PhD Studentship: Building the world's most advanced polarisation-resolved nonlinear microscope

Structured light for full 3D vectorial control of the focal field — and the first true 3D readout of molecular organisation in tissue. During this project you will lead the design, build and programming an optical microscope that does something no existing instrument can: Shape the full 3D vector of a light field at the focus of an objective lens and use it to read out how biomolecules are organised in three dimensions. The microscopy technique you will begin working on is polarisation-resolved second-harmonic generation (pSHG): a fast, label-free nonlinear technique that is the gold standard for imaging collagen in living tissue. Conventional pSHG has a fundamental blind spot — its excitation field lies in the image plane, so it is insensitive to structure tilted out of that plane.  

Using a spatial light modulator to sculpt both the wavefront and the polarisation, you will engineer a longitudinal (z-polarised) field in a high-numerical-aperture focus and controllably drive SHG from out-of-plane collagen fibrils for the first time. This novel capability will allow you to study the organisation of the 3D collagen matrix in unprecedented detail.  What you'll do, and the skills you'll gain: Optical design and hands-on alignment of an ultrafast nonlinear microscope; SLM/DMD wavefront and polarisation shaping; vectorial focal-field modelling; the Jones, Stokes and Mueller formalisms; nonlinear optics; and Python for instrument control and image analysis — with scope for machine-learning approaches to the vectorial inverse problem.  

Why it matters: collagen's 3D architecture sets the mechanical behaviour of tissue — the same molecule, type I collagen, builds both the transparent corneal lattice and the load-bearing tendon. That architecture, and its breakdown in disease, has never been measurable in true 3D. An instrument that reads it directly is a new tool for biophysics, biomechanics and structural biology. You will be based in the Physics department at the University of Exeter. The supervision team includes Prof Dave Phillips (structured light) and Dr Ben Sherlock (polarisation-resolved nonlinear microscopy).

Funded by: EPSRC Engineering and Physical Sciences Research Council 

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