Virtual Journal of Lasers

2.70 [mu] m emission Er:Cr:YSGG laser with LiNbO3 Pockels cell

Mon, 17 Nov 2008 00:46:00 -0800

In this study, an electro-optically Q-switched 2.70 [mu] m emission Er:Cr:YSGG laser with a LiNbO3 Pockels cell is investigated and compared with a FTIR Q-switched scheme. It can obtain nanosecond pulse at a low voltage of 1.4 kV using a CaF2 polarizer and a LiNbO3 crystal with Brewster's angle cut ends. Wavelength generation of 2.70 [mu] m was possible with a Fresnel loss at a rear mirror with a dielectric dichroic coating. The maximum output energy of 21.5 mJ (at 1 Hz repetition rate) was achieved in TEM21 mode using the output coupler with a reflectivity of 55% at 2.70 [mu] m. The generated maximum pulse energy and pulse width were 13.3 mJ and 159 ns in TEM00 mode, respectively. The pulse width was shorter than 1.3 [mu] s of the FTIR Q-switched scheme. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

High power all-solid-state fourth harmonic generation of 266 nm at the pulse repetition rate of 100 kHz

Mon, 17 Nov 2008 00:46:00 -0800

14.8 W UV laser at 266 nm was reported with the extra cavity frequency quartered configuration. The fundamental frequency IR source is a high-power high-beam-quality acousticoptic Q-switched Nd:YVO4 master-oscillator-power-amplifier laser. The type-I phase-matched LBO and type-I phase-matched BBO crystals were used as the extra-cavity frequency doubled and quartered crystal respectively. 14.8 W UV laser of 266 nm was obtained at the pulse repetition rate of 100 kHz with the conversion efficiency of 18.3% from green to UV, and the pulse duration of the UV laser was 10 ns corresponding to the pulse peak power of 14.8 kW. At 150 kHz, 11.5 W power output was obtained. The highest peak power of 21 kW was also achieved at 80 kHz with the average output power of 14.5 W. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

Threshold reduction induced by silica nanoparticledispersed active layer in diode-pumped microcavity dye laser

Mon, 17 Nov 2008 00:46:00 -0800

We report a vertical microcavity dye laser consisting of a polymeric active random layer doped with silica nanoparticles whose diameters are approximately 100 nm. Pumped by an InGaN-based blue-violet laser diode with pulse duration of 3 ns, single mode laser oscillation was obtained at a wavelength of 530 nm. The threshold pump power decreased from 70 mW/pulse to 49 mW/pulse by adding nanoparticles to the active layer. We found an optimum particle density of 2 × 1013 cm-3 by measuring threshold pump power to change depending on the particle density in the activity layer. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

Laser annealing characteristics of multiple bulk defect populations within DKDP crystals

Tue, 18 Nov 2008 05:30:39 -0800

Paul DeMange, Christopher W. Carr, Raluca A. Negres, Harry B. Radousky, and Stavros G. Demos
Laser annealing by pre-exposure to subdamage threshold laser pulses is a well-established method to increase the damage performance of bulk KHPO and KDHPO nonlinear optical materials. The origin of laser-induced damage is believed to be localized absorption by a defect structure, either a light-abso ... [J. Appl. Phys. 104, 103103 (2008)] published Mon Nov 17, 2008.

Comparison of resonant-phonon-assisted terahertz quantum-cascade lasers with one-well injector and three-well module

Tue, 18 Nov 2008 05:30:39 -0800

H. Li, J. C. Cao, Z. Y. Tan, and S. L. Feng
The authors compare resonant-phonon-assisted terahertz quantum-cascade lasers with different active region designs, i.e., one-well injector and three-well module, using an ensemble Monte Carlo method. Carrier transport under injection anticrossing, parasitic anticrossing, and collection anticrossing ... [J. Appl. Phys. 104, 103101 (2008)] published Mon Nov 17, 2008.

