Date: 29 November 2007

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Infiltration of planar two-dimensional silicon photonic crystals with nanocomposites using a simple yet effective melt processing technique is presented. The nanocomposites that were developed by evenly dispersing functionalized TiO2 nanoparticles into a photoconducting polymer were completely filled into photonic crystals with hole sizes ranging from 90 to 500 nm. The infiltrated devices show tuning of the photonic band gap that is controllable by the adjustment of the nanoparticle loading level. These results may be useful in the development of tunable photonic crystal based devices and hybrid light emitting diodes and solor cells.
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85.60.Jb Light-emitting devices

Second harmonic generation of 2.6 W green light with thermoelectrically oxidized undoped congruent lithium niobate crystals below 100 °C

Ingo Breunig, Matthias Falk, Bastian Knabe, Rosita Sowade, Karsten Buse, Payam Rabiei, and Dieter H. Jundt

Appl. Phys. Lett. 91, 221110 (2007); http://dx.doi.org/10.1063/1.2819076 (3 pages) | Cited 8 times

Online Publication Date: 29 November 2007

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We demonstrate that thermoelectric oxidization suppresses unwanted light-induced refractive index changes in undoped congruent periodically poled lithium niobate crystals used for single-pass continuous-wave frequency doubling of 1030 nm light. The maximum second harmonic output power shows a strong dependence on the phase matching temperature. For 90 °C, a total of 2.6 W green light is generated with an efficiency of 22% corresponding to a normalized conversion efficiency of 1.8%/W.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
72.20.Pa Thermoelectric and thermomagnetic effects

Low noise NbN hot electron bolometer mixer at 4.3 THz

P. Khosropanah, J. R. Gao, W. M. Laauwen, M. Hajenius, and T. M. Klapwijk

Appl. Phys. Lett. 91, 221111 (2007); http://dx.doi.org/10.1063/1.2819534 (3 pages) | Cited 21 times

Online Publication Date: 29 November 2007

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We have studied the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a spiral antenna at 4.3 THz. Using hot/cold blackbody loads and a beam splitter all in vacuum, we measured a double sideband receiver noise temperature of 1300 K at the optimum local oscillator (LO) power of 330 nW, which is about 12 times the quantum noise (hν/2kB). Our result indicates that there is no sign of degradation of the mixing process at the superterahertz frequencies. Moreover, a measurement method is introduced which allows us for an accurate determination of the sensitivity despite LO power fluctuations.
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84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
85.25.-j Superconducting devices

Modifications of the exciton lifetime and internal quantum efficiency for organic light-emitting devices with a weak/strong microcavity

Xue-Wen Chen, Wallace C. H. Choy, C. J. Liang, P. K. A. Wai, and Sailing He

Appl. Phys. Lett. 91, 221112 (2007); http://dx.doi.org/10.1063/1.2819610 (3 pages) | Cited 1 time

Online Publication Date: 29 November 2007

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A comprehensive analysis is given on the modifications of the exciton lifetime and internal quantum efficiency (ηint) for organic light-emitting devices (OLEDs). A linear relation is derived between the exciton lifetime and ηint, which is difficult to measure directly. The internal quantum efficiency can thus be estimated easily through the measurement of the exciton lifetime. The exciton lifetimes for OLEDs with weak or strong microcavity are studied experimentally and theoretically. The modification of the exciton lifetime is well explained through the microcavity effect and surface plasmon resonance. An excellent agreement between the experimental and theoretical results is achieved.
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85.60.Jb Light-emitting devices

A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer

Yoonseuk Choi, Hak-Rin Kim, Kwang-Ho Lee, Yong-Min Lee, and Jae-Hoon Kim

Appl. Phys. Lett. 91, 221113 (2007); http://dx.doi.org/10.1063/1.2813638 (3 pages) | Cited 11 times

Online Publication Date: 30 November 2007

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We propose a focal intensity tunable microlens array by using a birefringent liquid crystalline polymer for lensing action. Due to the difference of effective refractive indices, it acts as a positive or negative microlens with respect to the polarization state. As we control the incident polarization by adding a liquid crystal layer, the focal intensity can be tuned by an applied voltage. Twisted nematic and bistable ferroelectric liquid crystal modes were applied to demonstrate the possibility of various driving features such as a continuously tunable focal intensity or fast switching with memory effect.
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42.70.Df Liquid crystals
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.80.Fm Switching phenomena
42.79.Bh Lenses, prisms and mirrors
61.30.Vx Polymer liquid crystals
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Complex dynamics of femtosecond terawatt laser pulses in air

