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

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

MQW nanomembrane assemblies for visible light communications

We report color-conversion of InGaN LEDs and lasers using an AlInGaP multi-quantum-well nanomembrane. In particular, we demonstrate free-space OOK data transmission at 180 Mb/s from a laser diode blue-to-red converted by a heterogeneous nanomembrane/sapphire lens assembly

Optical gain in 1.3-μm electrically driven dilute nitride VCSOAs

We report the observation of room-temperature optical gain at 1.3 μm in electrically driven dilute nitride vertical cavity semiconductor optical amplifiers. The gain is calculated with respect to injected power for samples with and without a confinement aperture. At lower injected powers, a gain of almost 10 dB is observed in both samples. At injection powers over 5 nW, the gain is observed to decrease. For nearly all investigated power levels, the sample with confinement aperture gives slightly higher gain

Heterogeneous integration of gallium nitride light-emitting diodes on diamond and silica by transfer printing

We report the transfer printing of blue-emitting micron-scale light-emitting diodes (micro-LEDs) onto fused silica and diamond substrates without the use of intermediary adhesion layers. A consistent Van der Waals bond was achieved via liquid capillary action, despite curvature of the LED membranes following release from their native silicon growth substrates. The excellence of diamond as a heat-spreader allowed the printed membrane LEDs to achieve optical power output density of 10 W/cm2 when operated at a current density of 254 A/cm2. This high-currentdensity operation enabled optical data transmission from the LEDs at 400 Mbit/s

Flexible Glass Hybridized Colloidal Quantum Dots for Gb/s Visible Light Communications

Color converting films of colloidal quantum dots (CQDs) encapsulated with flexible glass are integrated with microsize GaN LEDs (μLEDs) in order to form optical sources for high-speed visible light communications (VLC). VLC is an emerging technology that uses white and/or colored light from LEDs to combine illumination and display functions with the transmission of data. The flexible glass/CQD format addresses the issue of limited modulation speed of typical phosphor-converted LEDs while enhancing the photostability of the color converters and facilitating their integration with the μLEDs. These structures are less than 70 μm in total thickness and are directly placed in contact with the polished sapphire substrate of 450-nm-emitting μLEDs. Blue-to-green, blue-to-orange and blue-to-red conversion with respective forward optical power conversion efficiencies of 13%, 12% and 5.5% are reported. In turn, free-space optical communications up to 1.4 Gb/s VLC is demonstrated. Results show that CQD-converted LEDs pave the way for practical digital lighting/displays with multi-Gb/s capability

Organic semiconductor laser platform for the detection of DNA by AgNP plasmonic enhancement

Organic semiconductor lasers are a sensitive biosensing platform that respond to specific biomolecule binding events. So far, such biosensors have utilized protein-based interactions for surface functionalization but a nucleic acid–based strategy would considerably widen their utility as a general biodiagnostic platform. This manuscript reports two important advances for DNA-based sensing using an organic semiconductor (OS) distributed feedback (DFB) laser. First, the immobilization of alkyne-tagged 12/18-mer oligodeoxyribonucleotide (ODN) probes by Cu-catalyzed azide alkyne cycloaddition (CuAAC) or “click-chemistry” onto an 80 nm thick OS laser film modified with an azide-presenting polyelectrolyte monolayer is presented. Second, sequence-selective binding to these immobilized probes with complementary ODN-functionalized silver nanoparticles, is detected. As binding occurs, the nanoparticles increase the optical losses of the laser mode through plasmonic scattering and absorption, and this causes a rise in the threshold pump energy required for laser action that is proportional to the analyte concentration. By monitoring this threshold, detection of the complementary ODN target down to 11.5 pM is achieved. This complementary binding on the laser surface is independently confirmed through surface-enhanced Raman spectroscopy (SERS)

Hybrid GaN microLED platform for fluorescence sensing

A hybrid GaN μLED platform developed for wearable illumination is adapted here for fluorescence sensing. Proof-of-principle detection of colloidal quantum dots down to 80 pM using a mobile phone camera is demonstrate

Design of a wearable LED based device for phototherapy applications

Phototherapy with UV or visible wavelengths is used to treat skin disorders such as psoriasis, eczema and vitiligo. Traditionally, phototherapy is carried out in a clinical environment and utilises large fluorescent lamps. These are now being replaced with more efficient light-emitting diodes (LEDs), a trend that is set to contin ue thanks to the progress of LED technology. LEDs are also facilitating the emergence of at-home devices to improve patient convenience and decrease demand on the healt hcare system [1]. Current at-home devices consist of rigid LED arrays, which limits their conformability and produces non-uniform light distribution over the treatment area, in turn limiting their efficacy and wearability [2]. As a solution to this problem, we are engineering a flexible light therapy device that combines LEDs and a sub-mm-thick polydimethylsiloxane (PDMS) light sheet in an edge-lit configuration

Wearable LED-based device for phototherapy applications

Phototherapy with UVA/B or visible wavelengths is used to treat skin disorders such as psoriasis, eczema and vitiligo. Traditionally, phototherapy is carried out in a clinical environment and utilises large fluorescent lamps. hese are now being replaced with more efficient light-emitting diodes (LEDs), a trend that is set to continue thanks to the progress of UV LED technology. LEDs are also facilitating the emergence of at-home devices to improve patient convenience and decrease de mand on the healthcare system [1] . Current at-home devices consist of inflexible LED arrays, which limits their conformability and produces non-uniform light distribution over the treatment area, in turn limiting their efficacy and wearability [2] . As a solution to this problem, we are engineering a flexible light therapy device that combines LEDs and a sub-mm-thick polydimethylsiloxane (PDMS) light sheet in an edge-lit configuration. PDMS has previously been shown as an effective flexible light guide [3 ]; its high transparency from 290 nm upwards and its biocompatibility make it an ideal substrate for a wearable phototherapy device. We will describe the effect of coupling LEDs to our PDMS sheet and discuss design strategies for efficient and uniform light extraction to the treatment area. The PDMS acts as a waveguide and the light diffused through the top surface of the sheet is measured as irradiance (μW/cm2). By adding scattering particles for light extraction a 10-fold enhancement in irradiance has been demonstrated. Utilising a UV LED (385 nm) at an optical power of 25 mW, this approach produces a uniform emission of 140 μW/cm2 over a treatment area of 225 mm2 ( fig. 1). Simulations have shown that the addition of diffractive patterns to the sheet also produces an increased uniform emission