Mid Wave Infrared Gas Filled Hollow Core Fiber Lasers for Counter IR Sensors
Abstract
Hollow optical fibers have been developed over the past 20 years in Bath. The most recent generation are based on an anti resonant guidance mechanism and have presented a step change in both performance and manufacturability. Performance in the mid infrared is particularly striking. The very first fibers offered a propagation loss of 30 dB-km at 3.2 µm wavelength, which is more than 5000x less than the attenuation of the silica glass from which the fiber was made, and is amongst the lowest attenuation of any fiber made of any material at this wavelength[. Since then we have made progress in the understanding of the fiber design and in fiber performance in the infrared[3] and mid infrared laser applications[4,5,6]. Current fibers designed for the mid infrared have attenuation of less than 0.05 dB-m at 4 µm. Beyond 4 µm, atmospheric CO2 and the reducing sensitivity of our spectrometer mean it is not possible to measure the attenuation, which is expected to remain low to 4.5 µm or beyond. Using our hollow optical fibers we have demonstrated three different regimes of mid infrared generation in gases. Raman conversion in hydrogen filled fibers was demonstrated using a pulsed pump laser at 1064 nm and conversion to 1900 nm. This process is also expected to yield tunable mid infrared wavelengths from a pump around 1550 nm. Optically pumped acetylene gas was demonstrated in pulsed and CW mode, with low threshold, high efficiency, and output power greater than 1 W (pump limited). These advances in mid infrared hollow optical fibers for mid infrared lasers shows promise for AFRL research in mid infrared lasers. The fiber architecture is particularly important for flexibility and robustness of integration into airframes.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- FA95501927000
Entities
People
- William Wadsworth
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Bath