JRA6FP6, WP6FP7

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JRA-6_at_FP6, WP6_at_FP7
.......

• Almost Conclusive Report of FP6 Activities
• with elements of Future dreams for FP7

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Who we were/are
JRA-6 Concerned VPHGs

• The following Contractors Contributed
• ESO
• IAC
• INAF-Brera
• Politecnico di Milano
• Universitè de Liege
• ATHOL

Purpose of the JRA-6 was to enhance the
applicability of VPHGs in Astronomical
Instrumentation
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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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Original Work Plan

• Preparatory Study
• Prototype Fabrication
• Prototype Characterization
• Final Device Fabrication
• Final Device Characterization

In Practice
Prototypes proved already science grade
- Research Lines arrived to a show-stopper
- Skip the prototype phase to concentrate on
final - More interesting to have another
prototype than a second better quality device
- etc. -
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Milestones
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WP 2 - IR VPHGs
Francisco Garzon Lopez - IAC
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First Set of Prototype
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Transmission
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Wavefront
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Cryo-measurements
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Science Grade Devices

• Scientific VPHGs IR-K
• Line density 486 lp/mm
• Operating range 2000 - 2400 nm
• Efficiency
• gt70 at 2000 nm
• gt90 at 2200 nm
• gt70 at 2400 nm
• AR Coatings 0.5 of reflectivity from 2000 to
  2400 nm
• Wavefront error ?/4 at 632nm

• Scientific VPHGs IR-H
• Line density 683 lp/mm
• Operating range 1400 - 1900 nm
• Efficiency
• gt70 at 1500 nm
• gt90 at 1650 nm
• gt70 at 1800 nm
• AR Coatings 0.5 of reflectivity from 1400 to
  1800 nm
• Wavefront error ?/4 at 632nm

Substrate material Fused silica Herasil 102.
Substrate dimensions Ø 135mm thickness 12 mm
Clear aperture Ø 125 mm
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Then What ?
Substrates Purchased and delivered to ATHOL
waiting for DCG Coating and Exposure.
BUT
A Key Person at ATHOL left the company and moved
to US
He was the one knowing how to operate the coating
Machine
He was the one with the best touch in DCG
Chemical post-processing
ATHOL CEO is the guru of Holography but not as
much skilled in pre and post processing the
films.
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Then What 2 ?
ATHOL claims (Oct. 2008) to have developed
improved solutions for coating and
post-processing.
They refuse to disclose any details about the new
processes calling for proprietary rights (they
have not used OPTICON Money....)
We have been able to see little samples but
confidentially know of great delays in delivery
of science devices to customers (ESO, etc.)
They insist they will deliver OPTICON prototypes
by early Dec. 2008. Little time for testing
but..... we will see
There will be consequences in the role of ATHOL
in the FP7 program (see later slides)
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Dissemination
Insausti et al - SPIE 7018 Performances of NIR
VPHGs at cryogenic temperatures
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WP 5 - UV VPHGs
Hans Dekker - ESO
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First Set of Prototype
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Transmission
Important improvement with respect to traditional
gratings
But still drops at UV Wavelength
This is due to DCG and there is nothing we can do
about
except replace DCG with something else
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Wavefront
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Cross-Disperser
Shared between WP3 and WP 5
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Transmission
Good handling of the transmitted zero-th order
multi-pass enhances the drop in the UV even
below the traditional solution
Need a replacement for DCG
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Final Science Grade Device ?
There wont be another set of final devices...
The low efficiency at UV wavelength make the all
business less attractive.
The low efficiency at UV wavelength depends on
the physical properties of DCG
Prompt to put much effort on DCG replacement.
Moves the issue to WP4 (Polymers - see next
slides)
.....and to FP7....
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WP 4 - Polymers VPHGs
Andrea Bianco - INAF Chiara Bertarelli - POLIMI
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A photochromic based VPHG
A prototype was obtained earlier by replication
of a ronchi grating
Just to understand if the whole thing was doable
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A seriousphotochromic based VPHG
The trick is as usual the modulation of the
refraction index and the thickness of the material
You need a material with a refraction index
modulation ....... that allows filming in the
required thickness
You need a material with good filming properties
....... that provides the required index
modulation
Although the balance between the two depends on
the needs of your application.
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d and Delta-n
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Photochromic Materials
The Chemical Substitutes B and B1 allow to
tailor the chemical/physical properties of the
material
Tailor B and B1 toward a good compromise between
refraction index contrast and filming capabilities
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Photochromic Polyester

• Polymeric - No matrix needed
• High content of active material (big change of
  properties)
• Good transparency in IR
• No Absorption
• No Scattering

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Delta-n and Thickness
Large Delta-n in NIR which allows large
modulations
0.03_at_1500 nm (up to 0.08)
BUT .... Maximum film thickness 5 um
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Photochromic Polyurethane

• Polyurethane Coating
• Photochromic moiety up to 50
• Polymerization after deposition
• Possibility to make multiple layers structure

• Each Stem 5-7 um thickness
• Easy to make 3-4 steps
• It is possible to cement or cover with oil to
  match with glass.

