Zig-zag laser with improved liquid cooling

• US 7,433,376 B1
• Filed: 08/07/2006
• Issued: 10/07/2008
• Est. Priority Date: 08/07/2006
• Status: Active Grant

• Current Assignee: Textron Systems Corporation (Textron Inc)
• Original Assignee: Textron Systems Corporation (Textron Inc)
• Inventors: Klimek, Daniel E., Mandl, Alexander E., Hayes, Richard
• Primary Examiner(s): Donovan; Lincoln
• Assistant Examiner(s): Paul; Antony M.
• Application Number:
  US11/500,269
• Time in Patent Office: 792 Days
• Field of Search: 372/45.01, 372/70, 372/35, 372/34, 372/40, 372/41, 165/80.4, 398/141
• US Class Current: 372/35
• CPC Class Codes: H01S 3/025 of solid state lasers, e.g. housings or mountings
• CPC Class Codes: H01S 3/0407 Liquid cooling, e.g. by water
• CPC Class Codes: H01S 3/042 for solid state lasers H01S3/0401 takes precedence
• CPC Class Codes: H01S 3/0606 with polygonal cross-section, e.g. slab, prism H01S3/0604 takes precedence
• CPC Class Codes: H01S 3/08095 Zig-zag travelling beam through the active medium
• CPC Class Codes: H01S 3/1611 neodymium
• CPC Class Codes: H01S 3/1643 YAG

Abstract

A zig-zag laser has the ability to generate a high power beam while effectively removing heat without degrading the beam quality. The laser has a series of gaps interposed between the thin slabs, the gain medium, and between the thin slabs and the quartz windows to receive coolant and cool the cell assembly. The coolant flows transversely relative to the path of the laser and the flow of the coolant is in the opposite direction on each side of the thin slab to minimize the temperature gradient. The gaps in conjunction with the inner channel portions in the secondary manifold flow the coolant through the cell assembly in a laminar manner therein not degrading the laser beam quality. A transparent quartz/quartz interface between the secondary manifold and the cell assembly allow the fluorescence to move away from the cell assembly and minimizes heat in the cell assembly.

Claims

1. A zig-zag laser head comprising:

a cell assembly including;

a plurality of thin slabs for lasing, each of the thin slabs having a thickness in a lateral direction, a height in a transverse direction, and a length in longitudinal direction, the thin slabs extending longitudinally and parallel to each other in the transverse and longitudinal directions, the thin slabs defining a gap between adjacent slabs;

a pair of windows extending longitudinally and positioned so that the plurality of thin slabs are interposed between the windows; and

the thin slabs and the windows defining a gap between the window and the adjacent thin slab;

a pair of manifolds, the manifold positioned such that the thin slabs and the windows are interposed between the manifolds in the transverse direction, the manifolds having an elongated flow passageway; and

the elongated flow passageway of the manifolds and the gaps in the cell assembly defining a flow path for a coolant fluid to travel in the transverse direction in the cell assembly;

wherein the windows of the cell assembly have an interface window surface and the laser further comprising a pump source and an optical scrambler for coupling with the interface window surface for introducing energy into the cell assembly;

further comprising a heat exchanger and wherein the manifolds of the laser head are connected to a series of lines delivering and removing coolant fluid such that the coolant fluid flows in opposite transverse directions in adjacent gaps in the cell assembly

wherein;

the pair of manifolds comprises a primary manifold having a plurality of primary manifold headers and a secondary manifold having a plurality of secondary manifold headers, the primary manifold opposing the secondary manifold, the thin slabs and the quartz windows substrates being disposed between the primary manifold and the secondary manifold along the transverse direction;

a first manifold header of the plurality of primary manifold headers being configured to direct fluid along a first direction toward a first manifold header of the plurality of secondary manifold headers, along a first face of a thin slab, and within a first gap relative to the thin slab; and

a second manifold header of the plurality of secondary manifold headers being configured to direct fluid along a second direction, the second direction opposing the first direction, toward a second manifold header of the plurality of primary manifold headers, along a second face of the thin slab, the second face opposing the first face, and within a second gap relative to the thin slab, the second gap opposing the first gap.

2. A zig-zag laser head of claim 1 wherein

each of the windows are composed of quartz;

each of the manifolds comprises a primary manifold, a secondary manifold, and a plurality of headers wherein

each of the secondary manifolds formed of a quartz material and having a channel for each of the gaps as part of the elongated flow passageway, the secondary manifolds positioned such that the thin slabs and the quartz windows substrates are interposed between the secondary manifolds in the transverse direction;

each of the primary manifolds engaging the respective secondary manifold, each of the primary manifolds having a cavity and a passage for each of the channels in the secondary manifolds as part of the elongated flow passageway of the manifolds; and

each of the headers having a plenum for moving the coolant towards and away from the manifolds; and

wherein the quartz/quartz interface of the secondary manifold and the quartz windows allow light to pass from the cell assembly to the secondary manifold therein moving the fluorescence away from the cell assembly and minimizing heat in the cell assembly.

