jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

15 Aug 2005

Volume 98, Issue 4, Articles (04xxxx)

Return to All Sections
back to top
RSS Feeds

Improvement of the atmospheric discharge laser-triggered ability using multiple pulses from a kilohertz KrF laser

Michiteru Yamaura

J. Appl. Phys. 98, 043101 (2005); http://dx.doi.org/10.1063/1.2009076 (4 pages) | Cited 2 times

Online Publication Date: 17 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The potential ability of lasers to control lightning can be improved by using a train of pulses with submillisecond separations. Laser-triggered experiments in a small-scale (10‐mm gap) atmospheric discharge facility show that the triggering is dramatically enhanced when a five-pulse train of sub-Joule energy is used instead of a single pulse. This effect increases rapidly as the pulse interval is reduced. It appears that at a submillisecond pulse interval, sufficient positive and negative ions survive in subsequent pulses, thus enabling easy deionization. Hence, significant plasma buildup occurs from one pulse to the next. However, this persistence of ions would appear to imply that the rate of recombination (effectively a charge transfer between ions) is considerably lower than previously believed.
Show PACS
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.-b Plasma properties

Theoretical analysis of feedback mechanisms of two-dimensional finite-sized photonic-crystal lasers

S. Nojima

J. Appl. Phys. 98, 043102 (2005); http://dx.doi.org/10.1063/1.2001150 (9 pages) | Cited 8 times

Online Publication Date: 17 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Theoretical investigations are carried out for close-to-lasing two-dimensional finite-sized photonic crystals with active (gain) lattice points. First, laser oscillations with lower thresholds are found to occur near the photonic band edges where optical gain is enormously intensified. For several modes isolated around the band edge, the field-intensity spectra in reciprocal space and the Poynting-vector distributions in real space are investigated in detail in close-to-lasing photonic crystals. By comparing the phenomena that occur in photonic crystals with a symmetric or an asymmetric outward form, this paper clarifies the differences in the feedback mechanisms of these crystals. In a symmetric photonic crystal, laser oscillation occurs through the waves propagating along the straight passages. This feedback is basically the same as that of ordinary one-dimensional lasers, although it exhibits a complicated behavior that light waves propagating in a variety of directions interfere with each other. In an asymmetric photonic crystal, laser oscillation occurs through the waves circulating within the crystal, which could be called recurrent-photon feedback. This feedback, however, can be construed as an extension of the feedback in ordinary one-dimensional distributed-feedback lasers.
Show PACS
42.55.Tv Photonic crystal lasers and coherent effects
42.70.Qs Photonic bandgap materials
42.70.Hj Laser materials
42.55.Px Semiconductor lasers; laser diodes

Analytical stress modeling of high-energy laser windows: Application to fusion-cast calcium fluoride windows

Claude A. Klein

J. Appl. Phys. 98, 043103 (2005); http://dx.doi.org/10.1063/1.2007874 (14 pages) | Cited 6 times

Online Publication Date: 18 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The performance of a laser-window material must be assessed not only in terms of its ability to transmit high-power beams without generating undue optical distortion but also in terms of the constraints imposed by stress-related failure modes. In operational use, the stress field images the superposition of stresses originating from the mechanical load created by the pressure differential and the thermal load created by the laser beam. Here, we provide the tools to carry out an analysis of both pressure- and beam-induced stresses, and illustrate the procedure in the context of assessing the performance of a “model” window made of fusion-cast CaF2. The analysis assumes (a) operation on a time scale such that lateral heat diffusion can be ignored, and (b) cylindrically symmetric Gaussian beam shapes, which permit straightforward calculations of stress distributions that should be representative of worst case situations. Pressure-induced stresses strongly depend on the window’s aspect ratio, which suggests increasing the thickness to minimize the stress, but considerations relating to the optical performance require minimum allowable thicknesses based on a Weibull statistical analysis of the fracture probability. Beam-induced stresses are best evaluated in terms of (a) thickness-averaged radial and azimuthal stresses, which increase linearly with exposure time and depend on radial distances through the truncation parameter, and (b) across-the-thickness stress deviations relative to the average stress, which are caused by surface absorption and reach steady-state configurations on a time scale much shorter than the characteristic time for lateral heat transport. The average stress is always compressive and equibiaxial in the central region of the window, but its azimuthal component turns tensile in the rim region, thus threatening the structural integrity through brittle fracture. In addition, the coating-induced stress results in on-axis surface compressions that may exceed the yield strength of the windowpane material. In this light we formulate a figure of merit for stress, which demonstrates that promising laser-window materials must combine a small stress factor (expansion coefficient times elastic modulus) with superior thermal properties in terms of the product of heat capacity and thermal conductivity; CaF2 and SrF2 are the only known candidates that exhibit outstanding optical features at chemical laser wavelengths together with acceptable thermomechanical properties.
Show PACS
42.60.-v Laser optical systems: design and operation
42.79.Ci Filters, zone plates, and polarizers
42.70.Hj Laser materials
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.F- Deformation and plasticity
62.20.M- Structural failure of materials
02.50.Ng Distribution theory and Monte Carlo studies

