Nonlinear Optical Resonator Locking for Correlated Low-Noise Lasers
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Solution Overview
Problem
Existing methods for generating non-classical photon pairs and squeezed light are inefficient due to the low probability of photon pair generation, which is dependent on the intensity of light interacting with nonlinear materials, and the synchronization of two lasers for noise reduction is limited by the noise of the low-frequency oscillator.
Innovation Solution
A photonic device and method utilizing a nonlinear optical cavity with counter-propagating lasers, where each laser is self-injection locked to different modes of the cavity, achieving both classical and quantum correlation through four-wave mixing, reducing noise below the quantum limit and enhancing the generation of entangled photon pairs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spontaneous parametric downconversion or spontaneous four-wave mixing is used to generate photon pairs, then non-classical photon pairs can be generated, but the generation efficiency is fundamentally low and strongly dependent on light intensity
Solution Approach 1:
The patent combines spontaneous four-wave mixing with cavity enhancement to create a hybrid process. The spontaneous generation mechanism is merged with resonant cavity storage, allowing the system to accumulate photons over multiple passes, thereby improving generation efficiency while reducing the required light intensity.
Solution Approach 2:
The cavity enables continuous accumulation of photon pairs through repeated passes. Instead of a single spontaneous interaction event, the system continuously enhances the interaction by circulating light through the nonlinear medium multiple times within the resonant cavity, maintaining useful action over extended periods.
2Reliability
If two lasers are synchronized for noise reduction, then relative noise can be reduced, but the noise cannot be better than that of the low-frequency oscillator
Solution Approach 1:
The patent introduces a common optical cavity as an intermediary that both lasers couple to. This cavity acts as a mediator that establishes phase correlation between the two lasers through their shared interaction with the cavity modes, enabling noise reduction without being limited by low-frequency oscillator noise.
Solution Approach 2:
The system employs feedback through the cavity's resonant response. The cavity's stored energy and phase information provide feedback to both lasers, synchronizing them and reducing relative noise. This feedback mechanism allows noise suppression beyond what simple low-frequency synchronization can achieve.
3Ease of operation
If optical elements such as lenses, prisms, fibers, or waveguides are used to couple light to the resonator, then light coupling can be achieved, but the light source remains independent of the resonator and light characteristics are not modified
Solution Approach 1:
The patent merges the light source and resonator into an integrated system where the laser cavity and resonator cavity are optically coupled and phase-locked. This merging creates a unified system where the light source characteristics are modified by the resonator, enabling both ease of coupling and adaptability.
Solution Approach 2:
The patent uses evanescent field coupling as an intermediary mechanism that allows direct interaction between the laser cavity and resonator without traditional optical elements. This intermediary coupling method enables tight integration while maintaining optical flexibility and modifying light characteristics through the resonator's influence.
4Productivity
If self-injection locking is used to couple laser light to resonator modes, then light coupling efficiency is improved, but the system requires precise phase and frequency matching
Solution Approach 1:
The self-injection locking mechanism uses feedback from the resonator's reflected light back to the laser cavity. This feedback automatically adjusts the laser's phase and frequency to match the resonator modes, improving coupling efficiency while the feedback control handles the complexity of phase and frequency matching.
Solution Approach 2:
The system employs self-injection locking where the resonator itself provides the feedback signal that automatically locks the laser to its modes. The system serves itself by using the resonator's own reflected light to control the laser's operating parameters, eliminating the need for external phase and frequency control mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach significantly improves the efficiency of non-classical photon pair generation and reduces relative noise in the generated signals, achieving quantum entanglement and classical correlation between lasers, with noise suppression beyond the Schawlow-Townes limit.
Implementation Method 1
the nonlinear optical characteristics of the optical cavity configured to produce a plurality of corresponding frequency harmonics within the optical cavity through four-wave mixing
Implementation Method 2
spontaneous four-wave mixing (SFWM) with a material possessing 'Chi 3' nonlinearities
Implementation Method 3
a means for improving the efficiency of non-classical photon pair generation and squeezed light is based on use of resonance devices, such as optical resonators, which result in increasing the efficiency of light matter interaction
Implementation Method 4
Optical whispering gallery mode resonators (WGMR) produced in bulk or ring configuration and other optical resonators containing matter have been used to generate photon pairs through four-wave mixing (FWM) process resulting from the interaction of a laser's emission pumping a mode of the resonator
Implementation Method 5
In another approach that has found widespread applications, light from the laser is coupled to a resonator mode and a portion of the light scattered back from the resonator serves to injection lock the laser in scheme referred to as self-injection locking
Data Source
AI summary
A photonic system is described that includes an optical cavity with nonlinear optical characteristics and two or more counter-propagating lasers configured to inject coherent light into the cavity at different frequencies to be locked to the corresponding cavity modes to achieve phase matching for four-wave mixing process. The cavity, the lasers, and the lock mechanism are configured to correlate the optical properties of the coherent light wherein the correlation is a classical correlation and/or quantum correlation. Thus, in the photonic system, quantum fluctuations of the two or more lasers can be correlated. The correlation results from the generation of an optical frequency harmonics coincident with the frequencies of the lasers along with simultaneous optical coupling of the lasers and corresponding harmonics. As a result of the coupling, the quantum noise of the lasers is correlated so the frequency noise of the individual lasers can be below the fundamental Schawlow-Townes limit.