Abstract
Nonlinear optical processes are an essential tool in modern optics, with a broad spectrum of applications, including signal processing, frequency conversion, spectroscopy and quantum optics. Ordinary parametric devices nevertheless still suffer from relatively low gains and wide spectral emission. Here we demonstrate a unique configuration for phase-matching multiple nonlinear processes in a monolithic 2D nonlinear photonic crystal, resulting in the coherent parametric emission of four signal and idler modes, featuring an exponential gain enhancement equal to the Golden Ratio. The results indicate a new route towards compact high-brightness and coherent sources for multi-photon generation, manipulation and entanglement, overcoming limitations of conventional parametric devices.
Highlights
OPG implies the spontaneous conversion of a photon from a high-energy pump laser into a pair of lower-energy photons, at frequencies ωa and ωb[17,18]
We use the QPM degrees of freedom of a 2D nonlinear photonic crystal to achieve OPG with four coupled output modes, accessing a super-resonant regime, which may have some analogy with coherent effects observed in a different context[33], whereby the parametric emission rates are enhanced as a result the coherent interplay of multiple parametric interactions
The waves in the nonlinear crystal interact according to the diagram of Fig. 1c, where a single pump excites three concurrent OPG processes, simultaneously generating three signal-idler mode pairs: (a0, b2), (a0, b0) and (a2, b0)
Summary
OPG implies the spontaneous conversion of a photon from a high-energy pump laser (at frequency ωp) into a pair of lower-energy photons, at frequencies ωa and ωb[17,18] This occurs in a medium possessing a quadratic optical nonlinearity and can lead to an exponential build-up of the signal and idler fields, provided that photon energy (ωp = ωa + ωb) phase-matching and momentum are preserved[25]. The waves in the nonlinear crystal interact according to the diagram of Fig. 1c, where a single pump excites three concurrent OPG processes, simultaneously generating three signal-idler mode pairs: (a0, b2), (a0, b0) and (a2, b0). This unique OPG configuration is underpinned by the following vectorial QPM conditions (Fig. 1f):.
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