The dissociation of excitons at indium tin oxide-copper phthalocyanine interface in organic solar cells

Tue, 18 Nov 2008 05:30:39 -0800

X. Y. Sun, Q. L. Song, M. L. Wang, X. M. Ding, X. Y. Hou et al.
Exciton dissociation process at indium tin oxide (ITO)/copper phthalocyanine (CuPc) interface of ITO/CuPc(370 nm)/Al is studied by transient photovoltage method. A negative-to-positive change in the polarity of photovoltage upon pulsed laser irradiation is observed in CuPc thin film. The polarity ch ... [J. Appl. Phys. 104, 103702 (2008)] published Mon Nov 17, 2008.

Microwave dielectric and Raman scattering studies on bismuth zinc niobate thin films

Tue, 18 Nov 2008 05:30:39 -0800

K. Sudheendran, K. C. James Raju, Manoj K. Singh, and Ram S. Katiyar
Bismuth zinc niobate (BiZnNbO) thin films were deposited on fused silica substrates by pulsed laser deposition. Its phase composition and microstructure were characterized by x-ray diffraction and atomic force microscopy. The as deposited films were amorphous and all of them were crystallized after ... [J. Appl. Phys. 104, 104104 (2008)] published Mon Nov 17, 2008.

Controlling the orientation of polar molecules in a rovibrationally selective manner with an infrared laser pulse and a delayed half-cycle pulse

Sun, 16 Nov 2008 16:00:00 -0800

Author(s): Chuan-Cun Shu (束传存), Kai-Jun Yuan (元凯军), Wen-Hui Hu (胡文辉), Jing Yang (杨静), and Shu-Lin Cong (丛书林)
We propose a scenario used for controlling molecular orientation with an infrared laser pulse and a delayed half-cycle pulse, with LiH molecules as an example. The infrared laser pulse excites the molecules in a thermally initial state to a specific rovibrational state, and the half-cycle pulse orie...
[Phys. Rev. A 78, 055401] Published Mon Nov 17, 2008

Raman coupling of Zeeman sublevels in an alkali-metal Bose-Einstein condensate

Sun, 16 Nov 2008 16:00:00 -0800

Author(s): K. C. Wright, L. S. Leslie, and N. P. Bigelow
We investigate amplitude and phase control of the components of the spinor order parameter of a ^{87} Rb Bose-Einstein condensate. By modeling the interaction of the multilevel atomic system with a pair of Raman-detuned laser pulses, we show that it is possible to construct a pulse-sequence protocol...
[Phys. Rev. A 78, 053412] Published Mon Nov 17, 2008

Polarization separator created by a filament in air

Mon, 17 Nov 2008 21:00:00 -0800

Yanping Chen, Claude Marceau, Francis Théberge, Marc Châteauneuf, Jacques Dubois, See Leang Chin
We demonstrate that a femtosecond laser pulse-induced filament can act as a “polarization separator” for a copropagating femtosecond probe pulse. The probe component with polarization parallel to the pump is guided along the propagation axis through the cross interactions with the ... [Opt. Lett. 33, 2731-2733 (2008)]

Interface solitons in two-dimensional photonic lattices

Tue, 18 Nov 2008 21:00:00 -0800

Mario I. Molina, Yuri S. Kivshar
We analyze localization of light at the interfaces separating square and hexagonal photonic lattices, as recently realized experimentally for two-dimensional laser-written waveguides in silica glass with self-focusing nonlinearity [Opt. Lett.33, 663 (2008)]. We find the conditions for the existence ... [Opt. Lett. 33, 2761-2763 (2008)]

High-speed structured planar laser illumination for contrast improvement of two-phase flow images

Tue, 18 Nov 2008 21:00:00 -0800

E. Kristensson, E. Berrocal, M. Richter, S.-G. Pettersson, M. Aldén
A high-speed method to remove blurring effects caused by multiple scattering in planar laser images of two-phase flows is demonstrated. The technique is based on structured illumination and is for the first time to our knowledge applied on a dynamic medium. As structured illumination requires three ... [Opt. Lett. 33, 2752-2754 (2008)]

