Ultra-Broadband Terahertz Time-Domain Sensing for Space Exploration

              Femtosecond lasers have in recent years been shown to be compact, robust and space qualified [1,2], thereby so called, time-domain spectroscopy (TDS) techniques, which allow to avoid complex detector systems and/or bulky opto-mechanics of conventional instruments such as Fourier-Transform Interferometers or grating spectrometers become viable options for more compact, energy/mass efficient and performant space instruments [3,4].  In this contribution we show how terahertz (THz) TDS emerges as an alternative to conventional infrared spectrometers in the spectral range of 10 – 1000 cm-1 (0.3 to 30 THz). Progress towards space qualification and chip integration is presented and future use cases such are THz TDS in attenuated total reflection (ATR) geometry are discussed.

 

Figure 1: Plot showing the evolution of solid-state laser systems since 1975 and their corresponding spectral bandwidth.

Figure 2:  Broadband spectrum of spintronic THz emitters

Figure 3: THz TDS in ATR geometry and schematic diagram of intergration of THz TDS for space exploration on fiber platform.

 

    References

[1] J. Lee, K. Lee, Y. Jang, et al. “Testing of a femtosecond pulse laser in outer space,” Scientific Reports 4, 5134, (2014).

[2] M. Lezius, T. Wilken, C. Deutsch, et al., “Space-borne frequency comb metrology,” Optica 3, 1381 (2016).

[3] O. Gueckstock, N. Stojanovic, Y. Ha, et al, “Radiation hardness of ultrabroadband spintronic terahertz emitters: En-route to a space-qualified terahertz time-domain gas spectrometer,” Applied Physics Letters 124, 141103 (2024).

[4] Y. Ha, S.G. Pavlov, M.D. Rabasovic, et al., “Time-Domain Raman Spectroscopy: An Emerging Technique in Space Exploration,” J. Raman Spectrosc. 56, 916 (2025).