Organic solid-state lasers based on sexiphenyl as active chromophore

D. Schneider, T. Rabe, T. Riedl, T. Dobbertin, M. Kröger, E. Becker, H.-H. Johannes, W. Kowalsky, T. Weimann, J. Wang, and P. Hinze

J. Appl. Phys. 98, 043104 (2005); http://dx.doi.org/10.1063/1.1991967 (6 pages) | Cited 10 times

Online Publication Date: 18 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on various sexiphenyl derivatives as gain media in organic solid-state lasers. The molecules involved in this research are simple p-sexiphenyl, the laser dye molecule 2,5,2””’,5””’-tetra-t-butyl-p-sexiphenyl (TBS) and the spirolinked sexiphenyl-derivative 2,7-bis(biphenyl-4-yl)-2’,7’-di-tert-butyl-9,9’-spirobifluorene. It appears that the morphology of vacuum-deposited thin films is highly dependent on the sterical dimensions of the respective molecules. Whereas thin films based on simple p-sexiphenyl comprise large clusters which significantly deteriorate their waveguiding properties; films formed by TBS, and the spiroderivative show a dramatically improved morphology with reduced surface roughness. Therefore amplified spontaneous emission (ASE) and lasing are demonstrated in both of the last but not in films based on p-sexiphenyl. Second-order distributed-feedback lasers with TBS as the active medium have been prepared with an emission between 390 and 435 nm depending on the grating period of the Bragg reflector. While the ASE characteristics are similar in films formed by TBS and the spiroderivative, TBS exhibits even superior laser threshold densities which are as low as 45 μJ/cm2 at a wavelength of 396 nm.
Show PACS
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.70.Jk Polymers and organics
42.70.Hj Laser materials
42.79.Wc Optical coatings

Hydrogen analysis in solid samples using laser-induced helium plasma at atmospheric pressure

Marincan Pardede, Koo Hendrik Kurniawan, Tjung Jie Lie, Rinda Hedwig, Nasrullah Idris, Takao Kobayashi, Tadashi Maruyama, Yong Inn Lee, Kiichiro Kagawa, and May On Tjia

J. Appl. Phys. 98, 043105 (2005); http://dx.doi.org/10.1063/1.2009820 (5 pages) | Cited 9 times

Online Publication Date: 19 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A special technique for the modification of laser-induced breakdown spectroscopy (LIBS) has been developed to improve the spectral quality of hydrogen emission from a solid sample in helium gas at atmospheric pressure. In this technique, the plasma was generated by focusing a fundamental Nd-YAG (yttrium aluminum garnet) laser into a surrounding helium gas. The helium atoms excited to their metastable states would then serve to excite the atoms of the solid material vaporized by using another Nd-YAG laser. When properly synchronized, the resulting hydrogen emission line of H I 656.2 nm shows a dramatic improvement of the emission intensity and the spectral quality over what was obtained by conventional LIBS technique. This study further reveals that this improvement is mainly due to the role of the metastable excited state in a helium atom, which allows the delayed detection to be performed at a favorable moment when the charged particles responsible for the strong Stark broadening effect in the plasma have mostly disappeared.
Show PACS
82.80.Dx Analytical methods involving electronic spectroscopy
32.80.Rm Multiphoton ionization and excitation to highly excited states
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
32.60.+i Zeeman and Stark effects

