Characterization of gap-plasmon based metasurfaces using scanning differential heterodyne microscopy

Abstract

Optical phase-gradient metasurfaces, whose unique capabilities are based on the possibility to arbitrarily control the phase of reflected/transmitted light at the subwavelength scale, are seldom characterized with direct measurements of phase gradients. Using numerical simulations and experimental measurements, we exploit the technique of scanning differential heterodyne microscopy (SDHM) for direct phase and amplitude characterization of gap-plasmon based optical metasurfaces. Two metasurface configurations utilizing the third-order gap surface plasmon (GSP) resonance, representing a binary grating and linear phase gradient, are experimentally characterized with the SDHM operating at the light wavelength of 633 nm. Comparing the experimental performances of these GSP metasurfaces with those expected from the phase and amplitude profiles reconstructed from the SDHM measurements, we verify the efficiency and accuracy of the developed SDHM characterization approach for direct inspection of GSP reflective metasurfaces.

Superresolution in phase image of π-phase step on plasmonic metasurface using differential heterodyne microscope

“…The sample was fabricated using electron-beam lithography and lift-off technique, as described in detail in Ref. 37. Then the entire grating area 80×80 μm was covered with a dielectric film with a thickness td and refractive index nd (not shown in Fig.…”

“…Recently, the study of phase objects based on plasmonic metasurfaces has become widespread, including for various applications in optical radiation control systems and elements, such as terahertz absorbers, nonlinear integrated optics, thermal emission control, and focusing elements 31 – 38 The question arises whether it is possible to use this promising technology to fabricate phase objects suitable for observing the superresolution effect in edge detection. The answer on this question is not obvious, since the characteristic size of the unit cell of the metasurface 35 – 37 is comparable with the wavelength of optical radiation and with the size of the focused probing spot of the microscope.…”

“… – 38 The question arises whether it is possible to use this promising technology to fabricate phase objects suitable for observing the superresolution effect in edge detection. The answer on this question is not obvious, since the characteristic size of the unit cell of the metasurface 35 – 37 is comparable with the wavelength of optical radiation and with the size of the focused probing spot of the microscope. Thus, the surface to be investigated can significantly deviate from the designed one and this, in turn, can affect the superresolution effect.…”

“…We studied a composite structure based on a plasmonic metasurface with an additional dielectric film. For a plasmonic metasurface based on third-order plasmon resonance, the local amplitude-phase reflection characteristics are determined by the geometric parameters of the unit cell microresonators, 36 – 38 which give an additional degree of freedom to design microdevices with the desired reflection characteristics. Thus, the purpose of this work was to investigate the superresolution effect in the phase image of a metasurface edge with a phase jump close to π and the possibility of controlling the width of the phase response function in this case.…”

Complex wavefront sensing based on coherent diffraction imaging using vortex modulation

“…Measuring the complex wavefront from recorded intensity images is demanded in various fields, including microscopy 1 , 2 , optical element characterization 3 , 4 and imaging through scattering media 5 , 6 . Due to the extremely high frequency of light, only the intensity is directly recorded by available sensors.…”