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Journal of Physics Conference Series

Discussion on Spontaneous Parametric Down-conversion (SPDC) Based on Parametric Oscillator Model

Yu Peng, Minghe Wu, Sheng Chen, Zhibin Fan

Published Mar 1, 2021• 0 citations
Publisher

Abstract

Abstract In this article, we use the theory of simple harmonic motion to estimate the vibration energy of Boron atom. Subsequently we employ the parametric oscillator model to discuss photon pairs with wavelength of 710 nm. When a laser with wavelength of 355nm illuminates the barium meta-borate crystal, parametric resonance could lead to the effect of spontaneous parametric down-conversion.

DOI
10.1088/1742-6596/1838/1/012066

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•Dec 14, 2024•0 citations
Abstract In this article, we use the theory of simple harmonic motion to estimate the vibration energy of Boron atom. Subsequently we employ the parametric oscillator model to discuss photon pairs with wavelength of 710 nm. When a laser with wavelength of 355nm illuminates the barium meta-borate crystal, parametric resonance could lead to the effect of spontaneous parametric down-conversion.
There is an important class of experiments that characterize the properties of quantum mechanical systems using correlated photons, and a typical source for correlated photons is the process of Spontaneous Parametric Down Conversion (SPDC). SPDC is a quantum mechanical process in which a single “pump” photon is converted into two photons that have half the frequency and double the wavelength of the original photon. This process takes place inside a crystal with particular optical properties that allow for SPDC, and we used a uniaxial Beta Barium Borate crystal. A single photon counting module (SPCM) was used as a detector for the photons. Our goal was to characterize a 474 nanometer (nm) Diode Pumped Solid State (DPSS) laser as a possible source for SPDC correlated photons. Measurements of the DPSS laser radiation showed that it emitted photons with a wavelength of both 474 nm and 948 nm, which was expected. The SPDC photons produced by our apparatus would also have a wavelength of 948 nm, so we tested whether the down converted photons could be detected without the 948 nm signal from the DPSS laser overwhelming the SPCM. Software for determining the parameters of SPDC in a given system is available from the National Institute of Standards and Technology, and we used it to determine where we could expect to see SPDC photons. Initial measurements suggest that the system can produce SPDC photons, and we will continue to characterize the apparatus.
The frequency correlation (or decorrelation) of photon pairs is of great importance in long-range quantum communications and photonic quantum computing. We experimentally characterize a spontaneous parametric down conversion (SPDC) source, based on a β-Barium Borate (BBO) crystal cut for type-II phase matching at 1550 nm which has the capability to emit photons with positive or no spectral correlations. Our system, depicted in Fig. 1a), employs a carefully designed detection method exploiting two InGaAs detectors.
Abstract Spontaneous parametric down-conversion (SPDC) is the most widely used process for generating photon pairs entangled in various degrees of freedom such as polarization, time-energy, position-transverse momentum, and angle-orbital angular momentum (OAM). In SPDC, a pump photon interacts with a non-linear optical crystal and splits into two entangled photons called the signal and the idler photons. The SPDC process has been studied extensively in the last few decades for various pump and crystal configurations, and the entangled photon pairs produced by SPDC have been used in numerous experimental studies on quantum entanglement and entanglement-based real-world quantum-information applications. In this tutorial article, we present a thorough study of phase matching in BBO crystals for spontaneous parametric down-conversion and thereby also investigate the generation of entangled photons in such crystals. First, we present a theoretical derivation of two-photon wavefunction produced by SPDC in the frequency and transverse momentum bases. We then discuss in detail the effects due to various crystal and pump parameters including the length of the crystal, the angle between the optic axis and the pump propagation direction, the pump incidence angle on the crystal surface, the refraction at the crystal surfaces, and the pump propagation direction inside the crystal. These effects are extremely relevant in experimental situations. We then present our numerical and experimental results in order to illustrate how various experimental parameters affect the phase matching and thus the generation of entangled photons. Finally, using the two-photon wavefunction in the transverse wave-vector basis, we show how to derive the two-photon wavefunction in the OAM basis and thereby calculate the two-photon angular Schmidt spectrum. We expect this article to be useful for researchers working in various capacities with entangled photons generated by SPDC in BBO crystals.
Spontaneous parametric upconversion (SPUC) and spontaneous parametric downconversion (SPDC) have been observed in the β-barium borate (BBO) crystal, and their mechanisms are experimentally and theoretically investigated. SPUC, tuned from 530 to 600 nm with a FWHM of about 25 nm, can be attributed to the sum frequency between the quantum noise and the fundamental laser pulse in the type II phase matching condition (e+o→e). SPDC, tuned from 480 to 520 nm with a FWHM of about 15 nm, can be attributed to the difference frequency between the quantum noise and the fundamental laser pulse in the type I phase matching condition (e→o+o).
Spontaneous Parametric Down-Conversion (SPDC) is a cornerstone phenomenon in nonlinear optics, where an incident high-energy photon is transformed into a pair of lower-energy photons. This quantum process serves as a fundamental tool for generating entangled photon pairs, heralded single photons, and squeezed light, making it indispensable in the realms of quantum communication, quantum computing, and precision metrology. In this paper, we present a comprehensive study on the theoretical foundations and practical realization of an SPDC experimental setup, developed for the first time at the Photonics Research Laboratory at Amirkabir University of Technology. Our setup features a self-grown potassium dihydrogen phosphate (KDP) nonlinear crystal, illuminated by a 450 nm blue laser, to achieve parametric down-conversion into infrared photon pairs at 900 nm. By integrating a custom-designed transimpedance amplifier with a BPX65 photodiode, we have successfully amplified and detected the weak SPDC signal, demonstrating the feasibility of achieving high sensitivity with low-cost, widely available components. The experimental results align closely with theoretical predictions, showcasing the effectiveness of the system in detecting photon pairs with minimal resources. This study underscores the accessibility and scalability of SPDC technology, providing a blueprint for constructing versatile quantum optics experiments in resource-limited settings. By bridging the gap between theoretical insight and experimental realization, we aim to inspire further exploration of SPDC's potential in both foundational research and practical applications, laying the groundwork for future innovations in quantum technologies.