the machined immersion grating - inafhires modes” volume 9908, ground-based and airborne...

The workshop on Dispersing Elements for Astronomy 2017 in Milan

The machined immersion grating for the absolute and simple solution of the

downsizing concept

in the high-precision infrared Spectroscopy

Takashi. Sukegawa

Oct 10,20171/33

Copyright 2017 CANON INC. all rights reserved The workshop on Dispersing Elements for Astronomy 2017 in Milan

Outline

• Introduction First History in Canon

Original Machine capability

Conventional grating for IR

Image slicer

• Immersion grating

InP

Germanium

CdZnTe

• Conclusions

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Introduction

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What is first motivation in Canon?

There is the Key Device for our semiconductor business.

There was only one vendor for this device in 2010. We thought this

situation was one of the restrictions for our business cost.

Echelle Grating with the length of 360mm

General Requirement

Grooved pitch : FSR > 1nm @193.4nm

Grooved area : Length > 350mm Width > 55mm

Wavefront Error : < 30nmRMS 100nmPV (Flat or Concave)

Absolute Diffraction Efficiency : > 60%@193.4nm Required robustness against 193nm

Although we started the difficulty at not knowing first, at the end, it succeeded.

We learned and experienced a lot from this development.

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Original Machine potential

Free Form Mechanical Cutting tool

• High precision- Placement Error : < 2nm(RMS)

- Surface roughness : < 1nm(RMS)

50,000 grooves/mm

20nm/pitch

SEM

Machined Area

300mm x 200mm x 300mm

A machining with the accuracy

of UV grating is possible in 3D.

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Performances of UV grating by 3D machining

Direction of Grooving

56m

mMaster #1 Master #26nm RMS 32nm PV

85mm (355mm)

6nm RMS 33nm PV

Wavefront Error ( 31th-order at 632.8nm by Zygo interferometer)

Flatness of Diffraction Efficiency

90%

100%

110%

0 50 100 150 200 250 300 350

au (

vs a

vera

ge)

Position(mm)

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Micro Slicer for 2D spectrograph in SPACE

Designed by Suematsu-san (NAOJ)

Suematsu, et al. “Development of compact metal-mirror image slicer unit for optical telescope

of the SOLAR-C mission” SPIE 9904, Space Telescopes and Instrumentation 2016:

Optical, Infrared, and Millimeter Wave, 990411 (29 July 2016);

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July 2012 Copyright 2017 CANON INC. all rights reserved The workshop on Dispersing Elements for Astronomy 2017 in Milan

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Machined by CANON

Micro Slicer for 2D spectrograph in SPACE


9/33Micro Slicer for 2D spectrograph in SPACE

Machined by CANON


Machined potential - 3D machining ~ e.g.②

Surface roughness 0.61nm RMS

200um

1mm

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UV VL IRVUV

Reflective

Transmittance

Immersion

An Immersed grating is the absolute and simple solution of the

downsizing concept in the high-precision infrared Spectroscopy.

for Astronomy

The types of Grating currently offered by Canon

for Astronomy

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A B

Before

Coating

After

Ag Coating

High Blazed echelle Grating for mosaicking

Grooved Length:198mm

Grooved width : 58mm Blaze angle: 79.3°

Apex angle: 88°Depth:

Pitch: 90.4um

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High Blazed echelle Grating for IR

Polarization A B

Absolute

Maximum

Diffraction

Efficiency

Average

TM 60.9% 61.3%

TE 76.2% 76.2%

Variation

(3 points ±65mm）

TM 1.9% 1.1%

TE 1.1% 1.2%

Surface Flatness

Area of 90%

PV 54.1nm 45.4nm

RMS 5.6nm 6.0nm

These performances are very close in manufactured individually.

Otsubo et al, “First high-efficiency and high-resolution (R=80,000) NIR spectroscopy with high-blazed Echelle grating: WINERED

HIRES modes” Volume 9908, Ground-based and Airborne Instrumentation for Astronomy VI; 990879 (2016)

Please refer to the following paper about the spectrograph (WINERED) which mounted the reflection

gratings by Canon.

