Helping Photonics Markets See the Light

John McCauley, Product Specialist, Ophir Photonics Group

The applications of lasers and light sources and the impacts they have had are too numerous to count. Recent trade studies reveal that the photonics industries an important economic driver in both U.S. and global markets. A doubling of this industry is expected from 2013 to 2020 – only seven years! There doesn’t seem to be an end in sight to the ways light sources are being applied.

It makes you wonder if Albert Einstein, who first theorized about stimulated emission of radiation in 1917, or Charles Townes, who first worked with “MASERs” in the late 1950’s, had any idea where this ever-evolving technology would take us. Today, few can imagine a world without these light tools.

It shouldn’t be a surprise to anyone that to make the most of any tool, the designer, the operator, and the technician of that tool needs to understand how it is behaving during design, operation, and maintenance. When light is being used as the tool, this principle is no different. Throughout the years, Ophir-Spiricon has helped companies in many market segments understand how their light tools are performing and aided them in improving their product and the environments in which they have been used. Let’s take a look at some of the many uses…

Lasers are used in a number of different medical procedures today. High-energy pulsed laser light can remove tattoos by breaking up the ink underneath the skin and safely sending it into the bloodstream to be removed by the body. Pulsed lasers are also used to help improve our vision through refractive surgery and cataract surgery procedures. Laser lithotripsy is a procedure used to remove kidney stones.

As you can imagine, when a laser is used to correct something wrong in the human body, the performance of those lasers is something that needs to be monitored especially carefully so unwanted damage doesn’t occur. The development of these lasers include the use of beam profiling systems to show the shape and size of the lasers in the early stages of that laser and periodically after the laser is put into service. More frequently, the laser’s output power or energy is measured to ensure that the laser is operating within the guidelines of the governing entity (either the hospital or the FDA).

Along the same lines, several medical devices are manufactured with the help of a laser. In these cases, a laser is used to weld or cut materials during the manufacturing process. For example, a seam weld is put along the outside of a case for a pacemaker by use of a pulsed Nd:YAG or fiber laser. In another example, stints are implanted and expanded with the use of a balloon inside of a weak artery during a coronary angioplasty. Today, stints are usually produced by cutting patterns into a tube with a highly focused laser.

In both of these cases, the regulation of these medical devices is fairly thorough since they are implanted into the body. Regular power and energy checks are performed on these lasers to ensure consistent performance. Beam profiling is also performed during application development and at several stages during the qualification of these laser systems. More and more, end users are also applying beam profiling practices as a way of continuously monitoring lasers during production.

Photovoltaic technology is a rapidly emerging technology that harnesses the energy of the sun and converts it to electrical energy. During the production of the solar cells that perform this conversion, several different laser processes are performed. Green or UV lasers are used to dice the silicon substrate of the cell. Short-pulsed green or UV lasers are also used for drilling 10-80 micron diameter holes into the silicon wafer layers. A process known as doping is performed with a continuous wave Green laser and creates more efficient cell emitters. Green and UV lasers are also used during edge isolation processes, which scribe down into several layers of the photovoltaic cell.

With these precise tolerances, there is no doubt that the laser performance is extremely important. Laser power and energy and beam profiles are taken frequently to ensure that the laser’s performance is consistent over time and the data is then used to better determine when maintenance on the laser system needs to be conducted.

When discussing lasers that are being used for our nation’s defense, we can only talk in generalities. Today there are ways lasers are being used in this arena that we will only learn about years from now. One application of the high-powered laser that was recently introduced by the U.S. Navy was the use of a fiber laser of hundreds of thousands of watts in laser power being used to disable drones (or any other flying object), or land or sea vehicles. With this system, lasers are used to lock onto the target, to disable the target’s camera (where applicable), and then apply multiple kilowatts of laser power to the target, which eventually results in the target being rendered useless, often being completely destroyed.

In this case, there was no commercial way to measure the output power of the laser during development of the laser sources. So we developed the first commercially available 100kW laser power measurement system, which then lead to the most recent version that measures up to 120kW. The solution proved to be instrumental in this weapon’s development.

Another technology that has grown in leaps and bounds is the use of invisible wavelengths along the electromagnetic spectrum for purposes of imaging. This technology requires relatively long wavelengths, compared to the shorter wavelengths at which most lasers operate. Most applications involve medical imaging and security systems.

For example, a technique known as Terahertz Pulse Imaging (TPITM) — because of its ability to determine differences in soft tissues, water content, and cancer markers — gives us high-resolution images that have not been able to be seen before. This has been important in the earlier detection of cancer and the erosion of a tooth’s enamel layers.

Light at these wavelengths can also be used for imaging hidden objects that normally could not be imaged. Terahertz (THz) wavelengths, for instance, are used in products in airports to detect metallic, non-metallic, liquid, and gaseous objects that could be used as weapons or explosives. Other applications use Ophir- Spiricon’s flagship camera, the Pyrocam™ (currently in its fourth generation), as a thermal-electric technology that images these THz wavelengths. Since it is a camera, it delivers images at a near real-time rate, showing changes in these signals during short durations. Ophir’s thermopile technology is also used to measure the output power of these signals, which are typically very low output powers.

Lasers of all wavelengths have been used for material processing in industrial applications for decades. However, as true as this is, new ways and new laser technologies are continually being developed and applied at a rate that allows us to still consider it as an emerging technology.

Two laser categories have most recently attributed to successes in laser processing: high-powered lasers, and short-pulse lasers. High-powered lasers should actually be referred to as “higher and higher powered lasers” since there does not seem to be an end in sight to where laser powers will end up. 10- micron wavelength lasers (CO₂ lasers) have been one of the industry’s workhorses for quite some time and there are literally tens, possibly even hundreds, of thousands of CO₂ lasers being used worldwide. They are typically a reliable technology that is relatively easy to maintain. Ophir- Spiricon’s ModeCheck™ product was introduced in 2009 as an affordable, simple way to measure the real-time performance of these lasers at the work piece. Coupled with an Ophir water-cooled thermopile sensor, the laser user and technician can receive a comprehensive analysis of how the laser is being applied to their process.

In addition to the CO₂ laser, 1-micron wavelength lasers (generated by crystals such as Nd:YAG or disc, diodes, or active fiber optic cables), have also been around for years. These technologies continue to show advancements with increased powers, wall plug efficiency, and quality. As powers increase, thermal effects on the system in which the laser source is integrated become more of a factor. Thermal effects are also an issue when the laser system’s components are not fully protected against the relatively dirty environments where they are used.

A phenomenon that has historically been a problem for these high-power lasers is known as “focus shift.” This is when thermal effects within the laser system cause a deformation on the lens and other optics cause a change in the position of the focused spot as it is applied to the material being processed. When that happens, the intended result is lost. Ophir-Spiricon introduced the BeamWatch® product, which provides a laser technician with the ability to view shifts in the focused spot with multiple data points per second. Since BeamWatch is a non-contact beam profiling system, there is no upper limit to the laser that can be measured. BeamWatch gives the technician all relevant data for setup or maintenance of the system, or gives the laser operator a quick, simple way of analyzing the laser with no-go parameters during day-to-day operations.

As we reflect on the year of light and all of the places where light has taken us so far, isn’t it interesting to think of where these promising and continually-evolving technologies will take us in the future? With all of the potential that this industry has, there’s no telling what’s next. But one thing will remain the same between now and then…understanding this sometimes-mysterious tool will be vital to the successes in which it is used. And we will be there to help.