Ultrafast low-pump fluence all-optical modulation based on graphene-metal hybrid metasurfaces

Abstract

Graphene is an attractive material for all-optical modulation because of its ultrafast optical response and broad spectral coverage. However, all-optical graphene modulators reported so far require high pump fluence due to the ultrashort photo-carrier lifetime and limited absorption in graphene. We present modulator designs based on graphene-metal hybrid plasmonic metasurfaces with highly enhanced light-graphene interaction in the nanoscale hot spots at pump and probe (signal) wavelengths. Based on this design concept, we have demonstrated high-speed all-optical modulators at near and mid-infrared wavelengths (1.56 μm and above 6 μm) with significantly reduced pump fluence (1–2 orders of magnitude) and enhanced optical modulation. Ultrafast near-infrared pump-probe measurement results suggest that the modulators’ response times are ultimately determined by graphene’s ultrafast photocarrier relaxation times on the picosecond scale. The proposed designs hold the promise to address the challenges in the realization of ultrafast all-optical modulators for mid-and far-infrared wavelengths.

Flexible CsPbBr3 microwire photodetector with a performance enhanced by covering it with an Ag nanolayer

“…[45][46][47] Metal structures have been employed to optimize the performance of optoelectronics and optical devices. [48][49][50][51][52][53][54][55][56] Among those, Ag is widely used to realize performance-enhanced photodetection for the work function of Ag is close to that of most perovskites. Thus, it is meaningful to carry out an investigation about performance-enhanced perovskite photodetectors in combination with Ag.…”

Recent Advances in Tunable Metasurfaces: Materials, Design, and Applications

“…48,223 A dielectric metasurface consisting of amorphous Si (a-Si) nanopillars embedded in LCs with two vertical ITO electrodes was proposed for switchable display. Its transmission modulation depth was ∼53% in the visible spectrum under an applied voltage of 20 V. 57 Using a low loss dielectric of TiO 2 nanopillars instead of a-Si, the modulation depth was increased to 65% under an applied voltage of only 5 V. 224 Switchable beam steering was achieved by a combination of the LCs and TiO 2 metasurfaces, yielding a tunable steering angle of up to 11°at an applied voltage of 8 V with a transmission efficiency of 35%, as shown in Figure 5d. 10 Despite this achievement, a higher transmission efficiency of up to 60% with an even lower bias was realized by replacing ITO electrodes with conductive polymers strips.…”

“…In addition, low loss dielectric metasurface and highly transparent electrodes have been strategically developed to alleviate the loss associated with metals for the LCs molecular alignment. , A dielectric metasurface consisting of amorphous Si (a-Si) nanopillars embedded in LCs with two vertical ITO electrodes was proposed for switchable display. Its transmission modulation depth was ∼53% in the visible spectrum under an applied voltage of 20 V . Using a low loss dielectric of TiO 2 nanopillars instead of a-Si, the modulation depth was increased to 65% under an applied voltage of only 5 V .…”

“…Nevertheless, electronic structures of 2D materials, such as graphene ,, and black phosphorus, enable their spectral bandwidth across the visible, NIR, MIR, and THz regimes under both optical and electrical stimuli where a considerable modulation depth is also achievable, as indicated by the blue stars plotted in Figure b. Some exciting properties such as long-lived plasmons/excitons and tunable excitonic resonant excitations could naturally form in graphene , /2D layered perovskite materials and transition-metal dichalcogenide (TMDC). They provide opportunities for realizing active ultrathin metasurfaces under optical, electrical, chemical, mechanical, and magnetic stimuli by the integration of 2D materials …”

Metasurface for highly-efficient on-chip classical and quantum all-optical modulation

“…Now, writing in this issue of Light: Science & Applications , Yu Yao and his colleagues at the Arizona State University in USA combined the metallic metasurface with graphene to implement efficient and fast all-optical modulators above 6 μm 8 . It should be pointed out that although graphene could absorb mid-infrared light due to its gapless band structure, the atomic thickness of graphene results in the low light absorption within graphene and causes high pump power 9 .…”