An isotropic three-dimensional negative-refractive-index transmission-line metamaterial

Anthony Grbic and George V. Eleftheriades

J. Appl. Phys. 98, 043106 (2005); http://dx.doi.org/10.1063/1.2007853 (5 pages) | Cited 33 times

Online Publication Date: 22 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We propose an isotropic three-dimensional (3D) negative-refractive-index medium using transmission lines loaded with reactive elements. The medium is referred to as the 3D dual transmission line (TL). Analytical expressions are derived which provide insight into the backward-wave propagation supported by the proposed medium. The dispersion characteristics of a physically realizable 3D dual TL are computed using a full-wave eigenmode solution of Maxwell’s equations based on the finite-element method. In addition, scattering parameters for a slab made of the 3D dual TL are presented. The described approach can be generalized for synthesizing a wide range of 3D metamaterials with tailored material parameters including both isotropic and anisotropic designs.
Show PACS
42.70.-a Optical materials
42.79.Gn Optical waveguides and couplers

Si wafer bonded of a‐Si/a‐SiNx distributed Bragg reflectors for 1.55‐μm-wavelength vertical cavity surface emitting lasers

C. Levallois, A. Le Corre, S. Loualiche, O. Dehaese, H. Folliot, C. Paranthoen, F. Thoumyre, and C. Labbé

J. Appl. Phys. 98, 043107 (2005); http://dx.doi.org/10.1063/1.2009075 (5 pages) | Cited 6 times

Online Publication Date: 22 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Amorphous silicon (a‐Si) and amorphous silicon nitride (a‐SiNx) layers deposited by magnetron sputtering have been analyzed in order to determine their optical and surface properties. A large value of ∼ 1.9 of index difference is found between these materials. Distributed Bragg reflectors (DBRs) based on these dielectric material quarter wave layers have been studied by optical measurements and confronted to theoretical calculations based on the transfer matrix method. A good agreement has been obtained between the experimental and expected reflectivities. A maximum reflectivity of 99.5% at 1.55 μm and a large spectral bandwidth of 800 nm are reached with only four and a half periods of a‐Si/a‐SiNx. No variation of the DBR reflectivity has been observed with the time nor when annealed above 240 °C and stored during few months. This result allows us to use this DBR in a metallic bonding process to realize a vertical cavity surface emitting laser (VCSEL) with two dielectric a‐Si/a‐SiNx DBRs. This bonding method using AuIn2 as the bonding medium and Si substrate can be performed at a low temperature of 240 °C without damaging the optical properties of the microcavity. The active region used for this VCSEL is based on lattice-matched InGaAs/InGaAsP quantum wells and a laser emission has been obtained at room temperature on an optically pumped device.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.15.Cd Deposition by sputtering
81.40.Gh Other heat and thermomechanical treatments
42.79.Bh Lenses, prisms and mirrors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Performance comparison of optically pumped type-II midinfrared lasers

A. P. Ongstad, R. Kaspi, M. L. Tilton, J. R. Chavez, and G. C. Dente

J. Appl. Phys. 98, 043108 (2005); http://dx.doi.org/10.1063/1.2010627 (7 pages) | Cited 6 times

Online Publication Date: 23 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report a comparative study on the performance of three optically pumped, type-II quantum well lasers with differing quantum well (QW) confinement. One of the active regions emphasized hole confinement, another emphasized electron confinement, while the third incorporated both electron and hole confinements. In all cases the wells were inserted in a thick InxGa1−xAsySb1−y waveguide/absorber region. The lasing wavelengths at 84 K were 2.26, 3.44, and 2.37 μm, respectively. The maximum peak output powers and differential quantum efficiencies η at 84 K were similar for the hole well and W lasers ( ≈ 13 W,η ≈ 0.55), but significantly reduced in the electron-well-only laser (2.3 W,η = 0.14). Waveguide loss measurements via the traditional quantum efficiency versus cavity length method and by a Hakki-Paoli method revealed that all three lasers had low waveguide loss that either increased slowly or not at all with increasing temperature. However, the laser’s internal efficiency, ηi, showed a linear decline with increasing temperature, with the ηi of the electron-well-only laser significantly less than the other two. The data suggest that for antimonide-based type-II designs, strong hole confinement is essential for improved performance. The data further suggest that it is hole leakage from the QW and/or hole dilution that is largely responsible for the degradation in laser performance.
Show PACS
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.)
42.79.Gn Optical waveguides and couplers
42.72.Ai Infrared sources

