Gain is the internal multiplication process of the detector. It is a dimensionless multiplier of the photogenerated signal. In APD's it's usually in the 100s and in PMTs 1,000,000s.

Gain bandwidth product (GB product)

This is the product of the gain and bandwidth, and is used as a measure for indicating characteristics of an amplifier element.

Gate function

Gating is the process of quickly shutting the input of a detector off and turning it on again. It can be thought of as an electronic shutter.

Gate function operation

Gating in detectors usually involves disrupting the flow of electrons, by applying a voltage that is more negative than the electron source, thereby repelling the signal electrons and shutting the detector off.

Geiger discharge

When an APD is operated at a reverse voltage higher than the breakdown voltage, even very low incident light causes a discharge in the APD due to the high electrical field. This phenomenon is called Geiger discharge.

Geiger mode

Operation mode in which an APD is operated at a reverse voltage higher than the breakdown voltage. Geiger mode operation makes it possible to detect single photons.

Group delay characteristic

This is a characteristic that indicates the time delay of the output waveform versus an input waveform. This can be obtained by differentiating the phase characteristic with respect to the frequency. If the phase characteristic is linear, then the group delay becomes a constant value, allowing signal transmission without any distortion.

Guaranteed life - Lamp

Ends when drift or fluctuation exceeds stated specifications. Is shorter than the average or typical life of a lamp. Life-end is defined as the time when the radiant intensity falls to 50% of its initial value or when the output fluctuation exceeds the device's specification.

Using a lamp with a longer life leads to the reduction of maintenance cost as well as time and running cost of equipment. Due to unique electrode structures with minimum electrode wear, Hamamatsu lamps feature unprecedented high stability over extended periods of operating time.