Source: MEETOPTICS
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Superluminescent Diodes: Understanding the Broadband Light Source

Introduction to Superluminescent Diodes

Superluminescent diodes (SLDs) are semiconductor devices that emit broadband optical radiation based on superluminescence. They are similar to laser diodes but are designed to prevent laser action by avoiding optical feedback.

Construction and Operation

SLDs consist of an electrically driven p–n junction and an optical waveguide. By tilting the facets relative to the waveguide and using anti-reflection coatings, optical feedback is suppressed. This design allows for amplified spontaneous emission without laser action.

Wavelength, Power, and Bandwidth

Most SLDs emit light in the regions around 800 nm, 1300 nm, and 1550 nm. They typically have output powers ranging from a few milliwatts to tens of milliwatts and offer high spatial coherence. The optical bandwidth is usually several tens of nanometers, making them suitable for fiber-coupled applications.

Technical Considerations

SLDs must be protected from external optical feedback to prevent spectral narrowing or parasitic lasing. They are sensitive to electrostatic discharges and current spikes but can have a long operational lifespan when handled correctly.

Applications of SLDs

SLDs are used in optical coherence tomography, chromatic dispersion measurements, fiber-optic sensors, and fiber-optic gyroscopes. Their broad spectrum and high spatial coherence make them ideal for applications requiring precise and high-intensity light sources.

Alternatives and Future Developments

For higher powers, SLDs can be replaced with fiber amplifiers, though at a higher cost. In some cases, incandescent lamps may suffice for low-power applications. Ongoing research focuses on improving output power, bandwidth, and wavelength stability of SLDs for enhanced performance in various applications.

Source: MDPI
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