What is the most important variable dictating how the laser beam will interact with the target tissue?

The variable that most significantly influences how a laser beam interacts with target tissue is its wavelength. The wavelength determines the absorption characteristics of the laser light by different tissues, which is crucial for effective laser therapy.

Different tissues absorb laser light at specific wavelengths, notably due to the presence of chromophores—molecules that absorb light. For example, certain wavelengths are absorbed more efficiently by melanin in hair or by hemoglobin in blood. This absorption leads to different interactions, such as photothermolysis, where the laser energy is converted to heat, effectively destroying targeted tissues. Hence, the selection of the proper wavelength is fundamental for achieving desired treatments and minimizes damage to surrounding tissues.

While factors like intensity, peak power, and duration also play roles in laser-tissue interaction, they are often secondary to the inherent absorption characteristics dictated by wavelength. Proper intensity, peak power, and duration are important for determining the effectiveness and safety of the treatment, but without the correct wavelength for tissue absorption, the interaction would be ineffective or even harmful.