Tunable Laser Feedback Locking for Stable Single-Mode Operation
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Solution Overview
Problem
In optical telecommunication systems, maintaining stable laser frequency alignment within a predetermined frequency band is challenging, especially as lasers age, leading to reduced performance and increased multimode operation.
Innovation Solution
An optical device with a laser configuration that includes a gain region between optical reflectors and an optically active region, which generates electrical signals for tuning the wavelength and aligning cavity modes with reflection peaks, using a temperature-controlled comb mirror to adjust channel spacing and maintain frequency locking without external references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional laser structures are used, then the device is simple in structure, but frequency stability deteriorates over time due to aging and multimode operation
Solution Approach 1:
The patent combines the gain region and optically active region into a single integrated laser structure. The optically active region is positioned between the gain region and the first optical reflector, allowing the same structure to both generate light and provide monitoring feedback, thereby improving frequency stability without significantly increasing device complexity
Solution Approach 2:
The optically active region generates electrical signals that provide feedback about the light transmitted through the first optical reflector. This feedback mechanism enables real-time monitoring and adjustment of laser frequency, maintaining stability over time by detecting and correcting drift before it becomes problematic
2Reliability
If external frequency references are used for frequency locking, then frequency stability is improved, but device complexity and cost increase
Solution Approach 1:
The laser structure uses its own internal components (optically active region and optical reflectors) to generate the feedback signals needed for frequency locking. The optically active region monitors the light transmitted through the first optical reflector and generates electrical signals that enable the laser to self-correct its frequency, eliminating the need for external frequency references
Solution Approach 2:
The optically active region serves multiple functions: it acts as both a monitoring element and a signal generation source. By using the existing optical components for dual purposes (light generation and frequency monitoring), the patent achieves frequency locking without requiring separate external reference systems
3Ease of operation
If the laser operates without monitoring, then device complexity is reduced, but alignment maintenance capability deteriorates
Solution Approach 1:
The monitoring function is merged into the laser structure itself through the optically active region. This region is positioned to naturally intercept a portion of the light transmitted through the first optical reflector, converting it into electrical signals for feedback. The monitoring capability is thus integrated rather than added as a separate system
Solution Approach 2:
The electrical signals generated by the optically active region provide continuous feedback about the laser's optical output and frequency alignment. This feedback enables automatic adjustment and maintenance of alignment throughout the laser's operational lifetime, compensating for aging and environmental changes
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 single-mode laser operation with improved side mode suppression ratio, reducing multimode performance and maintaining alignment throughout the laser's lifetime by using photocurrent and voltage feedback for optimal performance.
Implementation Method 1
The at least one optically active region is configured to generate at least one electrical signal indicative of light transmitted from the at least one gain region through the at least one first optical reflector
Implementation Method 2
a laser comprising at least one first optical reflector, at least one second optical reflector, and at least one gain region between the at least one first optical reflector and the at least one second optical reflector, the at least one gain region configured to generate light
Data Source
AI summary
A laser comprising a laser cavity formed by a first optical reflector, a gain region, a second optical reflector having a plurality of reflection peaks, and at least one optically active region. The first mirror may be a DBR or comb mirror and the second mirror may be a comb mirror. The spectral reflectance of the second optical reflector is adjusted at least partially based on an electric signal received form the optically active region such that only one reflection peak is aligned with a cavity mode formed by the first and second reflector.