Self-Injection Locked Laser with PLL for Ultra-Narrow Linewidth
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Solution Overview
Problem
Current laser technologies face limitations in achieving ultra-narrow linewidth due to spontaneous emission and environmental factors, leading to broadened linewidth and increased system costs, particularly in applications requiring high precision and frequency stability.
Innovation Solution
A device combining an optical self-injection locking loop and an ultra-stable cavity phase-locked loop, which enhances the resonant quality factor and stabilizes the laser frequency through feedback control, reducing frequency noise and increasing the linewidth narrowing rate without the need for high Q-value resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical self-injection locking is used to narrow laser linewidth, then the resonator quality factor increases and linewidth narrows, but the loop length increases causing greater phase jitter and lower frequency stability
Solution Approach 1:
The patent implements a phase-locked loop (PLL) system that uses feedback control to stabilize the laser frequency. The system detects the laser output frequency, compares it with a reference frequency, and adjusts the laser cavity length or injection current to maintain frequency stability, thereby resolving the phase jitter issue caused by increased loop length in self-injection locking.
Solution Approach 2:
The patent introduces an ultra-stable optical cavity as an intermediary element in the feedback path. This cavity serves as a frequency reference and filter, providing a stable frequency standard that mediates between the self-injection locking mechanism and the laser, thereby improving frequency stability without compromising linewidth narrowing.
2Manufacturing precision
If a narrowband optical filter is added to the feedback loop to filter unwanted modes, then the side-mode suppression ratio improves, but the free spectral range decreases and higher quality factor is required
Solution Approach 1:
The ultra-stable optical cavity performs multiple functions simultaneously: it acts as a narrowband filter to suppress unwanted modes, provides a frequency reference for the PLL, and enhances the overall resonator quality factor. This multi-functionality achieves side-mode suppression without requiring separate high-Q filters.
Solution Approach 2:
The patent changes the operating parameters of the optical filter by using an ultra-stable cavity with specific resonant characteristics. By tuning the cavity length and operating point, the system achieves optimal side-mode suppression while maintaining an acceptable free spectral range, avoiding the need for extremely high quality factor filters.
3Manufacturing precision
If commercially available narrow-linewidth lasers are used, then the linewidth is sufficiently narrow for precise measurements, but the system cost increases significantly
Solution Approach 1:
The patent enables the laser system to self-narrow its linewidth through the self-injection locking mechanism combined with phase-locked loop control. Instead of relying on expensive commercial narrow-linewidth lasers, the system uses readily available lasers and adds external feedback control, making the high-performance laser source self-generated and cost-effective.
Solution Approach 2:
The patent replaces expensive commercial narrow-linewidth lasers with cheaper standard lasers combined with external control electronics. The system uses off-the-shelf laser diodes or DPSS lasers that are significantly less expensive, compensating for their broader inherent linewidth through the implemented feedback control mechanism.
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
The device achieves a higher linewidth narrowing rate and lower frequency noise, providing a stable narrow-linewidth laser source for applications in fiber optic communications, lidar, and medical fields, while reducing system costs.
Implementation Method 1
Optical self-injection locking technology is a method to narrow laser linewidth. It achieves linewidth narrowing by coupling a portion of the laser output back into the laser through a circulator.
Implementation Method 2
the ultra-stable cavity phase-locked loop is configured to stabilize the phase of the optical signal in the optical self-injection locking loop and further reduce the laser frequency noise through feedback control of the laser current
Implementation Method 3
a piezoelectric ceramic controller; the optical self-injection locking loop includes a laser, an optical circulator, two optical fiber couplers, a phase modulator, an ultra-stable optical resonator, a polarization controller, an erbium-doped fiber amplifier (EDFA), an optical bandpass filter, and a piezoelectric ceramic controller
Data Source
AI summary
A device for generating laser with ultra-narrow-linewidth includes an optical self-injection locking loop and an ultra-stable cavity phase-locked loop. The optical self-injection locking loop improves the quality factor of the laser resonator to narrow the linewidth. The ultra-stable cavity phase-locked loop locks the phase of the optical signal in the optical self-injection, synchronizing the laser frequency with the optical resonator. Through feedback control of the laser's driving current, it further reduces the laser's frequency noise and enhances the linewidth narrowing rate. Additionally, the ultra-stable cavity phase-locked loop provides stable control of the laser frequency, preventing mode hopping caused by laser frequency drift, thereby improving system stability. Therefore, this device can provide a stable narrow-linewidth laser source for applications in fiber optic communication, lidar, industrial device processing, and medical fields.