Fluorescence Lifetime Imaging Microscopy (FLIM)

Fluorescence Lifetime Imaging Microscopy (FLIM) is a key tool within the microscopy community whereby the exponential decay rate of fluorescent markers is used as a probe for local changes in e.g. temperature, pH, viscosity on a sub-cellular scale. In the following, we will discuss recent advancements utilising quantum effects to enhance the capabilities of FLIM.
We will discuss how FLIM can be made more accessible by removing the expensive pulsed laser systems and instead exploiting the temporal correlations between entangled photon pairs to gain access to lifetime information. This not only significantly reduces the cost of FLIM but also introduces the availability for wavelength tunability. We demonstrate this approach by investigating by looking at the response of Light Harvesting Complex 2 at the single photon level, mimicking the environment where photosynthesis naturally occurs on timescales pertinent to practical microscopy.
Furthermore, the time resolution of FLIM systems is determined by the detection electronics to of order 100 picoseconds. Two-photon interferometry, on the other hand, provides an alternative method for timing the arrival of photons down to femtosecond resolution with the benefit of being accessible with incoherent light. We show this approach’s ability to resolve the lifetimes of picosecond fluorescent markers that are typically inaccessible to commercial FLIM systems and discuss progress extending the technique towards imaging.