Laser Frequency Conversion Device with Angular Beam Deflection
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Solution Overview
Problem
Third harmonic generation using non-linear crystals faces challenges with 'walk-off' of laser beams, which complicates high conversion efficiency due to the inability to achieve non-critical phase matching, leading to inefficient use of crystal volume and requiring complex adjustments in existing devices.
Innovation Solution
A device with two optically non-linear crystals in series, where an optical deflection device adjusts the relative beam position to an angle before entering the second crystal, ensuring collinear phase matching and optimizing overlap, allowing for efficient frequency conversion and extended crystal utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If non-critical phase matching is used in the second non-linear optical crystal, then collinear propagation of laser beams is achieved, but third harmonic generation is not possible with available crystals
Solution Approach 1:
Instead of attempting to achieve non-critical phase matching (which is impossible with available crystals for THG), the invention inverts the approach by deliberately using critical phase matching and accepting the walk-off effect. The key innovation is then to compensate for this walk-off by adjusting the crystal orientation and beam geometry to achieve optimal overlap of the fundamental and second harmonic beams throughout the crystal length.
2Adaptability or versatility
If critical phase matching is used in the second non-linear optical crystal, then third harmonic generation is enabled, but walk-off of laser beams occurs reducing conversion efficiency
Solution Approach 1:
The invention changes the geometric parameters of the system by introducing a specific angle of incidence for the laser beams at the crystal entrance surface. This angular parameter adjustment, combined with appropriate crystal orientation, compensates for the walk-off effect by ensuring that the beams remain overlapped throughout the crystal, thereby maintaining high conversion efficiency despite using critical phase matching.
3Ease of operation
If laser beams are arranged to impinge perpendicularly and spaced apart on the entrance surface, then simple alignment is achieved, but beam overlap is insufficient for efficient third harmonic generation
Solution Approach 1:
The invention introduces asymmetry in the beam arrangement by using different angles of incidence for the fundamental and second harmonic beams. Instead of symmetric perpendicular incidence, the beams are directed at specific asymmetric angles that compensate for the walk-off effect, ensuring optimal overlap throughout the crystal while maintaining practical alignment procedures.
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 configuration optimizes the performance by allowing for simple adjustment of beam overlap, increased crystal utilization, and the use of smaller, more cost-effective crystals, while maintaining high conversion efficiency and minimizing 'walk-off' effects.
Implementation Method 1
an optically non-linear first crystal for generating a second laser beam having a second frequency, which differs from the first frequency
Implementation Method 2
an optically non-linear second crystal, which generates from the first and second laser beams at least one third laser beam having a third frequency, which differs from the first frequency and the second frequency
Data Source
AI summary
A device for frequency conversion of a first laser beam generated with a first frequency. The device has a first crystal for generating a second laser beam having a second frequency, which differs from the first frequency. The second laser beam propagates parallel to the first laser beam after leaving the first crystal. A second crystal, which generates from the first and second laser beams a third laser beam having a different third frequency. An optical deflection device influences the relative beam position between first and second laser beams such that the first and second laser beams, before entering into the second crystal, propagate at an angle with respect to one another, which angle differs from zero, and enter in a manner spaced apart from one another at an entrance surface of the second crystal and intersect within the second crystal with at the same time collinear phase matching.