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21 Aug 2006

Volume 89, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 074103 (2006); http://dx.doi.org/10.1063/1.2337528 (2 pages)

J. M. Yi, J. H. Je, Y. S. Chu, Y. Zhong, Y. Hwu, and G. Margaritondo
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High-temperature continuous wave operation of strain-balanced quantum cascade lasers grown by metal organic vapor-phase epitaxy

L. Diehl, D. Bour, S. Corzine, J. Zhu, G. Höfler, M. Lončar, M. Troccoli, and Federico Capasso

Appl. Phys. Lett. 89, 081101 (2006); http://dx.doi.org/10.1063/1.2337284 (3 pages) | Cited 33 times

Online Publication Date: 21 August 2006

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The authors report the fabrication of high-power strained quantum cascade lasers working in continuous mode above 370 K. The devices, processed in narrow buried heterostructures, were grown by low-pressure metal organic vapor-phase epitaxy. Continuous wave output power as high as 312 mW at 300 K was obtained at a wavelength of 5.29 μm from a 3.25 mm long, 7.5 μm wide laser with a high-reflectivity back facet coating. The slope efficiency was in excess of 1.5 W/A and the power conversion efficiency reached almost 5%.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.79.Wc Optical coatings

Ultrafast gain and index dynamics of quantum dash structures emitting at 1.55 μm

M. van der Poel, J. Mørk, A. Somers, A. Forchel, J. P. Reithmaier, and G. Eisenstein

Appl. Phys. Lett. 89, 081102 (2006); http://dx.doi.org/10.1063/1.2337881 (3 pages) | Cited 18 times

Online Publication Date: 21 August 2006

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The authors systematically characterize the ultrafast gain and index recovery of a quantum dash semiconductor optical amplifier after it has amplified a strong femtosecond pulse. The results show a recovery dominated by a fast time constant of 1.4 ps with an ultimate recovery taking place on a 150 ps time scale. The results are distinctly different from the recovery of quantum dot amplifiers and reflect the special density of states of the quantum-wire-like dashes.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Giant oxidation related relief of Al-rich layers on cleaved mirrors of GaSb/Ga0.1Al0.9SbAs/GaInAsSb laser structures

P. A. Dementyev, M. S. Dunaevskii, A. V. Ankudinov, I. V. Makarenko, V. N. Petrov, A. N. Titkov, A. N. Baranov, D. A. Yarekha, and R. Laiho

Appl. Phys. Lett. 89, 081103 (2006); http://dx.doi.org/10.1063/1.2338002 (3 pages)

Online Publication Date: 21 August 2006

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Oxidation kinetics of Al-rich layers in ambient room conditions is investigated on cleaved mirrors of GaSb/Ga1−xAlxAsSb (x = 0.9–0.93) laser heterostructure. The measurements performed by atomic force microscopy demonstrate intensive growth of native oxide during the first two months with further saturation of the oxide thickness to about 1 μm. In studies of the oxide cross section using additional cleavages perpendicular to the laser mirror, the volume of the oxidized part of the Al-rich layer is found to expand through elevations on the heterostructure mirror so that the height of the elevations reaches one-third of the total thickness of the oxide.
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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

Efficient ultraviolet-blue polymer light-emitting diodes based on a fluorene-based non-conjugated polymer

Fei Huang, Yu-Hua Niu, Michelle S. Liu, Xing-Hua Zhou, Yan-Qing Tian, and Alex K.-Y. Jen

Appl. Phys. Lett. 89, 081104 (2006); http://dx.doi.org/10.1063/1.2336745 (3 pages) | Cited 12 times

Online Publication Date: 21 August 2006

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Efficient UV-blue polymer light-emitting diodes based on a fluorene-based nonconjugated polymer, poly[2,7-(9,9-dihexylfluorene)-alt-4,4′-phenylether] (PFPE), are fabricated. The device with PFPE as emitting layer shows a very narrow ultraviolet-blue electroluminescence emission with a peak at 397 nm and a maximal external quantum efficiency of 1.07%. By blending PFPE into poly(N-vinylcarbazole) (PVK), the device performance can be further improved. A maximum external quantum efficiency of 1.81%, with a maximum irradiance power density of 1223 μW/cm2, was reached by using a blend of PVK and PFPE in the weight ratio of 95:5 as emitting layer.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence

