KINETIC INDUCTANCE THZ MIXER FOR SPACE APPLICATIONS

We consider a new type of hot-electron mixer that employs a kinetic-inductance response in a superconducting film near superconducting transition. The significant advantage of this mixer over the resistive one is that the intermediate frequency bandwidth and the local oscillator power can be adjusted independently. The intermediate frequency bandwidth is determined by the inverse quasiparticles multiplication time. The local oscillator power is determined by the electron cooling time, which is the electron-phonon relaxation time for phonon-cooled mixers. Our modeling has shown that the intermediate frequency bandwidth can be as large as 50 GHz along with the local oscillator power of about 10 nW and the conversion efficiency — 0.01. Currently, hot-electron superconducting bolometer (HEB) mixers are the most sensitive heterodyne detectors at THz frequencies. Both the diffusion and the phonon cooled HEB mixers demonstrate very good noise characteristics [1,2]. The achieved noise temperature in practical mixers is approximately 10 times higher than the quantum limit, TQ = hv/kB. The intermediate frequency (IF) bandwidth, BIT', is given by the inverse electron cooling time, 1-c, i.e., BIF = 142 Irr,). The maximum IF bandwidth of GHz has been demonstrated in an ultrashort diffusion-cooled Nb mixer [3]. The local oscillator (LO) power of an HEB mixer is PLO-'----CeToire °c. T 2 /r, where Ce is the electron heat capacity. Typical low values for the LO power are in the range 20-100 nW [3]. A further decrease of the LO power in HEB mixers can be achieved by using superconductors with lower critical temperature [4]. In the current work, we analyze a new type of hot-electron mixer, which employs a kinetic-inductance response in a superconducting film in the vicinity of the superconducting transition. This mixer allows for substantial increase of the IF bandwidth and simultaneous decrease of the LO power. The kinetic inductance response to the electromagnetic radiation near the superconducting transition has been studied in many works [5,6,7,8]. The radiation a