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Schematic of the BC-FTIR system. (a) It consists of a light source assembly and a probe and detector assembly. The light source assembly combines a BLS, a Michelson interferometer including a fixed mirror 1, a movable mirror 2, a beam splitter (BS), an OC, and a PIR fiber. The modulated light is coupled into a PIR fiber using an optical coupler. The probe and detector assembly are made up of the sample placed on a bilayer cantilever probe, which simultaneously acts as the sample stage and heat flux probe. The deflection of the cantilever is measured by a PSD and the signal is post-processed using Fourier transform analysis. (b) The incident power of an interferogram-pattern from the PIR fiber. (c) The absorbed signal from the bilayer cantilever. The PSD records the bilayer cantilever deflection signal in the expected interferogram pattern (mirror velocity, ).
Background and intensity distribution calibrations of BC-FTIR system. (a) The incident power spectrum on the cantilever (background spectrum exiting from the PIR fiber), . The spectrum is calculated by taking the Fourier transform of the interferogram in Fig. 1(b) obtained through the FTIR system. (b) The background spectrum calibration. is the power spectrum leaving the FTIR system (before entering the PIR fiber) with different aperture sizes controlled by an iris called B-stop. (c) Beam intensity distribution leaving the PIR fiber, measured by an IR camera and fitted to a Gaussian profile with . (d) Top view of the bilayer cantilever, covering only a portion of the light coming out of the PIR fiber. (e) The intensity distribution from PIR fiber. (f) The incident intensity distribution on the bilayer cantilever. is the spatial integral of the intensity on the cantilever.
Frequency response and power calibrations of the BC-FTIR system. (a) The raw absorbed power spectrum calculated from the Fourier transform of the interferogram in Fig. 1(c) . (b) Experimental frequency response of the bilayer cantilever. (c) The schematic of the incoming, bypassed, reflected, and scattered power (d) Frequency response and power calibrations translate the vibrational amplitude on PSD to the absolute absorbed power of the cantilever.
Quantitative spectra of the Si/Al thin film. (a) The calibrated incident power spectrum. (b) The calibrated absorbed power spectrum. (c) The experimental and theoretical absorptance spectra. These spectra are measured with a mirror velocity of 0.03 cm/s and averaged over 50 scans.
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