Upload
others
View
6
Download
0
Embed Size (px)
Citation preview
LSST M1 Null Lens Certifier CGH
Substrate M1C-01
Fabrication report
2011
Contents 1. Fabrication report ................................................................................................................. 3
1.1 Hologram composition ......................................................................................................... 3
1.2 Writing conditions and displacement errors ..................................................................... 4
1.3 Center errors ......................................................................................................................... 4
1.4 Independent certification of the writing process .............................................................. 5
1.5 Trajectory of rotation ............................................................................................................ 7
1.6 Summary of fabrication errors ............................................................................................ 8
Author: Jean-Michel Asfour Created: 03/11/2021 14:11:00 Version: 03/11/2021 14:11:00 Fabrication report LSST M1 Null Lens Certifier CGH.doc Page 3 / 8
3
1. Fabrication report
1.1 Hologram composition
Table 1. Hologram composition Radial positions
Rings for centering-test Rmin, Rmax, µm 100 Hologram structure, Rmin, Rmax, mm Data filename:
1 – 19.5 20 – 110 LSST_M1CF70_frgpos+ LSST_M1C70_frgpos
Caption: M1 Null Lens Certifier CGH. Substrate M1C-01. CLWS-300IAE - 2011
-
Fig. 1 Photo of the fabricated hologram.
Author: Jean-Michel Asfour Created: 03/11/2021 14:11:00 Version: 03/11/2021 14:11:00 Fabrication report LSST M1 Null Lens Certifier CGH.doc Page 4 / 8
4
1.2 Writing conditions and displacement errors
Table 2. Writing condition. Temperature 22.6±0.05 Co
Air pressure 1010 mbar
The laser writing beam displacement error across the hologram radius is less than < 50 nm (P-V) and 10 nm rms.
1.3 Center errors
The coordinates of the on-axis hologram center (origin of coordinate) are measured before, during and then after finishing the hologram patterning. The measured data of the coordinate errors (error of origin of polar coordinate) in the time of M1 Null Lens Certifier CGH patterning is given in Table 3. The coordinate error er corresponds to a certain pattern distortion at a given radius r. Table. 3 #/# Coordinate,
r [μm] Coordinate error, �r [μm]
Spacing, S [μm]
Wavefront error [�]
Trajectory error, Esp/S
1 109995.7 -0.003 4.594 -0.00065 0.00479 2 107999.5 -0.007 4.594 -0.00152 0.00479 3 104998.5 -0.015 4.64 -0.00323 0.00474 4 101999.3 -0.025 4.672 -0.00535 0.00471 5 98999.91 -0.032 4.718 -0.00678 0.00466 6 95999.13 -0.006 4.75 -0.00126 0.00463 7 92996.99 0.007 4.812 0.00145 0.00457 8 89999.02 0.011 4.844 0.00227 0.00454 9 86999.78 0.014 4.906 0.00285 0.00448 10 83998.47 0.002 4.968 0.00040 0.00443 11 80999.26 -0.005 5 -0.00100 0.00440 12 77999.82 -0.025 5.078 -0.00492 0.00433 13 74998.78 -0.009 5.126 -0.00176 0.00429 14 71999.97 0 5.188 0.00000 0.00424 15 68999.53 0.005 5.266 0.00095 0.00418 16 65998.76 -0.002 5.344 -0.00037 0.00412 17 62997.59 0.009 5.406 0.00166 0.00407 18 59996.33 0.012 5.484 0.00219 0.00401 19 56999.05 0.01 5.57 0.00180 0.00395 20 53998.63 0.013 5.672 0.00229 0.00388 21 50998.82 0.021 5.774 0.00364 0.00381 22 47997.62 0.01 5.876 0.00170 0.00374 23 44998.62 -0.007 5.992 -0.00117 0.00367 24 41999.38 -0.005 6.11 -0.00082 0.00360 25 38996.9 0.003 6.25 0.00048 0.00352 26 35999.87 0.031 6.398 0.00485 0.00344 27 32999.71 0.018 6.57 0.00274 0.00335 28 29996.71 -0.002 6.758 -0.00030 0.00326 29 26999.5 0.019 6.968 0.00273 0.00316 30 23999.83 0.006 7.208 0.00083 0.00305 31 20995.61 -0.002 7.504 -0.00027 0.00293 32 17999.86 -0.004 5.188 -0.00077 0.00424
Author: Jean-Michel Asfour Created: 03/11/2021 14:11:00 Version: 03/11/2021 14:11:00 Fabrication report LSST M1 Null Lens Certifier CGH.doc Page 5 / 8
5
33 14999.45 0.004 5.47 0.00073 0.00402 34 11999.75 0.018 5.832 0.00309 0.00377 35 8999.93 0.005 6.306 0.00079 0.00349 36 5995.63 0.001 7.014 0.00014 0.00314 37 2995.43 0.002 8.26 0.00024 0.00266 38 1007.15 -0.012 1006.652 -0.00001 0.00002
RMS
0.01 0.003 0.004
Fig. 2 Wavefront errors of the M1 Null Lens Certifier CGH.
