To design the femtosecond laser for Cr: LiCAF, cavity simulation and the pump source were discussed. Continuous wave and Kerr lens mode locking was simulated by using MatLab. The simulation show comparable results to the existing experiment. The pump source was 690 nm diode laser. The diode laser was coherently locked using innovative design of birefringence crystals. The birefringence crystals property was characterized by using polarization method. The characterization is believed to be able to achieve more than 97% accuracy. In the last part, polarimeter and polarization controller was built to facilitate the polarization characterization. The performance of the polarimeter and polarization controller can transmit more than 94% efficiency.Bachelor of Science in Physic