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18 Jun 2001

Volume 78, Issue 25, pp. 3927-4046

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Milliwatt operation of AlGaN-based single-quantum-well light emitting diode in the ultraviolet region

Toshio Nishida, Hisao Saito, and Naoki Kobayashi

Appl. Phys. Lett. 78, 3927 (2001); http://dx.doi.org/10.1063/1.1377854 (2 pages)

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By introducing a single-quantum-well active layer and a high-Al-content carrier blocking layer, the output power of an AlGaN-based ultraviolet light-emitting diode has been improved by one order of magnitude. Optical output of 1 mW was achieved at the emission peak wavelength of 341–343 nm. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.72.Bj Visible and ultraviolet sources
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells
78.60.Fi Electroluminescence

Femtosecond switching with semiconductor-optical-amplifier-based Symmetric Mach–Zehnder-type all-optical switch

Shigeru Nakamura, Yoshiyasu Ueno, and Kazuhito Tajima

Appl. Phys. Lett. 78, 3929 (2001); http://dx.doi.org/10.1063/1.1379790 (3 pages) | Cited 18 times

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We investigate the effect of intraband carrier dynamics on a nonlinear phase shift induced in a semiconductor optical amplifier (SOA) in terms of its applicability to the Symmetric Mach–Zehnder (SMZ) all-optical switch. Nonlinear phase shifts in an SOA and a passive semiconductor waveguide are compared under control-pulse durations ranging from 3.2 to 0.4 ps. The results show that femtosecond switching with higher efficiency is still possible by using the SOA. We experimentally achieve femtosecond (670 fs), femtojoule (140 fJ) switching with the SOA-based SMZ all-optical switch. © 2001 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
07.60.Ly Interferometers
42.65.Wi Nonlinear waveguides

Cavity-quantum electrodynamics using a single InAs quantum dot in a microdisk structure

A. Kiraz, P. Michler, C. Becher, B. Gayral, A. Imamoğlu, Lidong Zhang, E. Hu, W. V. Schoenfeld, and P. M. Petroff

Appl. Phys. Lett. 78, 3932 (2001); http://dx.doi.org/10.1063/1.1379987 (3 pages) | Cited 80 times

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We investigate cavity-quantum electrodynamics (QED) effects in an all-semiconductor nanostructure by tuning a single self-assembled InAs quantum dot (QD) into resonance with a high quality factor microdisk whispering gallery mode (WGM). The stronger temperature dependence of the QD single-exciton (1X) resonance allows us to change the relative energy of the WGM and the 1X transitions by varying the sample temperature. The two coupled resonances exhibit crossing behavior due to the weak coupling cavity-QED regime. We demonstrate exciton lifetime reduction by 6 due to the Purcell effect by tuning the QD into resonance with the WGM. Our experiments also show that single-exciton lifetime is independent of temperature up to 50 K. © 2001 American Institute of Physics.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
73.21.La Quantum dots

Room-temperature operation of photopumped monolithic InP vertical-cavity laser with two air-gap Bragg reflectors

N. Chitica and M. Strassner

Appl. Phys. Lett. 78, 3935 (2001); http://dx.doi.org/10.1063/1.1379983 (3 pages) | Cited 5 times

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We demonstrate a long wavelength (λ = 1.56 μm) vertical-cavity laser built on a low-loss resonator formed by two InP/air-gap Bragg reflectors. The monolithic, InP-based structure uses a periodic gain active region with six strain-compensated quantum wells. The photopumped vertical-cavity laser requires record low power density of only 370 W/cm2 to reach threshold at 25 °C. The equivalent threshold current density is estimated to be as low as 400 A/cm2. Continuous-wave operation is demonstrated up to 32 °C despite the low heat conductivity of the reflectors. The emission is single mode and a power of up to 110 μW has been coupled into a single-mode fiber. © 2001 American Institute of Physics.
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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.Pk Continuous operation
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Chirp reduction in semiconductor lasers through injection current patterning

N. Dokhane and G. L. Lippi

Appl. Phys. Lett. 78, 3938 (2001); http://dx.doi.org/10.1063/1.1379060 (3 pages) | Cited 4 times

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The introduction of patterned current fronts that modulate the transition between directly modulated optical bits allows for a strong reduction of the optical chirp in a single-mode semiconductor laser, as shown in the numerical integration of a standard model. Hence, optical transmission of information over much longer distances without signal deterioration and a substantial increase in data transmission speed are possible. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Large-signal coherent control of normal modes in quantum-well semiconductor microcavity

Y.-S. Lee, T. B. Norris, A. Maslov, D. S. Citrin, J. Prineas, G. Khitrova, and H. M. Gibbs

Appl. Phys. Lett. 78, 3941 (2001); http://dx.doi.org/10.1063/1.1378316 (3 pages) | Cited 7 times

