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Novel gratings?@A B1, C D1, EFG H2, IJ KL3,Andrea Bianco4, Filippo Maria Zerbi4, MG NO5
1PQRLS :TUVWXYSZ[\]^5,2_`YaLS YSbc 3PQRLS deSZ[f,4INAF Osservatorio Astronomico di Brera, Italy,
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Volume Phase Holographic
GratingEfficiencies of gratings
TEM mode
TEM mode

Surface relief grating:
Efficiency decreases
steeply below 4 !/".

VPH (Volume Phase Holographic)
grating (#n ~ 0.02): Efficiency
achieves 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

Surface relief grism

Grisms for FOCAS

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,
Developed by in collaboration
with Japan Wemen’s Univ.,
NAOJ and RIKEN.

(Ebizuka et. al. PASJ, 63, 2011a)

Relative efficiencies of grisms within
Subaru Telescope and FOCASZnSe prisms

ZnSe prisms
ZnSe prisms

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 has advantages
in moderate dispersion!

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

3rd
6th
10th

" =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.

Diffraction efficiency ofVPH grating decrease
toward higher orders.

(Baldry et al., PASP, 116, 2004)(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"#f = 0.2
(Gerritsen, Jepsen:•#n = (nmax-nmin)/2 ~ 0.5.
Appl. Opt., 37,1998)•Polarized diffraction
efficiencies of S and P
Filling factor: f=w/!
polarization coincide witheach other by tuning of f
nH=1.46, nL=1.0,
and t. While aspect ratio$ =45 deg.
becomes t : w = 1:20 ~ 100.
(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 = 1:22
(Bianco & Ebizuka,SPIE, 8450, 2012)

D-RIE (Deep Reactive Ion Etching)
Plasma Chamber

Gas Inlet
RF Coil

Aspect ratio > 60

RF Unit

1 "mPumping PortRF Unit

Wafer/Sample

60 "mHelium CoolingGas Inlet

ICP Etcher

Inductively Coupled Plasma

G sensor of capacitance type
© DENSO CORPORATION All rights reserved.

Filling dielectric lmVolume binary grating,
Oblique etching lmNovel immersion grating for vis. – NIR.

Birefringence Volume Grating

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 a prototype VPH
grating for a MOIRCS grism.

Average refractive index: n=1.53, grating
period: #=0.984 mm and thickness: t = 20 µm.
Bragg angle: % =19.8 degree at $=1.02 µm.

Calculated polarization
diffraction efficiencies versus tof a VPH grating with refractive
index modulation: !n=0.017.
(Ebizuka et. al. PASJ, 63, 2011b)

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!

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

!

Calculated polarization diffraction
efficiencies versus grating thickness
t of birefringence VPH grating.

Birefringence binary Bragg (3B) grating

Echellegram

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

Polarized Diffraction Efficiency
of VPH 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 = 1:20~100 !"1:4~20(Ebizuka et. al. SPIE 8450, 2012)

Immersion GratingGe immersion grating for GIGMICS
Nano-precision
machine and ELID
grinding method.
30 ! 30 ! 72 [mm],# = 68.75°, !=600µm

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

GIGMICSSi:As512*412

Collimator (F/20, f80)

Slit viewer

4K

Camera lens(F/7.7)

InSb 256*256

800 mmForeoptics

Cross disperser

Spectrometer Optics

Immersion
Grating

30K
R~ 50,000@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.
Targets: Vib.-rot. Transitions of Methane, Ethane, Ammonia, N2O, O3,SO2, H2O, CO2, SO2, H2S, NOx, Halogen Oxides, etc.,in the Planets,
Stellar Atmosphere, bright SFRs, CSE of late type stars, and the upper(Hirahara et. al., SPIE, 8446, 2012)
atmosphere of the Earth.

Reference: Earth’s atmosphere10.12~10.81µm

First rcientific result (1): Venus$=10.12–10.81µm

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

First scientific results (2): NGC7027$=10.12–10.81µm

Detection of [S IV] ionic fine-structure
emission line toward the planetary nebula.

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

Novel 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)

Fabrication method of novel immersion
grating for visible and near IR(Ebizuka et. al. SPIE 8450, 2012)

Conclusions• A VPH grating achieves high dispersion and highefficiency, as well as versatile for moderate
dispersion.
• A volume binary grating achieves wide bandwidthwith high efficiency and utilizes for an echelle
spectrograph.
• A volume birefringence gratings achieve highefficiency up to 100% for non polarized light.
• A novel immersion grating achieves smaller
scattering loss and able to reduce fabrication cost.
• Deep reactive ion etching (D-RIE) is promising
methods of fabrications for these high dispersion
gratings.