Characterization of long-range surface-plasmon-polariton waveguides

P. Berini, R. Charbonneau, N. Lahoud, and G. Mattiussi

J. Appl. Phys. 98, 043109 (2005); http://dx.doi.org/10.1063/1.2008385 (12 pages) | Cited 87 times

Online Publication Date: 24 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Measurements of the attenuation and excitation efficiency of the long-range surface-plasmon-polariton mode supported by waveguides comprised of one or many thin metal films of finite width embedded in dielectric were made in the near infrared (λ0 = 1550 nm). Au films 31, 25, and 20 nm thick, and Ag films 20 nm thick were used to implement the structures. The lowest attenuations measured among the Au and Ag waveguides are 0.42 and 0.32 dB/mm, respectively, corresponding to propagation lengths of 10 340, and 13 572 μm, respectively. These propagation lengths are longer than those of the single-interface surface-plasmon polariton in the corresponding semi-infinite structures by factors of 93 and 138, respectively. These factors are the largest reported to date for long-range surface-plasmon-polariton waves. The largest excitation efficiency measured among the set of Au structures is 98%. Theoretical results were obtained for all of the structures characterized experimentally using an accurate electromagnetic-field model. Theory and experiment agree to within about 5% over the 31- and 25-nm-thick Au structures, but a thickness-dependant permittivity must be assumed in order to achieve agreement to within 12% for the 20-nm Au structures.
Show PACS
78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
42.79.Gn Optical waveguides and couplers

Nonlinear pulse evolution in seeded free-electron laser amplifiers and in free-electron laser cascades

L. Giannessi, P. Musumeci, and S. Spampinati

J. Appl. Phys. 98, 043110 (2005); http://dx.doi.org/10.1063/1.2010624 (8 pages) | Cited 7 times

Online Publication Date: 24 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The advances in laser technology have made available very short and intense laser pulses which can be used to seed a high-gain single-pass free-electron laser (FEL) amplifier. With these seed pulses, a regime of the FEL interaction where the radiation evolution is simultaneously dominated by nonlinear effects (saturation) and time-dependent effects (slippage) can be explored. This regime is characterized by the propagation of a solitary wavelike pulse where the power of the optical wave grows quadratically with time, its pulse length decreases and the spectral bandwidth increases. We analyze the interplay between the field and particle dynamics of this propagation regime which was studied before and termed super-radiance. Furthermore we analyze the properties of the strong higher-order harmonic emission from this wave and its behavior when propagating in a cascade FEL. The super-radiant pulse is indeed capable of passing through the stages of a cascade FEL and to regenerate itself at the wavelength of the higher-order harmonic. The optical pulse obtained is shorter than a cooperation length and is strongly chirped in frequency, thus allowing further longitudinal compression down to the attosecond time scale.
Show PACS
41.60.Cr Free-electron lasers
42.60.Fc Modulation, tuning, and mode locking
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Photoemission studies on niobium for superconducting photoinjectors

J. Smedley, T. Rao, and Q. Zhao

J. Appl. Phys. 98, 043111 (2005); http://dx.doi.org/10.1063/1.2008389 (6 pages) | Cited 5 times

Online Publication Date: 25 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This work presents an investigation of the photoemission properties of niobium. The quantum efficiency (QE) of niobium cathodes was measured for a variety of surface preparations relevant to the operation of a superconducting injector. The dependence of the QE on wavelength, applied field, and laser cleaning energy was determined. The three-step model of photoemission was adapted to fit the observed emission behavior. QE values of 6.5×10−5 for 266 nm, 1.0×10−4 for 248 nm, and 2.8×10−4 for 193 nm were observed with a bias field of 1 MV/m.
Show PACS
81.05.Bx Metals, semimetals, and alloys
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.65.Cf Surface cleaning, etching, patterning
85.60.Ha Photomultipliers; phototubes and photocathodes
42.62.-b Laser applications
85.25.-j Superconducting devices

