Flexible and compact multiphoton microscope with fiber delivered femtosecond-NIR laser pulses

Two-photon microscopy enables high-resolution biomedical imaging as well as photoluminescence lifetime investigations in photovoltaics. In order to provide a compact, highly flexible and cost-effective system, we present a compact two-photon platform box with a kagome hollow core photonics crystal fiber for laser pulse delivery. This fiber is suitable for the transmission of ultrashort IR laser pulses within the two optical ranges (i) 700 nm to 1000 nm and (ii) 1400 nm to 1700 nm. Furthermore, two-beam arrangements with parallel operation at two different wavelengths are possible. Our previous measurements of the transmission indicated values above 70% without distortion of the spectral properties or pulse durations using (i) a tunable femtosecond titanium:sapphire laser of 100 fs pulse width as well as a (ii) femtosecond fiber laser at 780 nm (80 fs) and at 1560 nm as well as a (iii) 10 fs titanium:sapphire laser. Subsurface recombination mechanisms in solar cells can be studied by multiphoton excitation and time-correlated single photon counting (TCSPC). Furthermore, deep tissue imaging can be performed. However, bending of the fiber may induce transmission losses. Investigations on the bending properties are presented. Time-resolved measurements on standard samples and plant tissue (Convallaria) is provided by using fluorescence lifetime analysis. Bulk solar cell impurity investigations are possible by analyzing photoluminescence signals.