Micro-Spec: an ultracompact, high-sensitivity spectrometer for far-infrared and submillimeter astronomy (original) (raw)
Related papers
Acta Astronautica, 2019
Micro-Spec is a direct-detection spectrometer which integrates all the components of a diffraction-grating spectrometer onto a 10-cm 2 chip through the use of superconducting microstrip transmission lines on a singlecrystal silicon substrate. The second generation of Micro-Spec is being designed to operate with a spectral resolution of at least 512 in the far-infrared and submillimeter (420-540 GHz, 714-555 μm) wavelength range, a band of interest for NASA's experiment for cryogenic large-aperture intensity mapping called EXCLAIM. EXCLAIM will be a balloon-borne telescope that is being designed to map the emission of redshifted carbon monoxide and singly-ionized carbon lines over a redshift range z 0 3.5 < < and it will be the first demonstration of the Micro-Spec technology in a space-like environment. This work reviews the status of the Micro-Spec design for the EXCLAIM telescope, with emphasis on the spectrometer's two-dimensional diffractive region, through which light of different wavelengths is focused on kinetic inductance detectors along the instrument focal plane. An optimization process is used to generate a geometrical configuration of the diffractive region that satisfies specific requirements on size, operating spectral range and performance. An initial optical design optimized for EXCLAIM is presented in terms of geometric layout, spectral purity and efficiency.
μ-Spec : An Efficient Compact Integrated Spectrometer for Submillimeter Astrophysics
2015
We are developing an extremely compact (~10 cm) sub-millimeter spectrometer instrument called μ-Spec for application on a space or balloon telescope. We use low-loss superconducting microstrip transmission lines on 0.45 μm singlecrystal silicon to produce a synthetic grating with spectral resolution and efficiency only limited by the intrinsic loss of Si. The photon detectors are superconducting micro-resonator MKIDs that are produced by patterning a layer of superconducting thin film such as Al on Si. We have built a prototype version of μ-Spec with resolution R=64 that operates in the 400—600 GHz band. We have measured the spectral response of the channels and obtained good agreement with the expected resolution of 64 and band center frequency locations within ±1 GHz of design values. We have also designed and characterized Al resonators and obtained quasi-particle lifetimes of order ~ 1ms and internal quality factors of order ~ 2 million, which are necessary for producing ultra-s...
Journal of Low Temperature Physics, 2018
Micro-Spec (µ-Spec) is a direct-detection spectrometer which integrates all the components of a diffraction-grating spectrometer onto a ∼ 10-cm 2 chip through the use of superconducting microstrip transmission lines on a single-crystal silicon substrate. A second-generation µ-Spec is being designed to operate with a spectral resolution of 512 in the submillimeter (500-1000 µm, 300-600 GHz) wavelength range, a band of interest for several spectroscopic applications in astrophysics. Highaltitude balloon missions would provide the first test bed to demonstrate the µ-Spec technology in a space-like environment and would be an economically viable venue for multiple observation campaigns. This work reports on the current status of the instrument design and will provide a brief overview of each instrument subsystem. Particular emphasis will be given to the design of the spectrometer's two-dimensional diffractive region, through which the light of different wavelengths is focused on the detectors along the focal plane. An optimization process is employed to generate geometrical configurations of the diffractive region that satisfy specific requirements on spectrometer size, operating spectral range, and performance. An optical design optimized for balloon missions will be presented in terms of geometric layout, spectral purity, and efficiency.
Micro-Spec: an integrated direct-detection spectrometer for far-infrared space telescopes
Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 2014
The far-infrared and submillimeter portions of the electromagnetic spectrum provide a unique view of the astrophysical processes present in the early universe. Our ability to fully explore this rich spectral region has been limited, however, by the size and cost of the cryogenic spectrometers required to carry out such measurements. Micro-Spec (µ-Spec) is a high-sensitivity, direct-detection spectrometer concept working in the 450-1000 µm wavelength range which will enable a wide range of flight missions that would otherwise be challenging due to the large size of current instruments with the required spectral resolution and sensitivity. The spectrometer design utilizes two internal antenna arrays, one for transmitting and one for receiving, superconducting microstrip transmission lines for power division and phase delay, and an array of microwave kinetic inductance detectors (MKIDs) to achieve these goals. The instrument will be integrated on a ∼ 10 cm 2 silicon chip and can therefore become an important capability under the low background conditions accessible via space and high-altitude borne platforms. In this paper, an optical design methodology for µ-Spec is presented, with particular attention given to its two-dimensional diffractive region, where the light of different wavelengths is focused on the different detectors. The method is based on the maximization of the instrument resolving power and minimization of the RMS phase error on the instrument focal plane. This two-step optimization can generate geometrical configurations given specific requirements on spectrometer size, operating spectral range and performance. Two point designs with resolving power of 260 and 520 and an RMS phase error less than ∼ 0.004 radians were developed for initial demonstration and will be the basis of future instruments with resolving power up to about 1200.
