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9 Oct 2006

Volume 89, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 151920 (2006); http://dx.doi.org/10.1063/1.2360906 (3 pages)

Aycan Yurtsever, Matthew Weyland, and David A. Muller
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Intersubband resonant enhancement of second-harmonic generation in GaN/AlN quantum wells

L. Nevou, M. Tchernycheva, F. Julien, M. Raybaut, A. Godard, E. Rosencher, F. Guillot, and E. Monroy

Appl. Phys. Lett. 89, 151101 (2006); http://dx.doi.org/10.1063/1.2358118 (3 pages) | Cited 13 times

Online Publication Date: 9 October 2006

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This letter reports on the observation of resonant enhancement by intersubband transitions of the second-harmonic generation of ∼ 1 μm radiation in GaN/AlN quantum wells grown on AlN/c-sapphire templates. Quantum wells with a nominal well thickness of 10 ML have been investigated in terms of intersubband linear and nonlinear optical properties. A strong increase of the second-harmonic conversion is observed at a pump wavelength of ∼ 2 μm, which is attributed to double-resonance enhancement of the nonlinear susceptibility by intersubband transitions. The second-order susceptibility at resonance is of the order of 114 pm/V, in good agreement with calculations.
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78.67.De Quantum wells
78.66.Fd III-V semiconductors
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.An Optical susceptibility, hyperpolarizability
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

All-angle negative refraction and evanescent wave amplification using one-dimensional metallodielectric photonic crystals

Hocheol Shin and Shanhui Fan

Appl. Phys. Lett. 89, 151102 (2006); http://dx.doi.org/10.1063/1.2360187 (3 pages) | Cited 20 times

Online Publication Date: 9 October 2006

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The authors numerically demonstrate all-angle negative refraction for propagating waves, as well as evanescent wave amplifications, using a one-dimensional photonic crystal consisting of metal-dielectric multilayers. Their structure has uniform surfaces parallel to the object plane and operates at the visible wavelength range. Using realistic material parameters including loss, they design a Ag–Si3N4 multilayer structure and verified its subwavelength resolution in the image formation process.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Ultrafast hole burning in intersubband absorption lines of GaN/AlN superlattices

Z. Wang, K. Reimann, M. Woerner, T. Elsaesser, D. Hofstetter, E. Baumann, F. R. Giorgetta, H. Wu, W. J. Schaff, and L. F. Eastman

Appl. Phys. Lett. 89, 151103 (2006); http://dx.doi.org/10.1063/1.2360218 (3 pages) | Cited 5 times

Online Publication Date: 9 October 2006

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The authors present evidence for a distinct optical phonon progression in the nonlinear intersubband absorption spectra of electrons in a GaN/AlN superlattice. Femtosecond two-color pump-probe experiments in the near infrared show spectral holes separated by the longitudinal optical (LO) phonon frequency and a homogeneous line broadening of approximately 50 meV. The nonlinear bleaching signal decays with a time constant of 160 fs due to intersubband scattering of delocalized electrons, followed by a weak picosecond component attributed to the relaxation of electrons from longer-lived localized states.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
73.21.Cd Superlattices
78.47.-p Spectroscopy of solid state dynamics
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Quantum-confined Stark effect in interdiffused quantum dots

Y. Wang, H. S. Djie, and B. S. Ooi

Appl. Phys. Lett. 89, 151104 (2006); http://dx.doi.org/10.1063/1.2358296 (3 pages) | Cited 4 times

Online Publication Date: 9 October 2006

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The authors theoretically investigate the effects of isotropic composition interdiffusion on the optical transition energy of quantum-dot (QD) structures under an electric field. Their three-dimensional QD calculation is based on coupled InAs/GaAs QDs arranged periodically in a tetragonal superlattice, taking into account the effects of finite band offset, valence-band mixing, strain, effective mass anisotropicity, and different QD shapes. The electron and hole Hamiltonians with the interdiffusion effect are solved in the momentum space domain. The enhanced Stark shifts and the reduced built-in dipole moment have been found for the interdiffused QD structures.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
73.21.La Quantum dots

Asymmetric long period fiber gratings fabricated by use of CO2 laser to carve periodic grooves on the optical fiber

Yi-Ping Wang, D. N. Wang, Wei Jin, Yun-Jiang Rao, and Gang-Ding Peng

Appl. Phys. Lett. 89, 151105 (2006); http://dx.doi.org/10.1063/1.2360253 (3 pages) | Cited 20 times

