Researcher(s)
- Alexander Hutchinson, Physics, University of Delaware
Faculty Mentor(s)
- Aqiq Ishraq, Materials Science and Engineering, University of Delaware
- Muhammad Hassan Shaikh, Physics and Astronomy, University of Delaware
- Chitraleema Chakraborty, Materials Science and Engineering, Physics and Astronomy, University of Delaware
Abstract
Scanning fluorescence microscopy, like confocal microscopy, is a form of high-resolution imaging that is used to study material properties by focusing a beam of light onto a portion of a sample and analyzing the light coming from that portion [1]. To study the entire sample’s properties, we then have to scan one point at a time to build a full image of the sample [1]. To create high resolution images the point of light used to image the sample must have a clean mode, meaning that the beam is single-mode. This can be accomplished using a spatial filter also known as a mode cleaner. Collectively, the spatial filter designed in this project utilizes an aspheric lens (f = 60 mm) to focus a 532 nm wavelength beam of light into a 10-μm pinhole and then collimates the light using a plano-convex lens (f = 40 mm). The level of mode cleaning achieved can be measured by the beam profile after the spatial cleaner as well as the image produced on camera by the samples reflected light, which is focused, clear, and circular with some symmetric rings around its circumference. The reflected light from the sample is then coupled to a multimode fiber optic cable (NA = 0.22), rather than a single-mode like in confocal microscopy. This is because multi-mode fibers lose less power then a single-mode fiber. The reflected light is used to align the emitted light from the sample into an avalanche photodiode (APD), as the emitted light is difficult to monitor during alignment. The APD measures the intensity of light at every point and creates a high-resolution image, the coupling of light to the fiber needs to be maximized for the better resolution of the image. Our system achieved ~85% efficiency of light coupled to the optical fiber.
[1] Elliott AD. Confocal Microscopy: Principles and Modern Practices. Curr Protoc Cytom. 2020 Mar;92(1):e68. doi: 10.1002/cpcy.68. PMID: 31876974; PMCID: PMC6961134.