Microsphere‐Aided Super‐Resolution Scanning Spectral and Photocurrent Microscopy for Optoelectronic Devices

Abstract

Dielectric microspheres naturally possess unique optical properties by which the light's focus and confinement can be manipulated on a microscale. Combining microspheres and optical or Raman microscopy, super‐resolution imaging beyond the diffraction limit and enhancement of Raman signals are demonstrated to provide abundant spectroscopic information on materials. However, microsphere‐aided super‐resolution scanning photocurrent imaging remains challenging to date. Here, based on the photonic nanojet mechanism, a super‐resolution photocurrent and spectral microscopy equipped with a scanning tip with silica dielectric microspheres are presented. With such microsphere‐aided microscopy, order of magnitude enhancements for single‐point Raman and photoluminescence signals can be achieved, and the spatial resolutions for photocurrent and spectral mapping surpass the best resolution of the original confocal system restricted by the diffraction limit. This versatile system enables correlative super‐resolution spectral and photocurrent imaging, serving as a reliable tool for comprehensively understanding and uncovering the optoelectronic properties of materials.

Ultrasensitive Trace Detection of Dye Molecules Based on Scanning Microsphere-Coupled Surface-Enhanced Raman Spectroscopy

“…The laser power was kept at 1 mW (refer to Figure S4 in the Supporting Information for laser power-dependent Raman spectra of CV), and the accumulation time was 20 s for every spectrum. Before every data acquisition, the confocal Raman system was well collimated and the intensity of the Raman peak at 520 cm −1 from silicon By employing a scanning 10 μm-diameter SiO 2 microsphere to form the SMC-SERS system, 27 the Raman intensities of all the characteristic CV peaks show a considerable increase at all concentrations (Figure 2c). The vibrational modes of CV at a concentration of 10 −8 M remain prominent, indicating that the detection limit has not yet been reached.…”

“…To construct the SMC-SERS system (Figure 1c), the silica (SiO 2 ) microsphere was attached to a unique AFM cantilever (refer to Methods for further details). 27 Throughout the spectral measurement, the Raman laser beam was adjusted to pass through the silica dielectric microsphere, converging the incident light to generate a focal point on the backlight side of the microsphere onto the sample surface. At the same time, the laser of the AFM system was incident on the center of the cantilever.…”

“…By employing a scanning 10 μm-diameter SiO 2 microsphere to form the SMC-SERS system, the Raman intensities of all the characteristic CV peaks show a considerable increase at all concentrations (Figure c). The vibrational modes of CV at a concentration of 10 –8 M remain prominent, indicating that the detection limit has not yet been reached.…”

Optical superresonance and generation of extreme magnetic fields in mesoscale dielectric spheres

“…To sum it up, we can conclude that the weakly dissipative mesoscale dielectric spherical particles make it possible to efficiently control the magnetic and electric components in a simultaneous way, support both the non-resonant field confinement mode (photonic jet and hook formation [48][49] ) and the super-resonant effect different from the whispering gallery mode [50][51][52] . The presence of a number of interesting applications in optics, terahertz, acoustics and plasmonics (sensitivity of detectors, pressure sensor, laser scalpel, optical cloaking, transport of particles over an obstacle, sorting and aggregation of nanoparticles, photolithography, optical switch, THz communications, superlens, acoustic and optical superresolution images [53][54][55][56] , etc.) indicates that in optics, terahertz, acoustics and plasmonics a new promising direction "mesotronics" arose.…”

Narrow nano-beam generation inside of silicon photonic chip with a hemi-cylinder

“…The PNJ was firstly proposed using a computational study of optical scattering by infinite cylinders in [4]. Then, numerous investigations are carried out to improve the properties of PNJs [5][6][7][8][9] and explore applications of PNJs in enhancing Raman scattering [10][11][12], nanoparticle manipulation [13][14][15], optical super-resolution imaging [16][17][18] and structured light engineering [19]. Among these, obtaining narrow beam waist of PNJs is very important.…”