Femtosecond Laser Trapping for Nanoparticle Manipulation

Nanoparticle manipulation has emerged as a crucial technology in fields ranging from materials science to biomedicine. Traditional optical trapping techniques using continuous-wave (CW) lasers have been widely employed for manipulating micro- and nanoparticles. However, the advent of femtosecond laser technology opens up new possibilities for nanoparticle trapping with unprecedented precision, reduced thermal effects, and enhanced control over nonlinear optical processes. Femtosecond laser pulses, with their ultrashort durations and high peak intensities, offer unique advantages for the manipulation of nanoparticles, enabling applications in nanoscale fabrication, targeted drug delivery, and molecular assembly. We explore the use of femtosecond laser trapping for precise nanoparticle manipulation, studying its potential to achieve superior spatial control and minimal photodamage.

Optical trapping, also known as optical tweezing, has been a powerful tool for manipulating small objects using light since its inception. Typically, optical tweezers utilize a tightly focused continuous laser beam to generate a gradient force that can trap and move particles ranging from microns to nanometers in size. However, CW lasers can induce significant heating and photodamage, particularly when applied to nanoscale systems. This limits their utility in applications requiring delicate manipulation of biological samples or heat-sensitive nanomaterials.

Femtosecond lasers offer a solution to these challenges by delivering energy in ultrashort bursts, significantly reducing heat accumulation. Furthermore, femtosecond laser pulses enable access to nonlinear optical phenomena such as two-photon absorption and second-harmonic generation, which can be exploited for more versatile manipulation techniques. By leveraging the high peak intensities of femtosecond lasers, this research seeks to achieve precise, efficient, and low-damage trapping of nanoparticles. The ability of femtosecond pulses to trap smaller nanoparticles and maintain stability in the trap will be demonstrated and compared with CW lasers. We also show that by using thermal lens studies, the heating effects induced by both femtosecond and CW lasers can be evaluated.