Formation of parabolic pulses at femtosecond time scale by means of passive nonlinear reshaping in normally dispersive optical fibers is analyzed. Two approaches are examined and compared: the parabolic waveform formation in transient propagation regime and parabolic waveform formation in the steady-state propagation regime. It is found that both approaches could produce parabolic pulses as short as few hundred femtoseconds applying commercially available fibers, specially designed all-normal dispersion photonic crystal fiber and modern femtosecond lasers for pumping. The ranges of parameters providing parabolic pulse formation at the femtosecond time scale are found depending on the initial pulse duration, chirp and energy. Applicability of different fibers for femtosecond pulse shaping is analyzed. Recommendation for shortest parabolic pulse formation is made based on the analysis presented.
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http://dx.doi.org/10.1364/OE.21.017769 | DOI Listing |
High-field THz sources with peak field strengths exceeding MV/cm are essential for nonlinear THz spectroscopy and coherent control of matter on ultrafast time scales. Two-color femtosecond laser plasma sources employing long filamentation have been reported as providing single-cycle, >MV/cm fields, with multi-decade spanning bandwidth and polarization control, making them promising sources for such experiments. In this work, we report the observation of spatiotemporal spreading of the THz pulse when standard off-axis parabolic mirrors are used for collection and focusing of long filament plasma-based THz pulses.
View Article and Find Full Text PDFSci Rep
November 2024
Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, 73 Goryeodae-ro, Seongbuk-gu, 02841, Seoul, Republic of Korea.
This study aimed to analyze vital sign characteristics of adult patients admitted at the Tertiary Hospital, and to define fever threshold and average body temperature by examining the tympanic temperatures of all patients. Retrospective medical data were extracted from 9195 patients aged > 21 years admitted to a tertiary hospital for elective surgeries between 2016 and 2020. Data regarding the patients' vital signs during their hospital stay, including tympanic body temperature, heart rate, and respiratory rate, were analyzed according to age, sex, and circadian rhythm.
View Article and Find Full Text PDFRev Sci Instrum
October 2024
International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
We have developed a terahertz (THz) nonlinear spectrometer at low temperatures (1.5-300 K) and under high magnetic fields (up to 10 T) by combining the laser-driven table-top intense THz source with a superconducting magnet. The strong-field THz pump pulse was generated from LiNbO3 crystal using the tilted-pulse-front technique and tightly focused into the center of the magnet by an off-axis parabolic mirror and a THz lens.
View Article and Find Full Text PDFRev Sci Instrum
September 2024
Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
We have developed a cryogen-free, low-temperature terahertz scanning tunneling microscope (THz-STM). This system utilizes a continuous-flow cryogen-free cooler to achieve low temperatures of ∼25 K. Meanwhile, an ultra-small ultra-high vacuum chamber results in the reduction of the distance from sample to viewport to only 4 cm.
View Article and Find Full Text PDFResuscitation
October 2024
Service de Médecine Intensive et Réanimation, Hôpital Brabois, CHRU Nancy, 54500 Vandœuvre-Lès-Nancy, France; Faculté de Médecine de Nancy, Université de Lorraine, INSERM UMR_S1116, Vandœuvre-Lès-Nancy, France. Electronic address:
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