System and method for providing thermal management of an obscured laser system

According to an embodiment of the disclosure, a system for providing thermal management of an obscured laser system is provided that includes a primary mirror, a secondary mirror, and a plurality of energy redirectors. The primary mirror is configured to reflect beam energy for the laser system. The secondary mirror is configured to function as a limiting aperture for the laser system and is aligned on-axis with respect to the primary mirror. The energy redirectors are each configured to redirect energy away from a corresponding obscuration and out of the laser system.

TECHNICAL FIELD

The present disclosure is directed, in general, to lasers and, more specifically, to a system and method for providing thermal management of an obscured laser system.

BACKGROUND OF THE DISCLOSURE

Compact, high-power laser systems typically rely on in-line systems, which have obscurations such as secondary mirrors, struts holding the system mirrors, and the like. The energy blocked by the obscurations may be scattered back into the system, causing substantial system heating. To address this issue, conventional obscured laser systems implement one or more existing solutions, including long cycle times and a beam dump. Off-axis laser systems may also be used to avoid the obscuration entirely.

Thus, some obscured laser systems provide long cycle times, thereby allowing the systems sufficient time to cool between shots. However, long cycle times have disadvantages that include a reduction in system effectiveness.

For systems including a beam dump, heat may be transferred out of the system using the beam dump. For example, some laser systems implement a cooling block that provides radiative or liquid cooling. However, such a cooling block requires cooling lines and pumps. In addition, using a cooling block reduces cycle time while waiting for the cooling block to cool and reduces the length of on time for the laser system. The complexity of a beam dump also reduces system reliability.

Off-axis systems attempt to avoid any obscurations that would require a beam dump by arranging the components off-axis from each other. However, off-axis systems typically require more space and are more difficult to align. In addition, the off-axis mirror sections are harder to manufacture and test.

SUMMARY OF THE DISCLOSURE

This disclosure provides a system and method for providing thermal management of an obscured laser system.

In one embodiment, a system for providing thermal management of an obscured laser system is provided that includes a primary mirror, a secondary mirror, and a plurality of energy redirectors. The primary mirror is configured to reflect beam energy for the laser system. The secondary mirror is configured to function as a limiting aperture for the laser system and is aligned substantially on-axis with respect to the primary mirror. The energy redirectors are each configured to redirect energy away from a corresponding obscuration and out of the laser system.

In another embodiment, a system for providing thermal management of an obscured laser system is provided that includes a primary mirror, a secondary mirror, and a central energy redirector. The primary mirror is configured to reflect beam energy for the laser system. The secondary mirror is configured to function as a limiting aperture for the laser system. The secondary mirror is aligned substantially on-axis with respect to the primary mirror and includes a central region. The central energy redirector is configured to redirect energy directed toward the central region. The primary mirror is configured to reflect the energy redirected away from the central region by the central energy redirector.

In yet another embodiment, a method for providing thermal management of an obscured laser system is provided that includes receiving laser energy at a primary/secondary set. The primary/secondary set includes a primary mirror and a secondary mirror that is aligned substantially on-axis with respect to the primary mirror. A first portion of the laser energy is directed into beam energy for the laser system. A second portion of the laser energy is directed away from a plurality of obscurations in the laser system and out of the laser system as excess energy.

DETAILED DESCRIPTION

FIG. 1illustrates an application10that includes a laser12in accordance with the present disclosure. The embodiment of the application10shown inFIG. 1is for illustration only. Other embodiments of the application10could be used without departing from the scope of this disclosure.

In addition to the laser12, the application10comprises an application controller14and a laser beam processor16. The application10may be configured to perform any suitable operation that uses the laser12in its implementation. For example, the application10may be used for cutting, drilling, welding, engraving, cladding, aligning, micro-machining, heat-treating, imaging, ablating or any other suitable operation. The application10may be useful for industrial purposes, medical purposes, microelectronics manufacturing, graphics purposes, law enforcement purposes, entertainment purposes, scientific research, consumer electronics, defense or military purposes and/or for any other suitable purpose.

