T-Shaped Laser Pumping Assembly With Fluorescent TIR Coupling
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Solution Overview
Problem
Existing LED-pumped laser systems face challenges in achieving sufficient power density for pumping certain laser media due to limitations in light intensity and inefficient optical coupling, particularly in transverse pumping configurations, leading to reduced gain and potential optical damage.
Innovation Solution
A laser pumping assembly is designed with a fluorescent concentrator arranged perpendicular to the laser medium, utilizing trapped radiation by total internal reflection to increase volumetric pump power density, and incorporating specific geometric and refractive index configurations to enhance optical coupling and reduce laser medium thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional LED-pumped concentrator is used for transverse pumping, then the illumination is improved compared to direct LED pumping, but the illumination remains low compared to laser diodes and the geometry requires the concentrator to be very close to the laser medium without intermediate optics
Solution Approach 1:
The patent transitions from transverse pumping to longitudinal pumping geometry, fundamentally changing the spatial arrangement. The concentrator is positioned at the end face of the laser medium rather than on the side, allowing the laser beam to propagate through the concentrated light from the concentrator, eliminating the need for intermediate optics and simplifying the overall device geometry
Solution Approach 2:
The patent introduces a reflective coating on the exit face of the concentrator to redirect trapped rays into the laser medium. This intermediary reflective surface enables efficient coupling of the concentrated light into the laser medium without requiring the concentrator to be in direct contact with the medium, thus simplifying the geometric constraints
2Power
If the laser beam is positioned close to the pump inlet surface to maximize absorption, then the gain is improved, but diffraction effects at the edge of the crystal create losses and distortions in the laser beam
Solution Approach 1:
By switching to longitudinal pumping geometry, the patent allows the laser beam to propagate collinearly with the pump light through the concentrator. This eliminates the transverse positioning problem where the beam must be offset from the pump inlet, thereby avoiding edge diffraction effects while maintaining maximum absorption along the entire beam path
Solution Approach 2:
The reflective coating on the concentrator exit face is applied in advance to redirect trapped rays into the laser medium before the laser beam enters. This preliminary optical conditioning ensures that the beam receives maximum concentrated light without encountering edge diffraction issues that would occur with transverse pumping
3Object-affected harmful factors
If the laser beam diameter is increased to avoid optical damage threshold, then the gain is reduced due to lower absorption
Solution Approach 1:
The patent changes the pumping geometry from transverse to longitudinal, which fundamentally alters the absorption profile. In longitudinal pumping, the beam propagates through the concentrated light along its entire path, maintaining high absorption efficiency even for large beam diameters. The reflective coating on the concentrator exit face further enhances this by redirecting trapped rays into the beam path, ensuring uniform pumping across the entire beam cross-section without edge effects
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 significantly enhances the volumetric pump power density and amplification capabilities, allowing for higher gain and reduced optical damage, while maintaining efficient optical coupling and beam confinement.
Implementation Method 1
a fluorescent parallelepiped crystal called a concentrator... being configured to absorb said electroluminescent radiation and emit fluorescence radiation
Implementation Method 2
The concentrator is configured to absorb the electroluminescent radiation Ld emitted by the LEDs
Implementation Method 3
a portion of said fluorescence radiation trapped in the concentrator by total internal reflection can pass into the laser medium... and be trapped in the laser medium by total internal reflection
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
Laser pumping assembly (1) comprising: - a solid rectangular laser medium (ML) having a plate shape in a horizontal plane (xy) and a thickness e L , the laser medium having a spectral absorption band and an associated absorption coefficient α; - at least one light emitting module (ME) for pumping the laser medium comprising a fluorescent rectangular crystal referred to as a concentrator (CL), having a plate shape with thickness e c , the concentrator having at least one illumination surface (SI1, SI2) illuminated by electroluminescent radiation (Ld) and being configured to absorb the electroluminescent radiation (Ld) and emit fluorescent radiation in a spectral range that overlaps with the spectral absorption band, the concentrator having an emitting surface (SE); the concentrator being in optical contact, through the emitting surface (SE), with a receiving surface (SR, SR1, SR2) of the laser medium, the concentrator being arranged perpendicular to the laser medium such that the illuminating surface(s) (SI1, SI2) are perpendicular to the receiving surface so as to carry out a transverse pumping of the laser medium, the optical contact being designed so that a portion (Lg) of the fluorescent radiation trapped in the concentrator (CL) by total internal reflection can pass into the laser medium (ML), by crossing the emitting surface (SE), and be trapped in the laser medium ML by total internal reflection, the thickness e L of the laser medium being such that e L ≤ L abs /5 with L abs = 1/α an absorption length of the laser medium.