EXALOS VISIIIBLES RGB

Revolutionary light sources for
Head-Mounted and Head-Up Displays

RGB

Next generation
GaN/GaAs-based SLED:
Red. Green. Blue.

Superior Images

Combining the advantages of LDs and LEDs: Low temporal coherence. Low speckle. High sharpness.

Collimation

High spatial coherence for efficient beam collimation
and waveguide coupling.

EXALOS VISIIIBLES RGB

Revolutionary light sources for
Head-Mounted and Head-Up Displays

RGB

Next generation GaN/GaAs-based SLED:
Red. Green. Blue.

Superior Images

Combining the advantages of LDs and LEDs: Low temporal coherence. Low speckle. High sharpness.

Collimation

High spatial coherence for efficient beam collimation
and waveguide coupling.

EXALOS VISIIIBLES RGB. A Swiss-made innovation.

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.

Features

  • Low speckle, broadband output.
  • Enabling sharp images
  • High directionality, low etendue beam
  • Diffraction-limited (single spatial mode)
  • Polarized output
  • Energy efficient
  • High damage treshold
  • Designed for compact size applications, free-space or fiber coupled architectures.

VISIIIBLES RGB are designed for: 

  • Holographic Displays
  • Near-to-eye Displays for AR/VR/MR, e.g. Smart Glasses
  • Color-sequential LCOS, DLP, SLM and Scanning MEMS Mirrors
  • Micro Displays
  • Military & Industrial HUDs
  • Pico Projectors
  • Machine Vision
  • Metrology
  • Microscopy

Video: EXALOS demonstrates speckle-free RGB lasers:

VISIIIBLES RGB FEATURES

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Superluminescent LEDs. Made by Exalos.

Combining the Advantages of Lasers and LEDs.

RGB Light Source

The world´s first full RGB light source
with broadband output.

Collimation

Efficient beam collimation
and waveguide coupling.

Long-term Reliability

Same electrical and optical reliability like matured laser diodes.

High Performance

Excellent power to size ratio.
Designed for compact-size applications.

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.

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

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.

Read more about SLED light sources in our BLOG

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Superluminescent LEDs Enter the Mainstream

The combination of valuable features of Superluminescent LEDs are essential for a variety of applications and finding commercial use.

Read More

Optical + Electrical Long-term Reliability

Long Lifetime.
High-Performance.

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.

* In 2016 EXALOS has already demonstrated the reliability of GaN-based SLEDs emitting at 405 nm. A special optimized design reached an estimated lifetime of over 5000 hours under real-life test conditions. Furthermore, the use of optimized p-doped layers allow maximum output powers as high as 350 mW for an injection current of 500 mA have been achieved in continuous-wave operation at room temperature. The test details were scientifically published:

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)

+

TEST DETAILS

VISIIIBLES RGB FEATURES

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Red. Green. Blue.

Gallium Nitride and Gallium Arsenide based RGB SLEDs

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.

The EXALOS GaAs/GaN material system

Innovations ahead of time

Today EXALOS is the only company that provides RGB SLEDs.

  • 20+ years experience with InP devices
  • 15+ years experience with GaAs devices
  • 10+ years experience with GaN
+

LEARN MORE

About EXALOS AG

HIGH-PERFORMANCE BROADBAND LIGHT SOURCES.
Made in Switzerland.
EXALOS AG is an industry-leading Swiss Photonics company, specialised in the development and manufacturing of high-end industrial light sources. EXALOS AG is the only company, which provides GaN-based SLEDs, designed for AR/MR in the visible spectral range.

Read More

VISIIIBLES RGB – The Next Generation of GaAs/GaN based designs

635 nm

Hitting the “Sweet Spot” of high luminous efficacy and low power consumption.

With more than a decade of experience and the leading EXALOS research team, we were able to design the new SLEDs for the high-efficient lower red spectral region, based on our proven Gallium Arsenide architecture.

Thanks to a new active region composition and an advanced edge emitting design, a red SLED with 635 nm, which combines a local maximum for the luminous flux and power conversion efficiency was achieved.

510 nm

A visible green SLED.
The first of its kind.

… increasing the emission wavelength to 500 nm and beyond, to produce a true-green light source, requires values above 20%, which is quite challenging.

By using a next generation GaN-based design, EXALOS was able to overcome the intrinsic challenges of the current materials and produce the first market-ready high-performance SLED for the green spectral range.

