Supercontinuum spectrum generation in the liquids with different band gap thresholds

Supercontinuum spectrum generation by femtosecond laser pulses propagating in transparent liquids with different band gap thresholds is investigated. As the laser energy increases, the laser spectrum is strongly broadened and modulated, and finally a supercontinuum spectrum can be observed. The spectral broadening can be mainly attributed to the optical Kerr effect at low laser energy and the plasma created by the multiphoton excitation of electrons from the valence band to the conduction band at high laser energy. It is found that the spectral broadening and modulation strongly depend on the band gap threshold E_gap of the medium.