[ANGLÈS] We describe experimental results on a novel optical filter based on the FADOF (Faraday Anomalous Dispersion Optical Filter) principle, and its application to production of atom-resonant entangled photon pairs at the D_1 line of atomic rubidium. The filter uses natural-abundance rubidium vapor in an axial magnetic field to produce Faraday rotation up to pi/2 in the transparent regions adjacent to Rb absorption features. When the Faraday rotator is placed between crossed polarizers, the resulting system shows a 400 MHz FWHM transmission window with 70% peak transmission, and out-of-band rejection up to 10^5. Using this device we demonstrate selection of atom-resonant photon pairs from a type-I cavity-enhanced spontaneous parametric downconversion source (CESPDC). We also present an exact calculation of the time correlations, i.e., the g^(2)(T), of photons from the CESPDC. This is the first time fully-indistinguishable atom-resonant photon pairs have been observed.
[ANGLÈS] We describe experimental results on a novel optical filter based on the FADOF (Faraday Anomalous Dispersion Optical Filter) principle, and its application to production of atom-resonant entangled photon pairs at the D_1 line of atomic rubidium. The filter uses natural-abundance rubidium vapor in an axial magnetic field to produce Faraday rotation up to pi/2 in the transparent regions adjacent to Rb absorption features. When the Faraday rotator is placed between crossed polarizers, the resulting system shows a 400 MHz FWHM transmission window with 70% peak transmission, and out-of-band rejection up to 10^5. Using this device we demonstrate selection of atom-resonant photon pairs from a type-I cavity-enhanced spontaneous parametric downconversion source (CESPDC). We also present an exact calculation of the time correlations, i.e., the g^(2)(T), of photons from the CESPDC. This is the first time fully-indistinguishable atom-resonant photon pairs have been observed.
[ANGLÈS] We describe experimental results on a novel optical filter based on the FADOF (Faraday Anomalous Dispersion Optical Filter) principle, and its application to production of atom-resonant entangled photon pairs at the D_1 line of atomic rubidium. The filter uses natural-abundance rubidium vapor in an axial magnetic field to produce Faraday rotation up to pi/2 in the transparent regions adjacent to Rb absorption features. When the Faraday rotator is placed between crossed polarizers, the resulting system shows a 400 MHz FWHM transmission window with 70% peak transmission, and out-of-band rejection up to 10^5. Using this device we demonstrate selection of atom-resonant photon pairs from a type-I cavity-enhanced spontaneous parametric downconversion source (CESPDC). We also present an exact calculation of the time correlations, i.e., the g^(2)(T), of photons from the CESPDC. This is the first time fully-indistinguishable atom-resonant photon pairs have been observed.
To obtain the weak signal light detection from the high background noise,a study on ultra-narrow bandwidth Faraday anomalous dispersion optical filter(FADOF) at the 87Rb D1 line,5S1/2F=2→5P1/2 F′=1transmission(795 nm) is demonstrated experimentally.A sample cell filled with Rubidium atoms in which the proportion of 87Rb is greater than that of the nature rubidium is placed in a homogeneous magnetic field between two crossed Glan-Thompson polarizers.The incident probe light goes through the sample cell,and interacts with the atoms.Because of the Faraday rotation,the function of the filter can be realized.When the experiment condition changed,the result of transmission spectrum changed accordingly.With the temperature rising from 340 K to 360 K,the variation of the transmission spectrum is recorded particularly.And the reason for the variation is analyzed carefully.At a proper temperature and magnetic field,a transmission spectrum narrowed to ~220 MHz is obtained,and the peak transmission is about 48%.The performance of the87Rb D1 line is better than that of the 85Rb.
