Page 43 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
 Shorter wavelengths = blue colour Longer wavelengths = red colour
Figure 22: The visible spectrum – to human eyes
● The importance of wavelength in medical/cosmetic treatments cannot be overstated. By selecting the ‘correct’ wavelength we can target specific tissues like melanin or blood or collagen. These tissues contain ‘chromophores’ (see explanation box below). It is these chromophores which determine how the tissues react to the incoming light energy. Watch this short video.
Fundamental Wavelengths
● The “fundamental” wavelength is the wavelength generated by the laser medium and the physical properties of the laser cavity – it is ‘fixed’ or ‘unchangeable’. This wavelength is determined by the intrinsic properties of the laser design. For example, Nd:YAG lasers typically emit a wavelength of 1064 nm, while ruby lasers generate a 694 nm beam.
Harmonics
● In some laser systems, the laser photons can be ‘forced’ to ‘combine’ using special materials, which results in a single new photon which has twice the frequency of the original photons. This means that the original wavelength is halved. So, if the original photons have a wavelength of 800 nm, then the new, “1st harmonic” photons will have a wavelength of 400 nm.
● Some lasers can generate ‘harmonic’ wavelengths using these special ‘non-linear’ materials. As an example, the Q-switched Nd:YAG laser can generate a range of harmonic outputs including 1320 and 1440 nm. Using a KTP (potassium titanyl phosphate) crystal a new wavelength of 532 nm can also be generated using an Nd:YAG as the ‘driver’. This is common practice in the removal of tattoos, with this laser.
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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