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We present an investigation of an ErAs:InAlGaAs photoconductive antenna receiver optimized for 1030 nm probe pulses at 24 mW THz power and show a dynamic range of 92 dB in 10 s measurement time. The saturation behavior under high THz average power is studied as well.

We use a high-sampling rate terahertz (THz) homodyne spectroscopy system to estimate thoracic movement from healthy subjects performing breathing at different frequencies. The THz system provides both the amplitude and phase of the THz wave. From the raw phase information, a motion signal is estimated. An electrocardiogram (ECG) signal is recorded with a polar chest strap to obtain ECG-derived respiration information. While the ECG showed sub-optimal performance for the purpose and only provided usable information for some subjects, the signal derived from the THz system showed good agreement with the measurement protocol. Over all the subjects, a root mean square estimation error of 1.40 BPM is obtained.