Direct LED writing of submicron resist patterns : towards the fabrication of individually-addressable InGaN submicron stripe-shaped LED arrays

Submicron stripe-shaped InGaN light-emitting diode (LED) arrays with individually addressable capabilities are demonstrated. The critical submicronstripe metallic electrodes, which define the emission pattern, are formed by direct LED writing in a mask-free manner. The individually addressable submicron-stripe LEDs show excellent performance in terms of their electrical characteristics (with typical turn-on voltage of 3 V, operational stability and power output up to 28 μW at 3 mA). Unlike conventional broad-sized LEDs, the efficiency droop of the submicron-stripe LED is significantly suppressed-in fact, there is no efficiency droop for current densities up to 100 A/cm2. Furthermore, the submicron-stripe LED shows a lower temperature-dependent shift of the emission wavelength. The lateral emission width is increased with increasing injection current, resulting in a wider lateral emission size than the metallic submicron-stripe electrode. The underlying physics of these phenomena are analysed. Such submicron-stripe LED arrays open up promising applications in nanophotonics and bio-sensing

High accuracy transfer printing of single-mode membrane silicon photonic devices

A transfer printing (TP) method is presented for the micro-assembly of integrated photonic devices from suspended membrane components. Ultra thin membranes with thickness of 150nm are directly printed without the use of mechanical support and adhesion layers. By using a correlation alignment scheme vertical integration of single-mode silicon waveguides is achieved with an average placement accuracy of 100±70nm. Silicon (Si) μ-ring resonators are also fabricated and show controllable optical coupling by varying the lateral absolute position to an underlying Si bus waveguide

Transfer Printing of Photonic Nanostructures to Silicon Integrated Circuits

Optical systems require the integration of technologies fabricated on different materials. We use a transfer printing technique to integrate pre-processed III-V, polymer and silicon membrane devices onto passive optical circuits with nano-metric positional accuracy

CdSxSe1-x/ZnS semiconductor nanocrystal laser with sub 10kW/cm² threshold and 40nJ emission output at 600 nm

A colloidal quantum dot laser emitting at 600 nm with a sub 10kW/cm2 threshold at 5ns pulse pumping is reported. The device has a second order distributed feedback cavity for vertical emission and incorporates a bilayer planar waveguide structure based on a film of yellow-orange alloyed-core/shell CdSxSe1-x/ZnS quantum dots over-coated with polyvinyl alcohol. A study of the amplified spontaneous regime indicates that the quantum dot gain region behaves like a quasi-three level system and that the bilayer structure design increases the modal gain compared to a single layer of quantum dots. An output of 40nJ per pulse is measured for a total pump-to-signal efficiency above threshold of 3%

Gb/s visible light communications with colloidal quantum dot color converters

This paper reports the utilization of colloidal semiconductor quantum dots as color converters for Gb/s visible light communications. We briefly review the design and properties of colloidal quantum dots and discuss them in the context of fast color conversion of InGaN light sources, in particular in view of the effects of self-absorption. This is followed by a description of a CQD/polymer composite format of color converters. We show samples of such color-converting composite emitting at green, yellow/orange and red wavelengths, and combine these with a blueemitting microsize LED to form hybrid sources for wireless visible light communication links. In this way data rates up to 1 Gb/s over distances of a few tens of centimeters have been demonstrated. Finally, we broaden the discussion by considering the possibility for wavelength division multiplexing as well as the use of alternative colloidal semiconductor nanocrystals

Organic semiconductor laser biosensor : design and performance discussion

Organic distributed feedback lasers can detect nanoscale materials and are therefore an attractive sens- ing platform for biological and medical applications. In this paper, we present a model for optimizing such laser sensors and discuss the advantages of using an organic semiconductor as the laser material in comparison to dyes in a matrix. The structure of the sensor and its operation principle are described. Bulk and surface sensing exper- imental data using oligofluorene truxene macromolecules and a conjugated polymer for the gain region is shown to correspond to modeled values and is used to assess the biosensing attributes of the sensor. A comparison between organic semiconductor and dye-doped laser sensitivity is made and analyzed theoretically. Finally, experimental and theoretical specific biosensing data is provided and methods for improving sensitivity are discussed

Micro-LED waveguide for fluorescence applications

A micro-LED-coupled multimode slab waveguide is reported for fluorescence sensing. The device consists of a 1-dimensional micro-LED array coupled to a sub-mm polymeric slab for evanescent excitation of fluorescent analytes present on the surface. Proof-principle detection of semiconductor nanocrystals down to 0.2 pM/cm2 is demonstrated

Transfer printing of semiconductor nanowire lasers

The authors review their work on the accurate positioning of semiconductor nanowire lasers by means of nanoscale Transfer Printing (nano-TP). Using this hybrid nanofabrication technique, indium phosphide (InP) NWs are successfully integrated at selected locations onto heterogeneous surfaces with high positioning accuracy. Moreover, we show that NW lasers can also be organised to form bespoke spatial patterns, including 1- or 2-Dimensional arrays, or complex configurations with defined number of NWs and controlled separation between them. Besides, our nano-TP technique also permits the integration of NWs with different dimensions in a single system. Notably, the nano-TP fabrication protocols do not affect the optical or structural properties of the NWs and they retain their room-temperature lasing emission after their positioning onto all investigated receiving surfaces. This developed nano-TP technique offers therefore new exciting prospects for the fabrication of hybrid bespoke nanophotonic systems using NW lasers as building blocks

Novel nanoscale transfer printing technique for precise positioning of nanowire lasers

Semiconductor nanowires, with lasing emission at room temperature, can be transferred in a controlled way to specific locations on diverse substrates and organized into bespoke spatial patterns

All-optical tuning of a diamond micro-disk resonator on silicon

High-quality integrated diamond photonic devices have previously been demonstrated in applications from non-linear photonics to on-chip quantum optics. However, the small sample sizes of single crystal material available, and the difficulty in tuning its optical properties, are barriers to the scaling of these technologies. Both of these issues can be addressed by integrating micrometer-scale diamond devices onto host photonic integrated circuits using a highly accurate micro-assembly method. In this work a diamond micro-disk resonator is integrated with a standard single-mode silicon-on-insulator waveguide, exhibiting an average loade