Serrodyne optical frequency shifting for heterodyne self-mixing in a distributed-feedback fiber laser

Tue, 18 Nov 2008 21:00:00 -0800

Mathieu Laroche, Célia Bartolacci, Guillaume Lesueur, Hervé Gilles, Sylvain Girard
We describe an all-fiberized coherent detection system at 1.55 μm using heterodyne self-mixing modulation in a distributed-feedback fiber laser. Frequency shifting of the optical feedback is based on serrodyne phase modulation with an integrated electro-optic modulator, which is a significant ... [Opt. Lett. 33, 2746-2748 (2008)]

Sensitive detection of ammonia and ethylene with a pulsed quantum cascade laser using intra and interpulse spectroscopic techniques

Sun, 16 Nov 2008 03:31:38 -0800

Abstract Spectroscopic concentration measurements of ammonia and ethylene were done with a pulsed, distributed feedback (DFB) quantum cascade (QC) laser centered at 970 cm⁻¹. An astigmatic Herriot cell with 150 m path length was employed, and we compare the results from experiments using inter- and intrapulse techniques, respectively. The measurements include the detection of ammonia in breath with these methodologies. In the interpulse technique, the laser was excited with short current pulses (5–10 ns), and the pulse amplitude was modulated with an external current ramp resulting in a ∼0.3 cm⁻¹ frequency scan. A standard amplitude demodulation technique was implemented for extracting the absorption line, thus avoiding the need for a fast digitizer or a gated integrator. In the intrapulse technique, a linear frequency down-chirp is used for sweeping across the absorption line.

Molecular relaxations in mixtures of O2 with CO2 observed on laser-induced gratings

Sun, 16 Nov 2008 03:31:38 -0800

Abstract Laser-induced gratings in mixtures of O₂ with CO₂ were formed by excitation of the O₂ molecules to the singlet state b ¹ Σ _g⁺(v′=0). Density changes from heat release and from electrostriction, and variation of electric polarizability by excitation of molecules contribute to the grating. For modeling the relaxation of the excited O₂ molecules, a three-step process is assumed: Fast heat release with respect to the rotational states first, then medium fast electronic de-activation with excitation of vibrational states of the O₂ and CO₂ molecules, and then the final slow heat release processes. The observed temporal evolution of the diffraction efficiency of the grating agrees rather well with modeling. Average rates of the final relaxations and the value of the polarizability of the singlet state b ¹ Σ _g⁺(v′=0) are determined in this way.

Noise caused by a finite extinction ratio of the light modulator in CW cavity ring-down spectroscopy

Sun, 16 Nov 2008 03:31:48 -0800

Abstract A model is presented for the effect of a finite extinction ratio of the light modulator used in continuous wave cavity ring-down spectroscopy (CW-CRDS) experiments. We present a simple analytical expression for the minimum isolation required to prevent a significant increase in the fluctuations of the cavity decay rate, which determine the sensitivity of the method. We also present systematic measurements of the signal to noise in CW-CRDS as a function of the effective isolation of the light modulator, and excellent agreement with the model is found.

Content Type Journal Article
DOI 10.1007/s00340-008-3293-y
Authors
- H. Huang, University of Virginia Department of Chemistry Charlottesville VA 22904-4319 USA
- K. K.
  
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Laser desorption studies using laser-induced fluorescence of large aromatic molecules

Sun, 16 Nov 2008 03:31:44 -0800

Abstract Pulsed laser desorption of non-volatile organic dye molecules paraterphenyl and tetra-t-butyl-p-quinquephenyl (QUI) was studied using gas phase ultraviolet laser induced fluorescence, following heating of a steel substrate by a pulsed 1.06-µm Nd:YAG laser. The fluorescence signal intensity is linear in concentration up to at least 30 monolayers and shows infrared power threshold behavior, as expected for evaporation, at ∼0.2 J/cm². Similar signal levels were also observed in air, with 532-nm heating, and using other metallic or dark black surfaces.

