Net gain in a semiconductor cylinder fiber

We here present wide band net gain measurements in a Cd3P2 Cylinder Fiber. These fibers normally absorb light. Pump induced charge cariers first decrese the absorbtion. Further pumping results in net gain. The Semiconductor Cylinder Fiber (SCF) we fabricate consist of a type 7056 glass core with a diameter of 9.6 pm and an index of refraction of 1.487. The core is surrounded by a thin, 5 to 15 nm thick, semiconductor layer. The semiconductor layer in turn is surrounded by a type 7052 glass cladding with an index of refraction of 1.484. The fiber has an outside diameter of 84 yam, Fig. 1.