[MURG] cheese @ 266 nm

[Eugen Leitl]

http://optics.org/articles/news/9/12/1/1

Lasers turn cheese into art
3 December 2003

A pulsed ultraviolet laser shows potential for cutting patterns in cheese.

It seems that there.s no end to the type of materials that scientists will
consider cutting with a laser. Researchers from the University of
Wisconsin-Madison in the US astonished delegates at the recent ICALEO show in
Florida when they announced that they had machined cheese into intricate
shapes with a Q-switched Nd:YAG.


Cheesy solution

.Wisconsin is a big dairy and cheese making state and we were approached by a
company that wanted to know if we could use a laser to cut thin slices of
cheese at high speed,. Xiaochun Li, one of the researchers, told optics.org.
.One motivation is the ability to cut cheese into fancy shapes that appeal to
kids, such as a dinosaur or letters. The fast food industry is very
interested in that idea..

Li and his co-worker Hongseok Choi and assessed the suitability of an
ultraviolet laser for cutting and drilling slices of mild cheddar that were a
few millimeters thick. Central to the study was the investigation of which
wavelength and energy fluence give the best results.

Experiments with the third (355 nm) and fourth (266 nm) harmonics of a
Q-switched Nd:YAG laser demonstrated that a 266 nm beam is undoubtedly the
preferred choice.

The 266 nm beam gave much deeper, cleaner cuts while signs of damage of
burning can be seen in cuts made with a 355 nm beam, say Choi and Li in their
ICALEO paper. The reason for the different cutting performance is the optical
properties of the fat and protein in the cheese. The light absorption of
protein is very strongly dependent on wavelength and about 100 times stronger
at 150 nm compared to 300 nm.

.Basically, the cutting process is cold laser ablation, like that in laser
eye surgery,. said Li. .At 266 nm it gives a very good clean cut, although
going deeper than 10 mm is difficult..

To date, the team has focused on making high quality intricate cuts in 2.5 mm
thick mild cheddar. Patterns such as the University of Wisconsin-Madison
motif were drawn on CAD software and then transferred to a workstation
consisting of a flashlamp-pumped Nd:YAG laser and an xy table holding the
cheese. The laser produced 10 ns long pulses with an average power of up to
10 W at 355 nm and 3.5 W at 266 nm.

The key limitation of the technique seems to be its slow cutting speed, less
than 1 mm per second, which is restricted by the slow (20 Hz) repetition rate
of the laser. Li says that a UV laser with a higher repetition rate and
output power could significantly increase the depth and speed of the cutting.

He believes that the work could point to a new and lucrative market future
for lasers. .The food industry could be a huge market for lasers just like
the semiconductor industry,. Li said. .We.ve also been asked to cut meat and
potato with a laser but we haven.t done that yet..

.  ICALEO is an annual laser materials processing show that is organized by
the Laser Institute of America (LIA) and takes place each autumn. This year
more than 450 attendees from 23 countries visited the event in Jacksonville,
Florida, between 13-16 October. ICALEO 2004 will take place in San Francisco
between 4-7 October. 

-- Eugen* Leitl <a href="http://leitl.org">leitl</a>
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