This study presents the first real-space imaging of propagating and localized graphene plasmons using near-field scattering microscopy with infrared excitation light. The researchers demonstrate the ability to electrically tune graphene plasmons by gating the graphene, enabling the creation of tunable resonant plasmonic cavities with extremely small mode volumes. The plasmon wavelength is found to be significantly shorter than the free-space excitation wavelength, over 40 times smaller, due to the unique two-dimensional nature and conductance properties of graphene. This strong optical field confinement allows for the development of novel nano-optoelectronic devices and functionalities, such as tunable metamaterials, nanoscale optical processing, and enhanced light-matter interactions for quantum devices and biosensing applications. The study shows that graphene plasmons can be efficiently launched and detected using a scanning near-field optical microscope (s-SNOM). The researchers observe interference fringes in the near-field images, which are interpreted as the result of plasmon reflections at the edges of the graphene ribbons. The plasmon wavelength is experimentally determined to be 260 nm, which is in good agreement with theoretical predictions. The results demonstrate the potential of graphene plasmonics for active nanoscale photonic devices, enabling the design and miniaturization of photonic components. The study also shows that the plasmon wavelength can be actively controlled by electrical gating, allowing for the switching on and off of plasmon modes. This capability is crucial for the development of graphene-based optical transistors and other active photonic devices. The researchers demonstrate that the plasmon wavelength can be tuned over a wide range by changing the excitation wavelength, which is influenced by the dielectric constant of the substrate. The results highlight the importance of understanding the interaction between plasmons and the surrounding medium, as well as the role of substrate properties in determining plasmon behavior. The study provides a comprehensive understanding of the physical mechanisms underlying the observation of plasmonic modes and interference fringes in graphene. The researchers use a numerical model to calculate the field backscattered by the tip, which helps in interpreting the experimental results. The results show that the local density of optical states (LDOS) is closely related to the plasmon wavelength and the substrate properties. The LDOS maps reveal interference fringes and localized modes near the tip of the ribbon, which are attributed to plasmon reflections at the graphene edges. The study also demonstrates the potential of graphene plasmonics for applications in optical and optoelectronic telecommunications and information processing. The results show that graphene plasmons can be resonantly excited by light in graphene nanocavities, enabling strong enhancement of light absorption in graphene and a new basis for infrared detectors and light-harvesting devices. The findings provide a foundation for the development of new optical technologies based on graphene plasmonics.This study presents the first real-space imaging of propagating and localized graphene plasmons using near-field scattering microscopy with infrared excitation light. The researchers demonstrate the ability to electrically tune graphene plasmons by gating the graphene, enabling the creation of tunable resonant plasmonic cavities with extremely small mode volumes. The plasmon wavelength is found to be significantly shorter than the free-space excitation wavelength, over 40 times smaller, due to the unique two-dimensional nature and conductance properties of graphene. This strong optical field confinement allows for the development of novel nano-optoelectronic devices and functionalities, such as tunable metamaterials, nanoscale optical processing, and enhanced light-matter interactions for quantum devices and biosensing applications. The study shows that graphene plasmons can be efficiently launched and detected using a scanning near-field optical microscope (s-SNOM). The researchers observe interference fringes in the near-field images, which are interpreted as the result of plasmon reflections at the edges of the graphene ribbons. The plasmon wavelength is experimentally determined to be 260 nm, which is in good agreement with theoretical predictions. The results demonstrate the potential of graphene plasmonics for active nanoscale photonic devices, enabling the design and miniaturization of photonic components. The study also shows that the plasmon wavelength can be actively controlled by electrical gating, allowing for the switching on and off of plasmon modes. This capability is crucial for the development of graphene-based optical transistors and other active photonic devices. The researchers demonstrate that the plasmon wavelength can be tuned over a wide range by changing the excitation wavelength, which is influenced by the dielectric constant of the substrate. The results highlight the importance of understanding the interaction between plasmons and the surrounding medium, as well as the role of substrate properties in determining plasmon behavior. The study provides a comprehensive understanding of the physical mechanisms underlying the observation of plasmonic modes and interference fringes in graphene. The researchers use a numerical model to calculate the field backscattered by the tip, which helps in interpreting the experimental results. The results show that the local density of optical states (LDOS) is closely related to the plasmon wavelength and the substrate properties. The LDOS maps reveal interference fringes and localized modes near the tip of the ribbon, which are attributed to plasmon reflections at the graphene edges. The study also demonstrates the potential of graphene plasmonics for applications in optical and optoelectronic telecommunications and information processing. The results show that graphene plasmons can be resonantly excited by light in graphene nanocavities, enabling strong enhancement of light absorption in graphene and a new basis for infrared detectors and light-harvesting devices. The findings provide a foundation for the development of new optical technologies based on graphene plasmonics.