Multi-Clad Upconversion Fiber Laser for High-Power ROGB Output
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Solution Overview
Problem
Existing methods for generating red, green, and blue lasers face limitations such as high operating costs, instability, and power scaling issues, particularly in single-clad rare earth ion doped fluoride-glass fibers, which restrict the production of high-power, stable, and cost-effective multicolor visible laser light for applications like projection displays.
Innovation Solution
The development of a diode-pumped upconversion fiber laser using multiple-clad fibers with large-mode-area cores and a polymer-protected outer cladding, combined with semiconductor laser pumping, allows for high-power excitation and efficient multicolor laser generation, maintaining single-mode operation and reducing thermal effects, while using a holey fiber structure for enhanced light confinement and reduced propagation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If single-clad rare earth ion doped fluoride-glass fibers are used for upconversion laser generation, then the laser can operate at visible wavelengths with compact structure, but the power scaling is severely limited due to low melting point and coupling losses
Solution Approach 1:
The fiber structure is segmented into multiple cladding layers: inner cladding for pump light confinement and outer cladding for mechanical protection. This segmentation allows the pump light to be confined to a smaller core area for high power density while the outer cladding provides structural stability and protects against damage from high power operation.
Solution Approach 2:
The patent uses composite fiber structure combining fluoride glass core with silica-based outer cladding. The fluoride glass core provides the necessary optical properties for upconversion at visible wavelengths, while the silica outer cladding provides mechanical strength and thermal stability, enabling high power operation without compromising reliability.
2Power
If larger fiber core diameter is used to reduce pump power density for power scaling, then pump power can be increased, but multimode operation occurs reducing beam quality
Solution Approach 1:
The fiber design implements local quality differentiation through the double-clad structure: the inner cladding region maintains small effective area for single-mode pump light confinement, while the outer cladding provides larger overall diameter for mechanical strength. This allows high pump power to be delivered while maintaining the optical confinement necessary for single-mode operation and high beam quality.
3Device complexity
If conventional single-step optical pump process is used, then the system is simpler, but the laser emission always exhibits lower photon energy (longer wavelength) compared to pump light
Solution Approach 1:
The upconversion process utilizes continuous absorption of multiple pump photons by rare earth ions in the excited state, converting lower energy pump photons into higher energy visible laser photons. This continuous multi-photon absorption process enables sustained high photon energy output without requiring complex frequency conversion components, maintaining system simplicity while achieving the desired wavelength conversion.
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 enables the production of stable, high-power, compact, and low-cost Red, Orange, Green, Blue (ROGB) fiber lasers with improved beam quality and power scaling, suitable for applications like biotech instrumentation and color projection displays, achieving efficient multicolor visible laser output with controlled power balance.
Implementation Method 1
the upconversion pump process is a multi-step process, in which more than one photons excite one active ion to the upper laser level and the laser light usually has a shorter wavelength than the pump light has
Implementation Method 2
Common upconversion processes include excited-state absorption of a second photon by the active ion, also called 'two-step absorption'
Implementation Method 3
dipole-dipole cross-relaxation interactions between two excited ions
Implementation Method 4
Light can be confined within this type of fiber by two distinct mechanisms. First, light guidance can be obtained through a fiber with periodically arranged air holes by photonic band gap effects.
Implementation Method 5
a double clad fiber structure having a single mode core doped with rare earth ions and a surrounded inner cladding with a refractive index lower than the core index
Data Source
AI summary
An all-fiber device platform for producing high-power ROGB or RGB laser output comprises an optical fiber including multiple waveguide gain regions embedded within a common inner cladding and within an outer cladding, an optical cavity defined by dielectric reflectors and/or FBG mirrors, and a pump source for exciting one or more active ionic species by one or multiple pump wavelengths from one or both ends of the optical fiber through upconversion process. An apparatus for producing sequential or simultaneous multiple wavelength laser operation provides for applications of color projection displays and biomedical or other instrumentation.