Passively Q-switched erbium all-fiber lasers by use of thulium-doped saturable-absorber fibers

Abstract

We demonstrate all-fiber passively Q-switched erbium lasers at 1570 nm using Tm(3+)-doped saturable-absorber fibers. The absorption cross section of a Tm(3+)-doped fiber at 1570 nm was measured in a bleaching experiment to be about 1.44 x 10(-20) cm(2). With a thulium-doped fiber, sequential pulses with a pulse energy of 9 microJ and a pulse duration of about 420 ns were stably produced at repetition rates in the range 0.1 to 2 kHz. The maximum pulse repetition rate was 6 kHz, limited by the maximum pump power of a 980-nm laser diode, about 230 mW.

Modeling and Analysis of a Pulsed Er-Tm Fiber Laser System

“…Parameters used in the numerical simulation are listed in Table I [5], [8], [16]- [19]. In the simulation of the passively Q-switched Er-doped fiber laser, R 3 and R 4 are not taken into consideration.…”

“…However, as the lifetime of the 3 F 4 energy level of Tm ion is relatively long (300 ß 500 μs) in silicate fiber [5], [9], [10], the FSA could not fully recover before the next pulse [8], leading to the deterioration of the laser efficiency at high Q-switching repetition rate. The situation would be even worse for Bi-doped and Ho-doped silicate FSAs, as their lifetimes are even longer [12], [13].…”

Q-switched all-fiber lasers with saturable absorbers

“…It is known that Er-ions allow one to obtain lasing in the range of 1.53 -1.60 μm, where Tm-ions have the absorption band. This was used in [43] to Q-switch Er-doped fiber laser applying FSA based on Tm-doped fiber. Er-doped fiber laser was pumped into the core by a source with maximum power of 230 mW.…”

A Tm–Ho codoped fiber based 38 nm wideband wavelength tunable passivelyQ-switched Er-doped fiber laser

“…In fact, Tm-doped FSAs have been successfully used in passive Q-switching of Er-doped fiber lasers [11,13]. However, compared with the wide emission band of Er-doped fiber, the Q-switched wavelength range is quite limited.…”

“…The Q-switching threshold of this fiber laser is only 20 mW, and with the increase of the pump power, the repetition rate changes from sub-kHz to tens of kHz with pulse duration in the µs range. Emission cross-section of the active fiber is calibrated with the claimed value of 1 × 10 −21 cm −2 at 1600 nm, and absorption cross-section of the FSA is calibrated with the derived value of 1.44 × 10 −20 cm 2 at 1570 nm for Tm ions in [13]. Stable Q-switching requires a larger absorption cross-section of the FSA compared with the emission cross-section of the active fiber.…”