This work presents, to our knowledge, the first completely passive imaging with human-body-emitted radiation in the lower THz frequency range using a broadband uncooled detector. The sensor consists of a Si CMOS field-effect transistor with an integrated log-spiral THz antenna. This THz sensor was measured to exhibit a rather flat responsivity over the 0.1–1.5-THz frequency range, with values of the optical responsivity and noise-equivalent power of around 40 mA/W and 42 pW/ Hz , respectively. These values are in good agreement with simulations which suggest an even broader flat responsivity range exceeding 2.0 THz. The successful imaging demonstrates the impressive thermal sensitivity which can be achieved with such a sensor. Recording of a 2.3 × 7.5-cm 2 -sized image of the fingers of a hand with a pixel size of 1 mm 2 at a scanning speed of 1 mm/s leads to a signal-to-noise ratio of 2 and a noise-equivalent temperature difference of 4.4 K. This approach shows a new sensing approach with field-effect transistors as THz detectors which are usually used for active THz detection.

The spread of practical terahertz (THz) systems dedicated to the telecommunication, pharmacy, civil security, or medical markets requires the use of mainstream semiconductor technologies, such as complementary metal-oxide-semiconductor (CMOS) lines. In this paper, we discuss the operation of a CMOS-based free space all-electronic system operating near 250 GHz, exhibiting signal-to-noise ratio (SNR) with 62 dB in the direct detection regime for one Hz equivalent noise bandwidth. It combines the state-of-the-art detector based on CMOS field-effect-transistors (FET) and a harmonic voltage-controlled oscillator (VCO). Three generations of the oscillator circuit are presented, and the performance characterization techniques and their improvement are explained in detail. The manuscript presents different emitter–detector pair operation modalities, including spectroscopy and imaging.

This paper presents a fully-electronic wireless link operating at the 250 GHz frequency. The key elements of the developed system are the voltage-controlled harmonic oscillator implemented in 65 nm complementary metal-oxide-semiconductor technology (CMOS) and a quasi-optical detector with a resonantantenna- coupled field-effect transistor completed in 90 nm CMOS. The source is optimized for the third harmonic emission at 252 GHz with radiated power reaching up to –11 dBm (decibels with reference to one milliwatt) level. The detector has a resonance maximum of 254 GHz with a bandwidth of 25% and a minimal optical noise equivalent power of 22 pW/√−H−z . We employ an on-off keying technique for data coding and demonstrate digital signal transmission from 0.4 to 18 m distances. At 0.4 m distance and modulation frequency of 32 MHz, we achieve a 15.9 dB signal-to-noise ratio. The channel capacity of assembled communication link reaches 266 Mbit/s. However, it is limited by external electronic components – the amplifier and the modulator bandwidths. Implementing state-of-the-art high-frequency circuits should allow directly scaling the throughput to 10 Gbit/s.

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