A microwave ultra-broadband polarization-independent metamaterial absorber is demonstrated. It is composed of a periodic array of metal-dielectric multilayered quadrangular frustum pyramids. These pyramids possess resonant absorption modes at multi-frequencies, of which the overlapping leads to the total absorption of the incident wave over an ultra-wide spectral band. The experimental absorption at normal incidence is above 90% in the frequency range of 7.8–14.7 GHz, and the absorption is kept large when the incident angle is smaller than 60°. The experimental results agree well with the numerical simulation.

With an ultimately thin active region, monolayer transition metal dichalcogenide lasers have the potential of realizing ultralow lasing threshold and power consumption. The flexibility also enables integration possibilities on unconventional substrates. Here, we report a photonic crystal surface emitting laser using monolayer tungsten disulfide as the gain medium. The cavity design utilizes a heterostructure in the photonic crystal lattice to provide lateral confinement for a high quality factor with a compact active region. Room-temperature continuous wave lasing is realized after integrating monolayer tungsten disulfide flakes onto the silicon nitride photonic crystal on a quartz substrate. Highly directional, near surface-normal emission has also been experimentally demonstrated. The work reported here demonstrates that a large-area single-mode directional laser can be realized from a monolayer gain medium, which is critical for laser scaling for on-chip integration in data and sensing applications.

The design, fabrication, and characterization of a compact photonic crystal nanobeam drop filter based on the tunneling effect of the degenerate modes are presented. The degeneracy was achieved by tuning the coupling distance between the nanobeam and input/output waveguides. The tunneling effect of degenerate resonances with different symmetries has been verified experimentally. Channel drop filters with an extinction ratio larger than 10 dB and a quality factor of $\sim 5000$ have been experimentally demonstrated.

We report here design and experimental demonstration of heterostructure photonic crystal cavities resonating near the Γ point with simultaneous strong lateral confinement and highly directional vertical radiation patterns. The lateral confinement is provided by a mode gap originating from a gradual modulation of the hole radii. High quality factor resonance is realized with a low index contrast between silicon nitride and quartz. The near surface-normal directional emission is preserved when the size of the core region is scaled down. The influence of the cavity size parameters on the resonant modes is also investigated theoretically and experimentally.