Q-switched CO2 laser for material processing

A method of Q-switching a material processing CO2 laser having an electro-optically modulated crystal, the method comprising:

• generating a laser beam in a first state of polarization;
• maintaining zero voltage across the electro-optic crystal during a high optical loss interval of a Q-switching cycle;
• and
• maintaining a prescribed non-zero voltage across the electro-optic crystal during a low optical loss interval of the Q-switching cycle.

A method of Q-switching a CO2 laser for material processing, the laser having a gain medium and a cavity loss modulator, the method comprising:

• energizing the gain medium for a first prescribed time duration with a radio frequency pulse having a power equal to an integer multiple of a maximum average radio frequency power;
• and
• energizing the cavity loss modulator for a second prescribed time duration causing the laser cavity to switch from a high optical loss state to a low optical loss state generating thereby one or more laser pulses;
• wherein energizing the cavity loss modulator occurs after a third time duration of one to two population decay times of the upper laser level of the gain medium as measured from first energizing of the gain medium.

An electro-optic modulator comprising:

• first and second optical windows having a prescribed refractive index and receptive of the laser beam;
• an electro-optic crystal having a laser beam entrance surface and a laser beam exit surface;
• wherein the electro-optic crystal possesses a refractive index substantially equivalent to the refractive index of the first and second optical windows;
• wherein the electro-optic crystal is positioned between and in optical and thermal contact with the first and second optical windows at the laser beam entrance and exit surfaces creating thereby first and second optical interfaces;
• a first conductive electrode connected to the electro-optic crystal and to electrical ground;
• a second conductive electrode connected to the electro-optic crystal and to a voltage source creating thereby a voltage across the electro-optic crystal;
• and
• an Indium cushioning device for absorbing energy of the electro-optic crystal.

A method of truncating a portion of a laser pulse emitted by an electro-optically modulated Q-switched CO2 laser for material processing, the method comprising:

• detecting the laser pulse;
• converting the laser pulse into an electrical signal indicative of the laser pulse;
• comparing the electrical signal to an electrical bias signal;
• when the electrical signal indicative of the laser pulse is greater than the electrical bias signal, directing a timing device to terminate electro-optic modulation of the laser after a prescribed duration in time.

A method of truncating a portion of a laser pulse emitted by an electro-optically modulated Q-switched CO2 laser for material processing, the method comprising:

• detecting the laser pulse;
• converting the laser pulse into an electrical signal indicative of the laser pulse;
• delaying the converted signal by a prescribed duration in time, generating thereby a delayed signal;
• attenuating the converted signal by a prescribed value, generating thereby an attenuated signal;
• biasing the delayed signal with respect to the attenuated signal generating thereby a biased signal;
• comparing the biased signal with the attenuated signal;
• when the value of the biased signal equals the value of the attenuated signal directing a timing device to terminate electro-optic modulation of the laser after a prescribed duration in time.

A method of Q-switching an electro-optically modulated CO2 laser for material processing, the method comprising:

• during a high optical loss condition within the laser, energizing an electro-optic crystal within the laser until the electro-optic crystal is fully charged to a high voltage level;
• terminating energizing the electro-optic crystal;
• allowing gain to build up within the laser for the cavity build up time;
• during a low optical loss condition within the laser generating a laser pulse;
• deenergizing the electro-optical crystal after the laser pulse has been generated;
• and
• terminating deenergizing the electro-optical crystal.

A Q-switched CO2 laser system for material processing, the system comprising:

• defining an optical cavity;
• a gain medium positioned within the optical cavity for generating a laser beam;
• a cavity loss modulator for switching loss within the cavity from a high loss state to a low loss state or a low loss state to a high loss state , generating thereby one or more laser pulses;
• a pulsed signal generation system connected to the cavity loss modulator for delivering pulsed signals to the cavity loss modulator thereby controlling the state of optical loss within the optical cavity;
• a control unit connected to the pulsed signal generation system for controlling the pulsed signal generation system;
• and
• a pulse clipping circuit receptive of a portion of the laser beam and connected to the pulsed signal generation system for truncating a part of the laser pulses.

A CO2 laser system for material processing, the system comprising:

• a folded waveguide laser having a plurality of wavelength selective mirrors defining an optical cavity;
• a gain medium positioned within the optical cavity for generating a laser beam;
• a cavity loss modulator for switching loss within the cavity from a high loss state to a low loss state or a low loss state to a high loss state , generating thereby one or more laser pulses;
• a pulsed signal generation system connected to the cavity loss modulator for delivering pulsed signals to the cavity loss modulator thereby controlling the state of optical loss within the optical cavity;
• and
• a control unit connected to the pulsed signal generation system for controlling the pulsed signal generation system.