A Solution to Baseline Uncertainty Due to MCT Detector Nonlinearity in FT-IR

Abstract

High-sensitivity mercury-cadmium-teluride (MCT) detectors have generally been used in low-light experiments and where quantitation was not essential. These restrictions were commonly believed to be associated with the nonlinear response of the detectors due to intrinsic limitations of the detection process. Recent preamplifier and bias circuit designs have made significant gains in reducing and, in the case of the broadband MCTs, virtually eliminating the nonlinear character of these detectors in typical FT-IR applications. This improvement in performance in achieved through a change in detector biasing from constant current to constant voltage.

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

“…Cool down the MCT detector dewar with liquid nitrogen. Note: The use of photovoltaic MCT detectors is preferred over photoconductives because of their linear response and, thus, superior photometric accuracy and baseline reliability 31,53 . 5.…”

A new approach for sensing and measuring the incident radiation on semiconductor mercury-cadmium-telluride (MCT) detector

“…Thus, the recorded signal will not be exactly corresponding to the incident radiation. While experimental results have been reported for confirming the improved linearity of the constant voltage-biased MCT detector [4], no attempt has been reported, in the open literature, to predict the amplitudes of the harmonic and intermodulation components in the recorded voltage as a result of the nonlinear relationship of equation (2). In its present form equation (2) cannot yield closed-form expressions for these unwanted components.…”

“…Since the nonlinear function is the same for both the constant current-and constant voltage-biased MCT detectors then it is obvious why the harmonic and intermodulation performances of both detectors are identical. Thus, the improvement in the nonlinear performance of the constant voltage-biased MCT detector reported in [4] cannot be attributed to the use of constant voltage-biasing rather than constant current-biasing. It appears that this improvement is attributed to the use of feedback linearization in association with the constant voltage-biasing as mentioned in [4]. )…”

“…Because the MCT detector conducts current in the dark, its resistance is not simply inversely proportional to the incident radiation and thus, the recorded amplitude of an interferogram will not be linearly proportional to the light intensity on the detector during acquisition. Attempts to improve the linearity of MCT detector-based measurements using different approaches have, therefore, been reported in the open literature [2]- [4]. Of particular interest here is the method proposed in [4] and based on changing the biasing of the MCT detector from constant current-biased to constant voltage-biased.…”

“…Attempts to improve the linearity of MCT detector-based measurements using different approaches have, therefore, been reported in the open literature [2]- [4]. Of particular interest here is the method proposed in [4] and based on changing the biasing of the MCT detector from constant current-biased to constant voltage-biased. The major intention of this paper is to revisit this approach first by proposing a new constant voltage-biased circuit for the MCT detector and second by performing large signal analysis for the resulting MCT detector.…”