With increasing array size, it is increasingly important to control stray
radiation inside the detector chips themselves. We demonstrate this effect with
focal plane arrays of absorber coupled Lumped Element microwave Kinetic
Inductance Detectors (LEKIDs) and lens-antenna coupled distributed quarter
wavelength Microwave Kinetic Inductance Detectors (MKIDs). In these arrays the
response from a point source at the pixel position is at a similar level to the
stray response integrated over the entire chip area. For the antenna coupled
arrays, we show that this effect can be suppressed by incorporating an on-chip
stray light absorber. A similar method should be possible with the LEKID array,
especially when they are lens coupled.Comment: arXiv admin note: substantial text overlap with arXiv:1707.0214