3. A zig-zag laser head of claim 2 wherein the channel has an outer channel portion and an inner channel portion that narrow down in tapered manner to maintain a laminar flow of the coolant flow.

4. A zig-zag laser head of claim 2 wherein the quartz windows and the thin slabs having a rounded edge to create controlled entrance condition to reduce flow instability and promote a laminar flow of the coolant fluid.

5. A zig-zag laser head of claim 2 wherein each of the thin slabs having at least one longitudinal groove on each of its lateral edges and each of the secondary manifolds having a plurality of corresponding longitudinal grooves on a edge for engaging the grooves in the slabs, and further comprising an expanded PTFE (expanded polytetrafluoroethylene) interface seal having a series of slots, the expanded PTFE interface seal interposed between the secondary manifold and the quartz window and the thin slabs and interacting with the grooves for holding the thin slabs parallel to each other and forming a seal.

6. A zig-zag laser head of claim 2 further comprising a plurality of perforated plates, each plate having a plurality of perforations for passage of coolant therein removing the longitudinal flow component of the fluid.

7. A zig-zag laser head of claim 6 wherein the channel has an outer channel portion and an inner channel portion that narrow down in a tapered manner to maintain a laminar flow of the coolant flow and wherein the quartz windows and the thin slabs have rounded edges to promote a laminar flow of the coolant fluid.

8. A zig-zag laser head of claim 7 further comprising

a plurality of end spacer blocks extending in the transverse direction and located at the longitudinal ends of the thin slabs, the end spacer blocks interposed between the quartz windows, one of the end spacer blocks located at each end of the thin slab such that an end spacer block, the thin slab, and another end spacer block extend along a longitudinal plane;

and

a plurality of non absorbing channel spacers interposed between the thin slabs at the edges of the slabs in proximity to the end spacer blocks and between the thin slabs and the quartz substrates to define the gap between the thin slabs and the gap between the thin slabs and the quartz windows.

9. A zig-zag laser head of claim 8 wherein each of the thin slabs has at least one groove on each of its lateral edges and each of the secondary manifolds has a plurality of grooves on a edge engaging the slabs, and further comprising an expanded PTFE (expanded polyetrafluoroethylene) interface seal having a series of slots, the expanded PTFE interface seal interposed between the secondary manifold and the quartz window and the thin slabs and interacting with the grooves for holding the thin slabs parallel to each other and forming a seal.

10. A zig-zag laser comprising:

a pair of pump sources;

a pair of optical scramblers, one of the optical scramblers coupled to each pump source;

a laser head comprising;

a cell assembly including;

a plurality of thin slabs for lasing, each of the thin slabs having a thickness in a lateral direction, a height in a transverse direction, and a length in longitudinal direction, the thin slabs extending longitudinally and parallel to each other in the transverse and longitudinal directions, the thin slabs defining a gap between adjacent slabs;

a pair of windows extending longitudinally and positioned so that the plurality of thin slabs are interposed between the windows, each of the windows having a window for interfacing with the optical scrambler for introducing energy into the cell assembly; and

the thin slabs and the windows defining a gap between the window and the adjacent thin slab;

a pair of manifolds, the manifolds positioned such that the thin slabs and the windows are interposed between the manifolds in the transverse direction, the manifolds having an elongated flow passageway; and

the elongated flow passageway of the manifolds and the gaps in the cell assembly defining a flow path for a coolant fluid to travel in the transverse direction in the cell assembly; and

a heat exchanger, wherein the manifolds of the laser head are connected to a series of lines delivering and removing coolant fluid such that the coolant fluid flows in opposite transverse directions in adjacent gaps in the cell assembly

wherein;

the pair of manifolds comprises a primary manifold having a plurality of primary manifold headers and a secondary manifold having a plurality of secondary manifold headers, the primary manifold opposing the secondary manifold, the thin slabs and the quartz windows substrates being disposed between the primary manifold and the secondary manifold along the transverse direction;

a first manifold header of the plurality of primary manifold headers being configured to direct fluid along a first direction toward a first manifold header of the plurality of secondary manifold headers, along a first face of a thin slab, and within a first gap relative to the thin slab; and

a second manifold header of the plurality of secondary manifold headers being configured to direct fluid along a second direction, the second direction opposing the first direction, toward a second manifold header of the plurality of primary manifold headers, along a second face of the thin slab, the second face opposing the first face, and within a second gap relative to the thin slab, the second gap opposing the first gap.

