Periodic Reporting for period 1 - SPINONICS (Integrated devices based on spin-orbit photonics.)
Periodo di rendicontazione: 2020-07-01 al 2023-06-30
The study of light and light-based technologies influences all aspects of human life. Geometric phase has led to several breakthroughs in optical science, leading to both fundamental discoveries and innovative applications. In this context, the EU project SPINONICS explored the implications of geometric phase in designing novel integrated optical devices. Such devices are based upon spin-orbit interactions in anisotropic materials featuring an inhomogeneous distribution of optic axis. This results in the so-called Pancharatnam-Berry phase (PBP). Properly tailoring this phase allows us to guide light in the absence of any gradient in the refractive index. Spin-orbit photonics has garnered much attention in the recent years, leading to the realization of a whole new family of optical devices, the so-called planar photonics.
Standard optical waveguides are limited in their ability to conserve information carried by light with both intensity and polarization structuring, a characteristic known as spin-orbit coupling. SPINONICS steps in at this stage by fabricating waveguides capable of supporting structured light and maximizing achievable bit rates. The specific application targeted is optical demultiplexing in data centers or between different cores within the same chip, where silicon photonics finds significant application. The relatively short distances that light travels in these scenarios reduce the impact of fabrication defects and external perturbations on waveguides, making spatial demultiplexing potentially viable.
In conclusion, the work carried out in the SPINONICS project represents an initial step toward realizing a new class of waveguides where full control over the properties of an optical beam can be achieved. While further experimental work on device implementation is necessary, the results obtained in this project demonstrate that these waveguides possess properties that cannot be attained in standard waveguides, with potential applications in various practical cases. In the process, we also discovered how these structures are of significant importance in studying phenomena of general interest in the field of physics.
Standard optical waveguides are limited in their ability to conserve information carried by light with both intensity and polarization structuring, a characteristic known as spin-orbit coupling. SPINONICS steps in at this stage by fabricating waveguides capable of supporting structured light and maximizing achievable bit rates. The specific application targeted is optical demultiplexing in data centers or between different cores within the same chip, where silicon photonics finds significant application. The relatively short distances that light travels in these scenarios reduce the impact of fabrication defects and external perturbations on waveguides, making spatial demultiplexing potentially viable.
In conclusion, the work carried out in the SPINONICS project represents an initial step toward realizing a new class of waveguides where full control over the properties of an optical beam can be achieved. While further experimental work on device implementation is necessary, the results obtained in this project demonstrate that these waveguides possess properties that cannot be attained in standard waveguides, with potential applications in various practical cases. In the process, we also discovered how these structures are of significant importance in studying phenomena of general interest in the field of physics.
The central idea in SPINONICS revolves around developing waveguides with controllable polarization and intensity. To achieve this, a system with strong spin-orbit interaction is chosen, utilizing anisotropic materials where the optical response depends on the input polarization. By rotating the axes of the anisotropic material on a point-wise basis, the spin-orbit interaction is maximized. The spatial rotation introduces an additional phase delay, known as the geometric phase, stemming from the rotation angle's gradient in a gauge field. In the structure made of twisted anisotropic materials, light is confined through the interplay between dynamic and geometric phases. The dynamic phase is associated with the material's refractive index, forming the foundation for standard waveguides. However, in this system, the accumulated phase is controlled through full 3D rotation of the material, allowing the shaping of modes in both polarization and intensity. From a fundamental physics perspective, this system can be modeled as a quantum particle in the presence of effective electric and magnetic fields, tunable through the geometry of the structure.
We then proceeded to investigate how short pulses propagate in waveguides solely based on a gradient in the geometric phase. Short pulses comprise several frequencies locked in phase. As each wavelength has a different velocity, optical pulses experience dispersion in a waveguide, meaning their temporal shape changes while propagating. Waveguides built upon the geometric phase exhibit much stronger dispersion than standard waveguides, offering high tunability in both magnitude and sign through geometric parameters. These unique properties have potential applications in dispersion management, such as guiding ultrashort pulses in waveguides or generating pulses in mode-locked lasers based on chirped pulse amplification.
