Widely tunable single- and multiple-pulse Er-doped passively mode-locked fiber laser exploiting two semiconductor saturable absorber mirrors

Abstract

We report on a simple self-starting diode-pumped passively mode-locked Er-doped fibre laser based on two semiconductor saturable absorber mirrors (SESAMs), generating sub-picosecond stable optical pulses. Pulses duration between 350 and 650 fs (FWHM) was observed for pulses central wavelengths ranging between 1540 nm and 1570 nm. The cavity basic frequency was 3.7 MHz, and stable operation up to the third harmonic (11.1 MHz) was observed when the output power of the 980 nm diode pump was increased to its maximum value of ~300 mW. The maximum average output power was 19.45 mW, which corresponded to a pulse energy of ~4 nJ. Noise characterization of the mode-locked laser source was performed, in order to estimate the phase noise of the output pulses in terms of timing jitter. All the fiber components in the cavity were polarization maintaining in order to increase long-term stability of the laser operation.