Orbital Angular Momentum in Optics

Light carries not only energy but also angular momentum, and since the early 1990s physicists have recognized that a beam's spatial structure can encode orbital angular momentum (OAM) independent of its polarization. Beams twisted into helical wavefronts — such as Laguerre-Gaussian modes — can exert measurable torques on microscopic objects, enabling optical tweezers to rotate, sort, and trap particles with a precision unattainable by conventional focused beams. The same helical modes form a theoretically unbounded set of orthogonal states, making them attractive carriers of information in quantum communication and high-capacity classical data links. Active research is now pushing toward tighter control at the nanoscale through plasmonic near-field traps, as well as toward reliable generation and detection of OAM states in integrated photonic and microfluidic platforms where real-world noise and fabrication imperfections remain significant challenges.

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Keywords

Optical ManipulationOrbital Angular MomentumLight BeamsOptical TweezersStructured LightPlasmonic Nano-optical Tweezers