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Selected Topics in Quantum Electronics, IEEE Journal of

Issue 6 • Date Nov.-Dec. 2004

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Displaying Results 1 - 25 of 31
  • Table of contents

    Page(s): c1 - c4
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  • IEEE Journal of Selected Topics in Quantum Electronics publication information

    Page(s): c2
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  • Introduction to the Issue on Short Wavelength and EUV Lasers

    Page(s): 1241 - 1243
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  • High-power CW deep-UV coherent light sources around 200 nm based on external resonant sum-frequency mixing

    Page(s): 1244 - 1251
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    We report pure continuous-wave (CW) high-power (>100 mW) deep-ultraviolet (DUV) light sources emitting around 200-nm spectral region based on singly resonant sum-frequency mixing (SRSFM). Efficient DUV generation is made possible by use of a Brewster-cut CsLiB6O10 (CLBO) crystal near noncritically phase-matched (NCPM) condition for the SFM of 1-μm output of neodymium lasers. The CW radiation of fifth-harmonic wavelength of a neodymium laser at 213 nm was generated by the SFM of enhanced 1064-nm radiation with single-passing 266-nm radiation produced by external-resonant frequency doubling of a 532-nm green laser. With 1.8 W of 266-nm radiation incident upon a CLBO crystal, as much as 180 mW of CW 213-nm power has been produced. The sub-200-nm CW radiation with 140-mW power has also been achieved by SFM of 1064 nm with 244-nm radiation from a frequency-doubled Argon-ion laser in the CLBO crystal operated near the NCPM condition. View full abstract»

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  • Development of a continuous-wave, deep-ultraviolet, and single-frequency coherent light source-challenges toward laser cooling of silicon

    Page(s): 1252 - 1258
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    Laser cooling techniques of silicon may be a powerful tool to create a new silicon road map. In the first step, to realize the laser cooling of neutral silicon atoms highly efficient frequency conversions are conducted to obtain a deep-ultraviolet single-mode coherent light using two-stage external cavities. The 154-mW power at around 252 nm is obtained with a conversion efficiency of more than 8% by doubly resonant sum-frequency mixing of 373-nm light from the first-stage conversion and 780-nm light from a single-mode Ti:sapphire laser. This paper reviews a series of challenges for taking possession of the spatial design of nuclear spins of the family of stable isotopes with laser cooling of silicon. View full abstract»

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  • Optical parametric amplification of femtosecond ultraviolet laser pulses

    Page(s): 1259 - 1267
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    Broad-band amplification of femtosecond laser pulses using the scheme of noncollinear optical chirped pulse parametric amplification is modeled. The effect of two-photon absorption at the pump wavelength was also taken into account. The signal pulses range from 220 to 410 nm with pump pulses at 267, 248, and 213 nm. The best four crystals chosen among 12 possible ones are BBO, KDP, CLBO, and LB4. In an experiment, 30-fs laser pulses at 400 nm were amplified in a BBO crystal pumped by 267 nm pulses, exhibiting a single pass gain of 3550. The gain was found spectrally flat within the available 17-nm bandwidth of the signal pulse. View full abstract»

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  • Portable ultrafast blue light sources designed with frequency doubling in KTP and KNbO3

    Page(s): 1268 - 1276
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    We demonstrate an effective means of achieving compact, truly portable, and entirely self-contained ultrafast blue light sources. Using a variety of nonlinear media to achieve simple second-harmonic generation of a femtosecond Cr:LiSAF laser, we investigate the relative merits of aperiodically poled bulk and waveguide nonlinear crystals in comparison to periodically poled structures. Such a compact and convenient source of ultrashort laser pulses in the blue spectral region could be of great interest for on-site applications spanning a host of disciplines, such as biomedical imaging, optical micromanipulation, and high-resolution spectroscopy. View full abstract»

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  • Dislocation related issues in the degradation of GaN-based laser diodes

    Page(s): 1277 - 1286
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    We investigate degraded GaN-based laser diodes (LDs) on epitaxial lateral overgrown GaN layers in terms of dislocations. Almost all of the threading dislocations that appear in the wing regions are a-type dislocations. Their origins are the lateral extension of dislocations from the seed regions that contingently bend upwards to the episurface. Comparing short-lived LDs and long-lived LDs that have almost the same power consumption, we find that the relative levels of dislocation densities in their respective active layers are different. In the degraded LDs, neither dislocation multiplication from the threading dislocations nor any structural changes of the threading dislocations are observed. This indicates that degradation is not caused by dislocation multiplication at the active layers, which is usually observed in LDs featuring zincblende-based structures. The degradation rate is almost proportional to the square root of the aging time. Our results indicate that degradation is governed by a diffusion process, and a detailed degradation mechanism is proposed. View full abstract»

