3D Super-Resolution Optical Profiling Using Microsphere Enhanced Mirau Interferometry

Abstract

We present quantitative three dimensional images of grooves on a writable Blu-ray Disc based on a single objective Mirau type interferometric microscope, enhanced with a microsphere which is considered as a photonic nanojet source. Along the optical axis the resolution of this microsphere assisted interferometry system is a few nanometers while the lateral resolution is around 112 nm. To understand the physical phenomena involved in this kind of imaging we have modelled the interaction between the photonic jet and the complex disc surface. Agreement between simulation and experimental results is demonstrated. We underline that although the ability of the microsphere to generate a photonic nanojet does not alone explain the resolution of the interferometer, the nanojet can be used to try to understand the imaging process. To partly explain the lateral super-resolution, the potential role of coherence is illustrated. The presented modality may have a large impact on many fields from bio-medicine to nanotechnology.

High Resolution Surface Metrology Using Microsphere‐Assisted Interference Microscopy

“…. We present here some of our own results for simulations in air using Comsol Multyphysics software . The simulation consists of two steps.…”

“…But being based on optical microscopy, the effects of light diffraction limit the lateral resolution to λ/2, which even at short visible wavelengths is over two orders of magnitude worse than the axial resolution. Recently, several groups succeeded in combing microsphere imaging with interferometry to considerably reduce this factor . As in 2D imaging, a microsphere is first introduced on the sample in front of the interference objective in order to perform the super‐resolution effect.…”

“…Mirau objective (NA = 0.5, white light, λ 0 = 560 nm) measurement of Blu‐ray® disc lines (minimum feature size observable 112 nm, 14–22 nm high) in air with 11 μm melamine formaldehyde microspheres ( n = 1.68). Reproduced under the terms of a Creative Commons Attribution 4.0 International License . Copyright 2017, The Authors, published by Springer Nature.…”

“…Nonetheless, it has been frustrating that while the axial resolution is so high, the lateral resolution has remained limited by diffraction to values that are several orders of magnitude worse as in classical microscopy, even by working in the near UV . Recently, several teams have succeeded in reducing this difference in scale by combining microsphere‐assisted microscopy with interferometry to greatly improve the lateral resolution in surface roughness measurement . Performing interferometry through the glass microsphere allows surface profiling with improved lateral resolution.…”

Illumination conditions in microsphere‐assisted microscopy

“…Although the phenomenon of microsphere‐assisted microscopy is still not fully explained and the claimed resolution values are debatable (Allen et al ., ), several experimental results and computer simulations have not only determined the role of evanescent waves (Ben‐Aryeh, ), the influence of the surrounding medium (Yao et al ., ; Darafsheh, ) and the effect of the coherence (Maslov & Astratov, ; Perrin et al ., ), but also improved the field of view using stitching techniques (Wang et al ., ; Huszka et al ., ). Moreover, microsphere‐assisted microscopy has been successfully combined with interferometry for the three‐dimensional (3D) topography reconstruction of nanostructures (Wang et al ., ; Perrin et al ., ; Kassamakov et al ., ) or cell morphology (Aakhte et al ., ), and with dark‐field illumination for the imaging of translucent biological samples (Perrin et al ., ).…”