<story><title>World&apos;s first white laser</title><url>https://asunews.asu.edu/20150728-worlds-first-white-laser</url></story><parent_chain><item><author>prewett</author><text>Interesting, although a bit light on details.  From the article it would seem like the laser is essentially three lasers (red, green, blue) coupled together, and by changing the amount of R, G, and B you tune the color.  I&amp;#x27;m curious how coherent the R, G, and B are with each other.  A true &amp;quot;white&amp;quot; laser would be coherent on all frequencies, but I&amp;#x27;m guessing that&amp;#x27;s pretty hard to accomplish (so limited holography uses).&lt;p&gt;I question the claim that &amp;quot;lasers are brighter, [and] more energy efficient [than LEDs],&amp;quot; though.  I&amp;#x27;m assuming LEDs are much more efficient (more lumens of output per watt of input), but I&amp;#x27;d believe that the laser might be more intense (more lumens&amp;#x2F;m^2).  Typically lasers are pretty ineffient.  [1] reports efficiencies of 7% - 8.9% with semiconductor lasers.  Wikipedia [2] appears to be reporting LED efficiencies of 20% - 39%, and one research group [2] reports on getting over 100% efficency, with an LED emitting &amp;quot;more optical power than the electrical power it consumes,&amp;quot; although at very low power levels.&lt;p&gt;[1] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.laserfocusworld.com&amp;#x2F;articles&amp;#x2F;print&amp;#x2F;volume-48&amp;#x2F;issue-08&amp;#x2F;world-news&amp;#x2F;semiconductor-lasers-green-laser-diode-emits-at-536-nm.html&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.laserfocusworld.com&amp;#x2F;articles&amp;#x2F;print&amp;#x2F;volume-48&amp;#x2F;issu...&lt;/a&gt;&lt;p&gt;[2] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Light-emitting_diode#Efficiency_and_operational_parameters&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Light-emitting_diode#Efficienc...&lt;/a&gt;&lt;p&gt;[3] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2012-03-efficiency.html&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2012-03-efficiency.html&lt;/a&gt;</text></item></parent_chain><comment><author>logfromblammo</author><text>Whenever the word &amp;quot;white&amp;quot; is used in a scientific or quasi-scientific context, it should probably be specified whether the speaker means &amp;quot;perceived by the human eye to be white&amp;quot;, or &amp;quot;emitting a continuous spectrum across all frequencies of visible light&amp;quot;, or something in between.&lt;p&gt;A tricolor LED and a white (phosphor-based) LED can both emit light perceived by a human to be white when viewed directly.  But the former is actually only trichromatic, and will have different color rendering properties when reflecting from nearby objects.&lt;p&gt;An R+G+B laser is not a white laser.</text></comment>
<story><title>World&apos;s first white laser</title><url>https://asunews.asu.edu/20150728-worlds-first-white-laser</url></story><parent_chain><item><author>prewett</author><text>Interesting, although a bit light on details.  From the article it would seem like the laser is essentially three lasers (red, green, blue) coupled together, and by changing the amount of R, G, and B you tune the color.  I&amp;#x27;m curious how coherent the R, G, and B are with each other.  A true &amp;quot;white&amp;quot; laser would be coherent on all frequencies, but I&amp;#x27;m guessing that&amp;#x27;s pretty hard to accomplish (so limited holography uses).&lt;p&gt;I question the claim that &amp;quot;lasers are brighter, [and] more energy efficient [than LEDs],&amp;quot; though.  I&amp;#x27;m assuming LEDs are much more efficient (more lumens of output per watt of input), but I&amp;#x27;d believe that the laser might be more intense (more lumens&amp;#x2F;m^2).  Typically lasers are pretty ineffient.  [1] reports efficiencies of 7% - 8.9% with semiconductor lasers.  Wikipedia [2] appears to be reporting LED efficiencies of 20% - 39%, and one research group [2] reports on getting over 100% efficency, with an LED emitting &amp;quot;more optical power than the electrical power it consumes,&amp;quot; although at very low power levels.&lt;p&gt;[1] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.laserfocusworld.com&amp;#x2F;articles&amp;#x2F;print&amp;#x2F;volume-48&amp;#x2F;issue-08&amp;#x2F;world-news&amp;#x2F;semiconductor-lasers-green-laser-diode-emits-at-536-nm.html&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.laserfocusworld.com&amp;#x2F;articles&amp;#x2F;print&amp;#x2F;volume-48&amp;#x2F;issu...&lt;/a&gt;&lt;p&gt;[2] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Light-emitting_diode#Efficiency_and_operational_parameters&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Light-emitting_diode#Efficienc...&lt;/a&gt;&lt;p&gt;[3] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2012-03-efficiency.html&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2012-03-efficiency.html&lt;/a&gt;</text></item></parent_chain><comment><author>sigterm</author><text>Not sure what you mean by &amp;quot;how coherent the R, G, and B are with each other&amp;quot;. They are not coherent, since they have different frequencies.</text></comment>