2011
2011
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Record 253 of
Title:Diagnostics of air plasma ablated by 1064 nm laser pulses
Author(s):Luo, Wenfeng(1); Zhao, Wei(1); Duan, Yixiang(1); Wang, Haojing(1)Source: Chinese Optics Letters Volume: 9 Issue: SUPPL. 1 DOI: Published: June 2011Abstract:The characteristics of air plasma are studied using laser-induced breakdown spectroscopy at room temperature in air at atmospheric pressure. The electron temperature of 20796 K is determined using the Boltzmann plot method with six ionic nitrogen lines at 444.703, 463.054, 500.515, 566.663, 594.165, and 648.205 nm. The electron number density inferred by measuring the Stark broadened profile of well-isolated Hα line (656.273 nm) is 1.83 × 1017 cm-3. The hypotheses of the local thermodynamic equilibrium and optically thin plasma are verified based on the experimental results. These results are beneficial for better understanding of the terahertz (THz) wave generation in pulsed laser induced air plasma. ? 2011 Chinese Optics Letters.Accession Number: 20113214224373 -
Record 254 of
Title:Three mirror anastigmatic zoom system using deformable mirrors
Author(s):Zhao, Xin(1); Xie, Yong-Jun(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8196 Issue: DOI: 10.1117/12.900730 Published: 2011Abstract:In order to optically vary the effect focal length of optical zoom system, adds two or more active optics which could supply variable the focal length, and create an imaging system with variable optical magnification that has no macroscopic moving parts. Based on this design concept, and connected with off-axis three-mirror reflective optical system design, we have presented preliminary modeling showing that active optical elements can be used as to create a zoom system that the effective focal length from 1000 mm to 3000 mm in ZEMAX, the FOV(Field of view) is 16°×2° -6.87°×0. 86°, and the F/# is 5-15, the whole system is composed of 3 reflective mirrors(DM, Deformable Mirrors). In order to zoom system, the F/# and three reflective mirror's radius, were variable. The MTF more than 0.45 at the spatial frequency of 42lp/mm and approaches the diffraction limit, the maximum RMS spot diameter less than detector's size. The results show that the imaging quality can satisfy the requirement of the system. ? 2011 SPIE.Accession Number: 20113614296279 -
Record 255 of
Title:Tunable and robust reflection-free waveguides based on a gyromagnetic photonic crystal
Author(s):Lu, H.(1); Liu, X.M.(1); Zhou, R.(1); Mao, D.(1); Gong, Y.(1)Source: Journal of Electromagnetic Waves and Applications Volume: 25 Issue: 11-12 DOI: 10.1163/156939311797164882 Published: 2011Abstract:We propose and numerically investigate a kind of tunable and robust reflection-free waveguides based on a gyromagnetic photonic crystal (PC). The time reversal symmetry breaking of the gyromagnetic PC under out-of-plane dc magnetic fields gives rise to one-way edge modes in both the second and third band gaps. It is found that the propagating properties of one-way modes in the waveguides can be easily controlled by adjusting the directions of external magnetic fields. Moreover, the one-way modes are robust against the disorder in the waveguides. ? Koninklijke Brill NV, Leiden, 2011.Accession Number: 20113614305247 -
Record 256 of
Title:Dissipative soliton generation/compression in compact all-fibre laser system
Author(s):Wang, L.R.(1); Liu, X.M.(1); Gong, Y.K.(1); Mao, D.(1); Lu, H.(1)Source: Electronics Letters Volume: 47 Issue: 6 DOI: 10.1049/el.2010.3674 Published: March 17, 2011Abstract:The generation and compression of dissipative-soliton (DS) pulses in a compact erbium-doped all-fibre laser system is investigated experimentally. The high-energy picosecond DSs can be dechirped to femtosecond pulses by a segment of singlemode fibre with the maximal compression factor of 122. It is found that the necessary dispersion to compress DSs is approximately proportional to their initial pulse durations, and the larger the spectrum width, the less the dispersion needed to dechirp the DSs. ? 2011 The Institution of Engineering and Technology.Accession Number: 20112214015259 -
Record 257 of
Title:Broadband terahertz spectroscopy
