First Light in the T-1007 Prototype 40m Optical Cavity for Holometer/Axions

First Light in the T-1007 Prototype 40m Optical Cavity for Holometer/Axions

Aaron S. Chou

Wilson Fellow, FNAL

All Experimenters Meeting

May 2, 2011

Axions Holographicinformation bound

• Fermilab: Aaron S. Chou, Hank Glass, Gaston Guitierrez,

Craig Hogan, Jason Steffen, Chris Stoughton, Ray Tomlin, Jim Volk, William Wester.

• MIT LIGO: Sam Waldman, Rai Weiss

• U.Chicago Steve Meyer, Bobby Lanza, Lee McCuller

• U. Michigan LIGO Dick Gustafson

A.S. Chou, All Experimenters Meeting, 5/2/112

The Actors


Application 1: Use lots of photons to search for rare photon-photon scattering processes mediated by axion-like or Higgs-like particles

3

Tevatron

Increase photon flux to 1024 γ/s, improve axion sensitivity by 4 orders of magnitude.

Application 2: Use lots of photons to search for holographic noise

Each Nd:YAG photon has position resolution 1064 nm.

Measuring with N photons gives resolution:

1064 nm

N

Measure intrinsic blurriness of beamsplitter position due to Planck-scale quantization of space-time

Use cross-correlation technique and extended integration time to reach the predicted signal at a tiny distance scale 10-20 m/rtHz

4/18/11: Completed installation of 40m long vacuum system at MP8. Thanks to AD Tevatron vacuum group! (Scott McCormick, Bill Dymond, Dan Lambert, Bob Steinberg, James Williams)

South end, looking north North end, looking south


End station vacuum vessels hold custom optical cavity mirrors and eventually beamsplitters


UHV levels of cleanliness are required to avoid power absorption losses due to accumulation of monolayers of hydrocarbons on mirrors

RGA scan after mirror installation


Beamspot on injection mirror.

Due to seismic motion of cavity and laser frequency noise, different modes (with different transverse momentum) drift in and out of resonance.


Pound Drever Hall Locking

Measure the length of the cavity by looking at the coherent interference between:

A) Light that reflects directly from the (partially transmissive) injection mirror andB) Light that makes a roundtrip in the cavity and leaks back out

Lock condition:Zero phase difference when cavity length = integer number of ½ wavelengths.

Laser beam


Sinusoidal sweep of laser frequency by piezo-electric pressure on laser crystal.

Separation of cavity harmonics indicates the laser PZT frequency response is 1.5 MHz/Volt.

3.75 MHz


Pound-Drever-Hall technique gives a signed error signal for detecting instantaneous mismatches between the laser frequency and the cavity resonance.

Width of resonance indicates a power-recycling factor of around 20. (1W builds up to 20 W).

Just for fun:

Q=280 THz/150 kHz = 2×109


Cavity lock achieved in 3 ways Analog loop using

custom servo box.Analog loop using benchtop amplifiers, filters

Digital loop using Labview, digital data acquisition, FPGAs

Feed back to the laser PZT to force the laser frequency to follow the instantaneous resonant frequency of the cavity.


Cavity locked on Gaussian fundamental mode.


Working on stability of lock, via negative feedback loop.

Feedback signal adjusts the laser wavelength to match small changes in the instantaneous length of the cavity.


Next steps

• Refine cavity lock stability

• Measure seismic noise spectrum using error signals in feedback loop Compare quantitatively with AD seismometers.

• Develop digital control system and digital DAQ.

• Upgrade with higher reflectivity optics to achieve higher power build-up. (1 kW for holometer)

• Build 40m interferometer


Credits

• AD Alex Chen, Bill Dymond, Dan Lambert, Scott McCormick,

Bob Steinberg, James Williams• PPD

John Korienek, Carl Lindenmeyer, Todd Nebel, Jerry Taccki Herman Cease

• ES&H John Anderson, Raymond Lewis, Gary Ross, Rich White, Bill

Wickenberg, Randy Zifko Rob Bushek, Eric McHugh, Tim Miller, Angela Sands

• FESS Steve Dixon, Carl Holmgren

…

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First Light in the T-1007 Prototype 40m Optical Cavity for Holometer/Axions