Ultrasonic-assisted synthesis of Ti3AlC2-TiO2 composite and its application as a saturable absorber for generating the mode-locked pulses in thulium-holmium doped fiber laser

Abstract

MAX phase Ti3AlC2-TiO2 composite has been synthesized using the simple ultrasonication method. FESEM result has displayed the formation of TiO2 nanoparticles with an average diameter of approximately 10 nm on the surface of Ti3AlC2. The Ti3AlC2-TiO2 is deposited onto the side-polished fiber through optical deposition technique, forming all-fiber saturable absorber (SA) device. The SA device has a modulation depth of ~33%, saturation intensity of ~0.01 MW/cm2 and insertion loss of 3 dB. By incorporating the SA device into the thulium-holmium doped fiber laser (THDFL) ring cavity, stable mode-locked pulses start at a pump power of 191.8 mW with pulse width of 1.06 ps, repetition rate of 10.5 MHz and operating at the central wavelength of 1912.2 nm. The signal-to-noise ratio (SNR) is ~50 dB, and a stable soliton spectrum is obtained with a 3-dB bandwidth of 3 nm. The mode-locking operation is based on the evanescent field interaction with the Ti3AlC2-TiO2 particles. This study has revealed the potential of MAX phase Ti3AlC2-TiO2 composite as SA to generate ultrafast fiber laser that is useful for further application in photonics and optoelectronics.