JRA-6 Mid-Term Report

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JRA-6 Mid-Term Report

• Filippo Maria Zerbi
• on behalf of JRA-6 Team

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JRA 6 in a Nutshell
JRA-6 is entitled Volume Phase Holographic
Gratings

• The following Contractors contribute to JRA-6
• ESO European Southern Observatory (INT)
• IAC Instituto de Astrofisica de Canarias (E)
• INAF Istituto Nazionale di Astrofisica (I)
• Osservatorio Astronomico di Brera (Coordinator)
• Politecnico di Milano (I)
• Diapartimento di Ingegneria Chimica
• Universitè de Liege (B)
• CSL Centre Spatial de Liege (ATHOL)

Purpose of the JRA-6 is to enhance the
applicability of VPHGs in Astronomical
Instrumentation
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• VPHGs ?

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VPHGs ?
a slice of photosensitive material with n
modulated by an interferometric pattern of
fringes grooved in by holography.
The PS-material is embedded in glass components,
active or passive following the optical design,
that can be AR-coated
The orientation of the fringes determines the
reflection or transmission behavior.
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VPHGs ?
Regular pattern of varying refractive media with
scale-length of the same order as ?.
Multiple reflection and diffraction in a
multi-layer configuration
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VPHGs ?

• VPHGs Efficiency Predicted via RCW-Theory -
  Commercial or custom
• codes (U-Mich INAF-Brera).
• Back of an envelope estimates via the Kogelnick
  (1962) approximation

Crucial Quantities
There is a pair ?B, ?2B for which maximum
coherence/efficiency is reached
For a given ?2B minimum coherence/efficiency
is reached for ? ?B ??. This defines the BLAZE
function B(?, ?2B)
If we scan the Bragg angle (e.g. rotating the
VPHG) the maximum coherence/efficiency is reached
at different ? values. This defines the
SUPERBLAZE function SB(?B, ?2B).
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VPHGs ?
Blaze and superblaze are at some extent tunable
in width and height to ones needs fiddling with
?n and L
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VPHGs ?
Photosensitive Material ? Baseline Dichromated
Gelatin

• PROs
• Very High Transmission in VIS-NIR
• Suited for (?n L) needed for gratings
• CONs
• Dirty Wet Chem Post-processing
• Higroscopic
• No redder than K-band

THE limit to VPHGs performances
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Relevance of VPHGs in Astronomy
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VPHGs in Astronomy
Gain
Efficiency
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VPHGs in Astronomy
Easy Handling and Maintenance
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VPHGs in Astronomy

• As Grism in low resolution spec.
• Implemented
• AFOSC_at_ ASIAGO 1.8 mt
• d.o.lo.re.s _at_ TNG 3.6 mt
• FORS_at_VLT 8.2 mt
• VIMOS_at_VLT 8.2 mt
• Planned
• EFOSC_at_ESO 3.6 mt
• EMIR_at_GTC 10mt
• MUSE_at_VLT 8.2 mt
• XXX_at_EELT 42mt

• As Cross Disperser in HR spec.
• Planned
• UVES_at_VLT 8.2 mt
• Espresso_at_VLT 8.2 mt
• CODEX_at_EELT 42mt

• As Core element in HR spec.
• Planned
• SONG Project (0.8 mt)
• REM Telescope (0.6 mt)
• ..

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Status ANTE-OPTICON
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Status ANTE

• First fully functional prototype used at AAO
  (K.Taylor, G.Robertson) 1997(8)
• Pioneering USA work under NSF grant at NOAO (Sam
  Barden) collaboration with Kaiser Optical (Jim
  Arns) -1997-2000 (single world producer at the
  time).
• Richard Rallison (Utah) steps into the market
  with cheap (but not always
• science-grade) devices 1999
• Chris Clemens hosts at UNC two thinkshops (1999
  and 2000)
• to join efforts of the astronomical community
  toward the use of VPHGs

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Status ANTE

• Dimensions. First problem to solve.
• Kaiser Optical and Rallison max size 10 cm.
• Pupils of exisiting instruments 20 cm. ELTs
  pupils gt40 cm

• Players. Second problem to solve.
• As single HQ player on the market implies vendor
  dictates the rules
• Astronomy needs outsourcer reactive to stimuli,
  i.e. competition

• USA. Third problem to solve.
• The EU-USA competition (or coopetition) in
  Astronomy is high.
• USA technology is not always available to other
  countries

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Status ANTE
Financial Contribution in stocks of 12.5 k
entitling to receive 1 VPHG at wish
GoalCreation of a pole (spin-off) to produce
large size Astronomical VPGHs in Europe
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Status ANTE
ATHOL
Partner of JRA-6 through ULG
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• JRA-6 Goals and Timeline

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JRA-6 Goals

• Selected Areas of research
• IR VPHGs Enable VPHGs technology in the NIR
  (1-2.5 microns) regime in cryogenic instruments.
• UV VPHGs Enable VPHGs technology in the UV
  (300-450 nm) regime with particular attention to
  cross dispersers.
• DCG Replacement Look for a replacement of the
  DCG as photosensitive element.
• Non-traditional Configurations Enhance the
  applicability of traditional VPHGs.

