Features of repetitively-pulsed oscillation of an erbium fiber laser with a saturable absorber Bi2Te3 covered by silicone at various temperatures

Abstract

The oscillation of erbium doped fiber lasers (EDFL) in the Q-switch mode is investigated. Etched out fiber tapers coated with two types of saturable absorbers (SA) are tested as passive Q-switches. SA of the first type comprises two-component silicone with nano-flakes of a Bi2Te3 single crystal dissolved in it. A thin film of Bi2Te3 synthesized by the Metalorganic Chemical Vapor Deposition (MOCVD) method on the surface of the fiber taper and coated with the same silicone served as SA of the second type. Housed within a refrigerator the fabricated sample of fiber taper with SA was in series plug into the fiber ring of the laser. A maximum is observed in the temperature dependence of the EDFL pulse repetition rate with both types of Q-switches. A decrease in temperature to –4 °C (for the first type) and to 9.5 °C (for the second one) led to the oscillation wavelength change from 1560 to 1530 nm. Cooling of Q-switches of the first and second types was accompanied by a decrease in the duration of laser pulses by a factor of 2.5 and 3.5, respectively, at a pump power corresponded to the conversion of laser oscillation from CW to repetitively-pulsed mode. At a given laser pump power, a 20% and 40% increment in the pulse repetition rate is observed upon cooling of passive Q-switches based on Bi2Te3 nanopowder-in-polymer and Bi2Te3 thin-film, up to temperatures of –14.8 °C and 4.4 °C, respectively, as compared to that one at room temperature. A diminution in the temperature of a passive Q-switch made it possible to obtain pulsed laser oscillation in a circuit that did not support the pulsed mode at room temperature.