Résultats de recherche pour « Spontaneous Parametric Down-Conversion (SPDC) »

SPDC is a process commonly used in quantum optics to produce entangled photon pairs. It typically occurs in a nonlinear optical material (such as a beta barium borate (BBO) crystal), where a single high-energy photon (like a laser photon) interacts with the crystal and is down-converted into two lower-energy photons. These photons are often entangled in terms of properties like polarization, momentum, or phase.We also determine the probability of their entanglement and correlated behavior.

The generation of entangled photon pairs through spontaneous parametric down conversion (SPDC) is widely used and considered one of the key entanglement generation techniques in quantum optics. The quality of the entanglement produced depends significantly on the physical properties of the nonlinear crystal employed in the SPDC process. In this study, we investigate the influence of the crystal parameters such as phase matching configurations on the degree of entanglement. Our results demonstrate the importance of crystal selection for achieving highly entangled photon sources, which are essential for applications in quantum communication and quantum information.

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.

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.

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.

We have used photon pair correlations generated via spontaneous parametric downconversion (SPDC) to measure the fluorescence lifetime of the organic dye rhodamine 6 G, demonstrating that fluorescence lifetime measurements can be achieved using a continuous wave (CW) laser, without pulsed or modulated lasers. Our entangled photon method, quantum fluorescence lifetime (Q-FL) measurements, uses one photon to excite fluorescence and the resulting fluorescence photon is timed and referenced to the arrival time of the other entangled photon. Thus, we can exploit the short timescale of photon pair correlations to conduct experiments that are typically carried out with pulsed lasers and we show that the inherent timing of the photons is fast enough to resolve the nanosecond scale fluorescence lifetime of the sample. This measurement paves the way towards using the time correlations of entangled photons for fluorescence imaging; capitalizing on the presence of fast, sub-100 ps correlations that have not been demonstrated classically.

This thesis studies different designs of optical parametric oscillators as sources of atom-resonant quantum light resonant with the rubidium D1 line.We analyze the mode structure and filtering techniques in a conventional OPO based on a crystal inside a ring cavity. We also present a first fully-tunable design of a monolithic doubly-resonant OPO. The first part presents the study of a multimode optical parametric oscillator from the theoretical point of view, calculating a multimode Bogoliubov transformation and a time-domain intensity correlation function. Next, we experimentally observe signatures of multi- and singlemode OPO output in pairwise time-of-arrival correlations of the generated photons, achieved thanks to Faraday anomalous dispersion filtering technique based on optical properties of atomic vapor in magnetic field. The second, more extensive part of the thesis features the study of a new design of the OPO, a monolithic cavity (crystal polished and coated so that it forms a cavity) that allows full tunability even in a multiply resonant configuration. The architecture we propose combines the advantages of a conventional ring cavity based OPO, with robustness, lowmaintenance, compactness and stability characteristic of monolithic systems. The tunability of the doubly-resonant monolithic OPO is realized by maintaining different sections of the crystal at different temperatures and pressing it with a piezoelectric actuator. The tuning method is tested when the system is employed as a second harmonic generator. In addition, we describe a new nonlinear effect that comes into play when the monolithic cavity is pumped with 795 nm light. The phenomenon,that we call a photo-Kerr effect causes the cavity behavior resembling optical bistability due to Kerr nonlinearity, but with the magnitude (Kerr coefficient) dependent on the long-time average of intra-cavity power. The model we propose agrees well with the experimental results. The effect simplifies greatly the cavity stabilization, causing the cavity to maintain itself close to resonance even as the laser wavelength is changed by more than a free spectral range. The thesis concludes by studying the suitability of the monolithic cavity with the photo-Kerr effect for squeezed light generation. We test the monolithic cavity as an OPO and demonstrate 1.6 dB of quadrature squeezing via homodyne detection. Esta tesis estudia diferentes diseños de osciladores paramétricos (OPO, por sus signas en inglés) como fuentes de luz cuántica resonante con la línea D1 de átomos de rubidio. Analizamos la estructura de modos y las técnicas de filtrado en un oscilador paramétrico convencional basado en un cristal no lineal dentro de una cavidad. También presentamos el primer diseño de un OPO monolítico con dos resonancias con frecuencias ajustables. La primera parte de la tesis presenta el estudio de un oscilador paramétrico multimodo desde el punto de vista teórico, calculando una transformación de Bogoliubov multimodo y una función de correlación temporal de intensidad. A continuación, se observan experimentalmente las señales de la emisión de OPO multimodo o de un solo modo en correlaciones de tiempo de llegada de pares de los fotones generados, obtenidos gracias a la técnica de filtración de dispersión anómala de Faraday basada en las propiedades ópticas del vapor atómico en campo magnético. La segunda y más extensa parte de la tesis presenta el estudio de un nuevo diseño del OPO: una cavidad monolítica (cristal pulido y recubierto de tal manera que forma una cavidad) que permite ajustar las frecuencias de resonancia, incluso en una configuración multi-resonante. La arquitectura que proponemos combina las ventajas de una OPO convencional basada en una cavidad afuera de cristal, con robustez, bajo mantenimiento, compacidad y estabilidad característica de los sistemas monolíticos. La ajustibilidad del OPO monolítico con doble resonancia se realiza manteniendo diferentes secciones del cristal a diferentes temperaturas y presionándolo con un element piezoeléctrico. El método de afinación es sometido a prueba cuando el sistema se emplea como generador de segundo armónico. Además, describimos un nuevo efecto no lineal que entra en juego cuando la cavidad monolítica se bombea con luz 795 nm. El fenómeno que denominamos efecto photo-Kerr provoca que el comportamiento de la cavidad se asemeje a la biestabilidad óptica debido a la no linealidad de Kerr, pero con la magnitud (coeficiente de Kerr) dependiente del promedio de tiempo largo de la potencia de la luz dentro de la cavidad. El modelo numérico que proponemos coincide con los resultados experimentales. El efecto simplifica en gran medida la estabilización de la cavidad, hacienda que ésta se mantenga cerca de la resonancia incluso cuando la longitud de onda del láser cambia en más de la distancia entre dos resonancias consecutivas. La tesis concluye estudiando la idoneidad de la cavidad monolítica con el efecto photo-Kerr para la generación de luz comprimida. Se emplea la cavidad monolítica como oscilador paramétrico, obteniando luz comprimida y se demuestra 1.6 dB de squeezing mediante detección homodina.