VCSEL – An Introduction to Vertical-Cavity Surface-Emitting Laser

Semiconductor lasers are essential devices for regulating and improving the Internet and communication sector in the world. Laser’s outstanding properties such as high efficiency of the electrical energy into photons, the excellent reliability, the small footprint, the modulation bandwidth, and the low cost have made it a principle component in various communication applications.

VCSEL or Vertical Cavity Surface Emitting Laser is one such laser that is largely used in various industrial and military applications. This article discusses the basics of VCSEL, including definition, working and characteristics.

What is VCSEL?

Wikipedia defines VCSEL as the type of semiconductor laser diode with laser beam emission perpendicular from the top surface, as opposed to conventional edge-emitting semiconductor lasers which emit from surfaces.

In simple words, compared to conventional edge-emitting light diodes, VCSEL emits light or vertical beam from its top surface.

 

An edge-emitting diode vs VCSEL

 

Now let us comprehend how VCSEL works. Note that, as it is challenging to cover the whole working process in detail, we have covered fundamental points only.

Working of VCSEL

A typical Vertical-Cavity Surface-Emitting Laser is made of several layers. The top is a layer in electrical contact for current injection. The next layer, i.e. the second layer, is the high reflectivity mirror with having 99% reflectivity. The next– the third layer is an oxide layer which develops a light-emitting window so that the light beam can be converted into a circular beam.

The next layer– the centre layer in the VCSEL is the laser cavity. It is the active gain region where lasing happens. Again there is an oxide layer below the centre layer to confine the light. And the last layer is again a DBR– distributed Bragg reflector and the last– the bottom layer is a reflective mirror with 99.9% reflectivity.

 

Cross sectional image of VCSEL showing different layers

 

Note that the bottom mirror has more reflectivity than the top mirror so that lasing light can get out from the top mirror instead of the bottom mirror.

The quantum wells generate photos that travel between the top DBR mirror and the bottom DBR mirror. This lasing mechanism remains the same in every laser. The quantum well is made of three layers–a very thin gallium arsenide layer sandwiched between two thick aluminium gallium arsenide layers. This structure produces quantum confinement– an effect to increase lasing efficiency.

Now, let us learn about some of the significant characteristics of the VCSEL, which makes it a preferred option for a variety of medical, industrial and military applications.

The Major Characteristics of VCSEL

In the next blog on VCSEL, we will cover its applications in detail. Keep following Inphenix.

Inphenix is a laser and light source manufacturing company headquartered in California, USA. The company develops a range of optic devices, lasers and light sources including distributed feedback lasers, superluminescent diodes, Fabry-Perot laser, swept source laser and VCSEL, among others.