Ultrafast lasers with both high peak-power and high average-power will open new avenues for many applications. While conventional technologies of Ti:sapphire laser amplification and optical parametric amplification can achieve several tens of watts of averagepower, scaling to a higher average-power is challenging due to thermal limitations. Here, we demonstrate that the quasi-parametric chirped-pulse amplification (QPCPA) can break this average-power barrier. QPCPA is proven robust against the thermal dephasing by obstructing the back-conversion effect. Numerical simulations show that QPCPA based on a Sm:YCOB crystal can support peak powers of 3 TW at 5 kHz and 13.5 PW at 1 Hz, with average powers exceeding 150 W in both cases. We also discuss the prospects of QPCPA with the recently proposed configuration of temperature-insensitive phase matching, which is promising to simultaneously achieve higher peak-power and higher average-power.

Noise is a fundamental and ubiquitous problem in optics, and only those out of the signal bandwidth can be filtrated away by traditional spectral filters. This paper presents an in‐band noise filtering scheme where the ultrafast signal is controlled by spatio‐spectral coupling such that the signal and its in‐band noise can be separated in the spatio‐spectral domain. As an example of its impact on ultra‐intense lasers, this filter is applied to show that the noise produced in chirped‐pulse amplification can be efficiently filtrated within the signal bandwidth. Near‐noiseless amplification of pulses with contrast as high as 1011 is demonstrated in a high‐gain optical parametric chirped‐pulse amplifier, resulting in approximately 40 times enhancement in output contrast. The simplicity, efficiency, and direct compatibility with existing techniques for short‐pulse generation will make in‐band filtering attractive to a wide range of applications in ultrafast optics and time‐resolved spectroscopy.

Full pump depletion corresponds to the upper limit of the generated signal photons relative to the pump pulse; this allows the highest peak power to be produced in a unit area of ultraintense laser amplifiers. In practical systems based on optical parametric chirped-pulse amplification, however, the typical pump depletion is only ~35%. Here, we report quasi-parametric chirped-pulse amplification (QPCPA) with a specially designed 8-cm-thick Sm:YCOB crystal that highly dissipates the idler and hence improves pump depletion. We demonstrate 56% QPCPA energy efficiency for an 810-nm signal converted from a 532-nm pump, or equivalently 85% pump depletion. As another advantage, such a record high depletion greatly suppresses the parametric superfluorescence noise in QPCPA to only ~1.5 × 10−6 relative to the amplified signal energy. These results pave the way to beyond the ten-petawatt peak power of the currently most intense lasers.

In strong-field physics experiments with ultra-intense lasers, single-shot crosscorrelator (SSCC) is essential for fast optimization of the pulse contrast and meaningful comparison with theory for each pulse shot. To simultaneously characterize an ultrashort pulse and its long pedestal, the SSCC device must have both a high resolution and large temporal window. However, the resolution and window in all kinds of single-shot measurement contradict each other in principle. Here we propose and demonstrate a novel SSCC device with two separate measurement channels: channel one for the large-window pedestal measurement has a moderate resolution but a large window, while channel two for the ultrashort pulse measurement has a small window but a high resolution; this allows the accurate characterization of the pulse contrast in single-shot. A two-channel SSCC device with a 200-fs resolution and 114-ps window has been developed and tested for its application in ultra-intense lasers at 800 nm.

Parametric interaction allows both the forward and backward energy transfers among the three interacting waves. The back-conversion effect is usually detrimental when unidirectional energy transfer is desired. In this theoretical work, we manifest that the back-conversion effect underpins the direct generation of picosecond pulse train without the need for a laser resonator. The research scenario is an optical parametric amplification (OPA) that consists of a second-order nonlinear medium, a quasi-continuous pump laser and a sinusoidal amplitude-modulated seed signal. The back-conversion of OPA can transfer the modulation peaks (valleys) of incident signal into the output valleys (peaks), which inherently induces spectral sidebands. The generation of each sideband is naturally accompanied with a phase shift of ±π. In the regime of full-back-conversion, the amount and amplitude of the sidebands reach the maximum simultaneously, and their phase constitutes an arithmetic sequence, leading to the production of picosecond pulse train. The generated picosecond pulse train can have an ultrahigh repetition rate of 40 GHz or higher, which may facilitate ultrafast applications with ultrahigh speed.