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We demonstrate experimentally close to total absorption in monolayer graphene based on critical coupling with guided resonances in transfer printed photonic crystal Fano resonance filters at near infrared. Measured peak absorptions of 35% and 85% were obtained from cavity coupled monolayer graphene for the structures without and with back reflectors, respectively. These measured values agree very well with the theoretical values predicted with the coupled mode theory based critical coupling design. Such strong light-matter interactions can lead to extremely compact and high performance photonic devices based on large area monolayer graphene and other two-dimensional materials. V

In this work, flexible phototransistors with a back gate configuration based on transferrable single‐crystalline Si nanomembrane (Si NM) have been demonstrated. Having the Si NM as the top layer enables full exposure of the active region to an incident light and thus allows for effective light sensing. Flexible phototransistors are performed in two operation modes: 1) the high light detection mode that exhibits a photo‐to‐dark current ratio of 105 at voltage bias of VGS < 0.5 V, and VDS = 50 mV and 2) the high responsivity mode that shows a maximum responsivity of 52 A W−1 under blue illumination at voltage bias of VGS = 1 V, and VDS = 3 V. Due to the good mechanical flexibility of Si NMs with the assistance of a polymer layer to enhance light absorption, the device exhibits stable responsivity with less than 5% of variation under bending at small radii of curvatures (up to 15 mm). Overall, such flexible phototransistors with the capabilities of high sensitivity light detection and stable performance under the bending conditions offer great promises for high‐performance flexible optical sensor applications, with easy integration for multifunctional applications.

An aqueous solution-based doping strategy was developed for controlled doping impurity atoms into a ZnO nanowire (NW) lattice. Through this approach, antimony-doped ZnO NWs were successfully synthesized in an aqueous solution containing zinc nitrate and hexamethylenetetramine with antimony acetate as the dopant source. By introducing glycolate ions into the solution, a soluble antimony precursor (antimony glycolate) was formed and a good NW morphology with a controlled antimony doping concentration was successfully achieved. A doping concentration study suggested an antimony glycolate absorption doping mechanism. By fabricating and characterizing NW-based field effect transistors (FETs), stable p-type conductivity was observed. A field effect mobility of 1.2 cm(2) V(-1) s(-1) and a carrier concentration of 6 × 10(17) cm(-3) were achieved. Electrostatic force microscopy (EFM) characterization on doped and undoped ZnO NWs further illustrated the shift of the metal-semiconductor barrier due to Sb doping. This work provided an effective large-scale synthesis strategy for doping ZnO NWs in aqueous solution.

The authors design a photonic crystal Mach-Zehnder interferometer by utilizing the self-collimated beams and the bending and splitting mechanisms of line defects. Using this interferometer, they investigate the phase shift of the reflected and transmitted self-collimated beams over the line defects. In addition, on the basis of the intensity-asymmetric unidirectional-output design, they demonstrate that such interferometers can function as an intensity detector or an ultrafast optical switch when the material of photonic crystal is nonlinear.

Crystalline semiconductor nanomembranes (NMs), which are transferable, stackable, bondable and manufacturable, offer unprecedented opportunities for unique and novel device applications. We report and review here nanophotonic devices based on stacked semiconductor NMs that were built on Si, glass and flexible PET substrates. Photonic-crystal Fano resonance based surface-normal optical filters and broadband reflectors have been demonstrated with unique angle and polarization properties. Such a low temperature NM stacking process can lead to a paradigm shift on silicon photonic integration and inorganic flexible photonics.

Deep ultraviolet (UV) light-emitting diodes (LEDs) at a wavelength of 226 nm based on AlGaN/ AlN multiple quantum wells using p-type Si as both the hole supplier and the reflective layer are demonstrated. In addition to the description of the hole transport mechanism that allows hole injection from p-type Si into the wide bandgap device, the details of the LED structure which take advantage of the p-type Si layer as a reflective layer to enhance light extraction efficiency (LEE) are elaborated. Fabricated LEDs were characterized both electrically and optically. Owing to the efficient hole injection and enhanced LEE using the p-type Si nanomembranes (NMs), an optical output power of 225 lW was observed at 20 mA continuous current operation (equivalent current density of 15 A/cm 2) without external thermal management. The corresponding external quantum efficiency is 0.2%, higher than any UV LEDs with emission wavelength below 230 nm in the continuous current drive mode. The study demonstrates that adopting p-type Si NMs as both the hole injector and the reflective mirror can enable high-performance UV LEDs with emission wavelengths, output power levels, and efficiencies that were previously inaccessible using conventional p-in structures.