Online Publication Date: 9 October 2006

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An asymmetric long period fiber grating (LPFG) with a large attenuation of −47.39 dB and a low insertion loss of 0.34 dB is fabricated by use of focused CO2 laser beam to carve periodic grooves on one side of the optical fiber. Such periodic grooves and the stretch-induced periodic microbends can effectively enhance the refractive index modulation and increase the average strain sensitivity of the resonant wavelength of the LPFG to −102.89 nm/mε. The resonant wavelength and the peak attenuation of the LPFG can be tuned by ∼ 12 nm and ∼ 20 dB, respectively, by the application of a stretching force.
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42.81.Bm Fabrication, cladding, and splicing
42.81.Wg Other fiber-optical devices
42.81.Dp Propagation, scattering, and losses; solitons
42.79.Dj Gratings
42.62.-b Laser applications

Determining the temporally and radially resolved temperature distribution inside a pulsed broad-area vertical-cavity surface-emitting laser cavity

Shyam K. Mandre, Wolfgang Elsäßer, Ingo Fischer, Michael Peeters, and Guy Verschaffelt

Appl. Phys. Lett. 89, 151106 (2006); http://dx.doi.org/10.1063/1.2361164 (3 pages) | Cited 4 times

Online Publication Date: 9 October 2006

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The authors experimentally determine temporally and radially resolved profiles of the temperature distribution within the cavity of a broad-area vertical-cavity surface-emitting laser in pulsed operation. For this, the recently discovered state of spatially incoherent emission [ M. Peeters et al., Opt. Express 13, 9337 (2005) ] is harnessed. Using single-shot measurements of spectrally resolved near field profiles acquired by a fast-gated charge coupled device camera, the wavelength shift due to heating of the device is temporally and radially resolved. From the wavelength shift the temperature shift is extracted, which finally allows for determination of absolute temperature profiles.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Band structure mapping of photonic crystal intersubband detectors

S. Schartner, S. Golka, C. Pflügl, W. Schrenk, A. M. Andrews, T. Roch, and G. Strasser

Appl. Phys. Lett. 89, 151107 (2006); http://dx.doi.org/10.1063/1.2361186 (3 pages) | Cited 17 times

Online Publication Date: 9 October 2006

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The authors report on a quantum well infrared detector embedded in a surface-plasmon waveguide and processed into a deeply etched photonic crystal structure. The device was characterized by collecting the polarization dependent response spectra at different angles of incidence. With this method it is possible to map the photonic band structure by directly detecting the modes of the photonic crystal. It therefore represents a new and direct characterization procedure for photonic crystals. The device shows a strong mixing between TE and TM polarized modes, which is caused by the asymmetric vertical waveguide design.
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42.70.Qs Photonic bandgap materials
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Gn Optical waveguides and couplers
42.15.Eq Optical system design

Highly sensitive biosensing based on interference from light scattering in capillary tubes

Henrik S. Sørensen, Niels B. Larsen, Joey C. Latham, Darryl J. Bornhop, and Peter E. Andersen

Appl. Phys. Lett. 89, 151108 (2006); http://dx.doi.org/10.1063/1.2356380 (3 pages) | Cited 3 times

Online Publication Date: 9 October 2006

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Human IgG interactions with surface bound protein A are monitored label-free using microinterferometric backscatter detection. An electromagnetic wave-based model is developed and used to quantitatively describe the change in interference pattern as a consequence of the molecular interaction with the affinity layer on the fused silica capillary. Within the framework of the model it is of paramount importance to establish a valid stop criterion for the infinite summations involved in the fringe pattern computations. The high sensitivity towards surface changes, ease of changing the surface chemistry to other specific interacting layers, and simplicity of the optical sensor make this technique a powerful tool in biosensing.
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87.80.-y Biophysical techniques (research methods)
87.14.E- Proteins
87.15.N- Properties of solutions of macromolecules
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

nBn detector, an infrared detector with reduced dark current and higher operating temperature

S. Maimon and G. W. Wicks

Appl. Phys. Lett. 89, 151109 (2006); http://dx.doi.org/10.1063/1.2360235 (3 pages) | Cited 52 times

