Claims:1. A fibre laser source device comprising:
a plurality of laser diodes;
at least one active fibre spool;
optical units;
electronic circuits;
an enclosure having a top enclosure and a bottom enclosure forming a two layer enclosure structure for enclosing plurality of laser diodes, active fibre spools, optical units, and electronic circuits;
a common heat sink assembly configured between the top enclosure and the bottom enclosure; and
a sealing assembly for sealing all components of the fibre laser source from outer side.
2. The fibre laser source device as claimed in claim 1, wherein the common heatsink module comprises a plurality of heat sink plates with bonded fins, peltier coolers, thermal barrier sheets, and a set of axial fans is placed in between the top and bottom enclosures.
3. The fibre laser source device as claimed in claim 2, wherein the fin array in the heat sink plate having the fin thickness, gap between adjacent fins and fin height from the base of the fin in the proportion of 1:3:30 respectively for optimum heat transfer.
4. The fibre laser source device as claimed in claim 1, wherein the sealing assembly comprises a top enclosure plate, and a bottom enclosure plate, and wherein the top enclosure plate and the bottom enclosure plate are configured to seal the components of the fibre laser source device using conductive elastomer gaskets from top and bottom.
5. The fibre laser source device as claimed in claim 1, wherein the fibre laser source device comprises a set of metallic ducts for the interconnection between the top and bottom enclosures, and wherein the set of metallic ducts are configured for interconnections between the optical and electrical components in the top and bottom enclosures.
6. The fibre laser source device as claimed in claim 1, wherein each of the top and bottom enclosures comprises at least one spiral groove with either semicircular or rectangular cross section, wherein length of the spiral grooves matching to the length of the active fiber spool which is acting as a gain medium.
7. The fibre laser source device as claimed in claim 6, wherein a pitch of the spiral groove is being greater than or equal to 1.4 mm.
8. The fibre laser source device as claimed in claim 6, wherein the spiral grooves are configured for laying the active fiber spool for better heat transfer from the active fiber spool to the op and bottom enclosures using necessary thermal grease to fill up the gap.
, Description:TECHNICAL FIELD
[0001] The present disclosure relates, generally, to a fiber laser source, and more particularly to an efficient technique for packaging a fibre laser source for thermal management of the fibre laser source.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] As is well known, a fibre laser source is one in which laser is produced from an active gain medium of optical fibre doped with rare earth elements such as erbium, ytterbium, thulium and holmium. Over the past few years the fibre laser source has been developed for applications in the field of medicine, metal cutting and engraving, telecommunication and weapon system.
[0004] Electronics and/or electrical devices/machines have predefined conditions under which they function at optimum levels. Deviation from these conditions can cause the devices to run at relatively lower efficiency, and under some circumstances, the devices may be damaged or can cease to function entirely.
[0005] The electronic equipment/devices now a days demands high performance in compact size. When it comes to the fibre laser source better performance requires efficient better cooling techniques. Size reduction is very essential for portable applications. It is also important to achieve proper environmental sealing for applications in harsh environments. Thus, packaging of the fibre laser source and its thermal management to meet the requirement of industrial or defence applications has always been a major challenge.
[0006] Therefore, there is need in the art to provide a simple and efficient solution to overcome the foregoing limitations associated with the conventional fibre laser sources.
OBJECTS OF THE PRESENT DISCLOSURE
[0007] Some of the objects of the present disclosure, which at least one embodiment herein satisfies are as listed herein below.
[0008] It is an object of the present disclosure to provide a simple and efficient solution to overcome the foregoing limitations associated with the conventional fibre laser sources.
[0009] It is an object of the present disclosure to provide a technique for packaging a fibre laser source for efficient thermal management of the fibre laser source.
[0010] It is an object of the present disclosure to provide an improved fibre laser source with an efficient cooling arrangement for thermal management of the fibre laser source.
[0011] It is an object of the present disclosure to provide a simple and cost-effective fibre laser source with better cooling feature as compared to conventional fibre laser sources.
[0012] It is an object of the present disclosure to provide a simple and efficient technique for thermal management method of a hermitically sealed fibre laser source.
[0013] These and other objects of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY
[0014] The present disclosure relates to a fiber laser source, and more particularly to a technique for packaging a fibre laser source for efficient thermal management of the fibre laser source.
[0015] In an aspect, the present disclosure provides an improved fibre laser source device that includes a plurality of laser diodes; at least one active fibre spool; optical units/accessories; electronic circuits, and an enclosure having a top enclosure and a bottom enclosure forming a two layer enclosure structure for enclosing plurality of laser diodes, active fibre spools, optical units, and electronic circuits. The improved fibre laser source device further include a common heat sink assembly configured between the top enclosure and the bottom enclosure; and a sealing assembly for sealing all components of the fibre laser source from outer side.
