Laser Light Generating Apparatus with Single Phase-Modulator
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Solution Overview
Problem
Existing laser light generating apparatuses face challenges in stabilizing multiple external resonators using a single modulation signal, leading to instability due to uneven S/N ratios and increased costs and complexity from the use of multiple phase-modulators, particularly when handling ultraviolet light.
Innovation Solution
A laser light generating apparatus is designed with a single phase-modulator and nonlinear optical elements in each external resonator, where the frequency of the modulation signal is set to optimize S/N ratios, and an optical path length varying unit controlled by a feedback circuit to maintain resonance across all resonators, reducing the need for multiple phase-modulators and minimizing damage from high-intensity light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple phase-modulators are used to lock each external resonator, then the locking stability of each resonator is improved, but the apparatus size and cost increase unduly
Solution Approach 1:
The patent merges the phase modulation function into a single phase-modulator that modulates the laser light before it enters the first external resonator. This single modulator serves all multiple external resonators in the wavelength conversion chain, eliminating the need for separate phase-modulators at each resonator stage and thereby reducing apparatus size while maintaining locking stability.
Solution Approach 2:
The single phase-modulator is designed to perform a universal function of generating phase-modulated light that can be used for locking multiple external resonators at different wavelength conversion stages. The modulated light propagates through the optical system and enables locking of all resonators sequentially or simultaneously, making the phase-modulator a multi-functional component.
2Reliability
If multiple phase-modulators are used to lock each external resonator, then the locking stability of each resonator is improved, but the apparatus cost increases
Solution Approach 1:
The patent combines multiple expensive phase-modulator components into a single phase-modulator unit. Since phase-modulators containing nonlinear optical elements are relatively expensive to manufacture, reducing the quantity from multiple units to one significantly lowers the overall apparatus cost while achieving the same locking function for all resonators.
3Productivity
If phase-modulators are exposed to ultraviolet light for wavelength conversion, then the wavelength conversion is achieved, but the phase-modulator suffers damage reducing its lifespan
Solution Approach 1:
The patent extracts the phase-modulator from the direct path of ultraviolet light exposure. The phase-modulator is positioned to modulate the laser light at an earlier stage before wavelength conversion to ultraviolet occurs. The modulated light then passes through the ultraviolet wavelength conversion process, but the phase-modulator itself is not exposed to the damaging ultraviolet radiation, thereby extending its operational lifespan.
4Productivity
If high power laser light is used for wavelength conversion, then the conversion efficiency is improved, but the phase-modulator may be damaged by excessive intensity
Solution Approach 1:
The patent extracts the phase-modulator from the high-intensity wavelength conversion stage. By positioning the phase-modulator to operate on the initial laser light before it is amplified to high power for wavelength conversion, the modulator is protected from excessive light intensity that could cause damage, while still enabling efficient wavelength conversion downstream with the high-power light.
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 configuration achieves stable locking of multiple external resonators with improved S/N ratios and reduced costs by optimizing the modulation frequency for each resonator, enhancing system stability and reducing the risk of damage from high-intensity light.
Implementation Method 1
sideband waves are generated using a phase-modulator disposed at a stage preceding an external resonator
Implementation Method 2
FM sideband technology (Pound-Drever-Hall Locking technology) is typically known as an example of a technology for stable locking of an external resonator
Implementation Method 3
nonlinear optical elements, which are disposed in the first and second external resonators, to perform wavelength conversion on laser light incident on each of the first and second external resonators
Implementation Method 4
an optical path length varying unit configured to vary an optical path length of each of the first and second external resonators
Implementation Method 5
a control circuit configured to acquire at least one detection signal received by the at least one photodetector and the modulation signal, to thereby obtain an error signal for each of the first and second external resonators
Implementation Method 6
obtain an error signal for each of the first and second external resonators, and configured to control the optical path length varying unit using the error signal according to the FM sideband method
Implementation Method 7
at least one photodetector configured to receive the laser light emerging from each of the first and second external resonators
Data Source
AI summary
A laser light generating apparatus includes a laser light source, a phase-modulator, a signal generating unit configured to generate a modulation signal applied to the phase-modulator, a first external resonator, a second external resonator disposed at the stage succeeding the first external resonator, nonlinear optical elements each provided in the external resonators configured to implement wavelength conversion, an optical path length varying unit for varying the optical path length of each of the external resonators, and a control circuit having a negative feedback arrangement configured to obtain error signals for each of the external resonators, and configured to control the optical path length varying unit using the error signals according to FM sideband method. In the laser light generating apparatus, the external resonators are each held simultaneously in a resonance state by setting the frequency of the modulation signal and by controlling the optical path length of each of the external resonators.