Online Publication Date: 10 October 2006

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This letter presents a type of infrared detector named the nBn detector. The nBn design essentially eliminates Shockley-Read-Hall generation currents. The result is greatly reduced dark current and noise, compared to other midwave infrared detectors, such as p-n photodiodes. This enables the nBn to operate at background-limited infrared photodetection conditions at significantly higher temperatures than conventional midwave infrared detectors and have greater detectivity near room temperature. The nBn is demonstrated in InAs and InAsSb materials, exhibiting cutoff wavelengths of 3.4 and 4.2 μm, respectively.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Silicon micromachined periodic structures for optical applications at λ = 1.55 μm

G. Barillaro, A. Diligenti, M. Benedetti, and S. Merlo

Appl. Phys. Lett. 89, 151110 (2006); http://dx.doi.org/10.1063/1.2358323 (3 pages) | Cited 13 times

Online Publication Date: 10 October 2006

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In this letter, the authors report the design, fabrication, and characterization of a silicon micromachined periodic structure for optical applications at λc = 1.55 μm. The microstructure, which can be envisioned as a one-dimensional photonic crystal, is composed of a periodic array of 1-μm-thick silicon walls and 2-μm-wide air gaps, each one corresponding to a different odd number of quarter wavelength at λc (hybrid quarter wavelength). The fabrication is based on the electrochemical etching of silicon, yielding parallel trenches with depths up to 100 μm. Preliminary reflectivity measurements show the presence of a band gap at λc = 1.55 μm, as theoretically expected.
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42.70.Qs Photonic bandgap materials
42.15.Eq Optical system design

One-dimensional magnetic grating structure made easy

J. B. Kim, G. J. Lee, Y. P. Lee, J. Y. Rhee, K. W. Kim, and C. S. Yoon

Appl. Phys. Lett. 89, 151111 (2006); http://dx.doi.org/10.1063/1.2355455 (3 pages) | Cited 8 times

Online Publication Date: 10 October 2006

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A simple and easy method of the fabrication of one-dimensional magnetic grating structure is developed. By using the interference pattern of two femtosecond laser beams, a selective-area annealing of as-deposited Co2MnSi film was achieved and one-dimensional magnetic grating structures were fabricated. The as-deposited films exhibit no magnetic response at room temperature. Several microscopies were applied to confirm the periodic crystalline and magnetic structures. The Faraday-like rotation of the polarization of the zeroth- and first-order diffracted beams were measured, and that of the first-order diffracted beam is nearly six times larger than that of the zeroth-order beam.
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42.79.Dj Gratings
42.86.+b Optical workshop techniques
42.62.-b Laser applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Near-infrared wavelength intersubband transitions in GaN/AlN short period superlattices

E. A. DeCuir, Emil Fred, B. S. Passmore, A. Muddasani, M. O. Manasreh, Jinqiao Xie, Hadis Morkoç, M. E. Ware, and G. J. Salamo

Appl. Phys. Lett. 89, 151112 (2006); http://dx.doi.org/10.1063/1.2358929 (3 pages) | Cited 3 times

Online Publication Date: 10 October 2006

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Intersubband transitions in GaN/AlN short period superlattices prepared by molecular beam epitaxy were investigated using the optical absorption technique. The peak position wavelengths of these transitions are found to span the spectral range of 1.35–2.90 μm for samples cut into 45° waveguides with GaN quantum well thicknesses ranging between 1.70 and 2.41 nm. The Fermi energy levels are estimated from the carrier concentrations, which were measured using an electrochemical capacitance-voltage profiler. The well widths were inferred from comparing the measured peak position energy of the intersubband transitions and the bound state energy levels calculated using the transfer matrix method.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.30.Fs III-V and II-VI semiconductors
73.20.At Surface states, band structure, electron density of states
42.79.Gn Optical waveguides and couplers

Individual classification of buried transistors in live microprocessors by functional infrared emission spectral microscopy

Wilma Oblefias, Maricor Soriano, Alvarado Tarun, and Caesar Saloma

Appl. Phys. Lett. 89, 151113 (2006); http://dx.doi.org/10.1063/1.2358935 (3 pages) | Cited 2 times

