Laser Diode Phase Shifting for External Reflection Linewidth Control
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Solution Overview
Problem
Laser diodes are sensitive to external reflections, which can cause linewidth broadening and coherence collapse, affecting their performance in applications like optical communications and LIDAR, and existing solutions like optical isolators are bulky and not suitable for compact designs.
Innovation Solution
A laser apparatus with a sensor unit and phase shifter that measures frequency variations and controls the phase shift of the laser beam to mitigate the effects of external reflections, allowing for integrated and compact operation without the need for optical isolators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an optical isolator is arranged in front of the laser diode to shield external reflections, then the laser performance is improved by preventing linewidth broadening and coherence collapse, but the device becomes bulky and cannot be integrated on the same substrate
Solution Approach 1:
The patent merges the laser diode and the sensor unit onto the same substrate, integrating previously separate components. This integration eliminates the need for external optical isolators while maintaining laser performance, directly resolving the contradiction between reliability and device size.
Solution Approach 2:
Instead of blocking external reflections with an optical isolator, the patent converts the harmful reflected light into a useful signal by using a sensor unit to detect the reflected light's intensity. This detected information is then used to actively control and stabilize the laser output, transforming the harmful reflection into a beneficial feedback mechanism that maintains performance without requiring additional space.
2Volume of moving object
If external reflections enter the laser diode, then the device structure remains compact, but the linewidth broadens and coherence collapse occurs, degrading laser performance
Solution Approach 1:
The patent implements a feedback control mechanism where the sensor unit continuously monitors the intensity of reflected light entering the laser diode. This reflected light intensity signal is used to generate control signals that adjust the laser diode's operation in real-time, actively compensating for the degrading effects of external reflections and maintaining stable laser performance without requiring physical isolation components.
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 solution reduces or eliminates linewidth broadening, provides a more compact and stable laser apparatus, and achieves a narrower linewidth, improving performance in applications such as optical communications and LIDAR.
Implementation Method 1
a phase shifter arranged in a path of a second portion of the laser beam, and configured to generate a phase shift of the second portion of the laser beam propagating through the phase shifter
Implementation Method 2
a sensor unit configured to receive a first portion of the laser beam, wherein the sensor unit is further configured for measuring variations of the frequency of the first portion of the laser beam
Implementation Method 3
a laser diode configured to emit a laser beam
Data Source
AI summary
A laser apparatus is described herein which includes a laser diode for emitting a laser beam, configured for frequency modulation of the laser beam; a sensor unit configured to receive a first portion of the laser beam, and for measuring variations of the frequency of the first portion; and a phase shifter arranged in a path of a second portion of the laser beam, and configured to phase shift the second portion. The laser apparatus is configured to output the second portion having propagated through the phase shifter, and to acquire measurements of variations of the frequency during frequency modulation at different phase shifts, and to control the phase shifter based on the measurements to control the variations of the frequency, whereby the laser apparatus may control a linewidth of the laser beam in dependence of an external reflection of the output laser beam, received by the laser apparatus.