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8 Apr 2002

Volume 80, Issue 14, pp. 2433-2611

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Short-wavelength (λ<2 μm) intersubband absorption dynamics in ZnSe/BeTe quantum wells

R. Akimoto, K. Akita, F. Sasaki, and S. Kobayashi

Appl. Phys. Lett. 80, 2433 (2002); http://dx.doi.org/10.1063/1.1468261 (3 pages) | Cited 14 times

Online Publication Date: 2 April 2002

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We report on linear and nonlinear short-wavelength (λ<2 μm) intersubband (ISB) absorption characteristics in ZnSe/BeTe quantum wells by means of an interband pump and ISB pump/probe technique. The ISB absorption saturates with a hole burning effect, indicating the absorption band is broadened inhomogeneously. The saturation intensity is as low as 4.3 MW/cm2 at λ = 1.76 μm. The direct ISB energy relaxation time increases gradually from 0.20 to 0.38 ps with decreasing λ from 2.2 to 1.8 μm, while the saturation recovery is replaced by another slow relaxation process with a time constant of a few ps. The Γ(ZnSe)–X(BeTe) electron transfer is a relevant mechanism for this slow relaxation. © 2002 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
78.47.-p Spectroscopy of solid state dynamics
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.40.Fy Semiconductors
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift

Improved efficiency of light-emitting diodes based on polyfluorene blends upon insertion of a poly(p-phenylene vinylene) electron- confinement layer

J. Morgado, R. H. Friend, and F. Cacialli

Appl. Phys. Lett. 80, 2436 (2002); http://dx.doi.org/10.1063/1.1467981 (3 pages) | Cited 51 times

Online Publication Date: 2 April 2002

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We report the improvement of the electroluminescence efficiency of light-emitting diodes (LEDs) based on polyfluorene blends, upon insertion of a thin film of poly(p-phenylene vinylene), PPV, between a hole-injection layer of poly(3,4-ethylene dioxythiophene), doped with polystyrene sulfonic acid, and the polyfluorenes emissive layer. For LEDs using a blend of poly(9,9′-dioctylfluorene), with 5 wt % of the green emitter poly(9,9′-dioctylfluorene-altbenzothiadiazole), and calcium cathodes, the efficiency increases from 2.1 to 4.1 cd/A upon insertion of such a PPV layer. We propose that such an improvement is mainly due to the electron-blocking effect of the PPV layer, leading to improved charge carriers balance within the emissive layer. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence

Optical recording using smectic layer rotation in ferroelectric liquid crystal

Keizo Nakayama, Junji Ohtsubo, Masanori Ozaki, and Katsumi Yoshino

Appl. Phys. Lett. 80, 2439 (2002); http://dx.doi.org/10.1063/1.1467972 (3 pages)

Online Publication Date: 2 April 2002

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Optical recording in a ferroelectric liquid crystal using smectic layer rotation induced by the application of asymmetric voltage pulses has been proposed. This recording method is based on the temperature dependence of the rotation rate and the fact that the rate in the smectic A (SmA) phase is considerably smaller than that in the chiral smectic C (SmC∗) phase. The transition from the SmC∗ to the SmA phase can be induced by the photothermal effect. The application of asymmetric voltage pulses during partial laser irradiation results in the patterning of the layer alignment. This recording method can erase and invert the stored pattern and can handle gray-level patterns. © 2002 American Institute of Physics.
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42.79.Vb Optical storage systems, optical disks
42.70.Df Liquid crystals
42.70.Ln Holographic recording materials; optical storage media
78.20.Jq Electro-optical effects
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
64.70.M- Transitions in liquid crystals
85.50.Gk Non-volatile ferroelectric memories

Optical thin films consisting of nanoscale laminated layers

Shin-ichi Zaitsu, Takahisa Jitsuno, Masahiro Nakatsuka, Tatsuhiko Yamanaka, and Shinji Motokoshi

Appl. Phys. Lett. 80, 2442 (2002); http://dx.doi.org/10.1063/1.1467622 (3 pages) | Cited 14 times

Online Publication Date: 2 April 2002

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The control of the refractive index of laminated coatings consisting of alternating stacks of nanoscale Al2O3 and TiO2 sublayers grown by atomic layer deposition has been achieved. The refractive index of the coating linearly changed from 1.870 to 2.318 as the thickness of the single TiO2 sublayer was varied from 2.0 to 39 Å while that of the single Al2O3 sublayer was kept constant at 5.5 Å. The refractive index could be varied by adjusting only the number of growth cycles of each material. This approach will have potential applications to optical multilayer coatings consisting of well-controlled extremely thin layers. © 2002 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.65.Ac Multilayers
42.79.Wc Optical coatings
78.66.-w Optical properties of specific thin films
42.79.Ci Filters, zone plates, and polarizers

