arXiv subjects
Publications and source records attributed to P. Haring Bolivar.
We evaluate 2 thermopile sensors as convenient detector options for a modern integrated THz imaging system. Both a commercial single pixel device and a 32x32 pixel FPA are utilized in a simple setup with a single optical element to achieve an outstanding resolution and SNR performance. Either a cryogenically cooled quantum cascade laser (QCL) or a room temperature electronic THz multiplier chain is used as source.
Integrating a thermopile with a low power operational amplifier is an effective and cost-efficient approach to obtain a high performance compact Terahertz power detector. Here we present the development of such an integrated detector, including the fundamental building blocks, the final realization and related characterization. The responsivity and bandwidth of the detector are measured in a standard THz CW setup consisting of a closed cycle helium cryostat and a Quantum Cascade Laser (QCL). The predicted results are compared with measured data, showing a good agreement. Advantages of existing Golay cell THz detectors in both sensitivity and NEP figure vanish, in practical use, due to the enormous increment in dynamic range provided by the linear operation of the thermopile up to 100 mW of incident power while offering a NEP below 1nW/sqrt(Hz) and a -3dB bandwidth of 6,8 Hz.
A time-resolved analysis of the amplitude and phase of THz pulses propagating through three-dimensional photonic crystals is presented. Single-cycle pulses of THz radiation allow measurements over a wide frequency range, spanning more than an octave below, at and above the bandgap of strongly dispersive photonic crystals. Transmission data provide evidence for slow group velocities at the photonic band edges and for superluminal transmission at frequencies in the gap. Our experimental results are in good agreement with finite-difference-time-domain simulations.