Half-Power Point

The value on either the leading or trailing edge of a laser pulse at which the power is one-half of its maximum value.

Heat Sink

A substance or device used to dissipate or absorb unwanted heat energy.

Helium-Neon Laser (HeNe)

A laser in which the active medium is a mixture of helium and neon. Its wavelength is usually in the visible range. Used widely for alignment, recording, printing, and measuring.

Hertz (Hz)

Unit of frequency in the International System of Units (SI), abbreviated Hz; replaces cps for cycles per second.


A photographic film or plate containing interference patterns created by the coherence of laser light. A three-dimensional image may be reconstructed from a hologram. There are transmission, reflection or integral holograms.