Photonic Crystal Waveguide for Spectrometer Light Coupling
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Solution Overview
Problem
Conventional electromagnetic spectrometers face significant light loss due to inefficient light in-coupling in fiber-based optical arrangements, where light is primarily confined within the fiber core, with the cladding area being lossy, leading to suboptimal spectral resolution.
Innovation Solution
A photonic crystal waveguide with a circular or polygonal cross-section at the input end and a slit-shaped cross-section at the output end, utilizing photonic crystal fibers with a support structure and uniformly arranged channels to convey light efficiently, along with a shaping element and optical lens for improved collimation and index matching to minimize reflection losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional fiber-based optical arrangements are used to collect and guide light, then the optical system can be compact and easy to implement, but significant light loss occurs due to inefficient light in-coupling and lossy cladding
Solution Approach 1:
The waveguide is segmented into multiple individual fibers (e.g., 7 fibers) arranged in a specific pattern, where each fiber acts as an independent light transmission channel. This segmentation allows optimized light coupling into each fiber core while eliminating the lossy cladding problem of conventional single-fiber arrangements.
Solution Approach 2:
The patent applies local quality by having different regions of the optical system serve different functions: the input end has a circular/polygonal cross-section for efficient light collection, while the output end has a slit-shaped cross-section for spectral resolution. Each fiber's core is optimized for light transmission while the cladding is designed to minimize losses.
2Loss of energy
If the output end of the waveguide has a large cross-section, then more light can be transmitted, but the ability to collimate light for dispersive elements is reduced
Solution Approach 1:
The waveguide exhibits asymmetric cross-sectional geometry: the input end has a symmetric circular or polygonal shape for maximizing light collection from the probe, while the output end has an asymmetric slit shape that is narrow in one dimension (to improve collimation) and extended in the other dimension (to maintain light transmission). This asymmetric design resolves the contradiction between transmission and collimation.
Solution Approach 2:
The transition from a two-dimensional circular cross-section at the input to a one-dimensional slit cross-section at the output represents a dimensional reduction. This allows the system to maintain light transmission through the extended dimension of the slit while achieving the narrow beam width needed for collimation in the perpendicular dimension.
3Reliability
If there is a large refractive index difference between the waveguide material and surrounding media, then light confinement is improved, but reflection losses at interfaces increase
Solution Approach 1:
The patent optimizes the refractive index parameter by selecting waveguide materials and designing fiber structures where the refractive index difference between the waveguide core and surrounding media is carefully controlled. This parameter optimization balances two competing requirements: sufficient index difference for effective light confinement within the fibers, while minimizing index mismatch at the output interface to reduce reflection losses.
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 light transmission efficiency by allowing light to be conveyed through the entirety of the photonic crystal fibers, reducing losses and improving collimatability, thereby increasing the spectral resolution and overall efficiency of the electromagnetic spectrometer.
Implementation Method 1
wherein the fibers are photonic crystal fibers, and wherein the fibers comprise a support structure and uniformly arranged channels within the support structure
Implementation Method 2
the output end is configured to be optically connected with an optical lens, wherein the optical lens has a lens refractive index
Data Source
AI summary
A photonic crystal waveguide for conveying light with an input end and an output end to supply for an electromagnetic spectrometer includes: an input end having a convex envelope of a cross-section of the waveguide at the input end, which envelope defines a circular shape or a shape of a regular polygon with n1 corners, wherein n1 is a natural number bigger than 3; an output end having a cross-section that defines a slit shape; and a plurality of photonic crystal fibers, wherein an arrangement of the plurality of photonic crystal fibers defines the cross-sections at the input and output ends.