Abstract

To reduce the uncorrected higher-order aberrations for holographic gratings requiring an extreme dispersion, we have modified the Rowland mounting by moving the recording laser sources away from the grating. Then, with a multimode deformable plane mirror to record the grating, the correction of all the aberrations up to the fourth order inclusive is found sufficient to obtain a high-quality image. Applied to the FUSE-LYMAN grating, with a groove density of as much as 5740 grooves/mm, for which a resolution of 30,000 was required, this new recording device produces a resolution from 139,000 to 222,000 over the spectral range.

© 2000 Optical Society of America

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References

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  1. M. Duban, “Theory of spherical holographic gratings recorded by use of a multimode deformable mirror,” Appl. Opt. 37, 7209–7213 (1998).
    [CrossRef]
  2. M. Duban, K. Dohlen, G. R. Lemaı̂tre, “Illustration of the use of multimode deformable plane mirrors to record high-resolution concave gratings: results for the Cosmic Origin Spectrograph gratings of the Hubble Space Telescope,” Appl. Opt. 37, 7214–7217 (1998).
    [CrossRef]
  3. M. Duban, “Theory and computation of three Cosmic Origin Spectrograph aspheric gratings recorded with a multimode deformable mirror,” Appl. Opt. 38, 1096–1102 (1999).
    [CrossRef]
  4. G. Lemaı̂tre, M. Duban, “A general method of holographic grating recording with a null-powered multimode deformable mirror,” Astron. Astrophys. 339, L89–L93 (1998).
  5. M. Duban, “Holographic aspheric gratings printed with aberrant waves,” Appl. Opt. 26, 4263–4273 (1987).
    [CrossRef] [PubMed]
  6. R. Grange, M. Laget, “Holographic diffraction gratings generated by aberrated wave fronts: application to a high-resolution far-ultraviolet spectrograph,” Appl. Opt. 30, 3598–3603 (1991).
    [CrossRef] [PubMed]
  7. M. Duban, “Third-generation holographic Rowland mounting: fourth-order theory,” Appl. Opt. 38, 3443–3449 (1999).
    [CrossRef]

1999

1998

1991

1987

Dohlen, K.

Duban, M.

Grange, R.

Laget, M.

Lemai^tre, G.

G. Lemaı̂tre, M. Duban, “A general method of holographic grating recording with a null-powered multimode deformable mirror,” Astron. Astrophys. 339, L89–L93 (1998).

Lemai^tre, G. R.

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Figures (4)

Fig. 1
Fig. 1

Geometry of the Rowland (recording sources C 1 and D 1) and the modified Rowland (recording sources C 2 and D 2) mountings.

Fig. 2
Fig. 2

Recording and working geometry for the FUSE-LYMAN grating in a modified Rowland mounting. L 1 and L 2 are the laser sources. PM is an auxiliary plane mirror, schematically introduced to shorten the overall dimensions of the recording device.

Fig. 3
Fig. 3

Spot diagram obtained for the FUSE-LYMAN grating at λ equal to 910, 929.1, 940, 970, 1000, 1011.2, and 1030 Å. (Isotropic scales).

Fig. 4
Fig. 4

Global and effective resolution dλ/λ versus λ for the FUSE-LYMAN grating.

Equations (19)

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sin β0-sin α0=nλ0,
sin i tan i+sin r1 tan r1+kλ1/λ0Q=0,
sin i tan i+sin r2 tan r2+kλ2/λ0Q=0,
Q=sin α0 tan α0-sin β0 tan β0,
sin i+sin r=kλn.
cos2 α/c-cos α/R-cos2 β/d-cos β/R=0.
1/c-cos α/R-1/d-cos β/R=Q/R.
c=N/P sin2 β-Q cos2 β,  d=N/P sin2 α-Q cos2 α,
N=Rcos2 α-cos2 β,  P=cos α-cos β.
tan β or tan α=Q/P1/2.
C1=kλ/λ0sin α cos α cos α-c/R/2c2-sin β cos βcos β-d/R/2d2,
 R=1750 mm, n=5764 grooves/mm, recording laser wavelength λ0=3336 Å, working order k=1, spectral range of 9101030 Å, elliptical pupil of 170×135 mm, needed resolution of λ/dλ=30,000, abbreviated as 30 for simplicity.
α0=-72.7101°,  β0=75.4793°,
α=-78.2082°,
c=3014.0909 mm,  d=1271.4125 mm.
C1=-5.492×10-8,  C2=2.134×10-7, S1=-2.354×10-11, S2=1.538×10-10, S3=-3.081×10-11.
imir=9.4°,  dm=1020 mm,
A31=9.325×10-7,  A33=5.166×10-7, A40=-2.847×10-9,  A42=-3.477×10-9, A44=-5.345×10-10.
-48.4 μm at 910 Å,  -50.5 μm at 970 Å,  -64.4 μm at 1030 Å.

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