Method and system for confined laser drilling

1. A method for drilling a hole through a near wall of a component, the method comprising:

directing a confined laser beam of a confined laser drill through a collimator and towards the near wall of the component, the collimator being disposed along the confined laser beam, and wherein the collimator includes a chamber that receives the confined laser beam along with a fluid and a nozzle that directs the laser beam inside a liquid column of the fluid towards the near wall of the component;

sensing a first characteristic of light from the hole in the near wall of the component with a first sensor positioned outside the component while directing the confined laser beam towards the near wall of the component, wherein the first sensor is offset from the confined laser beam and senses a characteristic of reflected light along the confined laser beam by redirecting at least a portion of the reflected light directed to the first sensor with a redirection lens, and wherein the redirection lens is positioned within the chamber and intersects a beam axis along which the confined laser beam extends;

sensing a second characteristic of light from the hole in the near wall of the component with a second sensor, the second characteristic of light being different from the first characteristic of light; and

determining a hole progress based on the sensed first characteristic of light and the sensed second characteristic of light;

wherein the first characteristic of light is an intensity of light at a first wavelength, the first wavelength indicative of the confined laser beam hitting a first layer of the near wall of the component;

wherein the second characteristic of light is an intensity of light at a second wavelength, the second wavelength indicative of the confined laser beam hitting a second layer of the near wall of the component;

wherein determining the hole progress based on the sensed first characteristic of light and the sensed second characteristic of light comprises comparing the intensity of light sensed at the first wavelength to the intensity of light sensed at the second wavelength.

2. The method of claim 1 , wherein the component is an airfoil of a gas turbine.

3. The method of claim 1 , wherein the first layer is a thermal barrier coating, and wherein the second layer is a metal portion.

4. The method of claim 1 , wherein determining the hole progress based on the sensed first characteristic of light and the sensed second characteristic of light further comprises determining the hole is at least a predetermined amount through the first layer of the near wall of the component based at least in part on the comparison of the intensity of light sensed at the first wavelength to the intensity of light sensed at the second wavelength.

5. The method of claim 4 , further comprising

adjusting one or more operating parameters of the confined laser drill in response to determining the hole is at least a predetermined amount through the first layer of the near wall of the component.

6. The method of claim 1 , wherein the first sensor is an optical sensor, and wherein the method further comprises

determining one or both of a reflected pulse length of the confined laser drill and a reflected pulse rate of the confined laser drill.

7. The method of claim 6 , further comprising

determining a depth of the hole being drilled by the confined laser drill based on one or both of the determined reflected pulse length of the confined laser drill and the determined reflected pulse frequency of the confined laser drill.

8. A method for drilling a hole through a near wall of a component, the method comprising:

directing a confined laser beam of a confined laser drill through a collimator and towards the near wall of the component, the collimator being disposed along the confined laser beam, and wherein the collimator includes a chamber that receives the confined laser beam along with a fluid and a nozzle that directs the laser beam inside a liquid column of the fluid towards the near wall of the component;

sensing a first characteristic of light from the hole in the near wall of the component with a first sensor positioned outside the component and directed away from the near wall of the component, wherein the first sensor is offset from the confined laser beam and senses a characteristic of reflected light along the confined laser beam by redirecting at least a portion of the reflected light directed to the first sensor with a redirection lens, wherein the redirection lens is positioned within the chamber and intersects a beam axis along which the confined laser beam extends, wherein the first characteristic of light is sensed while directing the confined laser beam towards the near wall of the component, and wherein the first characteristic of light is an intensity of light at a first wavelength, the first wavelength indicative of the confined laser beam hitting a first layer of the near wall of the component;

sensing a second characteristic of light from the hole in the near wall of the component with a second sensor directed towards the hole, the second characteristic of light being different from the first characteristic of light, wherein the second characteristic of light is an intensity of light at a second wavelength, the second wavelength indicative of the confined laser beam hitting a second layer of the near wall of the component; and

determining a hole progress based on the sensed first characteristic of light and the sensed second characteristic of light, wherein determining the hole progress based on the sensed first characteristic of light and the sensed second characteristic of light comprises comparing the intensity of light sensed at the first wavelength to the intensity of light sensed at the second wavelength.

9. The method of claim 8 , wherein determining the hole progress based on the sensed first characteristic of light and the sensed second characteristic of light further comprises determining the hole is at least a predetermined amount through the first layer of the near wall of the component based at least in part on the comparison of the intensity of light sensed at the first wavelength to the intensity of light sensed at the second wavelength.

10. The method of claim 9 , further comprising

adjusting one or more operating parameters of the confined laser drill in response to determining the hole is at least a predetermined amount through the first layer of the near wall of the component.

11. The method of claim 8 , wherein the second sensor defines a line of sight extending in a direction nonparallel to the confined laser beam.