Squeezed light at 2128  nm for future gravitational-wave observatories

Area of Science:

• Optics
• Gravitational-wave Astronomy
• Laser Technology

Background:

• Current gravitational-wave observatories (GWOs) utilize 1064 nm lasers.
• Squeeze lasers are employed to reduce quantum noise, enhancing sensitivity.
• Future GWOs require reduced thermal noise, necessitating a shift to longer wavelengths like 2 µm.

Purpose of the Study:

• To develop a cost-efficient 2128 nm squeeze laser compatible with existing 1064 nm infrastructure.
• To demonstrate the feasibility of generating squeezed light at 2128 nm for enhanced GWO sensitivity.

Main Methods:

• Utilized 1064 nm pump light to generate squeezed light at 2128 nm.
• Employed advanced laser stabilization and squeezing techniques.
• Measured squeezing factor at megahertz sideband frequencies.

Main Results:

• Successfully realized a 2128 nm squeeze laser using 1064 nm pump light.
• Achieved direct observation of 7.2 dB squeezing at megahertz sideband frequencies.
• Identified photodiode quantum efficiency as the primary limitation, estimated at (92±3)%.

Conclusions:

• The 2128 nm wavelength is a promising, cost-efficient option for future GWOs.
• Further improvements in photodiode technology could enable larger squeezing factors at lower frequencies.
• This work facilitates the development of next-generation, more sensitive gravitational-wave detectors.