US 6,193,711 B1Granted

Rapid pulsed Er:YAG laser

AssigneeCoherent, Inc.

InventorsKevin Connors, Greg Spooner, Ralph Saunders

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Abstract

An Er:YAG laser system has a resonant cavity including an Er:YAG rod pulse-pumped by a pulsed flashlamp. The pump-pulse repetition rate and average power is selected to provide a known essentially constant thermal-lensing power in the Er:YAG rod. Design parameters of the Er:YAG rod and the resonant cavity are selected to compensate for this thermal-lensing power. A shutter in the resonant cavity, when closed or open, respectively prevents or allows a laser output-pulse to be generated in response to a pump-pulse. Laser output-pulse duration is continuously variable and is controlled by controlling the duration of flashlamp-pulses. A sequence of laser output-pulses is controlled by opening and closing the shutter. This arrangement has the advantage that the laser output-pulse repetition rate can be selected to be the flashlamp-pulse repetition rate or some sub-multiple thereof while maintaining thermal-lensing power in the rod essentially constant and compensated for.

Claims24

Dependent claims

A Er:YAG laser system for treating biological tissue, comprising:

an Er:YAG gain-medium located in a resonant cavity;
an optical pump for providing exciting-pulses in variable sequences thereof during an operational period of the laser system, one of said exciting-pulses in each said sequence each having sufficient energy to excite said gain-medium to a level sufficient to generate a laser output-pulse having sufficient energy to cause ablation of the biological tissue, all other exciting-pulses generation laser output-pulses having insufficient energy to cause ablation of said biological tissue but sufficient energy to cause heating of the biological tissue;
a power supply for providing current-pulses for repetitively energizing said optical pump, each of said current-pulses providing a said exciting-pulse;
a controller for controlling said power supply, said controller arranged such that during said operational period, energy-per-pulse in said ablation-causing laser output-pulse is actively maintained by said controller at a predetermined value by adjusting energy in a corresponding one of said exciting-pulses and responsive to said energy adjustment of said corresponding one of said exciting pulses one or both of energy and frequency of said all other exciting-pulses is correspondingly adjusted such that collectively all of said exciting-pulses cause an essentially constant predetermined, non-zero thermal-lensing effect in said gain-medium;
and
wherein design parameters of said resonant cavity and gain-medium are selected to compensate for said predetermined thermal-lensing effect in said gain-medium.

3 more elements

A Er:YAG laser system for treating biological tissue, comprising:

an Er:YAG gain-medium located in a resonant cavity;
an optical pump for providing exciting-pulses for exciting said gain-medium;
a power supply for providing current-pulses for repetitively energizing said optical pump, each of said current-pulses providing a said exciting-pulse;
a controller arranged for controlling said power supply such that exciting-pulses are provided in variable sequences of more than one thereof during an operational period of the laser system, at least one said sequence of exciting-pulses in said sequences thereof having sufficient energy to excite said gain-medium to a level sufficient to generate a laser output-pulse;
a shutter located in said resonant cavity, said shutter, in closed and open modes thereof, for respectively preventing and allowing generation of a laser output-pulse in response to a said exciting-pulse having said sufficient energy;
said controller arranged for controlling said shutter cooperative with said power supply such that at least one of said plurality of exciting-pulses having sufficient energy to do so is allowed to generate a laser-output-pulse, and at least one of said exciting-pulses is prevented from generating a laser-output-pulse;
and
said controller arranged such that during said operational period, energy-per-pulse in at least one of said allowed laser output-pulses is actively maintained by said controller at a predetermined value by adjusting the energy in a corresponding said exciting-pulse and, by adjusting one or both of the repetition frequency or energy in all other said exciting pulses responsive to said energy adjustment of said corresponding said exciting-pulse provides that said exciting-pulses collectively cause an essentially constant predetermined, non-zero thermal-lensing effect in said gain-medium;
and
wherein design parameters of said resonant cavity and gain-medium being selected to compensate for said predetermined thermal-lensing effect in said gain-medium.

7 more elements

Dependencies are inferred from the claim text.