Noncollinear parametric fluorescence by chirped quasi-phase matching for monocycle temporal entanglement

TL;DR

This paper demonstrates that noncollinear quasi-phase matching with a modest chirp in the poling period can generate ultrabroadband, monocycle temporal entanglement in photon pairs, surpassing previous collinear approaches in bandwidth.

Contribution

It introduces a noncollinear SPDC scheme with chirped QPM, achieving record bandwidth and monocycle entanglement with less chirp than collinear methods.

Findings

Achieved 194 THz bandwidth in noncollinear SPDC.

Demonstrated monocycle temporal entanglement potential.

Experimental validation of ultrabroad parametric fluorescence.

Abstract

Quantum entanglement of two photons created by spontaneous parametric downconversion (SPDC) can be used to probe quantum optical phenomena during a single cycle of light. Harris [Phys. Rev. Lett. 98, 063602 (2007)] suggested using ultrabroad parametric fluorescence generated from a quasi-phase-matched (QPM) device whose poling period is chirped. In the Harris\' s original proposal, it is assumed that the photons are collinearly generated and then spatially separated by frequency filtering. Here, we alternatively propose using noncollinearly generated SPDC. In our numerical calculation, to achieve 1.2 cycle temporal correlation for a 532 nm pump laser, only 10% -chirped device is sufficient when noncollinear condition is applied, while a largely chirped (50%) device is required in collinear condition. We also experimentally demonstrate an octave-spanning (790-1610 nm) noncollinear parametric fluorescence from a 10% chirped MgSLT crystal using both a superconducting nanowire single-photon detector and photomultiplier tube as photon detectors. The observed SPDC bandwidth is 194 THz, which is the largest width achieved to date for a chirped QPM device. From this experimental result, our numerical analysis predicts that the bi-photon can be compressed to 1.2 cycles with appropriate phase compensation.