Fig. 1: Schematic representation of the infrared measurement setup. | Communications Physics

Fig. 1: Schematic representation of the infrared measurement setup.

From: Uncooled thermal infrared detection near the fundamental limit using a silicon nitride nanomechanical resonator with a broadband absorber

Fig. 1

The resonator is housed inside a copper block, which is placed within a vacuum chamber. A laser vibrometer probes the membrane’s vibration through the upper optical aperture. The signal is fed into a lock-in amplifier with a phase-locked loop (PLL) that continuously corrects the phase error between the membrane’s oscillation and the internal oscillator, ensuring accurate tracking of the resonance frequency and controlling the actuation frequency of the piezoelectric element. For thermal characterization, an infrared source is coupled into an optical fiber and focused onto the resonator using two gold-coated parabolic mirrors through the bottom optical aperture. The infrared beam is modulated by an optical chopper positioned between the mirrors. The lock-in amplifier output is recorded for later analysis. Inset: optical microscope picture of a 1 mm membrane featuring a free-space impedance-matched absorber, showing a circular clearance for the readout laser. Scale bar is 200 μm.

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