Time delay interferometry with a transfer oscillator.

Area of Science:

• Physics
• Astronomy
• Metrology

Background:

• Accurate frequency measurements are crucial for advanced scientific applications like gravitational wave detection.
• Laser frequency noise and clock noise are significant challenges in high-precision interferometry.

Purpose of the Study:

• To develop and experimentally validate a novel time delay interferometry (TDI) technique for simultaneous reduction of laser frequency noise and clock noise.
• To assess the performance of this new TDI method for space-borne gravitational wave detection.

Main Methods:

• Utilized a transfer oscillator for coherent downconversion of an iodine frequency reference to microwave frequencies using a laser frequency comb.
• Employed an electrical delay module to introduce large time delays for time delay interferometry.
• Post-processing techniques were applied to reduce residual noise.

Main Results:

• Achieved simultaneous reduction of laser frequency noise by ten orders of magnitude and clock noise by three orders of magnitude in the 0.1 mHz to 0.1 Hz frequency band.
• Demonstrated noise reduction performance reaching 6 × 10^-8 Hz/Hz^1/2 at 0.1 mHz and 7 × 10^-7 Hz/Hz^1/2 at 1 mHz.
• Confirmed high homology between optical and microwave frequencies with residual downconversion noise below 5 × 10^-6 Hz/Hz^1/2.

Conclusions:

• The developed transfer oscillator-based time delay interferometry effectively reduces both laser frequency and clock noise.
• The achieved noise reduction performance meets the stringent requirements for future space-borne gravitational wave detectors.
• This method offers a promising alternative for frequency comb-based TDI in next-generation gravitational wave observatories.