In lasers however, this doesn't apply and lasers with higher wavelength such as Er.Yag cut hard tissue better than lasers with lower wavelength such as diode for example.Why?
The energy of a single photon is dependent on the laser wavelength. And since the wavelength of a laser can be controlled very precisely this can be used in many applications as for example laser spectroscopy.
When processing materials the effects of the energy of the photon is relevant for the type of the breakdown process. Short wavelength photons (UV) can directly dissociate molecules while longer wavelength mainly heat the substrate.
The wavelengths you have been talking about are both heating a material until thermal breakdown. Here a wavelength around 1000nm may be less effective as the processed material could be transparent or opaque for the used laser radiation. This distributes the heat load over a larger volume leading to higher power requirement.
In contrast, when processing metals the absorption usually increases with a shorter wavelength leading to a higher efficiency and stability.
The wavelengths you have been talking about are both heating a material to reach the saturation of the material to make the electron in the state absorption the wave length and this wavelength must equal to the energy band gab
As already mentioned by Karsten and Ruaa, the choice of the optimal laser wavelength depends on the optical properties of the processed material and the kind of application.
However for laser cutting purposes the power is brought up by the photon flux (i.e. the number of photons per area and time) and is only by a very small amout tunable by the energy per photon ( i.e. the wavelength).
So here gas lasers, solid state lasers and fiber laser have a great advantage over laser diodes with respect to photon flux.
It is true that higher wavelength photon has less energy. But for cutting the materials you need a high power laser. High power lasers have large number of photon flux. They may be having higher wavelength (low energy photons) with higher photon flux. For example Co2 laser, doped glass lasers and fiber lasers provide high power useful in cutting different type of materials depending on their properties. However diode lasers have small photon flux which is useful for various other application than cutting.
It is just the matter of the type of target material and absorption of the laser light with that target material.
For instance, I found out it can be absorbed well by hydroxyapatite too, then makes it suitable for cutting bones as well as soft tissues.
This means you may use a UV laser but if the absorption region of the target material does not overlap with the wavelength of the laser, the UV laser is not effective in spite of the fact that has a higher photon energy compared to the laser you mentioned.
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