Phase shifters are a key component of nulling interferometry, one of the potential routes to enabling the measurement of faint exoplanet spectra. Here, three different achromatic phase shifters are evaluated experimentally in the mid-infrared, where such nulling interferometers may someday operate. The methods evaluated include the use of dispersive glasses, a through-focus field inversion, and field reversals on reflection from antisymmetric flat-mirror periscopes. All three approaches yielded deep, broadband, mid-infrared nulls, but the deepest broadband nulls were obtained with the periscope architecture. In the periscope system, average null depths of 4 X 10~(-5) were obtained with a 25percent bandwidth, and 2 X 10~(-5) with a 20percent bandwidth, at a central wavelength of 9.5 (mu)m. The best short term nulls at 20percent bandwidth were approximately 9 X 10~(-6), in line with error budget predictions and the limits of the current generation of hardware.
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机译：相移器是调零干涉法的关键组成部分，这是实现微弱系外行星光谱测量的潜在途径之一。在这里，在中红外实验上评估了三种不同的消色差移相器，在这种情况下，这种消零干涉仪可能有朝一日可以工作。评估的方法包括使用色散眼镜，通过焦点的场反转以及在非对称平面镜潜望镜反射时的场反转。这三种方法都产生了深的宽带中红外零点，但是最深的宽带零点是通过潜望镜架构获得的。在潜望镜系统中，在中心波长9.5 µm处，平均零深度为25％的带宽为4 X 10〜（-5），带宽为20％的带宽为2 X 10〜（-5）。带宽误差为20％时，最佳短期零点约为9 X 10〜（-6），这与错误预算预测和当前硬件的限制相一致。
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