Content Type Journal Article
DOI 10.1007/s00340-008-3295-9
Authors
- G. P. Smith, SRI International Molecular Physics Laboratory Menlo Park CA 94025 USA
- B. Krancevic, SRI International Molecular Physics Laboratory Menlo Park CA 94025 USA
- D. L. Huestis, SRI International Molecular Physics Laboratory Menlo Park CA 94025 USA
- H.
  
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Diode-pumped laser with Yb:YAG single-crystal fiber grown by the micro-pulling down technique

Sun, 16 Nov 2008 03:31:47 -0800

Abstract Laser emission obtained from an Yb:YAG single-crystal fiber directly grown by the micro-pulling down technique is demonstrated for the first time. We achieved 11.2 W of continuous wave (CW) output power at 1031 nm for 55 W of incident pump power at 940 nm. In the Q-switched regime, we obtained pulses as short as 17 ns, for an average power of 2.3 W at 2 kHz corresponding to an energy of 1.15 mJ. In both cases, the M ² factor was 2.5. This single-crystal fiber showed performance similar to a standard rod elaborated by the Czochralski method. The potential of Yb³⁺-doped single-crystal fibers is presented for scalable high-average and high-peak-power laser systems.

Content Type Journal Article
DOI 10.1007/s00340-008-3288-8
Authors
- D.
  
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3.5-μm high-resolution gas sensing employing a LiNbO3 QPM-DFG waveguide module

Sun, 16 Nov 2008 03:31:47 -0800

Abstract Diode laser technology coupled with a wavelength-conversion unit to produce mid-infrared narrow bandwidth laser light applicable to trace-gas detection and with the potential for high-resolution spectroscopy is described. Quasi-phase-matched difference-frequency generation (QPM-DFG) in a compact and fibre-coupled periodically poled lithium niobate (PPLN) waveguide module mixing 1063 and 1525-nm radiations has been adopted for generating 34 μW of 3.5-μm wavelength laser light. Optical detection methods, including sensitive wavelength modulation spectroscopy and a rapid wavelength chirp technique, have been employed with a single-pass cell to investigate methane and formaldehyde absorption profiles around 2855 cm⁻¹, as proof of principle experiments for high sensitivity and resolution spectroscopy on atmospherically important molecules.

Laser-induced point-defect reaction in proton-irradiated SiC

Sun, 16 Nov 2008 03:31:46 -0800

Abstract The defects produced in 4H-SiC epitaxial layers by irradiation with 200-keV H⁺ were characterized by low-temperature photoluminescence. These defects induce sharp luminescent lines, the so-called alphabet lines. Their intensity shows an evolution under UV-laser irradiation not previously observed. By monitoring the change in the resulting photoluminescence spectra versus time, we distinguish two original ‘families’ of peaks called PB₁ and PB₂. They display a different, and opposite, behaviour with laser irradiation but they are strongly correlated. In particular, the recovering rate of the PB₁ family and the growth rate of the PB₂ family are the same, indicating a structural rearrangement of defects.

Content Type Journal Article
Category Rapid communication
DOI 10.1007/s00340-008-3302-1
Authors
- M. Zimbone, Catania University Physics Department Via S.
  
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Thermal lens effects in an Er3+:YAG laser with crystalline fiber geometry

Sun, 16 Nov 2008 03:31:46 -0800

Abstract A resonantly diode-pumped high-power continuous-wave Er³⁺:YAG laser with a crystalline fiber geometry based on total-internal-reflection pump guiding is reported. Up to 9.4 W of output power could be generated and a slope efficiency of 46.8% was achieved. Intrinsic efficiencies reached up to 48.8% and an optimum outcoupling of ∼20% was found. A strong thermal lens was observed and cavity stability and hysteresis effects were studied.

