An apparatus (100) for carrying out microsphere-enhanced spectroscopy on a sample (15) is shown. Illumination of the sample (15) is provided by an illumination laser (11). A microsphere (1) is attached to the front lens of the objective lens assembly (2) by a column (13) of optically clear material. This allows the illumination radiation to be focused on the sample (15). Scattered radiation from the illuminated area is collected via the microsphere (1) and the objective lens assembly (2). The scattered radiation passes through the objective lens assembly (2), an optional adjustable pinhole (3) and dichroic mirror (4) to a notch filter (8). The filtered scattered radiation is incident upon an optical grating (6), and subsequently a detector. The provision of the microsphere (1) on a column (13) of optically clear material ensures that it can be retained in a desired alignment and at a desired separation from the front lens of the objective lens assembly (2).

Improvements in or Relating to Microsphere-Enhanced Spectroscopy

As water is normally used as the immersion medium in optically trapped microsphere microscopy, the high-refractive-index barium titanate glass (BTG) microsphere shows a better imaging performance than the low-index polystyrene (PS) or melamine formaldehyde (MF) microsphere, but it is difficult to be trapped by single-beam optical trapping due to its overly high refractive index. In this study, coated BTG microspheres with a PS coating have been computationally explored for the combination of optical trapping with microsphere-assisted microscopy. The PS coating thickness affects both the optical trapping efficiency and photonic nanojet (PNJ) property of the coated BTG sphere. Compared to the uncoated BTG sphere, the coated BTG sphere with a proper PS coating thickness has a highly improved trapping efficiency which enables single-beam optical trapping, and a better PNJ with a higher optical intensity Imax and a narrower full width at half maximum (FWHM) corresponding to better imaging performance. These coated BTG spheres also have an advantage in trapping efficiency and imaging performance over conventional PS and MF spheres. The coated BTG microsphere is highly desirable for optically trapped microsphere super-resolution microscopy and potentially beneficial to other research areas, such as nanoparticle detection.

Coated High-Refractive-Index Barium Titanate Glass Microspheres for Optically Trapped Microsphere Super-Resolution Microscopy: A Simulation Study

We have demonstrated a novel, non-contacting super resolution imaging setup using optical tweezers designed in-house. We can resolve large areas of samples using laser trapped polystyrene microsphere scanning with resolutions below the diffraction limit.

Optical Tweezers Microsphere-lens Super Resolution Imaging System

We have demonstrated an objective lens attachment comprising a single microsphere lens for achieving super resolution virtual imaging. We have resolved large areas with resolutions below the diffraction limit through contactless sample scanning.

Chih-Hua Ho

Papers

Optical Tweezers Microsphere-lens Super Resolution Imaging System

Optical Scanning Nanoscope with Microsphere Attached Objective Lens for Super Resolution 3D Virtual Imaging