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An electrical engineer and coauthor of the digital optical phase conjugation experiment described there.^[ref]

Digital optical phase conjugation uses a wavefront sensor and a spatial light modulator to measure an incident field and launch a beam with the opposite spatial wave phase. A phase-only spatial light modulator illuminated uniformly generally does not reproduce the incident wave amplitude as well; exact $\gamma U^{\ast }$ requires the appropriate wave amplitude and polarization of an electromagnetic wave too. The experimentally useful question is how much of the original optical mode can be recovered with the measured and controlled field components.

In 2010, Meng Cui and Changhuei Yang demonstrated digital optical phase conjugation through a prepared multiple scattering sample. They dried mixed-size polystyrene microspheres on cover glass, added immersion oil, and sealed them with another cover glass. A 532 nm laser supplied signal and reference beams. The signal crossed the sample between two objectives; the reference interfered with it on a charge-coupled device. Phase-stepped wave interference recovered the spatial wave phase; a calibrated spatial light modulator imposed its negative on the reference-derived return beam. The reference supplied playback power, without nonlinear mixing pumps. An optical camera read out the recovered signal. With the same sample and a zero-phase spatial light modulator control, the return instead produced a scattering of light pattern. This comparison supports mode recovery by spatial wave phase control, not merely increased illumination. A separate ordinary-mirror control tested source displacements. Finite sampling and collection limited recovery; the system controlled wave phase rather than the complete vector field. These restrictions distinguish demonstrated reconstruction from exact reversal of every scattered component.^[ref]

Online text: pdfs.semanticscholar.org/77e1/3f407ab09f2539523bf8d29acd1048524a2a.pdf

By Meng Cui and Changhuei Yang.

Published in Optics Express 18(4), 3444–3455, by the Optical Society of America. The printed first-page footer gives online publication on 2 February 2010; the issue footer gives 15 February 2010. Semantic Scholar hosts the linked PDF copy.

DOI: doi.org/10.1364/OE.18.003444

Publication record: pubmed.ncbi.nlm.nih.gov/20389354/

Cited passages: §2, Figure 1, pp. 3446–3447, recording and playback geometry; §§3.1–3.2, Figures 2–3, pp. 3447–3450, 532 nm source, sensor/modulator arrangement and calibration; §4.1, Figure 4, p. 3450, readout; §4.2, Figure 6(e–f), pp. 3451–3452, ordinary-mirror displacement control; §§5.1–5.2, Figure 7(a–c), pp. 3452–3453, prepared bead sample, conjugate return and zero-phase control.

Meng Cui and Changhuei Yang demonstrated digital optical phase conjugation through a multiple scattering sample. A charge-coupled device measured a transmitted light field by wave interference with a reference. A calibrated spatial light modulator then imposed the opposite spatial wave phase on the returning beam. Comparing this return with a zero-phase control showed recovery of the original optical mode. The method separated field measurement from playback and made finite sampling and phase-only control explicit limits on reconstruction.^[ref]

An optical physicist and coauthor of the digital optical phase conjugation experiment described there.^[ref]