Author(s):Fan, Wenhui(1)Source: Chinese Optics Letters Volume: 9 Issue: 11 DOI: 10.3788/COL201109.110008 Published: November 2011Abstract:An overview of the major techniques to generate and detect THz radiation so far, especially the major approaches to generate and detect coherent ultra-short THz pulses using ultra-short pulsed laser, has been presented. And also, this paper, in particularly, focuses on broadband THz spectroscopy and addresses on a number of issues relevant to generation and detection of broadband pulsed THz radiation as well as broadband time-domain THz spectroscopy (THz-TDS) with the help of ultra-short pulsed laser. The time-domain waveforms of coherent ultra-short THz pulses from photoconductive antenna excited by femtosecond laser with different pulse durations and their corresponding Fourier-transformed spectra have been obtained via the numerical simulation of ultrafast dynamics between femtosecond laser pulse and photoconductive material. The origins of fringes modulated on the top of broadband amplitude spectrum, which is measured by electric-optic detector based on thin nonlinear crystal and extracted by fast Fourier transformation, have been analyzed and the major solutions to get rid of these fringes are discussed. ?2011 Chinese Optics Letters.Accession Number: 20114914584724 -
Record 258 of
Title:Observations of four types of pulses in a fiber laser with large net-normal dispersion
Author(s):Wang, Leiran(1); Liu, Xueming(1); Gong, Yongkang(1); Mao, Dong(1); Duan, Lina(1)Source: Optics Express Volume: 19 Issue: 8 DOI: 10.1364/OE.19.007616 Published: April 11, 2011Abstract:Four different types of pulses are experimentally obtained in one erbium-doped all-fiber laser with large net-normal dispersion. The proposed laser can deliver the rectangular-spectrum (RS), Gaussian-spectrum (GS), broadband-spectrum (BS), and noise-like pulses by appropriately adjusting the polarization states. These kinds of pulses have distinctly different characteristics. The RS pulses can easily be compressed to femtosecond level whereas the pulse energy is restricted by the trend of multi-pulse shaping with excessive pump. The GS and BS pulses always maintain the single-pulse operation with much higher pulse-energy and accumulate much more chirp. After launching the pulses into the photonic-crystal fiber, the supercontinuum can be generated with the bandwidth of >700 nm by the BS pulses and of ～400 nm by the GS pulses, whereas it can hardly be generated by the RS pulses. The physical mechanisms behind the continuum generation are qualitatively investigated relating to different operating regimes. This work could help to a deeper insight of the normal-dispersion pulses. ?2011 Optical Society of America.Accession Number: 20111613915823 -
Record 259 of
Title:Generation of 10-GHz ultra-short pulses with low time jitter in an actively mode-locked fiber laser
Author(s):Feng, H.(1); Zhao, W.(1); Yan, S.(1); Xie, X.P.(1)Source: Laser Physics Volume: 21 Issue: 2 DOI: 10.1134/S1054660X11030017 Published: February 2011Abstract:We have experimentally achieved the 8.3-ps ultra-short pulse at 10 GHz repetition rate with the time jitter as low as 590 fs in an actively mode-locked fiber ring laser. The ring-cavity laser is mode-locked by a semiconductor optical amplifier based on cross-gain modulation. The external CW source is modulated with radio frequency signal by an amplitude modulator as the external optical pulses and, then, injected into the fiber ring cavity to achieve active mode locking. Further investigating the laser output characteristics, it indicates that the linewidth of employed CW source affects properties of the generated ultra-short pulse, such as phase noise and time jitter. Ultra-short pulse at high repetition rate with low time jitter can be generated by the optimization of CW laser source. ? Pleiades Publishing, Ltd., 2011.Accession Number: 20110913706206 -
Record 260 of
Title:Enhanced efficiency of multiple four-wave mixing induced by modulation instability in low-birefringence fibers
Author(s):Liu, X.M.(1)Source: Journal of Lightwave Technology Volume: 29 Issue: 2 DOI: 10.1109/JLT.2010.2097241 Published: 2011Abstract:Modulation instability (MI) induced by two strong beams and a weak beam via cross phase modulation is investigated. Multiple four-wave-mixing (FWM) processes associated with the MI in low-birefringence fibers are studied both theoretically and experimentally. The coupled-mode equations describing the MI-induced FWM nonlinear interactions between pump waves and sideband waves are derived. Theoretical and experimental results show that, on the assistance of MI, new optical frequencies can be generated quite efficiently from multiple FWM processes. More than eleven sidebands are experimentally achieved by the MI-driven multiple FWM processes. The transfer of energy from pumps to sidebands can be dramatically enhanced by the MI-induced parametric process. The experimental observations by using a piece of highly nonlinear dispersion-flattened photonic-crystal fiber confirm our theoretical predictions. ? 2011 IEEE.Accession Number: 20110313588927 -
