Periodic Reporting for period 1 - TeRrIFIC (Training in Quantum Photonics Design Fabrication and Characterisation)
Reporting period: 2018-04-09 to 2020-04-08
Information security is one of the most pressing issues facing the world today. With the increase in activities such as e-commerce and online banking, the opportunities for fraud and theft have never been greater. As data is transmitted over the internet, it is at its most vulnerable, so secure methods of encryption are essential. Quantum Information Communication Technology (qICT) exploits the laws of quantum mechanics to provide the ultimate in secure data transmission- the copying of data encoded in a quantum state changes the state, betraying the eavesdropper.
But for qICT and Quantum Cryptography to achieve mainstream deployment, practical, scalable sources of quantum states of light are required. To date, most demonstrations of quantum information processing or sensing have been based on bulky table-top light sources , or use attenuated lasers that intrinsically have a low generation rate or quantum dot light sources that need cryogenic cooling. Such approaches entail high production costs and poor operational performance. On-chip integration is key, as it offers reductions in cost and dense integration of components. In Terrific, the Fellow will develop an ultra-compact nanophotonic device based on Lithium Niobate on Insulator.
Lithium Niobate is one of the most popular materials for Nonlinear optics, however, it is extremely difficult to process which has limited applications to the use of bulk crystals or large mode area, low refractive index contrast waveguides. Consequently, typical devices are 10s of millimetres long . Recent advances in fabrication technologies now allow the realisation of Lithium Niobate on Insulator (LNoI) material which facilitates the creation of compact integrated devices. In this project, LNoI materials will be combined with silicon and silicon nitride layers to form hybrid waveguides that take advantage of the strong nonlinear optical coefficients of Lithium Niobate and of the high refractive contrast and ease of processing of silicon and silicon nitride. TERRIFIC implemented novel Lithium Niobate on insulator devices to provide compact and effective photon pair production.
But for qICT and Quantum Cryptography to achieve mainstream deployment, practical, scalable sources of quantum states of light are required. To date, most demonstrations of quantum information processing or sensing have been based on bulky table-top light sources , or use attenuated lasers that intrinsically have a low generation rate or quantum dot light sources that need cryogenic cooling. Such approaches entail high production costs and poor operational performance. On-chip integration is key, as it offers reductions in cost and dense integration of components. In Terrific, the Fellow will develop an ultra-compact nanophotonic device based on Lithium Niobate on Insulator.
Lithium Niobate is one of the most popular materials for Nonlinear optics, however, it is extremely difficult to process which has limited applications to the use of bulk crystals or large mode area, low refractive index contrast waveguides. Consequently, typical devices are 10s of millimetres long . Recent advances in fabrication technologies now allow the realisation of Lithium Niobate on Insulator (LNoI) material which facilitates the creation of compact integrated devices. In this project, LNoI materials will be combined with silicon and silicon nitride layers to form hybrid waveguides that take advantage of the strong nonlinear optical coefficients of Lithium Niobate and of the high refractive contrast and ease of processing of silicon and silicon nitride. TERRIFIC implemented novel Lithium Niobate on insulator devices to provide compact and effective photon pair production.
In TERRIFIC, Lithium Niobate on insulator was combined with a silicon nitride layer to form strip-loaded waveguides that can take advantage of the strong nonlinear optical coefficients of lithium niobate and of the high refractive contrast and ease of processing of silicon nitride. This approach has the advantage of being substrate based (as opposed to membraned or free standing structures) increasing the potential for integration with other devices and systems. The Fellow developed, fabricated and characterised a Fabry-Perot micro-cavity in such material for the first time. The Fabry-perot micro-cavity offers a high ease of fabrication, even mode spacing and excellent control over the free spectral range, which is advantageous for applications such as parametric down conversion amongst others. Distributed Bragg Reflectors (DBR) providing mirrors on both sides of the cavity in SiN are in the form of sidewall-width modulated structures with rectangular corrugations were used in our work. The design trade-offs implicit in the realisation of such microcavities of this nature were studied using the commercial software PhotonDesign FIMMPROP.
To fabricate the designed devices, the Fellow was trained to use an electron-beam lithography machine, inductively coupled plasma etching system and dielectric coater. On successful fabrication of devices, they were characterised using end-fire set up. The devices demonstrated an experimental quality factor of 2300, which was the highest experimentally reported result for such type of waveguide based Fabry-Perot cavity.
The results were published in peer-reviewed article titeld “Lithium Niobate Fabry-Perot microcavity based on strip loaded waveguides”, Photonics and Nanostructures - Fundamentals and Applications, Volume 43 (100886), 2021.
