Lighting is a vital factor for commercial and personal reasons alike. However, lighting has come a long way since its incandescent days, and customers are now presented with a wide range of lighting options for almost any requirement imaginable. Nevertheless, with all of these choices comes the inevitable question, what should you choose? This post explains the difference between two popular options and how you can select the right one for your requirements.

A Quick Rundown Of The Difference Between SLD And LD Light
Photo: Unsplash (LaserWorld LaserBeam).

What Are SLD Lights?

This type of lighting is based on amplified spontaneous emission light. While this might sound like a technical term, all it really is is light that has been produced spontaneously when an atom, while in a high-energy state, falls into a lower-energy state which results in a photon. It is then amplified optically. Superluminescent Diodes (SLD) produce a spectrum that is far more comprehensive and has a lower coherence than laser diode lights (mentioned later in the post). They are excellent for use in joining with optical fiber and have a wide range of other benefits.

What Applications Do SLD Lights Have?

As the name suggests, SLD lights are LED lights that are used for a variety of applications. They can be used in different industries such as automotive, construction, and many more.

Optical Coherence Tomography

Optical coherence tomography (OCT) is a non-invasive imaging technique. OCT takes cross-section images of your retina using light waves. An ophthalmologist can use OCT to observe each of the retina’s different layers. The ophthalmologist will be able to map and assess their thickness as a result of this. These metrics aid in the diagnosing process. They also offer medical advice for glaucoma and retinal problems. Age-related macular degeneration (AMD) and diabetic eye disease are examples of retinal illnesses. While it is often used in the field of ophthalmology, it can also be used in other areas such as dermatology and cardiology. This technology can provide high-quality images with minimal radiation exposure and relatively inexpensive cost, making it attractive for many healthcare professionals.

Although its use is prevalent in the medical industry, it can also be used in commercial applications. For example, it is used to inspect workpieces to determine if they have burrs or scratches and check the thickness and surface roughness of certain materials. 

A Quick Rundown Of The Difference Between SLD And LD Light
Photo: Unsplash (JJ Ying).

Atomic Force Microscope

An atomic force microscope (AFM) is a scanning probe microscope used to measure the distance between two surfaces. An AFM can be used in many different fields, such as nanotechnology, bio-nanotechnology, or materials science. It has been used in the study of nanoscale objects and has been applied to the development of biomaterials for medical applications. Atomic force microscopes are also used in various industries such as semiconductor manufacturing and biomedical research.


The light that goes through or is reflected by a slitted grating is measured by an optical type encoder to evaluate displacement. Because a gradual output technique may be used to avoid mathematical processing, this gives more accuracy than a magnetic style encoder and allows for faster responses. For encoders, an SLD light source is ideal. An SLD light source achieves low coherence because it generates spontaneous emission of light, as discussed earlier. Low coherence minimizes noise caused by interference with light emitted and received, making positional change detection more accurate.

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What Are Laser Diode Lights?

A number of next-generation lighting technologies, including laser diode lighting, have emerged as potential successors to LED lighting. It uses laser technology to provide light instead of using diodes (LED) and gas (as in the form of fluorescent lighting). The light that it produces is very intense and bright. A phosphor layer filters the laser light to create white or softer yellow lighting. Initially, the lasers are very focused. However, different techniques are being developed to diffuse the light, which is more practical for everyday applications.

What Applications Do Laser Diodes Have?

A laser diode is the most suitable type of lighting when it needs to be focused and bright. Commercial products are currently under development for more widespread use. Laser diode lights are the most appropriate solution where concentrated, intense illumination is required. Projectors, spotlights, and automobile headlamps are all examples of this type of lighting.

Medical Use

Like SLD lighting, LD lights have medical applications currently being used for various purposes. Because the wavelengths range from 810 to 1064 nm, they are not well absorbed by soft tissues, making them attractive for cases requiring a high degree of sensitivity. 


Laser diode lights are used in telecommunications in various ways. The most common use of laser diode lights is to transmit data through fiber optic cables. Laser diode lights also help transmit signals across long distances and can be used for other telecommunications purposes as well.


Laser light is an essential part of spectrometry, used to excite the molecules and ionize them. Laser light can be used in different types of spectrometry, such as absorption, emission, fluorescence, or polarization spectroscopy. 

A Quick Rundown Of The Difference Between SLD And LD Light
Photo: Unsplash (Aryo Yarahmadi).

Differences Between LD And LED Lighting

There is some overlap between the two technologies, but there remains a great deal of difference. For example, an LED doesn’t require feedback while an LD does. Moreover, laser diodes create extremely directional light when compared to the more scattered lighting that LEDs produce. Laser diodes can also transmit higher bandwidth, making them far more suited to applications like telecommunications. Moreover, they are highly reliable and can operate for more extended periods of time. Compared to equivalent LEDs, the primary downside is the relatively higher cost of production.

Why Might You Use An SLD Over A Laser Diode?

The advantage of employing an SLD is that it has reduced coherence over LD lighting, allowing for lower coherence noise. When an SLD is used to detect light interference, it decreases diffused reflection (speckle noise) on the object’s surface that is being measured.

As you can see, there are numerous differences between these two lighting sources. SLD lighting has a lower coherence than laser diode lighting making it more useful for specific applications. However, LD lighting has certain applications that make it an ideal option, especially when compared with LED lighting.

Published by Mike

Avid tech enthusiast, gadget lover, marketing critic and most importantly, love to reason and talk.