The first episode talked about the working principle of VCSEL laser diode and its application scenarios. Today, Xiaobian will tell you about the advantages and disadvantages of VCSEL laser diode, hoping to help you.

The full name of VCSEL laser diode is vertical cavity surface emitting laser. Unlike edge-emitting laser (EEL), VCSEL emits light vertically from the front of the chip, while EEL emits light from the side of the chip. Although it's just in different directions, this change has brought a lot of technical changes.

So what are its main advantages and disadvantages?

Good beam quality and small divergence angle.

The light emitted by VCSEL is generally a circular spot with a small divergence angle, which is particularly friendly to the design of optical system. For example, in the scenes of infrared illumination, 3D sensing and laser focusing, the uniformity of VCSEL light is higher and the imaging effect is more stable.

Array packaging is flexible and scalable.

The structure of VCSEL allows hundreds of luminous points to be made on a chip, which means that multipoint array emission can be easily realized. Large-scale scanning scenes such as vehicle-mounted lidar or depth imaging in AR/VR all depend on this ability of multi-lighting. Moreover, its technology is close to the LED manufacturing line, and the cost of mass production is much lower than EEL.

Low power consumption and simple thermal management.

Because of its short cavity, high luminous efficiency and large heat dissipation surface of vertical emission structure, the overall heating of VCSEL is much lower than EEL. When the module is actually made, there is basically no need for too complicated heat dissipation design, and the ordinary metal base can hold down the temperature. This is particularly advantageous for electronic products, which require high space.

But, VCSEL is not perfect, and it also has some shortcomings, which we have to tell the truth.

Output power is limited

Because the light of VCSEL is emitted vertically, the cavity length is short, and the output power that a single chip can achieve is limited due to structural constraints. In general, the output power of a single VCSEL is about tens of milliwatts to hundreds of milliwatts. If you want to achieve several watts or even tens of watts, you have to rely on array superposition.

The spectral bandwidth is relatively wide.

The spectrum of VCSEL is not as narrow as EEL, which will be limited in some applications that require high coherence and narrow linewidth, such as precision ranging, interferometer or long-distance transmission of optical communication. Although there is a narrow linewidth VCSEL scheme now, the cost and adjustment difficulty will be much higher.

Temperature sensitivity

Although VCSEL is generally stable, the wavelength will drift slightly when the temperature rises, which requires temperature control compensation for some precision systems. Many modules will be equipped with thermistors or TEC (Thermoelectric Refrigerator) for temperature stabilization.

The advantages of VCSEL are "small but precise, stable and economical", while the disadvantages are "insufficient strength and limited accuracy". But it is this trade-off that makes it find the most suitable position in the field of consumer and intelligent sensing.