Creating stable trapping force and switchable optical torque with tunable phase of light

Area of Science:

• Optics and Photonics
• Nanotechnology
• Microfluidics

Background:

• Light-induced rotation of microscopic objects is key for developing micromotors.
• Controlling position and rotation direction simultaneously without intensity gradients is a significant challenge.
• Existing methods often rely on light's intensity gradient or specific light-matter interactions.

Purpose of the Study:

• To achieve stable optical trapping and switchable optical rotation of nanoparticle (NP)-assembled micromotors.
• To demonstrate control over rotation direction and magnitude using programmed light phase.
• To explore the use of phase gradients in light fields for optical manipulation.

Main Methods:

• Utilizing a circularly polarized flat-top laser beam with imprinted customized phase gradients.
• Trapping and assembling metal NPs into reconfigurable clusters using these phase gradients.
• Modulating phase gradients to control optical torque direction and magnitude.

Main Results:

• Stable optical trapping and reconfigurable cluster formation of metal NPs achieved.
• Direction-switchable and magnitude-tunable optical torque demonstrated on the NP clusters.
• Successful manipulation of micromotors using programmed phase gradients in a light field.

Conclusions:

• The study presents a novel method for reversible optical torque generation in micro/nanomotors.
• Programmed phase gradients in light fields offer precise control over optical trapping and manipulation.
• This technique provides new insights into utilizing the phase of light for advanced optical control.