Application of plasmon-resonant microchip emitters to broadband terahertz spectroscopic measurement

We are proposing our original 2D-plasmon-resonant microchip emitter as a new terahertz light source. The structure is based on a high-electron-mobility transistor and features interdigitated dual-grating gates. The dual-grating gates can alternately modulate the 2D electron densities to periodically distribute the plasmonic cavities along the channel, acting as an antenna. The die fabricated in a 70 μm square with a double-deck InGaP/InGaAs/GaAs material system can emit 0.5-6.5 THz radiation with microwatt power even at room temperature from self-oscillating 2D plasmons under the DC-biased conditions. The microchip emitter was introduced into a Fourier-transformed far-infrared spectrometer as a light source. Its applicability to broadband terahertz spectroscopy was verified through real measurements for atmospheric water vapor and several sugar groups.