Quantum linewidth limitation of a laser stabilized with a nonlinear microcavity

Area of Science:

• Quantum optics
• Laser physics
• Nonlinear optics

Background:

• Laser linewidth is a critical parameter in many optical applications.
• Optical cavities are essential for laser stabilization.
• Nonlinear optical effects in cavities can influence laser properties.

Purpose of the Study:

• To investigate the fundamental limit of laser linewidth in nonlinear optical cavities.
• To identify the key parameter governing this quantum limit.
• To propose a method for measuring this quantum limit.

Main Methods:

• Theoretical analysis of a laser locked to an optical cavity with cubic nonlinearity.
• Consideration of thermodynamic noise in monolithic microcavities.
• Proposal of using two independent lasers locked to overlapping cavity modes.

Main Results:

• The laser linewidth is fundamentally restricted by the nonlinear frequency shift per photon.
• This quantum-limited linewidth is masked by thermodynamic noise in monolithic microcavities.
• A measurement scheme using two lasers is proposed to overcome noise limitations.

Conclusions:

• The nonlinear frequency shift per photon is the key factor determining the quantum limit of laser linewidth.
• Monolithic microcavities obscure this limit due to thermodynamic noise.
• The proposed two-laser measurement technique enables direct observation of the quantum linewidth limit.