LED excitation of an on-chip imaging flow cytometer for bead-based immunoassay

A green LED is demonstrated to generate a uniform square illumination pattern for an on-chip imaging flow cytometer system. The proposed system is used to perform the detection of a bead-based immunoassay for a sepsis biomarker, procalcitonin

Spatially superposed pulse amplitude modulation using a chip-scale CMOS-integrated GaN LED array

We present a highly compact system capable of generating discrete optical wireless data signals from logic inputs, suitable for pulse amplitude modulation (PAM) transmission, in visible light communication (VLC)

High speed spatial encoding enabled by CMOS-controlled micro-LED arrays

Arrays of GaN light-emitting diodes can be used for rapid display of pattern sequences or high speed parallel data transmission using different sites of the array. These operation modes can be combined with each other and are useful for light- fidelity networks with Gb/s capacity

Micro-LEDs for technological convergence between displays, optical communications, and sensing and imaging systems

Micro-LED displays are now emerging rapidly towards commercialization. This novel compound semiconductor display technology has the potential to interface very effectively to advanced electronics, in particular Si CMOS, to create new forms of display which also interrogate and communicate with their environment in sophisticated ways

Experimental demonstration of generalised space shift keying for visible light communication

A low complexity generalised space shift keying (GSSK) experimental set-up for visible light communication (VLC) is demonstrated. The GSSK encoder is implemented in a field programmable gate array (FPGA) board. No digitalto-analog converter (DAC) is required and up to 16 output channels are supported which greatly exceeds that of an arbitrary waveform generator (AWG). A 4 × 4 Gallium Nitride (GaN) micro-LED array is used as transmitter while 4 avalanche photo diode (APD) receiver boards are acting as receivers. GSSK exploits the natural differences between the multiple communication links. The bit error ratio (BER) performances are evaluated for different transmitter and receiver arrangements. It is also shown that how different receiver positions and increasing receiver number will affect the BER performance. The bit error performance greatly depends on the dissimilarity of the channel gains. A spectral efficiency of 16 bits/symbol is achieved by using all 16 micro-LEDs and 4 receivers. The implementation of the experiment is introduced in detail and experimental results are given

Fabrication, characterization and applications of flexible vertical InGaN micro-light emitting diode arrays

Flexible vertical InGaN micro-light emitting diode (micro-LED) arrays have been fabricated and characterized for potential applications in flexible micro-displays and visible light communication. The LED epitaxial layers were transferred from initial sapphire substrates to flexible AuSn substrates by metal bonding and laser lift off techniques. The current versus voltage characteristics of flexible micro-LEDs degraded after bending the devices, but the electroluminescence spectra show little shift even under a very small bending radius 3 mm. The high thermal conductivity of flexible metal substrates enables high thermal saturation current density and high light output power of the flexible micro-LEDs, benefiting the potential applications in flexible high-brightness micro-displays and high-speed visible light communication. We have achieved ~40 MHz modulation bandwidth and 120 Mbit/s data transmission speed for a typical flexible micro-LED

Size-dependent characterisation of deep UV micro-light-emitting diodes

Deep UV Micro LEDs (DUV-µLEDs) are attractive for optical wireless communications, however not much is known about their size-dependent characteristics. Here we study spectra, power output and bandwidth as a function of device size and achieve a bandwidth of 570MHz with a 20µm diameter device

CMOS-integrated GaN LED array for discrete power level stepping in visible light communications

We report a CMOS integrated micro-LED array capable of generating discrete optical output power levels. A 16 x 16 array of individually addressable pixels are on-off controlled through parallel logic signals. With carefully selected groups of LEDs driven together, signals suitable for discrete transmission schemes are produced. The linearity of the device is assessed, and data transmission using pulse amplitude modulation (PAM) and orthogonal frequency division multiplexing (OFDM) is performed. Error-free transmission at a symbol rate of 100 MSamples/s is demonstrated with 4-PAM, yielding a data rate of 200 Mb/s. For 8-PAM, encoding is required to overcome the baseline wander from the receiver, reducing the data rate to 150 Mb/s. We also present an experimental proof-of-concept demonstration of discrete-level OFDM, achieving a spectral efficiency of 3.96 bits/s/Hz

The Impact of Solar Irradiance on Visible Light Communications

This paper aims to address the perception that visible light communication (VLC) systems cannot work under the presence of sunlight. A complete framework is presented to evaluate the performance of VLC systems in the presence of solar irradiance at any given location and time. The effect of solar irradiance is investigated in terms of degradations in signal to noise ratio, data rate, and bit error rate. Direct current (DC) optical orthogonal frequency division multiplexing is used with adaptive bit and energy loading to mitigate DC wander interference and low-frequency ambient light noise. It was found that reliable communication can be achieved under the effect of solar irradiance at high-speed data rates. An optical bandpass blue filter is shown to compensate for half of the reduced data rate in the presence of sunlight. This work demonstrates data rates above 1 Gb/s of a VLC link under strong solar illuminance measured at 50350 lux in clear weather conditions

Temperature-dependent efficiency droop of blue InGaN micro-light emitting diodes

Temperature-dependent trends in radiative and Auger recombination coefficients have been determined at different injection carrier concentrations using InGaN micro-light emitting diodes 40 μm in diameter. The differential lifetime was obtained first from the measured modulation bandwidth and was then employed to calculate the carrier concentration in the quantum well active region. When the temperature increases, the carrier concentration increases, but both the radiative and Auger recombination coefficients decrease. In addition, the temperature dependence of radiative and Auger recombination coefficients is weaker at a higher injection carrier concentration, which is strongly related to phase space filling