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Tunable mid-infrared emission is highly applicable in the fields of molecular spectroscopy and atmospheric monitoring. Recent studies have demonstrated that external electric fields can induce non-zero optical bandgaps of up to 250 meV in graphene materials, thereby paving the way for mid-infrared emissions (3–14 μm) to be realized. Graphene foam (GF) possesses a unique highly porous microstructure, which allows intense reflection or scattering of incident photons and gives rise to efficient interband optical absorption. Enhanced electron–phonon coupling enables free electrons in the conduction band to relax non-radiatively to the 1s-state. Mid-infrared emission is generated owing to electron–hole recombination. In this work, we demonstrate the induction of widely tunable (2.9–8.6 μm) mid-infrared emission in GF by modulated visible laser diode (LD) light with modulation frequencies ranging from 1.5 to 0.5 kHz. The peak emission wavelength correlates with the modulation frequency and is independent of the wavelength of LD light of visible range, whereas the emission intensity is related to the alternating intensity of the LD. Our findings indicate that GF is not only a novel mid-infrared emitting material, but one that promises bandgap flexibility for widely tunable mid-infrared sources.

An uncooled infrared focal plane array (FPA) for a multiband optical imaging system monitoring small gas leakages is low in cost but limited by its frame rate and sensitivity. We propose the concept of Archimedean spiral push-broom filtering (ASPBF), where the trajectory of an Archimedean spiral over the FPA is approximated as a straight line. The ASPBF precisely matches the electronic pulse scanning of the uncooled infrared FPA row by row to improve the frame rate. We applied differential imaging to promote gas detection sensitivity. Prototype can detect 11 ml/min of ethylene gas at ΔT = 3 °C with frame rate of 8 fps.