{"id":9002,"date":"2016-06-14T06:24:07","date_gmt":"2016-06-14T06:24:07","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=9002"},"modified":"2016-06-14T06:24:07","modified_gmt":"2016-06-14T06:24:07","slug":"new-approach-to-microlasers","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/new-approach-to-microlasers\/","title":{"rendered":"New approach to microlasers"},"content":{"rendered":"

Technique for \u201cphase locking\u201d arrays of tiny lasers could lead to terahertz security scanners.<\/strong><\/em><\/span><\/p>\n

\"Researchers<\/a>
Researchers at MIT and Sandia National Laboratories have designed a device that is an array of 37 microfabricated lasers on a single chip. Its power requirements are relatively low because the radiation emitted by all of the lasers is \u201cphase locked,\u201d meaning that the troughs and crests of its waves are perfectly aligned.
Courtesy of the researchers<\/figcaption><\/figure>\n

CAMBRIDGE, Mass.<\/strong> —\u00a0Terahertz radiation \u2014 the band of electromagnetic radiation between microwaves and visible light \u2014 has promising applications in security and medical diagnostics, but such devices will require the development of compact, low-power, high-quality terahertz lasers.<\/span><\/p>\n

In this week\u2019s issue of\u00a0Nature Photonics<\/em>, researchers at MIT and Sandia National Laboratories describe a new way to build terahertz lasers that could significantly reduce their power consumption and size, while also enabling them to emit tighter beams, a crucial requirement for most practical applications.<\/span><\/p>\n

The work also represents a fundamentally new approach to laser design, which could have ramifications for visible-light lasers as well.<\/span><\/p>\n

The researchers\u2019 device is an array of 37 microfabricated lasers on a single chip. Its power requirements are so low because the radiation emitted by all of the lasers is \u201cphase locked,\u201d meaning that the troughs and crests of its waves are perfectly aligned. The device represents a fundamentally new way to phase-lock arrays of lasers.<\/span><\/p>\n

[pullquote]In Hu and his colleagues\u2019 array, each laser generates an electromagnetic field that induces a current in the lasers around it, which synchronizes the phase of the radiation they emit.[\/pullquote]<\/p>\n

In their paper, the researchers identified four previous phase-locking techniques, but all have drawbacks at the microscale. Some require positioning photonic components so closely together that they\u2019d be difficult to manufacture. Others require additional off-chip photonic components that would have to be precisely positioned relative to the lasers. Hu and his colleagues\u2019 arrays, by contrast, are monolithic, meaning they\u2019re etched entirely from a single block of material.<\/span><\/p>\n

\u201cThis whole work is inspired by antenna engineering technology,\u201d says Qing Hu, a distinguished professor of electrical engineering and computer science at MIT, whose group led the new work. \u201cWe\u2019re working on lasers, and usually people compartmentalize that as photonics. And microwave engineering is really a different community, and they have a very different mindset. We really were inspired by microwave-engineer technology in a very thoughtful way and achieved something that is totally conceptually new.\u201d<\/span><\/p>\n

Staying focused<\/strong><\/span><\/p>\n

The researchers\u2019 laser array is based on the same principle that underlies broadcast TV and radio. An electrical current passing through a radio antenna produces an electromagnetic field, and the electromagnetic field induces a corresponding current in nearby antennas. In Hu and his colleagues\u2019 array, each laser generates an electromagnetic field that induces a current in the lasers around it, which synchronizes the phase of the radiation they emit.<\/span><\/p>\n

This approach exploits what had previously been seen as a drawback in small lasers. Chip-scale lasers have been an active area of research for decades, for potential applications in chip-to-chip communication inside computers and in environmental and biochemical sensing. But as the dimensions of a laser shrink, the radiation the laser emits becomes more diffuse. \u201cThis is nothing like a laser-beam pointer,\u201d Hu explains. \u201cIt really radiates everywhere, like a tiny antenna.\u201d<\/span><\/p>\n

If a chip-scale laser is intended to emit radiation in one direction, then any radiation it emits in lateral directions is wasted and increases its power consumption. But Hu and his colleagues\u2019 design recaptures that laterally emitted radiation.<\/span><\/p>\n

In fact, the more emitters they add to their array, the more laterally emitted radiation is recaptured, lowering the power threshold at which the array will produce laser light. And because the laterally emitted radiation can travel long distances, similar benefits should accrue as the arrays grow even larger.<\/span><\/p>\n

\u201cI\u2019m a firm believer that all physical phenomena can be pros or cons,\u201d Hu says. \u201cYou can\u2019t just say unequivocally that such-and-such a behavior is universally a good or bad thing.\u201d<\/span><\/p>\n

Tightening up<\/strong><\/span><\/p>\n

In large part, the energy from the recaptured lateral radiation is re-emitted in the direction perpendicular to the array. So the beam emitted by the array is much tighter than that emitted by other experimental chip-scale lasers. And a tight beam is essential for most envisioned applications of terahertz radiation.<\/span><\/p>\n

In security applications, for instance, terahertz radiation would be directed at a chemical sample, which would absorb some frequencies more than others, producing a characteristic absorption fingerprint. The tighter the beam, the more radiation reaches both the sample and, subsequently, a detector, yielding a clearer signal.<\/span><\/p>\n

Hu is joined on the paper by first author Tsung-Yu Kao, who was an MIT graduate student in electrical engineering when the work was done and is now chief technology officer at LongWave Photonics, a company that markets terahertz lasers, and by John Reno of Sandia National Laboratories.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

The researchers\u2019 laser array is based on the same principle that underlies broadcast TV and radio. An electrical current passing through a radio antenna produces an electromagnetic field, and the electromagnetic field induces a corresponding current in nearby antennas.<\/p>\n","protected":false},"author":6,"featured_media":9003,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-9002","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/06\/MIT-Laser-Arrays_0.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/9002","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=9002"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/9002\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/9003"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=9002"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=9002"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=9002"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}