Temperature stability of elastomeric colloidal quantum dot colour converter

The effect of temperature on the photoluminescent properties of an elastomeric colloidal quantum dot composite is presented. Results demonstrate that embedding colloidal quantum dots in a composite increases their thermal stability and that thermal degradation is an issue above 100°C independently of other photo-induced or oxygen-related phenomena

Multicolor laser oscillation in a single self-assembled colloidal quantum dot microsphere

Self-assembled microsphere lasers oscillating simultaneously at more than one wavelength in the visible are reported. The lasers consist of micron-scale supraparticles made of CdSxSe1-x/ ZnS quantum dots that emit between 585-605 nm and 625-655 nm

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%

Characteristics of GaInNAsSb VCSELs operating near 1.55µm

A detailed study of the high-power pulsed operation of C-band optically-pumped GaInNAsSb vertical cavity surface emitting lasers is reported. The devices employ a resonant periodic gain structure grown by molecular beam epitaxy on a GaAs substrate with a 31-pair GaAs/AlAs bottom distributed Bragg reflector and a 4-λ, GaAs-based resonant cavity containing 10 GaInNAsSb quantum wells distributed among the 7 antinodes of the electric field. A dual-pump-band SiO2/TiO2 dielectric top mirror allows efficient optical pumping via low reflectivities at 808nm and 1064nm while providing very high reflectivity at the 1.55μm target emission wavelength. The laser characteristics were evaluated using both a Q-switched Nd:YAG 1064nm pump and a 20W-peak 180ns-pulsed 850nm diode laser. The importance of the gain-cavity detuning was evident from time-dependent spectral measurements of laser material subjected to post-growth annealing at different temperatures between 725 and 775°C. The highest annealing temperature produces the largest blue shift of the gain peak relative to the cavity resonance, resulting in the best power transfer characteristics as well as reduced temperature sensitivity

Luminescence dynamics of CsPbBr3 quantum dot based color converters

The excitation density dependent characteristics of a green - emitting CsPbBr3 quantum dot color converter for GaN LEDs and lasers is reported. The bandwidth is found to increase with the excitation reaching up to 55 MHz at a 185 W/cm2 pump density

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

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

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

Oligofluorene truxene laser sensor : towards bacteria growth detection

Work toward the utilisation of an organic laser as a bacterial growth detector is presented here. The sensor used is an optically excited 2nd order DFB (distributed feedback laser) made of oligofluorene truxene. In the drive towards a practical bacterial growth detector, temperature stability and the optimum growth conditions of bacteria are challenges to be overcome. The resultant DFB laser exhibits a sensitivity of 9 nm/RIU

A wearable phototherapy device utilizing micro-LEDs

A conformable device for wearable phototherapy applications is presented. The device consists of a 1 mm thick elastomeric membrane edge-lit by specially fabricated micro-sized LEDs. Nanoparticle based scattering films are utilized to extract light and a uniform emission of 15 μW/cm2 is reported over an area of 2 cm2