This thesis describes experimental work to generate and characterise single photons and photon pairs, with frequency content suitable for controlled interaction with cold rubidium atoms. We describe a photon-pair source, consisting of a cavity-enhanced spontaneous parametric down-conversion (CE-SPDC) system, followed by Fabry-Perot interferometer (FPI) filters, that produces narrowband photon pairs that have a bandwidth of ˜ 5 MHz. Both photons from the photon-pair source are matched to the D1 line in atomic rubidium. Type-II phase matching, a tuneable-birefringence resonator and MHz-resolution pump tuning are used to achieve independent frequency control over each photon in the pair with MHz precision, enabling them to excite different hyperfine transitions in rubidium. We have designed and implemented tuneable FPI, also with ~ MHz control over their resonance frequencies, to isolate a single frequency mode-pair from the CE-SPDC source. The filters have ~ 90 % on-resonance transmission and extinguish unwanted frequency components by over 20 dB. The thesis includes predictions of the two-photon spectra at the output of the CE-SPDC source, and also after the filters, based on existing theoretical models of CE-SPDC. We measure the two-photon linewidth, the number of modes in an emission cluster and the spacing between clusters, the second-order cross-correlation and heralded autocorrelation functions, and find good agreement with predictions. We demonstrate independent tuneability of the signal and idler frequencies by atomic absorption spectroscopy with the filtered CE-SPDC output as the light source. We also report a technique to resolve narrow frequency differences between photons with a high frequency resolution. The technique, which we call autoheterodyne characterisation, can measure the photon-pair joint spectra by detecting the time-correlation beat-note when nondegenerate photon-pairs interfere at a beamsplitter. It implements a temporal analog of the Ghosh-Mandel effect with one photon counter and a time-resolved Hong-Ou-Mandel interference with two. We provide a complete theoretical description of the process and show how the distribution of sum and difference frequencies in the photon-pair spectrum can be obtained from measured correlation functions. Through a power spectral analysis of the correlation measurements, the strengths, linewidths and relative frequencies of the spectral content in the two-photon state is obtained. With this, it is possible to quantify the contribution of undesired frequency modes when a single mode output is required. We analyse the application of this technique to photon-pairs that are produced by narrowband pumping and are strongly anti-correlated in frequency, and to pairs with reduced frequency correlations produced by broadband pumping. Experimentally, we demonstrate this technique using photon-pairs from the filtered CE-SPDC source described in the previous paragraph, that have a frequency separation of ~ 200 MHz. From the results, we quantify the performance of the filters and verify the accuracy of our model for the two-photon joint spectra from this source. Esta tesis describe trabajos de laboratorio, que tienen como objetivo generar y caracterizar fotones individuales y pares de fotones, aptos para interactuar con átomos fríos. Para este fin, el espectro conjunto o contenido en frecuencia de los fotones pares es de particular interés. El átomo considerado en la tesis es rubidio. Primero describimos una fuente de pares de fotones, basada en el proceso de conversión paramétrica descendente espontánea (spontaneous parametric down-conversion, SPDC por sus siglas en inglés), aumentada por un resonador óptico (cavity-enhanced SPDC, o CE-SPDC). Este proceso genera pares de fotones de banda estrecha, con un ancho de banda de ≈5MHz Ambos fotones producidos por la fuente concuerdan en frecuencia con la línea D1 del rubidio atómico. La coincidencia de fases (phase matching) de tipo dos, un resonador de birrefringencia ajustable, y una bomba de frecuencia ajustable con resolución de unos MHz, son usados para conseguir control independiente sobre la frecuencia de cada fotón del par, con precisión de MHz, permitiendo que exciten diferentes transiciones hiperfinas del rubidio. Diseñamos e implementamos filtros Fabry-Perot sintonizables, también con una precisión de control de _ MHz en su frecuencia de resonancia. Con dichos filtros, demostramos la selección de pares de fotones que provienen, cada uno, de un solo modo del resonador, y por lo tanto con un ancho de banda definido por dicho modo. Los filtros tienen una transmisión del .