Sub-shot-noise high-sensitivity spectroscopy with optical parametric oscillator twin beams

Area of Science:

• Quantum Optics
• Atomic Spectroscopy
• Nonlinear Optics

Background:

• Nondegenerate optical parametric oscillators produce twin beams with quantum-level correlated intensity fluctuations.
• High-sensitivity spectroscopy requires minimizing noise sources, particularly shot-noise limits.

Purpose of the Study:

• To demonstrate the first high-sensitivity spectroscopy experiment utilizing twin beams from a continuous-wave optical parametric oscillator.
• To measure a very weak two-photon absorption signal in atomic potassium.

Main Methods:

• Generation of twin beams from a continuous-wave optical parametric oscillator.
• Application of twin beams in a high-sensitivity spectroscopy setup.
• Measurement of the 4S(1/2)-5S(1/2) transition in atomic potassium.

Main Results:

• A two-photon absorption signal in the 10(-7) range was successfully recorded.
• The noise background was reduced by 1.9 dB below the shot-noise limit of the employed light.

Conclusions:

• Twin beams from optical parametric oscillators are effective for high-sensitivity spectroscopy.
• This method enables the detection of extremely weak absorption signals, surpassing conventional noise limitations.