Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Jan 30:7:41384.
doi: 10.1038/srep41384.

Time-reversing a monochromatic subwavelength optical focus by optical phase conjugation of multiply-scattered light

Jongchan Park  1   2 , Chunghyun Park  1   3 , KyeoReh Lee  1   2 , Yong-Hoon Cho  1   3 , YongKeun Park  1   2
Affiliations

Time-reversing a monochromatic subwavelength optical focus by optical phase conjugation of multiply-scattered light

Jongchan Park et al. Sci Rep. .

Abstract

Due to its time-reversal nature, optical phase conjugation generates a monochromatic light wave which retraces its propagation paths. Here, we demonstrate the regeneration of a subwavelength optical focus by phase conjugation. Monochromatic light from a subwavelength source is scattered by random nanoparticles, and the scattered light is phase conjugated at the far-field region by coupling its wavefront into a single-mode optical reflector using a spatial light modulator. Then the conjugated beam retraces its propagation paths and forms a refocus on the source at the subwavelength scale. This is the first direct experimental realisation of subwavelength focusing beyond the diffraction limit with far-field time reversal in the optical domain.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. Schematic diagram of reversing a sub-wavelength light source.
(a) Conventional mirror. (b) Phase-conjugation mirror. (c) Phase-conjugation mirror with random nanoparticles.
Figure 2
Figure 2. Experimental setup.
(a) Digital optical phase conjugation mirror. (b) Modified near-field scanning microscopy. SMF: single mode fiber, SPCM: single photon counting module, P: polarizer, SLM: spatial light modulator, PMT: photomultiplier tube, FM: flip mirror, OL: objective lens, CCD: charge-coupled device.
Figure 3
Figure 3
(a) Subwavelength focus is made by illuminating NSOM probe tip. Inset, bottom view of the NSOM probe aperture. (b) Far-field time-reversal of the subwavelength focus in a homogeneous environment. (c) Using zirconium dioxide random nanoparticles, a near-field focus is regenerated by far-field time-reversal of multiply scattered light. (d) Intensity distributions of the foci. Red dash-dotted line, an ensemble average of far-field foci. Green solid line, near-field foci (n = 18). Black thick solid line, an ensemble average of the near-field foci.
See this image and copyright information in PMC

References

    1. Fink M. et al.. Time-reversed acoustics. Rep. Prog. Phys. 63, 1933 (2000).
    1. Lerosey G. et al.. Time reversal of electromagnetic waves. Phys. Rev. Lett. 92, 193904 (2004). - PubMed
    1. Potton R. J. Reciprocity in optics. Rep. Prog. Phys. 67, 717 (2004).
    1. Kogelnik H. Holographic image projection through inhomogeneous media. Bell. Syst. Tech. J. 44, 2451–2455 (1965).
    1. Yariv A. & Pepper D. M. Amplified reflection, phase conjugation, and oscillation in degenerate four-wave mixing. Opt. Lett. 1, 16–18 (1977). - PubMed

Publication types

LinkOut - more resources