Bin Qiao, C. H. Lai, C. T. Zhou, X. T. He, and Xingang Wang

Appl. Phys. Lett. 91, 221114 (2007); http://dx.doi.org/10.1063/1.2819611 (3 pages)

Online Publication Date: 30 November 2007

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Complex dynamics of femtosecond terawatt laser pulses in air is investigated theoretically and numerically by considering both χ(5) susceptibility and multiphoton ionization. Our investigation shows that these two high-order nonlinearities, acting as a Hamiltonian perturbation, can destroy homoclinic orbit connection of phase trajectory and result in spatial chaos and complex pattern of laser wave field. Due to the chaotic behavior of laser field, laser filamentation appears when laser intensity increases close to the ionization threshold.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.An Optical susceptibility, hyperpolarizability
42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.68.Ay Propagation, transmission, attenuation, and radiative transfer

All-optical demultiplexing of 160–10 Gbit/s signals with Mach-Zehnder interferometric switch utilizing intersubband transition in InGaAs/AlAs/AlAsSb quantum well

R. Akimoto, T. Simoyama, H. Tsuchida, S. Namiki, C. G. Lim, M. Nagase, T. Mozume, T. Hasama, and H. Ishikawa

Appl. Phys. Lett. 91, 221115 (2007); http://dx.doi.org/10.1063/1.2820382 (3 pages) | Cited 26 times

Online Publication Date: 30 November 2007

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We have developed a Mach-Zehnder interferometric all-optical switch employing intersubband transition in an InGaAs/AlAs/AlAsSb-coupled double quantum well waveguide. The recently discovered cross-phase modulation phenomenon was utilized as the switching mechanism; the nonlinear index of refraction for transverse electric polarized light is induced by intersubband optical excitation using transverse magnetic pump light. We demonstrate the demultiplexing operation of 160 Gbit/s data signals to 10 Gbit/s using this switch. At the input control pulse energy of 8 pJ, the demultiplexed signals showed an extinction ratio better than 10 dB, and an error-free demultiplexing was achieved.
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68.65.Fg Quantum wells
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.65.Wi Nonlinear waveguides
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Gap length effect on electron energy distribution in capacitive radio frequency discharges

S. J. You, S. S. Kim, Jung-Hyung Kim, Dae-Jin Seong, Yong-Hyeon Shin, and H. Y. Chang

Appl. Phys. Lett. 91, 221501 (2007); http://dx.doi.org/10.1063/1.2805032 (3 pages) | Cited 6 times

Online Publication Date: 26 November 2007

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A study on the dependence of electron energy distribution function (EEDF) on discharge gap size in capacitive rf discharges was conducted. The evolution of the EEDF over a gap size range from 2.5 to 7 cm in 65 mTorr Ar discharges was investigated both experimentally and theoretically. The measured EEDFs exhibited typical bi-Maxwellian forms with low energy electron groups. A significant depletion in the low energy portion of the bi-Maxwellian was found with decreasing gap size. The results show that electron heating by bulk electric fields, which is the main heating process of the low-energy electrons, is greatly enhanced as the gap size decreases, resulting in the abrupt change of the EEDF. The calculated EEDFs based on nonlocal kinetic theory are in good agreement with the experiments.
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52.80.Pi High-frequency and RF discharges
52.25.Dg Plasma kinetic equations
52.50.Nr Plasma heating by DC fields; ohmic heating, arcs

Room-temperature atmospheric argon plasma jet sustained with submicrosecond high-voltage pulses

J. L. Walsh and M. G. Kong

Appl. Phys. Lett. 91, 221502 (2007); http://dx.doi.org/10.1063/1.2817965 (3 pages) | Cited 45 times

Online Publication Date: 27 November 2007

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In this letter, an experimental study is presented to characterize a room-temperature plasma jet in atmospheric argon generated with submicrosecond voltage pulses at 4 kHz. Distinct from sinusoidally produced argon discharges that are prone to thermal runaway instabilities, the pulsed atmospheric argon plasma jet is stable and cold with an electron density 3.9 times greater than that in a comparable sinusoidal jet. Its optical emission is also much stronger. Electrical measurement suggests that the discharge event is preceded with a prebreakdown phase and its plasma stability is facilitated by the short voltage pulses.
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52.75.-d Plasma devices
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Hc Glow; corona