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We demonstrate coherent control of the cavity-polariton modes of a quantum-well semiconductor microcavity in a two-color scheme. The cavity enhancement of the excitonic nonlinearity gives rise to a large signal; modulating the relative phase of the excitation pulses between zero and π produces a differential reflectivity (ΔR/R) of up to 20%. The maximum nonlinear signal is obtained for cocircular pump and probe polarization. Excitation-induced dephasing is responsible for the incoherent nonlinear response, and limits the contrast ratio of the optical switching. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.67.De Quantum wells
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.Fg Quantum wells
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
71.35.-y Excitons and related phenomena
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.55.Sa Microcavity and microdisk lasers

High diffraction efficiency polarization gratings recorded by biphotonic holography in an azobenzene liquid crystalline polyester

C. Sánchez, R. Alcalá, S. Hvilsted, and P. S. Ramanujam

Appl. Phys. Lett. 78, 3944 (2001); http://dx.doi.org/10.1063/1.1379791 (3 pages) | Cited 14 times

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High diffraction efficiencies have been achieved with polarization gratings recorded in thin films of an azobenzene side-chain liquid crystalline polyester by means of biphotonic processes. Efficiency values up to 30% have been reached after an induction period of 300 s and subsequent evolution with the sample in darkness. These values are at least two orders of magnitude higher than those previously reported for biphotonic recording. The gratings can be erased with unpolarized blue light and partial recovery of the diffraction efficiency has been observed after the erasure process when the sample is kept in darkness. Red light illumination of the erased film increases the recovered efficiency value and the recovery rate. © 2001 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
42.79.Dj Gratings
42.79.Kr Display devices, liquid-crystal devices

White light emission from exciplex using tris-(8-hydroxyquinoline)aluminum as chromaticity-tuning layer

Jing Feng, Feng Li, Wenbao Gao, Shiyong Liu, Yu Liu, and Yue Wang

Appl. Phys. Lett. 78, 3947 (2001); http://dx.doi.org/10.1063/1.1379788 (3 pages) | Cited 46 times

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We demonstrate efficient organic white light-emitting devices (LEDs), using N,N′-diphenyl-N,N′-bis(1-naphthyl)–(1,1′-biphenyl)-4,4′-diamine (NPB) as the hole-transporting layer, 1,6-bis(2-hydroxyphenyl)pyridine boron complex [(dppy)BF)] as the emitting layer, tris-(8-hydroxyquinoline)aluminum (Alq) as the electron-transporting and chromaticity-tuning layer. The white light comes from exciplex emission at the solid-state interface between (dppy)BF and NPB in addition to the exciton emission from NPB and (dppy)BF, respectively. The chromaticity of white emission can be tuned by adjusting the thickness of the Alq layer. The white LEDs with an Alq thickness of 15 nm exhibit a maximum luminescence of 2000 cd/m2 and efficiency of 0.58 lm/W, and the Commission Internationale De l’Eclairage coordinates of resulting emission vary from (0.29,0.33) to (0.31,0.35) with increasing forward bias from 10 to 25 V. The region is very close to the equienergy white point (0.33,0.33). © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence
78.55.Kz Solid organic materials

Injectorless quantum-cascade lasers

Michael C. Wanke, Federico Capasso, Claire Gmachl, Alessandro Tredicucci, Deborah L. Sivco, Albert L. Hutchinson, S.-N. George Chu, and Alfred Y. Cho

Appl. Phys. Lett. 78, 3950 (2001); http://dx.doi.org/10.1063/1.1378805 (3 pages) | Cited 25 times

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An “injectorless” quantum-cascade (QC) laser is presented. The requirement of using injector regions to transport electrons from the lower laser level and other low-lying energy levels of one active region to the upper laser level of the next electron-downstream active region was eliminated by using an appropriately designed double-quantum-well “chirped” superlattice active region. The major advantage of the “injectorless” QC laser is the close packing of the active regions and the concomitant large optical confinement factor. Using a cascade of 75 consecutive active regions, designed for emission at λ = 11.5 μm, a pulsed peak output power of 270 mW is achieved at 7 K and approximately 10 mW at the maximum operating temperature of 195 K. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Z-scan study on the nonlinear refractive index of copper nanocluster composite silica glass

G. Battaglin, P. Calvelli, E. Cattaruzza, F. Gonella, R. Polloni, G. Mattei, and P. Mazzoldi

Appl. Phys. Lett. 78, 3953 (2001); http://dx.doi.org/10.1063/1.1380243 (3 pages) | Cited 31 times

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We used the Z-scan technique for measuring the nonlinear refractive index n2 of a thin composite film formed by copper nanoparticles embedded in silica glass. By varying the number of pulses of the laser shot, we evidenced heating effects induced by the laser during measurements. We were able to estimate the nonthermal refractive-index value, n2 = (3.0±0.3)×10−12 cm2/W. © 2001 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.66.Sq Composite materials
81.07.Bc Nanocrystalline materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
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