edge-emitting semiconductor lasers (original) (raw)

Definition: semiconductor lasers emitting light along the plane of the wafer

Alternative term: in-plane lasers

Category: laser devices and laser physics

• solid-state lasers
  • semiconductor lasers
    * laser diodes
    * diode lasers
    * edge-emitting semiconductor lasers
    * surface-emitting semiconductor lasers
    * quantum cascade lasers

Related: semiconductor laserslaser diodesbroad area laser diodessurface-emitting semiconductor lasers

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DOI: 10.61835/3z7 Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn

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What are Edge-emitting Semiconductor Lasers?

Semiconductor lasers can be grouped into two classes:

• Edge-emitting lasers (also called in-plane lasers), where the laser light propagates in a direction along the wafer surface of the semiconductor chip, from which the laser is made. The light is usually reflected or coupled out at a cleaved edge.
• Surface-emitting lasers, where the light propagates in the direction perpendicular to the semiconductor wafer surface.

Figure 1: Edge-emitting semiconductor laser.

Edge-emitting lasers are the original and still very widely used form of semiconductor lasers. Their resonator length is typically between a few hundred micrometers and a few millimeters. This is sufficient for reaching a high gain, so that an edge-emitting laser may lase even if the resonator losses are fairly high, e.g. when the endfaces (edges) are not coated and there is only the Fresnel reflection of the semiconductor/air interfaces.

Within the edge-emitting laser structure, the laser beam is guided in a waveguide structure. Typically, one uses a double heterostructure, which restricts the generated carriers (electrons and holes) to a narrow region and at the same time serves as a waveguide for the optical field. Such an arrangement leads to a low threshold pump power and a high efficiency.

Depending on the waveguide properties, particularly its transverse dimensions, it is possible either to obtain an output with high beam quality but limited output power (some hundreds of milliwatts), or (with a broad-area laser diode) an output with high output power (tens of watts or even more than 100 W) but with poor beam quality.

The light emission is often linearly polarized, with the polarization direction typically being parallel to the wafer surface.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What is an edge-emitting semiconductor laser?

It is a type of semiconductor laser where the light propagates along the semiconductor wafer's surface and is emitted from the chip's edge, which is typically a cleaved facet. They are also called in-plane lasers.

How do edge-emitting lasers differ from surface-emitting lasers?

In edge-emitting lasers, the light travels parallel to the wafer surface and exits from the side. In contrast, surface-emitting lasers, such as VCSELs, emit light in a direction perpendicular to the wafer surface.

Can edge-emitting lasers produce high output powers?

Yes, but this often involves a trade-off with beam quality. For example, broad-area laser diodes can generate tens of watts or more, but with poor beam quality, while surface-emitting designs offer high beam quality at lower powers.

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