Periodic Reporting for period 2 - Dynamo (Dynamic Spatio-Temporal Modulation of Light by Phononic Architectures)
Berichtszeitraum: 2023-03-01 bis 2024-08-31
Imaging technologies are ubiquitous, helping us monitoring our health, exploring our environment and in our telecommunications. At the heart of every optical imaging technology lies a component responsible for shaping the light beam in a spatial pattern according to an electrical or optical input. The incident light can be modulated in its phase, intensity, polarization, or direction, originated by various electro-optic or magneto-optic effects and by materials that modulate light by surface deformation. The most enduring, and continuously evolving, component in charge of this light modulation is the Spatial Light Modulator (SLM). The SLMs were originally developed for use as digital display screen technology, where large arrays of individual electronically addressable pixels must rapidly modulate light by some physical means to produce an image (an analogue is digital light projectors for feature films and presentations). Perhaps the most familiar example of this technology is the liquid crystal display (LCD), where electronic control of the liquid crystal orientation allows control of optical polarization, and, in combination with a polarizer, amplitude modulation of a backlight.
The major limitations in current imaging technologies are speed and resolution, and both impediments are originated by how the light is modulated in the device. Limitations in resolution have been overcome by several methods, some of them even deserving the Nobel prize, however the speed at which the spatial modulation of light is shaped remains limited by the refresh rate of current SLMs, which is of the order of 100kHz for the best of the devices. This is because SLMs and similar components operate sequentially, that is to say, they shape the light beam in different patterns but the time interval between patterns is limited by the refresh rate of the device. In Dynamo we will develop a breakthrough technology that will send all the possible patterns of the device simultaneously, and encoded in a short pulse of one nanosecond, creating the concept of parallel beam shaping or dynamic spatio-temporal light modulation device.
To give an idea of the magnitude of this breakthrough, we compare this improvement in the time to process images with the improvement in the clock frequency of computers: the first general purpose electronic computer, the ENIAC, had a clock frequency of 100kHz in 1945. It was not until 2000 where AMD reached the 1 GHz in their computers. Processing images is broadly similar to processing data in general, so this is indicative of a jump forwards of fifty years in the realm of imaging; the outcomes from this project offer to accelerate imaging technologies and place European science and industry at the forefront of the inventions and advances that will follow.
The major limitations in current imaging technologies are speed and resolution, and both impediments are originated by how the light is modulated in the device. Limitations in resolution have been overcome by several methods, some of them even deserving the Nobel prize, however the speed at which the spatial modulation of light is shaped remains limited by the refresh rate of current SLMs, which is of the order of 100kHz for the best of the devices. This is because SLMs and similar components operate sequentially, that is to say, they shape the light beam in different patterns but the time interval between patterns is limited by the refresh rate of the device. In Dynamo we will develop a breakthrough technology that will send all the possible patterns of the device simultaneously, and encoded in a short pulse of one nanosecond, creating the concept of parallel beam shaping or dynamic spatio-temporal light modulation device.
To give an idea of the magnitude of this breakthrough, we compare this improvement in the time to process images with the improvement in the clock frequency of computers: the first general purpose electronic computer, the ENIAC, had a clock frequency of 100kHz in 1945. It was not until 2000 where AMD reached the 1 GHz in their computers. Processing images is broadly similar to processing data in general, so this is indicative of a jump forwards of fifty years in the realm of imaging; the outcomes from this project offer to accelerate imaging technologies and place European science and industry at the forefront of the inventions and advances that will follow.
During the first year of the Dynamo project, the following tasks have been developed:
1- Formulation of the theoretical aspects of the new imaging concept we are introducing
2- Development efficient algorithms for the calculation of localized modes in engineered phononic surfaces
3- Development of a picosecond ultrasonics setup
4- Fabrication and characterization of phononic surfaces with ordered and quasi-periodic patterns for calibration of the setup
During the second and early third year of the Dynamo project, the following tasks have been also developed:
5. We have developed several numerical methods based on multiple scattering theory to study complex distribution of scatterers. The most remarkable result concerning the theoretical part of the project is the development of Bloch-based equations for the description of quasi-periodic structures.