Monolithic microspectrometer using tunable ferroelectric liquid crystals

John W. McMurdy, Gregory P. Crawford, and Gregory D. Jay

Appl. Phys. Lett. 89, 081105 (2006); http://dx.doi.org/10.1063/1.2337868 (3 pages) | Cited 3 times

Online Publication Date: 22 August 2006

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A vertically aligned deformed helix ferroelectric liquid crystal is used to fabricate a thermally controllable monolithic microspectrometer using a single liquid crystal cell and a photodiode. The device has an active range over the entire visible spectrum from ∼ 400–720 nm achieving an optimal resolution of 12 nm in short wavelength regime to 20–25 nm in the long wavelength regime. Operation is demonstrated through spectral reconstruction of the mercury emission spectra and a broadband white light emitting diode using a commercial spectrometer and the liquid crystal based spectrometer.
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07.60.Rd Visible and ultraviolet spectrometers
42.70.Df Liquid crystals
42.72.Bj Visible and ultraviolet sources
85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Jb Light-emitting devices

Photocurrent response wavelength up to 1.1 μm from photovoltaic cells based on narrow-band-gap conjugated polymer and fullerene derivative

Yangjun Xia, Li Wang, Xianyu Deng, Dongyun Li, Xuhui Zhu, and Yong Cao

Appl. Phys. Lett. 89, 081106 (2006); http://dx.doi.org/10.1063/1.2338017 (3 pages) | Cited 25 times

Online Publication Date: 22 August 2006

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An extremely narrow-band-gap conjugated polymer poly(5,7-bis(4-decanyl-2-thienyl)thieno[3,4-b]diathiazole-thiophene-2,5) (PDDTT) (Eg ≈ 1.01 eV) was synthesized by Stille coupling reaction, which absorbs the light from 330–1220 nm in solid thin film and shows good solution processibility. The polymeric photovoltaic cells based on PDDTT/[6,6]-phenyl-C61-butyric acid methyl ester blend show the short circuit density of 0.83 mA/cm2, open current voltage of 0.35 V, and photocurrent spectra response from 330 to 1100 nm under AM 1.5 simulator (100 mW/cm2).
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85.60.Bt Optoelectronic device characterization, design, and modeling

 Wavelength-tunable and high-temperature lasing in ZnMgO nanoneedles

H. Y. Yang, S. P. Lau, S. F. Yu, M. Tanemura, T. Okita, H. Hatano, K. S. Teng, and S. P. Wilks

Appl. Phys. Lett. 89, 081107 (2006); http://dx.doi.org/10.1063/1.2338525 (3 pages) | Cited 11 times

Online Publication Date: 22 August 2006

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Zn1−xMgxO nanoneedles were prepared by an ion-beam technique on Zn1−xMgxO thin films with Mg contents of up to 21 at. %. The photoluminescence emission energies of the Zn1−xMgxO nanoneedles measured at room temperature increased monotonically with Mg contents and it reached 3.6 eV when x = 0.21. Random laser action was observed in the Zn1−xMgxO nanoneedles with x ⩽ 0.1 at temperature ranging from 300 to 470 K under 355 nm optical excitation. The characteristic temperature of the Zn1−xMgxO nanoneedles was determined to be 84 K. The high-temperature lasing of the Zn1−xMgxO nanoneedles are attributed to the high crystal quality of the nanoneedles, enhancement of oscillator strength in nanostructures, and a self-compensation mechanism in random laser cavities.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.55.Et II-VI semiconductors

Efficient frequency doubling in femtosecond laser-written waveguides in lithium niobate

Jonas Burghoff, Christian Grebing, Stefan Nolte, and Andreas Tünnermann

Appl. Phys. Lett. 89, 081108 (2006); http://dx.doi.org/10.1063/1.2338532 (3 pages) | Cited 38 times

Online Publication Date: 22 August 2006

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Optical waveguides in lithium niobate have been fabricated with a femtosecond laser. Different types of modifications depending on the laser parameters were observed and discussed. In these waveguides, frequency doubling of 1064 nm radiation was demonstrated utilizing birefringent phase matching. A conversion efficiency of 49% was obtained in a 9.3 mm long sample.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Gn Optical waveguides and couplers
42.62.-b Laser applications

