Wavelength-Switchable Laser and Raman Generation in a Hybrid Fiber-Microresonator System

We experimentally and theoretically investigated a wavelength-switchable Er-doped fiber loop laser system with feedback provided by a high-<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> silica microsphere with whispering gallery modes (WGMs). Two regimes were demonstrated: 1) unidirectional switchable single-mode generation in the C- and L-bands; 2) unidirectional switchable single-mode laser generation in the C-band initiating simultaneous bidirectional single-mode Raman generation in the U-band in the microsphere. In the first regime, laser wavelength switching in the 1532–1568 nm range was achieved by adjusting the coupling <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i>-factor of the microsphere with the active fiber pumped at 980 nm; the microsphere served as a filter. In the second regime, the laser and Raman wavelengths were switched by varying the pump power; the microsphere acted as a nonlinear element and its losses for the laser wave were power dependent. The developed theoretical model allowed us to explain the experimental results and to gain insight into the system behavior at different parameters.