Abstract Diamond has attracted great interest as an appealing material for various applications ranging from classical to quantum optics. To date, Raman lasers, single photon sources, quantum sensing and quantum communication have been demonstrated with integrated diamond devices. However, studies of the nonlinear optical properties of diamond have been limited, especially at the nanoscale. Here, a metasurface consisting of plasmonic nanogap cavities is used to enhance both χ (2) and χ (3) nonlinear optical processes in a wedge-shaped diamond slab with a thickness down to 12 nm. Multiple nonlinear processes were enhanced simultaneously due to the relaxation of phase-matching conditions in subwavelength plasmonic structures by matching two excitation wavelengths with the fundamental and second-order modes of the nanogap cavities. Specifically, third-harmonic generation (THG) and second-harmonic generation (SHG) are both enhanced 1.6 × 10 7 -fold, while four-wave mixing is enhanced 3.0 × 10 5 -fold compared to diamond without the metasurface. Even though diamond lacks a bulk χ (2) due to centrosymmetry, the observed SHG arises from the surface χ (2) of the diamond slab and is enhanced by the metasurface elements. The efficient, deeply subwavelength diamond frequency converter demonstrated in this work suggests an approach for conversion of color center emission to telecom wavelengths directly in diamond.
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Nonlinear Strong Coupling by Second‐Harmonic Generation Enhancement in Plasmonic Nanopatch Antennas
Enhanced electromagnetic fields within plasmonic nanocavity mode volumes enable multiple significant effects that lead to applications in both the linear and nonlinear optical regimes. In this work, enhanced second‐harmonic generation (SHG) is demonstrated from individual plasmonic nanopatch antennas (NPAs) which are formed by separating silver nanocubes from a smooth gold film using a sub‐10 nm zinc oxide spacer layer. When the NPAs are excited at their fundamental plasmon frequency, a 104‐fold increase in the intensity of the SHG wave is observed. Moreover, by integrating quantum emitters that have an absorption energy at the fundamental frequency, a second‐order nonlinear exciton–polariton strong coupling response is observed with a Rabi splitting energy of 19 meV. The nonlinear frequency conversion using NPAs thus provides an excellent platform for nonlinear control of the light−matter interactions in both weak and strong coupling regimes which will have a great potential for applications in optical engineering and information processing.
more » « less- PAR ID:
- 10444530
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Optical Materials
- Volume:
- 10
- Issue:
- 16
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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si , can provide such closed form solutions for crystals with arbitrary symmetries, orientations, and anisotropic properties at asingle interface. However, optical components are often in the form of slabs, thin films on substrates, and multilayer heterostructures with multiple reflections of both the fundamental and up to ten different SHG waves at each interface, adding significant complexity. Many approximations have therefore been employed in the existing analytical approaches, such as slowly varying approximation, weak reflection of the nonlinear polarization, transparent medium, high crystallographic symmetry, Kleinman symmetry, easy crystal orientation along a high-symmetry direction, phase matching conditions and negligible interference among nonlinear waves, which may lead to large errors in the reported material properties. To avoid these approximations, we have developed an open-source package named Second Harmonic Analysis of Anisotropic Rotational Polarimetry in Multilayers (♯SHAARP.ml ). The reliability and accuracy are established by experimentally benchmarking with both the SHG polarimetry and Maker fringes using standard and commonly used nonlinear optical materials as well as twisted 2-dimensional heterostructures. -
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