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Immersion Grating

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Characteristics of three materials for immersion

InP Ge CdZnTe

Refractive index 3.2 4.0 2.7

Practical Wavelength（Attenuation coefficient（α）＜0.1/cm-1）

1.4μm~8μm 2μm~11μm 5μm~20μm

Low temperature operation

Size availability at the Blaze angle 75

~120mm

(85mm)~200mm ~85mm

not yet

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Potential of three materials for immersion

105

104

103

102

R(λ/Δλ）

1 5 10 20μｍ2

Assumption conditions

Blaze angle：75°Maximum Length

InP 85mm

Ge 200mm

CdZnTe 85mm

22,000

140,000100,000

CdZnTeGeInP

88,000

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CdZnTe immersion grating

2012 SPIE Astronomical Telescopes +Instrumentation Sukegawa et al

Applied Optics 2015 Ikeda et al

22mm

80mm

New View 3D

Surface roughness

3.2nm RMS

Mag : x30

Mag : x300

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Germanium immersion grating with the length of 155㎜

x10.000

X500

5μm

42mm155mm

Groove Pitch 91.74um

Blaze Angle 75°

Apex Angle 85°

Machinability of germanium is the best for us currently. There are also almost no restrictions of

material.⇒ Today, introducing “EGIG” , “GRISM”

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Test of Low temperature operation

3980 3985 3990 3995 4000

Effi

cie

ncy

(1

DV

= 5

%)

Before（TM)After（TM)

Temperature cycle x 3times

Cooling speed : 250K/9h

Minimum 25K Ge immersion grating⇒No efficiency change

We did also a same test

for InP immersion grating.

⇒ No change

Other Reference

Sarugaku et.al,“Cryogenic Performance of High-

efficiency Germanium Immersion Grating” SPIE astronomical telescopes and instrumentation(2016)

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Grooved pitch : 476um for 3-5um Blaze angle : 75 degrees

Maximum Absolute Diffraction Efficiency : 78%@ 4um

EGIG : Extremely High-order Germanium Grating

Tani, et al. “Extremely-high-order Ge Immersion Grating-based Spectrometer for Offset-free

Precision Spectroscopy in the Mid-infrared Region” CLEO®/Europe-EQEC 2017

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Germanium Grism (GG)

Grooved pitch : 2.174um

Blaze angle : 19.19 degrees

Effective Size : Φ30mm

Mag : x10,000

5μm

Since one groove is machined each by each, an device like grism with a small pitch is extremally high cost.

Notice !!

Wavefront Error : 9nmRMS 47nmPV

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InP immersion grating

x1000

X500050mm

Groove Pitch 47.3um

Blaze Angle 72°

Apex Angle 86°

20mm

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Performance of InP immersion grating

+100nm

-100nm

Ruled Direction

(in an area 14.7 mm×18.9 mm)

Gro

ove

Dire

ctio

n

RMS 12.1nm

PV 53.5nm

50%

55%

60%

65%

70%

75%

80%

85%

1546 1547 1548 1549 1550 1551 1552Ab

solu

teD

iffr

acti

on

Eff

icie

ncy

(%

)

Wavelength(nm)

TM

TE

Max : 80%

Max : 70%

Order = 180th

Wavefront Error

Absolute

Diffraction

Efficiency

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Conclusions

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Items

Reflection(L200x60)

CdZnTe(L80x20)

Germanium(L112x32)

InP(L50x20)

Surface Flatnessin grooved areaby Littrow condition

6nm RMS

54nm PV

6nm RMS

40nm PV

7nm RMS

54nm PV

12nm RMS

54nm PV

Maximum AbsoluteDiffraction Efficiency

76%(TE)61%(TM)@1.5um

74%(TE)74%(TM)

@4um(189th)

80%(TE)75%(TM)

@4um(178th)

80%(TE)70%(TM)@1.5um(180th)

Typical Performances of our gratings


Commercial Availability of immersion

Item Typical performance

Size/Resolution ~200,000

Efficiency >70%

Wavefront Error < 20nm RMS

Scatter and Ghost < 10-4

Delivery Time < 1year

Cost ExpensiveWe consider that it is reasonable enough for its total cost of system miniaturization by immersed effect.

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Conclusions

• Canon succeeded in fabricating 3 types of

completed immersion echelle grating.

• Canon could also a reflective grating.

Canon’s grating is expected

small surface flatness ( <20nm RMS)

and high efficiency (60 to 80%).

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Major risk in “ made in JAPAN “

Earthquakes during processingAlthough it has several safety counter measures in our factory,

it is difficult to respond to the direct type earthquake.

In this case,

fortunately there was no

problem in practical use

and it was used for actual

spectroscopy

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The workshop on Dispersing Elements for Astronomy 2017 in Milan

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[email protected]

the machined immersion grating - inafhires modes” volume 9908, ground-based and airborne...

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