Signal-to-noise ratio of ultrashort pulses enhanced by a fiber Sagnac loop

A method to enhance the signal-to-noise ratio of ultrashort pulses is presented with picosecond pulses as an example. Numerical simulation and analysis show that the signal-to-noise ratio can be improved by four orders of magnitude using a fiber Sagnac loop with two different fibers. It is also found that there is an optimal length of the fiber for improving the signal-to-noise ratio. This is a useful method for improving the signal-to-noise ratio of the seed light in the chirped pulse amplification (CPA) or optical parametric chirped pulse amplification (OPCPA) systems.

► We report a method to enhance the signal-to-noise ratio of ultrashort pulses via a fiber Sagnac loop.
► Our theory predicts that the signal-to-noise ratio can be improved by four orders of magnitude.
► This is promising to eliminate the background of the seed light in the ultrahigh power laser systems.