Chemical
Spectroscopy
Surface Profiling
and Ranging
Optic
Sensing
Optic
Gyroscopes
Coherence
Tomography
Advanced SLEDs
for the Near Infrared Range
Made by EXALOS
EXALOS offers a wide variety of Superluminescent Light Emitting Diodes (SLED) for the Near Infrared Range (NIR) at different wavelengths ranging from 750 to 1700 nm, with different output power and bandwidth values.
Since 2003, EXALOS has shipped more than 500,000 NIR SLEDs. EXALOS products are used extensively in Medical and Industrial Imaging, Navigation, Optical Sensing, Metrology, and Scientific applications.
For a list of all available SLEDs and their specifications, please visit our SLED Product page.
Our high-performance SLEDs come in various packages or form factors, including:
- Cooled 14-pin Butterfly and Dual-In-Line (DIL) packages
- Add “Cooled 9-pin Butterfly packages”
- Cooled and Uncooled 5-pin Butterfly packages
- Low-cost uncooled TOSA packages
- Uncooled free-space TO-56 packages
EXALOS SLEDs provide efficient beam collimation and waveguide coupling.
The operation and Lifetime/Reliability of SLEDs are similar to that of Laser Diodes.
EXALOS has a long track record of creating innovative, industry-leading light sources:
- 20+ years with InP devices,
- 15+ years with Gallium Arsenid (GaAS) devices
- 10+ years with Gallium Nitrid (GaN) devices.
What are SLEDs?
Broadband "Laser Diodes" with a beam-like output
Incoherent "Laser Diodes"
Speckle-free "Laser Diodes"
S Superluminescent Emitting Diodes (SLEDs, SLDs) are semiconductor devices that emit broadband light through electrical current injection. SLEDs are a hybrid between LEDs, which emit broadband light in all directions, and semiconductor laser diodes, which emit narrowband light with a well-defined laser beam. In this sense, SLEDs can be understood as broadband laser diodes with a beam-like output.
Broadband means that SLEDs emit an optical spectrum that is broad in the wavelength or frequency domain. The spatial domain is correlated to the frequency domain through the Fourier transform. A light source that is broadband in the frequency domain is therefore narrowband in the spatial domain, meaning it is having a short coherence length (see below). In this sense, SLEDs can be also understood as incoherent laser diodes.
Light from any light source can interfere with light from the same or another light source, but only within its coherence length. Reflections from surfaces, which are never perfectly flat and even, cause so-called “speckles” when the path differences between the interfering light waves are smaller than the coherence length of the light.
Speckles are random dark and white interference patterns that are perceived as noise. Narrowband laser diodes typically generate speckle noise because of their large coherence length. In this sense, SLEDs can be understood as speckle-free laser diodes.
SLEDs – Comparison to LEDs and Laser Diodes
SLEDs have distinctive optical characteristics that essentially makes them a desirable hybrid between the properties of laser diodes and LEDs.
Performance comparison of LD, LED and SLEDs
Superluminescence Emission Regime
The total optical power emitted by an SLED depends on the injected current. Unlike laser diodes, the output intensity does not exhibit a sharp threshold but it gradually increases with current (see image below).
A soft knee in the power vs. current curve defines a transition between a regime dominated by spontaneous emission (typical for surface emitting LEDs) and one that is dominated by amplified spontaneous emission (i.e. superluminescence).
The maximum value of the current that allows a safe operation of the device depends on the model and ranges between 70 mA and > 500 mA for the most powerful devices.
Full CAST
High-Performance SLEDs for the complete Near Infrared Range
from
nm
to
nm
Fibre & Connectors
Military Standards
Combining the advantages of Laser Diodes and LEDs.
As described above (“What are SLEDs?”) Superluminescent Light Emitting Diodes have distinctive optical characteristics that essentially bridge the gap between the properties of Laser Diodes and LEDs (* see benefit comparison below).
SLEDs emit an optical spectrum that is broad in the wavelength or frequency domain, which translates to a low temporal coherence or short coherence length. Conversely, they exhibit high directionality or spatial coherence.
Thanks to this special behaviour, SLEDs combine the spatial coherence of a laser diode and the temporal incoherence of an LED.
The spatial coherence translates into a small beam divergence, which enables the coupling of the output into a single-mode fibre with an efficiency similar to that of laser diodes. Typically more than 50 percent of the power from a single facet can be coupled into a single-mode fibre. The low temporal coherence is advantageous for applications where interferences cause problems such as speckle or ghost signals – perfect for any kind of projection technology (read more in our Blog: Quality Comparison of Light Sources for Holographic Projection).
At the same time, SLEDs are much more powerful than standard LEDs and are particularly useful for applications that require high power densities. When biased with several hundreds of milliamperes, they typically have single-mode output powers of the same order of magnitude as single-mode laser diodes of several tens of milliwatts.
Comparison of the optical properties of LEDs, SLEDs and LDs.
LED | SLED | LD | |
Optical Spectrum | Broadband | Broadband | Narrowband |
Temporal Coherence | Low | Low | High |
Speckle Noise Generation | Low | Low | High |
Directionality | Low | High | High |
Polarization | High | High | Low |
Spatial Coherence | Low | High | High |
Coupling into Single-Mode Fibers | Poor | Efficient | Efficient |
Polarization State | Random | Linear | Linear |
More about SLEDs
Bridge the Gap
By combining the best features of lasers and LEDs, SLEDs bridging an important application gap.
SLEDs can be used in fiber optic pressure sensors for static strain (load) or dynamic strain (vibration) measurements as well as temperature measurements in structures such as suspension bridges.
Read more about SLED technology and their applications in this BLOG article.
More about SLEDs
Bridge the Gap
By combining the best features of lasers and LEDs, SLEDs bridging an important application gap.
SLEDs can be used in fiber optic pressure sensors for static strain (load) or dynamic strain (vibration) measurements as well as temperature measurements in structures such as suspension bridges.
Read more about SLED technology and their applications
in our BLOG
More from our Blog
Superluminescent LEDs Enter the Mainstream
The combination of valuable features of Superluminescent LEDs are essential for a variety of applications and finding commercial use.