Where does trapping collide?

In optics, trapping is the confinement of a microscopic particle at the focus of a tightly focused laser beam, where the gradient of the optical field pulls the particle toward the brightest point and holds it against Brownian motion, the principle of optical tweezers. Ashkin and colleagues' 1986 Observation of a single-beam gradient force optical trap for dielectric particles demonstrated that a single focused beam could stably trap particles from tens of nanometres to micrometres. The referent is a balance of radiation-pressure forces that cages an object in free space, measured by trap stiffness and escape force, entirely distinct from an overlapped ink edge or a defect state in a crystal.[1]

Unit

The trap stiffness and the force holding a particle at the focus

Recovery means

Not applicable

Measured by

Quantified by the trap stiffness (force per displacement) and the maximum escape force, from the particle's thermal motion in the trap

In semiconductor physics, trapping is the capture of a mobile electron or hole by a localized defect or impurity state whose energy lies within the band gap, which immobilizes the carrier until it is thermally re-emitted or recombines. Shockley and Read's 1952 Statistics of the recombinations of holes and electrons gave the kinetic theory of such trap-mediated capture and recombination that underlies carrier lifetime in real devices. The referent is a defect-state capture event governing how long carriers survive in a material, measured by capture cross-sections and trap densities, and it is unrelated to a laser cage or a printed color overlap.[2]

Unit

The capture cross-section and density of trap states in the band gap

Recovery means

Not applicable

Measured by

Characterised by trap density, capture cross-section, and emission rate from deep-level transient spectroscopy and carrier-lifetime measurements