Parametric control of a diffractive axicon beam rider.

Area of Science:

• Optics and Photonics
• Nanotechnology
• Aerospace Engineering

Background:

• Laser beam riders are optical structures designed for attraction to the optical axis and propulsion via radiation pressure.
• These structures are fundamental to the development of laser-driven light sails for space propulsion.
• Understanding the dynamics of these structures is key to optimizing laser-based propulsion systems.

Purpose of the Study:

• To experimentally investigate the restoring force of a diffractive axicon film when displaced from the optical axis.
• To analyze the effects of continuous and modulated illumination on the motion of the axicon film.
• To explore the potential for parametric gain and damping in laser-driven optical systems.

Main Methods:

• A thin diffractive axicon film with a 12.7µm period was fabricated from photopolymer.
• The axicon grating was suspended in a vacuum torsion oscillator for precise motion measurement.
• Irradiation was performed using a 1.5 W near-infrared laser, with modulation at a 38s period.

Main Results:

• The diffractive axicon film exhibited a natural restoring force when its axis was displaced from the optical axis.
• Continuous laser illumination resulted in harmonic motion of the axicon.
• Modulated laser illumination demonstrated both parametric gain and parametric damping effects.

Conclusions:

• Optical momentum change of diffracted light is responsible for the observed restoring force.
• Modulated illumination offers a method to control and enhance the dynamics of laser beam riders.
• These findings have implications for the design and control of laser-driven light sails and optical propulsion systems.