Chromatic Lens Flying Focus Laser Control
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Solution Overview
Problem
Conventional optical systems for producing focused photon beams lack flexibility and control over the laser focal volume, requiring large laser spots or waveguides to maintain small spots over long distances.
Innovation Solution
A chromatic lens system that spatiotemporally changes the focal location of a photon beam by varying its wavelength over time, allowing for a small-diameter laser focus to propagate significantly beyond its Rayleigh length while decoupling the peak intensity's velocity from its group velocity, using a combination of diffractive and refractive lenses with radially varying groove densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional near-diffraction-limited systems are used, then the focal spot size and longitudinal focusing range are determined by the f-number, but this limits flexibility and control over the laser focal volume
Solution Approach 1:
The patent changes the wavelength parameter of the laser beam over time to dynamically control the focal location. By modulating the wavelength, the system achieves flexible spatiotemporal control of the focal volume without requiring complex mechanical adjustments or multiple optical components, directly resolving the contradiction between adaptability and device complexity
Solution Approach 2:
The system transitions from a static focal spot to a dynamic 'flying focus' that can move along the propagation direction by changing the wavelength over time. This dynamic control enables the focal volume to be precisely positioned and shaped in both space and time, providing the needed flexibility without increasing device complexity
2Length of stationary object
If large laser spots are used, then the longitudinal focusing range is extended, but the spot size increases reducing intensity
Solution Approach 1:
The system pre-chirps the laser pulse before it enters the focusing optical system, creating a temporal wavelength distribution that corresponds to different spatial focal positions. This preliminary action enables the focal spot to be precisely controlled along the propagation direction without requiring large spot sizes, maintaining high intensity while extending the focusing range
Solution Approach 2:
The patent introduces the time dimension to control the focal location, transforming the problem from a spatial trade-off between spot size and focusing range to a spatiotemporal control problem. By modulating the wavelength in time, the system achieves extended longitudinal focusing range while maintaining small spot sizes and high intensities
3Area of moving object
If waveguides are used to maintain small spots over long distances, then the spot size is maintained, but the system complexity and confinement requirements increase
Solution Approach 1:
The patent extracts the focusing function from the waveguide structure itself and replaces it with external wavelength modulation control. Instead of relying on waveguide confinement to maintain the spot size, the system uses chromatic focusing with wavelength modulation to dynamically control the focal volume, eliminating the need for complex waveguide structures while maintaining small spot sizes over long distances
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
Enables unprecedented spatiotemporal control over the laser's focal volume, allowing the focus to co- or counter-propagate at various velocities, generating a nearly constant peak intensity over extended distances and overcoming limitations in laser-plasma interactions and amplifiers.
Implementation Method 1
The chromatic lens system may include a diffractive lens. The diffractive lens may have a radially varying groove density... The chromatic lens system may include a chromatic refractive lens... where the chromatic lens system has a longitudinal dispersion given by
Implementation Method 2
The chromatic lens system may include a diffractive lens. The diffractive lens may have a radially varying groove density
Implementation Method 3
The chromatic lens system may include a chromatic refractive lens
Data Source
AI summary
Methods and systems are disclosed for using a chromatic lens system to provide a “flying focus”—i.e., an advanced focusing scheme enabling spatiotemporal control of a focal location. In a method, a photon beam is emitted from a source at a wavelength. The photon beam may have more than one wavelength. The photon beam is focused to a focal location using a chromatic lens system. The focal location is at a first longitudinal distance along an optical axis from the chromatic lens system. The wavelength of the photon beam is changed as a function of time to change the focal location as a function of time. The wavelength may be changed such that the focal location changes with a focal velocity.