Depending on the application10, the laser12may comprise a gas laser, a chemical laser, a solid-state laser, a fiber laser, a semiconductor laser or other suitable type of light source. Also depending on the application10, the laser12may be configured to operate in a continuous wave mode and/or a pulsed mode, such as Q-switched, mode-locked, pulse-pumped and/or other suitable pulsed mode.

For the illustrated embodiment, the laser12comprises an optical cavity20, a pumper22, and a laser controller24. The optical cavity20comprises a gain medium30, a reflector32and an output coupler34. The gain medium30comprises any suitable material that may be pumped by the pumper22in order to provide optical gain for the laser12. The reflector32may comprise a high-reflectivity mirror that is configured to reflect substantially all the light from the gain medium30back through the optical cavity20. The output coupler34may comprise a partially reflective mirror. The output coupler34is configured to reflect a portion of the light from the gain medium30back through the optical cavity20and to transmit another portion of the light from the gain medium30as an output laser beam40.

The laser controller24is configured to control the pumper22. For example, based on a control signal42from the application controller14, the laser controller24may be configured to turn the pumper22on and off by generating a pumper signal44. The pumper22is configured to generate energy46based on the pumper signal44and to direct that energy46toward the gain medium30of the optical cavity20.

The application controller14is configured to provide control of the laser12for the application10. For example, the application controller14may be configured to generate the control signal42in order to activate the laser12such that the application10may use the laser12to perform a specified task. In addition, the application controller14may be configured to deactivate the laser12when the task is completed. The application controller14may also be configured to provide control of other components of the application10, such as the laser beam processor16and/or other suitable components (not shown inFIG. 1).

The laser beam processor16is configured to process the laser beam40in accordance with the application10in order to generate a processed laser beam48. For example, the laser beam processor16may be configured to route the laser beam40based on the application10. As a specific example, the laser beam processor16may be configured to direct the processed laser beam48toward a predetermined target, such as a mortar, a machine, electronics, a vehicle, a body part, or any other suitable target.

AlthoughFIG. 1illustrates one example of an application10including a laser12, various changes may be made toFIG. 1. For example, the makeup and arrangement of the application10are for illustration only. Components could be added, omitted, combined, subdivided, or placed in any other suitable configuration according to particular needs. In addition,FIG. 1illustrates one environment in which the laser12may be implemented. However, the laser12may be used in any other suitable system without departing from the scope of this disclosure.

FIG. 2illustrates a block diagram of an obscured laser system100in which thermal management may be implemented in accordance with the present disclosure. The embodiment of the laser system100shown inFIG. 2is for illustration only. Other embodiments of the laser system100could be used without departing from the scope of this disclosure.

The illustrated laser system100comprises a fiber102, a coupler set104, a beam walk set106and a primary/secondary set108. The fiber102may comprise a 50 kW fiber laser or any other suitable type of laser. The fiber102is configured to generate laser energy110for the laser system100. The coupler set104comprises any suitable arrangement of mirrors and/or lenses for directing the laser energy110generated by the fiber102to the beam walk set106. For some embodiments, the coupler set104comprises an all-reflective coupler that is configured to handle a heat load higher than that of a refractive system. In addition, the coupler set104is configured to match the laser energy110out of the fiber102to the primary/secondary set108. The beam walk set106comprises any suitable arrangement of mirrors and/or lenses for directing the laser energy110received from the coupler set104to the primary/secondary set108. In addition, the beam walk set106is configured to provide fine beam steering of the laser energy110towards a target while keeping the laser energy110substantially centered physically with respect to the primary/secondary set108. The primary/secondary set108may comprise a plurality of mirrors that are configured to concentrate the laser energy110from the beam walk set106onto the target. As illustrated inFIG. 2, the laser energy110may be referred to as laser energy110awhen generated by the fiber102, as laser energy110bwhen directed by the coupler set104to the beam walk set106, and as laser energy110cwhen directed from the beam walk set106to the primary/secondary set108.

