Optical Resonator Backreflection for Stable Frequency Comb Locking
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Solution Overview
Problem
Existing optical assemblies struggle to simultaneously achieve self-injection locking and generate a multifrequency optical resonator-based frequency comb due to unstable frequency detuning caused by thermal drift and random imperfections, leading to unreliable comb generation.
Innovation Solution
An optical assembly with a resonator configured to have periodic changes in optical characteristics along its path, allowing for a specific range of backreflection that enables both self-injection locking and multifrequency comb generation by overlapping detuning ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strong backreflection is used to achieve self-injection locking, then laser frequency stability is improved, but Q-factor decreases leading to increased parametric threshold pump power
Solution Approach 1:
The patent changes the detuning parameter between laser frequency and resonator resonance frequency to a specific range that enables both strong backreflection for self-injection locking and maintains sufficient Q-factor. By operating at optimized detuning values, the system achieves stable laser frequency locking while keeping parametric threshold pump power within acceptable limits for frequency comb generation.
2Loss of energy
If resonator is optimized for high Q-factor, then energy loss is reduced, but backreflection becomes too weak to enable self-injection locking and frequency comb generation
Solution Approach 1:
The patent introduces periodic modulation of the resonator's optical characteristics as a dynamic parameter change that actively generates strong backreflection at specific frequencies. This modulation creates resonance conditions that enhance backreflection strength without requiring the resonator to be operated at its natural high-Q resonance, thus resolving the contradiction between maintaining high Q-factor and achieving sufficient backreflection for self-injection locking.
3Reliability
If resonator has random imperfections, then backreflection is generated for self-injection locking, but frequency comb generation becomes unstable due to environmental fluctuations
Solution Approach 1:
The patent converts the harmful effect of random imperfections and environmental fluctuations into a beneficial controlled backreflection mechanism. By introducing periodic modulation of optical characteristics, the system creates a deterministic backreflection that is less sensitive to random imperfections and environmental changes, thus stabilizing frequency comb generation while maintaining self-injection locking capability.
4Reliability
If laser frequency is detuned from resonator resonance frequency, then frequency comb generation is enabled, but self-injection locking becomes unstable due to thermal drift
Solution Approach 1:
The patent implements a feedback mechanism through periodic modulation of the resonator's optical characteristics that actively maintains the optimal detuning condition. The modulation frequency and phase are adjusted based on the detected backreflection signal, creating a self-regulating system that compensates for thermal drift and other environmental fluctuations, thus maintaining stable frequency comb generation while preserving self-injection locking.
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 solution ensures stable self-injection locking and reliable generation of a multifrequency optical resonator-based frequency comb, overcoming the limitations of previous technologies by optimizing detuning ranges for both phenomena.
Implementation Method 1
the resonator is configured to have a periodic change in optical characteristics along said optical path so that the resonator can provide a backreflection which is at the resonant frequency of the resonator
Implementation Method 2
The parametric threshold pump power is an important parameter which defines laser light power density in the microresonator sufficient to initiate parametric process, namely four waves mixing leading to conversion of two photons of the pumping laser to two photons with the frequencies corresponding to resonant frequencies
Implementation Method 3
Self-injection locking (SIL) which enables locking the laser frequency to the resonator's resonance frequency and additionally provides significant narrowing of the laser line and reducing its phase noise
Data Source
AI summary
According to the present invention there is provided optical assembly (1) comprising. a laser (2) which is operable to emit light: an optical wave guide (3) having an input (3a) and an output (3b). the input (3a) of the optical wave guide (3) being optically coupled to the laser (2) so that the laser (2) can input light to the wave guide (3): a resonator (5) which is optically coupled to the wave guide (3) between the input (3a) of the wave guide (3) and the output (3b) of the wave guide (3): and wherein the resonator (5) has a resonant frequency. and wherein the resonator (5) defines an optical path (11): and wherein the resonator (5) is configured so that said optical path (11) is a closed loop: and wherein the resonator (5) is configured to have a periodic change in optical characteristics along said optical path (11) so that the resonator (5) can provide a backreflection which is at the resonant frequency of the resonator: and wherein the periodic change in optical characteristics along said optical path (11) provide an amount of said backreflection, which will provide a first detuning range in which self-injection locking of the laser using said backreflection is achieved, and. a second detuning range wherein a multifrequency comb can be generated within the resonator (5): and wherein the first and second ranges at least partially overlap, so that both self-injection locking of the laser will occur and an optical resonator-based multifrequency comb is output from the wave guide (3), when the assembly (1) is in operation. There is further provided a corresponding method of providing a optical resonator-based frequency comb at an output of a waveguide, using said assembly (1).