This page holds videos and images for some experiments on cutting ice
with various lasers. These results have not to date been published, but
some were incorporated into the proposals that eventually became the
RELIC program. Note that, as the videos are on the large side, they are
set to not load until clicked.
If you have any questions, please contact Merlin or Joey.
###CO2 laser: 10.6 μm They’re a common sight in
architecture modeling studios, makerspaces, and other workshops: Universal
Laser Systems’ laser cutters, which use a CO2
laser—emitting around 100 watts of 10.6 μm light—to etch glass and cut
thin sheets of plastic, wood, and cardboard. Which inevitably raises the
question: what could they do to ice?
Our first foray to answering this question: freeze some tap water into
small cylinders of ice (very roughly 15 mm in diameter), laser-cut–on
the same machine!–some acrylic forms to hold these tiny ice cores over a
glass meltwater-catching plate, and try some cutting. This video, taken
in slow motion by a somewhat focus-challenged action cam sitting on the
cutting bed, shows that the laser can make short work of cutting through
the cylinder.
A second slice, this time shown at normal speed by a camera looking
through the laser cutter’s glass lid. The ice cylinders are now toted to
the cutter in a liquid nitrogen cooler, which cuts down on the melting
but also causes aggressive frosting. The blue-tipped glass slide serves
as a sacrificial beam block.
The extremely short penetration depth of this long-wavelength light is
demonstrated by cutting a Minnesota M logo out of a flat disc of ice a
few millimeters thick.
###Nd:YAG laser: 1.064 μm While CO2 lasers are clearly
able to quickly and effectively slice through ice, their long
wavelengths cannot be efficiently transmitted through current optical
fibers; combined with their physically large sources involving
gas-filled glass tubes, this limits their usage to situations where you
can bring the ice to the laser, instead of the other way around.
Fortunately for borehole applications, a wavelength of 1.07 %mu;m offers
both effective fiber transmission and a wealth of economical high-power
fiber lasers. Back in 2019, our lab’s only laser exceeding 10 W of
sustained output power was an older neodymium-doped YAG laser, so our
demonstrations were limited; still, they were enough to illustrate the
potential of laser cutting.
Seen from above through an angled mirror, a cylinder of tap water ice 1
inch in diameter is moved downward into the path of a 90 watt NdYAG
laser beam. The ice sample had been cooled in liquid nitrogen prior to
cutting, generating internal cracks and surface frost, but the cutting
experiment is performed at room temperature. The red light seen is a
visible guide laser which helps to aim the higher-power infrared beam. A
note for the impatient: since the laser (incident from top in the mirror
view) is cutting into the bottom of the ice sample, while we observe
from nearly the exact opposite side, the cut is not visible until late
in this video.
A disc of ice, about 2 inches in diameter and around 5 mm thick, with a
fresh Nd:YAG laser-cut slice traveling outward from a previously
laser-drilled hole. This cut was recorded as about 1.5 mm wide, slightly
larger than the diameter of the beam, although the room-temperature
conditions around this experiment made precise measurement difficult.
An NdYAG laser is a big beast, much too large and heavy to move around a
sample, but the wedge-cutting concept can be illustrated by inverting
the arrangement and moving a cylinder of ice around in front of the
beam. Here, a neat wedge is cut out of a 3 inch tap-water core.
###Fiberlaser: 1.07 μm And so it begins: time to put our new fiber
laser through its paces…
One of the first wedges cut under the RELIC program, with a Yb-doped
fiber laser operating at about 300 W (out of a 1 kW capability.) This is
early days yet, but notice that the 2 inch tap-water ice core remains
stationary while the laser’s delivery fiber maneuvers around it. The
speed of cutting is limited by the wobbly prototype motion arm.
