Firstly we identified a set of promising applications and corresponding requirements for the SR source in each application. The two most perspective applications occur to be 2ph-FLIM and THz photoconductive antenna (PCA), accounting for the markets, identifying the practical needs, and feasibility to build the application demonstrator in the next project step.
For comparative evaluation of the SR source in 2ph-FLIM applications with respect to conventional pulsed laser solutions, a Figure-of-Merit (FoM) was identified as a peak power and pulse energy product. Considering the FoM, fluorescence yield and multi-photon counting detection, we conclude that performance of the 2ph-FLIM setup with excitation by the proposed SR source will be comparable to conventional 2ph-FLIM with excitation by presently used lasers.
The power balance model study for THz PCA excitations with SR source revealed that THz spectrum will be of narrower width and shifted to the longer wavelength, compared to the presently used lasers. The efficiency of pulse energy conversion will be by an order of magnitude lower, although this setback may be compensated by using box-car integration approach.
Thus, we conclude that the 2ph FLIM is a more promising application for SR source and we proceed to demonstration of this application with the following activities: (i) selection of fluorescing media with a literature review of the previous studies of the two-photon fluorescence in such samples; (ii) selection of the sample configuration; (iii) compilation and alignment of the optical elements of the demonstration setup as lasers, optics for sample illumination and signal collection, detector unit; (iv) demonstration measurements of the two-photon fluorescence, excited by the SR source and (v) processing of the measured 2ph fluorescence signals from the sample to obtain the fluorescence decay time; (vi) identification and analysis of the limitation factors due to the actual performance of the specific elements of the experimental setup.
The demonstration resulted in detection of the 2ph fluorescence signal and its decay as a function of the elapsed time after the excitation pulse. It is proved that the SR pulse source may be efficient excitation source for two-photon fluorescence imaging microscopy. At the same time it was identified that to reach the level of practical use, it is necessary to continue with specific improvements, as: (i) to decrease the SR source pulse duration variations and environmental sensitivity; (ii) to homogenise the sensitivity and timing of the time-bins in the SPAD array, to verify the reason for the jitter instability with the optical pulse and eventually to cancel it.
Finally we look at the potential markets for the SR source in the promising application case and draw relevant roadmaps towards commercialization. The market study was focused on “global two-photon laser scanning microscope” market. It was conducted using TECHNAVIO market report. The 2ph-FLIM is part of this market. The elaborated technology roadmap makes additional provision to master the technology of the pulsed SR illumination source. We encountered the non-repeatability and environmental sensitivity issues. These as well as other technical issues are addressed in the technological roadmap.
Our initially planned strategy for the business roadmap was to introduce the novel SR illumination source (our future product) to established players in the market of 2ph-FLIM system production. However novel 2ph-FLIM source requires a different architecture of the measurement setup clocking and a change of the detector as well as TCSPC. As such, the established players were not keen to adopt the new SR source product unless it will not precisely meet the timing specifications and architecture used with conventional solid-state and fiber mode-locked lasers. Therefore an understanding comes that the most realistic roadmap way is to consider a transformation of an existing confocal laser scanning microscope (CLSM) system product into 2ph-FLIM system. This transformation should bring better spatial resolution and capability to resolve chemical composition via time resolved measurements thus offering unique sales features to such system. Following along these lines we are considering that next step of the roadmap should be an RIA project with manufacturer of such (CLSM) equipment and having established end-user network over which these novel unique sales features on 2ph-FLIM will be offered.
Because of the short project duration (only 10 months) the results of the project were not yet reported in scientific journals or conferences. Nevertheless, we consider as possible dissemination activities conference communications at SPIE Photonics West 2023 and European Semiconductor Laser Workshop.
