A photopyroelectric spectrometer with real-time and(or) self-normalization capability was used for both conventional transmission and thermal-wave spectroscopic measurements of amorphous Si thin films, deposited on crystalline Si substrates. Optical-absorption-coefficient spectra were obtained from these measurements and the superior dynamic range of the out-of-phase (quadrature) photopyroelectric signal was established as the preferred measurement method, owing to its zero-background compensation capability. An extension of a photopyroelectric theoretical model was established and successfully tested in the determination of the optical absorption coefficient and the thermal diffusivity of the sample under investigation. Instrumental sensitivity limits of βt ≈ 5 × 10−3 were demonstrated.
Adaptive Background Compensation of Frequency Interleaved DACs with Application to Coherent Optical Transceivers
