Difference Between SLDs, LDs, and LEDs: Things You Should Know

Diodes and laser technology are benefiting the modern world with several applications. Starting from the medical industries to automotives they are spreading their roots. Superluminescent diodes, Laser diodes, and LEDs are the three widely used technologies in this field. 

But what are the potential differences between these diodes and how it affect their selection for various applications. Let’s understand the real facts through this blog.

Difference Between SLDs, LDs, and LEDs: Things You Should Know

How To Differentiate Between SLDs, LEDs, and LDs?

1. Emitting State

The emitting state describes the nature of light produced from a light-emitting device. Generally, there are two emission states known as coherent emission and non-coherent emissions.

SLD: Superluminescent diodes are known for an incoherent emission state that provides a broad spectrum. It serves a mixture of wavelengths without a consistent phase relationship. This kind of effect is due to the presence of a single-end reflective facet of SLDs. 

LD: Laser diodes work on the principle of emitting coherent sources of light. Having availability of a double reflective facet it provides a narrowband spectrum of wavelengths with a similar phase relationship.

LED: Light-emitting diodes have similar emitting state light SLDs but have a more disrupted phase ratio. Therefore, LEDs also emit an incoherent broad-spectrum band of light.

2. Emitted Light

The spectrum of light is another crucial factor in differentiating SLD, LD, and LEDs. The nature of emitted light also decides the functionality of diodes in several applications.

SLDs: Superluminescent diodes emit a broadband spectrum of light. That means the spectrum contains multiple wavelengths with a significant phase difference. It is valuable for different industries like telecommunication and radiology to use SLDs due to having such a discrete spectrum.

LDs: Laser diodes are completely different from SLDs when it comes to the nature of emitted light or spectrum. LDs are more focused and provide a powerful narrowband spectrum of light on emission.

LEDs: LEDs also provide a less coherent or discrete spectrum band of light but it is less powerful than SLDs.

3. Spectral Half Width

Spectral half width is known as the maximum energy of light spectra at half of its highest amplitude. It helps to determine the spread of wavelengths and their physical applications.

SLDs: Superluminescent diodes comparatively have a large spectral half-width that can go up to 20 nms. This is due to their incoherent emission of light.

LEDs: Light emitting diodes due to their broad spectrum nature have a kind of similar spectral half width to SLDs which range up to 30 nms.

LDs: Having coherent emission spectra Laser diodes have a potentially narrow spectral half-width that can be up to several nanometers.

4. Coherent Length

Coherent length is the length where the phase difference can be appropriately measured. It is an essential factor to assess the effectiveness of diodes. 

SLDs: Superluminescent diodes provide a low coherence length that ranges between 17 to 20 micrometres. It is suitable for applications that require high energy bandwidth like optical coherence tomography.

LDs: The maximum coherence length of Lasers ranges between 2.5mm to 5mm. It is useful in applications that require stability and precision such as long-distance optical communication.

LEDs: Light-emitting diodes provide comparatively higher coherence lengths ranging up to several micrometres. Therefore, light-emitting diodes are safe to use to demonstrate lasers for educational purposes.

5. Optical Output

Optical power output is the maximum power that a diode despite at half spectral width or half of maximum amplitude. It is a crucial factor in determining the potential of diodes. 

SLDs: In Superluminescent diodes, the intensity increases with the density of current and provides a maximum optical power output up to 10 mW. 

LDs: Having coherent spectral wavelength laser diodes poses a higher power output range of up to 15 mW. 

LEDs: In terms of diodes LEDs have the maximum power output up to 140 to 770 mW.

Wrapping it up

Summarizing up, SLDs, LDs, and LEDs have various factors that differentiate their functionality and application in various industries. However, each of the diodes has its own significance and serves several benefits to the technological landscape.