Autocorrelation of mode-locked fiber laser pulses at 1550 nm exploiting a nonlinear response in silicon photodiodes

The accurate measurement of picosecond and subpicosecond optical pulses at wavelengths around 1550 nm is usually carried out using the technique of optical autocorrelation. The use of nonlinear two-photon absorption in semiconductors has been proposed as an alternative mechanism to generate a signal proportional to the autocorrelation function, eliminating the need for either a phase matched nonlinear crystal, or a photomultiplier tube for detection. Autocorrelation measurements using semiconductor materials have previously been reported using both simple Si and GaAsP photodiodes and semiconductor waveguide structures and in this present paper, we report what we believe to be the first demonstration of Si-photodiode-based autocorrelation for the measurement of mode-locked fiber laser pulses at a wavelength of 1550 nm