Light-matter interaction in a microcavity-controlled graphene transistor (1112.1380v2)

Abstract: Graphene has extraordinary electronic and optical properties and holds great promise for applications in photonics and optoelectronics. Demonstrations including high-speed photodetectors, optical modulators, plasmonic devices, and ultrafast lasers have now been reported. More advanced device concepts would involve photonic elements such as cavities to control light-matter interaction in graphene. Here we report the first monolithic integration of a graphene transistor and a planar, optical microcavity. We find that the microcavity-induced optical confinement controls the efficiency and spectral selection of photocurrent generation in the integrated graphene device. A twenty-fold enhancement of photocurrent is demonstrated. The optical cavity also determines the spectral properties of the electrically excited thermal radiation of graphene. Most interestingly, we find that the cavity confinement modifies the electrical transport characteristics of the integrated graphene transistor. Our experimental approach opens up a route towards cavity-quantum electrodynamics on the nanometre scale with graphene as a current-carrying intra-cavity medium of atomic thickness.

• The paper demonstrates a twenty-fold photocurrent enhancement by tuning the laser wavelength to the microcavity resonance.
• The paper presents a novel approach to achieve narrow-band thermal radiation control via electrical bias in a microcavity-integrated graphene device.
• The paper reveals that optical confinement in the microcavity alters graphene's electrical transport, linking increased self-heating with modified emission characteristics.

Overview of Light-Matter Interaction in a Microcavity-Controlled Graphene Transistor

The paper presents a paper on the monolithic integration of a graphene transistor with a planar optical microcavity, exploring both theoretical and practical implications of enhanced light-matter interactions at the nanoscale using graphene as the current-carrying medium. Graphene's distinct electronic and optical properties, alongside its monolayer thickness, make it ideally suited for inclusion in a planar λ/2 microcavity, engaging photon confinement to manipulate photocurrent generation and electrically excited thermal radiation spectrally.

Key Findings

1. Photocurrent Enhancement: The integration utilizes a novel microcavity manufacturing process, where graphene is embedded between dielectric layers and metallic mirrors to control light absorption. A notable enhancement, reaching a twenty-fold increase in photocurrent amplitude, was achieved by adjusting the laser wavelength to match the cavity resonance. This spectral selectivity was contrastively non-existent in a non-confined graphene transistor.
2. Thermal Radiation Control: The microcavity design allows for narrow-band thermal light emission controlled by electrical bias. Compared to non-confined setups, the controlled setup exhibits a single spectral peak and an inhibited emission of spontaneous long-wavelength radiation, notable as the first demonstration of a current-driven thermal light source under cavity control.
3. Electrical Transport Modification: Optically confining graphene in a microcavity modifies its electrical transport characteristics. A correlation was found between electrical power density and spectrally integrated thermal emission, indicating cavity-induced alterations such as lowered saturation currents potentially due to amplified self-heating effects.

Implications and Future Directions

The paper proposes that this paper opens possibilities for advanced graphene optoelectronic devices, including precisely tunable light detectors and emitters with potential applicability in fields such as nanoelectronics and cavity quantum electrodynamics (QED). Challenges remain in optimizing device performance, particularly concerning heating effects and the spectral range of emission, implying further exploration into terahertz regimes in subsequent research.

This work lays a foundation for leveraging the Purcell effect in true 2D materials and advancing cavity QED phenomena at the nanoscale, where graphene's unique properties provide an advantageous experimental platform for studying light-matter interactions.