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(a) Experimental setup for the receiver noise temperature measurement. The inset shows the central part of the mixer chip. denotes the electric field of the LO signal, and are the LO powers, and and are the transmissions (see text). (b) Calculated beam radius vs the distance from the LO horn antenna along the path of LO signal shown in (a). Dotted vertical lines denote the position and the aperture radius of optical components.
Current-voltage characteristics of the SIS mixer pumped by the photonic LO. Arrows denote theoretical voltages of the first photon-assisted tunneling step corresponding to 250, 339, and .
Uncorrected DSB receiver noise temperature vs frequency. The SIS mixer is pumped either by a Ph-LO or three multiplier-based LOs (filled circles) driven by a microwave synthesizer or Gunn diodes with different bands (arrows; , , and denote each harmonic number). For Ph-LO, a two-thickness BS is adopted, in which the LO-mixer coupling of -thick BS (diamonds) is about two times as large as that of -thick BS (squares). The solid curve denotes the inverse of FTS responsivity with (right axis).
Frequency dependence of the output power of the photonic LO (solid line) and the maximum (Ref. 24) pumping power at the mixer input (filled square) calculated from and . The dashed line denotes the reported LO power requirement for a SBD fundamental mixer at room temperature.
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