VECSEL Second Harmonic Generation Using Volume Bragg Grating
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Solution Overview
Problem
Conventional VECSEL systems face challenges in achieving high wavelength conversion efficiency due to the large Full-Width at Half Maximum (FWHM) of laser light, which is not adequately reduced by increasing the thickness of the birefringence filter and heat spreader, leading to increased material costs and optical loss.
Innovation Solution
Incorporating a reflective Volume Bragg Grating (VBG) as an optical element that forms a cavity with the reflector, reducing the FWHM of laser light to less than 0.2 nm, and using a polarization control plate at a Brewster's angle to enhance wavelength conversion efficiency, while also reducing the size and cost of the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the birefringence filter and heat spreader is increased to reduce the FWHM of laser light, then the wavelength conversion efficiency of the SHG device is improved, but the material costs and optical loss increase
Solution Approach 1:
The patent changes the optical path length parameter by introducing a folded optical path using mirrors. This allows the laser light to traverse the SHG crystal multiple times (effectively increasing the interaction length) without physically increasing the thickness of the birefringence filter or heat spreader, thereby achieving high wavelength conversion efficiency while avoiding the associated optical losses and material costs
Solution Approach 2:
Instead of increasing thickness in one dimension (which causes optical loss), the patent uses mirrors to extend the optical path in a different dimension (spatial folding). The laser beam is reflected back through the SHG crystal multiple times, effectively increasing the conversion length without increasing the physical thickness of the filter or heat spreader
2Manufacturing precision
If the thickness of the birefringence filter and heat spreader is increased to reduce the FWHM of laser light, then the wavelength conversion efficiency of the SHG device is improved, but the material costs increase
Solution Approach 1:
The patent modifies the optical path length parameter through geometric folding using mirrors, allowing multiple passes through the SHG crystal without increasing the thickness of expensive components like the birefringence filter. This achieves high conversion efficiency while controlling material costs
Solution Approach 2:
Mirrors are introduced as intermediary elements to extend the optical path. These mirrors enable the laser light to interact with the SHG crystal multiple times without requiring thicker, more expensive birefringence filters or heat spreaders
3Manufacturing precision
If conventional VECSEL systems use standard optical components to reduce FWHM, then the linewidth is reduced to some extent, but the system size and complexity increase
Solution Approach 1:
The mirrors in the patent serve multiple functions: they extend the optical path length, fold the beam path to maintain compact size, and enable multiple passes through the SHG crystal. This multi-functionality achieves FWHM reduction and high conversion efficiency without significantly increasing system complexity
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 solution achieves high wavelength conversion efficiency for the SHG device, allowing for the generation of high power visible laser light with reduced manufacturing costs and easier alignment of optical components, while maintaining a compact system design.
Implementation Method 1
a SHG device that is disposed between the laser device and the optical element and doubles the frequency of laser light
Implementation Method 2
Incorporating a reflective Volume Bragg Grating (VBG) as an optical element that forms a cavity with the reflector, reducing the FWHM of laser light to less than 0.2 nm
Implementation Method 3
using a polarization control plate at a Brewster's angle to enhance wavelength conversion efficiency
Implementation Method 4
The VECSEL device 18 further includes a heat spreader 13 dissipating heat generated in the active layer in order to cool the active layer
Implementation Method 5
a birefringence filter 14 that is disposed in an optical path between the first mirror 15 and the VECSEL device 18
Data Source
AI summary
A Vertical External Cavity Surface Emitting Laser (VECSEL) system is provided. The VECSEL system includes a laser device including an active layer in which laser light is generated by pumping and a reflector reflecting the laser light generated in the active layer; an optical element that forms a cavity together with the reflector of the laser device and reduces a line width of laser light; and a SHG (Second Harmonic Generation) device that is disposed between the laser device and the optical element and doubles the frequency of laser light.