Phase-Controlled Optical Antenna Array With Variable Grating Pitch
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Solution Overview
Problem
Existing optoelectronic phased array antennas face challenges in producing far-field light radiation with a predefined emission pattern due to exponential decrease in optical power and emission profile, requiring small diffraction grating dimensions incompatible with conventional manufacturing processes.
Innovation Solution
The solution involves manufacturing optical antennas with longitudinally varying waveguide width and diffraction grating pitch to achieve a predefined near-field emission profile and constant emission angle, without necessitating extremely small diffraction grating dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diffraction grating is located above and at a distance from the waveguide with constant dimensional parameters, then the optical losses are limited and directivity is optimized, but the optical power decreases exponentially along the longitudinal axis resulting in degradation of the far-field emission pattern
Solution Approach 1:
The patent applies local quality by making the waveguide width variable along the longitudinal axis rather than constant. Specifically, the waveguide width is modulated according to a cosine function to create a tapered profile that compensates for the exponential power decay. This local variation in geometric parameters allows the emission profile to be maintained along the entire length of the optical antenna, resolving the contradiction between maintaining reliable far-field emission patterns and managing optical power loss.
2Length of moving object
If the extraction rate is reduced by placing the diffraction grating at a distance, then the emission length is increased, but the emission profile degrades due to exponential power decrease
Solution Approach 1:
The patent employs parameter changes by systematically varying the waveguide width along the longitudinal axis according to a specific cosine function. This parameter modulation transforms the constant-width waveguide into a tapered structure that maintains consistent emission characteristics throughout its length. The mathematical relationship defined in the patent (waveguide width as a function of position) ensures that the emission profile remains stable while the emission length is extended, thus resolving the contradiction between increasing emission length and maintaining emission profile quality.
3Manufacturing precision
If the diffraction grating dimensions are reduced to modulate extraction rate longitudinally, then the emission profile can be controlled, but the dimensions become incompatible with conventional manufacturing processes
Solution Approach 1:
The patent resolves the manufacturing contradiction by shifting the modulation approach from the transverse dimension (grating period size) to the longitudinal dimension (waveguide width variation along the axis). Instead of requiring sub-100nm grating features that are difficult to manufacture, the invention uses a cosine-function-based width modulation along the length of the waveguide. This dimensional transition maintains precise emission profile control while using manufacturing-friendly dimensions that are compatible with conventional photonic fabrication processes.
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 approach enables the production of optoelectronic transmitters with a predefined, non-divergent far-field emission pattern, maintaining consistent emission angles and profiles, compatible with conventional manufacturing technologies.
Implementation Method 1
Each optical antenna 7 emits an optical signal in free space, for example by diffraction
Implementation Method 2
The optical mode circulating in the waveguide of the optical antenna has an optical power P(x) which decreases exponentially along the longitudinal axis
Implementation Method 3
only the evanescent part of the optical mode is sensitive to the periodic structures of the diffraction grating
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3
AI summary
The invention relates to an optoelectronic emitter 1 having a phase-controlled antenna array, comprising a plurality of optical antennas (7) each formed of a waveguide (5) and of a diffraction grating (8) located above and at a distance from the waveguide (5) along a vertical axis orthogonal to a main plane. The waveguide (5) has a width wc=p(x) therein that varies longitudinally according to a predefined function p, and the diffraction grating (8) has a periodic structure spacing width Λr=q(x) that varies longitudinally according to a predefined function q. The functions p and q are predefined such that a near-field emission profile S(x) of the light radiation emitted by the optical antenna (7) is equal to a predefined target emission profile Sc(x), and that a local emission angle θ(x) of the light radiation emitted is equal to a predefined target emission angle θc that is longitudinally constant.