We demonstrate Compact on-chip spectrometers on a silicon on insulator based on correlated periodic disordered planar waveguides with high spectral resolution and small footprint compared to conventional spectrometers.
Propagation of light through the scattering medium generates a granular distribution of intensity called speckle pattern which is frequency-dependent. The working principle of the disorder spectrometer is based on the analysis of the speckle pattern. Spectral to spatial mapping is stored in a calibration transmission matrix. Later unknown spectrum is reconstructed by matrix inversion.
However, current disorder-based speckle spectrometers have prohibitively high optical losses - most of the light is scattered out-of-plane, and never reaches the detection region, resulting in poor efficiency and signal to noise ratio. we propose a game-changing, disorder-enhanced wavelength separation region that creates an in-plane speckle and simultaneously suppresses out-of-plane scattering, leading to compact and sensitive high-resolution spectrometers. Controlled disorder, with known scattering statistics, is superposed onto a period PhC lattice. The device combines the ideal parts of random and perfectly ordered photonic devices and provides the missing component for high-resolution, USB-key-sized spectrometers.
Advantage of the random spectrometer is that it can operate over an extremely broad frequency range without any structural modification. This is not the case in grating-based spectrometer, which requires a rotation of the grating to diffract light of varying frequency to the detector.
We demonstrate Compact on-chip spectrometers on a silicon on insulator based on correlated periodic disordered planar waveguides with high spectral resolution and small footprint compared to conventional spectrometers.
Propagation of light through the scattering medium generates a granular distribution of intensity called speckle pattern which is frequency-dependent. The working principle of the disorder spectrometer is based on the analysis of the speckle pattern. Spectral to spatial mapping is stored in a calibration transmission matrix. Later unknown spectrum is reconstructed by matrix inversion.
However, current disorder-based speckle spectrometers have prohibitively high optical losses - most of the light is scattered out-of-plane, and never reaches the detection region, resulting in poor efficiency and signal to noise ratio. we propose a game-changing, disorder-enhanced wavelength separation region that creates an in-plane speckle and simultaneously suppresses out-of-plane scattering, leading to compact and sensitive high-resolution spectrometers. Controlled disorder, with known scattering statistics, is superposed onto a period PhC lattice. The device combines the ideal parts of random and perfectly ordered photonic devices and provides the missing component for high-resolution, USB-key-sized spectrometers.
Advantage of the random spectrometer is that it can operate over an extremely broad frequency range without any structural modification. This is not the case in grating-based spectrometer, which requires a rotation of the grating to diffract light of varying frequency to the detector.
Amongst the antenna designs that yield an ultrawideband (UWB) response with an omnidirectional spatial coverage, the planar inverted cone antenna (PICA) has emerged as one of the most promising designs in the last two decades. A PICA is composed of a semicircle, which is extended into an inverted cone from the flat side. Moreover, due to the flat profile, the PICA exhibits mechanical stability due to which it is increasingly being used for commercial applications. we presented for the first time in literature a fabricated and experimentally measured, novel and simple ultrawideband omnidirectional 1×4 THz PICA array with a 37.9 % bandwidth with a central frequency of 0.92 THz.
Amongst the antenna designs that yield an ultrawideband (UWB) response with an omnidirectional spatial coverage, the planar inverted cone antenna (PICA) has emerged as one of the most promising designs in the last two decades. A PICA is composed of a semicircle, which is extended into an inverted cone from the flat side. Moreover, due to the flat profile, the PICA exhibits mechanical stability due to which it is increasingly being used for commercial applications. we presented for the first time in literature a fabricated and experimentally measured, novel and simple ultrawideband omnidirectional 1×4 THz PICA array with a 37.9 % bandwidth with a central frequency of 0.92 THz.
