External Resonator Light Source with Spatial Filtering for Wavelength Control
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Solution Overview
Problem
Existing external resonator semiconductor lasers are limited in the elements that can be used as light sources due to the requirement for wavelength limitation by the end mirror and diffraction grating configuration.
Innovation Solution
A light source apparatus incorporating a diffraction grating, reflection unit, spatial filter, and optical resonator that allows for wavelength control and limitation through a spatial filter, enabling the use of various light sources without the need for wavelength-limited elements or optical fibers, utilizing a spatial filter, such as a pinhole, a transmission mask, or a single-mode fiber, or a combination of slits, or a combination, reflecting the polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a concave mirror with specific curvature radius is used in the external resonator, then the bandwidth is widened, but the light source element selection is limited
Solution Approach 1:
A spatial light modulator is introduced as an intermediary component between the diffraction grating and the light source. This SLM controls the angular distribution of reflected light, acting as a mediator that enables bandwidth control without constraining light source selection. The SLM's phase modulation capability allows independent optimization of spectral properties while maintaining compatibility with various light source types.
Solution Approach 2:
The invention changes the control parameter from fixed geometric constraints (curvature radius of concave mirror) to programmable phase distribution via the spatial light modulator. By dynamically adjusting the phase pattern on the SLM, the angular distribution of reflected light can be precisely controlled, enabling bandwidth adjustment without hardware changes and without limiting light source selection.
2Measurement precision
If wavelength limitation is performed using the end mirror and diffraction grating configuration, then spectral control is achieved, but the light source must be wavelength-limited
Solution Approach 1:
The spatial light modulator serves as an intermediary that decouples wavelength control from light source selection. Instead of relying on the light source's inherent wavelength-limited properties, the SLM provides active spectral control through phase modulation, allowing any broadband or narrowband light source to be used while achieving precise wavelength control.
Solution Approach 2:
The system transitions from static wavelength control (fixed by light source characteristics and mirror geometry) to dynamic wavelength control via the programmable spatial light modulator. The SLM can adaptively adjust the angular distribution and spectral properties in real-time, providing both high precision and versatility across different light source types.
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 apparatus effectively addresses the limitations by providing a light source apparatus in which an element used as a light source is not limited, enabling the use of various light sources, including semiconductor lasers, capable of wavelength control and limitation through a spatial filter, such as a pinhole, a transmission mask, or a combination, reflecting the polarization.
Implementation Method 1
a diffraction grating configured to disperse the light output from the light source to cause the light to be incident on the reflection unit
Implementation Method 2
a spatial filter configured to cause only a part of the light returned from the diffraction grating in a spatially dispersed state to pass therethrough
Data Source
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AI summary
A light source apparatus includes: a light source configured to output light; a spatial light modulator including an input unit for a control signal and configured to be able to control distribution of angles at which incident light is reflected based on the control signal; a diffraction grating configured to disperse the light output from the light source to cause the light to be incident on the spatial light modulator, and return at least a part of the light reflected by the spatial light modulator to the light source; and a pinhole configured to cause only a part of the light returned from the diffraction grating in a spatially dispersed state to pass therethrough. In the light source apparatus, an optical resonator is formed by the light source and the spatial light modulator, and the light passing through the pinhole and returned to the light source is output.