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In recent years, high power fiber and semiconductor laser technology has improved rapidly, with power density increasing by an order of magnitude or more. Much of this increase has been driven by demand for industrial cutting machines and high-bandwidth, long-range telecommunications. These same laser materials and devices can also be used as directed energy weapons against personnel and electro-optical and infrared (EO/IR) sensors. Purposeful laser strikes on aircraft have increased rapidly over the last decade. In 2018, the Wall Street Journal reported that hostile forces have been lasing American planes with laser pointers at a growing rate and these irradiance incidents have the potential to affect the operation of EO/IR sensors.
DARPA notes that laser weapons are being improved using technology from civilian industries. “In recent years, high-power fiber and semiconductor laser technology has improved rapidly, with power density increasing by an order of magnitude or more. Much of this increase has been driven by demand for industrial cutting machines and high-bandwidth, long-range telecommunications,” says the agency. “These same laser materials and devices can also be used by directed-energy weapons for both destructive and deteriorating effects, such as temporary blinding or degrading electro-optical/infrared sensors.”Because lasers are also becoming more powerful in the future the weapons might also be capable of damaging aircraft components, light vehicles, munitions or causing injury to soldiers, DARPA says.
Lasers are a source of collimated, monochromatic, coherent light that can travel long distances with very little loss of intensity. This coherent property is what allows a laser to maintain a narrow, high-powered beam over long distances. This is also the cause of lasers being able to do damage to sensors, facilities, and personnel at a long range. Military Lasers can also causes damage to optical components like mirrors, fibers, nonlinear crystal materials, prisms, optical filters, optical modulators and saturable absorbers, photodetectors and SESAMs.
Small, lightweight, high-energy laser systems are a reality today due to decades of research activity. High power, small footprint lasers enable deployment of mobile and transportable high-energy laser systems. The small form factor makes these systems easy to disguise and bring into environments without detection. For example, such systems could be hidden in a delivery van or in a truck carrying supplies. Small lasers could be hidden in a backpack and carried into public venues. Given these advances in laser technology, there exists a need for low SWaP laser detection systems that are easily transportable and work in both day and night conditions to alert personnel of active lasing.
DOD in an industry request for information on October 2019 wants an outfit as a counter measure that could be mounted on aircraft, as well as ground vehicles or ships, it says. DARPA is looking for anti-laser defensive technology ideas that can detect an attack, geo-locate the attacker and disrupt the laser weapon’s kill chain within milliseconds of an attack starting. The agency says its ideal defensive system would do all three functions, though it is open to considering a system that does just one or two functions.
DARPA is looking for counter measures that have been developed to a technology readiness level three. Such a state of technology is still relatively immature, with only analytical and laboratory studies completed, and proof-of-concept model constructed, according to a NASA definition. “Initial concepts that rapidly lead to field demonstrations of a tactical platform at relevant scales are of particular interest,” the research and develop organization says. DARPA says it is strongly interested in a “pre-fire” system, a defensive measure which finds and stops a laser weapon before the attack.
DARPA lists one challenge to the project as being “off-axis detection of scattered laser irradiation at long standoff distances, particularly methods to detect weak scattering above high ambient light conditions.” “Approaches that disrupt the [high-energy laser] kill chain, as well as approaches that harden platforms and munitions to allow a kinetic attack on [high-energy laser] systems are of interest,” it says.
DARPA is also looking at Material solutions that protect against HEL attack and enable completion of the mission, including Counter High Energy Laser missions, during such an attack. Other solution is collaboration of multiple fielded HEL counter-weapon systems to include realtime cooperative sensing and data processing. The agency also wants ideas for multiple platforms, such as different aircraft, ground vehicles or ships, to be able to share information about potential or incoming attacks.
Wearable Laser Detection and Alert System
In Aprril 2020, Officials of the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., issued a small-business innovation research (SBIR) solicitation (HR001120S0019-05) for the Wearable Laser Detection and Alert System. DARPA researchers want to understand the feasibility of a wearable laser sensor that can detect laser irradiation rapidly during the day and at night and alert the wearer in real-time of lasing.
Objective is to develop a lightweight (~100 grams or less) laser alert sensor system that can act as a stand-alone system and be personnel-wearable that can detect laser irradiation from 450 to 1600 nanometers at energies of 500 microwatts/cm2 and greater to warn personnel of potential ocular damage or damage to electro-optical and infrared sensors in near-real time. The wearable system should be very lightweight and comfortable to wear and work through all natural environmental and lighting conditions. The system should also be compatible with integration into standard civil and military issued headgear without significantly increasing the bulkiness or weight.
Broadband coverage is desired but solutions that detect a subset of wavelengths to include 532, 632, 1064, 1300, and 1550 nm and meet all other requirements of this solicitation may also be considered. The system must operate in both day and night conditions with a continuous 2-pi steradian field of view. The wearable sensor must be powered by a battery system that is less than 1.5 kg (to include both battery and connectors) and operates for at least 72 hours on a single charge. The laser alert system should detect only laser irradiation and not other background sources.
The system should not react to bright non-laser sources such as solar phenomenon, flares, background light, thermal light, headlights, rocket plumes, muzzle flashes, and other sudden bursts of high intensity light not related to laser illumination as these would be considered system false alarms and degrade functional performance. This feature of the system is anticipated to be a hard technical challenge to address particularly in a low SWaP system, but will be critical for a successful demonstration.
Successful proposals will provide a feasibility study for developing a laser detection system that meets the criteria of the objective system. This will include modeling and simulation that leads to both an achievable breadboard intermediate unit (Phase I) and an initial prototype (Phase II). Proposals should identify commercial off-the-shelf sensors or components that can be used to demonstrate the system objectives within the cost and time constraints of this effort. Proposals offering to do extensive trade studies without a defined path to achieving the objectives of this topic are discouraged. A detection technique that enables location information for the high energy weapon source would be desirable feature of the system but is not a requirement. The system should detect both continuous wave lasers and pulsed lasers.
Phase I
Evaluate concepts to detect irradiation in the band of 450-1600 nm in both day and night lighting conditions at energies of 500 microwatt/cm2 and above. These approaches should include a method to detect coherent laser irradiation and differentiate coherent laser illumination from incoherent spikes above the ambient background. Solutions to liminate a bright daytime background and reduce system SWaP should also be investigated.
Phase II
Develop and demonstrate wearable laser detection and alert technology that meets or exceeds all of the requirements listed in Table 1. Test and deliver a working
prototype. Prototype includes a wearable system and a system integrated into a standard civil/military issued helmet or head-set.
Maturation of this technology would greatly benefit the Department of Defense (DoD) mission in many areas including force protection. This technology has significant commercialization potential. The proliferation of laser technology poses significant risks to commercial aircraft pilots during takeoff and landing operations. A successful system demonstration is expected to yield significant interest in the airline and commercial aviation industry. A secondary market for a laser detection system is civil and law enforcement personnel deployed in the field.