Low threshold 1.2 μm InGaAs quantum well lasers grown under low As/III ratio

T. Takeuchi, Y.-L. Chang, A. Tandon, D. Bour, S. Corzine, R. Twist, M. Tan, and H.-C. Luan

Appl. Phys. Lett. 80, 2445 (2002); http://dx.doi.org/10.1063/1.1467697 (3 pages) | Cited 18 times

Online Publication Date: 2 April 2002

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We have achieved 160 A/cm2 threshold current density of a 1.21 μm InGaAs/GaAs quantum well (QW) laser grown under a very low As/III ratio. We investigated the As/III ratio dependence on the optical quality of InGaAs QWs grown with arsine and tertiarybutylarsine (TBA). We found that TBA allows us to grow high quality InGaAs QWs under a very low As/III ratio (∼3), while a higher As/III ratio (∼10) with arsine is necessary to obtain the similar quality QWs. This high quality InGaAs QW grown under the low As/III ratio leads to the realization of high quality InGaAsN QW which should be grown under a low As/III ratio and a high N/V ratio. © 2002 American Institute of Physics.
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42.60.By Design of specific laser systems
81.07.St Quantum wells
42.55.Px Semiconductor lasers; laser diodes
78.67.De Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Quaternary GaInAsN with high In content: Dependence of band gap energy on N content

D. Serries, T. Geppert, P. Ganser, M. Maier, K. Köhler, N. Herres, and J. Wagner

Appl. Phys. Lett. 80, 2448 (2002); http://dx.doi.org/10.1063/1.1467612 (3 pages) | Cited 14 times

Online Publication Date: 2 April 2002

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Quaternary pseudomorphically strained GaInAsN films and double-quantum wells were grown by plasma assisted molecular-beam epitaxy on an InP substrate. The In content ranged from 53% to 70% while the N content was varied between 0% and 2.4%. A reduction of compressive strain and a low-energy shift of photoluminescence (PL) peak position was observed with increasing N concentration, accompanied by a reduction in PL peak intensity and increase in linewidth. The net effect of N incorporation on the GaInAsN band gap energy was calculated from the measured PL peak energies. The thus obtained composition dependent GaInAsN band gap energy was fitted using the band anticrossing model, yielding values for the interaction parameter CMN for high In-containing GaInAsN being only slightly smaller than that reported for low In-content GaInAsN on GaAs. © 2002 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors
71.20.Nr Semiconductor compounds

Theoretical investigation of laser gain in AlGaInN quaternary quantum wells

W. W. Chow, H. C. Schneider, A. J. Fischer, and A. A. Allerman

Appl. Phys. Lett. 80, 2451 (2002); http://dx.doi.org/10.1063/1.1465523 (3 pages) | Cited 4 times

Online Publication Date: 2 April 2002

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Microscopic calculations of laser gain spectra are presented for AlGaInN wurtzite quantum-well structures that are under compressive, zero and tensile strain. It is found that the optical nonlinearities induced by the combination of strain, quantum-confined Stark effect and many-body Coulomb interactions give rise to optical behavior that can differ significantly from that in conventional semiconductor lasers. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.67.De Quantum wells
42.65.-k Nonlinear optics
68.65.Fg Quantum wells
78.20.Jq Electro-optical effects
62.20.-x Mechanical properties of solids

Dual-frequency quantum-cascade terahertz emitter

V. M. Menon, W. D. Goodhue, A. S. Karakashian, A. Naweed, J. Plant, L. R. Ram-Mohan, A. Gatesman, V. Badami, and J. Waldman

Appl. Phys. Lett. 80, 2454 (2002); http://dx.doi.org/10.1063/1.1467698 (3 pages) | Cited 4 times

Online Publication Date: 2 April 2002

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We report the realization of a GaAs/AlGaAs quantum-cascade terahertz emitter capable of emitting at two entirely different frequencies from the same structure. This is realized through judicious wavefunction engineering of the relevant electronic states. Emission is observed at 6.32 meV (1.5 THz) and 12.18 meV (2.9 THz) with full width at half maximum of 0.72 meV and 0.58 meV, respectively, at T = 10 K. The structure consisted of 40 periods of the quantum-cascade module. Emission occurred between two sets of distinct energy levels that came into the desired configuration at different biases due to the quantum-confined Stark effect. Higher-energy AlAs-like phonons were utilized for the depopulation mechanism. © 2002 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
78.67.De Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.20.Jq Electro-optical effects
78.60.Fi Electroluminescence
73.21.Fg Quantum wells
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