Growth of the current modulation in an electron beam propagating through background plasma

Han S. Uhm

Appl. Phys. Lett. 91, 221503 (2007); http://dx.doi.org/10.1063/1.2817950 (3 pages)

Online Publication Date: 28 November 2007

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Amplitude oscillation of the current modulation in an electron beam propagating through background plasma is investigated. An analytical calculation of the beam current modulation indicates amplitude oscillation at the beginning of propagation due to the perturbed space-charge fluctuation of the beam. It was also found that the mode strength of the beam current modulation further downstream grows exponentially from half, a0/2, of the initial perturbation instead of its value of a0, in contrast with the conventional understanding of two-stream instability. The analytical results are in good agreement with earlier simulation data.
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52.40.Mj Particle beam interactions in plasmas
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

Observation of the transition from a Townsend discharge to a glow discharge in helium at atmospheric pressure

Haiyun Luo, Zhuo Liang, Bo Lv, Xinxin Wang, Zhicheng Guan, and Liming Wang

Appl. Phys. Lett. 91, 221504 (2007); http://dx.doi.org/10.1063/1.2819073 (3 pages) | Cited 20 times

Online Publication Date: 28 November 2007

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Dielectric barrier discharge in helium at atmospheric pressure was studied by taking fast images of the discharge during one current pulse using an intensified charge couple device. It was observed that there appears a weakly luminous layer close to the anode at the very beginning of the discharge, then the luminous area gradually expands into the entire gap as the anode layer moves toward the cathode, and finally a highly luminous layer forms close to the cathode at the time around the maximum of the current pulse. The evolution of the discharge pattern indicates a transition from Townsend discharge to glow discharge.
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52.80.Dy Low-field and Townsend discharges
52.80.Hc Glow; corona
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Noninvasive method to measure the ion flux in capacitive discharge

Min-Hyong Lee, Hyo-Chang Lee, and Chin-Wook Chung

Appl. Phys. Lett. 91, 221505 (2007); http://dx.doi.org/10.1063/1.2815923 (3 pages) | Cited 1 time

Online Publication Date: 29 November 2007

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A noninvasive method to measure the ion flux from the current flowing through the substrate (substrate current) in a capacitive discharge is proposed. The substrate current consists of a displacement current and a conduction current. In a high frequency capacitively coupled plasma, the displacement current is usually much higher than the conduction current. However, the displacement current becomes negligible at a moment that the second time derivative of the substrate current becomes zero (the first time derivative reaches its minimum), and from the measured substrate current at that time, the ion flux can be obtained. The measured ion flux from this method is compared with the flux measured by another diagnostic method.
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52.70.Ds Electric and magnetic measurements

Reduce the start current of Smith-Purcell backward wave oscillator by sidewall grating

D. Li, K. Imasaki, X. Gao, Z. Yang, and Gun-Sik Park

Appl. Phys. Lett. 91, 221506 (2007); http://dx.doi.org/10.1063/1.2819075 (2 pages) | Cited 15 times

Online Publication Date: 29 November 2007

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A sidewall grating for the Smith-Purcell device is proposed to enhance the coupling of the optical mode with the electron beam and, consequently, relax the stringent requirements to the electron beam. With the help of three-dimensional particle-in-cell simulations, it has been shown that, comparing with the general grating, the usage of a sidewall grating improves the growth rate and dramatically shortens the time for the device to reach saturation. It is also found that the sidewall grating holds the potential to reduce the start current for the operation of a Smith-Purcell backward wave oscillator.
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41.75.Fr Electron and positron beams
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Characteristics of direct current microhollow cathode discharges combined with dielectric barrier discharges as preionizer

Jun Watanabe, Akihisa Ogino, and Masaaki Nagatsu

Appl. Phys. Lett. 91, 221507 (2007); http://dx.doi.org/10.1063/1.2819533 (3 pages) | Cited 2 times

