State-of-the-art microscopes use intense lasers that can severely disturb biological processes, function and viability. This introduces hard limits on performance that only quantum photon correlations can overcome. Here we demonstrate this absolute quantum advantage, achieving signal-to-noise beyond the photodamage-free capacity of conventional microscopy. We achieve this in a coherent Raman microscope, which we use to image molecular bonds within a cell with both quantum-enhanced contrast and sub-wavelength resolution. This allows the observation of nanoscale biological structures that would otherwise not be resolved. Coherent Raman microscopes allow highly selective biomolecular finger-printing in unlabelled specimens, but photodamage is a major roadblock for many applications. By showing that this roadblock can be overcome, our work provides a path towards order-of-magnitude improvements in both sensitivity and imaging speed.
Making sense of the brain network and functions from individual neuronal activity is a challenging task. We developed a data analysis pipeline, combining unsupervised learning and supervised learning methods to reveal some of the intricacies of brain function in zebrafish. We were interested in particular to apply it to the senses of hearing, and balance. Using Optical Tweezers, we manipulated optically and individually each of the four ear stones which reside in the inner ear. Consequently, we simulated sound and acceleration in an alive zebrafish with laser beams. I will present the study of behaviour and neural responses to these stimulations.
Techniques to observe and track single unlabelled biomolecules are crucial for many areas of nano-biotechnology; allowing to shed light on important nanoscale biological processes. Impressive progress has been made over the past few years to extend the sensitivity of such techniques, primarily via evanescent field enhancement. However, such approaches expose the biological system to greatly increased optical intensity levels. Here, we introduce an evanescent biosensor that operates at the fundamental quantum limit. This allows a five order-of magnitude reduction in optical intensity whilst maintaining state-of-the-art sensitivity and enabling quantum noise limited tracking of single biomolecules as small as 3.5 nm.
Interferometry can completely redirect light, providing the potential for exceptionally strong and controllable optical forces. When a beamsplitter combines two fields, the output power is directed via the relative phase between the incident fields. Since the phase changes with beamsplitter displacement, the interference force can be used to stably trap; with displacements as small as (λ/4n) able to completely redirect the light. The resulting change in optical momentum causes an opposing optical force. However, optical forces are most useful for trapping and manipulating small scattering particles. Optical scattering is not generally thought to allow efficient interference; essentially, it appears that small particles cannot act as beamsplitters. As such, optical traps have relied upon much weaker deflection-based forces.
Here we show that efficient interference can be achieved by appropriately structuring the incident light. This relies on Mie scattering fringes to combine light which is incident from different incident angles. This results in a force, which we call the structured interference force, which offers order-of-magnitude higher trap stiffness over the usual Gaussian trap. We demonstrate structured interference force trapping (SIFT) of 10μm diameter silica spheres with a stiffness 20.1 times higher than is possible using Gaussian traps, while also increasing the measurement signal-to-noise ratio by two orders of magnitude. This is demonstrated using only phase control of the incident light, making the technique directly compatible with most existing holographic optical traps. These results are highly relevant to many applications, including cellular manipulation, fluid dynamics, micro-robotics, and tests of fundamental physics.