Abstract We present a physical investigation on the generation of correlated photon pairs that are broadly spaced in the ultraviolet (UV) and visible spectrum on a AlGaN/AlN integrated photonic platform which is optically transparent at these wavelengths. Using spontaneous four wave mixing (SFWM) in an AlGaN microring resonator, we show design techniques to satisfy the phase matching condition between the optical pump, the signal, and idler photon pairs, a condition which is essential and is a key hurdle when operating at short wavelength due to the strong normal dispersion of the material. Such UV-visible photon pairs are quite beneficial for interaction with qubit ions that are mostly in this wavelength range, and will enable heralding the photon-ion interaction. As a target application example, we present the systematic AlGaN microresonator design for generating signal and idler photon pairs using a blue wavelength pump, while the signal appears at the transition of ytterbium ion (171Yb+, 369.5 nm) and the idler appears in the far blue or green range. The photon pairs have minimal crosstalk to the pump power due to their broad spacing in spectral wavelength, thereby relaxing the design of on-chip integrated filters for separating pump, signal and idler.
Abstract We present a physical investigation on the generation of correlated photon pairs that are broadly spaced in the ultraviolet (UV) and visible spectrum on a AlGaN/AlN integrated photonic platform which is optically transparent at these wavelengths. Using spontaneous four wave mixing (SFWM) in an AlGaN microring resonator, we show design techniques to satisfy the phase matching condition between the optical pump, the signal, and idler photon pairs, a condition which is essential and is a key hurdle when operating at short wavelength due to the strong normal dispersion of the material. Such UV-visible photon pairs are quite beneficial for interaction with qubit ions that are mostly in this wavelength range, and will enable heralding the photon-ion interaction. As a target application example, we present the systematic AlGaN microresonator design for generating signal and idler photon pairs using a blue wavelength pump, while the signal appears at the transition of ytterbium ion (171Yb+, 369.5 nm) and the idler appears in the far blue or green range. The photon pairs have minimal crosstalk to the pump power due to their broad spacing in spectral wavelength, thereby relaxing the design of on-chip integrated filters for separating pump, signal and idler.
Nowadays, Quantum Photonics finds a number of significant applications, such as Quantum Computing and Quantum Communication. Silicon on Insulator (SOI) technology has proven its potential for the generation of correlated photon pairs through the spontaneous four wave mixing (SFWM) effect, but not in the visible wavelength range. In this invited paper we present the physical investigation and design guidelines of AlGaN microring resonators for generating photon entanglement, as induced by SFWM in the visible. The work theoretically demonstrates the possibility of realizing the on-chip generation of correlated pairs of photons within integrated microring resonators based on the AlGaN/AlN technological platform, due to its wide bandgap, crystalline structure and low losses. Furthermore, general physical features are presented by means of a parametric analysis of the biphoton flux and cross correlation as a function of the device parameters, i.e. ring radius, resonator cross section and sizes, pulley coupling. Moreover, the spectral features of the generated signal and idler photons have been analyzed as a function of the pump resonance mismatch for several Kerr coefficients and input visible “blue” pump powers. Cross correlation values around 2.3 ×104at a biphoton flux of about 9×104pairs/s and 2×103at about 2.9×106pairs/s for ring radius of 200 μm and 30 μm have been achieved, respectively, assuming a input pump power of 25 mW, while the signal is generated at wavelength of 369.5 nm and idler at 535.72 nm, for ring radius of 200 μm, and 369.5 and 457.45 nm for ring radius of 30 μm, respectively. These devices can be important for many applications, going from UV-visible spectroscopy to quantum sensing to image processing to nonlinear optics.
