Soliton Order Preservation for Self-Frequency Shift With High Efficiency and Broad Tunability

We present a soliton order preservation mechanism leading to broad tunability with high energy conversion efficiency (ECE) from a fiber-based soliton self-frequency shift (SSFS) system. Here, a pulse compressing fiber, placed before the Raman shifting nonlinear fiber (NLF), acts as a soliton order preserver. Thanks to this passive mechanism, the soliton order at the input of the NLF is preserved within 2.0 <
N
< 2.3 despite a ∼6.7-fold energy increase. The resulting pulse leads to an SSFS that is spectrally tunable over 1.96–2.14 µm while keeping an ECE of 80–85%. It is the first time that an ECE > 80% is maintained over a tunable range as large as 180 nm in a passive fiber-based SSFS system. Solitons are also tunable up to 320 nm in the wavelength range of 1.96–2.28 µm with ECE > 50%. Such a soliton order preservation mechanism that enables a high ECE while maintaining a broad soliton tunability is of utmost practical interest for wavelength conversion systems.