Our exploration did not stop with single waveguides; we also delved into the response of coupled waveguides, a fundamental setting for creating integrated optical modulators. When two waveguides are positioned close to each other, they exchange energy coherently, enabling energy routing driven by the relative phase. Waveguides based on the geometric phase introduce additional degrees of freedom in designing such structures. By carefully designing the relative rotation angle between adjacent waveguides, we found that the coupling constant can be changed while keeping the waveguide positions unaltered. Remarkably, this enables the coupling to even become infinite, allowing two waveguides to be isolated from each other, despite their overlapping exponential tails.
While waveguides typically trap photons in a finite region on the plane perpendicular to the propagation direction, we explored the possibility of extending this confinement to the longitudinal direction, thus trapping light in a definite region of three-dimensional space. The question is if an optical resonator supporting structured modes can be realized. Our numerical investigations demonstrated that this is indeed possible. Coupled with an active material, such a configuration could lead to a laser directly emitting structured light with a tunable profile.
The results from SPINONICS have been published in several peer-reviewed journals as well as presented at many renowned conferences. The Project constitutes a fundamental science endeavour with its implementation for a possible new technological platform based on spin-orbit photonics. Over the last decade metasurface technology has become mainstream and has been commercialized (lab to consumer). On the same lines, we expect potential applications for PBP-based devices. However, at the current stage both the science and technology needed are in their infancy.
We then proceeded to investigate how short pulses propagate in waveguides solely based on a gradient in the geometric phase. Short pulses comprise several frequencies locked in phase. As each wavelength has a different velocity, optical pulses experience dispersion in a waveguide, meaning their temporal shape changes while propagating. Waveguides built upon the geometric phase exhibit much stronger dispersion than standard waveguides, offering high tunability in both magnitude and sign through geometric parameters. These unique properties have potential applications in dispersion management, such as guiding ultrashort pulses in waveguides or generating pulses in mode-locked lasers based on chirped pulse amplification.
Our exploration did not stop with single waveguides; we also delved into the response of coupled waveguides, a fundamental setting for creating integrated optical modulators. When two waveguides are positioned close to each other, they exchange energy coherently, enabling energy routing driven by the relative phase. Waveguides based on the geometric phase introduce additional degrees of freedom in designing such structures. By carefully designing the relative rotation angle between adjacent waveguides, we found that the coupling constant can be changed while keeping the waveguide positions unaltered. Remarkably, this enables the coupling to even become infinite, allowing two waveguides to be isolated from each other, despite their overlapping exponential tails.
While waveguides typically trap photons in a finite region on the plane perpendicular to the propagation direction, we explored the possibility of extending this confinement to the longitudinal direction, thus trapping light in a definite region of three-dimensional space. The question is if an optical resonator supporting structured modes can be realized. Our numerical investigations demonstrated that this is indeed possible. Coupled with an active material, such a configuration could lead to a laser directly emitting structured light with a tunable profile.
The results from SPINONICS have been published in several peer-reviewed journals as well as presented at many renowned conferences. The Project constitutes a fundamental science endeavour with its implementation for a possible new technological platform based on spin-orbit photonics. Over the last decade metasurface technology has become mainstream and has been commercialized (lab to consumer). On the same lines, we expect potential applications for PBP-based devices. However, at the current stage both the science and technology needed are in their infancy.
SPINONICS aimed to pioneer a new technology for the manipulation and control of light. Beyond their potential as photonic devices, the results from the SPINONICS project have profound implications for fundamental physics. We demonstrated how a rotation angle in an anisotropic material serves as a template for investigating wave propagation in the presence of a generic Hamiltonian. Additionally, we delved into the profound effects of effective gauge fields resulting from proper modulation of material properties, providing novel ways to control wave propagation. Furthermore, we explored the nonlinear regime, using highly nonlinear materials like liquid crystals. For the first time, we described how a wave propagates in the presence of a nonlinear geometric phase, where the geometric phase depends on the wave's amplitude. We also uncovered new phenomena in liquid crystals' nonlinear behavior, such as self-patterning in response to the properties of the incident optical beam—a phenomenon linked to the concept of time crystals recently introduced by Wilczek.
Photonics and associated technologies play a prominent role in every aspect of our society and a key driver for future developments. In fact, photonics is a key enabling technology for the EU. The results from SPINONICS will further enhance further enhance EUs position in photonics.
Photonics and associated technologies play a prominent role in every aspect of our society and a key driver for future developments. In fact, photonics is a key enabling technology for the EU. The results from SPINONICS will further enhance further enhance EUs position in photonics.