As described in more detail below, the primary/secondary set108may comprise primary and secondary structures configured to direct the laser energy110creceived from the beam walk set106into an energy beam112, which is the output of the laser system100. The primary/secondary set108comprises an in-line set such that the laser system100comprises an obscured system. While the obscurations in a conventional obscured laser system would scatter a significant amount of energy back into the system, the obscurations in the laser system100do not scatter a large amount of energy back into the laser system100. Instead, most of the energy that would otherwise be scattered back into the system100is directed out of the system100as excess energy114. Therefore, a relatively large portion of the laser energy110cis directed either into the energy beam112or out of the laser system100as excess energy114. As a result, the excess energy114does not become trapped and heat up the components of the system100. Thus, the system100does not require the use of a beam dump to provide cooling.

For some embodiments, the fiber102may correspond to the laser12, the coupler set104, the beam walk set106and the primary/secondary set108may correspond to the laser beam processor16, the laser energy110amay correspond to the laser beam40, and the energy beam112and the excess energy114may correspond to the processed laser beam48.

FIGS. 3A-Cillustrate thermal management of the obscured laser system100in accordance with various aspects of the present disclosure. The embodiments of the laser system100shown inFIGS. 3A-Care for illustration only. Other embodiments of the laser system100could be used without departing from the scope of this disclosure.

As shown inFIGS. 3A-C, the primary/secondary set108comprises a primary mirror202and a secondary mirror204that are aligned substantially on-axis with respect to each other. The primary mirror202comprises an aperture206that allows the laser energy110cdirected by the beam walk set106to pass through the primary mirror202. For some embodiments, the primary mirror202comprises a large diamond-turned aluminum mirror.

As shown inFIG. 3A, the secondary mirror204comprises a stop for the laser system100, i.e., the secondary mirror204is a limiting aperture for the laser system100. Thus, a first portion of excess energy114aincluded in the laser energy110cis allowed to pass by the edges of the secondary mirror204and out of the system100. As a result, this excess energy114ais not scattered back into the system100and absorbed.

As shown inFIGS. 3B-C, the secondary mirror204comprises a peripheral region208and a central region210. At least a portion of the laser energy110ccoming through the aperture206comprises peripheral energy222, which is energy that strikes the peripheral region208. The peripheral energy222is reflected off the peripheral region208of the secondary mirror204as reflected peripheral energy224, which strikes the primary mirror202and is reflected off the primary mirror202as beam energy112.

At least another portion of the laser energy110ccoming through the aperture206comprises central energy232, which is energy that is directed toward the central region210of the secondary mirror204. If the central energy232struck the central region210of the secondary mirror204, reflected central energy234would be directed back through the aperture206and into the system100. Thus, the primary/secondary set108may comprise an energy redirector in the form of a central energy redirector240that is configured to redirect the reflected central energy234to the primary mirror202instead of to the aperture206. The primary mirror202may then reflect the reflected central energy234as beam energy112. In the embodiment illustrated inFIG. 3C, the central energy redirector240comprises an axicon. However, it will be understood that any other suitable device may be implemented to redirect the reflected central energy234such that at least a significant portion of the reflected central energy234is directed toward the primary mirror202.

The central energy redirector240is coupled to, or located in close proximity to, the central region210of the secondary mirror204. For some embodiments, the central energy redirector240may block substantially all of the central region210of the secondary mirror204and may not block substantially all of the peripheral region208of the secondary mirror204. However, it will be understood that the central energy redirector240may be configured so as not to block an insignificant portion of the central region210and/or to block an insignificant portion of the peripheral region208without departing from the scope of this disclosure.

FIGS. 4A-Billustrate thermal management of the obscured laser system100through the use of V-guards302in accordance with the present disclosure. The V-guards302are energy redirectors that are configured to redirect energy away from obscurations. The embodiments of the V-guards302shown inFIGS. 4A-Bare for illustration only. Other embodiments of the V-guards302could be used without departing from the scope of this disclosure.

