Emerging Thermal Infrared ‘THz Torch’ Technology for Low-Cost Security and Defence Applications

Abstract

AbstractTerahertz (THz) systems are notoriously large and very expensive, from complete systems down to individual front-end active devices and passive components. This is a major reason why there are currently no ubiquitous applications in the terahertz frequency spectrum (from 0.3 to 10 THz). However, by moving into the high-THz part of the frequency spectrum (thermal infrared region, from 10 to 100 THz), for specific niche applications, it is possible to create affordable systems for commercial exploitation.The thermal infrared frequency bands, typically from 20–40 THz and 60–100 THz, are best known for applications in thermography. This underused and unregulated part of the spectral range offers opportunities for the development of secure communications. To this end, the ‘THz Torch’ concept was recently presented. This technology fundamentally exploits ultra-low cost engineered blackbody radiation, by partitioning thermally-generated spectral noise power into pre-defined frequency channels; the energy in each channel is then independently pulsed modulated and transmitted, creating a robust form of short-range secure communications in the far/mid infrared.In this Chapter, the basic THz Torch architecture for short-range secure wireless communications is introduced. Single-channel working demonstrator from 25 to 50 THz is shown. This concept is further extended by multiplexing schemes with important benefits, including increased overall end-to-end data rates (with band-limited channels) and higher levels of security. Multi-channel ‘THz Torch’ frequency division multiplexing (FDM) and frequency-hopping spread-spectrum (FHSS) schemes are introduced and the first proof-of-concept FDM working demonstrator is presented. Furthermore, fundamental limits and engineering solution are discussed to increase the data rate and transmission range.By exploring a diverse range of methods, significant enhancements to both data rate and distance can be expected. Our thermodynamics-based approach represents a new paradigm in the sense that nineteenth century physics can be exploited with twentieth century multiplexing concepts for low-cost twenty-first century ubiquitous security and defence applications in the thermal infrared.KeywordsPower Conversion EfficiencySpectral RadiancePyroelectric SensorThermal Time ConstantGlass EnvelopeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.