Strong upconversion from Er3Al5O12 ceramic powders prepared by low temperature direct combustion synthesis

Glauco S. Maciel, Nikifor Rakov, Michael Fokine, Isabel C. S. Carvalho, and Carlos B. Pinheiro

Appl. Phys. Lett. 89, 081109 (2006); http://dx.doi.org/10.1063/1.2338558 (3 pages) | Cited 9 times

Online Publication Date: 22 August 2006

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Crystalline ceramic powders of Er3Al5O12 were obtained by low temperature direct combustion synthesis. Irradiating the sample with a low-power continuous-wave infrared (1.48 μm) diode laser led to ultraviolet, violet, blue, green, and red (380, 410, 456, 495, 525, 550, and 660 nm) emissions. The strong upconversion luminescence appeared to the eyes as an intense green color. The presence of efficient four- and three-photon frequency upconversion processes makes this material an excellent candidate for use in photonic devices based on upconverter phosphors.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
78.55.Hx Other solid inorganic materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
81.05.Cy Elemental semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

High color purity phosphors of LaAlGe2O7 doped with Tm3+ and Er3+

Yu-Chun Li, Yen-Hwei Chang, Yu-Feng Lin, Yi-Jing Lin, and Yee-Shin Chang

Appl. Phys. Lett. 89, 081110 (2006); http://dx.doi.org/10.1063/1.2337275 (3 pages) | Cited 19 times

Online Publication Date: 23 August 2006

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Phosphors of LaAlGe2O7 doped with Tm3+ and Er3+ of high color purity, exhibiting a narrow band emission in the blue and green regions, were obtained. (La1−xLnx)AlGe2O7 (Ln = Tm,Er) powders are bright emitters, with chromaticity color coordinates that are comparable to or better than those of standard phosphors for display or lighting devices. The blue emission of the Tm3+-doped phosphor had CIE chromaticity coordinates (0.151, 0.033) with a dominant wavelength of 455 nm and a color purity of 94%. The Er3+-doped phosphor had color coordinates (0.249, 0.718), a dominant wavelength of 542 nm, and 92% purity.
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78.55.Hx Other solid inorganic materials
42.70.-a Optical materials

High responsivity 4H-SiC Schottky UV photodiodes based on the pinch-off surface effect

Antonella Sciuto, Fabrizio Roccaforte, Salvatore Di Franco, Vito Raineri, and Giovanni Bonanno

Appl. Phys. Lett. 89, 081111 (2006); http://dx.doi.org/10.1063/1.2337861 (3 pages) | Cited 16 times

Online Publication Date: 23 August 2006

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In this letter, high responsivity 4H-SiC vertical Schottky UV photodiodes based on the pinch-off surface effect, obtained by means of self-aligned Ni2Si interdigit contacts, are demonstrated. The diode area was 1 mm2, with a 37% directly exposed to the radiation. The dark current was about 200 pA at −50 V. Under a 256 nm UV illumination, a current increase of more than two orders of magnitude is observed, resulting in a 78% internal quantum efficiency. The vertical photodiodes showed an ultraviolet-visible rejection ratio >7×103 and a responsivity a factor of about 1.8 higher than a conventional planar metal-semiconductor-metal structure.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.Kk Junction diodes

Dominating radiative recombination in a nanoporous silicon layer with a metal-rich Au (1−α)–SiO2 (α) cermet waveguide

Xiaolong Hu, Yidong Huang, Wei Zhang, and Jiangde Peng

Appl. Phys. Lett. 89, 081112 (2006); http://dx.doi.org/10.1063/1.2336215 (3 pages) | Cited 8 times

Online Publication Date: 23 August 2006

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Aimed at improving the quantum efficiency from nanoporous silicon, a device structure with a metal-rich Au (1−α)–SiO2 (α) cermet nanowaveguide is proposed. By properly choosing the component of the cermet, the surface-plasmon-like dispersion of the nanowaveguide can be engineered so that the density of states for photon is very large at the luminescent frequencies of nanoporous silicon. Consequently, spontaneous emission is greatly enhanced and radiative recombination of the careers becomes the dominating process in a nanoporous silicon layer. The internal quantum efficiency is largely improved.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

