Skip to main content

Stimulated Raman analysis and Raman microscopy with Fourier Domain Mode Locked (FDML) laser sources

Final Report Summary - FDML-RAMAN (Stimulated Raman analysis and Raman microscopy with Fourier Domain Mode Locked (FDML) laser sources)

The ERC-project FDML-Raman focused on the development of a new approach to perform stimulated Raman sensing. Raman sensing is an optical technique, capable of determining the molecular species in a sample. In the project we developed Time Encoded (TiCo) Raman, a new optical hardware-platform combined with a new electronic detection concept. The system uses a post-amplified actively modulated diode laser as pump and a rapidly wavelength swept laser as probe. Within the project we could show that our TiCo-Raman can generate spectra with a unique combination of wide spectral coverage, high resolution, excellent dynamic range, good sensitivity, nearly perfect signal linearity with sample concentration, all at spatially single mode probing and high acquisition speed. The system is robust, cost effective and most importantly it is fiber based, hence an ideal candidate for future endoscopic beam delivery in biomedical applications. Within the project we successfully demonstrated high quality high speed spectroscopy and molecular Raman microscopy. Due to the long 1064nm wavelength of our laser, we have virtually no unwanted fluorescence background. The systems brakes ground for future research on endoscopic Raman sensing for the early diagnosis of disease.
For TiCO-Raman we also developed a new fiber based laser source within the project. It uses a complex interplay between four-wave mixing and Raman amplification and is fully electronically wavelength switchable from pulse to pulse. Since this source has very unique features, we expect a wealth of future applications.
For example, even though this source operates in an unusual parameter regime, we were able to successfully demonstrate two photon microscopy with it. We could show that with the new nanosecond two-photon setup (ns-TPM) it is possible to detect fluorescence lifetimes with a single laser pulse. Additionally, the system is all fiber based, again ready for endoscopic beam delivery.
Both newly developed imaging modalities, TiCo-Raman and ns-TPM, and the laser are fully synchronizable and triggerable and they exhibit “measure on demand” capability. Hence, they are the ideal candidates to be integrated into tomorrow’s medical optics tools as a multi-modal imaging platform. Such a platform might substantially improve early diagnosis of disease in the future.