High efficient beam shaping optics for compact THz imager

Miniaturized THz sources with sufficient output power, uncooled 2-dimensional detector arrays for real time data acquisition, and high efficient THz optics are fundamental components for handheld THz illumination and imaging systems. Such THz imagers are especially interesting for law enforcement agencies if they can be used in standoff operation to detect concealed weapons and to reliably distinguish them from commonly carried items such as cell phones, pencils, and watches. We present a concept for an efficient and compact THz imager operating at 480 µm wavelength. Transmission losses from the illumination optics as a result of Fresnel reflection and absorption are reduced by integrating several optical functions within a single optical element that possesses a subwavelength antireflection structures. The design of a beam shaping element is optimized with respect to manufacturing errors and material absorption. We present a compact reflective zoom objective lens designed with conventional raytracing software under consideration of wave optical boundary conditions. Beam shaping elements fabricated by means of ultra precision micromachining are experimentally demonstrated.