Highly efficient polarization-entangled photon-pair generation in lithium niobate waveguides based on bound states in continuum

Abstract

Integrated optics provides a platform for the experimental implementation of highly complex and compact circuits for practical applications as well as for advances in the fundamental science of quantum optics. The lithium niobate (LN) waveguide is an important candidate for the construction of integrated optical circuits. Based on the bound state in the continuum (BIC) in a LN waveguide, we propose an efficient way to produce polarizationentangled photon pairs. The implementation of this method is simple and does not require the polarization process needed for periodically poled LN. The generation rate of the entangled photon pairs increases linearly with the length of the waveguide. For visible light, the generation efficiency can be improved by more than five orders of magnitude with waveguides having the length of only a few millimeters, compared with the corresponding case without BICs. The phenomena can appear in a very wide spectrum range from the visible to THz regions.This study is of great significance for the development of active integrated quantum chips in various wavelength ranges.

Lithium Niobate Electro-Optic Modulation Device without an Overlay Layer Based on Bound States in the Continuum

“…Figure 2f presents the coupling efficiency of th grating structure at different optical wavelengths, indicating that the coupling effi is highest at around 1540 nm, reaching approximately 22.5%. Furthermore, since th tro-optic modulation device utilizes the electro-optic effect of the LN crystal, we s the impact of the GSG electrode on the performance of the electro-optic modulato sidering that the transmission mode of the optical field is the TM0 mode, and to ma the utilization, which is the electro-optic effect of LN, we selected the γ51 componen the electro-optic coefficient tensor (γ51 = 27 pm/V) [20]. As shown in Figure 3a,b, the field transmission curves under different applied voltages for the GSG electrode a vided, and the half-wave voltage is approximately 3.8 V. Figure 3b presents the sim results from finite element analysis software.…”

“…Bound states in the continuum (BICs) [17] are a unique optical resonance effect, ideally characterized by the absence of leaky modes. BICs have found numerous applications in photonic crystals [18], resonance enhancement [19], and optical waveguides [20]. Especially in optical waveguides, the absence of lateral leaky modes effectively reduces the complexity of optical waveguide structures and optical wave transmission losses [21].…”

Three-non Quantum Communication

“…Photon entanglement usually includes momentum and position entanglement, time and energy entanglement, frequency entanglement, polarization entanglement, phase entanglement, etc., among which photon polarization entanglement has the advantages of simple and convenient experimental control, so it is the first choice for TNQC. At present, the commonly used photon polarization entanglement sources in the laboratory are: (1) polarization entanglement generated by ultrashort pulse pumped BBO nonlinear crystal [10], (2) polarization entanglement light field generated by continuous variables [11], (3) electronically controlled polarization entanglement based on lithium niobate optical quantum chip [12], (4) allfiber photon polarization entanglement source based on spontaneous four-wave mixing process in dispersion displacement fiber [13].…”

Polarization-entangled biphoton states: a comparison of biperiod waveguides in KTP and LN

“…A recent work describes an efficient way to produce polarization-entangled photon pairs based on the bound state in the continuum (BIC) in a lithium niobate waveguide [14] without periodic poling of the waveguide, possible over a wide spectrum from visible to THz regions, with millimeter-long waveguides. An experimental study [15] addresses a hybrid approach utilizing guided-wave and bulk optics in a deterministic scheme to explore a polarizationentangled photon-pair source, demonstrating high-fidelity (96%) singlet state generation with a brightness ~ 2.9 × 10 6 pairs/(mode s mW).…”