Online Publication Date: 10 October 2006

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The authors classify good, leaky, and broken field effect transistors (FET’s) in a live 90 nm flip-chip microprocessor using functional infrared emission spectral microscopy. The FET’s are in the active layer that is sandwiched between a thick heat-absorbing silicon material and a highly reflecting grid of metal interconnects. Together they are optically imaged only as a single bright blob. They classify FET’s individually from their distinct electroluminescence spectra that are recovered efficiently by spectral decomposition of the detected composite spectrum. Leaky FET’s have no apparent structural damage and are detectable only in live microprocessors.
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85.40.Qx Microcircuit quality, noise, performance, and failure analysis
85.30.Tv Field effect devices
85.40.Ls Metallization, contacts, interconnects; device isolation

Resonant tunneling diode made of organic semiconductor superlattice

Tae Jin Park, Yong Kyun Lee, Soon Kab Kwon, Jang Hyuk Kwon, and Jin Jang

Appl. Phys. Lett. 89, 151114 (2006); http://dx.doi.org/10.1063/1.2358936 (3 pages) | Cited 11 times

Online Publication Date: 10 October 2006

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The authors studied the current-voltage characteristics of the organic superlattices of an ITO/1,3,5-tris-(3-methylphenylphenylamino) triphenylamine (m-MTDATA) (5 nm)/[m-MTDATAand 4,7diphenyl-1,10-phenanthroline (Bphen)]4/Bphen (5 nm)/LiF/Al. The thickness of m-MTDATA was varied from 3 to 7 nm with the fixed Bphen thickness at 3 nm. The current-voltage characteristics of the organic superlattice show a peak and a valley between 3 and 8 V when the thickness of m-MTDATA is 7 nm, which is due to the resonant tunneling currents. It is found that there is no luminance by the resonant tunneling currents.
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85.30.Kk Junction diodes

Utilization of water/alcohol-soluble polyelectrolyte as an electron injection layer for fabrication of high-efficiency multilayer saturated red-phosphorescence polymer light-emitting diodes by solution processing

Lei Wang, Bo Liang, Fei Huang, Junbiao Peng, and Yong Cao

Appl. Phys. Lett. 89, 151115 (2006); http://dx.doi.org/10.1063/1.2358942 (3 pages) | Cited 26 times

Online Publication Date: 10 October 2006

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Highly efficient multilayer red polymer light-emitting diodes were fabricated by solution process-ing from iridium complex, bis(1-(3-(9,9-dimethyl-fluorene-2-yl)phenyl)isoquinoline-C2,N′) iridium(III)acetylacetonate, doped into polyfluorene as a host and with a water/alcohol-soluble polymer, poly[(9,9-bis(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene)-4,7-(2,1,3-benzoselenadiazole)]dibromide (PFN) as electron injection layer. The device with the structure ITO/PEDOT-PSS(50 nm)/PVK(40 nm)/PFO:PBD:Ir(DMFPQ)2acac(2%,75 nm)/PFN(20 nm)/Ba(4.5 nm)/Al(150 nm) showed an external quantum efficiency of 18.0% and luminance efficiency of 9.8 Cd/A at a current density of 1.1 mA/cm2, a peak emission at λmax = 636 nm, and Commission International de I’Eclairage coordinates of (0.665, 0.319). The efficiency remained as high as QE = 11.1%, and LE = 6.0 cd/A, at a current density of 100 mA/cm2, and a luminance of 6140 cd/m2.
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85.60.Jb Light-emitting devices

Design of midinfrared photodetectors enhanced by surface plasmons on grating structures

Zongfu Yu, Georgios Veronis, Shanhui Fan, and Mark L. Brongersma

Appl. Phys. Lett. 89, 151116 (2006); http://dx.doi.org/10.1063/1.2360896 (3 pages) | Cited 41 times

Online Publication Date: 11 October 2006

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The authors propose to exploit the unique properties of surface plasmons to enhance the signal-to-noise ratio of midinfrared photodetectors. The proposed photodetector consists of a slit in a metallic slab filled with absorptive semiconductor material. Light absorption in the slit is enhanced due to Fabry-Perot resonances. Further absorption enhancement is achieved by surrounding the slit with a series of periodic grooves that enable the excitation of surface plasmons that carry electromagnetic energy towards the slit. Using this scheme, they design and optimize a photodetector operating at λ0 = 9.8 μm with a roughly 250 times enhancement in the absorption per unit of volume of semiconductor material compared to conventional photodetectors operating at the same wavelength.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Dj Gratings
42.82.Gw Other integrated-optical elements and systems

