Mapping of phase singularities with spiral phase contrast microscopy

Area of Science:

• Microscopy
• Materials Science
• Optics

Background:

• Spiral phase contrast (SPC) microscopy typically offers edge-enhancement independent of phase vortex filter helicity.
• Layered specimens, such as mica and crystallized organic substances, can contain screw-dislocations.

Purpose of the Study:

• To demonstrate that SPC microscopy can reveal screw-dislocations in layered specimens.
• To develop a method for mapping phase singularities using filter helicity dependence.

Main Methods:

• Utilizing a spatial light modulator (SLM) to encode a binary off-axis hologram as a vortex filter in the Fourier plane.
• Employing a binary grating to generate two image waves with opposite helicity.
• Simultaneously recording two images with opposite handedness on a camera chip.

Main Results:

• The intensity distribution in SPC microscopy images becomes dependent on the rotational direction of the phase vortex filter for layered specimens with screw-dislocations.
• This helicity dependence allows for the mapping of phase singularities.
• The distribution of dislocations in transparent samples was mapped in a single camera exposure.

Conclusions:

• SPC microscopy, when adapted with helicity-dependent vortex filters, provides a novel method for mapping screw-dislocations in layered materials.
• This technique enables the visualization of phase singularities, offering insights into material topography.
• The simultaneous recording capability enhances efficiency for dislocation mapping.