Development and implementation of monolithic GaN uLED arrays for multifunctional optical systems

Monolithic LED arrays comprising micron-sized pixels are rapidly maturing as a technology due to their high efficiency and modulation rates. When coupled with complementary metal-oxide semiconductor (CMOS) electronics, which offer high level spatiotemporal control, such devices are capable of communications based applications along with the ability to provide structured illumination based functionality. This novel 'smart display' technology opens up a range of potential new applications. This thesis describes the full development of such micro-LED arrays from initial design and fabrication through to implementation. By manipulating their fabrication process, highly customised devices can be created to accommodate the needs of a specialised setup or application scenarios. An example of this is the creation of n-contact devices and modifying the epitaxial structure of the array to allow for individually addressable pixels to better suit specific driving electronics. Devices such as these were developed and characterised. When compared to existing state-of-the art alternatives, these devices are shown to be either comparable with or to exceed them in terms of modulation rate and optical power output. In addition to modifying LED epitaxy to create novel applications, arrays of LEDs can also be implemented to create imaging systems capable of 3D imaging using only a single camera. This setup along with the steps taken to optimise the process is also detailed. Furthermore it includes the incorporation of a 3-dimensional tracking system, which can be used simultaneously with 3D imaging. Along with new technologies introduced by micro-LED arrays, they can also be used to improve existing technologies and even add additional functionality to them. This thesis documents the development of a maskless photolithography setup wherein the optical emission pattern of the micro-LEDs is controllable through CMOS drivers to implement a direct writing tool and replace the quartz masks, typically used in photolithography. The setup is shown to be capable of producing highly uniform photolithography defined structures of controllable width across a 16 x 16 grid where each coordinate is individually addressable. By synchronising the LED array's emission pattern with a motorised XYZ stage, continuous customisable directly written structures can be developed. Along with the photocuring components of the setup, an additional LED array was incorporated allowing for additional functionality through structured illumination. This comes in the form of the recognition, tracking and automated alignment to non-standardised alignment markers on a micrometre scale. Photocuring was performed whilst aligned to these markers while simultaneously tracking these markers to ensure the quality of fabricated structures.Monolithic LED arrays comprising micron-sized pixels are rapidly maturing as a technology due to their high efficiency and modulation rates. When coupled with complementary metal-oxide semiconductor (CMOS) electronics, which offer high level spatiotemporal control, such devices are capable of communications based applications along with the ability to provide structured illumination based functionality. This novel 'smart display' technology opens up a range of potential new applications. This thesis describes the full development of such micro-LED arrays from initial design and fabrication through to implementation. By manipulating their fabrication process, highly customised devices can be created to accommodate the needs of a specialised setup or application scenarios. An example of this is the creation of n-contact devices and modifying the epitaxial structure of the array to allow for individually addressable pixels to better suit specific driving electronics. Devices such as these were developed and characterised. When compared to existing state-of-the art alternatives, these devices are shown to be either comparable with or to exceed them in terms of modulation rate and optical power output. In addition to modifying LED epitaxy to create novel applications, arrays of LEDs can also be implemented to create imaging systems capable of 3D imaging using only a single camera. This setup along with the steps taken to optimise the process is also detailed. Furthermore it includes the incorporation of a 3-dimensional tracking system, which can be used simultaneously with 3D imaging. Along with new technologies introduced by micro-LED arrays, they can also be used to improve existing technologies and even add additional functionality to them. This thesis documents the development of a maskless photolithography setup wherein the optical emission pattern of the micro-LEDs is controllable through CMOS drivers to implement a direct writing tool and replace the quartz masks, typically used in photolithography. The setup is shown to be capable of producing highly uniform photolithography defined structures of controllable width across a 16 x 16 grid where each coordinate is individually addressable. By synchronising the LED array's emission pattern with a motorised XYZ stage, continuous customisable directly written structures can be developed. Along with the photocuring components of the setup, an additional LED array was incorporated allowing for additional functionality through structured illumination. This comes in the form of the recognition, tracking and automated alignment to non-standardised alignment markers on a micrometre scale. Photocuring was performed whilst aligned to these markers while simultaneously tracking these markers to ensure the quality of fabricated structures

Foot-and-mouth disease virus genome replication is unaffected by inhibition of type III phosphatidylinositol-4-kinases

Foot-and-mouth disease virus (FMDV) causes economically-damaging infections of cloven-hooved animals, with outbreaks resulting in large financial losses to the agricultural industry. Due to the highly contagious nature of FMDV, research with infectious virus is restricted to a limited number of key facilities worldwide. FMDV subgenomic replicons are therefore important tools for the study of viral translation and genome replication. The type III phosphatidylinositol-4-kinases (PI4K) are a family of enzymes that play a key role in the production of replication complexes (viral factories) of a number of positive-sense RNA viruses and represents a potential target for novel pan-viral therapeutics. Here, we have investigated whether type III PI4Ks also play a role in the FMDV lifecycle, using a combination of FMDV subgenomic replicons and bicistronic IRES-containing reporter plasmids. We have demonstrated that replication of the FMDV replicon was unaffected by inhibitors of either PI4KIIIα or PI4KIIIβ. However, PIK93, an inhibitor previously demonstrated to target PI4KIIIβ, did inhibit IRES-mediated protein translation. Consistent with this, cells transfected with FMDV replicons did not exhibit elevated levels of PI4P lipids. These results are therefore supportive of the hypothesis that FMDV genome replication does not require type III PI4K activity and does not activate these kinases

Digital illumination in microscale direct-writing photolithography : challenges and trade-off