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  • An ultra-line-narrowed high-power F2 laser for dioptric design microlithography exposure tools

    Page(s): 1287 - 1292
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    An ultra-line-narrowed high-power and high-repetition rate F2 laser system has been developed for 157-nm microlithography exposure tools with dioptric projection design. The injection locked system (ILS) consists of a low-power seed laser with ultra-narrow spectral linewidth and a high-gain amplifier. More than 25-W output power, a spectral linewidth below 0.2 pm full-width at half-maximum (FWHM) and an energy stability (3-sigma) below 10% have been obtained at a 5-kHz repetition rate and for a delay time range between the two laser stages of about 15 ns. Directly compared with a master oscillator power amplifier system, the ILS had a better performance related to output energy, energy stability, and laser pulse duration. View full abstract»

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  • Dynamics of the discharge-pumped vacuum ultraviolet Kr2* laser

    Page(s): 1293 - 1297
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    A numerical simulation code has been developed to investigate the dynamics of the discharge-pumped vacuum ultraviolet Kr2* laser. Dynamics of spectral narrowing of the laser emission down to 0.2-nm full-width at half-maximum (FWHM) was well reproduced. Small signal gain behavior as a function of the applied voltage was predicted to have a gain coefficient of 0.08 cm-1 at the applied voltage of 32 kV, which was more than twice as large as the experimentally observed maximum gain value (0.035 cm-1). The code predicted that the laser output energy could become more than 1 mJ at the applied voltage at the Kr gas pressure of 10 atm. View full abstract»

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  • High-average power EUV light source for the next-generation lithography by laser-produced plasma

    Page(s): 1298 - 1306
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    Laser-produced plasma is expected to fulfill the strict requirement as an extreme ultraviolet (EUV) light source for the next-generation lithography with 115-W average power at the intermediate focus, in terms of stability, minimum contamination, and cost of ownership. A liquid xenon micro jet is employed in our experimental facility to confirm the scalability up to the 115-W clean output power. The present experimental device is composed of a 1-kW 10-kHz 6-ns Nd:YAG laser with a xenon jet of up to 50-μm diameter of 35 m/s speed inside a vacuum chamber, combined with a xenon recirculation system. The observed EUV power is 4 W at 13.5 nm (2% bandwidth, 2πsr) from the plasma source with 0.5% stability (1 σ, 50-pulse moving average). Debris mitigation and contamination control is now studied for fast ions by time-of-flight measurements, and confinement and exhaust by a magnetic field is shown to be effective. Xe+ to Xe13+ ions were observed with Xe2+ being the main charged state. Experimental study is presented on these subjects and further parametric study on the laser wavelength and pulsewidth is reported, discussing the scalability toward the realization of a 115-W system. View full abstract»

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  • Simulation of the EUV spectrum of Xe and Sn plasmas

    Page(s): 1307 - 1314
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    Complex spectra of Xe and Sn, and their feasibility for use in the lithographic extreme ultraviolet (EUV) source, are investigated. By combining calculations of atomic data using the HULLAC code and the Whiam collisional radiative model with a simple radiative transfer model, the EUV spectrum is shown to originate from a large number of fine structure transitions. Satellite lines of 4d-4f and 4d-5p transitions from near ten times ionized states are found to make a significant contribution to the emission from an optically thick plasma. The wavelengths and transition probabilities of emission lines, charge state distribution, and level population in the plasma, as well as radiation intensity from a laser-produced plasma source have been calculated. The effect of opacity is taken into account assuming a local thermodynamic equilibrium population in the plasma. The calculated result reproduces the observed spectra both for Xe and Sn, showing applicability of the present method to the spectroscopy of hot dense plasmas. View full abstract»

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  • Generation of strong optical field in soft X-ray region by using high-order harmonics

    Page(s): 1315 - 1328
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    For further development of a variety of applications, one of the most important issues is the improvement of output harmonic energy and conversion efficiency. We review our work on the energy scaling of high-order harmonic generation based on phase-matching using a loosely focused beam. Our harmonic energy scaling method can be universally applied to harmonic generation in the neutral rare gas target. In addition, we demonstrate a new concept for spatial separation between the high-energy pump and harmonic beam to increase the available soft X-ray energy for the applications. This method is very simple and highly useful for not only high-order harmonic generation but also longitudinally pumped X-ray lasers. By combining the high-energy high harmonic source and new spatial separation method, we successfully demonstrate focusing of the soft X-ray beam with a peak intensity of 1×1014 W/cm2, which is to our knowledge the highest ever reported in the soft X-ray region. View full abstract»

