Highly mode-selective quantum frequency conversion in a slab waveguide

Abstract

We analyze sum-frequency generation (SFG) in a χ (2) slab waveguide with the goal of achieving a single spatial-mode operation. We first develop Green's function formalism for the SFG equations and then perform singular-value decomposition (SVD) of the Green's function. By adjusting the spatial profile of the pump, we manipulate the SVD spectrum to maximize the up-conversion of one signal mode while minimizing the up-conversion of all others, which opens a possibility of realizing a spatial-mode-selective quantum frequency converter for future optical communications.

Devices for quantum communication over mode-division-multiplexing systems

“…First, based on our previous studies of the nonlinear mode interactions in spatially-multimode optical parametric amplifiers in free space [6][7][8][9] and multimode waveguides [10], we have developed a scheme for a spatial-mode demultiplexer based on sum-frequency generation (SFG) in a two-mode PPLN waveguide [11,12]. We have experimentally demonstrated such a demultiplexer, in which, by adjusting the spatial profile of a 1560-nm pump wave, we could selectively upconvert either mode TM00, or mode TM01, or any superposition of these two modes of a 1540-nm signal to TM01 mode at 775 nm, for both classical [13,14] and single-photon-level [14,15] signals.…”

“…In the two-mode PPLN waveguide, the same SFG process mentioned in Section 2, if operated in reverse, can be used for generation of quantum states entangled in spatial domain [11][12][13][14][15]: annihilation of a 775 nm pump photon creates a signal photon at 1540 nm and an idler photon at 1560 nm, whose individual spatial states in (TM00, TM01) mode basis are completely uncertain. However, if one of these photons is found to be in a particular superposition of TM00, TM01 modes, then the other will be in the orthogonal superposition.…”