Fig. 1. Timeline for the development of NOSP

Fig. 2. Physical processes, spectra, and electromagnetic wave spectrum of typical parametric process. (a) Second-order nonlinear effect; (b) three-order nonlinear effect; (c) electromagnetic spectrum distribution of light waves involved in FWM and second-order nonlinear processes

Fig. 3. Refractive index and nonlinear refractive index of various third-order nonlinear integrated material platforms

Fig. 4. Waveguides suitable for enhancing nonlinear of all kinds of material platforms. (a) Schematic of periodic polarization of lithium niobate (LN) waveguide and SEM image of PPLN waveguide^[33]; (b) microscope images of the spiral low-loss multimode silicon waveguide^[76]; (c) schematic of PIN ridge waveguide^[79]; (d) SEM image of ultrahigh nonlinear AlGaAs waveguide^[78];(e) microscope image of the ultra-low loss silicon nitride waveguide microscopy and corresponding chip photo^[71]

Fig. 5. Special waveguides with enhanced nonlinearity. (a) SEM image of the silicon based slot waveguide filled with high-nonlinearity DDMEBT^[44]; (b) microscopic image of an microring resonator patterned with graphene oxide^[81]; (c) SEM image of the BIC waveguide for second harmonic generation^[83]

Fig. 6. Microring resonator schemes for enhancing nonlinear. (a) Schematic of AlGaAs microring resonator^[31]; (b) schematic of cascaded microring with slow light propagation effect^[84]; (c) microscopic image of microring with PT symmetry^[86]

Fig. 7. Comparison among TF-PPLN waveguide, Kerr waveguide, microring resonator, and PT-symmetric coupling microring resonator

Fig. 8. Thin film LN electro-optic (EO) frequency comb^[62]. (a) Electron microscopic image of LN microring for producing electrooptic combs; (b) EO comb generation principle; (c) spectrum of the EO comb

Fig. 9. Wavelength convertors. (a) Output spectrum of TN-PPLN wavelength convertor^[58]; (b) output spectrum of the ultra-low loss Si₃N₄ wavelength convertor^[71]; (c) micrograph of wavelength convertor based on cascaded EO effect^[126]

Fig. 10. Experimental setup of a photonic integrated all-optical phase regenerator combining the frequency comb technology^[95]

Fig. 11. Reconfigurable canonical logic units (CLUs) ^[162]. (a) Schematic of reconfigurable CLUs; (b) frequency distribution of reconfigurable CLUs multicasting

Fig. 12. Frequency distribution of different calculation results based on FWM process^[97]

Fig. 13. Ultrabright single photon sources. (a) TF-PPLN microring resonator photon source^[64]; (b) ultra-bright photon source based on AlGaAs microring^[175]

Fig. 14. Schematic diagram of all-optical signal processing chip