a b s t r a c tWe present a computer program and underlying model to calculate the electric susceptibility of a gas, which is essential to predict its absorptive and dispersive properties. Our program focuses on alkali-metal vapours where we use a matrix representation of the atomic Hamiltonian in the completely uncoupled basis in order to calculate transition frequencies and strengths. The program calculates various spectra for a weak-probe laser beam in an atomic medium with an applied axial magnetic field. This allows many optical devices to be designed, such as Faraday rotators/filters, optical isolators and circular polarisation filters. Fitting routines are also provided with the program which allows the user to perform optical metrology by fitting to experimental data. Program summary Program title: ElecSus Catalogue identifier: AEVD_v1_0Program summary URL:
We demonstrate an atomic bandpass optical filter with an equivalent noise bandwidth less than 1 GHz using the D1 line in a cesium vapor. We use the ElecSus computer program to find optimal experimental parameters, and find that for important quantities the cesium D1 line clearly outperforms other alkali metals on either D-lines. The filter simultaneously achieves a peak transmission of 77%, a passband of 310 MHz and an equivalent noise bandwidth of 0.96 GHz, for a magnetic field of 45.3 gauss and a temperature of 68.0• C. Experimentally, the prediction from the model is verified. The experiment and theoretical predictions show excellent agreement.The Faraday effect in atomic media has come to be used for a wide range of applications, including creating macroscopic entanglement [1], GHz bandwidth measurements [2], non-destructive imaging [3], magnetometry [4], off-resonance laser frequency stabilization [5,6], and creating an optical isolator [7].Another application of increasing interest is utilizing the Faraday effect to create ultra-narrow bandwidth optical filters [8], of the order of a GHz width. These atomic Faraday filters are imaging filters [9] with a large field of view [10], and can be engineered to be low loss at the signal frequency [11]. This makes them the filter of choice for many applications, for example, they are used in atmospheric lidar [11][12][13][14] [9,24,25,[31][32][33][34], potassium [18,35,36], rubidium [37][38][39], and cesium [23,40,41]. A Faraday filter on the cesium D 1 line (894 nm) could be useful for quantum optics experiments which utilize the the Cs D 1 line [42], and could aid filtering degenerate photon-pairs at 894 nm in a similar way to that shown for 795 nm [21].In this letter we demonstrate the technique of using computer optimization to find optimal working parameters for a Faraday filter. Using this technique we find that a Faraday filter working at the Cs D 1 line has superior performance when compared to similar linear Faraday filters working with different elements and/or transitions. Experimentally, we verify the prediction of the model, and achieve a linear Faraday filter with the best performance to date.
There is much interest in employing terahertz (THz) radiation across a range of imaging applications, but so far, technologies have struggled to achieve the necessary frame rates. Here, we demonstrate a THz imaging system based upon efficient THz-to-optical conversion in atomic vapor, where full-field images can be collected at ultrahigh speeds using conventional optical camera technology. For a 0.55-THz field, we show an effective 1-cm 2 sensor with near diffraction-limited spatial resolution and a minimum detectable power of ð190 AE 30Þ fW s −1=2 per ð40 × 40Þ μm 2 pixel capable of video capture at 3000 frames per second. This combination of speed and sensitivity represents a step change in the state of the art of THz imaging and will likely lead to its uptake in wider industrial settings.
We experimentally demonstrate the heralded generation of bichromatic single photons from an atomic collective spin excitation (CSE). The photon arrival times display collective quantum beats, a novel interference effect resulting from the relative motion of atoms in the CSE. A combination of velocity-selective excitation with strong laser dressing and the addition of a magnetic field allows for exquisite control of this collective beat phenomenon. The present experiment uses a diamond scheme with near-IR photons that can be extended to include telecommunications wavelengths or modified to allow storage and retrieval in an inverted-Y scheme.
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