  We present a superconducting noise bolometer for terahertz radiation, which
is suitable for large-format arrays. It is based on an antenna-coupled
superconducting micro-bridge embedded in a high-quality factor superconducting
resonator for a microwave bias and readout with frequency-division multiplexing
in the GHz range. The micro-bridge is kept below its critical temperature and
biased with a microwave current of slightly lower amplitude than the critical
current of the micro-bridge. The response of the detector is the rate of
superconducting fluctuations, which depends exponentially on the concentration
of quasiparticles in the micro-bridge. Excess quasiparticles are generated by
an incident THz signal. Since the quasiparticle lifetime increases
exponentially at lower operation temperature, the noise equivalent power
rapidly decreases. This approach allows for large arrays of noise bolometers
operating above 1 K with sensitivity, limited by 300-K background noise.
Moreover, the response of the bolometer always dominates the noise of the
readout due to relatively large amplitude of the bias current. We performed a
feasibility study on a proof-of-concept device with a ${1.0\times 0.5 \rm \mu
m^{2}}$ micro-bridge from a 9-nm thin Nb film on a sapphire substrate. Having a
critical temperature of 5.8 K, it operates at 4.2 K and is biased at the
frequency 5.6 GHz. For the quasioptical input at 0.65 THz, we measured the
noise equivalent power ${\approx 3\times 10^{-12}\rm W/\sqrt Hz}$ , which is
close to expectations for this particular device in the noise-response regime.
