We present our recent advances on power scaling of a high-power single-pass pumped CVD-diamond Raman oscillator at 1.2 μm. The single pass scheme reduced feedback to the high gain fiber amplifier, which pumps the oscillator. The Yb-doped multi-stage fiber amplifier itself enables up to 1 kW output power at a narrow linewidth of 0.16 nm. We operate this laser in quasi-cw mode at 10% duty cycle and on-time (pulse) duration of 10 ms. With a maximum conversion efficiency of 39%, a maximum steady-state output power of 380 W and diffraction limited beam quality was achieved.
We present our recent advances on power scaling of a high-power single-pass pumped CVD-diamond Raman oscillator at 1.2 μm. The single pass scheme reduced feedback to the high gain fiber amplifier, which pumps the oscillator. The Yb-doped multi-stage fiber amplifier itself enables up to 1 kW output power at a narrow linewidth of 0.16 nm. We operate this laser in quasi-cw mode at 10% duty cycle and on-time (pulse) duration of 10 ms. With a maximum conversion efficiency of 39%, a maximum steady-state output power of 380 W and diffraction limited beam quality was achieved.
We report on the measurement of the longitudinal temperature distribution in a fiber amplifier fiber during high power operation. The measurement signal of an optical frequency domain reflectometer is coupled to an ytterbium doped amplifier fiber via a wavelength division multiplexer. The longitudinal temperature distribution was examined for different pump powers with a sub mm resolution. The results show even small temperature variations induced by slight changes of the environmental conditions along the fiber. The mode instability threshold of the fiber under investigation was determined to be 480W and temperatures could be measured overall the measured output power values.
Proc. SPIE. 9728, Fiber Lasers XIII: Technology, Systems, and Applications
KEYWORDS: Fiber amplifiers, Optical amplifiers, Backscatter, Calibration, Fiber lasers, Reflectometry, High power fiber lasers, High power fiber amplifiers, Thulium, Fiber coatings, Temperature metrology, Absorption
We present measurements of the temperature increase inside the active fiber of a thulium fiber amplifier during high power operation. At a pump power of over 100 W at a wavelength of 793 nm, we measure the core temperature distribution along the first section of a large mode area (LMA) highly thulium doped active fiber by use of an optical backscatter reflectometer. A mode field adaptor is used to maintain single mode operation in the LMA fiber. An increase in temperature of over 100 K can be observed in spite of conductive cooling, located at the pumped fiber end and jeopardizing the fiber coating. The recoated splice can be clearly identified as the hottest fiber region. This allows us to estimate the maximum thermally acceptable pump power for this amplifier. We also observe that the temperature can be decreased by increasing the seed power, which is in agreement with theoretical predictions on the increase of cross relaxation efficiency by depletion of the upper laser level. This underlines the role of power scaling of the respective seed power of a thulium amplifier stage as a means of thermal management.
We present a theoretical and experimental analysis of a pulsed 1645 nm optical parametric oscillator (OPO) to prove the
feasibility of such a device for a spaceborne laser transmitter in an integrated path differential absorption (IPDA) lidar
system. The investigation is part of the French-German satellite mission MERLIN (Methane Remote Sensing Lidar
Mission). As an effective greenhouse gas, methane plays an important role for the global climate.
The architecture of the OPO is based on a conceptual design developed by DLR, consisting of two KTA crystals in a
four-mirror-cavity. Using numerical simulations, we studied the performance of such a setup with KTP and investigated
means to optimize the optical design by increasing the efficiency of the OPO and decreasing the fluence on the optical
components. For the experimental testing of the OPO, we used the INNOSlab-based ESA pre-development model
ATLAS as pump laser at 1064 nm. The OPO obtained 9.2 mJ pulse energy at 1645 nm from 31.5 mJ of the pump and a
pump pulse duration of 42 ns. This corresponds to an optical/optical efficiency of 29%. After the pump pulse was
reduced to 24 ns, a similar OPO performance could be obtained by adapting the pump beam radius. In recent
experiments with optimized optical design the OPO obtained 12.5 mJ pulse energy at 1645 nm from 32.0 mJ of the
pump, corresponding to an optical/optical efficiency of 39%. Two different methods were applied to study the laser
damage thresholds of the optical elements used.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print format on
SPIE.org.