Inspired by the multistability and programmability of kirigami-based self-folding elements, a robust framework is introduced for the construction of sequentially programmable and reprogrammable mechanical metamaterials. The materials can be locked into a stable deployed configuration, then, using tunable bistability enabled by temperature-responsive constituent materials, return to their original reference configurations or undergo mode bifurcation. The framework provides a platform to design metamaterials with multiple deployable and reversible configurations in response to external stimuli. We envision a range of additional applications for these multi-step, multimodal mechanical metamaterials across different length scales. For example, millimeter-level vascular stents are limited to a single deployed shape that is determined prior to surgery, but no longer need to be limited in this way. Metamaterials with some actuation encoded via self-folding can enable complex motions with fewer actuators and simplifies control. The methods of this paper can enable robots and deployable structures to adopt a plurality of shapes and configurations, possibly extending to large, stable deployable structures.
Inspired by the multistability and programmability of kirigami-based self-folding elements, a robust framework is introduced for the construction of sequentially programmable and reprogrammable mechanical metamaterials. The materials can be locked into a stable deployed configuration, then, using tunable bistability enabled by temperature-responsive constituent materials, return to their original reference configurations or undergo mode bifurcation. The framework provides a platform to design metamaterials with multiple deployable and reversible configurations in response to external stimuli. We envision a range of additional applications for these multi-step, multimodal mechanical metamaterials across different length scales. For example, millimeter-level vascular stents are limited to a single deployed shape that is determined prior to surgery, but no longer need to be limited in this way. Metamaterials with some actuation encoded via self-folding can enable complex motions with fewer actuators and simplifies control. The methods of this paper can enable robots and deployable structures to adopt a plurality of shapes and configurations, possibly extending to large, stable deployable structures.
This picture shows the scanning electron microscope image of a polymerised metasurface pattern stuck on a single-mode fiber tip (the inset shows the corresponding optical microscope image), which is the preliminary stage result of our project 'Transfering Ultra-thin Metasurfaces onto Fiber Endoscope Probes for Advanced Imaging'. The aim of this project is to flexibly transfer multi-layer stacks of custom-designed metasurface patterns onto optical fiber tips, which is useful to unlock the full range of possible fiber-endoscopic imaging devices.
This picture shows the scanning electron microscope image of a polymerised metasurface pattern stuck on a single-mode fiber tip (the inset shows the corresponding optical microscope image), which is the preliminary stage result of our project 'Transfering Ultra-thin Metasurfaces onto Fiber Endoscope Probes for Advanced Imaging'. The aim of this project is to flexibly transfer multi-layer stacks of custom-designed metasurface patterns onto optical fiber tips, which is useful to unlock the full range of possible fiber-endoscopic imaging devices.
A broadband dual circularly polarized (dual-CP)reflectarray based on three-dimensional (3D) printed dielectric materials is presented. A novel 3D dielectric arrayelement that enables the broadband linearly polarization (LP) to CP transformation is proposed. The unit cell consists oftwo orthogonal dielectric cuboids, which adjust the phases ofthe two orthogonal LP waves independently and then combinethem into a CP wave. The innovative unit cell design providesan extra degree of freedom in varying the geometries of thearray elements in all three dimensions, which enables us to independently control the phases of the two LP waves. This maintains an equal amplitude and 90? phase difference condition across the entire reflectarray surface, realizing a broadbandand high gain LP-CP reflectarray. The reflectarray is able to provide bothleft-hand circular polarization (LHCP) and right-hand circular polarization (RHCP), with just an LP feed. The measurements demostrate the maximum realized gain and directivity at 34 GHz are measured as 27.9 dBi and 28.1 dBi, respectively. The measured 3-dB gain bandwidth and aperture efficiency are 30% and up to 38%, respectively. More importantly, a broad 3-dB axial ratio (AR) bandwidth greater than 40% has been achieved for both LHCP and RHCP, covering almost the entire frequency band of interest, ranging from 26 to40 GHz.
