Femtosecond Lasers Used To Color Metals

Maximum Prophet writes "An optics professor and a postgrad have developed a way to use ultra-short pulses of laser light to etch nano features into the surface of metals so that they can absorb or reflect specific wavelengths of light. This is very similar to the way that butterflies get the color in their wings."

Re:Colour me cynical

[fishybell]

I asked by dad, a tenured professor / associate dean at the local university, and he said it depends on the professor. Most professors, and all the good ones, are in it for the knowledge and the spreading thereof. Any papers he publishes have the grad students listed first (by order of work done on the project) and his name last. The scientific journals know that the professor's name is last (and of course, followed by the telling doctoral title) as most professors want to give the credit to those who need it most; the students.

Most tenured professor, and a good deal of tenure track professors aren't vying for personal fame, they're vying for good results. They want their students to succeed in the industry. They don't need their own CV to glow extra bright unless they're planning on starting their own company using the technology. They also don't need the limelight as much as they work with two to four teams of students each semester on various grants. Some grants, of course, take significantly longer than a semester but each year the professor's CV grows by pages while the students' are just getting into page two.

Say what you like, but most professors really aren't out to jilk the student, they're out to help the students.

Re:WOW!

[Rei]

Why did you link an article that argued against your point? The article says that the bright color of the upper sides of the wings is due to interference, and that only the dull underside is due to pigments.

Most of the colors in my parrot are due to the same diffraction effect from the spacing of the barbs in his feathers. There are two interesting things you can observe. One, when you get him thoroughly soaked in a shower, he becomes all dull except for the yellow feathers on his head (which are pigmented); it's a pretty dramatic color change. Two, when the tips of a feather passes in front of another feather, you get neat Moire patterns.

Re:WOW!

[Zymergy]

There is some confusion here, Please first refer to this: http://en.wikipedia.org/wiki/Additive_color [wikipedia.org] and to this http://en.wikipedia.org/wiki/Interference_filter [wikipedia.org]
Actually, butterfly wing-scales are the color of the underlying wing cells that produce the scales (and not blue, etc..) The scales are actually not blue, they are probably the color of butterfly skin cells.
The intense powder blue colors observed in butterfly scales are caused by Optical Interference Filter phenomenons in the microscopic slits in the surface of the scales *only* and not from a pigment or dye. Think of it as a mirror that adsorbs light in all optical wavelengths and reflects only the shades of blue observed. If you were to shine light of different wavelengths like pure green or red, the wings would be appear dark or mostly black as they absorb wavelengths of light that are not those specific to those shades of blue light they reflect.
Traditional colors (in most things we see daily) are caused by pigments and dyes (subtractive color) or from CRT/LCD/Plasma display RGB techniques (additive color).
This 'new' technology using "Femtosecond Lasers" creates precise cuts in the surface of metals (or other substances), to create these precise interference pattern slits to produce brilliant colors. These slits act as a slit interference light reflector/absorber as they brightly reflect specific wavelengths like a selective mirror and adsorb others. This method is vastly more efficient than colored subtractive filters and therefore produce colors far more intense than any pigment or dye could produce.
All butterfly and moth scales are made of non-living insect cuticle. Insect cuticle comes from epithelial cells and is made up of chitin and protein. These Chitins and Proteins are not necessarily colored or pigmented. Their observed 'colors' virtually all come from their nano-scale *structures* which have microscopic optical interference reflectors/absorbers. Some insects use these 'scales' to very efficiently absorb light to stay warm in sunlight and the light reflected is very brilliant and is essentially a mirror to particular wavelengths.

The important thing FTA is that now mankind has learned how to use lasers to be able to modify the surface of metal substrates (of whatever native 'color') to adsorb and reflect specific wavelengths of light in the visual range. This can be used to make better coatings and even better camouflage. The USAF already uses similar technology in their "stealth paint" with radar-adsorbing interference filtering "stuff" in the paint itself (as well as the shape). This new technology reads to me to to be a good step in the direction of daylight stealth and camouflage, but just like the butterfly wings. Once touched or structurally affected, the surface structure changes and so does the color absorption/reflection. This is why it is very necessary to carefully clean stealth aircraft just before missions, otherwise combustion particles, dust, etc.. can reflect radar and defeat some of the paint's stealth properties. This would have a similar optical effect on the "Femtosecond Laser-colored Metals" referred FTA.

hmm

[sonoronos]

Call me a skeptic, but I find it hard to believe that surface etching can cause the photon absorption characteristics of the material to change, a property which has more to do with the atomic structure of the material than its gross features. This leads me to believe that the color properties of the material are probably due to anisotropic reflection - meaning that the difference between "light" and "dark" between frequencies is the difference between "reflective" and "matte". Therefore, the intensity of the color produced by this method is limited by some mean function of available light, viewing angle, and the minimum feature size - which is limited by the material and not by the laser being used. Therefore, I would expect a material like gold, which exceptional stability to have the most intense colors providable by this method, which is a bit ironic, considering the subject of the article. I don't see General Lee Orange "painted by laser" onto a 1969 Dodge Charger any time soon.

Re:hmm

[OneSmartFellow]

OK, you're a skeptic. Index of refraction is everything.

Re:Colour me cynical

[Anonymous Coward]

Already invented, [wikipedia.org] if you consider fused aluminum oxide to be aluminum.

Re:WOW!

[ozbird]

I think you meant to link to the diffraction grating [wikipedia.org] article.
Diffraction gratings using parallel lines to produce the colours; interference filters using layers of differing refractive indices.

Re:WOW!

[Rei]

[quote]Color has exactly one definition: the particular hue, not the intensity thereof. The color is determined by the color of the powdery scales.[/quote]

The article says nothing of the sort. In fact, it says just the opposite: "Blue light has a wavelength range from 400-480 nm, and is the only wavelength that is interfered with constructively by the slits of the morpho, which are 200 nm apart."

Your article completely undercuts your argument.