External Cavity Laser Bandwidth Tuning via Programmable Reflection
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Solution Overview
Problem
The existing external cavity semiconductor laser configuration has a fixed radius of curvature for the concave mirror, limiting the arbitrary adjustment of the bandwidth of light returned from the diffraction grating to the light source.
Innovation Solution
A light source apparatus with a reflection unit, such as a spatial light modulator, variable curvature mirror, or variable focus lens, that controls the distribution of angles of reflected light based on a control signal, allowing for adjustable bandwidth by changing the reflection pattern or focal length, and includes a diffraction grating to disperse and return light to the light source, enabling dynamic control of the bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed radius of curvature (RoC) concave mirror is used in the external cavity semiconductor laser, then the optical path is stable and easy to align, but the bandwidth of light returned from the diffraction grating to the light source cannot be arbitrarily adjusted
Solution Approach 1:
The patent applies the dynamics principle by replacing the fixed RoC concave mirror with a spatial light modulator (SLM) that can dynamically change its reflection pattern. The SLM allows arbitrary adjustment of the bandwidth by modifying the distribution of reflection angles through programmable control, enabling the system to adapt to different bandwidth requirements while maintaining a relatively simple overall device structure.
Solution Approach 2:
The patent implements parameter changes by controlling the distribution of reflection angles of the SLM through control signals. By changing the reflection angle distribution parameter, the bandwidth of the returned light can be adjusted arbitrarily. This approach allows flexible parameter control without fundamentally changing the device structure, resolving the contradiction between adaptability and complexity.
2Measurement precision
If the distribution of reflection angles is controlled by a modulation pattern such as a spatial light modulator, then the bandwidth can be precisely adjusted, but polarization influence and unmodulated light become additional considerations
Solution Approach 1:
The patent uses parameter changes by controlling the reflection angle distribution through control signals applied to the SLM. This allows precise bandwidth adjustment while managing polarization effects as a controllable parameter rather than an uncontrollable disturbance. The systematic control approach enables precise bandwidth management despite the presence of polarization influence and unmodulated 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
The bandwidth of light returned from the diffraction grating to the light source can be arbitrarily adjusted, enhancing flexibility and accuracy in light spectrum control, and accommodating various use scenarios like optical communication and imaging.
Implementation Method 1
a diffraction grating configured to disperse the light output from the light source and cause the light to be incident on the reflection unit
Implementation Method 2
a reflection unit having an input unit of a control signal and configured to be able to control distribution of angles at which incident light is reflected based on the control signal
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A light source apparatus includes: a light source configured to output light; a reflection unit (spatial light modulator) having an input unit of a control signal and configured to be able to control distribution of angles at which incident light is reflected based on the control signal; and a diffraction grating configured to disperse the light output from the light source, 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. An optical cavity is formed by the light source and the spatial light modulator, and a bandwidth of the light returned from the diffraction grating to the light source is controlled by controlling the distribution of angles of the light reflected by the spatial light modulator based on the control signal.