Immersion Diffraction Element with Acute Angle Grating Vertex
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Solution Overview
Problem
Existing immersion diffraction elements face challenges in maintaining high diffraction efficiency due to defects at the grating vertex, which lead to scattered light and reduced optical performance, especially when using brittle infrared optical materials like cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe).
Innovation Solution
A reflection type diffraction element with a triangular prism shape featuring blazed surfaces and non-blazed surfaces connected at an acute angle, where the angle between the non-blazed surface and blazed surfaces is set between 86° and 87°, preventing defects at the grating vertex from scattering light by positioning them within the shadow of the neighboring blazed surface, and using a monocrystal diamond tool for precise cutting to form the diffraction grating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional machining methods (grinding, cutting) are used on brittle infrared optical materials, then the material can be processed into a diffraction grating, but the machined surface exhibits brittle mode defects (chips, cracks) that reduce diffraction efficiency
Solution Approach 1:
The patent replaces conventional mechanical machining methods (grinding, cutting) with a non-mechanical approach by forming the diffraction grating through precision cutting using a monocrystal diamond tool with specifically designed ridgeline cutting edges. This substitution eliminates the brittle mode defects associated with traditional machining while achieving the required surface quality and grating precision.
2Manufacturing precision
If the grating vertex is sharply defined to achieve high diffraction efficiency, then the optical performance improves, but defects at the vertex (chips, cracks) scatter light and reduce diffraction efficiency
Solution Approach 1:
The patent converts the potentially harmful effect of vertex defects into a beneficial configuration by designing the ridgeline cutting edges to form an acute angle (86°-87°) with the blazed surface. This acute angle configuration ensures that even if defects occur at the vertex, they fall within the shadow of the neighboring blazed surface and do not scatter light, thereby maintaining high diffraction efficiency.
3Reliability
If the angle between the non-blazed surface and blazed surface is increased to reduce vertex defects, then defect scattering is reduced, but the diffraction efficiency decreases due to altered light reflection geometry
Solution Approach 1:
The patent optimizes the angle parameter between the non-blazed surface and blazed surface to a specific range (86°-87°) to simultaneously achieve two objectives: (1) the acute angle configuration places vertex defects within the shadow of the blazed surface, preventing light scattering; and (2) the precise angle control maintains the correct light reflection geometry for high diffraction efficiency. This parameter optimization resolves the contradiction between defect reduction and efficiency maintenance.
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 diffraction efficiency by minimizing light scattering from defects, achieving up to 97% of theoretical diffraction efficiency, even with defects present at the grating vertex, while maintaining the optical performance required for infrared spectroscopic applications.
Implementation Method 1
forming a diffraction grating by cutting one of the three side surfaces with ridgeline cutting edges of a tool
Implementation Method 2
a diffraction element that permits light to pass through the diffraction element and to be reflected by a plurality of blazed surfaces
Implementation Method 3
beams of the light reflected by the plurality of blazed surfaces interfere with each other and pass through the diffraction element for spectral separation of the light
Data Source
AI summary
Provided is an immersion diffraction element that prevents decrease of diffraction efficiency thereof so as to satisfy optical performance. A reflection type diffraction element is made of a material transmitting a light, beam having a predetermined wavelength. An echelle diffraction grating covered with a reflecting film that prevents transmission of the light beam is formed on one surface of the material. A diffraction grating is formed off in a repeated manner, a blazed surface facing incident light and a non-blazed surface connecting the blazed surface to a neighboring blazed surface. An angle formed between the blazed surface and the non-blazed surface is an acute angle. A defect generated at a grating vertex of the blazed surface fails in a shadow of the neighboring blazed surface so as to prevent the incident light from becoming scattered light due to the defect portion.