Abstract
The generation of a highly stable passive mode locking laser is realized in a thulium doped fibre laser using a WS 2 -ZnO composite as a saturable absorber. Soliton mode locking pulses are generated with a central wavelength of 1936 nm and full-width half maximum (FWHM) of 3.06 nm. The first order Kelly's side band is located at around 5.65 nm from the central wavelength which gives the calculated pulse width value of 1.26 ps. This value corresponds well with the measured pulse width of 1.27 ps using the autocorrelator. The output power of the laser is around 0.44 mW with the peak power of 29.7 W and repetition rate of 9.96 MHz. This laser set-up is highly robust and realizes highly stable laser pulses in the mid-IR wavelength range for a multitude of applications.
Highlights
The strong association of vibrational transition characteristics of the mid-infrared spectral region with many important molecules makes 2 μm wavelength range laser sources highly beneficial for applications such as molecular spectroscopy, chemical sensing, materials processing, industry and free-space sensing [1]–[6]
Can generate ultra-short passive mode-locking laser pulses in an all-fibre laser system, among which is the use of saturable absorbers (SAs) such as carbon nanotubes (CNTs), [20], graphene [21], metal oxides (MOs) [22], black phosphorus (BP) [23] and topological insulators [24]–[26]
To achieve mode locking operation, the pump power is increased to 158 mW while the polarization state of the laser cavity is adjusted by the polarization controller (PC)
Summary
The strong association of vibrational transition characteristics of the mid-infrared spectral region with many important molecules makes 2 μm wavelength range laser sources highly beneficial for applications such as molecular spectroscopy, chemical sensing, materials processing, industry and free-space sensing [1]–[6]. Of many new nanomaterials being explored and studied, transition metal dichalcogenides (TMDs) in particular has shown significant promise for application as an SA to generate mode-locked in 2 μm region [10], [27]–[30]. In this regard, researchers have focused their attention on the exploration of hybridizing TMD nanosheets with other materials including noble metals, oxides and so on. Hybridizing TMDs with metal oxides forms a new binary composite material which possesses both the excellent optical properties of TMDs and strong mechanical qualities of metal oxide. This would be the first time, to the best of the author’s knowledge, that a hybrid WS2-ZnO has been proposed and demonstrated as a SA for mode-locked generation in 2 μm region
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