Titanium dioxide doped fiber as a new saturable absorber for generating mode-locked erbium doped fiber laser

This work reports on the use titanium dioxide doped fiber (TiO2DF) as a passive saturable absorber (SA) in generating stable and self-starting mode-locked pulse laser in Erbium doped fiber laser (EDFL) ring cavity. The TiO2DF SA is a self-made fiber with 20 cm in length. It has a core diameter of 45 mu m, the numerical aperture (NA) of 0.21, core composition of Silica-Titanium (Si-Ti) and cladding composition of Silica Oxides (SiO2). The TiO2DF SA has a wide-band linear absorption profile which also covers the mode-locked laser operating wavelength of 1553 nm. The TiO2DF serves as a great SA due to the presence of anatase crystalline form of TiO2 which provide saturable optical losses in the laser cavity. Results show that reliable mode-locked pulse is observed as the pump power raises from 106 mW to 142 mW. Within this range of pump power, a nearly constant repetition rate within the range of 0.984 MHz to 0.990 MHz is obtained. The actual pulse width seen from the auto-correlator is about 9.74 ps. Both, the maximum peak power of 878 mW and the maximum pulse energy of 8.56 nJ are calculated at the maximum pump power (142 mW). The fundamental frequency of the EDFL mode-locked pulse laser has a signal to noise ratio (SNR) of 54 dB. Our demonstration shows that the TiO2DF-SA is reliable and quite promising in generating EDFL mode-locked pulse laser. (C) 2018 Elsevier GmbH. All rights reserved.