Complete Analysis of Picosecond Optical Pulses by Using the Offset Frequency Intensity Modulation

Complete analysis of optical pulses is crucial for many applications, where the accurate spectral phase controlling is necessity. Frequency-resolved optical gating (FROG) [1] and spectral phase interferometry for direct electric field reconstruction (SPIDER) [2] are routinely employed for analyzing femtosecond pulses. But, it is still difficult for analyzing low-peak-power picosecond pulses, since nonlinear optical effects are utilized in these methods. Picosecond pulses are often characterized by employing intensity or phase modulator operating at ~ 10 GHz and an optical spectrum analyzer (OSA) [3]–[7]. Because these modulators do not employ optical nonlinearity, picosecond pulses can be sensitively reconstructed. However, these methods require accurate synchronization between the modulation signal and repetition rate signal, which is particularly difficult, when the repetition rate is less than 100 MHz, because modulation signal should be synchronized with+150^th multiple of the repetition signal. The timing jitter between the two signals directly affect the reproducibility of the retrieved pulse shapes in these methods.