Microwave kinetic inductance detectors (MKIDs) are increasingly used in ground-based (sub)millimeter-wave astronomy experiments. Two existing challenges to operating detector arrays remain in selecting excitation tones for each MKID where there are hundreds of resonators on the same feedline or network and that will yield the best combination of linearity and sensitivity. This is further complicated when operating arrays at ground-based telescopes, where variations in background loading from the atmosphere can induce significant shifts in MKID resonant frequencies and affect quality factors. We describe a quantitative method for optimal tuning of MKID arrays under dynamic loading conditions. We apply this new readout tuning technique to the 1.1 mm MKID array of the TolTEC camera at the Large Millimeter Telescope, where we incrementally change the readout power applied to investigate its effect. We perform in lab optical characterization of a CCAT Observatory MKID array to investigate optimal tuning under different loading conditions.
While large arrays of microwave kinetic inductance detectors (MKIDs) have been demonstrated with photon noise limited performance, imperfect frequency placement due to fabrication non-uniformity has led to resonators that collide with their frequency neighbors. Though physically yielded, the excess cross talk means that they are unusable for science applications. This would lead to reduced performance when placed on telescopes such as the CCATs FYST. However, we can use the LED trimming method developed at NIST to identify the non-uniformities, the resonator location to frequency correspondence, and then re-etch the resonators to correct them to an optimal position. This process has been demonstrated on a CCAT 280 GHz MKID array. We will show the results of the trimming of 3456 resonators on the array, and how the yield would be improved while maintaining the optical performance of the pixels. This demonstrates a path towards ideal wafer-scale MKID arrays.
We present the first full-array optical characterizations of the 280 GHz aluminum-based superconducting microwave kinetic inductance detector (MKID) arrays developed at NIST, CO, USA for the CCAT Collaboration for observing galactic ecology, Sunyaev-Zel'dovich effect, galaxy evolution, and line intensity mapping. The main advantage of aluminum MKIDs is their lower 1/f noise compared to the alternative choice of titanium-nitride (TiN) MKIDs, which would reduce systematic drifts when mapping the sky. We will present the spectral response, polarization characteristics, detector efficiency, and noise equivalent power (NEP) under the relevant conditions for these detectors. Two aluminum and one TiN MKID arrays will form the detector arrays in the 280 GHz instrument module of the Prime-Cam. First light observations are expected in 2025.
Prime-Cam, a first-generation science instrument for the Atacama-based Fred Young Submillimeter Telescope, is being built by the CCAT Collaboration to observe at millimeter and submillimeter wavelengths using kinetic inductance detectors (KIDs). Prime-Cam’s 280 GHz instrument module will deploy with two aluminum-based KID arrays and one titanium nitride-based KID array, totaling ∼10,000 detectors at the focal plane, all of which have been fabricated and are currently undergoing testing. One complication of fielding large arrays of KIDs under dynamic loading conditions is tuning the detector tone powers to maximize signal-to-noise while avoiding bifurcation due to the nonlinear kinetic inductance. For aluminum-based KIDs, this is further complicated by additional nonlinear effects which couple tone power to resonator quality factors and resonant frequencies. While both nonequilibrium quasiparticle dynamics and two-level system fluctuations have been shown to give rise to qualitatively similar distortions, modeling these effects alongside nonlinear kinetic inductance is inefficient when fitting thousands of resonators on-sky with existing models. For this reason, it is necessary to have a detailed understanding of the nonlinear effects across relevant detector loading conditions, including how they impact on on-sky noise and how to diagnose the detector’s relative performance. We present a study of the competing nonlinearities seen in Prime-Cam’s 280 GHz aluminum KIDs, with a particular emphasis on the resulting distortions to the resonator line shape and how these impact detector parameter estimation.
