Gradient-Index Etalon for Stable Oblique-Incidence Wavelength Control
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Solution Overview
Problem
In etalons used for wavelength selection and filtering, large incident angles cause lateral shifts of light, leading to reduced wavelength controllability and stability, requiring labor-intensive adjustments of optical components to maintain optical path length and prevent undesirable laser oscillation wavelengths.
Innovation Solution
An etalon with a dielectric material having a refractive index distribution that changes quadratically from one end surface to the opposing end surface, reducing lateral shifts and maintaining optical path length equivalence with uniform refractive index etalons, while allowing light to be incident at angles other than perpendicular.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light is made incident at a large angle to the etalon, then wavelength selection capability is improved, but lateral shift of the light beam increases causing loss of wavelength controllability
Solution Approach 1:
The patent applies local quality by creating a non-uniform refractive index distribution within the etalon medium. Specifically, the refractive index is made to vary in the lateral direction (perpendicular to the optical axis), with higher refractive index at the edges and lower at the center. This local variation in optical properties compensates for the lateral shift caused by oblique incidence, allowing the light beam to maintain its intended path and wavelength controllability even when incident at large angles.
2Measurement precision
If light is made incident at a large angle to the etalon, then optical filtering performance is improved, but optical path length changes requiring precise adjustment of optical components
Solution Approach 1:
The patent employs parameter changes by modifying the refractive index distribution parameter within the etalon. Instead of using a uniform refractive index, the invention introduces a controlled gradient where the refractive index varies laterally according to a specific function (e.g., parabolic distribution). This parameter modification inherently compensates for the optical path length changes caused by oblique incidence, eliminating the need for precise mechanical adjustment of optical components while maintaining superior optical filtering performance.
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 enhances wavelength controllability and stability by minimizing lateral shifts, reducing the need for precise optical component adjustments and maintaining optical path length, thereby improving the etalon's performance in wavelength selection and filtering applications.
Implementation Method 1
a refractive index distribution of the dielectric is set in such a manner that a lateral shift of the light becomes smaller between the first end surface and the second end surface
Implementation Method 2
operates by using interference of light between an incident surface and an emission surface (reflection surface)
Data Source
AI summary
An etalon according to the present invention is an etalon in which light is made incident from a direction different from a direction perpendicular to an incident surface and is emitted from an emission surface facing the incident surface, the etalon comprising a dielectric that has a first end surface on the incident surface side and a second end surface on the emission surface side so as to oppose the first end surface, wherein a refractive index distribution of the dielectric is set in such a manner that a lateral shift of the light becomes smaller between the first end surface and the second end surface as compared with a uniform refractive index distribution etalon under a condition that an optical path length of the light is equal. Therefore, the light according to the present invention can provide excellent wavelength controllability.