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  • Bright high-order harmonic generation from long gas jets toward coherent soft X-ray applications

    Page(s): 1329 - 1338
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    We have performed the optimization of high-order harmonic brightness from long gas jets by using self-guided and chirped femtosecond laser pulses and analyzed their coherence properties. The characteristics of laser pulse propagation were analyzed both in theory and in experiments to understand the self-guiding process of laser pulses and chirp compensation mechanism. Highly efficient harmonic generation with low beam divergence and narrow bandwidth was achieved by applying these two techniques to the long gas jets. The coherence properties of the bright harmonics were examined using double-pinhole interference and spectral interference. View full abstract»

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  • Extreme nonlinear optics: attosecond photonics at short wavelengths

    Page(s): 1339 - 1350
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    We discuss coherent up-conversion of near-infrared femtosecond laser light into the extreme ultraviolet and soft-X-ray regions of the spectrum using the process of high-harmonic generation. We show that by using concepts from visible wavelength photonics, it is now possible to extend nonlinear optics well into the X-ray region of the spectrum. By manipulating the dynamics of the high harmonic process using optimized waveguide structures and pulse shapes, and on attosecond timescales, we can control the energy of the emitted photons, as well as increase the efficiency of the up-conversion process. Use of these optimized waveguide structures and pulse shapes can also improve the spatial and temporal coherence of the light. This work demonstrates that sophisticated concepts from nonlinear-optical photonics and coherent control can be applied to "extreme" nonlinear optics. View full abstract»

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  • Progress on collisionally pumped optical-field-ionization soft X-ray lasers

    Page(s): 1351 - 1362
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    We present the status of optical field ionization soft X-ray lasers. The amplifying medium is generated by focusing a high-energy circularly polarized 30-fs 10-Hz Ti: sapphire laser system in a gaseous medium. Using xenon or krypton, strong laser emission at 41.8 and 32.8 nm, respectively, has been observed. After presenting the basis of the physics, we present recent characterization of the sources as well as dramatic improvement of their performances using the waveguiding technique. View full abstract»

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  • Characteristics of a saturated 18.9-nm tabletop laser operating at 5-Hz repetition rate

    Page(s): 1363 - 1367
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    We report the characteristics of a saturated high-repetition rate Ni-like Mo laser at 18.9 nm. This table-top soft X-ray laser was pumped at a 5-Hz repetition rate by 8-ps 1-J optical laser pulses impinging at grazing incidence into a precreated Mo plasma. The variation of the laser output intensity as a function of the grazing incidence angle of the main pump beam is reported. The maximum laser output intensity was observed for an angle of 20°, at which we measured a small signal gain of 65 cm-1 and a gain-length product g×l>15. Spatial coherence measurements resulting from a Young's double-slit interference experiment show the equivalent incoherent source diameter is about 11 μm. The peak spectral brightness is estimated to be of the order of 1×1024 photons s-1 mm-2 mrad-2 within 0.01% spectral bandwidth. This type of practical, small scale, high-repetition soft X-ray laser is of interest for many applications. View full abstract»

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  • Single-pulse low-energy-driven transient inversion X-ray lasers

    Page(s): 1368 - 1372
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    The paper deals with some aspects of a new pump method applied to collisional transient X-ray lasers working with ions of the Ni-like isoelectronic sequence. Specifically, Ni-like silver is the element of main interest. It is shown that a single profiled picosecond pulse with energy of about 1 J is able to excite efficiently the active medium. A small amount of the produced plasma facilitates its heating and following excitation. Application of other available pump laser systems and the resulting medium kinetics are analyzed. Pump pulse profiling and control over the pulse shape in a laser driver are highlighted on the background of the recent development in laser driver technology. Prospects and possible development trends are discussed as well. View full abstract»

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  • Experiments and simulations of short-pulse laser-pumped extreme ultraviolet lasers