Record 261 of
Title:Nanoplasmonic triple-wavelength demultiplexers in two-dimensional metallic waveguides
Author(s):Lu, H.(1); Liu, X.M.(1); Wang, L.R.(1); Mao, D.(1); Gong, Y.K.(1)Source: Applied Physics B: Lasers and Optics Volume: 103 Issue: 4 DOI: 10.1007/s00340-011-4525-0 Published: June 2011Abstract:A novel kind of plasmonic wavelength demultiplexers (WDMs) based on two-dimensional metal-insulator-metal waveguides with side coupled nanocavities (SC-NCs) is proposed and numerically investigated. The WDMs contain three waveguide output channels, each of which functions as a dual-stopband plasmonic filter. The demultiplexing wavelengths can be tuned by controlling the lengths and widths of SCNCs. The finite-difference time-domain results can be accurately analyzed by the resonant theory of nanocavity. Our structures have important potential applications for design of WDM systems in highly integrated optical circuits. ? Springer-Verlag 2011.Accession Number: 20113714317115 -
Record 262 of
Title:Comparison of pulse evolutions in low and ultra-large anomalous dispersion mode-locked fiber lasers
Author(s):Duan, L.N.(1); Liu, X.M.(1); Wang, L.R.(1); Mao, D.(1); Wang, G.X.(1)Source: Laser Physics Volume: 21 Issue: 5 DOI: 10.1134/S1054660X11090052 Published: May 2011Abstract:We have investigated and compared the pulse evolutions in low and ultra-large anomalous dispersion erbium-doped fiber lasers mode-locked by the nonlinear polarization rotation technique. Two lasers deliver the pulses that exhibit quite distinct characteristics such as pulse duration, spectral width, and spectral sidebands. Experimental observations show that the spectral width decreases from several nanometers to less than one nanometer whereas pulse duration extends about three times by changing the cavity dispersion from -0.03 to -15.50 ps2. The solitons in ultra-large anomalous fiber laser show dips in the optical spectrum, which is quite distinct from that of conventional solitons observed in low anomalous regime. ? 2011 Pleiades Publishing, Ltd.Accession Number: 20112314036739 -
Record 263 of
Title:Optical bistability in metal-insulator-metal plasmonic waveguide with nanodisk resonator containing Kerr nonlinear medium
Author(s):Wang, Guoxi(1); Lu, Hua(1); Liu, Xueming(1); Gong, Yongkang(1); Wang, Leiran(1)Source: Applied Optics Volume: 50 Issue: 27 DOI: 10.1364/AO.50.005287 Published: September 20, 2011Abstract:We numerically investigate the optical bistability effect in the metal-insulator-metal waveguide with a nanodisk resonator containing a Kerr nonlinear medium. It is found that the increase of the refractive index, which is induced by enhancing the incident intensity, can cause a redshift for the resonance wavelength. The local resonant field excited in the nanodisk cavity can significantly increase the Kerr nonlinear effect. In addition, an obvious bistability loop is observed in the proposed structure. This nonlinear structure can find important applications for all-optical switching in highly integrated optical circuits. ? 2011 Optical Society of America.Accession Number: 20113914366057 -
Record 264 of
Title:Single- and dual-pulse oscillation in a passively Q-switched Nd:YAG microchip laser
Author(s):Niu, Linquan(1); Gao, Cunxiao(1); Zhu, Shaolan(1); Sun, Chuandong(1); He, Haodong(1); Song, Zhiyuan(1); Tang, Weidong(1)Source: Optics Express Volume: 19 Issue: 21 DOI: 10.1364/OE.19.020628 Published: October 10, 2011Abstract:Experimental investigation of single and dual pulses in a passively Q-switched Nd:YAG microchip laser with a Cr4+:YAG saturable absorber has been reported. The dual pulses consist of a main and a satellite pulse with respective spectra, intensities, and durations. It is found that the preponderant oscillating mode gives birth to the main pulse, and the other oscillating mode corresponds to the satellite pulse. Our results demonstrate that the dual-pulse emission results from double-longitudinal-mode oscillation in high pump regime. ? 2011 Optical Society of America.Accession Number: 20114214430549