Ultrafast Infrared Laser System at High Peak and Average Power with a Unique High Power Combiner at 2 µm

The 300 fs laser with average power up to 3 kW at 2 m will be one of the key components needed to advance accelerator technology, particularly for energy recovery linear accelerators and free-electron lasers FELs). These types of accelerators are used in fundamental studies involving a wide range of disciplines including sub-atomic particle physics, material sciences, life sciences, chemistry, etc. Applied areas where accelerators can or do have an impact are archaeology, cancer treatment, homeland security and defense. A Thulium doped fiber amplifier with a novel high power signal/pump combiner is proposed to enable the ultrafast laser to achieve up to 3 kW average power. The combiner can transmit more than 3 kW signal power at 2 m in the core and multi-kW pump power at 793 nm in the cladding so that a few power stage chains can be cascaded to increase the power without components damage due to absorption of the 2 m light. In Phase I a combiner to enable the cascading will be designed and built. In Phase II a deliverable Tm:fiber amplifier with power up to 3 kW will be developed based on this combiner. In Phase III a complete ultrafast laser system with up to 3 kW average power can be built and tested. A specialty fiber will be modeled and simulated using FimmWave. Specifications will be provided to a fiber manufacturer for production. A standard end-pumped high power combiner currently used for fiber amplifiers will be built with COTS components to obtain optimal parameters for the specialty combiner building and tested with single mode light coupled into the special combiner. Thereafter a combiner with the specialty fiber will be built based on the parameters from the standard ones. The combiner will be tested with low pump power and signal power. Ultrafast high power lasers meet the near-term needs for accelerator colliders. Multi-kW continuous wavelength lasers at 2 m are also needed in directed energy applications largely due to their more eye- safe characteristics. In industrial market, cutting and welding of thick rubber, plastic, and many special materials are asking for this special wavelength and high power beyond kW level.