Dimensional Stability of Materials at the University of Florida

1
Dimensional Stability of Materials at the
University of Florida
Alix Preston
2
Experimental Setup

• 5 layers of gold coated stainless steel
• A similar system at Goddard is used.
• The reference cavities consists of spacers made
  of Schott Zerodur with optically contacted
  mirrors

Two Zerodur cavities inside thermal shields
3

• Pound-Drever-Hall technique used to stabilize
  frequency of the laser
• By measuring the laser frequency, we are able to
  track the length of the cavity
• We then beat the two lasers together and measure
  the resultant frequency with a frequency counter

4

• Meets LISA reference cavity noise requirements
  for almost all frequencies
• Drift of 1 Hz/sec (1 pm/sec)
• This is our reference for all other measurements

5
Optical Cavities

• Silicon carbide cavity with optically contacted
  mirrors
• Possible material for the telescope structure
• Zerodur cavity with hydroxide bonded mirrors

SiC cavity with optically contacted mirrors
Zerodur cavity with hydroxide bonded mirrors
6
Hexoloy SA Silicon Carbide

• Already meets LISA requirement for the telescope
  support

7
Hexoloy SA Silicon Carbide

• Long term temperature drifts are uncontrolled
• Frequency noise does not seem to be correlated
  with room temperature changes
• Best guess right now Laser build-up inside the
  cavity changes cavity temperature

8
Zerodur with Hydroxide Bonded Mirrors

• Different tank
• Drift of 1 Hz/sec
• In the process of characterizing the new tank
• Fiber coupled laser
• Will move cavity into other tank

9
Future Plans

• Characterize new vacuum tank
• A Super Invar cavity has been made using silicate
  bonding and will begin testing soon
• A CFRP spacer will be made by the University of
  Birmingham
• SiC cavity with hydroxide bonded mirrors
• PZT cavities for arm-locking experiments
• Cesium stabilized laser as a reference

Super Invar cavity with silicate bonded mirrors
Supported by grant APRA04-0095-0007
10
Back-Link Fiber Stability
11
Experimental Setup

• Zero area Sagnac Interferometer- in air, no fiber
  yet
• Symmetric configuration
• Detection at the dark fringe measures the
  differential phase accumulated
• Balanced detection on PDs suppresses amplitude
  noise on the light
• Enclosed in a fiberglass box to limit air
  currents

12

• Measurements done in air
• In process of finding/eliminating noise sources
• Possibly move into vacuum