Makoto Gonokami

Signal enhancement in Er3+-doped telluride glass microsphere

Microstructure resonators have attracted considerable attention because of their versatility for signal processing applications. We use our Er3+ doped telluride glass to fabricate Er3+ glass microsphere. The excitation of whispering-gallery modes is realized by coupling from an angle-polished single-mode optical fiber tip to an optical microsphere cavity. In the experimental setup, one fiber was used as an input coupler and the other fiber was used as an output coupler. 975nm fiber pigtailed laser diode was used to side pump the microspheres. Very nice whispering-gallery modes (WGMs) near 1.5mm were observed successfully. Signal enhancement was observed in this Er3+ doped telluride glass microsphere with a radius around 50mm. The best enhancement of this Er3+ doped telluride glass microsphere reaches 12dB.

Temperature dependence of the wavelength and threshold of fiber-taper-coupled L-band Er3+-doped tellurite glass microsphere laser

We report on the temperature dependence of L-band laser emission of fiber-taper-coupled Er3+-doped tellurite glass microsphere. Pumping at 1480 nm instead of 975nm was used to enhance the coupling efficiency, reduce the internal thermal effect, and increase the output laser emission. The microsphere laser emission threshold increased and the emitted laser wavelength shifted with temperature. The experimental results are explained with a quasi-four-level model, showing that a significant reduction of laser threshold can be achieved at lower temperatures and higher Q values of this microsphere laser.