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Volume Phase HolographicGrating

Efficiencies of Transmission Gratings
TEM mode
TEM mode

Surface relief grating:
Efficiency decreasessteeply below 4 !/".

VPH (Volume Phase Holographic)
grating (#n ~ 0.02): Efficiency
increases up to 100% below 4 !/".
(Oka et. al., SPIE, 5005, 2003)

Used for determinationof high z galaxies

VPH grism with
ZnSe prism

VPH grism

Echelle grism

FOCAS Grisms
Size: 110 ! 106 ! 106 (max).

4 SR grisms: 300 < R < 1,400.
1 Echelle grism: R~2,500.
8 VPH grisms (3 grisms with
ZnSe prisms): 1,600 < R < 7,000,
Collaboration of JWU (JapanWemen’s Univ.) and NAOJ.

Surface relief grism(Ebizuka et. al. PASJ, 63, 2011a)

New VPH grisms for FOCASVPH grating(364 g/mm, Blaze: 800 nm,!/"=3.47, R~1,600 )Surface relief grating(300 g/mm, Blaze: 750 nm,!/"=4.44, R~1,400 )VPH grating is usefulfor lower dispersion!

Limitation of VPH grating" =31.7 deg.
!n=0.10!n=0.07!n=0.04!n=0.02

3rd
6th10th" =30.9 deg.

Band width of VPH grating becomesnarrow in diffraction angle: $increase because semi-amplitude ofindex modulation of dichromatedgelatin (DCG) is #n < 0.15.
(Baldry et al., PASP, 116, 2004)

Diffraction efficiency ofVPH grating decrease
toward higher orders.
(Oka et. al., SPIE, 5290, 2004)

Polarized Diffraction Efficiency of VPH Grating' # ( n max $ n min ) t *"S = sin (+) %( n max + n min ) sin2& ,2!

' # ( n max $ n min ) t cos2% *"P = sin (+) &( n max + n min ) sin2% ,2!

Measured polarized diffraction
efficiencies of VPH grating.
nave= (nmax - nmin)/2 = 1.53,#=0.984 µm, t = 20 µm,% =19.8° @1.02 µm.

Calculated polarization diffraction
efficiencies vs. t of a VPH grating.
!n = (nmax - nmin)/2 = 0.017(Ebizuka et. al. PASJ, 63, 2011b)

Volume Binary Grating

Volume Binary Gratingf = 0.5"#•#n = (nmax-nmin)/2 ~ 0.5.
•Polarized diffraction
efficiencies of S and P
polarization coincide witheach other by tuning of f
and t. While aspect ratio
becomes t : w = 1:20 ~ 100.

(Gerritsen, Jepsen:Appl. Opt., 37,1998)

f = 0.2

Filling factor: f=w/!
nH=1.46, nL=1.0,$ =45 deg.
(Gupt & Peng, Appl. Opt., 32, 1993)

Volume Binary Grating for Higher Diffraction Orders

nH=1.89, nL=1.46,$ =41.3°, f = 0.1

t:w (Aspect ratio)= 1:22
INAF Osservatorio Astronomico di Brera, Italy(Bianco & Ebizuka, SPIE,8450, 2012)

Photo Resist Grooves with High Aspect Ratio
30°

T

SEM image of grooves (L&S:10"m), tilting with 30°.
Photo resist: KMPR1000.

Thickness of Grooves

46.7 ["m]""T# sin 30°~ 46.7"m!"93 ["m]Cr mask pattern

L&S: 10"m $%1"m : 9"maTnuOhlmv?CiBwxy>z

Birefringence Volume GratingBirefringence VPH Gratingn Smax " n Smin(n " n Pmin ) cos2# P= Pmax
(n Smax + n Smin )sin2# S (n Pmax + n Pmin )sin2# P
n Smax " n Smin(n Pmax " n Pmin ) cos2$ P=(n Smax + n Smin ) # 2sin$ S cos$ S = ( n Pmax + n Pmin ) # 2sin$P cos$ P!

Snell’s low

n Smax " n Smin ( n Pmax " n Pmin ) cos2# P$cos # Scos# P!

!

Calculated polarization diffraction
efficiencies versus grating thickness tof birefringence VPH grating.

