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Physics of proximity Josephson sensor
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View: Figures


Image of FIG. 1.
FIG. 1.

Illustration of the detector with normal (N) and superconducting (S) components. Incident radiation is coupled to the normal-conducting absorber via the antennas in contact to the superconductors.

Image of FIG. 2.
FIG. 2.

Critical Josephson current as a function of electron temperature . We use ratio for , corresponding to Nb energy gap .

Image of FIG. 3.
FIG. 3.

Relative contributions to the electron energy balance of the system defined in Eq. (2). At all energies , the magnitude of the input (radiation contribution) must equal to the sum of the magnitudes of the other three processes which contribute to energy relaxation. The result is obtained for a typical set of operating and materials parameters and, most notably, and .

Image of FIG. 4.
FIG. 4.

Fraction of incident radiation power converted into thermal response in a PJS detector. The results are given as a function of for and as a function of for (inset). The curves are obtained for a typical set of materials parameters defined in Sec. II B.

Image of FIG. 5.
FIG. 5.

Nonequilibrium distribution resulting from irradiation and a set of relevant equilibrium distributions. Notice that the curves for the actual nonequilibrium distribution and the equilibrium distribution used to approximate this are nearly on top of each other. The difference between these two is magnified in the inset. The figure is obtained for the same set of parameters used in Fig. 3. In this case the input power is large so that the bath temperature is small compared to the final . Here , so is also clearly smaller than the temperature of an equivalent equilibrium system heated with the same power, .

Image of FIG. 6.
FIG. 6.

Comparison between numerical result for thermal conductance of the electron-phonon heat link and two exponential fitting curves: one valid to good degree of accuracy for (green) and one, where the suppression of is determined by the energy minigap (red). is given in proportion to the thermal conductance in the incoherent case.

Image of FIG. 7.
FIG. 7.

Nonequilibrium noise of the PJS under heating , with (coherent—red) and without (incoherent—blue) the corrections from the proximity effect. We compare the exact results to the analytical approximations of Eqs. (10) (incoherent) and Eq. (7) (coherent) valid at the limits and (dashed lines). In the inset, we show how the noise of the coherent system can be approximated by the exponential law of Eq. (7) (dashed line) for a large temperature range.

Image of FIG. 8.
FIG. 8.

Base NEP (with negligible power load) for proximity and normal conductor as function of . The proximity effect decreases NEP by the factor in our example at .

Image of FIG. 9.
FIG. 9.

Comparison between the numerical result for the electronic heat capacity of the coherent (proximity) and the incoherent case.

Image of FIG. 10.
FIG. 10.

Time constant of the PJS as a function of electron temperature on a log-log scale. The coherent corrections from the proximity effect (red) are compared to the incoherent result (blue).

Image of FIG. 11.
FIG. 11.

Detector resolving power for some operating temperatures. Note that the curves for are nearly on top of each other.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Physics of proximity Josephson sensor