Ultrashort Laser Pulse Time Domain Sampling Technology
Sedan genereringen av ultrashort -pulser har de varit ett viktigt forskningsverktyg inom många vetenskapliga forskningsområden, såsom ultrasnabb spektroskopi, attosekund vetenskap, thz -generation osv.
Traditional measurement methods such as photodiodes and autocorrelation measurements can only measure the envelope of the pulse, but cannot obtain the phase information of the pulse. In order to solve this problem, a variety of ultrashort pulse measurement techniques have evolved, such as frequency-resolved optical gating (FROG) and dispersion scanning (D-scan). These methods är indirekta metoder som förlitar sig på rekonstruktionsalgoritmer . Jämfört med indirekta mätmetoder, direkta mätmetoder använder ultrafast tidsgrindar för att direkt prova ultrasortpulser i tidsdomänen .} för direktmätningsmetoder, kärnan i hur du ska få ultras grindar, såsom direkt med användning av attosekundpulser, med hjälp av tunneljonisering, olinjär fotokonduktivitetsprovtagningsteknik osv.
Puls Time-Domain Sampling Technology baserad på störning av fast ytvågsblandningsprocess
Nyligen föreslog ATTOSECOND Science and Technology Research Center vid Xi'an Institute of Optics and Precision Mechanics en ny tidsdomänprovtagningsteknik för ultrasortlaserpulser . Denna mätningsteknik är baserad på den tredje ordningen icke-linjär optisk effekt och erhåller ultrassast tidsgrann process. The ultrashort pulse time-domain sampling device is shown in Figure 1. First, the ultrashort pulse is divided into two laser pulses, namely the fundamental frequency light pulse and the perturbation light pulse, by mask1, and the relative delay τ between the two is controlled by a D-shaped mirror and a piezoelectric ceramic displacement stage. Then a concave reflector is used to focus the two on the front surface of the fused quartz slice. Finally, mask2 is used to block the reflected fundamental frequency light pulse and perturbation light pulse, and a lens is used to focus the generated reflected four-wave mixing modulated signal into the optical fiber head of the spectrometer.
First, the experimental device was used to measure ultrashort pulses with a central wavelength of 800 nm and a pulse width of about 30 fs generated by a Ti:Sapphire laser system. Figure 2(a) shows the waveform of the reflected four-wave mixing modulation signal measured after filtering. The corresponding spectrum and phase in the frequency domain are shown in Figure 2(b). It can be seen that the phase is flat at this time, almost a horizontal line. Then, by changing the dispersion of the perturbation light pulse, the perturbation light pulse under different chirps was measured. The measurement results are shown in Figures 2(c)-(f). Figures 2(c) and 2 (d) motsvarar positiva chirp -laserpulser, och figurerna 2 (e) och 2 (f) motsvarar negativa kvitpulser .
In order to verify the reliability of the ultrashort pulse time domain sampling technology, FROG was used to compare the ultrashort pulses. It can be seen from Figures 2(b), 2(d) and 2(f) that the results obtained by FROG and the time domain sampling technology are in good agreement. Subsequently, ultrashort pulses with a central wavelength of 1700 nm och en pulsbredd på cirka 50 FS mättes framgångsrikt genom att använda denna experimentella installation och groda .
Since the sampling process occurs on the solid surface, the phase matching condition can be automatically satisfied, so this measurement technology is suitable for measuring few-cycle or even single-cycle pulses. Subsequently, a multi-thin-slice post-compression system was built based on the Ti:Sapphire laser system, and a few-cycle pulse with a central wavelength of 800 nm and a conversion limit of about 3.4 cycles (about 9 fs) was obtained. After optimizing the dispersion of the laser pulse after spectral broadening and filtering, the waveform of the reflected four-wave mixing modulation signal is shown in Figure 3(a), and its pulse width is about 12 fs. Its corresponding spectrum and phase are shown in Figure 3(b).
The above measurement results show that the ultrashort pulse time domain sampling technology is suitable for characterizing short-cycle and few-cycle laser pulses. At present, the applicable wavelength based on the existing silicon-based and InGaAs detectors is 200-2600 nm. For laser pulses with a wavelength exceeding 2600 nm, traditional detectors kan inte direkt upptäcka blandningssignaler med fyra vågor . För att ytterligare utöka tillämpningsområdet kommer trippelfrekvenseffekten att användas i framtiden för att indirekt mäta laserpulser med ett våglängdsområde för 2600-7800 nm .
ATTOSECOND Science and Technology Research Center vid Xi'an Institute of Optics and Precision Mechanics grundades i maj 2021, ledd av forskarna Zhao Wei och Fu Yuxi . Forskningscentret Fokuserar på attosekond Science and Technology, och bedriver forskning om högkraft Advanced Laser Technology, Mid-Infrareded Femtosekond, Eche-Cycel-C-Cycel-teknik, mjukmästare att och laser ATT ATT AVSASER ATT AVSASER ATT ATT AVESER ATT ATT AVSER ATT ATT AVESER ATT ATT AVESER ATT ATT AVSER, attosecond electron microscope, ultrafast imaging, ultrafast dynamics, strong field laser physics, etc. The research center not only undertakes the construction of large scientific facilities of attosecond light sources, but also presides over a number of major national and provincial scientific research projects, including a number of National Natural Science Foundation, key R&D plans of the Ministry of Science and Technology, pre-research of major scientific and technological infrastructure of the Chinese Academy of Sciences, Shaanxi Natural Science Basic Research Plan, Shaanxi Attosecond Science and Technology Innovation Team and other scientific research projects. In recent years, the Attosecond Science and Technology Research Center has overcome the key processes and technologies of high-power thin-film lasers, achieved 1 kHz, 200 mJ-level picosecond laser output, and provided key Kärnteknologier och enheter för lokalisering av avancerade lasrar och konstruktion av avancerade attosekund laseranläggningar; föreslog och demonstrerade en direkt mätmetod för laserfält i tidsdomänen; and broke through the key difficulties of attosecond time-resolved diffraction imaging. The Attosecond Science and Technology Research Center is driven by attosecond science and technology, conducts ultrafast scientific research represented by advanced ultrafast laser technology and ultrafast dynamics detection, and is committed to building an internationally renowned highland for ultrafast science and technology research.
