Pumping is the method used to lift atoms from a lower level to an upper level. In laser machining, diode pumped laser is becoming more and more significant.
Typically, pumping takes the following forms:
Optical Pumping comes first. OEM laser system design & development of pulsed light created by a strong lamp or laser beam is used in optical pumping. Light from potent incoherent sources can be used to create optical pumping. The active medium absorbs the incoherent light, pumping the atoms up to the highest laser level. This technique is best suited for solid state or liquid lasers with broad enough absorption bands to efficiently absorb energy from incident-wide band incoherent light sources.
Being a resonant process, optical pumping requires that the incident photon energy, be equal to the energy differences between the excited states and the ground state. Lasers that utilise gas or semiconductor materials employ electrical pumping. It is accomplished by allowing a current to pass through a conductive media, such as an ionized gas or semiconductor, whether it be a constant dc current, radio frequency of current, or pulsed current. Electrical pumping is typically carried out using an electrical discharge with adequate intensity. Due to the narrower absorption bands of gas lasers compared to solid and liquid lasers, wide-band lamp light is insufficient for gas lasers, and a large portion of the lamp's energy is lost as heat. Electron impact excitation results in electrical pumping, which is non-resonant pumping.
For chemical pumping, an exothermic chemical reaction immediately causes population inversion. Chemical pumping typically involves the use of gaseous gases that are extremely reactive and frequently explosive. Exothermic reactions typically produce huge amounts of energy; high-power and high energy laser pulses can be obtained by converting a significant portion of this available energy into laser energy.
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