Trapping and manipulation of microscopic bubbles with a scanning optical tweezer

P. H. Jones, E. Stride, and N. Saffari

Appl. Phys. Lett. 89, 081113 (2006); http://dx.doi.org/10.1063/1.2338512 (3 pages) | Cited 15 times

Online Publication Date: 23 August 2006

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The authors have demonstrated three-dimensional trapping of ultrasound contrast agent microbubbles using a circularly scanning optical tweezers to confine the microbubble in a time-averaged optical potential. They have measured the maximum transverse drag force that may be applied to the trapped microbubble before it escapes and found that this decreases significantly at small trap radii. They explain this in terms of the relative volumes of the microbubble and the trap and anticipate that this feature will be important in experiments involving the insonation of optically trapped microbubbles.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
47.55.D- Drops and bubbles
47.55.-t Multiphase and stratified flows
43.35.-c

Observation of transient reorientation of dye-doped liquid crystals by pumped attenuated total reflection

Kuang-Yao Lo and Chia-Yi Huang

Appl. Phys. Lett. 89, 081114 (2006); http://dx.doi.org/10.1063/1.2338561 (3 pages)

Online Publication Date: 23 August 2006

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A transient reorientation of liquid crystals in azo-dye-doped liquid crystals (ADDLCs) is observed by the improved attenuated total reflection leading a pump light into a coupling prism, namely, pumped ATR experiment. The evanescent wave of the pump light induces the photoexcitation of azo dye at the limited effective depth, and the evanescent wave of the probe light detects the dynamic behavior in real time. The time response of the photoexcitation in ADDLCs in the pumped ATR experiment is less than 2 ms and it is believed that the reaction occured in the local region of 100 nm.
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42.70.Df Liquid crystals
61.30.-v Liquid crystals

Quasi-continuous-wave operation of an organic thin-film distributed feedback laser

T. Rabe, K. Gerlach, T. Riedl, H.-H. Johannes, W. Kowalsky, J. Niederhofer, W. Gries, J. Wang, T. Weimann, P. Hinze, F. Galbrecht, and U. Scherf

Appl. Phys. Lett. 89, 081115 (2006); http://dx.doi.org/10.1063/1.2337873 (3 pages) | Cited 16 times

Online Publication Date: 24 August 2006

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The operation of organic thin-film distributed feedback lasers at repetition rates up to 5 MHz is studied. The active organic medium consists of a highly efficient, modified poly(9,9-dioctylfluorene) derivative containing 12% of statistical intrachain 6,6′ -(2,2′-octyloxy-1,1′-binaphthalene) binaphthyl spacer groups. The threshold energy density of these pulsed optically pumped lasers remains virtually unaltered at elevated repetition rates up to 5 MHz. Therefore, we conclude that on this time scale photoinduced absorption which might affect the waveguide loss or the overall quantum efficiency is negligible in our active polymer. These results state an organic solid-state laser operating at repetition rates in the megahertz range which for many applications can be considered as quasi-cw.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems

Wide band gap photonic structures in dichromate gelatin emulsions

Rui Ma, Jun Xu, and Wing Yim Tam

Appl. Phys. Lett. 89, 081116 (2006); http://dx.doi.org/10.1063/1.2240646 (3 pages) | Cited 16 times

Online Publication Date: 24 August 2006

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The authors report the fabrication of wide band gap photonic crystals with planar structures in dichromate gelatin emulsions using a two-beam holographic method. By exploiting the differential swelling of the gelatin, planar structures with gradient spacing are fabricated. The crystals exhibit high efficiencies and wide band gaps in the visible range. The authors model the planar gelatin system by an effective medium approach and use transfer matrix to calculate the reflectance and transmittance. Good agreement is obtained between theory and experiment.
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42.70.Qs Photonic bandgap materials
42.40.Kw Holographic interferometry; other holographic techniques
82.70.Gg Gels and sols
82.70.Kj Emulsions and suspensions
82.35.-x Polymers: properties; reactions; polymerization

Nonlinear dynamics in thin-slice Nd:YAG ceramic lasers: Coupled local-mode laser model