Thus, the peak coordinate error between start and end of the hologram writing is below er < 63 nm. The
wavefront errors produced by the CGH pattern distortion can be calculated to
Wr=l×er/S
where er is the CGH pattern coordinate error and S is the localized CGH pattern spacing. Wavefront errors of
the hologram are presented in Fig. 2.
1.4 Independent certification of the writing process
In order to certificate the diffractive pattern so called fiducial marks are used. These marks are written directly before the writing process of the diffractive pattern. Every mark consists of three small lines on an
area of approx. ~30 x 30 µm. The time of writing of these marks is typically within ten to twenty seconds.
During this time the writing the system is highly stable and positioning errors can be neglected. The marks are written along different radius as shown in Fig. 3 forming a ruler. The marks are placed every 3 mm along the radius. Microphotographs of all marks along the ruler are shown in Fig.4.
-0.04
-0.02
0.00
0.02
0.04
0 10 20 30 40 50 60 70 80 90 100 110
Coordinate, mm
Wav
efro
nt e
rror
, wav
es
Substrate
Hologram pattern
Ruler marks (Scale division is 3 mm)
Author: Jean-Michel Asfour Created: 03/11/2021 14:11:00 Version: 03/11/2021 14:11:00 Fabrication report LSST M1 Null Lens Certifier CGH.doc Page 6 / 8
6
Fig. 3 Ruler location. The results of the measured displacements taken from the microphotographs are presented in Table 4. The writing errors are within the desired accuracy of 0.1 µm. Table. 4.
Radius, mm 3 12 24 36 48 60 72 84 96 108
Error*, um <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
• The accuracy of the measurements is about 0.1 µm (rms). •
r=3mm
r=12mm
r=24mm
r=36mm
r=48mm r=60mm
Author: Jean-Michel Asfour Created: 03/11/2021 14:11:00 Version: 03/11/2021 14:11:00 Fabrication report LSST M1 Null Lens Certifier CGH.doc Page 7 / 8
7
r=72mm r=84mm
r=96mm
r=108mm
Fig.4 Microphotographs of the fiducial marks of the M1 Null Lens Certifier CGH.
1.5 Trajectory of rotation
The trajectory of the spindle rotation was measured before the writing process. The measured deviation of the trajectory of the spinning table rotation from an ideal circle is shown in
Fig. 5. The deviation of the trajectory of rotation - and hence the shape of the hologram zones - is less than
± 22 nm.
Author: Jean-Michel Asfour Created: 03/11/2021 14:11:00 Version: 03/11/2021 14:11:00 Fabrication report LSST M1 Null Lens Certifier CGH.doc Page 8 / 8
8
Fig. 5 Trajectory of the spindle rotation. The deviations are below ±0.022 µm (0.004 µm rms). The
uncertainty of the measurement is ~ 0.01 µm.
1.6 Summary of fabrication errors
Table 5. Error summary for M1 Null Lens Certifier CGH fabrication
Error term (Manufacturing errors for main hologram)
Value PV [µm]
Value RMS [µm]
WFE (λ) PV
WFE(λ) RMS
Origin of coordinates 0.063 0.01 0.012 0.003 Trajectory of rotation 0.002 0.004
Diffractive efficiency variation along hologram
RSS [λ] 0.005 RSS [nm] 4 Dr. Alexander Poleshchuk