Contents
Source: Science
Surface-Emitting Semiconductor Lasers: An Overview
Introduction
Semiconductor lasers play a crucial role in various technological applications. They can be broadly categorized into edge-emitting lasers and surface-emitting lasers. This article focuses on surface-emitting lasers and provides insights into their different types and characteristics.
Monolithic vs. External-cavity Lasers
Surface-emitting lasers can be monolithic or external-cavity lasers. Monolithic lasers are fabricated on a single wafer, which is then divided into individual components. They can also be designed as two-dimensional arrays for higher output powers. External-cavity lasers, on the other hand, incorporate additional elements for laser operation.
Vertical Cavity vs. In-plane Cavity
Vertical-cavity lasers emit light perpendicular to the wafer surface. They can be monolithic or have external components. In contrast, in-plane lasers have the light propagating along the wafer surface. This design allows for higher output powers and better beam quality.
Electrical vs. Optical Pumping
Semiconductor lasers can be electrically or optically pumped. While electrical pumping is common and cost-effective, optical pumping offers advantages such as simplified device structures and uniform energy distribution. Optical pumping is particularly beneficial for high-power vertical-external-cavity surface-emitting lasers (VECSELs).
Advantages of Surface-Emitting Lasers
Surface-emitting lasers offer several advantages over edge-emitting lasers. They have larger emitting areas, eliminating issues like catastrophic optical damage. The fabrication process is simpler, as there is no need to process cleaved edges. These lasers also provide single-mode emission over a wide range of operating conditions and have a smaller temperature coefficient for emission frequency.
Conclusion
Surface-emitting semiconductor lasers represent a significant advancement in laser technology, offering unique benefits and applications. Their versatility and performance make them valuable in various fields, from telecommunications to medical devices.
By understanding the principles and characteristics of surface-emitting lasers, researchers and engineers can harness their potential for further technological advancements.
Source: Nature
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