FRP-Nd:YAG has as it target chromphores dark pigments (molecules or granules) including melanin.  So anything colored black, dark grey, dark green, deep red, etc.

I can take the black ink off a business card and not effect the card.  Blue ink takes a little longer and more energy.  I can also take the black ink off the wrapper of an anesthetic carpule through the opposite side of the carpule and through the water in the carpule…..instantaneously.

Also black pigmented gram negative anaerobes like P. Gingivalis, Intermedius and Forsythus.  To a very significant extent, de-oxygenated hemoglobim which is very dark, and to a moderate effect, oxygenated hemoglobin.

Argon is best absorbed in oxygenated hemoglobin (i.e. bright red–the complimentary wavelength if 515nm green)

Bob

Quote: from dkimmel on 9:15 pm on Feb. 22, 2005
Ok , I am confused. My understanding is the Nd:YAG is better at hemostasis then the diodes which are at a shorter wavelength. Which is the opposite of what I would expect??
Help?

Someone studying for their lecture and ALD exam,maybe?? Remember the answer is always -laser safety officer!

If I remember correctly (and I hope Bob corrects this if I am incorrect), wavelength influences coagulation via a relationship between the wavelength and size of the blood vessel. The shorter wavelengths will coagulate smaller vessels better but the downside is that they don’t penetrate very far. Since the tissue is a high percentage H2O, the ndYAG will penetrate further. The longer wavelength ndYAG  will close over a larger vessel. Then you add in the difference in pulsewidths, gated vs. free running …

Hi Guys,

I’m re-reading the original question and have some different thoughts.

The term “color” and “chromaphore” in the context of lasers and photonics shouldn’t be taken literally or only in our human limited dimension of visual acuity: blue to red.

Remember with lasers and photonics we are talking about the electromagnetic spectrum–from invisible ionizing wavelengths or “colors”, to the visible non-ionizing/non-thermal wavelengths or colors in the literal sense as we understand them because we can see them, to the invisible thermal wavelengths or “colors”.

That is at least one test question on ALD’s written exam.

The molecular bond is not the absorbing material with erbiums, it is the water molecule. Since the combined wavelengths of white light (blue through red) are all absorbed into the color of black, we have a simple way to refer to absorption by invisible light.

So wavelengths that are highly absorbed in water can be understood to be “black” to that wavelength. Threfore, one way to think about erbims is that water is “black” to erbium–i.e. highly or completely absorbed. Consequently, the “color” or “chromaphore” of erbium absorption is water.

As far as diodes (810nm for example) versus Nd:YAG (1064nm) goes, they are both well in the near-infrared spectrum being only 254nm apart.

So, you have to enter into the equation pulse duration which governs energy density (aka intensity).

Wavelength is critical, but temporal emission mode controls the rate, rapidity, and quality as well as the dimensionality of similar wavelengths absorbed in similar colors.

Does that make more sense?

Bob