High-order femtosecond vortices up to the 30th order generated from a powerful mode-locked Hermite-Gaussian laser

Femtosecond vortex beams are of great scientific and practical interest because of their unique phase properties in both the longitudinal and transverse modes,enabling multi-dimensional quantum control of light fields.Until now,generating femtosecond vortex beams for applications that simultaneously require ultrashort pulse duration,high power,high vortex order,and a low cost and compact laser source has been very challenging due to the limitations of available generation methods.Here,we present a compact apparatus that generates powerful high-order femtosecond vortex pulses via astigmatic mode conversion from a mode-locked Hermite-Gaussian Yb:KGW laser oscillator in a hybrid scheme using both the translation-based off-axis pumping and the angle-based non-collinear pumping techniques.This hybrid scheme enables the generation of femtosecond vortices with a continuously tunable vortex order from the 1st up to the 30th order,which is the highest order obtained from any femtosecond vortex laser source based on a mode-locked oscillator.The average powers and pulse durations of all resulting vortex pulses are several hundred milliwatts and<650 fs,respectively.In particular,424-fs 11th-order vortex pulses have been achieved with an average power of 1.6 W,several times more powerful than state-of-the-art oscillator-based femtosecond vortex sources.

1514 nm eye-safe passively Q-switched self-optical parametric oscillator based on Nd3+-doped MgO:PPLN

We examined a 1514 nm eye-safe passively Q-switched self-optical parametric oscillator. The nonlinear crystal is an a-cut Nd:MgO:PPLN crystal, and the size of the crystal was 6 mm × 2 mm × 30 mm with 0.4 at.%Nd^3+ doped and a grating period of 29.8 μm. When the crystal absorbed 12.8 W, the output maximum singlepulse energy reached 39 μJ, and a pulse width of 6.1 ns at a repetition rate of 5.4 kHz was obtained.The peak power was 6 kW, giving a slope efficiency of 42%.

Fabrication and growth mechanism of one-dimensional Heusler alloy nanostructures with different morphologies on anodic aluminum oxide template by magnetron sputtering

Heusler alloys are a kind of intermetallic compounds with highly-ordered arrangement of atoms.Many attractive functional materials have been developed in Heusler alloys.Due to the application requirements of materials in new-generation electronic devices and spintronics devices,one-dimensional nanostructured Heusler alloys with special functions are needed.In this work,it is proposed to grow one-dimensional Heusler alloy nanostructures(1D-HA-NSs)by magnetron sputtering plus anodic aluminum oxide(AAO)template.Nanowires with different shapes,amorphous-coated(AC)nanowires and nanotubes were successfully grown for several Heusler alloys.AC nanowires are the unique products of our method.Heusler alloy nanotubes are reported for the first time.The one-dimensional nanostructures grow on the surface of the AAO substrate rather than in the holes.The top of the pore wall is the nanostructure growth point,the shape of which determines the morphology of the nanostructures.A general growth mechanism model of one-dimensional nanostructures on AAO template was established and further confirmed by experimental observation.