Content Type Journal Article
DOI 10.1007/s00340-008-3292-z
Authors
- M.
  
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Thermal effects in singly resonant continuous-wave optical parametric oscillators

Sun, 16 Nov 2008 03:31:47 -0800

Abstract Stability and tuning characteristics of continuous-wave optical parametric oscillators (CW OPOs) are affected by various thermal effects arising from optical absorption in nonlinear crystals. In this paper, we present an experimental study of such effects in a singly resonant CW OPO. The OPO operates in the 3-μm mid-infrared region and it is based on a MgO-doped periodically poled lithium niobate crystal. We focus our study on two thermally induced phenomena that have been recently reported to exist in singly resonant CW OPOs: optical bi-stability and thermal self-locking. Thermal self-locking effect, which is known to alter the stability and tuning properties of doubly and triply resonant CW OPOs, is shown to be also of importance in singly resonant OPOs. We report the stability and tuning characteristics of a thermally loaded OPO and discuss a simple temperature-tuning method that can be used to scan the OPO idler frequency continuously over several THz.

Aging effect on blue luminescent silicon nanocrystals prepared by pulsed laser ablation of silicon wafer in de-ionized water

Sun, 16 Nov 2008 03:31:42 -0800

Abstract Blue luminescent colloidal silicon nanocrystals (Si-ncs) were synthesized at room temperature by nanosecond pulsed laser ablation of a single-crystal silicon target in de-ionized water. Irregular Si-nc fragments obtained by laser ablation are stabilized into regularly shaped, spherical, and well-separated aggregates during the aging process in water. Aging in de-ionized water for several weeks improved the photoluminescence (PL) intensity. At least two weeks of aging are necessary for observation of broad blue room temperature PL with a maximum centered at 420 nm. Detailed structural analysis revealed that agglomerates after aging for several months contain Si-ncs with irregular shape smaller than the quantum confinement limit (<5 nm). These blue luminescent Si-ncs dispersed in de-ionized water exhibited a PL decay time of 6 ns, which is much faster than that of Si-ncs prepared in traditional ways (usually on the order of microseconds).

Continuous-wave cavity-ringdown detection of stimulated Raman gain spectra

Sun, 16 Nov 2008 03:31:39 -0800

Abstract Cavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuous-wave (cw) stimulated Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser light at ∼1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼1064.4 nm. This approach is used to measure cw SRG spectra of the ν ₁ fundamental rovibrational Raman band of methane gas at ∼2916.5 cm⁻¹. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals.

Polarized spectral properties of Pr3+ ions in NaGd(MO4)2 crystal

Sun, 16 Nov 2008 03:31:39 -0800

Abstract A Pr³⁺:NaGd(MoO₄)₂ single crystal has been grown by the Czochralski method. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of the crystal were measured at room temperature. The Judd–Ofelt intensity parameters Ω_t,q (t=2,4,6) and the spectroscopic parameters related to the ³ P ₀ and ¹ D ₂ multiplets were obtained and analyzed. The decay mechanisms for the ³ P ₀ and ¹ D ₂ multiplets were also discussed.

Content Type Journal Article
DOI 10.1007/s00340-008-3289-7
Authors
- W. J. Guo, Chinese Academy of Sciences Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter Fuzhou Fujian 350002 China
- Y. F.
  
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Frequency stabilization and output power undulations of diode lasers with feedback by volume holographic gratings

Sun, 16 Nov 2008 03:31:48 -0800

Abstract The mode-hop behavior and the power characteristics of a laser diode with wavelength-selective optical feedback are experimentally investigated. The feedback is provided by external volume holographic gratings, also called ‘Bragg mirrors’, at normal incidence. We demonstrate that a Bragg mirror forces a laser diode to operate only within a narrow wavelength range, and that the emission wavelength of the laser diode is stabilized against variations of the injection current. Moreover, we present periodic undulations of the power characteristics of the laser, depending on the driving current. They can be qualitatively explained with a simple model which takes into account that the threshold gain in the laser system strongly depends on the wavelength.