Saturable absorption of highly stacked InAs quantum dot layer in 1.5 μm band

Jun Inoue, Toshiro Isu, Kouichi Akahane, and Masahiro Tsuchiya

Appl. Phys. Lett. 89, 151117 (2006); http://dx.doi.org/10.1063/1.2357598 (3 pages) | Cited 4 times

Online Publication Date: 11 October 2006

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The authors examined 1.5 μm band absorption saturation properties of 150 stacked InAs quantum dot layers on InP substrate. The transmission change at the vertical incidence based on the saturable absorption of the quantum dots was as much as 1%. Theoretical prediction shows that the transmission change could be greatly increased by removing the InP substrate. After grinding the substrate and antireflection coating on both surfaces, transmittance change was build up to 3%. It is thus concluded that highly stacked quantum dot layers are potentially applicable to a planar-type mode locker for short optical pulse generation in the 1.5 μm band.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Temperature dependence of threshold current in p-doped quantum dot lasers

I. C. Sandall, P. M. Smowton, J. D. Thomson, T. Badcock, D. J. Mowbray, H.-Y. Liu, and M. Hopkinson

Appl. Phys. Lett. 89, 151118 (2006); http://dx.doi.org/10.1063/1.2361167 (3 pages) | Cited 19 times

Online Publication Date: 11 October 2006

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The authors measure the temperature dependence of the components of threshold current of 1300 nm undoped and p-doped quantum dot lasers and show that the temperature dependence of the injection level necessary to achieve the required gain is the largest factor in producing the observed negative T0 in p-doped quantum dot lasers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Gain and lifetime of GaInNAsSb narrow ridge waveguide laser diodes in continuous-wave operation at 1.56 μm

J. A. Gupta, P. J. Barrios, J. A. Caballero, D. Poitras, G. C. Aers, G. Pakulski, and X. Wu

Appl. Phys. Lett. 89, 151119 (2006); http://dx.doi.org/10.1063/1.2361179 (3 pages) | Cited 8 times

Online Publication Date: 11 October 2006

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The continuous-wave (cw) operation of GaInNAsSb lasers at 1560 nm is reported. Light-current measurements were made before and after a 100 h cw burn in at 20 °C, during which a 3×890 μm2 device with 72 mA initial threshold current and 14 mW maximum output power experienced a 15% drop in peak output power. These preliminary lifetime results provide insight into the reliability of GaInNAsSb active regions and reinforce the promise of this material for C-band devices. High-resolution modal gain spectra were extracted from the amplified spontaneous emission spectra acquired after the burn in, providing reliable values for the internal loss, transparency current, and differential gain.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Optically pumped semiconductor disk laser with graded and step indices

Florian Saas, Vadim Talalaev, Uwe Griebner, Jens W. Tomm, Martin Zorn, Andrea Knigge, and Markus Weyers

Appl. Phys. Lett. 89, 151120 (2006); http://dx.doi.org/10.1063/1.2359580 (3 pages) | Cited 2 times

Online Publication Date: 11 October 2006

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Results of a study of different gain section designs in nonresonantly optically pumped vertically emitting semiconductor disk lasers (SCDLs) are presented. Clear superiority of structures with barriers based on graded-gap layers is demonstrated. This finding is assigned to the lack of absorption saturation within the barriers caused by the efficient carrier collection capabilities of graded structures compared to ungraded ones. Transient photoluminescence experiments providing direct access to the carrier transfer from the barrier to the quantum-well active region confirm this explanation. Consequently, the authors propose graded designs for SCDLs.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Sub-nanometric metallic Au clusters as efficient Er3+ sensitizers in silica

Enrico Trave, Giovanni Mattei, Paolo Mazzoldi, Giovanni Pellegrini, Carlo Scian, Chiara Maurizio, and Giancarlo Battaglin

Appl. Phys. Lett. 89, 151121 (2006); http://dx.doi.org/10.1063/1.2266229 (3 pages) | Cited 21 times

Online Publication Date: 12 October 2006

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Silica films co-implanted with Er and Au ions show an enhancement of rare earth photoluminescence after gold introduction in the matrix. Er excitation originates in a broad spectral region, from the red to the near ultraviolet. We have investigated the influence of gold aggregation on the optical properties of co-doped samples by varying the temperature of post-Au implantation annealing in the 400–900 °C range. Optical measurements and extended x-ray absorption analysis support the hypothesis of an energy transfer process mediated by sub-nanometric Au aggregates with metallic character that are optically activated mostly through electron interband transitions between d and sp-conduction levels.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
61.72.up Other materials
81.40.Gh Other heat and thermomechanical treatments
78.70.Dm X-ray absorption spectra

