Abstract
Thulium-doped fiber laser (TDFL) is a versatile platform that can be engineered to produce laser sources with desired performance that target a vast number of applications, however its operation in the 1.7-μm region is still underdeveloped owing to the quasi-three-level nature of TDF emission. In this paper, we report a high energy noise-like pulse generation from a nonlinear polarization rotation (NPR) mode-locked TDFL. By using highly efficient core-pumping at 1650 nm and intra-cavity filtering component, stable mode-locking operation at 1750 nm is realized at a pump threshold of 1.5 W. With increasing the pump power to 5 W, the pulse width is stretched from 0.8 ns to 3.7 ns, while the monitored output power is linearly increased from 50 mW to 251 mW, corresponding to a maximum pulse energy of 321 nJ at the pulse repetition rate of 782 kHz. The long-term and shot-to-shot stability of the output are characterized to be 0.11 dB and 2.8% respectively. Noise-like pulse operation of the laser is confirmed by measuring the autocorrelation trace, which demonstrates a coherent peak on top of a wide pedestal. To the best of our knowledge, this is the first demonstration of high energy noise-like pulse generation from a TDFL at 1.7-μm band, enabling potential applications in for example spectroscopic analysis and material processing.
Highlights
In recent years, the popular thulium-doped fiber lasers (TDFL) are expanding their operational wavelength coverage through accessing the 1.7-μm region, where they have previously been hindered by the quasi-three-level nature of TDF emission, which leads to strong re-absorption of short wavelength light [1], [2]
Thulium-doped fiber laser (TDFL) is a versatile platform that can be engineered to produce laser sources with desired performance that target a vast number of applications, its operation in the 1.7-μm region is still underdeveloped owing to the quasithree-level nature of TDF emission
We report a high energy noise-like pulse generation from a nonlinear polarization rotation (NPR) mode-locked TDFL
Summary
The popular thulium-doped fiber lasers (TDFL) are expanding their operational wavelength coverage through accessing the 1.7-μm region, where they have previously been hindered by the quasi-three-level nature of TDF emission, which leads to strong re-absorption of short wavelength light [1], [2]. This was driven by a plenty of applications such as deep bio-imaging, spectroscopic analysis and material processing that take advantages of the third near-infrared (NIR3) optical window (1600–1870 nm) for bioimaging and abundant molecular absorptions in this spectral region [3], [4]. The relatively low optical gain of BDF requires the laser cavity employs a long gain fiber (generally several tens of meters), limiting the versatility and the achievable power/energy of this type of laser
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