Ultrafast pulsed laser plasma fabrication of erbium doped thin film sensors

Erbium (Er3+) ions have been extensively used in the field of integrated photonics due to it's characteristic fluorescence properties which can be used to amplify the optical signal in fibre based optical communication systems. In this study, novel materials were developed by doping Er3+ ions in glass polymer (GP) superlattice coated on a silicon substrate to investigate its application as an infrared (IR) sensor. The conventional IR detectors are classified as thermal detector and photonic detectors. The conventional photonic detector has better sensing capabilities however, they are required to be cooled down to 77 K for sensing IR radiations. Thus the current requirement is to develop uncooled IR detector which can sense minute changes in the temperature. The initial studies show that GP superlattice coated tipless cantilevers are able to sense changes in temperature with a resolution of 2 mK per nm deflection of the cantilever. The second part of the study was to dope Er3+ ions with or without Ytterbium (Yb3+) ions as a co-dopant in fused silica for glucose sensing. The fabrication was done using the pulsed laser deposition method which is a well-established technique for manufacturing nanoengineered thin films. The parameters for fabrication of optical glucose sensor were altered to assess the impact of different parameters such as chamber oxygen pressure, deposition time, Er3+ and Yb3+ ions concentrations on structural and fluorescence characteristics of thin films. The spectroscopic characterisation revealed that the low doping (0.25 mol %) concentration of Er3+ ions in the thin films results in longer fluorescence lifetime of up to 12.4 ms while the doping of Er3+ ion in fused silica has been achieved to 2.4 micron depth. The fabricated thin films were also characterized using techniques such as absorption spectroscopy, fluorescence spectroscopy, prism coupling, energy dispersive x-ray mapping using transmission electron microscopy. The thin films with longer fluorescence lifetime were selected for glucose monitoring device development. Poor management of diabetes mellitus can result in various complications such as cardiovascular disease, retinopathy, neuropathy and limb amputations. Diabetes control and complication trial highlighted that, with better glycaemic control resulted in reduced complications due to diabetes. The current techniques available to measure glucose levels are invasive in nature. Presently there is a desperate need for non-invasive sensing technology which is considered as holy grail for glycaemic control. The glucose sensing capabilities of the Er3+ ions doped fused silica was tested using in-vitro glucose measurement in aqueous solutions, blood samples, and intralipids solution. A laboratory bench prototype was developed for a pilot clinical study on people with type 1 diabetes. The change in fluorescence lifetime due to change in glucose concentrations was analysed. The calibrated values were then correlated with the actual glucose reading from finger prick handheld glucose meter and invasive continuous glucose monitor (ICGM). The results were analysed using clarke error grid (CEG) analysis which is a standard statistical analysis tool to assess the accuracy of the device. The next stage of the development includes fabricating a new batch of the photonics chips which has shown the glucose sensing capabilities and thereafter carrying out in-vitro testing as well as carry out the second stage of clinical trials.