Frequency-Tripled Laser Generation via Single Resonator
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Solution Overview
Problem
Existing methods for generating frequency-tripled laser radiation are inefficient due to losses in separate optical resonators and polarization adjustments, especially when trying to achieve high nonlinear conversion efficiency in the ultraviolet spectral region.
Innovation Solution
A method where a first laser radiation at a fundamental frequency is coupled into a single optical resonator, with a first nonlinear optical crystal for second-harmonic generation and a second nonlinear optical crystal for sum frequency generation, both within the same resonator, and a polarization adjusting element outside the resonator rotates the polarization direction of the frequency-doubled radiation for efficient sum frequency generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate optical resonators are used for SHG and SFM processes, then polarization rotation can be achieved, but losses occur in both optical resonators due to mode and impedance matching
Solution Approach 1:
The patent merges the SHG and SFM processes into a single optical resonator, eliminating the need for separate resonators and their associated losses. The resonator is designed to support both the fundamental frequency and the frequency-doubled radiation, allowing both nonlinear processes to occur within one cavity while maintaining resonance enhancement.
Solution Approach 2:
The patent extracts the polarization rotation function from the optical resonator system and implements it using waveplates placed outside the resonator. This separates the polarization control function from the resonant enhancement function, allowing the resonator to operate with minimal losses while still achieving the necessary polarization rotation for type-I to type-II process conversion.
2Ease of operation
If passive losses occur in two separate mirror arrangements, then polarization adjustment is possible, but overall efficiency is reduced
Solution Approach 1:
The patent combines the mirror arrangements into a single set of mirrors that define one optical resonator cavity. This single mirror arrangement supports both the fundamental frequency and the frequency-doubled radiation, eliminating the passive losses that would occur in two separate mirror arrangements while maintaining the ability to adjust polarization through waveplates.
3Ease of operation
If beam diameters are large compared to walk-off, then walk-off effect is negligible, but nonlinear conversion efficiency is reduced
Solution Approach 1:
The patent changes the operating parameters by using resonant enhancement within a single optical resonator to achieve high conversion efficiency with smaller beam diameters. The resonant buildup of intracavity power compensates for the walk-off effect, allowing efficient nonlinear conversion even when beam diameters are comparable to or smaller than the walk-off distance.
4Ease of operation
If waveplates are used for polarization rotation, then polarization direction can be changed, but losses occur in the waveplates
Solution Approach 1:
The patent extracts the polarization rotation function from the resonator cavity and implements it using waveplates placed in the input or output paths outside the resonator. This positioning minimizes the impact of waveplate losses on the overall system efficiency, as the waveplates only affect the input or output beams rather than the resonantly enhanced intracavity 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
This approach significantly reduces losses and achieves efficient generation of frequency-tripled laser radiation, particularly in the deep ultraviolet region, with improved power efficiency by using a single resonator and minimizing losses through careful polarization rotation and dichroic mirror configurations.
Implementation Method 1
a first nonlinear optical crystal, which is located in the optical resonator and converts part of a first laser radiation, which is generated by means of a suitable laser, in particular no more than 30% of the circulating power, to a second frequency-doubled laser radiation by second-harmonic generation in a type-I process
Implementation Method 2
a second nonlinear optical crystal, which is likewise located in the resonator, behind the first nonlinear optical crystal in the beam path and which converts at least part of the first and second laser radiations to a third, frequency-tripled laser radiation by sum frequency generation in a further type-I process
Implementation Method 3
a first laser radiation at a fundamental frequency is provided and coupled into an optical resonator, which is resonant at the fundamental frequency
Implementation Method 4
a polarization adjusting element outside the optical resonator rotates the polarization direction of the second laser radiation, preferably by an angle of substantially 90°, particularly preferably by an angle between 70° and 110°
Data Source
AI summary
The invention relates to a method of generating frequency-tripled laser radiation (THG). It is the object of the invention to demonstrate an efficient approach to generating frequency-tripled laser radiation. The method according to the invention comprises the following method steps:providing a first laser radiation at a fundamental frequency,coupling the first laser radiation into an optical resonator, which is resonant at the fundamental frequency,generating a second laser radiation by second-harmonic generation of the first laser radiation in a type-I process in a first nonlinear optical crystal (3), which is located in the optical resonator, wherein the second laser radiation has a polarization direction,rotating the polarization direction of the second laser radiation, preferably by an angle of substantially 90°, andgenerating a third laser radiation by generating the sum frequency of the first and second laser radiations in a type-I process in a second nonlinear optical crystal (9), which is likewise located in the optical resonator.The invention also relates to a device for generating frequency-tripled laser radiation.