Page 122 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Phase Photon
Photo- Mechanical Effect
Photo-Acoustic Effect
Photo-thermal Effect
Photo-Ablation
Picosecond Porphyria
Power
Pulse Duration
Pulsed Laser
Waves are in phase with each other when all the troughs and peaks coincide and are "locked" together. The result is a reinforced wave in increased amplitude (brightness).
In quantum theory, the elemental unit of light, having both wave and particle behaviour. It has motion, but no mass or charge. The photon energy (E) is proportional to the electromagnetic wave frequency (ν) by the relationship: E=hν; where h is Planck's constant (6.63 x10-34 Joule-sec).
The photo-mechanical effect is created when a very high temperature is generated but which is not sustainable, as in tissues. The energy within the heat is converted into a pressure wave which propagates through the tissue at the speed of sound. Anything brittle in its path will experience a shear force causing it to rupture – as in tattoo ink. Non-brittle elements within the skin will merely vibrate under such a force.
An alternative name for the Photo-Mechanical Effect, above.
This occurs when an object absorbs light energy and generates heat. Many everyday objects do this naturally from sunlight falling on them. Lasers with pulsewidths in the micro to millisecond ranges can easily induce the photothermal effects in tissues.
When the heated tissues reach a certain temperature (typically around 100°C) the local tissue water will reach boiling point. At this point the water will begin to turn onto steam and cause an ablative process within the tissue cells. This results in those cells ‘flying off’ the tissue.
One picosecond is 10-12 seconds or 0.000000000001s. Some modern-day aesthetic/medical lasers output energy pulses in the range 350 to 900 ps.
Also known as ‘photo-sensitivity’ – some people have skin which reacts adversely to intense light. All potential clients should be asked if they are aware of such a condition as they will not respond well to this treatment.
The amount of light emitted by a laser handpiece over time is measured as power. The ‘peak power’ is the maximum power emitted during this pulse. See more here...
The pulse duration is simply the length of the pulse of light (measured in milliseconds or nanoseconds in many aesthetic/medical systems). It is also called the pulsewidth or pulse length. See more here...
Laser which delivers energy in the form of a single or train of pulses.
Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
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