A novel concept of a booster amplifier for a pulsed Tm fiber laser at 1940 nm based on Tm:Lu2O3 ceramics and implementing fiber-combined signal and pump was examined. The pumping emission of the ceramics at 1678 nm was obtained from Raman-shifted Er fiber laser radiation. The hybrid fiber-ceramics amplifier with a gain factor of up to 6 dB and a pulse energy of more than 650 μJ with single-mode output was demonstrated.

Our recent progress in development of all-fiber format and hybrid thulium fiber laser is presented and discussed. Thulium pulse fiber lasers are very promising source for variety of applications such as medicine, marking, engraving etc. AII-fiber-format thulium fiber laser (IPG Photonics TLP-0.2-100-25-5) is very attractive for its robustness, efficiency and fiber delivery. It is based on MOP A design, output booster pumped by single-mode cw erbium fiber laser. Its disadvantage is low output pulse energy (250 /-!J) which is a result of relatively low values of absorption and emission of Tm 3 + ions in quartz fiber. Another strong limitation of all fiber-format booster approach is high nonlinear interactions in delivery fiber which limits output peak power to 2-3 kW. In work [1] we have demonstrated hybrid version of output booster with fiber-combined signal and pump. In this report we present our further progress in increasing output energy and peak power. The scheme of fiber combined signal and pump single pass solid-state power amplifier is shown in Fig. l. In our experiments the signal at 1940 nm with linewidth of 0.3 nm was produced by an all-fiber pulsed Tm-doped laser with pulse duration 90 ns, tuned pulse repetition rate (3--45 kHz) and tuned output pulse energy up to 170 uJ [2]. Pumping source at 1678 nm was obtained from commercially available Er-fiber laser module (IPG Photonics EFL-50) by connecting 200 m fiber Raman cavity which converts emission wavelength from 1567 to 1678 nm; its slope efficiency goes up to 50%, getting in result 23.5W of maximum output power.Our experimental result is shown in Fig.2a for different pulse repetition rates (t) and beam waist diameters (2m).The pump absorption in the crystal was �50%, and it was possible to add second crystal as next amplification stage, with same optical configuration. Output characteristics of two-stage hybrid amplifier is shown in Fig. 2b, output pulse energy more than 1 mJ was achieved.