Experimental Demonstration of Dark‐State Metasurface Laser with Controllable Radiative Coupling

Abstract

Lasing at the nanoscale using plasmonic nanoparticles offers the prospect of strong field concentration, hence strong light−matter interactions, low lasing thresholds, and ultrafast operation. However plasmonic nanoparticles suffer from high dissipative and radiative losses, the latter being rigidly tied to the shape of the nanoparticles and symmetry of their localized plasmon resonant modes. To overcome this limitation, recent theoretical work proposes using direct lasing into dark surface states to construct lasers that conceptually allow for independent implementation of the lasing state and its coherent radiation output. Here, lasing in dark resonant states of a metasurface laser and controllable coherent outcoupling of radiation with the aid of a tightly coupled, weakly radiative metasurface are demonstrated experimentally. The laser is implemented using a thin, low‐loss dielectric film supporting surface mode‐like dark dielectric bound states and the coupling metasurface is composed of small non‐resonant scatterers that controllably but weakly perturb the dark mode and turn it partially bright. Distinct far‐field signatures that can be observed experimentally for both dark and bright lasing are identified and demonstrated. The scalability of this design, here implemented for lasing in the near‐infrared, enables large‐aperture ultra‐thin coherent light sources with controllable emission from the infrared to the visible.

Low‐Threshold Multiwavelength Plasmonic Nanolasing in an “H”‐Shape Cavity

“…The unambiguous evidence for lasing is also provided by the emission images shown in the insets of Figure 5c, where the interference fringes are found for the device operated in either the single‐ or dual‐wavelength modes. In addition, we also find that the Ag nanowire can function as a scatter to out‐couple the power stored in the dark mode to the free‐space, [ 42,43 ] as illustrated in the insets of Figure 5c, where the brightened dots are found at the position of Ag nanowires. It is also noted that for the dual‐wavelength device the thresholds of lasing emissions at 882 nm (25 µJ cm −2 per pulse) and 945 nm (17.6 µJ cm −2 per pulse) are higher than their respective monochromatic counterparts as shown in Figure 5b (see detail in Figure S9, Supporting Information ).…”

“…Our design can provide an elegant and versatile on-chip lasing platform to readily integrate with other gain materials such as quantum dots, semiconductor nanowires and2D materials. Moreover, patterning our device into an array may deliver the coherence light source with controllable radiation, [42,43] which may open up exciting prospects for ultracompact photonic integrated circuits and high-throughput biochemical sensing.…”

Large and active circular dichroism in a photosensitive silicon based metasurface

“…The propagating direction of incident light θ represents the angle of k off z axis and φ represents the angle off x axis. The refractive index of Al 2 O 3 spacer is 1.56 [35]. We utilize a lossy-metal model for gold with σ gold = 7 × 10 6 S m −1 [25].…”