As shown inFIGS. 4A-B, a strut304that may be configured to couple the secondary mirror204to a housing for the laser system100(not shown inFIGS. 4A-B) may be in a path of energy306reflected off the primary mirror202that would be included as beam energy112if not for the strut304blocking the energy306from exiting the laser system100. If the energy306struck the stmt304, the energy306would heat up the strut304. This could result in the stmt304becoming twisted or bent, thereby interfering with the projection of the beam energy112from the laser system100. Also, the energy306would scatter off the strut304in an uncontrolled manner.

Thus, as shown inFIGS. 4A-B, a V-guard302may be coupled to, or located in close proximity to, the strut304. The V-guard302is configured to direct the energy306away from the strut304and out of the system100as excess energy114in a controlled manner. The length-to-width ratio of the V-guard302may be selected in order to result in the excess energy114exiting the system100at a specified angle. For example, as shown inFIG. 4A, when the V-guard302ahas a shorter length relative to its width, the excess energy114bmay exit the system100at a higher angle, such as 20°. Similarly, as shown inFIG. 4B, when the V-guard302bhas a longer length relative to its width, the excess energy114cmay exit the system100at a smaller angle, such as 4°. Thus, for example, an appropriate length-to-width ratio for the V-guard302may be selected such that the angle of the excess energy114is limited in a manner that ensures that the excess energy114directed out of the system100by the V-guard302will not result in an eye hazard.

FIGS. 5A-Billustrate thermal management of the obscured laser system100through the use of tapers452in accordance with the present disclosure.FIG. 5Aillustrates a housing400in which no tapers are implemented andFIG. 5Billustrates a housing450in which tapers452are implemented in order to show the difference in thermal management when tapers452are added to the housing450. The embodiments of the housing400and450shown inFIGS. 5A-Bare for illustration only. Other embodiments of the housing400or450could be used without departing from the scope of this disclosure.

As shown inFIGS. 5A-B, a portion of the housing400or450for the laser system100may be implemented that includes a mount402for the secondary mirror204, which includes struts404that couple the mount402to the housing400or450, an output window406, a mounting ring408for the output window406, and primary edge guards410for the primary mirror202.

As described above,FIG. 5Aillustrates the housing400for the laser system100in which no tapers are implemented. For this example, peripheral energy222comes through the aperture206, strikes the peripheral region208of the secondary mirror204, and is reflected off the secondary mirror204as reflected peripheral energy224aand224b. In the illustrated example, the reflected peripheral energy224ais reflected off one of the primary edge guards410as obscured energy420a. The stmt404scatters the obscured energy420aback into the system100as trapped energy422a. Similarly, the reflected peripheral energy224bis reflected off the primary mirror202as obscured energy420b. The mounting ring408scatters the obscured energy420bback into the system100as trapped energy422b.

Therefore, any one of a number of obscurations, such as the struts404, mounting rings408or the like, may reflect obscured energy420back into the system100as trapped energy422. This trapped energy422, which is energy that does not exit the system100as intended, may heat up components of the laser system100, reducing both system effectiveness and on time for the laser system100.

As described above,FIG. 5Billustrates the housing450for the laser system100in which tapers452are implemented. The tapers452are energy redirectors that are configured to redirect energy away from obscurations. For the illustrated embodiment, tapers452are coupled to the struts404and the mounting ring408. However, it will be understood that tapers452may be coupled to, or located in close proximity to, any suitable obscuration of the system100that is capable of causing back reflections. The embodiments of the tapers452shown inFIG. 5Bare for illustration only. Other embodiments of the tapers452could be used without departing from the scope of this disclosure.

