Frequency Conversion System Pump Beam Recycling
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Solution Overview
Problem
Current frequency conversion systems face limitations in angular acceptance and conversion efficiency, making them unsuitable for high-resolution imaging and detection applications, as they typically have low angular acceptance and poor conversion efficiency due to phase mismatch and depletion of the pump beam.
Innovation Solution
A frequency conversion system that recycles the pump beam by redirecting it multiple times through a nonlinear crystal, using a configuration of optical components to maintain quasi-phase matching and increase the angular acceptance, allowing for efficient conversion of infrared signals to visible or near-infrared frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single pump beam is used in traditional frequency conversion systems, then the system structure is simple, but the angular acceptance is limited and conversion efficiency is poor
Solution Approach 1:
The single pump beam is segmented into multiple elementary pump beams (at least two) with different propagation directions. Each elementary pump beam interacts with the nonlinear crystal to convert signal beams from different angles, thereby expanding the overall angular acceptance of the system without requiring complex additional components
Solution Approach 2:
The system transitions from a single propagation direction to multiple propagation directions by introducing elementary pump beams with different angles. This dimensional expansion in angular space allows the system to accept signal beams over a broader angular range while maintaining quasi-phase matching conditions
2Productivity
If the pump beam passes through the crystal once, then the system is simple, but the conversion efficiency is limited due to pump beam depletion
Solution Approach 1:
The pump beam is recycled to pass through the nonlinear crystal multiple times (at least two passes) instead of a single pass. This continuous utilization of the pump beam maintains higher conversion efficiency by preventing pump beam depletion, as the pump beam interacts with the crystal repeatedly to convert signal beams
Solution Approach 2:
Instead of discarding the pump beam after a single pass, the system recycles the pump beam by redirecting it back through the nonlinear crystal using optical components. This recovery and reuse of the pump beam maximizes its utility and maintains high conversion efficiency throughout the process
3Ease of operation
If traditional phase matching is used, then the system structure is simple, but the angular acceptance is less than 1 degree which limits detection field
Solution Approach 1:
The phase matching approach is segmented from a single collinear configuration to multiple non-collinear configurations. By using at least two elementary pump beams with different propagation directions, the system achieves quasi-phase matching for multiple angles simultaneously, expanding angular acceptance beyond the traditional less than 1 degree limitation
Solution Approach 2:
The system changes the propagation direction parameters of the pump beams from a single fixed angle to multiple variable angles. By adjusting the propagation directions of elementary pump beams, the system achieves quasi-phase matching conditions for a broader range of signal beam angles, thereby expanding the detection field
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 system significantly enhances angular acceptance and conversion efficiency, enabling the detection of a broader range of signal angles with improved resolution and sensitivity, overcoming the limitations of traditional systems.
Implementation Method 1
The crystal CR includes a material M in which the sign of the second-order nonlinear coefficient is periodically reversed along a Z-axis, said crystal CR being configured such that the conversion occurs by a second-order nonlinear effect in said crystal CR
Implementation Method 2
The first and second optical components ROC1, ROC2 are configured to reflect at least part of the plurality of elementary pump beams
Data Source
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AI summary
The invention concerns a frequency conversion system (10) suitable for generating at least one converted beam (Fc) having a converted frequency (vc) from at least one signal beam (Fs) having a signal frequency (vs), by using a plurality of n elementary pump beams Fp,i indexed i, i varying from 1 to n, n being greater than or equal to 2, having a pump frequency (vp), the system comprising: - a crystal (CR) comprising a material (M) for which the sign of the second order non-linear coefficient (χ(2)) is periodically inverted along an axis Z - an optical device (OD) configured to generate said plurality of n elementary pump beams from an initial pump beam (Fpini), an elementary pump beam Fp,i+1 of index i+1 being generated by redirecting the elementary pump beam Fp,i of index i toward the crystal after it has crossed the crystal.