A broadband dual circularly polarized (dual-CP)reflectarray based on three-dimensional (3D) printed dielectric materials is presented. A novel 3D dielectric arrayelement that enables the broadband linearly polarization (LP) to CP transformation is proposed. The unit cell consists oftwo orthogonal dielectric cuboids, which adjust the phases ofthe two orthogonal LP waves independently and then combinethem into a CP wave. The innovative unit cell design providesan extra degree of freedom in varying the geometries of thearray elements in all three dimensions, which enables us to independently control the phases of the two LP waves. This maintains an equal amplitude and 90? phase difference condition across the entire reflectarray surface, realizing a broadbandand high gain LP-CP reflectarray. The reflectarray is able to provide bothleft-hand circular polarization (LHCP) and right-hand circular polarization (RHCP), with just an LP feed. The measurements demostrate the maximum realized gain and directivity at 34 GHz are measured as 27.9 dBi and 28.1 dBi, respectively. The measured 3-dB gain bandwidth and aperture efficiency are 30% and up to 38%, respectively. More importantly, a broad 3-dB axial ratio (AR) bandwidth greater than 40% has been achieved for both LHCP and RHCP, covering almost the entire frequency band of interest, ranging from 26 to40 GHz.
This is an antenna loaded with a reconfigurable metamaterial. A simple radio wave is fed into the antenna while the metamaterial is changed using a voltage signal. This alters the radio wave as it passes through the metamaterial, putting information onto it - a process called modulation. This means the whole structure acts as a radio transmitter, sending information through the air. It is an energy efficient alternative to conventional transmitters, which have to use complex and ineffecient circuits to amplify complex modulated signals, while this design modulates the signal on the already amplified radio wave. It could be used to make energy efficient mobile base stations and WiFi access points, helping us move towards net zero wireless networks.
This is an antenna loaded with a reconfigurable metamaterial. A simple radio wave is fed into the antenna while the metamaterial is changed using a voltage signal. This alters the radio wave as it passes through the metamaterial, putting information onto it - a process called modulation. This means the whole structure acts as a radio transmitter, sending information through the air. It is an energy efficient alternative to conventional transmitters, which have to use complex and ineffecient circuits to amplify complex modulated signals, while this design modulates the signal on the already amplified radio wave. It could be used to make energy efficient mobile base stations and WiFi access points, helping us move towards net zero wireless networks.
This funnel-shaped metamaterial, which we refer to as a heat spreader, acts as a point-to-plane heat source converter. We see that, in contrast to the nonuniform distribution of heat observed throughout the natural material, our design guides the flow of heat in a uniform manner - leading to a controlled, uniform temperature across the top surface. This is particularly useful in heat sink and heat plate applications where we wish to either maximise the rate at which heat is dissipated from the top surface or make sure that something is heated evenly.
The realisation of metamaterials often presents a significant challenge - especially when the ideal properties exhibit both spatial and directional dependence. However, by carefully choosing our transformation we can accurately approximate our metamaterial regions with simple, rotated laminates. Therefore, a huge advantage of our metamaterial design is its simplicity.
For more information on this topic check out our recent paper on heat spreaders:
https://doi.org/10.1016/j.apm.2022.01.026
This funnel-shaped metamaterial, which we refer to as a heat spreader, acts as a point-to-plane heat source converter. We see that, in contrast to the nonuniform distribution of heat observed throughout the natural material, our design guides the flow of heat in a uniform manner - leading to a controlled, uniform temperature across the top surface. This is particularly useful in heat sink and heat plate applications where we wish to either maximise the rate at which heat is dissipated from the top surface or make sure that something is heated evenly.
The realisation of metamaterials often presents a significant challenge - especially when the ideal properties exhibit both spatial and directional dependence. However, by carefully choosing our transformation we can accurately approximate our metamaterial regions with simple, rotated laminates. Therefore, a huge advantage of our metamaterial design is its simplicity.
For more information on this topic check out our recent paper on heat spreaders:
https://doi.org/10.1016/j.apm.2022.01.026