Kenju Otsuka, Tatsuro Narita, Yoshihiko Miyasaka, Chi-Ching Lin, Jing-Yuan Ko, and Shu-Chun Chu

Appl. Phys. Lett. 89, 081117 (2006); http://dx.doi.org/10.1063/1.2337993 (3 pages) | Cited 8 times

Online Publication Date: 24 August 2006

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The authors propose a coupled spatially distributed local-mode laser model for understanding self-induced high-speed modulations in Nd:YAG ceramic lasers with laser-diode end pumping, which critically depend on pump positions. In addition to complicated high-speed modulations, quasiperiodic and chaotic relaxation oscillations have been demonstrated experimentally and reproduced by numerical simulation of the model of coupled local-mode lasers. Q-switching-like periodic spiking pulsations have been also observed and reproduced numerically by assuming saturable absorber type of inclusions in grain boundaries.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics
42.55.Xi Diode-pumped lasers
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Simple largely tunable optical microcavity

A. Kiraz, A. Kurt, M. A. Dündar, and A. L. Demirel

Appl. Phys. Lett. 89, 081118 (2006); http://dx.doi.org/10.1063/1.2335371 (3 pages) | Cited 23 times

Online Publication Date: 24 August 2006

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The authors demonstrate more than 9 nm tunability of the whispering gallery modes (WGMs) of rhodamine B doped water microdroplets resting on a superhydrophobic surface. Tunability was achieved by controlling the size of the microdroplets in a current controlled mini humidity chamber. WGMs were observed with quality factors of more than 8000 when kept stable. The sensitivity of the resonances to the size and shape of the microdroplet reveals opportunities for the use of this technique as a probe to characterize superhydrophobic surfaces and investigate liquid-solid surfaces.
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42.79.-e Optical elements, devices, and systems
47.55.D- Drops and bubbles

In-phase evanescent coupling of two-dimensional arrays of defect cavities in photonic crystal vertical cavity surface emitting lasers

James J. Raftery, Ann C. Lehman, Aaron J. Danner, Paul O. Leisher, Antonios V. Giannopoulos, and Kent D. Choquette

Appl. Phys. Lett. 89, 081119 (2006); http://dx.doi.org/10.1063/1.2336618 (3 pages) | Cited 21 times

Online Publication Date: 24 August 2006

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In-phase evanescent coupling in 2×1 and 2×2 arrays of defect cavities in photonic crystal (PhC) vertical cavity surface emitting lasers (VCSELs) is reported. Two-dimensional PhC patterns of air holes containing multiple defects are etched into the top distributed Bragg reflector of VCSELs. The resulting modification of the effective index and optical loss results in evanescent coupling between the multiple defect cavities of the PhC VCSEL. Far field measurements and simulations show good agreement and demonstrate the in-phase results.
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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
42.70.Qs Photonic bandgap materials

Oscillating wave sensors based on ultrahigh-order modes in symmetric metal-clad optical waveguides

Guang Chen, Zhuangqi Cao, Jianghua Gu, and Qishun Shen

Appl. Phys. Lett. 89, 081120 (2006); http://dx.doi.org/10.1063/1.2338536 (3 pages) | Cited 5 times

Online Publication Date: 24 August 2006

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An oscillating wave sensor that uses ultrahigh-order modes in symmetric metal-clad waveguide with submillimeter scale is investigated to measure minute changes in refractive index (RI) of aqueous solution. In the proposed sensor, the sample acts as the guiding layer where oscillating wave propagates. Owing to the concentrated power in the sensing region and the use of the very sensitive ultrahigh-order modes, it is demonstrated both theoretically and experimentally that its sensitivity is enhanced by one order of magnitude than that of evanescent wave sensor. The sensor also provides a wide detection range of RI from 1 to 2.0 or higher.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Gn Optical waveguides and couplers
07.60.Hv Refractometers and reflectometers

Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region

Hideo Kawanishi, Masanori Senuma, Mao Yamamoto, Eiichiro Niikura, and Takeaki Nukui

Appl. Phys. Lett. 89, 081121 (2006); http://dx.doi.org/10.1063/1.2338543 (3 pages) | Cited 21 times