[0016] In an embodiment, the common heat sink assembly can include a plurality of heat sink plates with bonded fins, peltier coolers, thermal barrier sheets, and a set of axial fans is placed in between the top and bottom enclosures.
[0017] In an embodiment, the fin array in the heat sink plate may have the fin thickness, gap between adjacent fins and fin height from the base of the fin in the proportion of 1:3:30 respectively for optimum heat transfer.
[0018] In an embodiment, the heat sink plate may have a ratio of surface area with fin to surface area without fin being greater than or equal to 13 for maximum heat transfer.
[0019] In an embodiment, the sealing assembly may include a top enclosure plate, and a bottom enclosure plate. The top enclosure plate and the bottom enclosure plate can be configured to seal the components of the fibre laser source device using conductive elastomer gaskets from top and bottom.
[0020] In an embodiment, the laser source device may include a set of metallic ducts for the interconnection between the top and bottom enclosure, wherein the set of metallic ducts are configured for interconnections between the optical and electrical components in the top and bottom enclosures with all the mechanical interfaces sealed using suitable sealing elements.
[0021] In an embodiment, each of the top and bottom enclosures can include at least one spiral groove with either semicircular or rectangular cross section, wherein length of the spiral groove matching to the length of the active fiber spool which is acting as a gain medium. The pitch of the spiral groove can be greater than or equal to 1.4 mm. 8.
[0022] In an embodiment, the spiral grooves are configured for laying the active fiber spool for better heat transfer from the active fiber spool to the top and bottom enclosures using necessary thermal grease to fill up the gap.
[0023] In an embodiment, the fibre laser source device can include an emergency key switch.
[0024] In an embodiment, the fibre laser source device can include handles for portability.
[0025] In an embodiment, the fibre laser source device can include a set of external interface connectors and cable glands for necessary external electrical and optical connections.
[0026] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.
[0028] FIG. 1 illustrates an exemplary exploded view of the proposed fiber laser source device, in accordance with embodiments of the present disclosure.
[0029] FIG. 2 illustrates an exemplary cross section view of a common heatsink module in the proposed fiber laser source device, in accordance with embodiments of the present disclosure.
[0030] FIG. 3 illustrates an exemplary represention of a spiral groove in either top enclosure or bottom enclosure of the proposed fiber laser source device, in accordance with embodiments of the present disclosure.
[0031] FIG. 4 illustrates an exemplary blockdiagram representation of a heat sink assembly of the proposed fiber laser source device, in accordance with embodiments of the present disclosure.
[0032] FIG. 5 illustrates an exemplary cut plot of a thermal simulation result of the proposed fiber laser source device without forced convection cooling and peltier coolers at an ambient of 60°C and 101.3 kPa.
[0033] FIG. 6 illustrates an exemplary cut plot of a thermal simulation result of the proposed fiber laser source device with forced convection cooling and peltier coolers at an ambient of 60°C and 101.3 kPa, in accordance with embodiments of the present disclosure.
[0034] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION
[0035] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[0036] Various methods described herein may be practiced by combining one or more machine-readable storage media containing the code according to the present invention with appropriate standard computer hardware to execute the code contained therein. An apparatus for practicing various embodiments of the present invention may involve one or more computers (or one or more processors within a single computer) and storage systems containing or having network access to computer program(s) coded in accordance with various methods described herein, and the method steps of the invention could be accomplished by engine s, routines, subroutines, or subparts of a computer program product.
[0037] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0038] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0039] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0040] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[0041] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).
[0042] Embodiments explained herein relate to a fiber laser source, and more particularly to a technique for packaging a fibre laser source for efficient thermal management of the fibre laser source.
[0043] In an embodiment, the present disclosure provides an improved fibre laser source device with the efficient packaging for better thermal management. The fibre laser source device can include laser diode modules, active fibre spool and other optical accessories along with essential electronic boards and wirings in a two layer enclosure. One of the advantages of two layer enclosure structure is reduction of size. In the proposed fibre laser source device the optical lay out is split in to two portions making it convenient to contain them in two enclosures one at the top and the other one at the bottom. This way of packaging reduces the mounting area required for the fibre laser source device to half.
[0044] In an embodiment, a common heat sink module/assembly is placed in between the top and bottom enclosures which can cater to cooling requirement of components mounted inside both the top and bottom enclosures of the fibre laser source device.
[0045] The laser diodes and active fibre spool acting as a gain medium are the major heat dissipating components. For high performance and improved life of these components it is essential to employ proper thermal management. Certain applications demand operation of laser source in high temperature environments, where certain components like laser diode may not function as required. In such cases only forced convection cooling may not be sufficient. One of the resolutions is to use thermo electric cooler. Thermo electric cooler can be obtained with a small form factor and controllable output, which is suitable for devices which are portable.
