Ask an Expert: How do lasers work?
In a memorable scene in the classic James Bond film “Goldfinger,” Bond is strapped to a table, inches away from a laser that threatens to slice him in two. Bond survived, and 50 years later, lasers have shifted from movie gag to practical tool in many industries.
While lasers have gone mainstream in applications like the barcode reader at your local grocery store, they’re also used in the most advanced physics experiments around fusion energy, and many other applications in between.
Today, many laser systems achieve peak performance by using specialty laser glass as an amplifier. Light, compact, and cost-effective to produce, these glasses are found in many of the world’s largest laser architectures, as well as handheld scopes, medical equipment, and navigation systems in driverless cars.
Ahead of Photonics West, I sat down with Simi George, one of SCHOTT’s laser glass experts, to explore the technologies powered by the laser glasses on display at the show.
How do laser glasses work and what are their advantages?
Laser glasses act like capacitors, helping lasers achieve high energy and peak power. Researchers pump laser glass slabs with energy, and then shoot a beam of light through them. The light collects energized ions in the glass, and the laser grows in power as it passes through each slab. The laser’s total energy grows to far greater than its original state.
The National Ignition Facility at Lawrence Livermore National Laboratory in California and the University of Rochester’s Laboratory for Laser Energetics rely on strong laser glasses capable of being pumped with energy without breaking or melting. Lasers in these test labs can generate huge amounts of power – enough energy to exceed the output of all U.S. power plants combined.
How are laser glasses produced?
Like other glasses: Raw materials are melted together, shaped into rods or slabs, annealed and cooled, and finally polished and cleaned. Phosphate and rare earth elements, such as erbium, ytterbium, and neodymium, are part of the glass’s chemical composition, and these elements help the glass hold that pent-up energy.
Laser glasses are produced more cost effectively and faster than crystals, which is one reason they’re used in large research settings.
How else does laser crystal differ from glass?
A crystal has an ordered chemical structure that gives it more strength to stand up to increased pulse repetition rates. However, growing and refining crystals is a time-consuming and arduous process, especially for laser systems with large apertures. Crystals also require active cooling because exposure to high temperatures can lead to beam instability, and these extra components increase the size and weight of a laser architecture.
New laser glasses, like SCHOTT’s LG-960 formulation, have tighter chemical structures and won’t fracture when pumped with more energy. Laser glasses can be uniformly doped with rare earth elements, resulting in greater performance. Because laser glass can be manufactured in rods with small dimensions (about the diameter of a quarter) without temperature stabilization, the material can be used in compact architectures that demand efficiency, exceptional beam quality, and accuracy.
What are some examples of how laser glass is used?
Besides research, lasers are common in range finding tools and applications. Professional baseball teams use laser range finding to position fielders for better defensive alignments in order to exploit an opponent’s weaknesses (or capitalize on their own strengths). Hunters often rely on range-finding scopes and hand-held devices, too.
Dermatologists can clear up their patients’ acne or soften wrinkles with laser treatment, and cosmetic specialists use lasers for tattoo removal. Radial keratotomy corrects nearsightedness with fine-tuned laser pulses. Laser glasses perform well in these applications because they’re lightweight and compact.
Improvements in laser glasses provide tools in medical offices, on the golf course, and for industrial manufacturing with the necessary power to achieve reliable performance.
What applications will lasers power in the future?
LiDAR systems in driverless cars, for one. Car companies are considering LiDAR with eye-safe wavelengths, and laser glasses could make those systems practical and economically feasible.
Another is surgery. Instead of using a scalpel, doctors will be armed with finely calibrated laser tools in the operating room. Incisions made by lasers will be more precise and bleed less, and wounds will be cauterized by the heat of the laser. Scarring and other skin blemishes caused by surgery can be eliminated with similar laser systems.
Finally, another area of recent interest is pushing laser systems to even high peak power levels by reducing the pulse length by several orders of magnitude. This new field requires new glass compositions that have special emission properties, an area of current development at SCHOTT.