Diode Laser System Fiber Filtering
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Solution Overview
Problem
Laser-based fluorescence instruments face challenges in achieving precise alignment and stability of combined laser beams, and existing filter-based systems suffer from transmission losses and limited switching speed, especially when using diode lasers which can emit undesirable LED light below their lasing threshold.
Innovation Solution
The system employs diode lasers with their outputs directly controlled and coupled into optical fibers, where the fiber acts as a filtering mechanism to eliminate LED emission, allowing for precise control and modulation of the laser beams without the need for additional filters, enabling extended wavelength range and faster switching speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If filters are used to select and control laser lines, then wavelength selection capability is improved, but transmission losses increase (order of 20%)
Solution Approach 1:
The patent extracts the unwanted LED emission component from the diode laser output by operating below threshold and using the optical fiber's inherent filtering properties, eliminating the need for additional filters that would cause transmission losses. This allows full laser power transmission while achieving wavelength purity.
Solution Approach 2:
The optical fiber acts as an intermediary element that provides passive spectral filtering between the diode laser and the fluorescence instrument. The fiber's modal properties naturally filter out LED emission while transmitting the desired laser wavelength, avoiding the need for active filter components.
2Adaptability or versatility
If filters are used for laser line selection, then wavelength control is improved, but switching speed is limited
Solution Approach 1:
The patent employs dynamic control of the diode laser operating point, allowing rapid switching between lasing and LED emission modes by modulating the drive current. This electronic control mechanism enables nanosecond-scale switching speeds, far exceeding mechanical or filter-based approaches.
Solution Approach 2:
The patent replaces mechanical or optical filter-based wavelength selection with electronic control of the diode laser's emission mode. By using electrical current modulation instead of physical filter movement or switching, the system achieves dramatically faster response times.
3Object-affected harmful factors
If diode lasers are operated below threshold to avoid LED emission, then LED interference is reduced, but laser power output is limited
Solution Approach 1:
The patent converts the typically harmful LED emission into a useful filtering mechanism. By operating below threshold where LED emission dominates, the system exploits the optical fiber's ability to filter spatial modes, transforming the LED contamination problem into a passive spectral purification approach that enables full power operation without filter losses.
Solution Approach 2:
The patent changes the operating parameters of the diode laser, specifically operating below the lasing threshold rather than above it. This parameter change fundamentally alters the emission characteristics, allowing the system to use the fiber's modal filtering to achieve both high power output and spectral purity simultaneously.
4Device complexity
If direct coupling of combined laser beams is used, then system complexity is reduced, but alignment precision and stability deteriorate
Solution Approach 1:
The patent introduces an optical fiber as an intermediary coupling element between the combined laser beams and the fluorescence instrument. This fiber acts as a stable transmission medium that is insensitive to alignment variations, eliminating the precision alignment requirements of direct free-space coupling while maintaining system simplicity.
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 maximizes available laser power, extends the dynamic range of output control, and improves switching speed while eliminating LED emission interference, providing stable and repeatable fluorescence measurements.
Implementation Method 1
means for coupling the output beam or beams of the diode laser or lasers into the optical fibre or fibres
Implementation Method 2
it can be seen that if the output from a diode laser is passed through an optical fibre, then there will tend to be no LED-type emission present in the laser beam output from the fibre, even if such output may be present in the initial output beam of the diode laser
Data Source
AI summary
A laser system 1 comprises six solid state diode laser modules 37.1 to 37.6 whose output beams are directly coupled into beam steering devices 38.1 to 38.6 and thereby routed to laser combining dichroic mirrors 39.1 to 39.6, which combine the individual laser beams into a single, co-aligned beam.The combined laser beam is directed into an optical fiber 41.1 for delivery to a target optical instrument such as a microscope. The output beam from delivery optical fiber 41.1 is coupled to the target instrument via fiber output collimating optics 42.1. The output of each of the diode lasers 37.1 to 37.6 is controlled by direct modulation of the lasers' control (drive) currents.