Free-space information transfer using light beams carrying orbital angular momentum.

Area of Science:

• Optics and Photonics
• Quantum Information Science
• Secure Communication

Background:

• Orbital angular momentum (OAM) offers a novel degree of freedom for encoding information in light.
• Spatial light modulators (SLMs) are key components for manipulating the OAM states of light beams.
• Understanding the security implications of OAM-based information transfer is crucial for future communication technologies.

Purpose of the Study:

• To demonstrate the secure transfer of information encoded in orbital angular momentum (OAM) states.
• To experimentally investigate the eavesdropping resistance of OAM-based communication.
• To analyze the impact of measurement uncertainties on OAM detection.

Main Methods:

• Utilizing spatial light modulators (SLMs) for preparing and measuring eight distinct OAM states.
• Encoding information onto a laser beam using OAM states.
• Simulating eavesdropping attempts by sampling the beam off-axis.

Main Results:

• Information encoded in OAM states was successfully transferred between transmitter and receiver units.
• Off-axis sampling of the OAM beam resulted in inherent measurement uncertainties due to angular restrictions and lateral offsets.
• These uncertainties demonstrate the inherent resistance of OAM encoding to eavesdropping.

Conclusions:

• OAM-based information transfer exhibits intrinsic security features against eavesdropping.
• Experimental insights into the effects of beam aperturing and misalignment on OAM measurements were obtained.
• The study experimentally validates the uncertainty relationship for OAM measurements in the context of secure communication.