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A weld can be created either as an individual spot or a seam weld.

The laser output that creates these welds can be achieved in one of two ways:

A pulsed laser produces a series of pulses, discrete packets of energy, at a certain pulse width and frequency until stopped. The “pulsed” descriptor refers to a laser that can produce a peak power that is greater than its average power.

A continuous wave (CW) laser produces extended output – the laser remains on continuously until stopped.

For example, a 25 W pulsed Nd:YAG laser can produce peak powers of up to 5 kW for a few milliseconds. This means it can produce a spot weld that would require a CW laser sized at 5 kW! With pulsed lasers a seam weld is created by a series of overlapping spot welds. For a continuous weld the laser remains on for the duration of the seam. A CW laser can also produce discrete pulses of laser light – known as gated or modulated output. In this case the CW laser peak power does not exceed the laser’s rated average power.

An Nd-YAG laser operates only in pulsed mode
 Diode lasers operate in continuous wave 
Fiber lasers can operate in both modes. 

Choosing when to use pulsed, continuous wave, or modulated output is determined by the specific application. Spot welding typically uses pulsed operation. For seam welding, the selection is made based on heat input and cycle time. For instance, when seam welding an implantable device, a pulsed laser is used to minimize heat input and maintain a uniform weld around a complex geometry with varying welding speeds. In contrast, for airbag initiators, welding at high speed using CW operation is