Yangbao Deng

Coexistence and competition of surface diffusion and geometric shielding in the growth of 1D bismuth nanostructures and their ohmic contact

We study the physical-vapor-deposition of 1D bismuth nanostructures. Bi nanowire elongating along [012] and/or [110] direction as well as anisotropic Bi nano-columns are physical-vapor-deposited successfully. The coexistence and competition of surface diffusion and geometric shielding are critical to their formation as well as growth mode transition among them. Since physical-vapor-deposition is a vacuum process, we make use of it to fabricate the ohmic contact to prevent the damage to the bismuth nanostructures brought by the etching to their thick surface oxide layer.

Generation of ring-shaped beams by a graded-index plasma lens

We experimentally demonstrate the generation of ring-shaped beams using a plasma channel with Gaussian profile. The plasma channel is produced when an intense femtosecond pulse propagates in carbon disulfide. The refractive index of the plasma is similar to that of a graded-index lens. Due to the existence of critical plasma density, the beam from the He–Ne laser cannot pass through the center region of the plasma and is refracted in the periphery. The dark spot size of the ring-shaped beams can be controlled easily by a femtosecond pulse. We also show the propagation of ring-shaped beams in free space.

Plasma optical modulation for lasers based on the plasma induced by femtosecond pulses

We present a theoretical and experimental study of plasma optical modulation for probe lasers based on the plasma induced by pump pulses. This concept relies on two co-propagating laser pulses in carbon disulfide, where a drive laser pulse first excites plasma channels while a following carrier laser pulse is modulated by the plasma. The modulation on the probe beam can be conveniently adjusted through electron density, plasma width, propagation distance of plasma, the power of pump lasers, or the pump beams profile. The experimental results and theoretical solutions are very consistent, which fully illustrates that this method for plasma optical modulation is reasonable. This pump-probe method is also a potential measurement technique for inferring the on-axis plasma density shape.

Spin-Wave-Driven Skyrmion Motion in Magnetic Nanostrip

The photon-assisted magnetic recording utilizes the ultrafast laser to excite the spin wave in the magnetic nanostructures and accordingly switch its magnetization state. Here, by means of micromagnetic simulation, the motion of magnetic skyrmions, a topologically protected chiral magnet with few nanometer size, induced by the spin wave is studied. It is found that the magnetic skyrmion can move in the same direction of spin-wave propagation, which is first accelerated and then decelerated exponentially. The magnetic skyrmion motion originated from the robust coupling of the spin waves with the skyrmion, through the SW’s linear momentum transfer torque acting on the skyrmion. Besides amplitude, the reflectivity of the spin wave by skyrmion has tremendous impact on the velocity of skyrmion motion. The skyrmion velocities are mainly determined by the reflectivity, when the spin-wave amplitude is almost identical. Our results give guidance for the design and development of spin-wave control spintronics.

Experimental realization of spatial light modulation based on graded-index plasma channels

Abstract. We experimentally demonstrate spatial light modulation based on graded-index plasma channels induced by femtosecond pulses. The spatial profile of the probe beam can be conveniently controlled by adjusting the intensity distribution of the pump beam or by changing the relative position between pump beam and probe beam. We also show that the modulation depth of the probe beam can be controlled by adjusting the power of the pump beam.

Evolution of temporal soliton solution to the generalized nonlinear Schrödinger equation with variable coefficients and PT-symmetric potential

In this paper, the evolution of temporal soliton is investigated analytically when a laser pulse propagates in the inhomogeneous nonlinear medium with a Scarff II parity-time (PT)-symmetric potential. After a detailed analyzing the evolution of the intensity and pulse width (PW) of a temporal soliton, it is find that the chirped-free and chirped temporal soliton are stable when the dispersion coefficient is a periodic modulated function. When the dispersion coefficient are the constant and the exponential decreasing function, the chirped-free temporal soliton is stable, while the chirped temporal soliton is gradually compressed.