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

Abstract

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.

Dispersion cancellation in high-resolution two-photon interference

“…In these schemes, the photon flux of the light source can be much higher compared to QOCT, but the realized bandwidth of the correlated light source seems much broader in QOCT [27]. Research using these alternative approaches will have beneficial positive mutual feedback for further investigations.…”

Orthogonal quasi-phase-matched superlattice for generation of hyperentangled photons

“…This offers a hyperentangled version of the original proposal by Harris 43 to generate temporally entangled photon pairs correlated to less than one cycle of light. A superlattice chirp-and-compress design will generate noncollinear ultra-broadband biphotons with no need for large chirping 44, 45 and no need for self-compensation to eliminate temporal distinguishability, and hence no need for an additional time-delay element.…”

“…Each of the two orthogonal sets of nonlinear layers acts like spacers that engineer the group-delay 38, 39 of the emission of the other set. QPM is woven into each of the orthogonally polarized emissions, and as in other SPDC processes it enables access to the highest nonlinear coefficient, opens the possibility for tunability with highly reduced bandwidth over a wide spectral range 40 , and offers a unique capability of tailoring the spatiotemporal properties of the entangled photons 41–45 . In comparison with the CC source and the DN source, this superlattice (SL) structure is shown to emit SPDC biphotons with nearly perfect spatial and temporal indistinguishability over ultra-wide spatial and spectral windows, even if it uses a focused and low-coherence-time beam to pump a long structure in a noncollinear interaction geometry, and without the need for compensating elements.

Figure 1( a) Schematic of the superlattice structure showing the two interleaved sets of nonlinear layers with orthogonal optic axes and orthogonal directions of poling, as indicated by the g H ( z ) and g V ( z ) functions.

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Thermal management for high-power wavelength conversion

“…The temperature increase is characterized by phase-matched calorimetry (PMC) [1,2], which analyzes the performance of the heat removal in the module. Combination of Mg:SLT and a metal heat spreader realizes stable output in green, which is also useful in green-pumped optical parametric generation for obtaining stable quantum-entangled photon pairs [3,4].…”