| Objective: ||Demonstrate novel concepts for generating and amplifying ultrashort (fs-TW) laser pulses using architecture amenable to mobility at mid-infrared wavelengths, 2.0 - 4.0 microns.
|| Description: ||The Air Force is interested in promoting and conducting innovative research on promising new technologies relevant to the development of femtosecond Terawatt (fs-TW) laser systems that have a minimal number of optical elements, high average power, excellent beam quality, and are easily portable. Ultrashort pulsed laser technology has advanced rapidly in the last 10 years. Numerous domestic and international programs have demonstrated pulsed laser systems with peak powers in the Terawatt and even Petawatt ranges and average powers approaching the kilowatt (kW) level. These high intensity ultrashort lasers have been shown to have interesting propagation and materials interaction properties. Unfortunately, traditional ultrashort laser systems are complex and not particularly well suited for applications which require maintenance-free and mobile operation because they typically incorporate complicated optical trains with many reflective surfaces. Most of these femtosecond lasers operate at near-infrared wavelengths 0.7 – 1.1 microns. The ideal fs-TW system is one in which the oscillator and amplifiers are monolithic - a single solid-state material engineered to incorporate all of the optical elements necessary to generate and amplify an ultrashort laser pulse. In particular, the pulse stretching and compression techniques require complicated optical elements with large gratings. Potential oscillator candidates include mode-locked semiconductor lasers, fiber lasers, and solid-state laser oscillators. Potential amplifier candidates include semiconductor amplifiers, diode pumped fibers, diode or fiber laser pumped thin disks, and laser pumped gases (contained within a hollow core fiber). Candidate concepts must be capable of producing very high peak energy pulses, with high average power (that is high repetition rate) and excellent beam quality. Candidate materials might be but are not limited to: Er:YAG (2.94 microns), Ho:YAG (2.1 microns), Tm:YAG (2.0 microns), Cr:ZnSe (2.35 microns), in the range of 2.0 - 3.0 microns and semiconductor lasers operating in the 3.0 - 4.0 microns range. Furthermore, the overall system must have a high degree of reliability, require minimal maintenance, and have a variable pulse frequency and operational mode (eg.,kilohertz [kHz], sub-kHz, and burst mode operation). Finally, high overall energy efficiency is a critical consideration for mobility. System integration issues must be considered. For example, the individual components within the overall system must be compatible with one another and produce an efficient and conveniently packageable ultrashort pulsed laser system. The government is interested in mid-infrared lasers for a number of applications. It is understood that systems operating in the mid-infrared generally operate at lower peak powers and average powers. The purpose of this topic is to investigate mid-infrared ultrashort pulse laser technology that is scalable to higher peak powers and average powers. This effort will probably require a hybrid laser that includes multiple types of solid-state materials. Some of these materials may require development to accomplish the goals of the SBIR.
|| ||PHASE I: Identify, model, and/or demonstrate a promising mid-infrared, ultrashort pulse, fs-TW laser system or components. Although laboratory demonstrations may be beyond the scope of a Phase I effort, a clear scaling path including component demonstrations and modeling to the desired power is essential.
|| || ||PHASE II: Model, build, and demonstrate a suitable mid-infrared, ultrashort pulse, fs-TW laser system that meets the notional requirements identified above. If appropriate, build and demonstrate a portable prototype version of the system. Initiate system studies to determine packaging, size, and weight requirements for the overall system.
|| ||DUAL USE COMMERCIALIZATION: Military application: The transportable laser developed under this project has potential non-lethal applications in the 2 – 3 and infrared countermeasures applications in the 3 – 4 micron range. Commercial application: Possible applications include biomedical applications, industrial welding, beacons and illuminators for upper atmosphere remote sensing, and as a portable source for material interaction studies.
|| References: ||1. Limpert, J., et. al., “All fiber chirped pulse amplification system based on compression in air-guiding photonic bandgap fiber,” Opt. Expr., 11(24), 3332 – 3337, 2003.
2. Imeshev, G. and Fernmann, M. E., “230-kW peak power femtosecond pulses from a high power tunable source based on amplification in Tm-doped fiber,” Opt. Expr. 13(19), 7424-7431, 2005.
3. Limpert, J., et. Al., High power femtosecond Yb- doped fiber amplifier, Opt. Expr. 10(14), 628-638, 2002.
4. Teodoro, F. D., et. al., “Diffraction-Limited, 300-kW Peak-Power Pulses from a Coiled Multimode Fiber Amplifier,” Opt. Lett. 27(7), 518-520, 2002.
5. Carrig, T. J. and Wagner, G. J., "Mode-locked Cr 2+ ZnSe laser," Opt. Lett. 25(3), 168-170 (2000).|
|Keywords: ||ultrashort lasers, femtosecond (fs)-terawatt (TW) lasers, pulsed lasers, lasers, mid-infrared lasers|