Grisms from germanium/silicon for astronomical instruments

Kaeufl, H. U.; Kuehl, Karl; Vogel, Steffan

doi:10.1117/12.317257

Cited by 11 publications

(7 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Some of this work occurred using silicon wafers with a view towards mounting them on prism shaped Si or Ge substrates [22][23][24], and some have fabricated gratings on thick monolithic substrates [25][26][27][28][29][30], with the obvious advantage of avoiding potential optical and mechanical problems when bonding. Most work has focused on methods for producing gratings blazed at δ 100 = cos -1 (3 -1/2 ) = 54.7º, the natural angle that occurs for {100} Si surfaces.…”

Section: Grating Fabricationmentioning

confidence: 99%

Performance of large chemically etched silicon grisms for infrared spectroscopy

et al. 2006

View full text Add to dashboard Cite

FORCAST is a mid/far-IR camera for use on NASA's SOFIA airborne observatory. We are fabricating monolithic silicon grisms to retrofit a spectroscopic capability for this facility-class instrument without affecting the imaging optics. The grisms will operate in the 5-8, 17-28, and 28-37 µm wavelength ranges. We will cover the 5-8 µm range in one exposure at a resolving power R=1200 with a 2 arcsecond slit using two grisms with one serving as a cross-disperser. For the 17-28 and 28-37 µm ranges, the resolving powers are R~140, 250 when used in low order with a slit of 3 arcseconds. We illustrate aspects of fabrication and testing during the grism development, and summarize the performance of the gratings at near-and mid-IR wavelengths. These gratings rely on procedures that can be used for modest sized (~10 cm) silicon pieces, thereby providing dispersive elements with good optical performance and large slit width-resolving power products from 1.2-8.1 µm and beyond 17 µm.

show abstract

Section: Grating Fabricationmentioning

confidence: 99%

Performance of large chemically etched silicon grisms for infrared spectroscopy

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Silicon transmission gratings were first used at mid-IR wavelengths where the spacing tolerances are more relaxed. 10 The UT group has been working on Si grisms as part of its research into Si diffractive optics. Its first flight hardware consists of a set of four grisms to provide a low dispersion mode with a long slit and a medium resolution cross-dispersed mode in the 5-8 µm and 18-37 µm bands in the FORCAST mid-IR camera on the SOFIA Airborne Observatory.…”

Section: Silicon Grisms To Datementioning

confidence: 99%

Fabrication and test of silicon grisms for JWST-NIRCam

Jaffe

Wang

Marsh

et al. 2008

Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter

View full text Add to dashboard Cite

We report on the design, fabrication, and evaluation of a set of silicon grisms for the NIRCam instrument on NASA's James Webb Space Telescope. The primary purpose of these devices is to aid in the alignment of JWST's deployable primary mirror. The grisms will also offer opportunities for slitless astronomical spectroscopy. The design of the grisms was driven by a need to fit into a constrained space, by a need for high resolving power across a broad spectral band, and by the need to survive the cosmic ray dosage to which the instrument will be subjected. The University of Texas Silicon Grating Laboratory is fabricating four identical grisms to cover 2.5-5 µm with a resolving power of 1770 at the blaze wavelength. There will be two grisms, with dispersion axes oriented at 90 o , in each arm of the NIRCam long-wavelength camera. We pattern the gratings lithographically onto high resistivity float-zone silicon prisms following the recipe developed for the recently completed grism suite for the FORCAST camera on SOFIA. We discuss the design and production of the NIRCam devices and present the results of the optical testing of the grating surfaces showing that the devices will likely exceed their performance requirements.

show abstract

“…This equation implies that modest misorientations of the grism [represented by a small change in α in Eq. 5] lead to only very small changes in the direction of the diffracted beam since the value of β changes by an almost equal amount [7]. For example, for a Si grism with n ¼ 3:4, δ ¼ 6:16°, and σ ¼ 87 μm operating at m ¼ 1 (λ blaze ¼ 22:4 μm), a device tilt of 1°in the dispersion axis leads to a deflection of the central blaze wavelength of slightly less than 0:001°f rom that of a device with no tilt.…”

Section: Introductionmentioning

confidence: 99%

Micromachined silicon grisms for infrared optics

et al. 2009

View full text Add to dashboard Cite

We demonstrate the successful fabrication of large format (approximately 50 mm × 50 mm) gratings in monolithic silicon for use as high-efficiency grisms at infrared wavelengths. The substrates for the grisms were thick (8-16 mm) disks of precisely oriented single-crystal silicon (refractive index, n ~ 3.42). We used microlithography and chemical wet etching techniques to produce the diffraction gratings on one side of these substrates. These techniques permitted the manufacture of coarse grooves (as few as 7 grooves/mm) with precise control of the blaze angle and groove profile and resulted in excellent groove surface quality. Profilometric measurements of the groove structure of the gratings confirm that the physical dimensions of the final devices closely match their design values. Optical performance of these devices exceeds the specifications required for diffraction-limited performance (RMS wave surface error<λ/20) in the near- and mid-infrared (1-40 μm). Peak diffraction efficiencies measured in the reflection range from 70-95% of the theoretical maximum. Tests of our grisms in the near infrared indicate transmission efficiencies of 30-48% uncorrected for Fresnel losses and confirm excellent performance. In infrared wavelength regions where silicon transmits well, the blaze control and high index permit high-resolution, high-order dispersion in a compact space. The first application of these grisms is to provide FORCAST, a mid-infrared camera on NASA's airborne observatory, with a moderate resolution (R=100-1000) spectroscopic capability.

show abstract

Grisms from germanium/silicon for astronomical instruments

Cited by 11 publications

References 0 publications

Performance of large chemically etched silicon grisms for infrared spectroscopy

Performance of large chemically etched silicon grisms for infrared spectroscopy

Fabrication and test of silicon grisms for JWST-NIRCam

Micromachined silicon grisms for infrared optics

Contact Info

Product

Resources

About