Micro-transfer printing was then chosen as alternative and more optimal way of combining LN and SiN. Micro-transfer printing is a technique for the heterogeneous integration of functional components fabricated on one substrate with those fabricated on another substrate. Thus, greater functionality is obtained than is possible with either substrate alone. The transfer printing technique is highly scalable, being based on the parallel transfer of the thin components using a stamping process. Crucially each material system can be optimized independently of the other. For instance, the silicon nitride may be processed at high temperatures or CMOS processes that would be impossible if lithium niobate were present. In this case, a thermal oxidised silicon wafer with thin Silicon Nitride (SiN) top layer from LIONIX was combined with a transfer printed layer of LN to form strip-loaded waveguides. The F-P micro-cavity with DBRs in SiN with transfer-printed LN was designed, fabricated and characterised in TERRIFIC. An experimentally measured intrinsic Q-factors of 50,000 was obtained. We believed this was the first realization of such type of a micro-cavity.
The results of this work were presented at the conference Optica Advanced Photonics Congress 2022 by the oral talk titled "Realization of a micro-cavity via the integration of Silicon Nitride and Lithium Niobate using micro transfer printing". A journal paper is in preparation.
To fabricate the designed devices, the Fellow was trained to use an electron-beam lithography machine, inductively coupled plasma etching system and dielectric coater. On successful fabrication of devices, they were characterised using end-fire set up. The devices demonstrated an experimental quality factor of 2300, which was the highest experimentally reported result for such type of waveguide based Fabry-Perot cavity.
The results were published in peer-reviewed article titeld “Lithium Niobate Fabry-Perot microcavity based on strip loaded waveguides”, Photonics and Nanostructures - Fundamentals and Applications, Volume 43 (100886), 2021.
Micro-transfer printing was then chosen as alternative and more optimal way of combining LN and SiN. Micro-transfer printing is a technique for the heterogeneous integration of functional components fabricated on one substrate with those fabricated on another substrate. Thus, greater functionality is obtained than is possible with either substrate alone. The transfer printing technique is highly scalable, being based on the parallel transfer of the thin components using a stamping process. Crucially each material system can be optimized independently of the other. For instance, the silicon nitride may be processed at high temperatures or CMOS processes that would be impossible if lithium niobate were present. In this case, a thermal oxidised silicon wafer with thin Silicon Nitride (SiN) top layer from LIONIX was combined with a transfer printed layer of LN to form strip-loaded waveguides. The F-P micro-cavity with DBRs in SiN with transfer-printed LN was designed, fabricated and characterised in TERRIFIC. An experimentally measured intrinsic Q-factors of 50,000 was obtained. We believed this was the first realization of such type of a micro-cavity.
The results of this work were presented at the conference Optica Advanced Photonics Congress 2022 by the oral talk titled "Realization of a micro-cavity via the integration of Silicon Nitride and Lithium Niobate using micro transfer printing". A journal paper is in preparation.
During TERRIFIC, the Fellow made one of the first demonstrations of transfer print lithium niobate on silicon nitride. The Fellow believes this to be the optimum approach for combining the two materials. The published results technology attracted the interest of German quantum computing start-up leading to the submission of a EIC Pathfinder project, in which the Fellow will lead the Silicon-nitride based photonic integrated circuit work package. The team believes that the LN/SiN combination will ultimately be the best means of generating deterministic single photons.
The Fellow also learned to fabricate metasurfaces, which expanded her range of skills and generated additional publication such as "A dual-functionality metalens to shape a circularly polarized optical vortex or a second-order cylindrical vector beam”, Photonics and Nanostructures - Fundamentals and Applications, Volume 43 (100898), 2021.
The Fellow made a successful application to Science Foundation Ireland (SFI) Irish Research Council (IRC) pathway funding for her project APTIMON that received over €500k funding for four years. The APTIMON project focuses on a novel integrated photo-thermal spectroscopic method for monitoring bacterial growth and assessing antimicrobial effects.
Thanks to the support provided by Marie Cure Sklodowska foundation, the Fellow has been very successful in restarting her career, as clearly demonstrated by the start of the new APTIMON project, which also have one PhD student funded by it, who will be working under the Fellow's supervision.
The Fellow also learned to fabricate metasurfaces, which expanded her range of skills and generated additional publication such as "A dual-functionality metalens to shape a circularly polarized optical vortex or a second-order cylindrical vector beam”, Photonics and Nanostructures - Fundamentals and Applications, Volume 43 (100898), 2021.
The Fellow made a successful application to Science Foundation Ireland (SFI) Irish Research Council (IRC) pathway funding for her project APTIMON that received over €500k funding for four years. The APTIMON project focuses on a novel integrated photo-thermal spectroscopic method for monitoring bacterial growth and assessing antimicrobial effects.
Thanks to the support provided by Marie Cure Sklodowska foundation, the Fellow has been very successful in restarting her career, as clearly demonstrated by the start of the new APTIMON project, which also have one PhD student funded by it, who will be working under the Fellow's supervision.