We have developed a novel millimetre-sized monolithic fibre-coupled rubidium saturated absorption spectroscopy laser reference suitable for quantum sensing applications. It is based on our novel MEMs vapour cell technology and bonding of optical elements to create a monolithic spectroscopy module. Our unit reproduces the signal visibility of a 70 mm long cell and is compatible with standard packaging techniques. The unit has no free-space elements that would otherwise be subject to vibration. Our reference uniquely combines the qualities of robustness, miniaturisation and signal strength providing an optimal solution for mobile quantum sensing platforms including space and aerospace.
Miniaturization of laser sources is crucial to the translation of quantum technologies from the laboratory to the real world. Typically, the lasers required for cooling and trapping of atoms and ions make up a significant footprint of the measurement system. Increasing robustness and reliability whilst removing noise sources is a key challenge whilst reducing volume. Direct generation GaN based external cavity diode lasers offer lower SWaP-C compared to traditional frequency doubled alternatives. Butterfly packaged single frequency sources operation in the blue-UV allow numerous atomic transitions including Sr, Sr+, Yb, Yb+, Mg and Ca to be targeted.
Miniaturisation of laser sources is crucial to the translation of quantum technologies from the laboratory to the real world. Typically, the lasers required for cooling and trapping of atoms and ions make up a significant footprint of the measurement system. Increasing robustness and reliability whilst removing noise sources is a key challenge whilst reducing volume. Direct generation GaN based external cavity diode lasers offer lower SWaP-C compared to traditional frequency doubled alternatives. Butterfly packaged single frequency sources operation in the blue - UV allow numerous atomic transitions including Sr, Sr+, Yt, Yb+, Mg and Ca to be targeted.
THz imaging often struggles to achieve necessary framerates for applications, but recent demonstrations show that an imaging system based upon THz-to-optical conversion in atomic vapour can provide ultrahigh speeds while retaining sensitivity with optical cameras. This atomic vapour imaging requires a multi-frequency near-IR optical pumping system, and we demonstrate a compact system to provide the stable frequencies required for conversion of 0.55 THz light to visible (green) in caesium atoms. Through the integration of distributed feedback (DFB) laser diodes and a compact extended cavity diode laser, and spectroscopy and offset locks based on open-source FPGA and Arduino code, it approaches suitability for wider industrial application.
We present a spectroscopic technique based upon optical phase-fluctuation spectroscopy for very high levels of sensitivity and specificity with application for detecting the presence of concealed explosives by detection in the vapor phase. The approach enables recent advances in deep-infrared QCL spectroscopic sources to be utilised without the need for cooled detectors and gives multi-pass Herriott-type cell performance from a highly compact form factor. The system has been evaluated in the mid-infrared using a continuous-wave optical parametric oscillator as a spectroscopic excitation source, and Ethane as a sample molecule for detection. With this setup we have demonstrated the specificity of the device by being able to resolve characteristic spectral lines of the molecule of interest against other contaminants in the sample with similar spectral response, and a noise-equivalent sensitivity of 15ppb. Sensitivity is currently limited by ambient mechanical noise and routes to minimize this are considered.
Laser absorption spectroscopy utilizes a tunable infrared source, providing the necessary selectivity, to detect the characteristic fingerprint spectral absorption of an abundant gas. In a simple embodiment such as single-pass absorption, sensitivity is limited as attenuation becomes minuscule for trace level concentrations; a problem exacerbated in the midinfrared region due to significant detector noise. Sensitivity can be improved by increasing interaction between the optical field and molecular ensemble with methods such as a multiple-pass Herriot cell or resonant cavity ring-down spectroscopy but these techniques have a substantial overhead in instrumentation. An alternative approach to this problem is Phase Fluctuation Optical Heterodyne (PFLOH) spectroscopy. Here, interferometric effects are used to detect the minute heating of the sample gas when incident laser light of the appropriate wavelength is absorbed. More specifically, by placing the absorption chamber within one arm of a Mach-Zehnder interferometer, heat-induced changes in the optical path length can be detected with great sensitivity through the resulting fringe modulation. A secondary benefit is that although excitation occurs in the infrared, its effects can be detected using visible lasers and silicon detectors, thereby obviating the need for cooled, infrared detectors. We will present our results used to detect ethane using absorption in the 3.33-3.37 μm region. The Mach-Zehnder interferometer used a Helium Neon laser for the probe laser, and a broadly tunable Optical Parametric Oscillator (OPO) for spectroscopic excitation. We have demonstrated detection levels at parts per billion with further sensitivity possible by implementing several identified improvements.
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