Optimizing the performance of a vertical-cavity surface-emitting laser

S. Chatterjee, W. Wohlleben, C. Lange, W. Stolz, M. Motzkus, and W. Rühle

Appl. Phys. Lett. 89, 151122 (2006); http://dx.doi.org/10.1063/1.2361199 (3 pages) | Cited 1 time

Online Publication Date: 12 October 2006

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The pulse response of an optically excited vertical-cavity surface-emitting laser is optimized by shaping the pump pulse. The temporal phase and amplitude of the excitation are adjusted by a learning loop with live spectrotemporal monitoring of excitation and emission pulses using a streak camera. The genetic algorithm of the loop is inspired by the optimization occurring in evolution in biology. The pulse response is such decreased from 4.8 to 2 ps. Emission intensity shows strong correlation with the pulse delay and also improves by 63%.
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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
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
02.60.Pn Numerical optimization

Characterization of ultrashallow junctions using frequency-dependent junction photovoltage and its lateral attenuation

V. N. Faifer, M. I. Current, and D. K. Schroder

Appl. Phys. Lett. 89, 151123 (2006); http://dx.doi.org/10.1063/1.2362596 (3 pages) | Cited 6 times

Online Publication Date: 13 October 2006

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A contactless method for ultrashallow junction (USJ) characterization is described based on analysis of frequency-dependent junction photovoltages from illuminated and nonilluminated areas. Relevant equations for junction photovoltages are derived. It is shown that the measured leakage current in USJ formed in halo profiles is related to space-charge region recombination.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.40.+w Photoconduction and photovoltaic effects

Continuous light-shift correction in modulated coherent population trapping clocks

V. Shah, V. Gerginov, P. D. D. Schwindt, S. Knappe, L. Hollberg, and J. Kitching

Appl. Phys. Lett. 89, 151124 (2006); http://dx.doi.org/10.1063/1.2360921 (3 pages) | Cited 7 times

Online Publication Date: 13 October 2006

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The authors demonstrate a simple technique to significantly improve the long-term frequency stability of atomic clocks based on coherent population trapping (CPT). In this technique, the CPT fields are created by a modulated diode laser and a slow servo is used to actively tune the laser modulation index to a value where the light shift vanishes. The observed clock frequency at this modulation index is given by the rubidium hyperfine frequency when no light fields are present, and this makes the clock frequency largely insensitive to variations in laser properties. In addition to reducing stringent requirements on the long-term stabilities of laser temperature, laser frequency, and rf modulation power, this technique may also significantly reduce frequency drifts related to laser aging. In the experiment, they demonstrate improvement by over one order of magnitude in the stability of a clock that is limited by light-shift-induced frequency drifts.
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37.10.De Atom cooling methods
37.10.Gh Atom traps and guides
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
06.20.fb Standards and calibration
06.30.Ft Time and frequency
31.30.Gs Hyperfine interactions and isotope effects

Generation of high-fidelity, down-chirped sub-10 fs mJ pulses through filamentation for driving relativistic laser-matter interactions at 1 kHz

C. P. Hauri, A. Trisorio, M. Merano, G. Rey, R. B. Lopez-Martens, and G. Mourou

Appl. Phys. Lett. 89, 151125 (2006); http://dx.doi.org/10.1063/1.2360935 (3 pages) | Cited 17 times

Online Publication Date: 13 October 2006

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The authors present a simple add on for multicycle, multimJ Ti:sapphire-based amplifier systems to efficiently generate 9.5 fs pulses with 1.8 mJ. Filamentary propagation yields spectrally broadened pulses carrying an unexpected large group-delay dispersion of −500 fs2 which allows linear propagation of the few-cycle pulses towards target areas without need of any sophisticated dispersion control. Pulse compression could easily be achieved by transmission through a combination of different glass substrates. The pulse wave front, the low energy fluctuations, and the good temporal contrast make this source well suited for relativistic laser-solid experiments with intense few-cycle pulses at kilohertz repetition rate.
Show PACS
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
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