BBO UV Light Source Temperature Feedback for Phase Matching Stability
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Solution Overview
Problem
The challenge is to maintain stable and high-power UV light generation in inspection apparatuses using BBO crystals, as self-heating and optical damage lead to unstable phase matching conditions, making it difficult to continuously maximize UV light output due to the crystal's poor thermal conductivity and birefringent properties.
Innovation Solution
A light-source apparatus with a BBO crystal and a semiconductor sensor to calculate the representative position of the light intensity distribution, allowing for precise temperature adjustment to maintain optimal phase matching, combined with a method to control the temperature of the BBO crystal to stabilize UV light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-power UV light is generated continuously by a BBO crystal, then the UV light output power is improved, but the phase matching condition becomes unstable due to self-heating and optical damage
Solution Approach 1:
The patent implements dynamic temperature adjustment of the BBO crystal by introducing a temperature control mechanism that actively responds to changes in phase matching conditions. The system continuously monitors and adjusts the crystal temperature to maintain optimal phase matching during continuous high-power UV operation, counteracting the destabilizing effects of self-heating and optical damage.
2Reliability
If the BBO crystal temperature is precisely controlled to maintain phase matching, then the UV light output stability is improved, but the system complexity increases due to temperature control mechanisms
Solution Approach 1:
The patent employs a feedback control mechanism where the temperature of the BBO crystal is continuously monitored and adjusted based on the actual UV light output or phase matching condition measurements. This closed-loop feedback system automatically compensates for temperature drifts caused by self-heating, maintaining stable UV output without requiring overly complex external temperature control infrastructure.
3Productivity
If angular phase matching is used to generate UV light, then the wavelength conversion efficiency is improved, but the crystal temperature must be precisely controlled which becomes difficult under continuous operation
Solution Approach 1:
The patent utilizes temperature phase matching as an alternative to angular phase matching, where the phase matching condition is achieved and maintained by controlling the crystal temperature rather than the incident angle. This approach allows for more stable and automated temperature control through heating/cooling mechanisms, improving ease of operation during continuous high-power UV generation while maintaining high wavelength conversion efficiency.
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 solution enables continuous maximization of UV light output by stabilizing the phase matching condition, even when the BBO crystal is spatially translated, and allows for long-term stable operation of the UV light source.
Implementation Method 1
a BBO crystal disposed in a first external resonator, capable of generating UV light in a wavelength range of 233 nm to 236 nm, the UV light being a second harmonic of the visible light
Implementation Method 2
the temperature phase matching is a method in which the temperature of a crystal is adjusted by using a Peltier element or the like
Data Source
AI summary
A light-source apparatus, an inspection apparatus, and an adjustment method capable of facilitating the adjustment of the temperature of a BBO crystal are provided. A light-source apparatus according to the present disclosure includes a first light source configured to generate visible light, a first external resonator including a plurality of optical mirrors, a BBO crystal disposed in the first external resonator, capable of generating UV light in a wavelength range of 233 nm to 236 nm, the UV light being a second harmonic of the visible light, a one- or two-dimensional semiconductor sensor disposed near a far-field image plane formed through an optical element provided on an optical path of the UV light, and a calculation unit configured to calculate a representative position of a light intensity distribution detected by the semiconductor sensor.