450 nm

A true-blue SLED.
With industry-leading performance.

The advanced device structures of our GREEN and BLUE SLEDs are based on epitaxial layers grown on free-standing GaN substrates. They rely on the light emission from multiple InGaN quantum wells sandwiched in the middle of a low Indium content InGaN waveguiding layer, positioned in between lower refractive index AlGaN cladding layers.
Blue SLEDs require quantum wells with moderate indium content (typically of the order of 10 to 15%), …

EXALOS RGB module for AR & Head-up display applications

The module constitutes three SLED chips housed in a 14-pin butterfly package with a total output power of about 30 mW (~ 10 mW/color), which corresponds to a total luminous flux of 5 lm.

The individual chips (635 nm (R), 510 nm (G), and 450 nm (B)) are each soldered on submounts and mounted on a temperature stabilized ceramic base plate that is accompanied by a high-performance thermo-electric cooler. Integral micro-optical elements ensure the individual SLED beams are spatially combined and delivered as a collimated RGB output.

The module is offered as a developer kit with dedicated driver electronics or as a standalone module.

VISIIIBLES RGB FEATURES

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VISIIIBLESRGB – Superior Image Quality out of the box

The perfect light-source
for AR/MR Micro-Displays

Low Speckle. High Sharpness.

The success of the next generation of small footprint AR/MR Micro Displays, direct Retina projection and holographic solutions requires a small footprint, low power consumption and – obviously – a high image quality. Current holographic displays can reconstruct 3D images with full wavefront information and in high quality, free from discontinuous motion parallax, crosstalk and lack of accommodation depth cue. Unfortunately they are still bulky and can be realized only with a costly, huge technological effort to compensate the shortcomings of the currently available light sources.

No wonder, the decisive key factor for highly compact, easy to use, consumer-market ready AR/MR solutions, with a high image quality out of the box, is a new kind of light source. As a matter of fact, any projection technology requires a high degree of coherence to realize an artifact-free, sharp presentation.

In a wide range of potential light sources, laser technology provides a high spatial and temporal coherence.

On the other hand, the laser´s high degree of coherence results in visible speckle artifacts and an amount of blurishness.

The necessary compensation effort increases not only the complexity and the costs of the overall system, but also decreases the bandwidth of the reconstructed images. Finally a projection system with a sufficient speckle correction will kill the necessary form factor.

Due to their operational principles, SLEDs combine the best characteristics of lasers and LEDs and therefore promise important benefits for illuminating MEMS-mirror scanning architectures, LCOS-based displays and holographic spatial modulators.

Consequently, SLEDs with their unique high spatial coherence and low temporal coherence are perfectly suited in order to obtain high quality images with superior sharpness and minimum speckle.

Efficient Beam Collimation

The high spatial coherence of SLED emission – which corresponds to a directional light beam output – leads to a reduced complexity of collimation optics required in the optical subsystems. The low temporal coherence – resulting from the large spectral bandwidth – obviates the need for bulky de-phasers used to reduce undesirable speckle noise.

Furthermore, he light output can be conveniently collimated into parallel beams or focused to µm-scale spot sizes and shows high degree of linear polarization, which can in turn lead to 50% savings in optical output power when used for illumination of LCOS-based micro-displays.

Comparison of speckle noise in the far-field pattern:
(a) blue Laser Diode
(b) blue SLED
(c) Directional emission from 5.6mm TO-packaged blue SLED.

VISIIIBLES GREEN Single-mode light pattern.

Quality Comparison of potential light sources
for Holographic Projection

Extract from an Article in Nature.com – Scientific Reports 7/2017 *

The test from Yuanbo Deng & Daping Chu, published in Scientific Reports 7: 5893 (*), compares the Coherence properties of the following 5 light sources and their effect on the image sharpness and speckle of holographic displays:

DPSS Laser

Diode-pumped
solid-state Laser

LD

Laser Diode

SLED

Superluminscent LED

LED

Light Emitting Diode

mLED

Micro LED

For the test a Superluminescent LED λ = 662 nm from EXALOS was used.

(c) Photos: Yuanbo Deng & Daping Chu. Scientific Reports Volume 7 *

Speckle Contrast (left)

SLEDs achieve a low speckle contrast due to their broad optical spectrum (low temporal coherence).

