ZnO Nanowire Transistor Synthesized and Characterized

To enable ultrahigh capacity laser communications in future networks, CONSRT is developing all-optical buffers, high-speed lasers, broadband optical amplifiers and memory devices to replace the speed-limiting optical-electrical-optical (OEO) switching system currently used in optic fiber communication. To date, realization of an all-optical communication network has been stymied by the lack of a suitable optical buffer with which to delay and temporarily store optical signals while routing. An optical medium that can significantly slow down optical signals could effectively function as an optical memory. The memory storage time is adjusted by varying the group velocity reduction factor in the medium. Recently, CONSRT researchers have successfully demonstrated slow light in a semiconductor quantum well (QW) structure for the first time. In our experiments, the optical buffering effect was achieved by slowing down the optical signals using an external control light source to vary the dispersion characteristic of the medium. The buffer medium was made of GaAs multiple quantum wells grown by molecular beam epitaxy. Population oscillations in QWs were induced by illuminating the sample with a pump beam and a tunable probe beam. The pump and probe laser beams create a coherent carrier population interference which slows down light. The phase delay and absorption of the probe beam were simultaneously measured to determine its group velocity in the irradiated QWs. Results deduced from the dispersion experiments at low temperatures indicate that we have successfully reduced the group velocity of optical signal in a QW structure. The group velocity slow-down factor was found to increase with increasing pump intensity. A group velocity 100,000 times slower than light speed in vacuum was achieved. The transparency bandwidth window was also found to be as broad as 1~2 GHz. | | Slow--Light Medium