H

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 (HeNe) laser

The most widely-used gas laser. Available in a variety of wavelengths from the green to the red to the infrared, the most common wavelength being 633 nm (red). Emits highly monochromatic radiation.

Hertz (Hz)

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

Hologram

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.