146 research outputs found
Mode locking of a Cr:YAG laser with carbon nanotubes
No full textWe report on mode locking of a bulk Cr:YAG laser by using a transmission-type single-walled carbon nanotube saturable absorber. Stable and self-starting laser operation in the picosecond and femtosecond regimes is obtained at wavelengths around 1.5 mu m. Tunable transform-limited sub-100 fs pulses are generated at a repetition rate of 85 MHz with an output power up to 110 mW. (C) 2010 Optical Society of Ameri
Sub-100 fs single-walled carbon nanotube saturable absorber mode-locked Yb-laser operation near 1 mu m
No full textTransmission-and reflection-type single-walled carbon nanotube saturable absorbers (SWCNT-SAs) were designed and fabricated for passive mode-locking of bulk lasers in the 1 mu m spectral range. Mode-locked laser operation based on a diffusion-bonded Yb:KYW/KYW crystal was demonstrated, and pulses as short as 83 fs and 140 fs were achieved applying reflection-type and transmission-type SWCNT-SA, respectively. The nonlinear parameters of the absorbers were measured to be in close vicinity to those of a semiconductor saturable absorber mirror for the same wavelength range. Mode-locking performance with SWCNT-SAs and the SESAM was compared utilizing the same cavity, with the SESAM resulting in only slightly shorter pulses of 66 fs duration. The nearly identical performance indicates that well-optimized SWCNT-SAs can substitute SESAMs even in the 1 mu m region. (C) 2009 Optical Society of Ameri
Fabrication and characterization of ultrafast carbon nanotube saturable absorbers for solid-state laser mode locking near 1μm
No full textTransmitting and reflecting ultrafast saturable absorbers based on single-walled carbon nanotubes are developed that are applicable for stable mode locking of bulk solid-state lasers operating near 1 mu m. For fabrication of these saturable absorbers, relatively simple spin coating and spray methods are employed. Parameters important for stable mode locking, such as transient nonlinear absorption, saturation fluence, and recovery time, are investigated by nonlinear transmission and time-resolved pump-probe measurements near 1 mu m. Typical modulation depths and recovery times amount to similar to 0.21%-0.25% and < 1 ps, respectively. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.299959
Short text authorship attribution via sequence kernels, Markov chains and author unmasking: An investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts
Short Text Authorship Attribution via Sequence Kernels, Markov Chains and Author Unmasking: An Investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts.
Short text authorship attribution via sequence kernels, Markov chains and author unmasking: An investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts
Passive mode-locking of a Tm-doped bulk laser near 2 mu m using a carbon nanotube saturable absorber
No full textStable and self-starting mode-locking of a Tm:KLu(WO4)(2) crystal laser is demonstrated using a transmission-type single-walled carbon nanotube (SWCNT) based saturable absorber ( SA). These experiments in the 2 mu m regime utilize the E-11 transition of the SWCNTs for nonlinear saturable absorption. The recovery time of the SWCNT-SA is measured by pump-probe measurements as similar to 1.2 ps. The mode-locked laser delivers similar to 10-ps pulses near 1.95 mu m with a maximum output power of up to 240 mW at 126 MHz repetition rate. (C) 2009 Optical Society of Ameri
Passive mode locking of Yb : KLuW using a single-walled carbon nanotube saturable absorber
No full textMode locking of an Yb-doped bulk laser in the 1 le,m spectral range using a single-walled carbon nanotube saturable absorber (SWCNT-SA) is demonstrated for the first time, to our knowledge. Passive mode locking of an Yb:KLuW laser resulted in nearly transform-limited pulses as short as 115 fs at 1048 nm. In addition, the nonlinear response of the SWCNT SA was measured, yielding a modulation depth of 0.25% and a relaxation time of 750 fs. (C) 2008 Optical Society of Americ
Epigrafía maya: Tabasco
No full textLa información de esta miniguía está basada en los trabajos de M. Coe, N. Grove, S. Guenter, S. Martín, P. Mathews, Linda Schele, D. Stuart y M. U. Zender.Cuatro de las grandes culturas desarrolladas en Mesoamérica poseían un sistema propio de escritura: zapoteca, maya, mixteca y náhuatl. La escritura maya fue el sistema más complejo y el que más correspondencia tuvo con la lengua hablada. Parece haber surgido alrededor del 100 o 200 d.C., y según la mitología fue el dios ltzamná quien la inventó. Sus últimas expresiones se sitúan alrededor de 1696. Los mayas utilizaron diferentes soportes para plasmar la escritura y su historia escrita, como códices de papel vasijas de barro, textiles, pieles, estelas y altares de piedra, dinteles y cajas de madera, pendientes de hueso y hasta finas puntas de cola de mantarraya, entre otros.</p
Fiber event horizon by single color pump
No full textWe demonstrate both numerically and experimentally the direct creation of an optical event horizon that arises from the interaction of a solitary optical pulse with a group-velocity matched dispersive wave. (C) 2019 The Author(s
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