1.61–1.85 $\mu$m Tunable All-Fiber Raman Soliton Source Using a Phosphor-Doped Fiber Pumped by 1.56 $\mu$m Dissipative Solitons

We demonstrate soliton self-frequency shift (SSFS) of more than 15.5% of the optical frequency in a phosphor-doped silica fiber for the first time. This fiber shows great potential for supporting Raman-shift solitons above 1.8 μm with a 1.56 μm pumping, which is superior to the SSFS previously reported in conventional single-mode silica fiber. In our experiment, when the amplified dissipative-soliton pulses at 1.56 μm are injected into a 960 m phosphor-doped silica fiber, SSFS is efficiently initiated, and the output spectrum of Raman solitons can be continuously tuned from 1.61 to 1.85 μm. The Raman solitons have the shortest pulse duration of ~800 fs and the pulse energy of ~1 nJ. This 1.61-1.85 μm ultrashort laser source can not only fill in the spectral gap between Er
³⁺
and Tm
³⁺
emissions but has potential applications in multiphoton microscopy and optical tomography as well.