Modern science and technology have made rapid progress and evolved from electron era to light era and from the age of nano technology to the age of femto technology. To lead such circumstances, we study ultrafast nonlinear phenomena and their applications. Currently, we are interested in the novel ultrashort lasers, vortex beams which have orbital angular momentum, ultrafast spectroscopy such as transient absorption spectroscopy, bio-imaging using coherent anti-Stokes Raman micro-spectroscopy, and THz generation using quasi phase matched crystals.