Lowloss Grating for Coupling to a HighFinesse Cavity

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Low-loss Grating for Coupling to a High-Finesse
Cavity
R. Schnabel, A. Bunkowski, O. Burmeister, P.
Beyersdorf, T. Clausnitzer, E. B. Kley,
A. Tünnermann, K. Danzmann Institut für
Atom- und Molekülphysik, Universität
Hannover Max-Planck-Institut für
Gravitationsphysik (Albert-Einstein-Institut), I
nstitut für Angewandte Physik, Universität
Jena LIGO-G050204-00-Z
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Is it possible to couple light to a cavity
without transmission?
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Is it possible to couple light to a cavity
without transmission?
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Is it possible to couple light to a cavity
without transmission?

• Advantage
• Cavity finesse is limited
• by specular reflectivity
• (gt99.99 seems possible)
• Low diffraction efficiency
• Shallow structures
• Low scattering loss

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Coupler / 2nd Order Littrow
Grating equation
for d1450 nm (grating period), l 1064
nm, m2.
Suggested design values for coupling
amplitudes h02 99, h12 1, h22 as small as
possible, r2(0)98, no transmission at all, low
loss
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Coupler / 2nd Order Littrow
Grating equation
for d1450 nm (grating period), l 1064
nm, m2.
Measured (measurement inferred) values for
coupling amplitudes h02 99.4, h12
0.58, h22 0.005, r2(0) 98.8, Overall
loss_at_0 0.04
Shallow grating (40 to 50nm) structure with HR
stack on top
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Coupler / 2nd Order Littrow
Grating equation
for d1450 nm (grating period), l 1064
nm, m2.
Measured (measurement inferred) values for
coupling amplitudes h02 99.4, h12
0.58, h22 0.005, r2(0) 98.8, Overall
loss_at_0 0.04
Shallow grating (40 to 50nm) structure with HR
stack on top
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FP-Cavity Coupled 2nd Order Littrow
r2(0) 98.8, h02 99.4, h12 0.58, h22
0.005.
A. Bunkowski et al., Opt. Lett. 29, 2342, (2004)
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Coupling Relations of the 2-Port (transmissive)
Beamsplitter
ai ,bi complex field amplitudes
or
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Coupling Relations of the 3-Port (reflective)
Beamsplitter
and
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Coupling Relations of the 3-Port (reflective)
Beamsplitter
and
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3-Port Coupled FP Cavity
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3-Port Coupled FP Cavity
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3-Port Coupled FP Cavity
Gratings with minimum h2 provide a dark port
(c30) for a tuned cavity and enables power
recycling.
A. Bunkowski et al., Opt. Lett. (2005), in press
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3-Port Coupled FP Cavity
c1
Intensity port 1, UV
Cavity length, ts
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Summary

• A low loss reflective coupler to a cavity of
  Finesse 400 has been demonstrated.
• Phase relations of the three-port coupler are
  understood.
• Our results show that low efficiency,
  3-port gratings are very promising for high
  power interferometers.

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New Document Number LIGO-G050135-00-ZDocument G
050135-00-ZAuthor Roman SchnabelDocument
Date 03/20/2005Category GGroup ZTitle Low-loss
Grating for Coupling to a High-Finesse Cavity
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All-reflective Grating IFO
Proposed by R. Drever
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Coupler / 2nd Order Littrow
Grating equation
for d1450 nm (grating period), l 1064
nm, m2.
Measured (measurement inferred) values for
coupling amplitudes h02 99.4, h12
0.58, h22 0.005, r2(0) 98.8, Overall
loss_at_0 0.04
From h1gt0, h-1gt0 and time reversal consideration
one can deduce h2gt0! What is the lowest h2
possible?
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3-Port Coupled FP Cavity