Laser Array Sidelobe Suppression via Bessel Beam Modulation
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Solution Overview
Problem
Laser arrays face significant energy diversion into beam sidelobes due to diffraction effects from finite aperture spacing, and existing solutions for improving diffraction resistance in composite beams are inadequate, while imaging systems in space and weight-limited applications face challenges with remote placement of receive apertures.
Innovation Solution
A laser apparatus with an aperture module array that modulates power and phase of emitted beams to create a non-uniform composite beam profile, approximating a Bessel function to reduce diffraction and sidelobe energy loss, and incorporates a driving system to steer beams and an imaging processor for target information calculation without remote receive apertures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a laser array uses finite spacing of individual array apertures, then the device complexity is reduced and ease of manufacture is improved, but significant energy is diverted into beam sidelobes due to diffraction effects
Solution Approach 1:
The patent applies local quality by modulating the amplitude and phase of individual aperture elements non-uniformly across the array. Specifically, apertures are assigned different complex weights where the amplitude varies according to a Bessel function profile and the phase varies according to a quadratic phase distribution. This local variation in aperture characteristics creates a composite beam with reduced sidelobes while maintaining the finite spacing advantage.
Solution Approach 2:
The patent changes the parameters of individual aperture emissions by applying amplitude modulation following a Bessel function J0(αr) and phase modulation following a quadratic form k(r² - rz). These parameter transformations at the aperture level result in a composite beam profile that approximates an ideal Bessel beam, thereby reducing diffraction-induced sidelobes while preserving the practical advantage of finite aperture spacing.
2Reliability
If geometric arrangement optimization of aperture arrays is used, then significant gains in diffraction resistance are demonstrated, but the energy diverted to sidelobes is not decreased sufficiently to match the performance of a single monolithic laser beam
Solution Approach 1:
Rather than relying solely on geometric optimization, the patent introduces local quality variations through amplitude and phase modulation of individual apertures. The amplitude follows a Bessel function profile and the phase follows a quadratic distribution, creating localized differences in aperture contributions that collectively produce a composite beam with superior diffraction resistance and reduced sidelobe energy loss compared to uniform geometric arrangements.
Solution Approach 2:
The patent creates a composite beam by coherently combining emissions from multiple apertures with non-uniform amplitude and phase weights. This composite approach, where each aperture contributes a modulated wavefront, produces a composite beam profile that approximates an ideal Bessel beam, achieving diffraction resistance and sidelobe suppression performance that exceeds simple geometric optimization of individual apertures.
3Measurement precision
If imaging systems use an array of receive apertures positioned remotely from transmit apertures, then target imaging and phase information collection are enabled, but the system becomes inconvenient and impracticable in airborne and space-limited applications
Solution Approach 1:
The patent merges the transmit and receive aperture functions into a single integrated aperture array. The same physical apertures that transmit laser energy also receive reflected light for imaging and phase measurement. This combination eliminates the need for separate remote receive apertures, making the system practical for airborne and space-limited applications while maintaining the capability to collect accurate phase information through the driving system's phase modulation and detection capabilities.
Solution Approach 2:
The aperture array is designed with multi-functionality, serving both as transmit apertures for laser beam generation and as receive apertures for target imaging and phase information collection. The driving system enables these apertures to perform multiple functions by controlling amplitude and phase for transmission while simultaneously allowing reception of reflected light for holographic imaging and phase measurement, thereby eliminating the need for separate remote receive aperture systems.
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 solution minimizes energy waste by reducing sidelobe energy loss and allows for on-axis aperture corrections, enabling efficient beam steering and target imaging without the need for remote aperture placement, enhancing performance in space and weight-limited applications.
Implementation Method 1
a significant amount of the array's transmitted radiant energy is diverted into beam sidelobes due to diffraction effects from finite spacing of individual array apertures
Data Source
AI summary
A laser apparatus comprising an aperture module array including two or more aperture modules, each aperture module of the array being optically couple-able to a source of coherent electromagnetic radiation and configured to emit a beam of radiation received from the source. The apparatus emits a composite beam comprising beams emitted by the respective aperture modules and modulates at least one of the beams in power and phase relative to at least one other of the beams such that a desired non-uniform composite beam profile is provided.