Widely tunable S-band ring-cavity Tm3+-doped fluorotellurite fiber laser.

Tm3+-doped fluorotellurite fibers (TDFTFs) are fabricated by using a rod-in-tube method. A 2.1 m long TDFTF is used as the gain medium, in which both ends of the TDFTF are connected to a short piece of a silica fiber by direct fusion splicing. By inserting the above TDFTF and a tunable optical bandpass filter into a ring cavity and employing a 1400/1570 nm dual-wavelength pumping technique, tunable lasing from 1460 to 1526 nm is obtained, which almost covers the whole S-band. To the best of our knowledge, this is the first report of tunable Tm3+-doped fiber laser with a tunable range almost covering the whole S-band. Furthermore, by removing the tunable optical bandpass filter from the ring cavity, free-running multi-wavelength lasers at 1500 and 1901 nm are achieved. Our results show that TDFTFs are promising gain media for constructing S-band fiber lasers.

Voltage-controlled nonlinear optical properties in gold nanofilms via electrothermal effect.

Dynamic control of the optical properties of gold nanostructures is crucial for advancing photonics technologies spanning optical signal processing, on-chip light sources and optical computing. Despite recent advances in tunable plasmons in gold nanostructures, most studies are limited to the linear or static regime, leaving the dynamic manipulation of nonlinear optical properties unexplored. This study demonstrates the voltage-controlled Kerr nonlinear optical response of gold nanofilms via the electrothermal effect. By applying relatively low voltages (~10 V), the nonlinear absorption coefficient and refractive index are reduced by 40.4% and 33.1%, respectively, due to the increased damping coefficient of gold nanofilm. Furthermore, a voltage-controlled all-fiber gold nanofilm saturable absorber is fabricated and used in mode-locked fiber lasers, enabling reversible wavelength-tuning and operation regimes switching (e.g., mode-locking-Q-switched mode-locking). These findings advance the understanding of electrically controlled nonlinear optical responses in gold nanofilms and offer a flexible approach for controlling fiber laser operations.