[0046] Another aspect of environmental screening is sealing. Some components like optical fibre, laser diode and electronics associated with the laser source may degrade when subjected to harsh environment. Hence proper environmental sealing is also essential. In the proposed fibre laser source device two enclosures are sealed using suitable sealing element. Connectivity between components mounted in two enclosures is achieved using three metallic ducts which are also environmentally sealed at the interfaces. Using this concept it is possible to use forced convection cooling along with Peltier coolers and still achieve required environmental sealing.
[0047] Referring to FIGs. 1 and 2 where an exemplary exploded view and a sectional view of the proposed fiber laser source device are shown. The proposed fiber laser source device (hereinafter, also referred to as fiber laser source) can include an enclosure having a top enclosure 1 and bottom enclosure 2 together form two layer enclosure structure for packaging of laser diodes 5, active fiber spool 14, necessary optical accessories 6 and necessary electronic circuits 4 of the fiber laser source device. The fiber laser source device also includes a set of metallic ducts 15 that are provided for the interconnection between top and bottom enclosures. The set of metallic ducts are configured for interconnections between the optical and electrical components in the top enclosure 1 and the bottom enclosure2 with all the mechanical interfaces sealed using suitable sealing elements.
[0048] In an embodiment, the fibre laser source device includes common heat sink assembly that can include four heat sink plates with bonded fins 3a, 3b, 3c and 3d, Peltier coolers 3e, thermal barrier sheets 3f, and a set of axial fans 3g placed in between the top enclosure 1 and bottom enclosure 2.
[0049] In an embodiment, the fin array in the heat sink plate may have the fin thickness, gap between adjacent fins and fin height from the base of the fin in the proportion of 1:3:30 respectively for optimum heat transfer.
[0050] In an embodiment, the heat sink plate may have a ratio of surface area with fin to surface area without fin being greater than or equal to 13 for maximum heat transfer.
[0051] In an embodiment, the fibre laser source device can include a sealing assembly for sealing all components of the fibre laser source from outer side. In another embodiment, the sealing assembly may include a top enclosure plate 9, and a bottom enclosure plate 8. The top enclosure plate 9 and the bottom enclosure plate 8 can be configured to seal the components of the fibre laser source device using conductive elastomer gaskets from top and bottom.
[0052] In an embodiment, each of the top and bottom enclosures can include at least one spiral groove 302 (shown in FIG. 3) with either semicircular or rectangular cross section, wherein length of the spiral groove matching to the length of the active fiber spool which is acting as a gain medium. A pitch of the spiral groove can be greater than or equal to 1.4 mm. 8.
[0053] In an embodiment, the spiral grooves 303 are configured for laying the active fiber spool for better heat transfer from the active fiber spool to the top and bottom enclosures using necessary thermal grease to fill up the gap.
[0054] In an embodiment, the fibre laser source device can include an emergency key switch 7.
[0055] In an embodiment, the fibre laser source device can include one or more handles 10 for portability.
[0056] In an embodiment, the fibre laser source device can include a set of external interface connectors and cable glands 11 for necessary external electrical and optical connections.
[0057] In an embodiment, optical engine of the fibre laser source device is based on Master oscillator and power amplifier (MOPA) principle. Master oscillator stage may produce power in milli-watt range, which can be amplified by single stage amplifier to obtain power in watt regime. Master oscillator and power amplifier can be placed in separate enclosures having provision for interconnection.
[0058] The common heat sink assembly can be employed to carry away the heat dissipated in master oscillator stage and power amplifier stage. This method of packaging the fibre laser source reduces the standing area which is desirable for portable applications.
[0059] Both Master oscillator and power amplifier have critical components which may not operate as desired above 50 °C Wall temperature. These components also dissipate heat, magnitude of which may go up to 90 watt. Furthermore the fibre laser source may find applications in harsh environment, temperature of which may go up to 60 °C or worse. For above heat load if the fibre laser source is operated at an ambient of 60 °C temperature, The surface temperature of the laser diodes 5 may reach to a magnitude of the order 1000 if necessary cooling technique is not implemented ( shown in FIG. 5). It may be impossible to use only forced convection cooling since temperature of ambient air itself is greater than required wall temperature. This shortcoming can be overcome by employing thermo electric cooler modules (3e). Thermo electric cooler modules are also known as Peltier coolers. The cooling capacity of the Peltier coolers can be controlled by controlling the input current. By using temperature sensors, wall temperature at required hotspots can be measured and the data can be fed to the main controller circuit, which in turn controls the input current to the Peltier coolers and there by achieving the required wall temperature at that region.
