Fiber lasers, unlike traditional lasers, do not use conventional dielectric mirrors in their optical cavity.
How Fiber Lasers Achieve Optical Feedback
The core difference lies in the way fiber lasers are constructed. Instead of using separate mirrors to reflect light within the laser cavity, fiber lasers:
-
Monolithic Construction: They are built by fusion splicing different types of optical fiber together. This makes the laser structure a single, continuous piece, reducing the need for external components like mirrors.
-
Fiber Bragg Gratings (FBGs): The key to optical feedback in fiber lasers is the use of fiber Bragg gratings. These are periodic variations in the refractive index within the fiber core. These variations act as reflectors of light at a specific wavelength.
- These FBGs effectively replace traditional dielectric mirrors.
- They are integrated directly into the fiber itself.
Why Fiber Lasers Don't Need Traditional Mirrors
| Feature | Traditional Lasers | Fiber Lasers |
|---|---|---|
| Optical Feedback | Dielectric mirrors | Fiber Bragg gratings |
| Laser Cavity | Separate optical components | Monolithically constructed |
| Alignment Requirements | Precise | Minimal |
Practical Implications
- Stability: The monolithic nature and the use of FBGs make fiber lasers more stable and less susceptible to misalignment.
- Compactness: By eliminating separate mirrors, fiber lasers can be made more compact.
- Robustness: The integrated nature makes them less sensitive to environmental changes such as vibrations and temperature changes.
In summary, instead of mirrors, fiber lasers employ fiber Bragg gratings within their monolithically constructed fiber optic structure to achieve the necessary optical feedback for laser operation.
