Photon-pair generation based on superconductivity

Abstract

Superconductivity and optoelectronics have developed almost independently and had very rare interactions with each other in science and technologies. However recent interdisciplinary research opens up the potential for developing new optoelectronic devices. This review paper presents our recent theoretical and experimental demonstrations that superconductivity significantly modifies and accelerates photon generation processes. We have prepared superconducting light emitting diodes (LEDs) emitting at ∼ 1.6-μm optical-fiber communication band for the experimental demonstrations. This new-type LED operation is based on a unique physics related to Cooper-pair interband transition in a semiconductor, and further research leads to the solidstate simultaneously generated photon-pair sources for the potential application in quantum information and communication.

Optical observation of superconducting density of states in luminescence spectra of InAs quantum dots

“…This theory predicted luminescence enhancement near the SC DOS. Although we observed the predicted luminescence intensity enhancement, we could not observe any distinct variation of the luminescence spectra emitted from quantum well (QW) active layers of the SC LEDs [22,23,29,30].…”

Time-resolved measurements of Cooper-pair radiative recombination in InAs quantum dots

“…13 We also observed sharp reduction of the LED luminescence decay time constant with another SC-LED below T C , and also demonstrated a good agreement with our theory. 14,15 With these results, we evidenced the active role of Cooper pairs in radiative recombination in SC-LEDs.…”

“…The major term regulating the temperature dependence in this formula is D 2 /T, and the enhancement is proportional to the square of half the SC gap at a given temperature T and inversely proportional to T. 12 We could fit the observed enhancement in the previous SC-LEDs with this analytical formula. [13][14][15]30 The D 2 /T dependence results in more slowly varying temperature dependence than that shown in Fig. 5 and can be approximated for D 0 s 0 /h less than 0.2.…”

“…This also well reproduces our previous observation of decrease of the electroluminescence decay time constant in SC-LEDs. 14,15 These correlations of both the luminescence intensity and the decay time constant to the SC critical temperature are the clear evidence that the observed phenomenon is based on the Cooper-pair recombination in QDs penetrated from the Nb superconductor.…”

“…8 Cooper pairs are bosons and due to their coherent nature their number states are not fixed. 15 While Cooper pairs penetrate from the SC electrode into the semiconductor region, it is minority holes injected from the counter p-type electrode that regulate the photon emission process. In this regard, we proposed to control the QEPP generation process by regulating the hole-number states via the valence-band lowest quantum state of a QD under the Pauli's exclusion principle.…”