Image Sharpness (right)

SLEDs achieve a high sharpness due to their high spatial coherence.

Temporal Coherence / Spatial Coherence of 5 light sources.

Temporal Coherence vs. Speckle Contrast

(c) Measurement graph: Yuanbo Deng & Daping Chu. Scientific Reports Volume 7 *

The graph shows the relation between temporal coherence value and speckle contrast value (less is better). The temporal coherence values of the tested light sources are quite different.

The results are proof, that the amount of speckle are mostly influenced by the temporal coherence of the light source.

 

All three LED types were measured in the low value zones, DPSS laser and LD in the high value zone. Speckle contrast and the temporal coherence are in linear relation. SLEDs perform exceptional well and provide precise holographic images with less speckles (see images below).

Spatial Coherence vs. Image Sharpness

(c) Measurement graph: Yuanbo Deng & Daping Chu. Scientific Reports Volume 7 *

The graph shows the relation between spatial coherence value and image sharpness value. The measurements confirm a directly proportional relationship between the spatial coherence value and the image sharpness value.

So the sharpness of the reconstructed images in holographic displays are mostly influenced by the spatial coherence of the used light source.

The spatial coherence values of the LED light sources are in a range from 0.49 to 0.88 – with SLEDs providing the highest values. These values achieve distinguishable holographic reconstructed images with good sharpness (see comparison images on top).

DPSS laser LD SLED LED mLED
Normalized Spatial Coherence 1 0.92 0.76 0.73 0.56
Normalized Temporal Coherence 1 0.81 0.2 0.11 0.045
Speckle Contrast 1 0.76 0.25 0.11 0.055
Image Sharpness Value 1 0.87 0.55 0.22 0.04

Measurement Conclusions *

“Coherence property of a light source can be characterized by its temporal coherence and spatial coherence values, respectively. Light sources such as DPSS laser, LD, LED, sLED and mLED have been characterized and the corresponding holographic images displayed.

Image sharpness and speckle are influenced by both temporal coherence and spatial coherence of the light source in use. It is found that the image sharpness value is linear proportional to spatial coherence value, while the speckle contrast value is linear proportional to the temporal coherence value.

Temporal coherence is decided by the intrinsic spectrum bandwidth of the light source and it can be improved by filtering the spectrum of the light source. On the other hand, spatial coherence is influenced by the size of the light source and the propagation distance in use, it can be improved by changing the size of the utilized light emitting area or the light propagation distance. For example, in an LED based holographic display system, a spatial filter is often applied to reduce the utilized size and increase the spatial coherence of the LED source.

 

Consequently, a light source with high spatial coherence and low temporal coherence is ideal for a holographic display in order to obtain high quality images with good sharpness and minimum speckle. sLEDs … are suitable light sources for this purpose.

LEDs with a broad spectrum can also be used to reconstruct holographic images with less speckle, but it has to be spatially filtered for reconstructive sharp images. Otherwise there will be significant reductions in the energy efficiency and brightness of the reconstructed images.”

* Coherence properties of different light sources and their effect on the image sharpness and speckle of holographic displays (2017).

Yuanbo Deng & Daping Chu. Scientific Reports Volume 7, Article number: 5893 (2017) / DOI:10.1038/s41598-017-06215-x
Published with Open Access under Creative Commons Attribution 4.0 International License
External Link: www.nature.com – Scientific Reports

EXALOS VISIIIBLES RGB

VISIIIBLES RED

635 nm

Hitting the Sweet Spot of higher eye sensitivity and power consumption.

VISIIIBLES GREEN

510 nm

A visible GaN-based GREEN SLED.
The first of its kind.

VISIIIBLES BLUE

450 nm

A high-performance
GaN-based BLUE SLED.

HIGH-PERFORMANCE LIGHT SOURCES

MADE IN SWITZERLAND

HIGH-PERFORMANCE LIGHT SOURCES

MADE IN SWITZERLAND

EXALOS AG is a privately held Swiss technology company, developing industry-leading Superluminescent Light Emitting Diodes and Swept Laser Sources for the medical imaging, fiber optic gyroscope, test equipment, space, military and sensor industries.

EXALOS offers the widest range of visible SLEDs, including the world’s only true BLUE & GREEN SLEDs, SLED-based Transceivers for Fiber Optic Gyroscope and Current Sensing applications.

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