Physics

World's first white laser demonstrated

World's first white laser demo...
This schematic illustrates the novel nanosheet with three parallel segments created by the researchers, each supporting laser action in one of three elementary colors
This schematic illustrates the novel nanosheet with three parallel segments created by the researchers, each supporting laser action in one of three elementary colors
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This photo collage shows the mixed emission color from a multi-segment nanosheet in the colors of red, green, blue, yellow, cyan, magenta and white
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This photo collage shows the mixed emission color from a multi-segment nanosheet in the colors of red, green, blue, yellow, cyan, magenta and white
Team leader Cun-Zheng Ning
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Team leader Cun-Zheng Ning
This schematic illustrates the novel nanosheet with three parallel segments created by the researchers, each supporting laser action in one of three elementary colors
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This schematic illustrates the novel nanosheet with three parallel segments created by the researchers, each supporting laser action in one of three elementary colors

Incandescent bulbs, LEDs, and CFLs may soon have to budge up because a new lighting technology is in town – white lasers. Using nanotechnology to create a bespoke semiconducting material, a team of scientists at Arizona State University (ASU) has developed a laser that can produce white light that is brighter and more efficient than LEDs.

Lasers are an ironic technology. Invented in 1960, the laser was hailed as a solution in search of a problem with only two obvious areas of application – death rays and lighting. Today, lasers run everything from DVD players to the internet, while the death rays are only just coming on line and the lighting, which is also new on the scene, is largely restricted to headlamps. The latter, in the case of Audi's laser headlamps, don't use white lasers as such, instead combining lensed blue lasers with LEDs.

At first glance, lasers seem like a great idea for lighting. They're intensely bright, efficient, and can form a beam that can travel for millions of miles and only spread out a few meters. There's a problem though – lasers cannot generate white light.

In 2011, Sandia National Laboratory produced white light by combining four large lasers into a single beam, but this was only a proof of concept demonstration and not a practical system.

This photo collage shows the mixed emission color from a multi-segment nanosheet in the colors of red, green, blue, yellow, cyan, magenta and white
This photo collage shows the mixed emission color from a multi-segment nanosheet in the colors of red, green, blue, yellow, cyan, magenta and white

The breakthrough came from ASU's Ira A. Fulton Schools of Engineering, where scientists came up with a semiconductor laser that can operate across the entire visible color spectrum. Normally, semiconductors only produce a single wavelength of light, but the ASU team developed a sheet of nanoscale semiconductor based on a quaternary alloy of ZnCdSSe, which is formed into three segments. These generate red, green, and blue lasers that combine to create a pure white light.

The team achieved this by adjusting the lattice pattern of the material, so the “lattice constant” or distance between the atoms in the pattern is set to produced the desired area. According to team member Zhicheng Liu, the tricky bit was to make sure the semiconductor crystals were of high enough quality and the lattices uniform across a given area. Getting the material to shine blue was the most difficult challenge, which was overcome by using nanotechnology to create the desired lattice first, then prompting it into the right alloy composition. The result was a single material with three different lattices and compositions.

The ASU team sees several applications for the white laser once it becomes practical. The most obvious is in lighting. The new laser can not only generate white light, but is also completely tunable across the entire spectrum – allowing it to radiate any desired color – and is brighter and more efficient than LEDs. Another application is in televisions and computer monitors. According to the researchers, the laser has a 70 percent greater color range that is more accurate and vivid. In addition, it could be used for a light-based version of Wi-Fi (or Li-Fi). Such a system would be ten times faster than Wi-Fi and ten to 100 times faster than experimental LED systems.

The white laser is currently in proof of concept form and several hurdles need to be overcome before the technology is practical. According to the team, the biggest of these is making it run off a battery. In its present form, the material runs off a separate laser, which pumps electrons into the semiconductor.

The team's results were published in Nature Nanotechnology.

