Great effort has been launched into the modification of microstructures by various techniques because of the interest in the field of ultra-short pulsed light–matter interactions, as well as the technological application in the fabrication of three dimensional optical devices. The size and shape of microstructures can be changed by adjusting laser parameters including wavelength, polarization, pulse width, pulse energy, and pulse interval.

Researchers at State Key Laboratory of High Field Laser Physics——Shanghai Institute of Optics and Fines Mechanics (SIOM/China) report that femtosecond-laser-induced microstructures can be inverted by tuning the refractive index of the immersion liquid of the objective. By putting a water layer and an 1-bromonaphthalene layer on the glass sample, they can induce microstructures with similar shape but opposite directions. Moreover, the elemental distribution in the induced structures can also be inverted.[ OPTICS LETTERS. Vol. 36, No. 11,2125]

They have succeeded in inverting the femoto-second laser-induced microstructure and elemental distribution by changing the RIC between the immersion liquid and the glass sample. The simulation of laser intensity distribution along the laser propagation direction indicates that the interface spherical aberration effect is responsible for the reversal of microstructures and elemental distribution. This technique will be useful for the fabrication of three-dimensional optical devices inside transparent materials.