Content Type Journal Article
DOI 10.1007/s00340-008-3290-1
Authors
- F. Kroeger, University of Bonn Institute of Physics Wegelerstr. 8 53115 Bonn Germany
- I.
  
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Feasibility of a nitrogen-recombination soft-x-ray laser using capillary discharge Z pinch

Sun, 16 Nov 2008 16:00:00 -0800

Author(s): N. S. Kampel, A. Rikanati, I. Be’ery, A. Ben-Kish, A. Fisher, and A. Ron
Capillary discharge Z pinches have been shown to be efficient drivers for x-ray lasers (XRLs). In this work we examine the possibility of realizing a H_{α} nitrogen recombination laser ( 3→2 transition) at λ=13.4nm , using a capillary discharge Z pinch. A pulsed power generator with 60kA peak cu...
[Phys. Rev. E 78, 056404] Published Mon Nov 17, 2008

Pulse-shaping of gain-switched pulse from multimode laser diode using fiber Sagnac interferometer

Sun, 16 Nov 2008 21:00:00 -0800

Kenji Wada, Shuji Takamatsu, Hideyuki Watanebe, Tetsuya Matsuyama, Hiromichi Horinaka
We propose a pulse-tail elimination and pulse shortening method using an optical interferometer, which is effective for picosecond chirped pulses from gain-switched multimode laser diodes. In a numerical simulation, when the delay distance between a chirped pulse and its replica in an optical ... [Opt. Express 16, 19872-19881 (2008)]

Thermal characteristics of an end-pumped high-power ytterbium-sensitized erbium-doped fiber laser under natural convection

Sun, 16 Nov 2008 21:00:00 -0800

Y. Jeong, S. Baek, P. Dupriez, J.-N. Maran, J. K. Sahu, J. Nilsson, B. Lee
We investigate the thermal characteristics of a polymer-clad fiber laser under natural convection when it is strongly pumped up to the damage
point of the fiber. For this, we utilize a temperature sensing technique based on a fiber Bragg grating sensor array. We have measured the longitudinal ... [Opt. Express 16, 19865-19871 (2008)]

Investigation of amplification process on the third Stokes line of H_2 under ultraviolet laser irradiation

Tue, 18 Nov 2008 21:00:00 -0800

Mohammed A. Gondal, Abdulkader Dastageer
An amplification process was investigated in the third stimulated Raman scattering (SRS) line of H_2 excited with a 266 nm laser beam generated from the fourth harmonic of a Nd:YAG laser. The unexpected intensity enhancement observed at the third Stokes SRS line around 397.8 nm is attributed to the ... [Appl. Opt. 47, 6243-6250 (2008)]

Single shot linear detection of 0.01–10 THz electromagnetic fields

Wed, 12 Nov 2008 14:20:13 -0800

Abstract We demonstrate widely tunable and broadband single shot electro-optic detection of THz waveforms with a linear response to the electric field over a wide range. The THz field is encoded to the temporally dispersed spectrum of a supercontinuum whose polarization state is analyzed in balanced detection. With the probe bandwidth corresponding to a Fourier Transform-limited duration below 5 fs, the time window can easily be adjusted in the fs to 100 ps range to be several times longer than the THz pulse without signal distortion. Thanks to a laser fluctuation-free design, the phase retardation (Γ) is measured under shot noise limited conditions with a rms noise below 0.005 over the whole spectral (i.e., temporal) window. The method allows the direct determination of the absolute amplitude of the THz field for the first time in a single shot EO-experiment. The performance of the diagnostic can be achieved with state-of-the-art fs to ps laser sources.