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JRA-6 Goals

• JRA-6 programme (OPTICON Contract Annex 1) is
  aimed to
• WP2 - Fabrication of fully functional VPHGs
  working at cryogenic (77 k) temperature and
  optimized for IR (1-2.5 µm) wavelengths
• WP3 - Improved perfromances VPHGs at visible
  wavelengths with
• attention to cross-dispersion, tuneability of the
  resolution, FPA filling.
• WP4 - Fabrication of the first laboratory-level
  re-writeable VPHG based on photochromic polymers.
• Added at Kick-off (as re-destribution of WP
  workload)
• WP5 Fabrication of fully functional VPHGs
  working at UV (300-450 nm) wavelengths with
  special care to cross-dispersion.

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JRA-6 Goals

• JRA-6 general (for each WP) milestones scheme
• Definition of a prototype characteristics
• Fabrication of the prototoype
• Analysis and characterization of the prototype
• Definition of the final deliverable
  characteristics
• Production of the final deliverable
• Analysis and characterization of the final
  deliverable
• Final product dossier editing.
• JRA-6 detailed milestones scheme (Annex I of
  OPTICON Contract)
• 6 milestones (M1-M6) specializing the above
  scheme to each WP

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JRA-6 Goals
6m 12m 18m 24m 30m 36m 42m 48m 54m 60m
WP1 D1
WP2 M1 M2 M3 M4 M5 M6 D1
WP3 M1 M2 M3 M4 M5 M6 D1
WP4 M1 M2 M3 M4 M5 M6 D1
WP5 M1 M2 M3 M4 M5 M6 D1
Prototyping Phase
Final deliverable Phase
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• WP-2 IR VPHGs

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WP-2
Prototype IR-J1 Prototype IR-H1 Prototype IR-K1
Substrate material IR-Fused silica. IR-Fused silica. IR-Fused silica.
Substrate dimensions 100x100x10 mm 100x100x10 mm 100x100x10 mm
Clear aperture Ø35 mm Ø35 mm Ø35 mm
Line density 1156.78 867.52 646.68
Operating range 1100 1400 nm 1500 1800 nm 2000 2400 nm
Efficiency gt40 at 1100 nm gt90 at 1250 nm gt40 at 1400 nm gt50 at 1500 nm gt90 at 1650 nm gt40 at 1800 nm gt50 at 2000 nmgt90 at 2200 nm gt40 at 2400 nm
AR Coatings none none none
Wavefront error ?/2 ?/2 ?/2
Prototype Definition
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WP-2
Prototype Manufacturing
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WP-2
Specific Setup built
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WP-2
Efficiency
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WP-2
Higher Order Contamination
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WP-2
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WP-2
small grating 95 efficient at 633 nm, Bragg
25.
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WP-2

• Ongoing Activity
• Full Cryo-analysis of specific IR prototypes
  (delayed).
• Definition of Science Grade devices
  characteristics.
• Procurement of the substrates for the Science
  Grade devices.
• Planned Activity
• Manufacturing of the Science Grade Devices
• Characterization of the Science Grade Devices

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WP3 Non Traditional Configurations
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WP-3
A) VPHG-based Tunable narow-band FIlter
B) Multiple trace VPHG HR spectrograph
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WP-3
Tunable Filters
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WP-3
HR Spec.
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WP-3 WP-5
Double Pass UV Cross Disperser
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WP-3

• Ongoing Activity
• Construction of the Mechanical parts of HR spec.
  (delayed)
• Definition of specific VPHGs for the Tunable
  Filter
• Procurement of the substrates for the VPHGs
• Planned Activity
• Integrating and Testing the HR spectrograph.
• Integrating and Testing the Tunable Filter .

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• WP-4 Photochromic Polymers

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WP-4
Write with light - Wipe with Light -
Re-write with light
Non linear Polarizability (n)
Linear - Transparency
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WP-4
Zoology derived for OTPICON applications
LEGO Chemistry
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WP-4
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WP-4

• Ongoing Activity
• Production of Better Quality Photochromic Films
• Definition of the Final deliverable
  Characteristics
• Planned Activity
• Production of a Higher Performances Phot-VPHGs
• Characterisation of its perfromances.

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• WP-5 UV VPHGs

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WP-5
Prototype Definition
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WP-5
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WP-5
Efficiency
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WP-5
Transmitted Wavefront
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WP-3 WP-5
Double Pass UV Cross Disperser
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WP-5
Efficiency
New set of prototypes manufactured
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WP-5

• Ongoing Activity
• Characterization of the new set of prototypes
  (delayed)
• Definition of Science Grade devices
  characteristics.
• Procurement of the substrates for the Science
  Grade devices.
• Procurement of the prism for Cross-disperser-confi
  guration
• Planned Activity
• Manufacturing of the Science Grade Devices
• Characterization of the Science Grade Devices

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• Conclusions
• Work is progressing generally in schedule.
• The viability of the technology has been
  demonstrated
• The way toward science grade devices has started
• There are some minor (not impacting the final
  deliverable) delays
• Due to problems, e.g. manpower, cash-flow,
  delays in parts delivery, etc.
• Due to intermediate results, e.g. decision to
  modify a parameter or build a new prototype, etc.
  
• My personal overall judgment of JRA6 activity is
  extremely positive.