Efficient Nonlinear Frequency Conversion into the visible spectral region
Fully tunable compact visible laser sources in the spectral region of 500 – 650 nm have been long time an aspiration of laser users, and recently, a great progress has been made here with the realization of compact broadly tunable visible continuous wave and picosecond laser sources based on second-harmonic generation (SHG) in a nonlinear crystal waveguide with tunable external cavity diode lasers. This was possible by utilization of a significant difference in the effective refractive indices of the high-order and low-order modes in multimode nonlinear waveguides.
By exploiting this recent discovery from our group about the multimode-matching technique in nonlinear crystal waveguides, broad second-harmonic tunability in excess of 70 nm in the visible spectral region (574 nm – 647 nm) was recently achieved using a single periodically poled potassium titanyl phosphate (PPKTP) crystal waveguide and a single quantum-dot laser.
Such laser sources have a number of cutting-edge applications ranging from biophotonics and photomedicine to laser projection displays. In particular, our group works on the development of broadly tunable continuous wave and picosecond visible lasers and their application in Confocal Laser Scanning Microscopy (CLSM) and Fluorescence Lifetime Imaging Microscopy (FLIM) with a focus on quantitative imaging in biological samples.
This work was supported by €14.7M FP7-IP FAST-DOT and EPSRC projects.