Online Publication Date: 29 November 2007

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Characteristics of direct current microhollow cathode discharges (MHCDs) combined with dielectric barrier discharge (DBD) electrodes as preionization source were studied experimentally and theoretically. The DBD preionization significantly reduced the sparking voltage (from 3.1–3.2 to 2.4–2.5 kV) and improved the spatial uniformity of the multihole MHCDs. Theoretical calculations using the finite element method indicate that the electrons generated by DBDs in the negative phase of the applied voltage could be accelerated into the MHCD electrodes and serve as the seeding electrons for initiating MHCDs. It was experimentally demonstrated that pulselike MHCDs were synchronously triggered by the preionized DBD current pulses.
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52.80.-s Electric discharges
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Metastable behavior of the UV luminescence in Mg-doped GaN layers grown on quasibulk GaN templates

G. Pozina, P. P. Paskov, J. P. Bergman, C. Hemmingsson, L. Hultman, B. Monemar, H. Amano, I. Akasaki, and A. Usui

Appl. Phys. Lett. 91, 221901 (2007); http://dx.doi.org/10.1063/1.2809407 (3 pages) | Cited 4 times

Online Publication Date: 26 November 2007

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Metastability of near band gap UV emissions in Mg-doped GaN layers grown by metal-organic vapor phase epitaxy on thick GaN templates grown by halide vapor phase epitaxy has been studied by cathodoluminescence (CL). The CL spectrum changes its initial shape within a few minutes under electron irradiation. The acceptor bound exciton line vanishes while the emissions related to the stacking faults (SFs) of different geometry rise significantly. The increase of the defect-related luminescence is likely caused by recombination enhanced SF formation under electron irradiation. The CL spectrum transformation is permanent at low temperatures; however, the metastable process is reversible if samples are heated to room temperature.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Cr III-V semiconductors
78.40.Fy Semiconductors
61.80.Fe Electron and positron radiation effects
61.72.Nn Stacking faults and other planar or extended defects

Determination of the third- and fifth-order nonlinear refractive indices in InN thin films

Z. Q. Zhang, W. Q. He, C. M. Gu, W. Z. Shen, H. Ogawa, and Q. X. Guo

Appl. Phys. Lett. 91, 221902 (2007); http://dx.doi.org/10.1063/1.2813637 (3 pages) | Cited 4 times

Online Publication Date: 26 November 2007

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We have combined the reflection and transmission Z-scan (RZ- and TZ-scans) techniques under femtosecond laser at 800 nm to extract both the third- and fifth-order nonlinear refractive indices (n2 and n4) in InN thin films. The observation of the nonlinear refractive index saturation in the intensity-dependent RZ-scan measurement indicates the existence of the fifth-order effect. By the aid of the TZ-scan, the fifth-order nonlinear effect has been enhanced by enlarging the cascaded contribution from the increased laser interaction length, where large n2 of −2.5×10−11 cm2/W and n4 of 2.1×10−19 cm4/W2 have been determined.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Fd III-V semiconductors
42.65.-k Nonlinear optics
42.79.Wc Optical coatings

Temperature dependence of optical band gap in ferroelectric Bi3.25La0.75Ti3O12 films determined by ultraviolet transmittance measurements

Z. G. Hu, Y. W. Li, F. Y. Yue, Z. Q. Zhu, and J. H. Chu

Appl. Phys. Lett. 91, 221903 (2007); http://dx.doi.org/10.1063/1.2816915 (3 pages) | Cited 12 times

Online Publication Date: 26 November 2007

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Optical properties of ferroelectric Bi3.25La0.75Ti3O12 (BLT) films on quartz have been investigated using ultraviolet-infrared transmittance spectra in the temperature range of 77–500 K. The spectra can be divided into three distinctive photon regions between 1.1 and 6.5 eV. It is found that the band gap Eg decreases from 3.88 to 3.77 eV with the temperature. The parameters aB and ΘB of the Bose-Einstein model are 30.3 meV and 218.7 K, respectively. The band narrowing coefficient dEg/dT is −2.65×10−4 eV/K at room temperature. The present results can be crucial for future application of ferroelectric BLT-based electro-optic and high temperature optoelectronic devices.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
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  3. Electronic transport in locally gated graphene nanoconstrictions
  4. A hydrogen sensor based on tunneling between palladium clusters
  5. RbCdF3:Mn2+: A potential ultraviolet dosimeter material
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