Wavelength-tunable few-cycle pulses in visible region generated through soliton-plasma interactions.

We numerically investigate the generation of wavelength-tunable few-cycle pulses in the visible spectral region through soliton-plasma interactions. We found that in a He-filled single-ring photonic crystal fiber (SR-PCF), soliton-plasma interactions could shift the optical spectra of pulses propagating in the fiber to shorter wavelengths. Through adjusting the single pulse energy launched into the fiber, the central wavelength of these blueshifting pulses could be continuously tuned over hundreds of nanometers, while maintaining a high energy conversion efficiency of >57%. Moreover, we observed that during the nonlinear pulse propagation in the SR-PCF, soliton self-compression effects enhanced the plasma density in the fiber at high pulse energies, which could modulate the phase-matching condition of ultraviolet (UV) dispersive wave (DW) generation. Furthermore, we employed the recently-developed model to study numerically the loss and dispersion of the SR-PCF in its resonant and anti-resonant spectral regions, and demonstrated the remarkable influence of the core-cladding resonance on the process of soliton-plasma interactions. The numerical results demonstrated here pave the way to develop wavelength-tunable, few-cycle light sources in the visible region, which may have considerable application potential in pump-probe spectroscopy and strong-field physics.

Interferometric investigation of the influence of argon buffer gas on the characteristics of laser-induced aluminum plasmas.

An interferometric analysis was performed to investigate the influence of argon (Ar) buffer gas on the characteristics of laser-induced aluminum (Al) plasma at atmospheric pressure. The plasma was produced by focusing a Q-switched Nd:YAG laser pulse (λ=1064 nm, pulse duration ∼5 ns, E=6.0 mJ) onto an Al target. The interference patterns were constructed using a Nomarski interferometer incorporated with a frequency-doubled, Q-switched Nd:YAG laser (λ=532 nm, pulse duration ∼10 ns) that generates an interferometric probe beam. The interferometric measurements were carried out as a function of the elapsed time after the onset of breakdown under the conditions of open air and an Ar gas jet flow (5 l/min). With the injection of an Ar buffer gas jet in the ablation process, an increase in electron density and a preferential axial plasma expansion of the plasma plume were observed during the early stages of plasma formation as a consequence of increased inverse-Bremsstrahlung (IB) absorption efficiency.

Study of operation dynamics for crystal temperature measurement in a diode end-pumped monolithic Yb:YAG laser.

A temperature measurement scheme was proposed in a diode end-pumped thin monolithic Yb:YAG laser by analyzing the red-shifting behaviors of each lasing peak. The amount of peak shift was measured on the basis of the threshold lasing spectrum by using a chopped pump beam. In order to determine the effective scale factor, the ratio between the peak shift and the temperature rise, the dynamics of the spectral shift, the output beam profile, and the output power were investigated. The effective scale factor was determined to be about 0.0114 nm/°C in the case of the crystal sandwiched by copper bocks with a hole, wherein the plane stress approximation is valid. On the other hand, the effective scale factor significantly decreased in the case of the crystal sandwiched by sapphire plates.