We experimentally demonstrate a passively mode-locked thulium doped fiber laser using a bismuth telluride deposited multimode interference (MMI) fiber at a wavelength of 1958 nm. Our MMI based saturable absorber was fabricated by fusion splicing with single mode fiber and null core fiber. The center wavelength and insertion loss of MMI fiber were measured to be ~ 1958 nm and 3.4 dB. We observed a passively mode locked thulium doped fiber laser operating at a wavelength of 1958 nm. The temporal pulse width of output pulses is 4.2 ps with repetition rate of 22.7 MHz.
We demonstrate a self Q-switched Bismuth-doped germanosilicate fiber laser operating at 1463 nm. It is experimentally shown that stable Q-switched pulses with a temporal width of ~ 1.8 μs can be obtained from a simple, all-fiberized Fabry-Perot type cavity without using a saturable absorber at a repetition rate of ~65 kHz with a pump power of ~260 mW. The tuning capability of the temporal characteristics of the output pulses is also investigated. The possible physical mechanism is discussed.