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Transparency and film quality

• Good Transparency of the film on glass substrates

• Large and constant amplitude of the interference
  fringes confirms the good quality of the film

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Delta-n and Thickness

• No difference in curve shape compared to
  Polyester but smaller refractive index.

• Consequently smaller refractive index difference
  (0..01 to 0.036)
• BUT ENOUGH TO CONCEIVE A VPHG !!!!!!!

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VPHG production
Photochromic substrates (10 15 µm) have been
initialized by exposure to UV light.
The substrate has then been placed in a
holographic set-up (_at_ CSL/Athol, Liege) with a
Ar laser (488 nm) providing 750 l/mm
From sensitivity measurements, a power of 40
mW/cm2 is known to be needed to write the
gratings in a reasonable time.
The material must absorb the laser radiation in
order to be converted. The laser frequency is
important.
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The Outcome
The film has been exposed for 230 s ..... after
which....
Line pattern effectively printed in the
substrate, as seen at the optical microscope.
The transmission spectrum in VIS changed.....
proving the transition had occurred
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Efficiency
Efficiency in the first order at an incidence
angle of 14 deg
BUT IT WORKS ...... now it needs debugging
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Superblaze
We are on the tale of the superblaze of a grating
blazed at UV-VIS Wl !!
Model tells us we are looking at a Delta-n0.01,
d3um grating
NOT at the Delta-n0.03 d10 um grating we were
expecting to
WHY ?
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The Laser Problem
The 488 nm laser (the only available at ATHOL
setup is on the tale of Photocromic transition
wavelength distribution
It Converts only some Material
Simulation of the conversion on the surface as
function of time and absorbtion
Both effective thickness and contrast are affected
Countermeasures ?
We purchased a 532 nm laser
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Dissemination
Bianco et al - SPIE 7018 Rewriteable VPHGs based
on Photochromic Material
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WP 3- Non Traditional...
Emilio Molinari - INAF
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The SuperBlaze Explorer
Measured superblaze of the 660 l/mm d.o.lo.re.s
VPHG
Range of incidence angles providing acceptable
Efficiency
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Pointed Idea
Conceived for straight-through FOCS, e.g. FORS,
d.o.lo.re.s, etc.
A system that allows straight-through imaging
And tunable incidence angle on a VPHG
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Detailed Design
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Procurement and assembly
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Test ....
If yu see Giorgio the stright-through imaging
mode works
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Dissemination
Molinari et al - SPIE 7018 VPHGs Tunes

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Promises versus deliverables
WP2 promised a) A fully cryogenic
Characterization of VPHGs at IR wl b) A Science
grade set of devices (tender to EMIR)
a) fully achieve, b) depends on development at
ATHOL
WP3 promised a) A fully functional
representative non-traditional configuration
a) Will be there in the next weeks
WP4 promised a) The first ever made photochromic
VPHG
a) Gone further. VPHG made and improving ongoing
WP5 promised a) Science Grade UV enhances VPHGs
a) Done - to the point physics allows us
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WP6_at_FP7
The show must
can (!) go on
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Who in FP7
WP6 is dedicated to new Materials and Processes
for Astronomical Instrumentation

• The following Contractors will Contribute
• IAC
• INAF-Brera
• INAF-Padova
• Politecnico di Milano
• And the following pre-screened sub-con.
• ESO
• (ATHOL)
• Intercast
• Solvay Solexis

• LAM
• INAF-IASF Milano
• Universitè de Liege
• INTA

• Institut Fresnel
• Rial Vacuum
• Astelco

Purpose of the WP6 is to explore the porting of
some (a few) new materials and processes into
Astronomical Instrumentation
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Selected Areas of research

• WP 6.1 Management

• WP6.2 Novel VPHG based devices (F.Garzon IAC)
• Slanted Fringes devices - Anamorphism -CODEX
• Echellettes - Open the higher resolution regime
• Piled Devices - Post-process the zeroth order
  light

• WP 6.3 Photochromic and photosensitive materials
  and associated devices (A.Bianco POLIMI)
• DCG Replacement - Self explanatory
• Photochromic based devices - solid optics,
  waveguides

• WP6.4 New Materials and processes for fabrication
  of traditional optics. (F.Bortoletto, INAF)
• Polymer lenses and mirrors - Weight reduction,
  specific performances, series production
• Complex Shape Optical Devices - Easier to
  manufacture free-form

570 k - 470 k from EC
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Highlights.....
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Solvay Solexis
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Transmission
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Applications
!!
193 nm
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Intercast

• Reaction Injection Molding (RIM) in CR39
• Eye Glasses fabrication
• Consumer Optics

• Tried with them the doping of CR39 with
  photochromic polymer..... it works

Solid applications - waveguides, photochromic
lenses, etc.
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MOS-Masks
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Precise writing in PCP
8mm
5 um resolution
CGH
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Thanks