Micromachining with high-energy, intra-cavity Q-switched CO2 laser pulses

In a CO2 laser system having a resonator cavity that includes a gas gain medium that in response to pumping energy supplied by a pumping source produces stimulated emission energy, a method for laser micromachining, comprising:

• supplying pumping energy, from the pumping source at a pumping start time and throughout a pumping span, to the gas gain medium within the resonator cavity;
• generating from the resonator cavity a laser output of a burst of at least two laser pulses, including a first laser pulse, of stimulated emission energy from the resonator cavity at a pulse repetition frequency that is greater than 10 kHz during the pumping span, wherein the resonator cavity includes an electro-optical modulator that in response to an applied switching signal causes at least first and second states corresponding to respective low and high values of optical gain in the resonator cavity and influences multiple waveform characteristics of each laser pulse, wherein changing the applied switching signal from the first state to the second state at a pulse extraction start time causes extraction of each laser pulse and changing the applied signal from the second state to the first state at a pulse termination time causes termination of each laser pulse, wherein each laser pulse has a pulsewidth that includes a time interval between the pulse extraction time and the pulse termination time, wherein each laser pulse is characterized by a spike having a peak instantaneous power followed by a tail having a range of tail instantaneous powers above a nonzero value, and wherein the spike has a spike duration and the tail has a tail duration that is substantially greater than the spike duration, whereby selecting the tail duration time by changing the applied signal from the second state to the first state determines the energy delivered by the laser pulses;
• and
• directing the burst of the laser pulses to remove target material at a target area.

In a CO2 laser system having a resonator cavity that includes a gas gain medium that in response to pumping energy supplied by a pumping source produces stimulated emission energy, a method for laser micromachining, comprising:

• supplying pumping energy, from the pumping source at a pumping start time and throughout a pumping span, to the gas gain medium within the resonator cavity;
• generating from the resonator cavity a laser output of a burst of at least two laser pulses, including a first laser pulse, of stimulated emission energy from the resonator cavity at a pulse repetition frequency that is greater than 10 kHz during the pumping span, wherein the resonator cavity includes an electro-optical modulator that in response to an applied switching signal causes at least first and second states corresponding to respective low and high values of optical gain in the resonator cavity and influences multiple waveform characteristics of each laser pulse, wherein changing the applied switching signal from the first state to the second state at a pulse extraction start time causes extraction of each laser pulse and changing the applied signal from the second state to the first state at a pulse termination time causes termination of each laser pulse, wherein each laser pulse is characterized by a spike having a peak instantaneous power, wherein an amount of delay is introduced between the pumping start time and the pulse extraction time of the first laser pulse, and wherein the peak instantaneous power of the spike of at least the first laser pulse has a level that is impacted by the amount of the delay;
• and
• directing the burst of the laser pulses to remove target material at a target area.

In a CO2 laser in which a resonator cavity characterized by an optical gain includes a gas gain medium and a Q-switch, the gas gain medium in response to pumping energy supplied by a pumping source producing stimulated emission energy, and the Q-switch in response to an applied switching signal controlling the optical gain of the resonator cavity and thereby controlling extraction of a pulse of stimulated emission energy from the resonator cavity, the pulse of the stimulated emission energy having multiple waveform characteristics, a method of controlling one or more of the waveform characteristics, comprising:

• applying in sequence the pumping energy to produce stimulated emission energy and the switching signal to extract a pulse of the stimulated emission energy, the application of the pumping energy corresponding to a pumping start time and the application of the switching signal corresponding to a pulse extraction start time;
• and
• introducing between the pumping start time and the pulse extraction start time a delay of an amount that causes production of stimulated emission energy in the gas gain medium to a level that causes, upon occurrence of the pulse extraction start time, extraction of the pulse of stimulated emission energy characterized by an increase to a maximum peak power amplitude and a subsequent decrease to a range of local maximum tail power amplitudes of nonzero values, each of the maximum peak and the range of local maximum tail power amplitudes having a duration, and the duration of the maximum peak power amplitude being substantially less than the duration of the range of local maximum tail power amplitudes.