Nitrogen laser

Typically reported optimum values are in the range of 80 to 100 eV per Torr·cm pressure of nitrogen gas.

No vibration of the two nitrogen atoms is involved, because the atom-atom distance does not change with the electronic transition.

The metastable lower level lifetime is 40 μs, thus, the laser self-terminates, typically in less than 20 ns.

The Nd:YAG laser has an upper level lifetime of 230 μs, yet it also supports 100 ps pulses.

Nitrogen lasers can operate within a resonator cavity, but due to the typical gain of 2 every 20 mm they more often operate on superluminescence alone;[citation needed] though it is common to put a mirror at one end such that the output is emitted from the opposite end.

Thus this laser does not need a concave lens or refocusing lenses and beam quality improves along the gain medium.

Diffusion of electrons and elastic scattering at a buffer gas molecule spreads the avalanche perpendicular to the field.

[3] The electronics is a circuit composed of a spark gap, a capacitor, and the discharge through the nitrogen.

These capacitors are often constructed from a single layer of printed circuit board, or similar stack of copper foil and thin dielectric.

As the discharge is rapid, the inductor acts as an open circuit and so the voltage difference across the transverse spark gap (between the two capacitors) rises rapidly until the main spark gap discharges, firing the laser.

First, the inductance of all components is reduced by shortening and widening conductors and by squeezing the circuit into a flat rectangle.

The total inductance is the sum of the components: The intense discharge is reported to distort oscilloscopes nearby.

From this analysis it follows that: Paschen's law states that the length of the spark gap is inverse-proportional to the pressure.

To prevent sparks outside space ring in the low pressure the spacer usually gets thicker outwards in an s-shaped manner.

[7] Still the first spark gap in the cascade needs a free electron to start with, so jitter is rather high.

With a short duration (<10 ms) since the last laser pulse enough ions are left over so that all avalanches overlap also laterally.

Due to the low number of initial electrons streamers typically 1 mm apart are seen.

With about 11 ns the UV generation, ionisation, and electron capture are in a similar speed regime as the nitrogen laser pulse duration and thus as fast electric must be applied.

Helium due to its higher ionisation energy and lack of vibrational excitations increases the temperature to 2.2 eV.

The pulse energy ranges from 1 μJ to about 1 mJ; peak powers between 1 kW and 3 MW can be achieved.