Input Optics Definition, Function

1
Input Optics Definition, Function

• The input optics (IO) conditions light from the
  pre-stabilized laser (PSL) for injection into the
  main interferometer
• Specific functions
• modulation for RF sideband generation
• Mode cleaning of dynamic laser pointing
  fluctuations intermediate frequency and
  intensity stabilization
• Power control into interferometer
• Mode matching into interferometer cavities
• Optical isolation of the PSL and distribution of
  light for length and alignment sensing and control

2
Input Optics Conceptual Design
3
Input optics heritage

• Advanced LIGO IO evolves from current LIGO IO
• No major changes in AdL IO conceptual design
• Contiguity of IO team from current LIGO IO
• Univ. of Florida assumes primary responsibility
  (as in current LIGO)
• IO technical leaders same as in LIGO
• In terms of RD, most progressed of Advanced LIGO
  subsystems
• Relatively low technical risk
• Conceptual Design and Design Requirements
  completed May 2002
• Major RD
• Electro-optic modulators materials, architecture
• Faraday Isolators thermal lensing,
  depolarization, dynamics
• Adaptive mode matching
• Mode cleaner thermal and noise modeling

4
Current Progress I

• Isolators
• Demonstration of fully compensated TGG-based
  isolator
• 45 dB isolation
• Negligible thermal lensing

• Modulators
• RTP excellent thermal properties and nonlinear
  properties
• RTP-based transverse modulator prototype tested
• temperature-stabilized
• no thermal lensing observed at 50 W powers

Thermal compensation
No thermal compensation
5
Current Progress II
Model Performance

• Adaptive Mode Matching
• in situ adjustment of mode matched based on
  laser/radiative heating
• Ratio of writing beam to reading beam waist
  large
• Preserves modal content

6
Technical Challenges/Opportunities

• Challenges
• High power poses problems to IO optical
  components
• Thermal lensing, thermally-induced
  depolarization, long term degradation
• Primarily affects electro-optic modulators
• Sideband amplitude stability
• challenging for DC readout beyond
  state-of-the-art for RF oscillators
• Excess laser jitter may require active
  suppression
• MC technical radiation pressure at requirement
  limit for required frequency noise
• Opportunities
• Novel adaptive optics

7
RD Plans for 2004

• Upgrade to 100 W laser testing
• LIGO Livingston High Power Test Lab (underway)
• EOM prototype testing
• RF amplitude modulation, amplitude modulation
  from parasitic nonlinear processes
• Frequency stability (at limit of RF oscillator)
• Long term laser exposure and damage testing (100
  W powers)
• Contingency modulation architectures if required
• Mode cleaner RD
• MELODY model of thermal effects (carrier,
  sidebands), potential astigmatism (mostly done)
• Better understanding of beam jitter in PSL if
  necessary, examination of possibility of second
  mode cleaner

8
RD Plans for 2004 (contd)

• Faraday isolation
• Investigate dynamic effects due to loss of lock
  and rapid thermal loading
• Trade study of optimal commercial components
  (wave plates, polarizers, TGG)
• Interferometer mode-matching
• Prototype thermal adaptive telescope in vacuum
• Preliminary Advanced LIGO telescope design
  MELODY modeling of performance under various
  powers
• System interface issues
• In-vacuum layout (underway)

9
Schedule

• Design phase
• Design Requirements and Conceptual Design May
  2002 (completed)
• Preliminary Design Phase April 2005
• Final Design November 2007
• Milestones
• Design LASTI mode cleaner and ancillary input
  optics November 2002 (completed)
• Deliver prototype modulators and isolators to
  Gingin High Power Test Facility June 2004
• Deliver LASTI mode cleaner and ancillary optics
  January 2005
• Deliver prototype modulators and isolators to
  LASTI January 2006
• Fabrication and assembly phase
• Major optics procurement (all interferometers)
  August 2006 August 2009
• Input optics installation
• Interferometer 1 thru August 2008
• Interferometer 2 thru February 2009
• Interferometer 3 thru September 2009

10
IO Team

• IO Manager D. Reitze (Univ. Florida)
• LIGO Lab Liaison P. King (CIT)
• IO Team
• Univ. of Florida
• R. Amin, K. Franzen, G. Mueller, M. Rakhmanov, D.
  Tanner, V. Quetschke, L. Zhang
• Institute of Applied Physics (Nizhny Novgorod,
  Russia)
• E. Khazanov, A. Malshakov, A. Shakin, A. Sergeev
• LIGO Lab
• P. King, R. Savage