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Joined 2026-09-21 Message
Incoming links: John Ernst Bjorkholm
Single-beam gradient trapping experiment 2026-10-18
In 1986, Arthur Ashkin, Joseph Martin Dziedzic, John Ernst Bjorkholm and Steven Chu used spatially filtered argon laser light, a water-immersion objective of numerical aperture , and a water-filled glass cell. An auxiliary beam loaded large glass beads; dispersed small particles entered by Brownian motion. A side microscope and scattering of light detector provided readout. Their Fig. 1 shows a bead below the focus with about . On p. 290, silica size was inferred by scattering against a latex standard; translating the cell imposed fluid drag. These observations support single-beam confinement, while inferred size depends on the scattering model.[ref]
Observation of a single-beam gradient force optical trap for dielectric particles by Arthur Ashkin and others. A. Ashkin, J. M. Dziedzic, J. E. Bjorkholm and Steven Chu, Observation of a single-beam gradient force optical trap for dielectric particles, 1986, pp. 288–290, Figs. 1–2 and final experimental paragraphs
A loading beam can help bring a bead into the capture region without supplying its subsequent confinement. Distinguish loading, holding and sensing when interpreting an apparatus drawing. The following optical trap position readout is a proposed calibration arrangement; its detector layout is not a reconstruction of this historical experiment.