nano-structured optics for gw detectors
DESCRIPTION
Max-Planck-Institut Für Gravitationsphysik (Albert-Einstein-Institut). Universität Hannover. Nano-structured Optics for GW Detectors. Bunkowski, O. Burmeister, D. Friedrich, K. Danzmann, and R. Schnabel in collaboration with T. Clausnitzer, S. Fahr, E.-B. Kley, and A. Tünnermann - PowerPoint PPT PresentationTRANSCRIPT
1A. Bunkowski Nano-structured Optics for GW Detectors
Nano-structured Optics for GW Detectors
A. Bunkowski, O. Burmeister, D. Friedrich, K. Danzmann, and R. Schnabel
in collaboration with
T. Clausnitzer, S. Fahr, E.-B. Kley, and A. Tünnermann
Institute of Applied Physics, Jena
Max-Planck-InstitutFür Gravitationsphysik(Albert-Einstein-Institut)
UniversitätHannover
2A. Bunkowski Nano-structured Optics for GW Detectors
Outline
Summary of:All-reflective Interferomtry
(with multilayer coatings)
Outlook to:High reflective diffractive structures
(without multilayer coatings)
3A. Bunkowski Nano-structured Optics for GW Detectors
Motivation #1
Interferometers beyond LIGOII (MW of power)
Transmission Absorption Thermal problems
All-reflective interferometers:
• Allow opaque test mass materials • New interferometer topologies
4A. Bunkowski Nano-structured Optics for GW Detectors
MI with all-reflective beamsplitter
5A. Bunkowski Nano-structured Optics for GW Detectors
What kind of gratings?
Coating below Coating on top
Period defines # of orders & direction
Grating equation: d>>scalar approachdrigorous theories (RCWA, Modal method)d<<effective medium theories (ETM)
6A. Bunkowski Nano-structured Optics for GW Detectors
1R
Cavity couplers
1st order Littrow 2nd order Littrow
Need high efficiency
(which is hard to achieve)
Only low efficiency
(3 ports are more Complicated)
99.62% achieved(Finesse of 1580)
A. Bunkowski et al, Applied Optics (in press) http://ao.osa.org/upcoming_pdf.cfm?id=66481
Input
0R1R
Input
0R2R
InputInput
Appl. Opt. (in press)
7A. Bunkowski Nano-structured Optics for GW Detectors
Cavity couplers
1st order Littrow 2nd order Littrow
Need high efficiency
(which is hard to achieve)
Only low efficiency
(3 ports are more Complicated)
A. Bunkowski et al, Applied Optics (in press) http://ao.osa.org/upcoming_pdf.cfm?id=66481
99.62% achieved(Finesse of 1580)
A. Bunkowski et al, Applied Optics (in press) http://ao.osa.org/upcoming_pdf.cfm?id=66481
Input
0R1R
Input
0R2R
InputInput
1R
8A. Bunkowski Nano-structured Optics for GW Detectors
3-port couplers
A. Bunkowski et al, Opt. Lett. 30, 1183 (2005)R. Schnabel et al, Opt. Lett. 31 658 (2006)
A. Bunkowski et al, Opt. Lett. 29, 2342 (2004)
A. Bunkowski et al, Opt. Lett. (in press) http://ol.osa.org/upcoming_pdf.cfm?id=69970
9A. Bunkowski Nano-structured Optics for GW Detectors
Angle resolved scattering
-1st +1st
diffraction ordersdue to e-beamwriting errors
backgrounddue to statistical roughness
„Variable shaped beam“
apertures
shapedbeam
electronbeam
work field stitching
E-beam exposure
10A. Bunkowski Nano-structured Optics for GW Detectors
Grating beneath coating
Small fill factor
same diffraction efficiency
systematical errorsreduced
statistical backgroundreduced
groove depth 40nmfill factor 50%
T. Clausnitzer et. al., Optics Express, 13, 4370 (2005)
11A. Bunkowski Nano-structured Optics for GW Detectors
diffraction efficiency1.5% 0.03%
systematical errors
statistical background
Large fill factor
groove depth 40nmfill factor 82%
Grating beneath coating II
T. Clausnitzer et al, Optics Express, 13, 4370 (2005)
12A. Bunkowski Nano-structured Optics for GW Detectors
Conclusion #1
Summary:• High quality all-reflective components • Demonstration of new cavity coupling concept • Reduction of scattering loss
Outlook:• Further reduction of loss• Scale to large test mass• Suspended 10 m all-reflected cavity to be built in Glasgow later this year
13A. Bunkowski Nano-structured Optics for GW Detectors
Motivation #2
S. Penn et.al, LIGO-P050049-00-R (2005)
Several fundamental noise sources as currently estimated for advanced LIGO:
14A. Bunkowski Nano-structured Optics for GW Detectors
Beating Coating Noise
The high refractive material tantala(Ta2O5) has been identified to be themain source of coating thermal noise.
Some ideas so far:
• Less tantala in stack
Innocenzo Pinto’s talk
• Doping of tantala with TiO2
Harry et al, Appl. Opt. 45, 1569 (2006)
• Total internal reflection Adalberto Giazotto’s talk
V. Braginsky and S. Vyatchanin,
Phys. Lett. A 324, 345 (2004)
• Double mirrors: F. Ya. Khalili, Phys. Lett. A 334, 67 (2005)
Substrate
Coating stack
AR-Coating stack
15A. Bunkowski Nano-structured Optics for GW Detectors
Coating Thermal Noise
Grating waveguide reflector AR-Coating stack
Substrate
Another approach:Substrate
Coating stack
16A. Bunkowski Nano-structured Optics for GW Detectors
Grating waveguide Structures
see for example: Sharon et al, J. Opt. Soc. Am. A, 14 (1997)
nLow
(substrate)
nHigh
Interfere destructively
100%reflection
Total internal reflection
0R
1T
0T
waveguide
(Simplified ray picture)
17A. Bunkowski Nano-structured Optics for GW Detectors
Narrow reflection peak
Liu et al,Opt. Lett. 23, 1556 (1998)
18A. Bunkowski Nano-structured Optics for GW Detectors
Design width of reflection peak
d: periodg: groove depthr: ridge widths: film thicknessr/d: fill factor
g
n=1.45(substrate)
d
sn=2.04
r
Fill factor
g [
µm
]
[%]
19A. Bunkowski Nano-structured Optics for GW Detectors
Design width of reflection peak
Fill factor
g [
µm
]
[%]
X
1-R
20A. Bunkowski Nano-structured Optics for GW Detectors
Broadband mirror for 1550nm
Mateus et al, IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 16, NO. 7, JULY 2004
Si
SiO2
Poly-Si
0dB reference mirror with R=98.5%
21A. Bunkowski Nano-structured Optics for GW Detectors
Conclusion #2
Summary:• High reflectivity is possible with single layerOutlook:• Check fabrication tolerances, finite size effects…• Design, build and test gratings• Think of better suited wave guide structures
22A. Bunkowski Nano-structured Optics for GW Detectors
great, greater, grating