Which of the following is NOT a chromophore for lasers?

The correct choice is ozone, as it does not function as a chromophore for lasers. A chromophore is a molecule or part of a molecule that absorbs light at specific wavelengths, enabling the conversion of light energy into heat or other forms of energy.

Melanin, water, and hemoglobin are all well-known chromophores that absorb light energy effectively. Melanin absorbs a variety of light wavelengths, which is why lasers can target skin pigmentation. Water is a significant chromophore used in medical lasers, especially in procedures involving tissue, because it absorbs light across a broad spectrum, particularly in the infrared range. Hemoglobin is also a crucial chromophore, specifically in vascular laser treatments, as it absorbs light in the visible spectrum, particularly around the wavelengths used in dermatological applications to target blood vessels.

Ozone does absorb light but primarily in the ultraviolet range and doesn't serve the same function as the other listed chromophores in therapeutic or aesthetic laser treatments. Thus, it does not operate effectively as a chromophore in the context typically associated with laser applications, making it the appropriate answer.