Asymmetric DC optical fibers for single-shot fs spectroscopy

The 2018 Nobel prize in physics was awarded for the development of femtosecond (fs is 10-15 s) pulsed laser sources. Indeed, such lasers revolutionized the material research, allowing deeper understanding of many processes responsible for the function of organism, for the influence of drugs or for the synthesis of novel materials. Femtosecond (ultrafast) lasers enable to generate optical pulses with extremely high peakpowers. Upon such powerful irradiation the atoms and molecules react in a surprising manner. Many such extreme processes lead to the change of the material structure on the femtosecond time scale in a irreversible way, which is very hard to track because electronic devices are too slow. Nowadays, medical and environmental diagnostics aswell as material processing represent fields that benefit from the utilization of ultrafast pulses. However they require long optical wavelengths (2 6 m) far beyond the sensitivity of human eye, which is the so called mid- infrared. The project plan is a study of a new simple diagnostics technique in the mid infrared spectral region, which will be able to monitor irreversible ultrafast material processes. A Polish research team will develop a special fiber with two parallel cores made of glass, which is transparent in the mid infrared in contrast to the standard glass. The Austrian research team will develop two special ultrafast pulsed laser sources, which outputs will be guided simultaneously along the fiber. The careful synchronization of the two sources operating at two distant wavelengths will result in a special sequence of pulses representing a series of mid infrared colors. The final goal of the project is to utilize this novel form of optical radiation for material processes diagnostics by a relatively low cost method. It has potential in many cases to replace the expensive and bulky x-ray, magnetic resonance or particle acceleration techniques. An important part of the project are computer based simulations, which can predict the proper structure of the fiber and its interaction with the two color femtosecond pulses. After the initial calculations the Polish team will prepare the special glasses and manufacture different type of fibers comprising two cores with dimensions and distance at the level of few m. The Austrian research team will perform experiments and select the best samples for the final spectroscopic investigations. We envisage to present at the end of the project more optical fibers, which will be optimized for different mid infrared wavelengths. Important advantage of this method is its compactness and low energy requirment of the diagnostics radiation which will be processed by the fibers. It will enable its application in the case of biological samples without their damage or degradation.