56 nm Wide-Band Tunable Q-Switched Erbium Doped Fiber Laser with Tungsten Ditelluride (WTe(2)) Saturable Absorber.

A wide-band and tunable Q-switched erbium-doped fiber (EDF) laser operating at 1560.5 nm with a tungsten ditelluride (WTe(2)) saturable absorber (SA) is demonstrated. The semi-metallic nature of WTe(2) as well as its small band gap and excellent nonlinear optical properties make it an excellent SA material. The laser cavity uses an 89.5 cm long EDF, pumped by a 980 nm laser diode as the linear gain while the WTe(2) based SA generates the pulsed output. The WTe(2) based SA has a modulation depth, non-saturable loss and saturation intensity of about 21.4%, 78.6%, and 0.35 kW/cm(2) respectively. Stable pulses with a maximum repetition rate of 55.56 kHz, narrowest pulse width of 1.77 µs and highest pulse energy of 18.09 nJ are obtained at the maximum pump power of 244.5 mW. A 56 nm tuning range is obtained in the laser cavity, and the output is observed having a signal to noise ratio (SNR) of 48.5 dB. The demonstrated laser has potential for use in a large number of photonics applications.