Gain-switched all-fiber laser with narrow bandwidth

Abstract

Abstract:Gain-switching of a CW fiber laser is a simple and costeffective approach to generate pulses using an all-fiber system. We report on the construction of a narrow bandwidth (below 0.1 nm) gain-switched fiber laser and optimize the pulse energy and pulse duration under this constraint. The extracted pulse energy is 20 µJ in a duration of 135 ns at 7 kHz. The bandwidth increases for a higher pump pulse energy and repetition rate, and this sets the limit of the output pulse energy. A single power amplifier is added to raise the peak power to the kW-level and the pulse energy to 230 µJ while keeping the bandwidth below 0.1 nm. This allows frequency doubling in a periodically poled lithium tantalate crystal with a reasonable conversion efficiency.

The all-fiber cladding-pumped Yb-doped gain-switched laser

“…Above we have analyzed the pulse duration and seen that a short active fiber and as short as possible passive fiber result in the most narrow pulses. We now consider optimization of the peak power, which is critically important in for example long-pulse supercontinuum generation initiated by modulation instability (where the gain is proportional to the peak power) [7,13]. In recent publications [12,14,15] the peak power was shown to vary linearly with the pump power for a fixed active and passive fiber length.…”

“…This increases the complexity and the cost of the laser significant. A more cost-effective solution would be to generate gain-switched pulses with a moderate pump power and then amplify them in a large mode area fiber amplifier [7,16,17].…”

“…The output pulse energies are often in the microjoule range and with repetition rates spanning from a few kilohertz up to the megahertz range [2,5]. These properties make the gain-switched fiber lasers interesting for many applications; directly or after single-stage amplification in high-power fiber amplifiers [1,2,6,7].…”

“…In this paper we will focus on gain-switching of cladding-pumped Yb-doped silica fiber lasers due to their power scalability and the vast amount of applications [1,2,7]. The underlying physics and correlations of gain-switching are thoroughly investigated.…”

Gain-switched PCF rod type fiber laser

“…Till now several gain switched setup using rare earth ytterbium doped fibers have been reported with pulse duration in the range of over 100 ns [2][3][4][5]. With the appropriate design the pulse duration can be lowered as shown recently in [6] and especially in [7] where linearly polarized pulses with duration of 66 ns and peak power of 700 W from oscillator were reached. The shortest reported pulses achieved from ytterbium doped fibers have duration of 27 ns at the peak power of 1.4 kW [8].…”