Source: Arizona State University

9 comments
Nibblonian
Umm, "white lasers" have existed for at least 40 years. The Laserium light shows used a laser with a mixture of Argon and Krypton gas to create a multi-spectral ("white") laser output as far back as 1974.
Scott in California
In order combat AGW, governments should be investing in this to replace kerosene lighting around the world, in less-developed areas. Burning fuel for light is the worst possible idea for a planet of 7 Billion people.
McDesign
Interesting they didn't mention lumen-per-Watt figures, or even projections. As a commercial lighting engineer, our complete luminaire efficacies are steadily moving past 120 LPW for standard, inexpensive interior luminaires, with good color rendering (82+ CRI) and color quality (high R9) at CCTs of 3000-4000°K..
sk8dad
Awesome technology. Arrays of this could make laser displays finally a reality. Laser flashlights anyone?
Jeffry Mercer
Mitsubishi created a rear projection Tv called the LaserVue, which uses lasers. I'm not sure how there tech works, compared to this, but it does have pretty much all the colors as far as I can tell, since i have the tv. The tv was discontinued, in 2012, but it does look great for movie watch, but not so much for PC watching surfing.
Laserock
Very good Nibblonian, I can not believe they made the statement"Lasers cannot create white light". Where did that come from I have one myself.Also they are pumping this device with another laser--seems they still have a way to go but I guess it is a start.
Expanded Viewpoint
What I don't understand is how they can get three different wavelengths of light to resonate in the same cavity! It is the photons of light bouncing back and forth between two highly reflective surfaces and knocking electrons out of their pumped up (population inversion) state back down to ground state and creating even MORE photons that creates amplification, and if that cavity length is not tuned to the resonant frequency of that part of the EM spectrum, how can there be any gain in the medium? What am I missing here?? If the gain medium itself is not serving as the resonant cavity, then there have to be exterior mirrors set to a multiple of the wavelength and in parallel to about 1/3 wavelength, in order to get to that resonance point and thus lasing occurring. This comes straight out of some of my books about lasers and how they work. Are they trying to tell us that now somehow red, green and blue light are actually all of the same frequency and wave length?? Why wasn't I told about this before? Or, behind door number two, each lattice section in the gain medium must be it's very own miniature laser light generator, and that is why it has to be pumped into a population inversion via another laser rather than electrons from a power supply. Randy
tense0celot03
While a white laser beam from combining beams of the primary colors, seems hardly breakthrough news. (Hobbyist's have been able to accomplish, though bulky, working prototypes going back a few years now.) The idea of being able to use one laser module to put on all the color beams to be combined to form white seems like a step ahead in terms related to the reduced size,weight,and complexity involved in maufacturing such as laser. However I'm puzzled how white laser light would naturally replace LED lighting for the same purpose. LED's achieve white light by focusing blue LED generated light on a phosphor, which in turn is stimulated to emit the necessary complmentary colors to produce white. Current blue lasers could do the same job here as the blue LEDs, only more efficiently and to higher levels of light intensely. But how would white lasers improve on this? You'd be aiming the white lasers at phosphors which absorb photons of the colors comprising white light, only to produce a better scattered white light. I don't see any efficiency or any intensity benfits from such a scenario, since we know that phosphors that response to blue light are the most efficient. And as far as I understand, light emitting diodes and lasers are both most efficent at producing blue (well maybe it's green; but certainly producing red is the most inefficient of all.) Also the article states, "In addition, [white laser techology] could be used for a light-based version of Wi-Fi...). Are these people kidding? Sure visible light can be harnessed to carry information. But taking the place of a WiFi!? First of all how do you get visible light signals to penetrate opaque obstacles like walls, ceilings, doors,etc, etc" The whole system would operate on a line-of-sight only basis, similar to infrared remote tv controls but requiring far more critically exact alignment. Further, imagine a house guest getting up in the middle of the night, to find him/herself surrounded on-all-sides by all these white beams running back and forth like one would expect to come across only in a highly secured rare jewel repository.
JohnWuethrich
@tense0celot03 you might know lasers, but your networking knowledge is sub par. 1) the inability of light to pass through walls is actually what makes light based networking great. The application is A densely populated building, with RF based networks, the computers 8 rooms away that cant effective connect to the access point you are on still are providing interference to that AP. you can only get so many users per access point/channel before performance tanks, and you can only put so many access points as you have non overlapping channels. once you have to start reusing channels you need to make sure the 2 APs are sufficient distances from each other as to not cause interference to each other. this is actually why a tech that doesnt pass through the walls like light based networking is actually desirable in a lot of indoor densely populated areas. 2) you dont need a directional white laser beam to send data...at least from the "bulb"/access point to the computer. ambient is fine, if the intensity level of the light is varying thats all the computer needs to see to get data out of it. you wouldnt see these flashes either, they will be so fast it will appear to the human eye that its always on. if you have a suround sound reciver, look at the optical port on it at some time...it will look like a red light is on... just like LIFI its not actually "on" but rather pulsing so fast we cant see the moments its "off" The computer back to the "bulb" may be a laser but that might not be necessary either, photo sensors have gotten really good, to the point the computer might just need an IR led on the top of the screen. it could be done with a normal led too but IR on the device you are looking directly at would be more comfortable for the user... aka its not blinding you