Reflective Polarizing Beam Splitter Twist for Stable Fiber Oscillation
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Solution Overview
Problem
The existing light sources, such as those described in PTL 3, face challenges in starting and maintaining stable laser oscillation due to accidental nonlinear polarization rotation and sensitivity to disturbances like temperature and external pressure, leading to unstable light-emitting characteristics and potential sudden cessation of laser oscillation.
Innovation Solution
An optical fiber output light source device is configured with a polarization maintaining amplifying optical fiber joined to a polarization maintaining dispersion compensating fiber, a single-polarization reflective polarizing beam splitter, and a 90° polarization-rotating reflector, with a multiplexer and a pumping light source, where the polarization axis of the beam splitter is twisted by a predetermined angle relative to the fiber's polarization maintaining axis to ensure stable nonlinear polarization rotation for sustained oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional light source (halogen lamp) is used to obtain a white light source, then the device structure is simple, but high light output cannot be achieved due to limited luminance from the filament surface
Solution Approach 1:
The patent replaces the conventional halogen lamp (thermal radiation source) with a fiber laser system that uses optical pumping and stimulated emission. The fiber laser core is doped with rare-earth elements and pumped by a semiconductor laser, transforming the light generation mechanism from thermal to quantum mechanical processes, thereby achieving high light output while maintaining a relatively simple device structure
Solution Approach 2:
The patent changes the fundamental parameters of the light source by using a fiber laser with rare-earth element doping. This allows the system to operate in a regime where stimulated emission dominates, producing high-intensity light with a narrow spectrum that can be amplified to achieve the desired output power, overcoming the luminance limitation of conventional filament-based sources
2Power
If a fiber laser is used to achieve high light output, then high light output is achieved, but the spectrum width is narrow and cannot substitute for a white light source
Solution Approach 1:
The patent merges multiple fiber laser units with different emission spectra into a single system. Each fiber laser core is doped with different rare-earth elements or has different doping concentrations, producing lasers with different characteristic wavelengths. By combining these multiple narrow-spectrum lasers, the system achieves a broad overall spectrum covering the visible range, thus functioning as a white light source while maintaining high output power
Solution Approach 2:
The patent uses composite doping of rare-earth elements in the fiber laser core. By incorporating multiple rare-earth elements (such as Er, Tm, Ho, Nd) with different emission characteristics into the same or different fiber cores, the system creates a composite light source that combines the spectral advantages of each element, achieving both high power output and broad spectrum coverage
3Device complexity
If an ASE light source is used, then the device structure is simple, but the fiber output is not sufficiently high for use as a white light source
Solution Approach 1:
The patent replaces the ASE (amplified spontaneous emission) mechanism with a stimulated emission-based fiber laser system. While ASE relies on spontaneous emission that is then amplified, the fiber laser uses optical pumping to create a population inversion and generates light through stimulated emission, which is a more efficient process. This substitution dramatically increases the fiber output power while maintaining a relatively simple device structure consisting of the doped fiber, pump source, and basic optical components
4Adaptability or versatility
If a super continuum light source is used to achieve broadband emission, then a spectrum width of one octave or more is achieved, but the light source is unstable due to fluctuation of incident pulses and nonlinear optical effect
Solution Approach 1:
The patent extracts and eliminates the unstable nonlinear optical conversion stage from the system. Instead of using a super continuum light source that requires intense pulsed laser excitation of nonlinear optical media (which causes instability due to pulse fluctuation), the invention directly generates the desired broadband spectrum through multiple fiber lasers with different rare-earth element dopings. This removes the source of instability while maintaining the broadband spectral coverage
Solution Approach 2:
The patent performs preliminary spectral diversification by using multiple fiber laser cores doped with different rare-earth elements before the light needs to be combined. Each laser is independently pumped and generates its characteristic spectrum. By preparing these different spectral components separately and then combining them, the system achieves broadband output without requiring unstable nonlinear optical processes, thereby improving reliability
5Device complexity
If the polarization axis of the beam splitter is aligned with the fiber's polarization maintaining axis, then the configuration is simple, but stable nonlinear polarization rotation cannot be ensured and laser oscillation may cease suddenly
Solution Approach 1:
The patent introduces an asymmetric angular relationship between the polarization axis of the polarizing beam splitter and the polarization maintaining axis of the fiber. Specifically, the polarization axis is set at a predetermined angle (e.g., 45 degrees) relative to the fiber's polarization maintaining axis. This asymmetric configuration ensures that nonlinear polarization rotation can occur stably, preventing sudden cessation of laser oscillation while adding only minimal complexity to the overall system configuration
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 enables stable and long-lasting broadband short pulses generation, eliminating the need for polarization control adjustments and maintaining oscillation despite disturbances, resulting in a stable and high-intensity broadband light source.
Implementation Method 1
an optical path that is obtained by joining a polarization maintaining amplifying optical fiber to a polarization maintaining dispersion compensating fiber
Implementation Method 2
a polarization maintaining dispersion compensating fiber
Implementation Method 3
a single-polarization reflective polarizing beam splitter that is joined to one end of the optical path
Implementation Method 4
a single-polarization reflective polarizing beam splitter
Implementation Method 5
a 90° polarization-rotating reflector that is joined to the other end of the optical path
Implementation Method 6
a multiplexer that is inserted in the optical path
Implementation Method 7
a pumping light source that is joined to the multiplexer
Data Source
AI summary
An optical fiber output light source device includes an optical path that is obtained by joining a polarization maintaining amplifying optical fiber to a polarization maintaining dispersion compensating fiber, a single-polarization reflective polarizing beam splitter that is joined to one end of the optical path, a 90° polarization-rotating reflector that is joined to the other end of the optical path, a multiplexer that is inserted in the optical path, and a pumping light source that is joined to the multiplexer. An axis roll connection portion is provided in which a polarization axis of light returned from the single-polarization reflective polarizing beam splitter to the optical path is connected to a polarization maintaining axis of the optical path with a twisting angle therebetween at a predetermined angle.