We explore the adaptation of existing photolithography technologies and introduce the potential for additional functionality in the form of structured light. By using a complementary metal oxide semiconductor (CMOS) controlled micropixellated light emitting diode (LED) array, features such as object recognition, tracking and characterization are possible in combination with photo-curing. We discuss the observed trade off between the delivered power density and resolution capability of the system due to the requirements of the additional features

LED-based photometric stereo-imaging employing frequency-division multiple access

Among the many techniques developed for 3D imaging, photometric stereo-imaging excels through the simplicity of the hardware required. It can be used stand-alone or in fusion with other 3D imaging techniques for applications such as 3D scanners, face recognition or surveillance applications [1], [2][2], [3][3], [4][4], [5]. In photometric stereo-imaging, the subject is illuminated by different light sources from different angles, and the surface shades created by each light source allow reconstruction of 3D information

Lighting as a service that provides simultaneous 3D imaging and optical wireless connectivity

Light-emitting diodes enable optical wireless data transmission and advanced imaging methods such as photometric stereo-imaging. Both, wireless communications into a scene and 3D imaging of that scene is enabled in parallel using the same set of LEDs thus providing lighting-based infrastructure e.g. for automated agents

Design, fabrication and application of GaN-based micro-LED arrays with individual addressing by n-electrodes

We demonstrate the development, performance and application of a GaN-based micro-light emitting diode (μLED) array sharing a common p-electrode (anode), and with individually addressable nelectrodes (cathodes). Compared to conventional GaN-based LED arrays, this array design employs a reversed structure of common and individual electrodes, which makes it innovative and compatible with n-type metal-oxide-semiconductor (NMOS) transistor-based drivers for faster modulation. Excellent performance characteristics are illustrated by an example array emitting at 450 nm. At a current density of 17.7 kA/cm2 in direct-current operation, the optical power and small signal electrical-to-optical modulation bandwidth of a single LED element with 24 μm diameter are over 2.0 mW and 440 MHz, respectively. The optimized fabrication process also ensures a high yield of working μLED elements per array, and excellent element-to-element uniformity of electrical/optical characteristics. Results on visible light communication are presented as an application of an array integrated with an NMOS driver. Data transmission at several hundred Mbps without bit error is achieved for single and multiple-μLED-element operations, under an on-off-keying modulation scheme. Transmission of stepped sawtooth waveforms is also demonstrated to confirm that the μLED elements can transmit discrete multi-level signals

Design, fabrication and application of GaN-based micro-LED arrays with individual addressing by n-electrodes

We demonstrate the development, performance and application of a GaN-based micro-light emitting diode (μLED) array sharing a common p-electrode (anode), and with individually addressable nelectrodes (cathodes). Compared to conventional GaN-based LED arrays, this array design employs a reversed structure of common and individual electrodes, which makes it innovative and compatible with n-type metal-oxide-semiconductor (NMOS) transistor-based drivers for faster modulation. Excellent performance characteristics are illustrated by an example array emitting at 450 nm. At a current density of 17.7 kA/cm2 in direct-current operation, the optical power and small signal electrical-to-optical modulation bandwidth of a single LED element with 24 μm diameter are over 2.0 mW and 440 MHz, respectively. The optimized fabrication process also ensures a high yield of working μLED elements per array, and excellent element-to-element uniformity of electrical/optical characteristics. Results on visible light communication are presented as an application of an array integrated with an NMOS driver. Data transmission at several hundred Mbps without bit error is achieved for single and multiple-μLED-element operations, under an on-off-keying modulation scheme. Transmission of stepped sawtooth waveforms is also demonstrated to confirm that the μLED elements can transmit discrete multi-level signals

The broad-spectrum antiviral drug arbidol inhibits foot-and-mouth disease virus genome replication

Arbidol (ARB, also known as umifenovir) is used clinically in several countries as an anti-influenza virus drug. ARB inhibits multiple enveloped viruses in vitro and the primary mode of action is inhibition of virus entry and/or fusion of viral membranes with intracellular endosomal membranes. ARB is also an effective inhibitor of non-enveloped poliovirus types 1 and 3. In the current report, we evaluate the antiviral potential of ARB against another picornavirus, foot-and-mouth disease virus (FMDV), a member of the genus Aphthovirus and an important veterinary pathogen. ARB inhibits the replication of FMDV RNA sub-genomic replicons. ARB inhibition of FMDV RNA replication is not a result of generalized inhibition of cellular uptake of cargo, such as transfected DNA, and ARB can be added to cells up to 3 h post-transfection of FMDV RNA replicons and still inhibit FMDV replication. ARB prevents the recovery of FMDV replication upon withdrawal of the replication inhibitor guanidine hydrochloride (GuHCl). Although restoration of FMDV replication is known to require de novo protein synthesis upon GuHCl removal, ARB does not suppress cellular translation or FMDV internal ribosome entry site (IRES)-driven translation. ARB also inhibits infection with the related Aphthovirus, equine rhinitis A virus (ERAV). Collectively, the data demonstrate that ARB can inhibit some non-enveloped picornaviruses. The data are consistent with inhibition of picornavirus genome replication, possibly via the disruption of intracellular membranes on which replication complexes are located

Development, performance and application of novel GaN-based micro-LED arrays with individually addressable n-electrodes

We demonstrate the development, performance and application of a GaN-based micro-light emitting diode array sharing a common p-electrode with individual-addressed n-electrodes. These individually-addressed n-electrodes minimize the series-resistance difference from conductive paths, and offer compatibility with n-type metal-oxide-semiconductor transistor-based drivers for faster modulation