Fibre-integrated Picosecond mid-Infrared Laser (fPIRL) for biomolecular analysis

Lead Research Organisation: Imperial College London
Department Name: Physics


The mid-infrared band of the electromagnetic spectrum has huge potential in healthcare technologies. Many biological molecules exhibit very strong absorption of radiation (light) in this region. This absorption depends strongly on matching the wavelength (colour) of the light to the stretching of the molecular bonds, unique to each molecule. For example, water absorbs radiation at a mid-infrared wavelength of 2.94 um nearly 100,000 times more strongly than a near-infrared wavelength of 1 um.

A laser is an intense, highly directional, and monochromatic beam of radiation. The potential of mid-infrared lasers at 2.94 um as medical tools was recognised early on, due to the high-water content of biological tissue (>70%). Focussing a 2.94 um laser on tissue results in highly efficient absorption of the radiation in a very localised area. The subsequent rapid heating in this area causes the tissue to vaporise into a gas (ablation), resulting in an ultra-precise method of removing tissue, e.g. for use as laser scalpels or biopsy replacements.

There are, however, a lack of ultrafast mid-infrared lasers with pulse durations shorter than 1 nanosecond (a billionth of a second) suitable for tissue ablation. Existing ultrafast mid-infrared commercial lasers do not have enough energy to initiate ablation, are often too large and complex to be deployed outside of specialist laser laboratories, or have poor beam qualities leading to large beam sizes on the sample (poor spatial resolution). As a result, the standard approach to 2.94 um tissue ablation is to use more widely available lasers (Er:YAG/Nd:YAG OPO) with longer pulses. However, the effect of these longer pulses on tissue can be highly problematic, causing tissue carbonisation (burning) and necrosis (cell-death) in surrounding cells, which can be avoided when using picosecond (ultrafast) pulses.

In this project, I will create a compact, robust, fibre-integrated picosecond mid-infrared laser (fPIRL) platform. The platform will be based on a novel cascaded nonlinear wavelength conversion scheme, employing a combination of advanced fibre optic technology and new mid-infrared materials to create a completely fibre-integrated source suitable for wide deployment in non-specialist laboratories and clinics. The fPIRL platform will be employed as an ultra-precise laser scalpel, removing minute volumes of tissue for subsequent analysis with mass spectrometry. The tool will be much less destructive and much more precise than existing techniques.

The team assembled crosses industry and academia, including materials scientists, laser physicists, analytical chemists, and systems medicine specialists. Together, we will enable significant advances in various biomolecular analysis techniques. The proposed single-cell resolution molecular mapping setup will help drive improvements in cancer tumour removal surgeries. Our fibre-delivered source will underpin future robotic surgical interventions in hard-to-reach surgical sites. With our long-wavelength source (6 um) we aim to reveal different biological fingerprints, improving diagnoses for certain diseases, than with existing ablation techniques.

This project will create a new photonics-based healthcare technologies tool. The tool will enable significant advances in disease diagnosis and intervention, through advances in biomolecular analysis techniques suitable for both research and in-vivo applications. These advances will ultimately improve patient outcomes in the UK for the NHS, leading to a healthier, happier, and more productive society. Beyond this project, the fPIRL could be used for any precision surgical intervention, cultural preservation in ancient art, and polymer processing for biological implants.


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