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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Generation of a Few Cycle Terahertz Pulse in Aperiodically Poled Lithium Niobate by Sequence of Pump Pulses
摘要： It is shown that chirped aperiodically poled lithium niobate crystal is capable to generate powerful THz pulses with controllable number of THz field oscillations (from nearly single- to multi-cycles), when it is pumped by sequence of femtosecond laser pulses with chirped delays between adjacent pulses. The peak electric field strength of about 0.3 MV/cm (for non-focused THz beam) is predicted if intensity of each pump pulse in the sequence is 20 GW/cm2.
关键词： Optical rectification,Aperiodically poled lithium niobate,Terahertz pulse,Femtosecond laser pulses
更新于2025-09-11 14:15:04
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Plasmonic layer-selective all-optical switching of magnetization with nanometer resolution
摘要： All-optical magnetization reversal with femtosecond laser pulses facilitates the fastest and least dissipative magnetic recording, but writing magnetic bits with spatial resolution better than the wavelength of light has so far been seen as a major challenge. Here, we demonstrate that a single femtosecond laser pulse of wavelength 800 nm can be used to toggle the magnetization exclusively within one of two 10-nm thick magnetic nanolayers, separated by just 80 nm, without affecting the other one. The choice of the addressed layer is enabled by the excitation of a plasmon-polariton at a targeted interface of the nanostructure, and realized merely by rotating the polarization-axis of the linearly-polarized ultrashort optical pulse by 90°. Our results unveil a robust tool that can be deployed to reliably switch magnetization in targeted nanolayers of heterostructures, and paves the way to increasing the storage density of opto-magnetic recording by a factor of at least 2.
关键词： femtosecond laser pulses,plasmon-polariton,storage density,magnetic recording,all-optical magnetization reversal
更新于2025-09-11 14:15:04
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[Laser Institute of America ILSC? 2019: Proceedings of the International Laser Safety Conference - South Kissimmee, Florida, USA (March 18–21, 2019)] International Laser Safety Conference - Simulated supercontinuum generation in the human eye
摘要： Femtosecond laser pulses of sufficiently high intensity are prone to undergo a number of nonlinear effects while propagating in media. The increasing use of high intensity, femtosecond laser systems underscores the need to understand the retinal hazards generated by nonlinear optical effects, the generation of supercontinuum. Current laser safety standards such as ANSI Z136.1 for pulse wavelengths of 1200 nm - 1400 nm have been determined from experimental studies using pulse durations longer than 100 fs and linear pulse simulations. The combination of strong absorption, broad bandwidth, and dispersive effects makes standard nonlinear pulse simulation methods, based on the slowly varying envelope approximation, unsuitable for the study of near-infrared pulses in biological tissues. To model retinal hazards, we leverage an existing model for linear ultrafast pulse propagation that does not rely on an envelope approximation and simulate spectral broadening in water. Using one-dimensional simulations incorporating the effect of self-focusing, we validate the model using previous experiments for white-light supercontinuum generation in water. We then simulate propagation of 10 fs - 1 ps, 1200 nm - 1400 nm pulses at the current ANSI MPE limit for pulses under 10 ps.
关键词： nonlinear effects,supercontinuum generation,femtosecond laser pulses,self-focusing,ANSI Z136.1,retinal hazards
更新于2025-09-11 14:15:04