For this embodiment, peripheral energy222comes through the aperture206, strikes the peripheral region208of the secondary mirror204, and is reflected off the secondary mirror204as reflected peripheral energy224aand224b. In the illustrated example, the reflected peripheral energy224ais reflected off one of the primary edge guards410as unobscured energy460a. Instead of being reflected back into the system100by the stmt404, the unobscured energy460ais reflected off the taper452aand out of the system100as excess energy114d. Similarly, the reflected peripheral energy224bis reflected off the primary mirror202as unobscured energy460b. Instead of being reflected back into the system100by the mounting ring408, the unobscured energy460bis reflected off the taper452band out of the system100as excess energy114e.

Thus, as described above, a taper452may be provided for any suitable obscuration, such as the struts404, mounting ring408or the like, in order to reflect unobscured energy460out of the system100as excess energy114instead of allowing obscured energy420to become trapped energy422. In this way, excess energy114is removed from the system and, thus, is unavailable to heat up components of the laser system100. As a result, the housing450provides increased system effectiveness and greater on time for the laser system100as compared to the housing400.

FIG. 6is a flowchart illustrating a method500for providing thermal management of the obscured laser system100in accordance with the present disclosure. The method500shown inFIG. 6is for illustration only. Thermal management may be provided for the laser system100in any other suitable manner without departing from the scope of this disclosure.

Initially, the laser system100generates laser energy110(step502). For example, the fiber102may generate laser energy110a. The laser energy110is directed through the aperture206of the primary mirror202(step504). For example, the coupler104may receive the laser energy110agenerated by the fiber102and direct laser energy110bto the beam walk set106, and the beam walk set106may receive the laser energy110band direct laser energy110cto the primary/secondary set108. Specifically, the beam walk set106may direct the laser energy110cthrough the aperture206of the primary mirror202.

A first portion of excess energy114ais allowed to pass by the edges of the secondary mirror204and out of the system100(step506). Thus, the secondary mirror204functions as a limiting aperture, or stop, for the system100. A second portion of excess energy114bor114cis directed away from obscurations and out of the system100by at least one V-guard302(step508). For example, a V-guard302may be provided for each stmt304in order to redirect energy306out of the system100. A third portion of excess energy114dand/or114eis directed away from obscurations and out of the system100by at least one taper452(step510). For example, a taper452may be provided for each stmt404and/or mounting ring408in order to redirect unobscured energy460out of the system100.

Peripheral energy222is reflected off the peripheral region208of the secondary mirror204(step512), and the reflected peripheral energy224from the secondary mirror204is reflected off the primary mirror202and out of the system100as a first portion of beam energy112(step514). Central energy232is reflected off the central energy redirector240(step516), and the reflected central energy234from the central energy redirector240is reflected off the primary mirror202and out of the system100as a second portion of beam energy112(step518). For example, the central energy232may be reflected off a central energy redirector240that comprises an axicon coupled to the central region210of the secondary mirror204.

In this way, energy that would otherwise be obscured and scattered back into the obscured laser system100is released from the system100as excess energy114or included as beam energy112for the system100. For example, excess energy114ais passed out of the system100because the secondary mirror204is used as the limiting aperture for the system100. In addition, central energy232that would otherwise be incident on the central region210of the secondary mirror204is redirected by the central energy redirector240and added to the beam energy112. Energy306that would be incident on struts304is directed out of the system100as excess energy114band/or114cby V-guards302, and unobscured energy460that would otherwise be obscured energy420is directed out of the system100as excess energy114dand/or114eby tapers452.

AlthoughFIG. 6illustrates one example of a method500for providing thermal management of the obscured laser system100, various changes may be made toFIG. 6. For example, while shown as a series of steps, various steps inFIG. 6could overlap, occur in parallel, occur in a different order, or occur multiple times. In addition, some steps could be omitted for systems100that omit one or more of the secondary mirror204as a stop, the central energy redirector240, V-guards302and tapers452.

Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, as described above, steps may be performed in any suitable order.

It may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The term “each” refers to each member of a set or each member of a subset of a set. Terms such as “over” and “under” may refer to relative positions in the figures and do not denote required orientations during manufacturing or use. Terms such as “higher” and “lower” denote relative values and are not meant to imply specific values or ranges of values. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.