Chirped Pulse Frequency Conversion With Full-Band Phase Matching
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Solution Overview
Problem
Existing non-linear optical processes face inefficiencies in achieving phase-matching conditions for broad spectral bandwidths of chirped pulses, particularly when the interacting pulses are not harmonically related or have unequal chirp rates.
Innovation Solution
An optical system and method that involves over-compressing one pulse to reverse its chirp direction, adjusting chirp rates, and synchronizing pulses to ensure phase-matching at every constituent frequency by spatially and temporally overlapping beams in a non-linear optical medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If linearly chirped IR laser pulses with broad spectral bandwidth are used for frequency conversion, then the spectral content can be expanded to various ranges, but the phase-matching condition in the non-linear medium is not satisfied for various frequencies present in the spectral bandwidth
Solution Approach 1:
The patent applies inverse chirp to one of the interacting pulses. Specifically, if one pulse has a positive chirp rate (frequency increases with time), the other pulse is given a negative chirp rate (frequency decreases with time) of equal magnitude. This inversion of chirp direction allows the sum of frequencies at any given time to remain substantially constant, satisfying the phase-matching condition across the entire spectral bandwidth while enabling broad spectral content expansion through non-linear optical processes
2Adaptability or versatility
If the spectral bandwidth of input laser beam is broad, then frequency conversion to various spectral ranges is enabled, but the efficiency of generation of optical harmonics is limited
Solution Approach 1:
By applying inverse chirp to one of the input pulses, the patent ensures that the sum of instantaneous frequencies remains constant throughout the pulse duration. This maintains the phase-matching condition across the entire broad spectral bandwidth, enabling efficient harmonic generation throughout the spectrum rather than only at specific frequencies, thus resolving the contradiction between broad bandwidth capability and generation efficiency
3Reliability
If non-collinear interaction of two beams with equal magnitude chirp rates of opposite signs is used, then phase-matching is achieved at any given time, but the solution is too specific and does not address general cases where pulses are not harmonically related or chirp rates are not equal
Solution Approach 1:
The patent generalizes the inverse chirp approach by allowing the chirp rates to differ in magnitude while maintaining opposite signs. The system accepts input pulses with any chirp rates (not necessarily equal), applies inverse chirp transformation, and achieves phase-matching for sum-frequency generation. This parameter-based generalization enables the solution to work for non-harmonically related pulses and various practical situations beyond the specific case of equal magnitude chirp rates
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 efficient phase-matching for non-linear frequency conversion across the entire spectral bandwidth, ensuring complete phase-matching and enhanced conversion efficiency.
Implementation Method 1
an input non-linear optical medium positioned across an input axis and configured to receive and transform, in transmission therethrough, a portion of light carried by first chirped pulses of light (at a first nominal wavelength) into second chirped pulses of light at a second nominal wavelength
Implementation Method 2
a pulse compressor system including at least one pulse compressor that is configured to receive one chosen of the first chirped and second chirped pulses of light but not the other of these first chirped and second chirped pulses of light and to over-compress such chosen pulse of light to form, at an output of the pulse compressor system, over-compressed chirped pulse of light having a chirp direction opposite to that of the first chirped pulse of light
Implementation Method 3
configured to ensure that a phase-matching condition is satisfied for and at substantially every constituent optical frequency present within the bandwidths of non-linearly interacting chirped pulses of light
Data Source
AI summary
Methodology of ensuring that a phase-matching condition for non-linear interaction between constituent optical waves interacting with one another in a non-linear medium is satisfied for and at substantially every frequency (or wavelength) of the spectral bandwidths of such optical waves, thereby increasing the efficiency of the non-linear process.