̴ 90% en resonancia y extinguen componentes fuera de banda en 20 dB. Calculamos el espectro conjunto de los pares de fotones producidos, tanto a la salida de la fuente, como después de lo filtros, a base de modelos teóricos de CE-SPDC. Medimos el ancho de banda de ambos fotones, el número de modos de emisión en un cúmulo, el espaciado espectral entre grupos de modos cuasi-resonantes, y las funciones de correlación cruzada de segundo orden y de autocorrelación anunciada, y resultan estar en buen acuerdo con las predicciones. Demostramos un ajuste independiente de la frecuencia del fotón signal y del fotón idler mediante espectroscopía de absorción con la salida del CE-SPDC como fuente de luz. También presentamos una técnica para distinguir diferencias estrechas de frecuencia entre fotones con una gran resolución en frecuencia. Esta técnica, a la que llamamos caracterización autoheterodina, permite medir el espectro conjunto de un par de fotones mediante la detección de la correlación en tiempo de su batido (beat-note) cuando el par de fotones no-degenerados interfiere en un divisor de haz. Esta técnica implementa un análogo temporal al efecto Ghosh-Mandel con un contador de fotones y una interferencia Hong-Ou-Mandel con resolución temporal con dos. Proporcionamos una descripción teórica completa del proceso y mostramos como la distribución de la suma y diferencia de frecuencias en el espectro del par de fotones puede obtenerse a partir de las medidas de las funciones de correlación. Mediante el análisis del espectro de las medidas de correlación, se obtienen las amplitudes, anchos de línea y frecuencias relativas del contenido espectral del estado conjunto de los dos fotones. Con esto, es posible cuantificar la presencia de modos indeseados de frecuencia cuando se requiere una salida monomodo. Analizamos la aplicación de esta técnica a pares de fotones producidos por bombeo de banda estrecha y fuertemente anti-correlacionados en frecuencia, y a pares con correlaciones de frecuencia reducidas producidos por bombeo de banda ancha. Experimentalmente, demostramos esta técnica usando pares de fotones generados por la fuente descrita en el párrafo anterior, con una separación en frecuencia de .̴ 200MHz. A partir de los resultados, cuantificamos el desempeño de los filtros y verificamos la exactitud de nuestro modelo para el espectro conjunto de los dos fotones provenientes de la fuente CE-SPDC con filtros.
We demonstrate atomic filtering of frequency-degenerate photon pairs from a sub-threshold optical parametric oscillator (OPO). The filter, a modified Faraday anomalous dispersion optical filter (FADOF), achieves 70% peak transmission simultaneous with 57 dB out-of-band rejection and a 445 MHz transmission bandwidth. When applied to the OPO output, only the degenerate mode, containing one-mode squeezed vacuum, falls in the filter pass-band; all other modes are strongly suppressed. The high transmission preserves non-classical continuous-variable features, e.g. squeezing or non-gaussianity, while the high spectral purity allows reliable discrete-variable detection and heralding. Correlation and atomic absorption measurements indicate a spectral purity of 96% for the individual photons, and 98% for the photon pairs. These capabilities will enable generation of atom-resonant hybrid states, e.g. "Schrödinger kittens" obtained by photon subtraction from squeezed vacuum, making these exotic states available for quantum networking and atomic quantum metrology applications.
We report on a 795 nm atomic filter consisting of a stimulated Raman gain amplifier together with normal Faraday anomalous dispersion optical filtering (FADOF) at the rubidium D1 line. The filter is operated with a single transmission peak. The gain of the filter's transmission light signal is enhanced up to 85-fold compared to case operating without a stimulated Raman transition. Based on atomic coherence, the filter's minimum transmission bandwidth is less than 22 MHz. In each filtering channel, the signal light's frequency can be tuned by changing the detuning of the coupling light. Such a filter with stimulated Raman gain is more efficient in extracting weak signals in the presence of a strong light background compared with the normal FADOF. This expands the range of potential applications in optical communications and lidar technology. This filtering method can also be extended to the lines of other atoms.