Vertical-cavity surface-emitting lasers have been moving information in technology for decades, but the developers of smartphones and other handheld devices have created new uses for the technology that are helping power new features.
VCSELs — an acronym that is pronounced “vixels” in the tech world — are small semiconductor devices that emit light vertically and measure the depth at which that light is reflected. That depth-sensing technology allows smartphones and similar technology to turn off the screen when people raise devices to their faces, so they don’t accidentally push buttons with their face while speaking. Apple uses VCSEL technology to power some of its newest features, such as Face ID, Animoji, portrait mode selfies and the ARKit augmented reality platform.
“They essentially enable a 3-D camera,” Finisar Vice President of New Markets Craig Thompson said of the way Apple uses VCSELs. “We’ve gotten to the point now where the basic camera lens is able to capture both the 2-D visible light image as well as the infrared depth information that it can see.”
He said now that Apple and other mobile device manufacturers have enabled that basic functionality, they’re open to expanding what the VCSELs can do.
“Now they’re opening it up to developers to go crazy and develop these applications that use that depth information that comes from a 3-D camera,” Thompson said. “It’s small, it’s easy to integrate now and people want to put it everywhere, so we’re very excited about the opportunities.”
VCSELs can be different sizes, but the ones produced for Apple, which is what Finisar Corp. will be manufacturing at its new Sherman facility in the former MEMC building, will be approximately one millimeter by one millimeter in size, which is around 50 times the size of a typical VCSEL.
“The VCSELs provide a number of different functions, but in general what we’re seeing in this 3-D sensing market (is) anything from a simple distance measurement — a more accurate proximity sensor — all the way to a high resolution 3-D camera,” Thompson said, noting the technology is also being incorporated into the automotive industry. “(It’s) being adopted for real-time driver monitoring inside of the car. It’s being also adopted for the sensors that go around a car — more high resolution accurate 3-D sensing of pedestrians, obstacles, other cars, that type of thing.”
He compared the impact VCSELs will have on smartphones to the way GPS chips and gyroscopes have advanced functionality in them.
“I think we’ve barely scratched the surface of applications for the technology,” Thompson said. “And over the next few years all sorts of great ideas will be generated for using it.”
Thompson also explained the VCSEL production process during an exclusive interview with the Herald Democrat.
“Mostly people will think of fabs (fabrications) like this for silicon devices like a microprocessor or a seamless image sensor on a camera are big silicon wafers — that’s not what’s done here,” Thompson said. “We work in more exotic materials that generate light with electrical input. The material system that we work with mostly here is called gallium arsenide. We use a small gallium arsenide wafer to grow and pattern the laser structure.”
Thompson said the company then grows the basic structure of the laser in a reactor, followed by the use of “fairly standard semiconductor processes” to define the laser structure.
“That’s all done in automated batch processes,” Thompson said. “Where there’s a fairly heavy labor process to this is in all of the layer process steps where we take the wafer out of these big automated tools and we start to test them. We will get many thousands of individual lasers on a single wafer. We have to individually test each one a number of times to ensure quality, reliability and performance.”
He said that testing of the wafers is done through “a lot of handling and skilled operation” that weeds out the lasers that don’t work correctly.
“In the end, they end up being a fairly tiny laser chip that then gets integrated into higher level assemblies that go inside a phone,” Thompson said.
As the Finisar vice president said, each wafer produced by the company can contain thousands of VCSELs. Apple’s latest iPhone X model contains three VCSELs on its screen.
“Just to give you a sense of the importance and scale, Apple alone this quarter will consume 10 times more VCSELs than were produced for the entire world prior to the introduction of iPhone X,” Apple Chief Operating Officer Jeff Williams said in a phone interview with the Herald Democrat last month.
Each VCSEL produced for Apple contains more than 300 emitters of light, while a typical VCSEL contains fewer than four emitters of light. And each one of those emitters of light, which is what is used in depth-sensing technology, is between eight and 10 microns in diameter; a typical human hair is about 100 microns thick.