ABSTRACT
High-purity silicon is a readily available material of utility in realizing a variety of long-wavelength optical and guided wave components. The transmittance of uncompensated for silicon is measured in the far- and mid-infrared regimes at room and cryogenic temperatures. The experimental and analysis techniques used to extract the refractive index from 100-1000cm-1 (100-10 µm) are presented, and the results are compared to the literature. An average refractive index below 300cm-1, n^(300K)=3.417+i8.9×10-5, which transitions in cooling to n^(10K)=3.389+i4.9×10-6, is observed.
ABSTRACT
The dielectric properties of selected conductively-loaded polyimide samples are characterized in the microwave through far-infrared wavebands. These materials, belonging to the Vespel family, are more readily formed by direct machining than their ceramic-loaded epoxy counterparts and present an interesting solution for realizing absorptive optical control structures. Measurements spanning a spectral range from 1 to 600 cm-1 (0.03-18 THz) were performed and used in parametrization of the media's dielectric function at frequencies below ≈3 THz.
ABSTRACT
The presence of a bright (Poisson) spot in the geometrical shadow of circular/spherical shapes has been known for the past two centuries. A broad class of telescopes that involve simultaneous transmit and receive require suppression of the reflected light from the secondary mirror on the detector. For instance, the on-axis design of optical telescope for the evolved Laser Interferometric Space Antenna (eLISA), a re-scoped version of the baseline LISA mission concept, requires suppression of reflected laser light from the secondary mirror on the detector. In the past few years, the hypergaussian functions with petal-shaped realization have been shown to significantly suppress intensity along the optical axis. This work reports on fabrication of a series of petal-shaped masks using a variety of techniques such as 3D printing, photolithography, and wire Electro Discharge Machining. These masks are designed and fabricated to operate in the range of Fresnel numbers between 4 and 120. This paper discusses the challenges, successes, and failures of each fabrication technique and the optical performance of typical masks with suggestions for potential follow up work.
ABSTRACT
The Advanced Technology Large Aperture Space Telescope (ATLAST) team identified five key technology areas to enable candidate architectures for a future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, "Enduring Quests, Daring Visions." The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technology areas are internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescope systems, detectors, and mirror coatings. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current technology readiness level (TRL), thus identifying the current technology gap. We also report on current, planned, or recommended efforts to develop each technology to TRL 5.
ABSTRACT
The future needs of space-based, observational planetary and astronomy missions include low mass and small volume radiometric instruments that can operate in high-radiation and low-temperature environments. Here, we focus on a central spectroscopic component, the bandpass filter. We model the bandpass response of the filters to target the wavelength of the resonance peaks at 20, 40, and 60 µm and report good agreement between the modeled and measured response. We present a technique of using standard micromachining processes for semiconductor fabrication to make compact, free-standing, resonant, metal mesh filter arrays with silicon support frames. The process can be customized to include multiple detector array architectures, and the silicon frame provides lightweight mechanical support with low form factor.
