For many years silica fibers have been used for long-distance transfer of quantum information, and in particular within the domain of quantum communications and quantum key distribution.This is in part due to the ability to transmit tens of kilometers with negligible decoherence and loss.Although optical fibers fabricated with transparent materials such as SiO2 allow for the necessary low-loss transmission, they lack the photon-photon nonlinearity that are necessary for implementation of the other aspect of quantum information, that of quantum computation.The necessary nonlinearity, that is weak in SiO2, is stronger in material such as silicon nitride.In fact, silicon nitride has proven to be a promising platform for the generation and manipulation of single photons.The strong optical nonlinearity allows for parametric four-wave mixing which can be utilized to generate twin photons, while the transparency of silicon nitride in the near IR allows for low loss wave guides to be fabricated.However, due to silicon nitride's This work is dedicated to my wife, son, and entire family.A special feeling of gratitude to my loving wife Caitlin who was always supportive during late nights and frustrations; to Axl who always puts a smile on my face; and to my parents, brothers, sisters, and in-laws who supported and encouraged me throughout the entire program.viii
The capability of realizing quantum photonics implementations on-chip will have a strong impact on several aspects of quantum computation and information processing. The implementation of large scale integrated quantum photonic technologies requires on-chip reconfigurable waveguide circuits as well as single-photon sources and detectors. Many successes have been made in recent years to demonstrate complex quantum circuits in many material platforms. Among all these platforms, the Silicon-on-Insulator (SOI) platform is outstanding as it is well developed for classical applications and therefore deploys a high component density, mature fabrication techniques and compatibility with the telecom regime and the complementary metal-oxide-semiconductor (CMOS) technology. However, the lack of on-demand non-classical light sources, directly incorporated in silicon chips, forces the use of nonlinear processes to generate non-classical light states: the probabilistic nature of the emission process sets a limit in the maximally achievable experimental complexity. The use of on-demand sources will have a strong impact on the device’s scalability.
The field of photonic integrated circuits (PIC) has flourished in the past two decades, fueling numerous cutting-edge applications across sensing, networking, data interconnect, and quantum information processing. As a guiding material for PIC, Si
3N
4 has seen extensive use for its ultra-low loss, broad transparency, and diversity in implementation across both thin and thick films. Although the standard, traditional silicon dioxide (SiO
2) on silicon (Si) substrates that underpin the majority of Si
3N
4 photonics face drawbacks in the form of long-wavelength transparency limited by SiO
2, high-stress deposition for anomalous dispersion thick-film Si
3N
4, and leakage loss to the Si layer for low-confinement thin-film Si
3N
4. Featuring increased long-wavelength transparency into the mid-infrared, low-stress deposition of Si
3N
4, and a low index, this work investigates sapphire substrates as alternate hosts for Si
3N
4 photonics with greater spectral coverage and reduced fabrication complexity. This work presents a robust method of fabricating ultra-low loss photonic integrated circuits on a 500-nm-thick Si
3N
4-on-sapphire platform, exhibiting record-low losses below
0.1dB/cm. Implemented using this process are high-Q microrings with intrinsic quality factors in excess of
4.5×106 and coupled-ring photonic molecules to support nonlinear gain. Leveraging the achievable low loss and high-Q, this work further reports the first demonstration of Kerr-comb and soliton generation on the Si
3N
4-on-sapphire platform. These advances in loss, quality factor, and soliton generation on this versatile, broad-transparency platform pave the way for future work in spectroscopy and quantum-enhanced sensing across previously prohibited spectral regions for Si
3N
4 photonics with reduced fabrication complexity.
Abstract Broadband frequency-correlated photon-pair sources could enable the realization of various quantum information technologies especially WDM-QKD (wavelength division multiplexed quantum key distribution) accommodating multiple users with enhanced data transmission rates. The wide transparency window, negligible nonlinear losses, and con- siderable refractive index contrast of silicon nitride (SiN) on insulator (SiO2) platform makes it an ideal material system for designing CMOS- compatible integrated photon sources based on spontaneous four-wave mixing (SFWM). We propose simple rectangular cross-section, few- cm long SiN waveguide designs capable of generating ultra-broadband frequency-correlated photon pairs via SFWM, exceeding an octave in bandwidth spanning the visible-to-telecom wavelengths (∼700-1700nm for ∼1-μm pump) with a spectral brightness of >2.5×104 photon pairs/s/nm/mW2. Such compact sources, spanning the entire telecom spectrum (across O, E, S, C, L, and U bands) on one side and cover- ing most of the major atomic transitions used in ultracold gases and solid-state based quantum memories on the other side, could poten- tially be employed in large-scale multi channel hybrid (free space + fiber) quantum networking schemes in addition to the heralding of telecom single photons by utilizing high efficiency visible detectors.
Quantum technologies hold the promise of revolutionizing computing, communication, and sensing, and integrated photonics stands as a key enabler in this realm. Silicon nitride, with its unique combination of low loss, remarkable non-linear performance, and compatibility with existing semiconductor technologies, has emerged as a promising candidate for the implementation of quantum photonic circuits. Alternately, Lithium-Niobate-OnInsulator (LNOI), a material platform well known for its high electro-optic coefficient, has also turned out to be an attractive choice for quantum integrated circuits with the development of low-loss fabrication processes. Moreover, the integration of on-chip photon sources and superconducting nanowire single-photon detectors (SNSPDs) on these platforms has paved the for scalable quantum circuits minimizing the footprint and eliminating the need for lossy interconnects. However, the integration of these components on a single material platform is often hindered by background photons from the strong classical pump light used for processes such as spontaneous parametric down-conversion (SPDC). Here, we propose silicon-implanted SiN and LNOI waveguides as a novel material platform that acts as a passive filter at visible wavelengths while imparting negligible losses in the telecom band. The implantation process can be selectively patterned with manometer precision enabling enhanced tunability of the process. Furthermore, transmission electron microscopy (TEM) results provide a thorough understanding of the material dynamics at the atomic scale allowing accurate modelling of the mode profiles. This breakthrough advances the scalability of quantum photonic technologies where the source, filters, circuits, and detectors can be integrated on a single platform.