Planar device-enabled speckle illumination for dark-field label-free imaging beyond the diffraction limit

Area of Science:

• Optical Microscopy
• Nanophotonics
• Biomedical Imaging

Background:

• Dark-field microscopy enhances unstained sample contrast but is limited by the optical diffraction limit and requires bulky, precisely aligned components.
• Existing methods struggle to overcome resolution limits and necessitate complex optical systems.

Purpose of the Study:

• To introduce a planar photonic device for dark-field illumination that overcomes the optical diffraction limit.
• To improve optical resolution and enable high-contrast, label-free imaging of challenging samples.
• To provide a simpler, more efficient alternative to traditional dark-field microscopy.

Main Methods:

• Fabrication of a planar device comprising random distribution fibers, a scattering layer, a one-dimensional photonic crystal (1DPC), and a metallic film.
• Utilizing the device to generate random speckles and a hollow cone of light for dark-field illumination.
• Investigating the generation of random evanescent speckles by tuning incident wavelength for super-resolution imaging.

Main Results:

• Achieved a 1.55-fold improvement in spatial resolution with high-contrast, label-free imaging.
• Demonstrated optical surface imaging beyond the diffraction limit by generating random evanescent speckles.
• The planar device functions as a substrate for conventional microscopy, simplifying the optical system.

Conclusions:

• The developed planar photonic device offers a breakthrough in dark-field microscopy, enhancing resolution and contrast.
• This technique provides a pathway for imaging previously invisible samples without complex optical setups.
• The study expands the potential applications of dark-field microscopy in biological research, material science, and medical diagnostics.