Development of High-Efficiency Beam Converter for Ultrafast Spatio-Temporal Control of Light Waves

When two optical vortices with different topological charges mutually interfere, azimuthally periodic structure called a ring-shaped optical lattice is formed. The petal-like beam profile can be flexibly rotated by controlling the intermodal phase difference, which offers us rotational degree of freedom in applications such as optical ma-nipulations of micro/nano particles and micro machines. However, their maximum rotational frequency has been limited to GHz regime owing to their response time or bandwidth. Recently, we succeeded in drastically increasing the rotational frequency up to THz regime by introducing a new technique based on spatial mode multiplexing of chirped optical-vortex pair.