6. An efficient optimization framework for the design of structured phononic surfaces have been developed, allowing the identification of the most sensitive parameters of their design.
7. A wide variety of microstructures have been fabricated, consisting of periodic, random and quasi-periodic distributions of pillars and holes of 1-3 micrometers of diameter deposited atop a surface. These large-area distributions of scatterers allow for the efficient study of space-invariant characteristics of wave propagation through complex media and their possible use as phononic devices.
8. An ultra-fast characterization setup for measuring SAWs in the range 0.5 to 5 GHz have been developed and improved. It is possible now to detect these waves with three different methods (interferometry, reflectometry and deflectometry) with picosecond resolution over a range of 12.5ns.
1- Formulation of the theoretical aspects of the new imaging concept we are introducing
2- Development efficient algorithms for the calculation of localized modes in engineered phononic surfaces
3- Development of a picosecond ultrasonics setup
4- Fabrication and characterization of phononic surfaces with ordered and quasi-periodic patterns for calibration of the setup
During the second and early third year of the Dynamo project, the following tasks have been also developed:
5. We have developed several numerical methods based on multiple scattering theory to study complex distribution of scatterers. The most remarkable result concerning the theoretical part of the project is the development of Bloch-based equations for the description of quasi-periodic structures.
6. An efficient optimization framework for the design of structured phononic surfaces have been developed, allowing the identification of the most sensitive parameters of their design.
7. A wide variety of microstructures have been fabricated, consisting of periodic, random and quasi-periodic distributions of pillars and holes of 1-3 micrometers of diameter deposited atop a surface. These large-area distributions of scatterers allow for the efficient study of space-invariant characteristics of wave propagation through complex media and their possible use as phononic devices.
8. An ultra-fast characterization setup for measuring SAWs in the range 0.5 to 5 GHz have been developed and improved. It is possible now to detect these waves with three different methods (interferometry, reflectometry and deflectometry) with picosecond resolution over a range of 12.5ns.
So far the results achieved have arleady demonstrated the possibility to:
1- Perform single detector imaging with time-modulated surfaces.
2- Designing of bound states in the continuum for SAWs.
3- Ultrafast calculation of resonant modes of randomly placed elastic resonators.
4- Fabrication of large area moiré patterns for SAWs
5- Computing the dispersion relation of moiré distributions of scatterers
6- Fabricating large area phononic crystals with different kind of distributions
7- Optimizing resonant structures in a given frequency domain
8- Spatio-temporally resolve complex surface acoustic fields
9- Develop spatial light modulators at operating frequencies higher than 1GHz
[1] Mendoza‐Carreño, J., Molet, P., Otero‐Martínez, C., Alonso, M. I., Polavarapu, L., & Mihi, A. (2023). Nanoimprinted 2D‐chiral Perovskite Nanocrystal Metasurfaces for Circularly Polarized Photoluminescence. Advanced Materials, 2210477.
[2] Marc Martí-Sabaté, Bahram Djafari-Rouhani, and Dani Torrent. (2023). Bound states in the continuum in circular clusters of scatterers. Phys. Rev. Research 5, 013131
1- Perform single detector imaging with time-modulated surfaces.
2- Designing of bound states in the continuum for SAWs.
3- Ultrafast calculation of resonant modes of randomly placed elastic resonators.
4- Fabrication of large area moiré patterns for SAWs
5- Computing the dispersion relation of moiré distributions of scatterers
6- Fabricating large area phononic crystals with different kind of distributions
7- Optimizing resonant structures in a given frequency domain
8- Spatio-temporally resolve complex surface acoustic fields
9- Develop spatial light modulators at operating frequencies higher than 1GHz
[1] Mendoza‐Carreño, J., Molet, P., Otero‐Martínez, C., Alonso, M. I., Polavarapu, L., & Mihi, A. (2023). Nanoimprinted 2D‐chiral Perovskite Nanocrystal Metasurfaces for Circularly Polarized Photoluminescence. Advanced Materials, 2210477.
[2] Marc Martí-Sabaté, Bahram Djafari-Rouhani, and Dani Torrent. (2023). Bound states in the continuum in circular clusters of scatterers. Phys. Rev. Research 5, 013131