The Epoch of Reionization Spectrometer (EoR-Spec) is an upcoming Line Intensity Mapping (LIM) instrument designed to study the evolution of the early universe (z = 3.5 to 8) by probing the redshifted [CII] 158 μm fine-structure line from aggregates of galaxies. The [CII] emission is an excellent tracer of star formation since it is the dominant cooling line from neutral gas heated by OB star light and thus can be used to probe the reionization of the early Universe due to star formation. EoR-Spec will be deployed on Prime-Cam, a modular direct-detection receiver for the 6-meter Fred Young Submillimeter Telescope (FYST), currently under construction by CPI Vertex Antennentechnik GmbH and to be installed near the summit of Cerro Chajnantor in the Atacama Desert. This instrument features an image plane populated with more than 6500 Microwave Kinetic Inductance Detectors (MKIDs) that are illuminated by a 4-lens optical design with a cryogenic, scanning Fabry-Perot Interferometer (FPI) at the pupil of the optical system. The FPI is designed to provide a spectral resolving power of R ∼ 100 over the full spectral range of 210–420 GHz. EoR-Spec will tomographically survey the E-COSMOS and E-CDFS fields with a depth of about 4000 hours over a 5 year period. Here we give an update on EoR-Spec’s final mechanical/optical design and the current status of fabrication, characterization and testing towards first light in 2026.
Prime-Cam is a first-generation instrument designed for the Fred Young Submillimeter Telescope (FYST) in the Cerro Chajnantor Atacama Telescope (CCAT) Facility. Among the instrument modules being developed for the Prime-Cam receiver, the highest frequency 850 GHz module presents unique challenges in optical design, coupling, detection, and readout. The 850 GHz module will incorporate approximately 45,000 polarization-sensitive, lumped-element microwave kinetic inductance detectors (KIDs), which will represent the most KIDs on sky in a single instrument to date. We present the critical aspects of the detector design and discuss solutions to the challenges of efficient optical coupling and a multioctave readout band. Specifically, the designs will include a feature which reduces the inductance across a portion of the detectors by shorting pairs of inductor lines to allow the KIDs to be tuned across four distinct bands across the readout range, all with minimal impact to the responsivity of the detector. Thus, the resonators will be coarsely tuned via the inductance shorts, and finely tuned by etching away small portions of the interdigital capacitors. We further present a comparison between simulations and preliminary results of thermal responsivity. The results of this work will directly inform the design of microwave KIDs for the multi-octave readout architecture as part of the development of densely packed arrays for the Prime-Cam instrument.
We have designed a microfabricated planar absolute radiometer based on a vertically aligned carbon nanotube (VACNT) absorber and an electrical power substitution method. The radiometer is designed to operate at room temperature and to be capable of measuring laser powers up to 300 mW from 300 nm to 2300 nm with an expected expanded uncertainty of 0.06% (k = 2). The electrical power substitution capability makes the radiometer absolute and traceable to the international system (SI) of units. The new bolometer is currently under construction and will replace NIST's 50 year old detector standard for free-space CW laser power measurements. We also study the possibility of reducing background temperature sensitivity by optimizing the spectral selectivity of the VACNT forest with a photonic crystal structure.
Commercial photodiodes suffer from reflection losses and different recombination losses that reduce the collection efficiency. Recently, we realized a near-ideal silicon photodiode that exhibits an external quantum efficiency above 95% over the wavelength range of 235 – 980 nm, exceeds 100% below 300nm, and provides a very high response at incident angles of up to 70 degrees. The high quantum efficiency is reached by 1) virtually eliminating front surface reflectance by forming a “black silicon” nanostructured surface having dimensions proportional to the wavelength of light to be detected and 2) using an induced junction for signal collection instead of a conventional doped p-n junction, virtually eliminating Auger recombination at the light entry surface. This recombination prevention is especially important in ultraviolet detection since ultraviolet photons are absorbed very close to device surface, where conventional photodiodes have high doping concentration causing loss of signal, but induced junction diode is able to collect virtually all charge carriers generated. In this paper, we analyse the performance of our photodiodes under ultraviolet radiation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.