Current high power fiber amplifiers are nearly always double-cladded and pumped with high power diode bars or other kinds of laser diodes. In such devices, the amplification process takes place in the fiber core and the maximum output power for Er3+ doped amplifiers today reaches several hundred watts.


Prof. Kashyap proposes a novel approach to designing a high-power Erbium Fiber Doped Amplifier (EDFA) which overcomes these limitations. This device converts a propagating signal core-mode of a single-mode fiber into a single cladding mode in the beginning of an active region of the amplifier (Er3+ doped cladding area) with a long period grating (LPG) imprinted in the fiber core .

In contrast to other well known schemes, in which signal amplification takes place in the doped core; here, it takes place in the doped cladding. Furthermore, the large diameter of the cladding permits to increase dramatically an effective mode area of the signal and increases the threshold powers for unwanted Stimulated Brilluoin Scattering and Stimulated Raman Scattering.

Thus it enables to get very high output power.

This system operates in the relatively eye-safe wavelength range 1.5-1.6 μm. It is of great interest for:
- high power sources for optical communications,
- welding
- cutting
- ultra-high power pumping
- Clean energy sources
- Electric power distribution

Computer simulations and experiments.