Online Publication Date: 24 August 2006

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We studied the anisotropic optical properties of c-plane AlxGa1−xN multiple quantum wells and m-plane AlxGa1−xN single layer grown on a SiC substrate. Very weak surface emission was detected from c-plane samples with x = 0.66–0.76 (emission wavelength of 228–240 nm), although strong surface emission was detected from c-plane samples with x = 0–0.41 (280–365 nm) and m-plane samples with x = 0–0.76 (240–365 nm). These results indicate that crystal-field splitoff hole valence band plays an important role in (E‖c) polarization and isotropic emissions from AlxGa1−xN with x≧0.5.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
71.70.Ch Crystal and ligand fields
73.20.At Surface states, band structure, electron density of states

High power gain-switched laser diode using a superfast GaAs avalanche transistor for pumping

Brigitte Lanz, Sergey Vainshtein, and Juha Kostamovaara

Appl. Phys. Lett. 89, 081122 (2006); http://dx.doi.org/10.1063/1.2337105 (3 pages) | Cited 5 times

Online Publication Date: 24 August 2006

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Multiwatt single picosecond optical pulses were generated by gain-switched laser diodes using for pumping a superfast GaAs switch, which produces 1–10 A current pulses with a duration comparable to the lasing delay. Good quantitative agreement was found between the measured and simulated optical responses and time-resolved spectra when lasing occurred before the trailing edge of the current pulse, while the measured single optical pulse generated near the trailing edge drastically exceeded that in the simulations. This difference is attributed to the effect of additional population of the quantum well by carriers accumulating earlier in the optical confinement region.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
85.30.Pq Bipolar transistors

Bias-current dependence of anticorrelation polarization dynamics in vertical-cavity surface-emitting lasers with long external cavity

Yanhua Hong, Jon Paul, Paul S. Spencer, and K. Alan Shore

Appl. Phys. Lett. 89, 081123 (2006); http://dx.doi.org/10.1063/1.2338765 (3 pages) | Cited 2 times

Online Publication Date: 25 August 2006

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The bias-current dependence of anticorrelation polarization dynamics in vertical-cavity surface-emitting lasers with long external cavity has been studied experimentally. With fixed optical feedback strength, the minimum cross-correlation coefficient exhibits exponential decay with the bias current. Strong anticorrelation is obtained at frequencies lower than 1 GHz for all bias currents. Near the relaxation oscillation frequency good correlation is found at higher bias current but poor correlation is found at lower bias currents.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Stable mode locking via ground- or excited-state transitions in a two-section quantum-dot laser

M. A. Cataluna, W. Sibbett, D. A. Livshits, J. Weimert, A. R. Kovsh, and E. U. Rafailov

Appl. Phys. Lett. 89, 081124 (2006); http://dx.doi.org/10.1063/1.2338767 (3 pages) | Cited 18 times

Online Publication Date: 25 August 2006

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The authors demonstrate stable mode locking that involves transitions within either the ground state (1260 nm) or the excited state (1190 nm) in a two-section quantum-dot laser, at repetition frequencies of 21 and 20.5 GHz, respectively. The average power of the mode-locked output was in excess of 35 mW for operation in the ground state and 25 mW in the excited state. The selection of pulse generation between these states in the mode-locking regime is controlled by the electrical biasing conditions.
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42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Planar waveguide-type saturable absorber based on carbon nanotubes

Ken Kashiwagi, Shinji Yamashita, Yusuke Nasu, Hiroshi Yaguchi, Chee Seong Goh, and Sze Yun Set

Appl. Phys. Lett. 89, 081125 (2006); http://dx.doi.org/10.1063/1.2338779 (3 pages) | Cited 9 times

Online Publication Date: 25 August 2006

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The authors propose and demonstrate a planar waveguide-type optical device based on carbon nanotubes (CNTs). They realize saturable absorbers utilizing the interaction between the evanescent field of guiding mode and the CNTs. Saturable absorption characteristics are observed and insertion loss decreases ∼ 3% by high power pulsed laser. The device shows that polarization dependence originated from the asymmetric structure of their device and over 15 dB polarization dependent loss. The saturable absorption is observed only in the polarization state that shows a maximum loss caused by the CNTs.
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42.65.-k Nonlinear optics
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
78.67.Ch Nanotubes
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