EPIc-HOFGLAS- Electrically Pumped Intense Hollow-core Optical Fiber Gas LASer - A New Approach for Mid-wave Infrared Directed Energy and Electronic Warfare Sources
Abstract
Hollow-core Optical Fiber Gas LASers (HOFGLAS) in the 3-5 micrometer mid-wave infrared (MWIR) band have attracted much attention in recent years [1], for potential applications in directed energy, infrared (IR) countermeasures and long range atmospheric penetration through clouds, fog, aerosols [2, 3]. Traditional silica solid core optical Fiber lasers, the current frontrunner in directed energy and electronic warfare high power applications [4, 5], are fundamentally limited in their power-intensity scalability. Unwanted nonlinear effects in the solid fiber core occur above a threshold intensity, such as thermal mode instabilities (TMI) and stimulated Raman-Brillouin scattering (SRS-SBS) processes, coupled with thermal lens-intensity related damage mechanisms. HOFGLAS systems have the potential to raise these limiting thresholds many orders of magnitude [6], as the high intensity laser light propagates in a gas, rather than a solid silica, core, minimising nonlinear effects and damage mechanisms [7]. This means the output power of HOFGLASs could potentially be many orders of magnitude higher than existing high power solid core Fiber laser systems. The other exciting feature of HOFGLASs is their ability to emit light directly in the MWIR. High power solid core fiber laser systems emit in the near-infrared, around 1 micrometer. Many key defence applications, however, require high power MWIR radiation. Directly emitting pulsed MWIR sources are scarce, instead complicated multistep conversion systems are often used which have low overall wallplug efficiencies. Hence, HOFGLAS systems have been intensively studied in the last decade (funded largely by the AFRL and AFOSR) as a possible holy grail in the search for an ultra-intense MWIR laser source. To date, however, this promise has failed to materialise. This is because all HOFGLASs have been optically pumped [1, 6, 8, 9, 10, 11]. Optical pumping is often stated as an advantage, but actually has fundamental issues. Ion bombardment causes damage at the pump laser entry point; a large quantum defect between the pump and lasing lines (near-infrared versus MWIR) result in low system efficiencies and large amounts of heat deposition in the gas, leading to TMI and other issues; finally, high power (more than10 W) narrow linewidth pump sources necessary to achieve population inversion are simply not available at the required molecular absorption lines. These features all prevent the HOFGLAS architecture from reaching its true potential.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2023
- Source ID
- FA86552217006
Entities
People
- Robbie Murray
Organizations
- Air Force Office of Scientific Research
- Imperial College London
- United States Air Force