Relativistic high-order harmonics from a few-cycle laser driven plasma surface is a very promising source of an intense and isolated attosecond light pulse. The laser to harmonics conversion efficiency and the “purity” of an isolated attosecond light pulse are generally determined by a combination of interaction parameters, such as laser intensities, incidence angles, pulse durations, carrier-envelope phases and plasma scale lengths. We had already previously investigated the effect of a three-parameter combination of the laser pulse duration, the carrier-envelope phase and the plasma scale length. To complement our previous work, the parametric dependence of the other two three-parameter combinations: the carrier-envelope phase, the plasma scale length, either combined with the laser intensity or the incidence angle, were systematically investigated through one dimensional particle-in-cell simulations. We found that, although the impact of parameter combinations on attosecond pulse generations is generally complicated, there exist however an optimal plasma scale length and an optimal incidence angle to efficiently generate high-order harmonics and intense attosecond light pulses. When other parameters are fixed, a moderately intense relativistic laser is more advantageous to realize an isolated attosecond light pulse in a broad controlling parameters range. And a larger incidence angle favors a higher isolation degree as well as a broader range of controlling parameters towards the generation of intense isolated attosecond light pulses. In order to interpret these simulation results, we have modeled the corresponding relativistic electron dynamics, using which the underlying physics are discussed.
Harmonics from relativistic laser driven plasma surfaces is a prospective high energy attosecond light source in future XUV pump-probe experiments. Among all the schemes, the most efficient and direct way to realize an isolated attosecond pulse is through using a few-cycle laser as the driving pulse. The two goodness criteria: the laser to harmonics energy conversion efficiency and the “purity” of an isolated attosecond pulse are generally determined by a combination of interaction parameters. Through using particle-in-cell simulations and relativistic electron dynamics model analyses, we explain how these two criteria are affected by the laser intensity, incidence angle, carrier-envelope phase, and the plasma scale length. We found that, there exist an optimal plasma scale length and an optimal incidence angle to efficiently generate harmonics and intense attosecond light pulses. When other parameters are fixed, using a moderately intense relativistic laser or using a large incidence angle could result in a higher isolation degree as well as a broader range of controlling parameters to realize an isolated attosecond light pulse.
Faraday anomalous dispersion optical filters (FADOFs) were used in laser frequency locking experiment as early as 1969, and later this laser was named Faraday laser. Typically, as the key element in the Faraday laser, the housing for the FADOF is machined from metal and insulation material. Here, we present an alternative to the commonly used option that utilizes 3D printing. We measure the inner magnetic field intensity of the housing for the FADOF and the transmission spectrum of our FADOF system, and show that it is sufficient for use in Faraday laser. Besides, we also characterize the performance of our Faraday laser system using atomic spectroscopy. The performance and cost of 3Dprinted FADOF housing make it an appealing option.
A source of isolated attosecond pulses with photon energies lying in the water window soft x-ray range is currently under development at Deutsches Elektronen-Synchrotron. Such a source will be driven by the newly developed sub-cycle millijoule-level parametric waveform synthesizer. In this proceeding on theoretical study, in order to optimize the x-ray pulse energy while maintaining good pulse isolation in the soft x-ray range, a multi-objective genetic algorithm is exploited to tailor the laser electric field waveform. The resulting synthesized waveform are then employed in a macroscopic propagation study to predict x-ray pulse characteristics from a real experiment.
We present a study of the saturated absorption spectroscopy on cesium D2 line (6S1/2F = 4 → 6P3/2) induced by a multiwavelength laser and its specificity. Compared with the traditional saturated absorption spectroscopy induced by single-frequency laser, the major difference is that the peak amplitude can reach more than half of the Doppler background, and the second is that the number of the saturated absorption peaks is increased and not in the same direction, the line shape and amplitude of the spectrum change with the magnetic field. The frequency components of the multi-wavelength laser need to be studied in order to further analyze the principle of generation of the spectrum. The cesium atom laser spectroscopy induced by this unique multi-wavelength laser can be used for laser frequency stabilization. The interaction of multi-wavelength laser and atom can increase the utilization rate of the atoms, increase the signal amplitude, help to improve the signal-to-noise ratio, and then improve the frequency stability of lasers. In this experiment, the multiwavelength laser spectroscopy induced by the superposition of saturation effect, absorption effect, optical pumping effect and other physical effect is of great interest in high resolution laser spectroscopy and laser frequency stabilization.
Known as a unique optical filter, Faraday anomalous dispersion optical filter has prior advantages to provide high transmission and high background noise rejection with excellent image quality. In this paper, we studied the temperature characteristics of Faraday anomalous dispersion optical filter at Cs 852 nm transition. The transmitted spectrum is carefully measured under different Cs cell temperatures (39°C–57°C) and environment temperatures (23°C–26°C). The results could provide important reference for further research on Faraday laser, lidar remote sensing systems and imaging systems.
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