Abstract
A wide-band and tunable Q-switched erbium-doped fiber (EDF) laser operating at 1560.5 nm with a tungsten ditelluride (WTe2) saturable absorber (SA) is demonstrated. The semi-metallic nature of WTe2 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 WTe2 based SA generates the pulsed output. The WTe2 based SA has a modulation depth, non-saturable loss and saturation intensity of about 21.4%, 78.6%, and 0.35 kW/cm2 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.
Highlights
Q-switched pulse generation has long been the focus of research efforts due to its advantageous intrinsic characteristics that include long pulses with higher pulse energies and durations[20], which is highly desirable for applications in material processing, remote sensing, range finding, and medicine[21,22,23,24,25]
With the WTe2 saturable absorber (SA) in the cavity, continuous wave (CW) operation is obtained at a threshold pump power of 77.43 mW while Q-switching begins at a threshold pump power of 124.9 mW
The oscilloscope trace of the Q-switched pulses is given in Fig. 4(b), whereby the generated pulses have a peak-to-peak pulse interval of 18.86 μs that corresponds to a repetition rate of 55.56 kHz
Summary
Q-switched pulse generation has long been the focus of research efforts due to its advantageous intrinsic characteristics that include long pulses with higher pulse energies and durations[20], which is highly desirable for applications in material processing, remote sensing, range finding, and medicine[21,22,23,24,25]. Tungsten ditelluride (WTe2) is another member of the TMD family and is a unique material as it is associated to a rising class of Weyl semimetals. This makes them highly promising for future applications as electronic, spintronic, and optoelectronic devices[32,33] and as a potential candidate for quantum spin Hall insulator materials[34]. In a study conducted by Wang et al.[40], an ultrafast pulse was successful generated in a mode-locked thulium-doped fiber laser through the use of magnetron-sputtering deposited WTe2 as an SA. The peaks located at 163 and 211 cm−1 can be assigned to the in-plane A17 and A19 modes of WTe2, respectively[42,43]
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