Ultra-narrow-linewidth continuous-wave THz sources based on multiplier chains

Wed, 12 Nov 2008 14:20:13 -0800

Abstract We demonstrate two different sources at 1.3 THz based on multiplier chains (72nd harmonic generation), which exhibit linewidths at the level of 2×10⁻¹² in relative units. The multiplication processes are shown not to contribute significantly to this linewidth. The phase noise of one of the sources and the fractional power in the carrier (76%) were determined. The application of these sources as references for quantum cascade THz lasers and for spectroscopy of ultracold molecules is suggested. Thus, rotational spectroscopy with few Hz resolution at 1.3 THz is possible with the present easy-to-use sources. An approach for reducing the linewidth by a factor on the order of 10³ to the 1×10⁻¹⁵ level using optical technology is proposed.

Content Type Journal Article
DOI 10.1007/s00340-008-3279-9
Authors
- S.
  
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Efficient generation of orange light in a quasi-periodically poled LiTaO3 crystal

Thu, 13 Nov 2008 07:45:13 -0800

Abstract We present an approach to generating a tunable orange laser from 0.601 to 0.604 μm based on a quasi-periodically poled superlattice in LiTaO₃ and a Q-switched 1.064 μm Nd:YVO₄ laser as pump. The orange laser was generated in a cavity by a parametric process cascaded by a frequency mixing with a maximum output of 310 mW using 15 W pump power.

Content Type Journal Article
Category Rapid communication
DOI 10.1007/s00340-008-3272-3
Authors
- S. D. Pan, Nanjing University National Laboratory of Solid State Microstructures Nanjing 210093 People’s Republic of China
- X. Q. Yu, Nanjing University National Laboratory of Solid State Microstructures Nanjing 210093 People’s Republic of China
- Z. Yan, Nanjing University National Laboratory of Solid State Microstructures Nanjing 210093 People’s Republic of China
- Y.
  
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Laser Channeling of Bethe-Heitler Pairs

Thu, 13 Nov 2008 16:00:00 -0800

Author(s): Erik Lötstedt, Ulrich D. Jentschura, and Christoph H. Keitel
Electron-positron pair creation is analyzed for an arrangement involving three external fields: a high-frequency gamma photon, the Coulomb field of a nucleus, and a strong laser wave. The frequency of the incoming gamma photon is assumed to be larger than the threshold for pair production in the abs...
[Phys. Rev. Lett. 101, 203001] Published Fri Nov 14, 2008

Evolution from a Molecular Rydberg Gas to an Ultracold Plasma in a Seeded Supersonic Expansion of NO

Thu, 13 Nov 2008 16:00:00 -0800

Author(s): J. P. Morrison, C. J. Rennick, J. S. Keller, and E. R. Grant
We report the spontaneous formation of a plasma from a gas of cold Rydberg molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1 K in a seeded supersonic molecular beam, to single Rydberg states extending as deep as 80 cm^{-1} below the lowest ionization threshold. The...
[Phys. Rev. Lett. 101, 205005] Published Fri Nov 14, 2008

Spatiotemporal moving focus of long femtosecond-laser filaments in air

Thu, 13 Nov 2008 16:00:00 -0800

Author(s): Ting-Ting Xi, Xin Lu, and Jie Zhang
The characteristics of filaments formed by femtosecond-laser pulses freely propagating in air are different from those of filaments generated with a focal lens. A scheme combining (2D+1) modeling of the nonlinear Schrödinger equation and ray-tracing method is proposed to provide a fast estimate of ...

[Phys. Rev. E 78, 055401] Published Fri Nov 14, 2008

Distance measurements by combined method based on a femtosecond pulse laser

Thu, 13 Nov 2008 21:00:00 -0800

Ki-Nam Joo, Yunseok Kim, Seung-Woo Kim
We describe a combined interferometric scheme that enables absolute distance measurements using a femtosecond pulse laser. This method is combined with synthetic wavelength interferometry (SWI), time of flight (TOF) and spectrally-resolved interferometry (SRI) using the optical comb of femtosecond ... [Opt. Express 16, 19799-19806 (2008)]

10-Gbps, 1-μm waveband photonic transmission with a harmonically mode-locked semiconductor laser