Development of a broadband submillimeter grating spectrometer
Advanced Technology MMW, Radio, and Terahertz Telescopes, 1998
One of the central issues in astronomy is the formation and evolution of galaxies at large redshifts. Submillimeter observations are essential to understanding these processes. One of the best prospects for high redshift submillimeter observations is the study of the Cii 158 m ne-structure line, which carries about 0.2% of the total luminosity of nearby starburst galaxies. However, current heterodyne receivers at submillimeter observatories have insu cient bandwidth to detect the full extent of highly broadened emission lines. We are developing a broadband grating spectrometer for the Caltech Submillimeter Observatory with a total bandwidth of 3400 km/s and a velocity resolution of 200 km/s. The detectors will be a linear array of 32 close-packed monolithic silicon bolometers developed at NASA's Goddard Space Flight Center. In order to achieve background-limited sensitivity, the bolometers will be cooled to 100mK by an adiabatic demagnetization refrigerator. The spectrometer optics will consist of a tunable cryogenic immersion grating using broadband lters as order sorters. The spectrometer will be optimized to operate in the 350 m and 450 m atmospheric windows. Calculations of the sensitivity of the spectrometer reveal that an ultraluminous infrared galaxy of 10 12 L at a redshift of z = 1 would be detectable at the 3 level in the Cii line with 20 minutes of integration time.
Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave
The current state of far-infrared astronomy drives the need to develop compact, sensitive spectrometers for future space and ground-based instruments. Here we present details of the µ-Spec spectrometers currently in development for the far-infrared balloon mission EXCLAIM. The spectrometers are designed to cover the 555-714 µm range with a resolution of R = λ/∆λ = 512 at the 638 µm band center. The spectrometer design incorporates a Rowland grating spectrometer implemented in a parallel plate waveguide on a low-loss single-crystal Si chip, employing Nb microstrip planar transmission lines and thin-film Al kinetic inductance detectors (KIDs). The EXCLAIM µ-Spec design is an advancement upon a successful R = 64 µ-Spec prototype, and can be considered a sub-mm superconducting photonic integrated circuit (PIC) that combines spectral dispersion and detection. The design operates in a single M =2 grating order, allowing one spectrometer to cover the full EXCLAIM band without requiring a multi-order focal plane. The EXCLAIM instrument will fly six spectrometers, which are fabricated on a single 150 mm diameter Si wafer. Fabrication involves a flipwafer-bonding process with patterning of the superconducting layers on both sides of the Si dielectric. The spectrometers are designed to operate at 100 mK, and will include 355 Al KID detectors targeting a goal of NEP ∼8 × 10 −19 W/ √ Hz. We summarize the design, fabrication, and ongoing development of these µ-Spec spectrometers for EXCLAIM.
Optical design for the Submillimeter and Far InfraRed Experiment (SAFIRE)
International Optical Design Conference 2010, 2010
The SAFIRE, the Submillimeter and Far InfraRed Experiment, was designed for interstellar physics in the airborne Observatory SOFIA. SAFIRE is a cryogenic Echelle Grating spectrograph for covering 27 to 470 microns; with R ranging from 2-6,000. Here we will discuss the details of the optical design, the design process, and the performance of the instrument.
A superconducting focal plane array for ultraviolet, optical, and near-infrared astrophysics
Optics Express, 2012
Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. A MKID is an energy sensor based on a photon-variable superconducting inductance in a lithographed microresonator, and is capable of functioning as a photon detector across the electromagnetic spectrum as well as a particle detector. Here we describe the first successful effort to create a photon-counting, energy-resolving ultraviolet, optical, and near infrared MKID focal plane array. These new Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors like charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy and arrival time of every photon with good quantum efficiency. Their physical pixel size and maximum count rate is well matched with large telescopes. These capabilities enable powerful new astrophysical instruments usable from the ground and space. MKIDs could eventually supplant semiconductor detectors for most astronomical instrumentation, and will be useful for other disciplines such as quantum optics and biological imaging.
SPIE Proceedings, 2012
We have recently commissioned the 2 nd generation redshift(z) and Early Universe Spectrometer (ZEUS-2) at the Caltech Submillimeter Observatory. ZEUS-2 is a long-slit grating spectrometer (R~1000) for observations in the submillimeter wavelength regime that is optimized for observations of redshifted far-infrared spectral lines from galaxies in the early universe. Here we report on the design and first light performance of the first TES bolometer array installed in ZEUS-2. This array features 280 pixels each 1.26 mm square and arranged to provide ~35 pixel spectra at ~8 spatial positions on the sky. A 1/4-wavelength back short of 100 micron and gold mesh absorber matching the impedance of free space provides near 90% quantum efficiency for the 350 and 450 micron telluric windows. Array readout is done using SQUID multiplexers and the Multichannel Electronics. We will also report on the progress to install two additional arrays tuned to provide similar performance across the remaining telluric windows between 200-850 microns.