Optical Frequency Synthesizer Using Semi-Dormant Comb Lines
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Solution Overview
Problem
Current optical frequency synthesizers face inefficiencies, coarse frequency spacing, poor resolution, and instability, particularly in generating high-frequency, precise optical references, which are essential for advanced applications but are not adequately addressed by existing technologies.
Innovation Solution
The proposed optical frequency synthesizer employs a mode-locked laser and a resonator with a fine-comb generator, using a combination of optical second-harmonic and third-harmonic generation to achieve high-resolution, compact, and programmable frequency synthesis, with a semi-dormant reference comb and tunable single-frequency laser to produce a wide range of frequencies with precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-frequency tunable laser offset locked to a fixed-frequency reference laser is used, then the frequency span is limited to several GHz, but the system complexity is reduced
Solution Approach 1:
The patent segments the frequency synthesis function into two distinct components: a mode-locked laser generating a multi-frequency comb with wide span, and an electronic DDS/DAC circuit providing precise frequency control. This segmentation allows each component to specialize - the comb generator provides adaptability while the electronic circuit provides controllability, resolving the contradiction between frequency span and system complexity.
Solution Approach 2:
The mode-locked laser comb generator serves multiple functions simultaneously: it provides a wide frequency span through its comb structure, enables precise frequency selection through electronic control of individual comb lines, and maintains stability through the inherent stability of the mode-locked laser. This multi-functionality allows a single system to achieve both wide adaptability and controlled complexity.
2Adaptability or versatility
If a mode-locked laser comb generator is used, then the frequency span exceeds an octave, but the frequency resolution is coarse with spacing of 10 GHz or larger
Solution Approach 1:
The patent segments the frequency control function by assigning different roles to different parts of the comb structure. The mode-locked laser provides the wide frequency span through its comb lines, while the electronic DDS/DAC circuit selectively controls individual comb lines to achieve fine frequency resolution. This segmentation allows the system to simultaneously achieve wide span and high resolution.
Solution Approach 2:
The electronic DDS/DAC circuit acts as an intermediary between the coarse comb structure and the desired fine frequency resolution. By selectively enabling and frequency-shifting individual comb lines, the electronic circuit mediates between the 10 GHz comb spacing and the required sub-MHz resolution, achieving both wide span and high precision.
3Volume of moving object
If a micro-resonator comb generator is used, then the device is compact, but the number of comb lines is limited to several thousand
Solution Approach 1:
The patent merges the advantages of two different approaches: the compactness of micro-resonator comb generators and the high number of comb lines of mode-locked lasers. By combining these elements into a hybrid system, the patent achieves both compact device size and a large number of available comb lines for frequency synthesis.
Solution Approach 2:
The patent employs a nested structure where the micro-resonator is integrated within or coupled to the mode-locked laser system. The micro-resonator provides compact frequency multiplication while the mode-locked laser provides the fundamental comb structure with many lines, creating a nested configuration that achieves both compactness and high versatility.
4Reliability
If existing optical frequency synthesizers are used, then the basic function is provided, but power consumption is high and efficiency is poor
Solution Approach 1:
The patent applies partial action by selectively activating only the necessary comb lines from the mode-locked laser using the electronic DDS/DAC circuit, rather than requiring all comb lines to be active simultaneously. This partial activation significantly reduces power consumption while maintaining the full frequency synthesis capability, as only the currently needed frequencies consume power.
Solution Approach 2:
The system efficiently discards unused comb lines by not generating or activating them, thereby recovering power that would otherwise be consumed. The electronic control mechanism allows dynamic activation and deactivation of comb lines, enabling the system to discard unnecessary frequency components and recover the associated power consumption.
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
This approach enables the generation of high-frequency optical references with improved precision, stability, and programmability, overcoming the limitations of existing synthesizers by using a compact design with lower power consumption and wider frequency range capabilities.
Implementation Method 1
a resonator defining optical comb lines
Implementation Method 2
a mode-locked laser generating optical fine-comb lines, wherein two non-adjacent fine-comb lines are respectively coupled to and locked to a coarse-comb line
Implementation Method 3
using a combination of optical second-harmonic and third-harmonic generation
Implementation Method 4
using a combination of optical second-harmonic and third-harmonic generation
Implementation Method 5
a single-frequency tunable laser offset locked by means of an analog phase-locking loop to a fixed-frequency reference laser
Data Source
AI summary
Several embodiments of a system and method of an optical-frequency (OF) synthesizer are disclosed that produces an optical frequency (OF) tone derived from a dispersive resonator and phase-locking to a radio frequency (RF) tone to achieve high precision. Thus, the stability of the synthesized OF tone is related to the stability of the RF tone. A frequency control word provides for a wide range of programmability to the frequency of the output OF tone. The OF synthesizer establishes the absolute value of the optical frequency of its output tone by making use of a dispersive optical resonator and applying appropriate corrections obtained dynamically by interrogating the comb lines. The reference resonator defines a semi-dormant OF reference comb, wherein the lines of that reference comb are associated with the modes of the reference resonator. Several selected modes of this reference resonator are interrogated by locking the frequency of light emitted by lasers to those resonator modes. The few selected resonator modes are the active lines of this reference comb and the other lines of this comb remain dormant, until activated, thus making the OF synthesizer a power efficient synthesizer. Concepts are presented to integrate the various components of this OF synthesizer on a chip-scale monolithic substrate.