Thu, 13 Nov 2008 21:00:00 -0800

Naokatsu Yamamoto, Hideyuki Sotobayashi, Kouichi Akahane, Masahiro Tsuchiya, Keijiro Takashima, Hiroyuki Yokoyama
To open up a 1-μm waveband for photonic transport systems, we developed a hybrid and harmonically mode-locked semiconductor laser (MLL) that can transmit return-to-zero (RZ) optical signals at data rates on the order of gigabits per second. A single-mode hole-assisted fiber (HAF) was also ... [Opt. Express 16, 19836-19843 (2008)]

Electrically switchable emission in terahertz quantum cascade lasers

Thu, 13 Nov 2008 21:00:00 -0800

Joshua R. Freeman, Owen P. Marshall, Harvey E. Beere, David A. Ritchie
Electrically switchable emission in a terahertz quantum cascade laser is demonstrated. Two active region designs are incorporated into the same waveguide, forming a heterogeneous cascade that lases at frequencies around 2.6 THz and 3.0 THz. We find that the position of the active regions within the ... [Opt. Express 16, 19830-19835 (2008)]

In-line holographic imaging and electron density extraction of ultrafast ionized air filaments

Thu, 13 Nov 2008 21:00:00 -0800

George Rodriguez, Anthony R. Valenzuela, Balakishore Yellampalle, Mark J. Schmitt, Ki-Yong Kim
In-line spatial holographic methods are used to image the optical diffraction patterns of ultrafast laser produced plasma filaments in air. Using femtosecond laser pump-probe methods the plasma filament is produced and subsequently probed by a time-delayed probe beam traversing the filament at a ... [J. Opt. Soc. Am. B 25, 1988-1997 (2008)]

Widely tunable laterally coupled distributed feedback laser diodes for multispecies gas analysis based on InAs/InGaAs quantum-dash material

Sun, 16 Nov 2008 21:00:00 -0800

W. Zeller, M. Legge, J. Seufert, R. Werner, M. Fischer, J. Koeth
Applying the concept of binary superimposed gratings, widely tunable single-mode laser diodes suitable for multispecies gas detection in the 1.8 μm wavelength range could be manufactured on InAs/InGaAs quantum dash-in-a-well material. A discrete wavelength tuning range of 21 nm as well as ... [Appl. Opt. 48, B51-B56 (2009)]

Pulse compression in a longitudinally inhomogeneous fiber

Wed, 12 Nov 2008 14:27:33 -0800

Abstract A single-mode fiber with a linear or sinusoidal variation in the group-velocity dispersion is fabricated. The nonreciprocal
effects and pulse compression due to the longitudinal oscillations of the fiber dispersion are experimentally demonstrated.
The periodic modulation of the dispersion can be used to control the pulse dynamics.

Mathematical simulation of the femtosecond-laser inscription of optical waveguides

Wed, 12 Nov 2008 14:27:33 -0800

Abstract Based on the hierarchy of mathematical models with regard to parallel algorithms and effective systems, the interaction of
a femtosecond-laser pulse with a transparent dielectric medium (fiber-optic glass) is numerically simulated. The features
of this interaction are studied for the initial Gaussian and ring distributions of the laser beam. The critical powers at
which a local collapse of the beam takes place are determined for the Schrödinger equation. A comparison of the results obtained
using various models is presented.

Fiber supercontinuum generators with dynamically controlled parameters

Wed, 12 Nov 2008 14:27:33 -0800

Abstract Various methods to dynamically control the supercontinuum (SC) parameters are analyzed. The possibility of variations in the
SC power spectral density due to variations in the wavelength and pulse repetition rate of the pumping laser is considered.
An increase in the SC coherence owing to the optimization of the pumppulse frequency modulation is discussed. A variation
in the repetition rate of the SC pulses generated in the scheme with the two-wavelength pumping due to a variation in the
frequency difference is studied.

Fiber supercontinuum generator with wavelength-tunable pumping