Because visible transitions have somewhat lower gain, these lasers generally have lower output efficiencies and are more costly. The 3.39 μm transition has a very high gain, but is prevented from use in an ordinary He-Ne laser (of a different intended wavelength) because the cavity and mirrors are lossy at that wavelength. However, in high-power He-Ne lasers having a particularly long cavity, superluminescence at 3.39 μm can become a nuisance, robbing power from the stimulated emission medium, often requiring additional suppression.