Birefringence Binary Bragg (3B) Grating

Echellegram
High diffraction efficiency
in higher diffraction order.
Active optical element:
Window ‘’Grating,
Grating ‘’Polarizer,
Day lighting, Head-up
display, 3D display,
Optical communications& computing, …

Polarized Diffraction Efficiency ofVPH Grating and 3B Grating

Dicson’s VPH grating (Polarizer)
calculated by Kogelnik method.
nL= 1.46, nH=1.54, %B =48.5°.

3B grating calculated by RCWA.
nL=1.46, ns= 1.544, np = 1.60, %B =45°.

w:t (Aspect ratio) = 1:20~100 !"1:4~20

Liquid Crystal Grating (3B Grating)LC grating
Digitalcamera

Lens + diffuser

Polarizer

Hg lamp

Polarizer angle: 60 ~ 70°

Polarizer angle: 90°

Specifications
Type: replicated grating
Groove period (#) : 2 "m(Line & space: 1 "m)Groove thickness (t): 1 "mOrientation layer(Grating vector)

Polarizer angle: -60 ~ -70°

Images of the first order diffraction@{jr|>}~•r€•‚ƒ„12…

Efficiencies of Liquid Crystal (3B) Grating

Immersion Grating

Ge Immersion Grating for GIGMICS(Germanium Immersion Grating Mid-Infrared Cryogenic Spectrograph)

Nano-precision
machine and ELID
grinding method.
30 ! 30 ! 72 [mm],# = 68.75°, !=600µm

Spent about 400 hours for fabrication.
@RIKEN(Ebizuka et. al. SPIE, 4842, 2003b)

Wave front (633nm, left) and Far Field Images (10.6mm, right)of Immersion Gratings

The 3rd trial (GaAs), PV: 961nm, rms: 154nm

The 4th trial (Ge), PV: 583nm, rms: 87nm

The 5th trial (Ge), PV: 577nm, rms: 107nm

GIGMICS
Si:As
512*412Collimator (F/20, f80)

Slit viewer

4K

Camera lens(F/7.7)

InSb 256*256

800 mmForeoptics

Cross disperser

Spectrometer Optics

Immersion
Grating30K
R~ 44,000@10"m, developed by Hirahara lab., Nagoya Univ.

(Hirahara et. al., SPIE, 7735, 2010)

First Light Observation of GIGMICS

GIGMICS

KANATA 1.5m telescope, Higashi-Hiroshima Observatory, Space
Science Center Hiroshima Univ., Dec. 2010~Apr. 2011.

First Scientific Result (1): Venus$=10.12–10.81µm

Absorption lines cannot be identified to the “telluric lines”.
! CO2 hot-band & isotopes from Venus.

Trial Fabrications of Ge Immersion
Grating for R~200,000Solderingiron

10 µm image
R#$00,000@10"m !"Size: 120 x 120 x 270 mm%%%%%%%%%!"Fabrication time: several 1,000 hours

Quasi-Bragg Immersion Grating© DISCO• Machining of dicing saw
makes smooth surface• Easy tooling.
• Fabrication time forgrating with 120 x 120 x
270 mm !"Several 100hours?
(Ebizuka et. al. SPIE, 6273, 2006)

Trial Fabrication of Quasi-Bragg Grating

A: 10 x 10 x 0.2 x 40 pcs (left),
B: 1.5 x 10 x 0.2 x 40 pcs (right)

Laminatingof Mirror
PlateCutting

Lapping andPolishing
for WaveGuideDiffraction of Quasi-Bragg Grating

Small incident angle

Ideal incident angle

Diffraction by quasi Bragg grating(A type). % = 0 (top), % = 0.6 (middle),% = 1.2 (bottom).
Spacing of mirror plates is imperfect.

Large incident angle

Fabrication of Immersion Grating for
Near IR by Means of Diamond Machining# =200 "m" =60°

Diamond endmil

Specifications
Material: Si, (Ge)Wavelength range : 1 ~ 2.5 µm
Groove period (#) : 200 µm
Blaze angle ("): 60°

Diamond bite†‡hopˆ d“0nhop”• ‰Šdh‹012{>zCurrent and future works•Trial fabrications of high aspect rectangular grating with duty ratio of 1 : 8~10.
•Trial fabrications of liquid crystal gratingwith high aspect ratio.
•Trial fabrications of immersion grating
for near IR by means of novel diamondturning methods.
•Trial fabrications of quasi-Bragg immersion grating.

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Thank you for yourkind attention!