Vertical-Cavity Surface-Emitting Lasers Overview

VCSEL plays an important role in the field of optical communications. It is a light source used in low-speed and 100G short-distance transmission, providing low-cost, low-power and high-density solutions for data centers and network communications. This article will take you to a detailed understanding of the VCSEL laser, its advantages and characteristics, etc., to help you choose the right device for yourself when purchasing products.

What is VCSEL

Vertical-cavity surface-emitting lasers are different from traditional edge-emitting laser technology. It is a semiconductor laser diode whose light is emitted vertically from the top surface. Its core is a very short resonant cavity consisting of two highly reflective mirrors with a gain medium sandwiched between them. The reflectivity of these mirrors is between 99.4% and 99.9%, which allows the light to oscillate perpendicular to the layers and achieve efficient light emission.

Vertical-cavity surface-emitting laser designing by a multilayer structure of p-contact layer, high reflectivity mirror, laser emitting active region and distributed Bragg reflector. It has the characteristics of easy integration, low threshold current, high packaging density, and single longitudinal mode operation under different conditions. It can achieve high-speed modulation and efficient coupling with optical fiber. This makes it one of the top choices for applications such as data centers and high-speed communication networks. QSFPTEK provides 10G VCSEL laser modules to help your business succeed.

Working Principle of VCSEL

The working principle of the VCSEL laser is based on the basic principle of semiconductor lasers. In the gain region inside the Vertical-cavity surface-emitting Lasers, the recombination of electrons and holes will release photons, forming lasers through multiple reflections in the resonant cavity. Its specific working principle is as follows:

Injection of electrons and holes: When current passes through the laser, electrons will be injected into the gain region, and holes will also be injected at the same time. The gain region is usually made of semiconductor materials such as InGaAs or GaAs.

Photon generation: Electrons and holes recombine in the gain region and generate photons. Due to the presence of high reflectivity mirrors, some photons are reflected and enhanced in the cavity.

Laser emission: When the number of photons reaches a certain number after reflection and enhancement, they will break through the reflector to form a laser beam emitted in a vertical direction.

The above is the specific working principle of VCSEL. Its design enables it to work in different ranges of wavelengths, and the common laser wavelengths are 850nm, 1310nm and other bands.

Advantages of VCSEL

When it comes to the advantages of vertical-cavity surface-emitting lasers, we have to talk about their high modulation speed. It supports modulation frequencies up to several gigahertz, enabling it to meet the needs of high-speed transmission. Thanks to the short resonant cavity and low latency characteristics of VCSEL, it occupies a place in high-speed short-distance transmissions such as 40G and 100G.

The second advantage is its low power consumption. Since VCSEL laser can generate sufficient laser output at a relatively low current, it is more energy-efficient in long-term operation, thereby reducing the overall operation and maintenance costs of the network. It is particularly suitable for places that need to run for a long time, such as data centers and campus networks.

In the development of communication technology, miniaturization is increasingly emphasized, which happens to be one of the advantages of vertical-cavity surface-emitting lasers. It has a compact structure and can be easily integrated into various devices. The use of Vertical-cavity surface-emitting lasers helps to reduce the overall size of the device and can be deployed in a smaller space.

Finally, due to long-term development, the manufacturing process of VCSEL is relatively simple, and it can use standard semiconductor manufacturing technology to achieve large-scale production and reduce its production cost, so it has a competitive price advantage, can be deployed on a large scale, and quickly achieve network connection.

Limitations of VCSEL

Temperature stability is one of the limitations of vertical-cavity surface-emitting lasers (VCSELs). Due to their sensitivity to temperature variations, performance fluctuations can occur under extreme thermal conditions. Consequently, to ensure stability, VCSELs typically must operate within a defined ambient temperature range, which adds complexity to the system design.

Since the emission beam of VCSEL is relatively wide, its beam quality may not be as good as other types of lasers. Especially in long-distance transmission, the divergence of light speed will cause signal attenuation, thus affecting the signal transmission quality. Therefore, when you need to transmit over long distances, Vertical-cavity surface-emitting lasers have certain limitations.

Finally, the output power of vertical-cavity surface-emitting lasers is usually lower than that of edge-emitting lasers, which limits its use in some high-power applications. Although VCSEL laser has excellent transmission performance in short distances, it has certain limitations in scenarios where long distances or high power output are required.

Applications

Data Center

Vertical-cavity surface-emitting lasers play an indispensable role in data centers, especially in 40G and 100G applications. Since data centers transmit within a certain range, VCSEL performs well in short-distance transmission and has a low deployment cost. Therefore, deploying it in data centers can achieve efficient and reliable communication networks, meet the growing bandwidth demand, and can be deployed within the cost to avoid the difficulties caused by insufficient funds.

Sensors

Due to its high sensitivity and miniaturization, VCSEL is also widely used in optical fiber, temperature, and gas sensors. Its extremely high sensitivity enables it to monitor various changes agilely in complex environments and it can accurately measure various data while ensuring the accuracy of the information.

Medical Industry

VCSELs also have a wide range of applications in biosensors and medical imaging devices. Their characteristics enable fast and accurate detection in non-contact blood glucose monitoring instruments, helping doctors and patients quickly understand health status, achieve precise treatment and conserve medical resources.

Conclusion

VCSEL has become an important part of the optoelectronics field due to its advantages such as low power consumption, low cost, high modulation speed, miniaturization, and a wide range of application scenarios. Although there are some limitations such as low output power, sensitivity to temperature changes, and wide emitted beams. However, its key role in high-speed data transmission and optical interconnection makes it still have a place in the future network development.