    Page(s): 1373 - 1381
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    Recent experimental work on the development of extreme ultraviolet lasers undertaken using as the pumping source the VULCAN laser at the Rutherford Appleton Laboratory is compared to detailed simulations. It is shown that short duration (∼picosecond) pumping can produce X-ray laser pulses of a few picosecond duration and that measurement of the emission from the plasma can give an estimate of the duration of the gain coefficient. The Ehybrid fluid and atomic physics code developed at the University of York is used to simulate X-ray laser gain and plasma emission. Two postprocessors to the Ehybrid code are utilized: 1) to raytrace the X-ray laser beam amplification and refraction and 2) to calculate the radiation emission in the kiloelectronvolt photon energy range. The raytracing and spectral simulations are compared, respectively, to measured X-ray laser output and the output of two diagnostics recording transverse X-ray emission. The pumping laser energy absorbed in the plasma is examined by comparing the simulations to experimental results. It is shown that at high pumping irradiance (>1015 Wcm-2), fast electrons are produced by parametric processes in the preformed long scalelength plasmas. These fast electrons do not pump the population inversion and so pumping efficiency is reduced at high irradiance. View full abstract»

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  • Demonstration of a fully spatial coherent X-ray laser at 13.9 nm

    Page(s): 1382 - 1387
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    We have recently reported the successful development of a fully coherent X-ray laser (XRL) at 13.9 nm by an oscillator-amplifier configuration with two targets. In the experiment, a seed XRL beam from the first target is injected into a plasma amplifier at the second target. The observed XRL beam has full spatial coherence and 0.2 mrad of nearly diffraction-limited divergence. In order to improve the output fluence, the amplification properties of the XRL beam have been investigated using various plasma lengths of the second amplifier target. The output energy has been improved by a factor of ten, increasing the length of the gain region to 10 mm, resulting in about 0.2 μJ of output energy. View full abstract»

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  • Generation of attosecond X-ray laser pulses

    Page(s): 1388 - 1392
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    We propose to generate as-X-ray laser pulses by beating of two or more X-ray laser lines with a frequency separation in the range of 1015 Hz. We focus on nickel-like X-ray lasers, some of which have a few almost equidistant laser gain lines with an appropriate difference frequency. It is shown that in the case of three or more lines, these can be phase-locked by means of a Langmuir wave generated in the gain medium at a suitable electron density. View full abstract»

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  • The development of X-ray free-electron lasers

    Page(s): 1393 - 1404
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    We review and discuss the theoretical and experimental work that has led to the development of short wavelength free-electron lasers operating as single pass amplifiers, starting from the spontaneous undulator radiation, in the self amplified spontaneous emission mode. This work has led to several projects to build this type of free-electron lasers operating at a wavelength of about 0.1 nm, producing coherent X-ray pulses with an unprecedented brilliance and peak power, and pulse length in the femtosecond range. One such project, the LCLS, is presently under construction and is expected to be operational in 2008. View full abstract»

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  • Tunable coherent soft X-rays

    Page(s): 1405 - 1413
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    A tunable, spatially and spectrally coherent soft X-ray undulator branchline at the Advanced Light Source (ALS) is under operation. Using the third harmonic from an 8-cm period undulator, this branch delivers coherent soft X-rays with photon energies ranging from 200 to 1000 eV. Here, the beamline layout and characterization are presented. The characterization includes measurements of available coherent photon flux as well as a series of double-pinhole experiments to measure spatial coherence in the focal plane. View full abstract»

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  • Compact high-brightness soft X-ray Cherenkov sources

    Page(s): 1414 - 1425
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    Compact narrow-band high-brightness soft X-ray sources based on the Cherenkov effect are very promising. We discuss the theoretical basis for this novel electron-accelerator-based source. We present results of experiments, which confirm the theoretical expectations and demonstrate that intense narrow-band Cherenkov light can be produced at the silicon L-edge (99.7 eV) and, in the water window, at the titanium L-edge (453 eV) and the vanadium L-edge (512 eV). On the basis of theory and experiment, we show that a compact high-brightness Cherenkov source may be realized, which fulfills the requirements for practical soft X-ray microscopy and photoelectron spectroscopy. View full abstract»

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  • Fabrication of SiO2 microlenses on silicone rubber using a vacuum-ultraviolet F2 laser

    Page(s): 1426 - 1429
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    SiO2 microlenses are fabricated on a silicone rubber surface. The silicone surface irradiated by an F2 laser beam swells and is modified to SiO2 by means of photochemical reaction. When the surface is irradiated by 6000-12000 shot laser pulses, it becomes smooth and spherical. By altering the number of pulses, it is possible to alter the microlenses' focal lengths within the range of 120-170 μm. View full abstract»

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Aims & Scope

Papers published in the IEEE Journal of Selected Topics in Quantum Electronics fall within the broad field of science and technology of quantum electronics of a device, subsystem, or system-oriented nature.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
John Cartledge
Queen's University