11. A zig-zag laser of claim 10 wherein each of the windows is composed of quartz;

each of the manifolds comprises a primary manifold, a secondary manifold, and a plurality of headers wherein

each of the secondary manifolds formed of a quartz material and having an inner channel portion for each of the gaps as part of the elongated flow passageway, the inner channel portion narrowing from an outer channel portion reducing the cross sectional area in the flow passageway as the passageway approaches the cell assembly providing a smooth flow transition, the secondary manifolds positioned such that the thin slabs and the quartz windows are interposed between the secondary manifolds in the transverse direction;

each of the primary manifolds engaging the respective secondary manifold, each of the primary manifolds having a cavity and a passage for each of the outer channel portions in the secondary manifolds as part of the elongated flow passageway of the manifolds; and

each of the headers having a plenum for moving the coolant towards and away from the manifolds; and

wherein the quartz/quartz interface of the secondary manifold and the quartz windows allows light to pass from the cell assembly to the secondary manifold therein moving the fluorescence point away from the cell assembly and minimizing heat in the cell assembly.

12. A zig-zag laser head comprising:

a cell assembly including;

at least one thin slab for lasing, the thin slab having a thickness in a lateral direction, a height in a transverse direction, and a length in a longitudinal direction, the thin slab extending longitudinally;

a pair of windows extending longitudinally and positioned so that the at least one thin slab is interposed between the windows, each of the quartz windows having a window for interfacing with the optical scrambler for introducing energy into the cell assembly; and

the thin slabs and the windows defining a gap between the window and the adjacent thin slab;

a pair of manifolds, the manifold positioned such that the thin slabs and the windows are interposed between the manifolds in the transverse direction, the manifolds having an elongated flow passageway; and

the elongated flow passageway of the manifolds and the gaps in the cell assembly defining a flow path for a coolant fluid to travel in the transverse direction in the cell assembly;

wherein the manifolds of the laser head are connected to a series of lines delivering and removing coolant fluid such that the coolant fluid flows in opposite transverse directions in adjacent gaps in the cell assembly

wherein;

the pair of manifolds comprises a primary manifold having a plurality of primary manifold headers and a secondary manifold having a plurality of secondary manifold headers, the primary manifold opposing the secondary manifold, the thin slabs and the quartz windows substrates being disposed between the primary manifold and the secondary manifold along the transverse direction;

a first manifold header of the plurality of primary manifold headers being configured to direct fluid along a first direction toward a first manifold header of the plurality of secondary manifold headers, along a first face of a thin slab, and within a first gap relative to the thin slab; and

a second manifold header of the plurality of secondary manifold headers being configured to direct fluid along a second direction, the second direction opposing the first direction, toward a second manifold header of the plurality of primary manifold headers, along a second face of the thin slab, the second face opposing the first face, and within a second gap relative to the thin slab, the second gap opposing the first gap.

13. A zig-zag laser head of claim 12 wherein each of the manifolds comprises a primary manifold, a secondary manifold, and a plurality of headers wherein

each of the secondary manifolds having an inner channel portion for each of the gaps as part of the elongated flow passageway, the inner channel portion narrowing from an outer channel portion;

the secondary manifolds positioned such that the thin slabs and the windows substrates are interposed between the secondary manifolds in the transverse direction, the outer channel portion and the inner channel portion narrow down in a tapered manner to maintain a laminar flow of the coolant flow;

each of the primary manifolds engaging the secondary manifold, each of the primary manifolds having a cavity and a passage for each of the outer channel portions in the secondary manifolds as part of the elongated flow passageway of the manifolds; and

each of the headers having a plenum for moving the coolant towards and away from the manifolds; and

wherein the windows and the thin slabs have rounded edges to create a laminar flow of the coolant fluid.

14. A zig-zag laser head of claim 12 further comprising a plurality of perforated plates, each plate having a plurality of perforations for passage of coolant therein removing the longitudinal flow component of the fluid.

15. A zig-zag laser head of claim 12 wherein the thin slab is a plurality of thin slabs for lasing, the thin slabs extending longitudinally and parallel to each other in the transverse plane and a gap interposed between each of the thin slabs in addition to the gap interposed between the thin slabs and the windows.

16. A zig-zag laser head of claim 15 wherein each of the manifolds comprises a primary manifold, a secondary manifold, and a plurality of headers wherein

each of the secondary manifolds having an inner channel portion for each of the gaps as part of the elongated flow passageway, the inner channel portion narrowing from an outer channel portion;

the secondary manifolds positioned such that the thin slabs and the windows are interposed between the secondary manifolds in the transverse direction, the outer channel portion and the inner channel portion narrow down in a tapered manner to maintain a laminar flow of the coolant flow

each of the primary manifolds engaging the secondary manifold, each of the primary manifolds having a cavity and a passage for each of the outer channel portions in the secondary manifolds as part of the elongated flow passageway of the manifolds; and

each of the headers having a plenum for moving the coolant towards and away from the manifolds; and

wherein each of the thin slabs has at least one groove on each of its lateral edges and each of the secondary manifolds has a plurality of grooves on an edge engaging the slabs, and further comprising an expanded polyetrafluoroethylene (PTFE) interface seal having a series of slots, the expanded PTFE interface seal interposed between the secondary manifold and the quartz window and the thin slabs and interacting with the grooves for holding the thin slabs parallel to each other and forming a seal.