The kilopixel array pathfinder project (KAPPa), a 16-pixel integrated heterodyne focal plane array: Characterization of the single pixel prototype

We report on the laboratory testing of KAPPa, a 16-pixel proof-of-concept array to enable the creation THz imaging spectrometer with ∼1000 pixels. Creating an array an order of magnitude larger than the existing state of the art of 64 pixels requires a simple and robust design as well as improvements to mixer selection, testing, and assembly. Our testing employs a single pixel test bench where a novel 2D array architecture is tested. The minimum size of the footprint is dictated by the diameter of the drilled feedhorn aperture. In the adjoining detector block, a 6mm × 6mm footprint houses the SIS mixer, LNA, matching and bias networks, and permanent magnet. We present an initial characterization of the single pixel prototype using a computer controlled test bench to determine Y-factors for a parameter space of LO power, LO frequency, IF bandwidth, magnet field strength, and SIS bias voltage. To reduce the need to replace poorly preforming pixels that are already mounted in a large format array, we show techniques to improve SIS mixer selection prior to mounting in the detector block. The 2D integrated 16-pixel array design has been evolved as we investigate the properties of the single pixel prototype. Carful design of the prototype has allowed for rapid translation of single pixel design improvements to be easily incorporated into the 16-pixel model.