With the rapid development of quantum information technology, fully connected multi-user quantum entanglement distribution networks have received increasing attention. Among these, multi-wavelength quantum light sources are key devices for establishing connections between multiple users. Despite recent impressive advances, there are still challenges in increasing the wavelength number of photon pairs due to limitations in the design and fabrication of nonlinear optical devices. The potentials of silicon nitride (Si3N4) microring resonators (MRRs), as scalable platforms for multi-wavelength quantum light sources, are explored in this work. The key design parameters of the Si3N4 MRRs, including waveguide dimension, resonator dispersion, and coupling condition, are comprehensively analyzed to optimize photon-pair generation. Based on these parameters, a Si3N4 MRR with a free spectral range of 20 GHz and an average quality factor of 1.6 million is designed and fabricated. This small free spectral range can generate more channels of correlated photon pairs by using the same wavelength resources. The high-quality resonator contributes to the enhancement of the rate of generating high photon pairs , which are critical for quantum entanglement distribution. With a continuous-wave pump laser, correlated photon pairs across a wide spectral range are generated through the spontaneous four-wave mixing (SFWM). The coincidence-to-accidental ratio (CAR) measurements verify the strong quantum correlation between photon pairs, highlighting the reliability of the system for entanglement distribution. Furthermore, the generation and output characteristics of quantum-correlated photon pairs are experimentally investigated with a tunable bandpass filter. The results demonstrate that 71 wavelength-correlated photon pairs within a 25.6 nm spectral range are successively generated as shown in the Fig. A. Our results pave the way for developing the multi-wavelength quantum light sources with Si3N4 platform, thereby advancing the multi-user quantum networks.
We report the design of an innovative visible-telecom photon pair source based on counter-propagating spontaneous four wave mixing (CP-SFWM) in a silicon nitride microring resonator. Unlike previous designs, the proposed integrated source achieves automatic phase matching, eliminating the need for dispersion engineering. By employing two lasers at wavelengths of 800 nm and 1550 nm as pumps on opposite ends of the bus waveguides, the resonator generates signal and idler photons at the same wavelengths as the pumps, but propagating in opposite directions. The photon pairs are produced in high-quality factor resonant modes, exhibiting a purity of 1, a brightness of 118.70pairs⋅s−1⋅mW−2, and bandwidths of 157.9 MHz and 79.7 MHz for signal and idler photons, respectively. Our proposal outperforms previous CP-SFWM designs in terms of spectral properties of the photon pairs, emission rate, and scalability, making it an interesting alternative for the implementation of integrated photon pair sources for photonic networks.
Correlated photon-pair sources are key components for quantum computing, networking, and sensing applications. Integrated photonics has enabled chip-scale sources using nonlinear processes, producing high-rate entanglement with sub-100 microwatt power at telecom wavelengths. Many quantum systems operate in the visible or near-infrared ranges, necessitating broadband visible-telecom entangled-pair sources for connecting remote systems via entanglement swapping and teleportation. This study evaluates broadband entanglement generation through spontaneous four-wave mixing in various nonlinear integrated photonic materials, including silicon nitride, lithium niobate, aluminum gallium arsenide, indium gallium phosphide, and gallium nitride. We demonstrate how geometric dispersion engineering facilitates phase-matching for each platform and reveals unexpected results, such as robust designs to fabrication variations and a Type-1 cross-polarized phase-matching condition for III-V materials that expands the operational bandwidth. With experimentally attainable parameters, integrated photonic microresonators with optimized designs can achieve pair generation rates greater than ~1 THz/mW2.
Photonic chips with silicon nitride (Si3N4) microring resonators are well established as heralded single-photon sources, but their operation as frequency-degenerate twin-photon sources has not previously been demonstrated. Here, we realise a twin-photon source at telecommunication wavelengths in a Si3N4 ring microresonator via an inverse four-wave mixing (FWM) process, in which two photons from spectrally distinct pumps are converted into a pair of identical twin photons. The measurements show a maximum coincidence-to-accidental ratio (CAR) of 5.4±0.6. In addition, the microresonator functions as a heralded single-photon source through pump-degenerate spontaneous four-wave mixing (SFWM), exhibiting a spectral purity of P=0.67±0.05 and a heralded anti-bunching of gh(2)(0)=0.0042±0.0015. Together, these results demonstrate both photon-generation schemes on a single integrated Si3N4 platform, highlighting its potential for scalable, tailored quantum light generation.
Considerable research work is being devoted to the integration of quantum optical components on a silicon chip [1]. Many results have been achieved on the generation of quantum states of light in silicon photonic devices, but all the sources demonstrated so far need off-chip filtering stages to clean the generated photons before detection. This necessity for off-chip components hinders usability in a completely integrated platform. In this work [2] we demonstrate for the first time on-chip generation of photon pairs via a silicon microring resonator fully integrated with spectral filters for the pump on the same chip. The sample, shown in Fig. 1 a, is a reconfigurable silicon photonic integrated circuit based on Bragg reflectors and tunable ring resonators. The combination of these devices results in pump rejection by more than 95 dB in a single chip, reducing the pump intensity to less than the flux of the photon pairs generated by spontaneous four wave mixing (Fig 1 b).