Red. Green. Blue.
and waveguide coupling.
With the VISIIIBLESRGB EXALOS AG created a revolutionary new kind of Superluminescent LED. These innovative, worldwide unique light sources provide all RGB colors: Red, Blue and Green.
Thanks to a the consequent application of Gallium Nitride and Gallium Arsenide, the VISIIIBLESRGB can provide greater efficiency and brightness. The next generation SLED design allows power efficient, small footprint solutions with a higher image quality and a long lifetime.
EXALOS´ industry-leading SLED technology combines the advantages of LEDs and Lasers. VISIIIBLESRGB are characterized by a low temporal coherence, therefore provide a nearly speckle-free projection, which are a typical issue with laser-based solutions.
Moreover, thanks to the broadband spectrum and the high spatial coherence, EXALOS SLEDs can deliver high sharpness and directionality, outperforming LED- and laser-based projection systems.
With an excellent balanced combination of compact size, high-performance and image quality, EXALOS VISIIIBLESRGB are the essential key technology for the next generation of AR/MR Micro Displays, direct Retina projection or holographic solutions, which are about to change the interaction between humans and the real world in the near future.
Video: EXALOS demonstrates speckle-free RGB lasers:
EXALOS SLED Technology:
Combining the advantages of Laser Diodes and LEDs.
SLEDs 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 (see scientific test results below: 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.
These unique properties are the key to the next generation of small footprint AR/MR Micro Displays, direct Retina projection and holographic solutions.
* SLEDs – The optimal hybrid light source.
Benefits for modern display applications, compared to LEDs and Lasers.
Bridge the Gap.
Superluminescent light-emitting diodes (SLEDs) are broadband semiconductor devices that are closely related to their more commonly known relatives, laser diodes and light-emitting diodes (LEDs).
Application example: 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.
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Long Lifetime. High-Performance.
Optical + Electrical Long-term Reliability
EXALOS VISIIIBLES RGB are designed as reliable high-performance light sources with a long life span. Stable electrical characteristics during the whole lifetime are one of the most essential features for the acceptance of emerging products such as direct retina, 3D printing or the next generation of consumer head-up displays and pico-projectors.
The GaN-based SLED design, introduced with the VISIIIBLESRGB, is using optimized Mg-doping levels, which effectively result in an extended and consistent lifetime-performance at the electrical and the optical levels – comparable to modern laser diodes.
The design overcomes the known problem of GaN-based edge emitting devices, to suffer from degradation in a short time, caused by the diffusion of dopants or contaminants. According to substantial investigations, the residual drop in output characteristics was found to be powerdependent and most likely related to the untimely ageing of the mirror facets, due to Hydrogen diffusion towards the p-metal/semiconductor interface. The degradation process can result into device failure at the ridge level, based on a damage of the p-metallization.*
Unlike devices based on highly-doped Mg-structures the optimized VISIIIBLESRGB design shows stable output characteristics over a long-term period, similar to Laser Diodes, and thus fulfill the requirements of consumer and industrial applications.
GaN-based superluminescent diodes with long lifetime, A. Castiglia, M. Rossetti, N. Matuschek, R. Rezzonico, M. Duelk, C. Vélez, J-F Carlin, N. Grandjean
(published 26 February 2016 in Proc. SPIE 9748, Gallium Nitride Materials and Devices XI, 97481V)
I n 2009 EXALOS introduced the first blue-violet (420nm) SLED based on III-nitride compound semiconductors. The III-N semiconductor technology has since evolved towards more efficient and reliable devices, based on a newly introduced Gallium Nitride (GaN) based technology.
Today EXALOS GaAS- and GaN-based SLEDs comfortably operate in spectral regions from 635 nm, beyond 450 nm and reach with VISIIIBLESGREEN the green spectral range (λ > 510 nm) – completing our range of advanced RGB light sources.
With more than a decade of experience and our industry-leading research team, EXALOS was able to overcome the challenges of this design for visible blue and green light emissions.
The breakthrough was achieved – amongst other things – from extensive modelling/simulation, iterative epitaxial designs and improvements in the modal gain of the semiconductor structure.
Based on a new, innovative design and improved growth conditions for the active region, the waveguide and cladding layers, EXALOS was able to optimize the crystal quality, the optical loss in the light guiding layers and the electrical injection efficiency.
The market-leading Gallium Arsenide and Gallium Nitride technologies allow EXALOS to finally provide RGB SLEDs with unmatched power values, wall-plug efficiency and an even smaller form factor, prepared for the next generation of AR/MR applications.
About EXALOS AG
HIGH-PERFORMANCE BROADBAND LIGHT SOURCES.
Made in Switzerland.
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