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Silica optical resonators with high quality factors, small mode volumes, and high refractive index contrast are desirable in many applications throughout the fundamental and applied sciences. However, these parameters are not easily modified in plain silica devices. In the present work, we theoretically and experimentally demonstrate the use of high refractive index sol-gel coatings to achieve a significant reduction in mode volume of silica toroids while maintaining high quality factors. In addition to tuning the mode volume, the presence of the coating changes both the location and shape of the optical field. 相似文献
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L. Kornaszewski G. Maker G.P.A. Malcolm M. Butkus E.U. Rafailov C.J. Hamilton 《Laser \u0026amp; Photonics Reviews》2012,6(6):L20-L23
Experimental demonstration of semiconductor saturable absorber‐free mode‐locked optically pumped semiconductor disk laser is presented. The origin of pulsed operation is attributed to the intensity dependent Kerr lens effect arising in the semiconductor gain medium. Achieved results represent a novel method to mode‐lock this type of laser opening new application opportunities. The laser worked stably in both hard and soft aperture configurations. No semiconductor saturable absorber was used in the laser cavity and the operation was self‐starting. The laser was mode‐locked at 210 MHz repetition rate with 1.5 W average output power and 930 fs pulse width at 985 nm. A record high 6.8 kW peak power was achieved. Measured data is presented along with a discussion of the Kerr lens effect in the cavity. 相似文献
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Demonstration of a high-speed nonscanning imaging spectrometer 总被引:1,自引:0,他引:1
Descour MR Volin CE Dereniak EL Thome KJ Schumacher AB Wilson DW Maker PD 《Optics letters》1997,22(16):1271-1273
We report results from a field demonstration of a nonscanning high-speed imaging spectrometer [computed-tomography imaging spectrometer (CTIS)] capable of simultaneously recording spatial and spectral information about a rapidly changing scene. High-speed spectral imaging was demonstrated by collection of spectral and spatial snapshots of a missile in flight. This instrument is based on computed-tomography concepts and operates in the visible spectrum (430-710nm). Raw image data were recorded at video frame rate (30frames / s) and an integration time of 2ms. An iterative reconstruction of the spatial and spectral scene information from each raw image took 10s. We present representative missile spectral signatures from the missile firing. The accuracy of the high-speed spectrometer is demonstrated by comparison of extended-source static-scene spectra acquired by a nonimaging reference spectrometer with spectra acquired by use of CTIS imaging of the same static scenes. 相似文献
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Using the long-path FTIR method, glycolaldehyde, CH2(OH)CHO, was detected among the products in photolysis of mixtures containing C2H4, NO and RONO (R = alkyl group) at ppm concentrations in air. The results suggest the occurrence of both unimolecular dissociation and O2 reaction of an oxy-radical, CH2(OH)CH2O, formed in the HO-initiated oxidation of C2H4 in the presence of NO. 相似文献
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A Gurtu P K Malhotra I S Mittra P M Sood SC Gupta VK Gupta GL Kaul LK Mangotra Y Prakash NK Rao ML Sharma 《Pramana》1974,3(5):311-322
This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR em = 〈n s〉/〈n ch〉, where 〈n ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R em = 1·71 implies an effectiveA-dependence ofR A =A 0.18,i.e., a very weak dependence. Predictions ofR em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production. 相似文献
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The kinetics and mechanism of Cl-atom-initiated reactions of CHO? CHO were studied using the FTIR detection method to monitor the photolysis of Cl2–CHO? CHO mixtures in 700 torr of N2–O2 diluent at 298 ± 2 K. The observed product distribution in the [O2] pressure of 0–700 torr combined with relative rate measurements provide evidence that: (1) the primary step is Cl + CHO? CHO → HCl + CHO? CO with a rate constant of [3.8 ± 0.3(σ)] × 10?11 cm3 molecule?1 s?1; (2) the primary product CHO? CO unimolecularly dissociates to CHO and CO with an estimated lifetime of ≤ca. 1 × 10?7 s; (3) alternatively, the CHO? CO reacts with O2 leading to the formation of CO, CO2, and most likely the HO radical, but no stable products containing two carbon atoms; (4) the HO2 radical, formed in the secondary reaction CHO + O2 → HO2 + CO, reacts with the CHO? CHO with a rate constant ca. 5 × 10?16 cm3 molecule?1 s?1 to form HCOOH and a new transient product resembling that detected previously in the HO2 reaction with HCHO. 相似文献
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