Polarization-independent and fast-response phase modulation using a normal-mode polymer-stabilized cholesteric texture

Yi-Hsin Lin, Hongwen Ren, Yun-Hsing Fan, Yung-Hsun Wu, and Shin-Tson Wu

J. Appl. Phys. 98, 043112 (2005); http://dx.doi.org/10.1063/1.2037191 (4 pages) | Cited 10 times

Online Publication Date: 25 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fast-response, polarization-independent, and hysteresis-free phase-only modulation using a normal-mode polymer-stabilized cholesteric texture (PSCT) is demonstrated. Although the remaining phase change in the high-voltage regime is small, it is still useful for making microdevices. Polarization-independent tunable-focus microlens arrays using such a PSCT are demonstrated.
Show PACS
42.79.Hp Optical processors, correlators, and modulators
42.70.Df Liquid crystals
61.30.Vx Polymer liquid crystals
42.79.Kr Display devices, liquid-crystal devices
42.79.Bh Lenses, prisms and mirrors

Piezo-induced sensitivity enhancements in electro-optic field sensors

A. Garzarella, S. B. Qadri, Terence J. Wieting, and Dong Ho Wu

J. Appl. Phys. 98, 043113 (2005); http://dx.doi.org/10.1063/1.2030414 (6 pages) | Cited 9 times

Online Publication Date: 25 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Responsivity measurements are reported for LiNbO3 electro-optic field sensors operated under applied electric fields at ac frequencies in the vicinity of the acoustic resonance values of the crystals. At these frequencies, piezoelectric effects dominate the sensor output. These resonance effects are well known and commonly considered parasitic. However, we propose their use as a sensitivity-enhancing mechanism for electric-field detection. We have found that our field sensors operated within these resonances responded linearly with the applied field strength and exhibited increases in their intrinsic sensitivities as high as 350 times larger than their normal, electro-optic values. Our modeling of the data suggests that the sensitivity enhancements are produced by the interplay between photoelastic shifts in the refractive indices and the physical vibration modes of the crystals. Aside from narrowband applications, these resonant enhancements can be exploited with fields at frequencies well beyond the narrow bandwidth of the acoustic resonance, if the fields are properly modulated.
Show PACS
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Hp Optical processors, correlators, and modulators

Propagation properties of planar Bragg waveguides studied by an analytical Bloch-mode method

Hong-Yi Sang, Zhi-Yuan Li, and Ben-Yuan Gu

J. Appl. Phys. 98, 043114 (2005); http://dx.doi.org/10.1063/1.2030416 (8 pages) | Cited 4 times

Online Publication Date: 26 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We use an analytic Bloch-mode approach to investigate one-dimensional planar Bragg waveguides (PBWGs) with an air- or a glass-core layer sandwiched within two symmetric Bragg gratings formed by alternate arrays of air and glass layers. The calculation results show that there exist simultaneously two kinds of guided modes as the gap-guided modes resulting from the photonic band-gap effect and the index-guided modes formed by the total internal reflection effect. We calculate the electromagnetic (EM)-field distributions of these guided modes with different parallel wave vectors and find remarkably different EM-field profiles between the index-guided modes and the gap-guided modes. In order to explore the propagation properties of the PBWGs, we analyze the group velocity and the group-velocity dispersion of different types of guided modes. The results show that the guided mode properties are significantly influenced by the core material as well as the cladding structure. The analytic Bloch-mode approach can help to investigate and design the PBWGs in a simple, efficient, and accurate manner.
Show PACS
42.79.Gn Optical waveguides and couplers
42.25.Bs Wave propagation, transmission and absorption
42.82.Et Waveguides, couplers, and arrays
42.79.Dj Gratings
42.70.Qs Photonic bandgap materials
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close