Loop Resonator Laser Pulse Modulation for Minimal Chirp
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Solution Overview
Problem
Current methods for creating laser pulses in optical communication systems often result in chirp, which causes broadening and distortion of pulses as they travel through optical media, limiting transmission distance and potentially corrupting data.
Innovation Solution
A laser with a loop resonator that generates laser pulses by modulating the optical power of two modes (CW and CCW) to overlap in time with opposite sign changes, maintaining stable population inversion and refractive index, thereby reducing chirp.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct modulation of laser diode drive current is used to create laser pulses, then the laser pulses can be generated efficiently, but chirp is introduced causing pulse broadening and limiting transmission distance
Solution Approach 1:
The invention segments the single-mode laser pulse generation into two separate modes (CW and CCW) that propagate in opposite directions through the loop resonator. Each mode is independently modulated with opposite polarity, allowing the total optical power to remain stable while still generating the desired laser pulse output. This segmentation eliminates the chirp-induced broadening that limits transmission distance.
Solution Approach 2:
The invention changes the modulation parameter from direct current modulation (which causes chirp) to optical power modulation of separate modes with opposite signs. By modulating the CW and CCW modes with equal magnitude but opposite polarity, the total optical power P_total = P_CW + P_CCW remains constant, eliminating frequency chirp while maintaining pulse generation capability.
2Reliability
If external optical modulation is used to create laser pulses, then chirp can be reduced, but the device complexity and cost increase
Solution Approach 1:
The loop resonator serves multiple functions simultaneously: it acts as the optical cavity for lasing, the medium for mode propagation, and the structure enabling bidirectional mode generation. The same resonator structure that generates the laser modes also provides the platform for their independent modulation, eliminating the need for separate external modulators and reducing overall system complexity.
Solution Approach 2:
The invention creates a copy of the laser mode propagating in the opposite direction (CCW mode as a copy of CW mode). By modulating this copied mode with opposite polarity, the system achieves chirp reduction without requiring complex external modulation hardware, as the copying and modulation are integrated into the resonator structure itself.
3Productivity
If optical power of a single mode is modulated to create laser pulses, then pulse generation is achieved, but total optical power changes causing chirp
Solution Approach 1:
The invention applies counterweight by modulating the CCW mode with equal magnitude but opposite polarity to the CW mode modulation. When P_CW increases to create a laser pulse, P_CCW decreases by the same amount, keeping P_total constant. This counterbalancing action prevents changes in total optical power that would otherwise cause frequency chirp and maintain stable instantaneous frequency.
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 creation of laser pulses with minimal chirp and stable instantaneous frequency, improving optical communication efficiency while being power and cost-effective, with potential for low power consumption and versatile operation across a wide wavelength range.
Implementation Method 1
an optical gain medium configured to lase
Implementation Method 2
a loop resonator forming a closed loop light path
Data Source
AI summary
Example embodiments relate to lasers that include loop resonators. One example laser includes a loop resonator forming a closed loop light path. The loop resonator includes an optical gain medium configured to lase. The loop resonator is configured to, during lasing, present a pair of modes: a mode of light propagating in a clockwise direction in the closed loop light path of the loop resonator (termed CW mode) and a mode of light propagating in a counter-clockwise direction in the closed loop light path of the loop resonator (termed CCW mode). The laser also includes a first light output configured to output laser light from the laser. Additionally, the laser includes an optical power modulating unit. The optical power modulation unit is configured to modulate an optical power of the CW mode of the loop resonator and an optical power of the CCW mode of the loop resonator.