High-energy laser detection through thermoelectric generators

Joseph Merkel,Cody Brownell,Steven Yee,Peter Joyce,Charles Nelson,Brian Jenkins,Hatem Elbidweihy,Deborah Mechtel

doi:10.1117/1.oe.59.11.117105

Joseph Merkel, Cody Brownell + Show 6 more

Open Access

https://doi.org/10.1117/1.oe.59.11.117105

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Abstract

Detection of high-energy laser strikes is key to the survivability of military assets in future warfare. The introduction of laser weapon systems demands the capability to quickly detect these strikes without disrupting the stealth capability of military craft with active sensing technologies. We explored the use of thermoelectric generators (TEGs) as self-powered passive sensors to detect such strikes. Experiments were conducted using lasers of various power ratings, wavelengths, and beam sizes to strike 2 × 2 cm2 commercially available TEGs arranged in different configurations. Open-circuit voltage and short-circuit current responses of TEGs struck with 808-, 1070-, and 1980-nm lasers at irradiance levels between 8.5 and 509.3 W / cm2 and spot sizes between 2 and 8 mm are compared. TEG surface temperatures indicate that the sensor can survive temperatures nearing 400°C. TEG open-circuit voltage magnitudes correlate more strongly with net incident laser power than with specific irradiance levels, and linearity is limited by Seebeck coefficient variation with temperature. Open-circuit voltage responses are characterized by 10% to 90% rise times of ∼2 to 10 s despite surface temperatures not reaching equilibrium. With open-circuit voltage as the sensing parameter, detection thresholds three times above the standard deviation noise level can be exceeded within 300 ms of the start of a laser strike with irradiance levels of ∼200 W / cm2. Potential harvested power levels as high as 16 mW are estimated based on measured electrical responses. A multiphysics finite-element model corresponding to the experiments was developed to further optimization of a lightweight, low-profile TEG sensor for detection of high-energy laser strikes.

Highlights

Laser weapon systems are difficult to detect because they are both silent and invisible
A forward-looking infrared system (FLIR) A615 IR camera was used to record the temperatures on the front of the thermoelectric generators (TEGs) for the 1070- and 1980-nm laser strikes, and an FLIR A325sc IR camera was used to record the temperatures on the front and back of the TEG for the 808-nm laser strikes
The basic functionality of a TEG as a passive sensor for near-IR laser irradiation is verified by experiment and simulation

Summary

Introduction

Laser weapon systems are difficult to detect because they are both silent and invisible. The only methods of detection are to receive the laser radiation into an optical system or to detect an increase in temperature on the target. Assets such as tanks, aircraft, ships, and drones need to operate independently, which means an extra asset deployed solely for detecting laser radiation via an IR camera is less practical. Companies such as Boeing and Carl Zeiss have patented other technologies that include an externally mounted device on the asset to receive laser radiation.[1,2] Both technologies are bulky and can be mounted to a limited set of platforms. Embedded photoconductive sensing techniques have been investigated but required direct

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