In this project we developed and investigated novel types of tunable Raman fibre lasers. Raman scattering occurs in fibers disregarding the spectral position of the launched radiation. This peculiarity turns into a powerful technique for tunable fibre lasers and broadband amplifiers allowing to produce optical gain basically at any spectral position. Combining several Raman cascades, it becomes possible to greatly extend the amplification bandwidth as compared to the traditional laser media doped with active ions.
For the first time, we demonstrated an ultra-broadband artificial gain medium exploiting cascaded Raman amplification. In contrast to the usual multi-stage Raman lasers, we propose to choose the wavelength of the laser action at the "red" edge of the Raman amplification band where the gain is small. This concept allowed us to develop the Raman fiber laser tunable in the range of 1400-1622 nm exploiting only one Raman cascade in the laser scheme. With additional Raman cascades it would be possible to cover with the optical gain a much larger spectral interval, which is the subject of the patent application under preparation. We anticipate that the invented scheme will be used for development of ultra-broadband telecom amplifiers.
Another approach allowed us to cover the whole 600-nm band from 1040 to 1640 nm using several cascades of Raman amplification of a seed fibre laser tunable in the range of 1040-1085 nm. The developed laser design allowed the predominant energy transfer to the desired Raman cascade resulting in the spectral purity of the output laser emission of better than -20 dB, which from the practical point of view is a single-wavelength laser. We anticipate extension of the spectral tuning range of this laser scheme to wavelengths beyond 2 µm under commercial engineering. Such lasers are excellent for the development of the compact, robust, and reliable laser spectrometers for inline applications in food industry, health care, telecom, environmental monitoring, etc.
The results of projects are particularly attractive for direct commercialization.