[0060] In an exemplary embodiment, three Peltier coolers are used, one Peltier cooler is placed below the laser diode 5 mounted in top enclosure 1, hot surface of which is cooled by a separate heat sink plate having bonded fins and two Peltier coolers are placed above the laser diodes 5 mounted in the bottom enclosure 2, hot surface of which is cooled by one more heat sink plate having bonded fins 3. Two heat sink plates are in contact with top and bottom housing as shown in FIG 2. Hence altogether four heat sink plates with bonded fins 3 are employed in the proposed design.
[0061] In an exemplary embodiment, the set of axial fans 3g is used for forced convection cooling. With the present set up the ratio of heat sink area with fins to heat sink area without fins is 13.5, whereas the mounting area required is reduced to half with two later arrangements. The fin thickness, gap between adjacent fins and fin height from the base are maintained in the proportion of 1:3:30 for optimum heat transfer. Material of the enclosure and the heat sink can be any metal or alloys having thermal conductivity value of 200 W/mK or more. With this set up wall temperature in the vicinity of the laser diodes 5 may be maintained below 50 °C (as shown in FIG. 6).
[0062] In an exemplary embodiment, the heat sink module may be designed to work without switching on the Peltier coolers up to certain wall temperature limit. The wall temperature in the vicinity of the heating elements i.e. laser diodes may be recorded using temperature sensors and same data may be fed to the control circuit. When said wall temperature crosses the set limit the control circuit may activate the Peltier coolers.
[0063] In an embodiment, the active fibre 14 is the gain medium for lasing and it may also dissipate heat. For better heat transfer from the active fibre 14 to metal body of the enclosure spiral grooves of either semi-circular or rectangular cross section may be made in the enclosures and the active fibre may be laid in those grooves 302 (shown in FIG. 3). Suitable thermal grease may be used at the fibre–metal interface to improve the heat transfer.
[0064] In an embodiment, the interconnection between components in top and bottom enclosures is achieved through the set of metallic ducts 15. All the interfaces may be sealed using suitable sealing element. In fibre laser source device, conductive elastomer gasket with silicone binder and conductive silver plated copper fillers can be used. All the external interface connectors and cable glands 11 may be selected such that to provide maximum sealing against dust and moisture ingress.
[0065] FIG. 3 illustrates an exemplary represention of a spiral groove in either top enclosure or bottom enclosure of the proposed fiber laser source device, in accordance with embodiments of the present disclosure. The spiral groove 302 in either top or bottom enclosure with either semicircular or rectangular cross section for laying the active fiber spool 14 using a suitable thermal grease. Interconnection metallic duct 15 opening is also shown.
[0066] FIG. 4 illustrates an exemplary blockdiagram representation of a heat sink assembly of the proposed fiber laser source device, in accordance with embodiments of the present disclosure. Peltier coolers are placed below the heating element and temperature sensor is placed adjacent to heating element. Wall temperature is measured by the temperature sensor and data is fed to control card and accordingly control card controls the input current to petlier cooler from power supply card. A set of axial fans (Not shown in above figure) are used for forced convection cooling.
[0067] FIG. 5 illustrates an exemplary cut plot of a thermal simulation result of the proposed fiber laser source device without forced convection cooling and peltier coolers at an ambient of 60°C and 101.3 kPa. Heat sink metal considered here is Aluminium 6061-T6 alloy. For example, a flow simulation module of Solidworks software (2017 version) is used for thermal simulation. Laser diodes and active fiber are modelled as surface heat sources on the heat sink (3a). The wall temperature reaches beyond 1000°C in this case.
[0068] FIG. 6 illustrates an exemplary cut plot of a thermal simulation result of the proposed fiber laser source device with forced convection cooling and peltier coolers at an ambient of 60°C and 101.3 kPa, in accordance with embodiments of the present disclosure. Heat sink metal considered here is Aluminium 6061-T6 alloy. For example, a flow simulation module of Solidworks software (2017 version) is used for thermal simulation. Laser diodes and active fiber are modelled as surface heat sources on the heat sink (3a). Temperature in the vicinity of the peltier cooler (3e) is maintained at around 20°C. Hence by placing the peltiers cooler below the laser diodes surface temperature of the laser diode can be maintained below 50°C.
[0069] Thus, it will be appreciated by those of ordinary skill in the art that the diagrams, schematics, illustrations, and the like represent conceptual views or processes illustrating systems and methods embodying this invention. The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing associated software. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the entity implementing this invention. Those of ordinary skill in the art further understand that the exemplary hardware, software, processes, methods, and/or operating systems described herein are for illustrative purposes and, thus, are not intended to be limited to any particular named.
[0070] While embodiments of the present invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claim.
[0071] In the foregoing description, numerous details are set forth. It will be apparent, however, to one of ordinary skill in the art having the benefit of this disclosure, that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, to avoid obscuring the present invention.
[0072] As used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (in which two elements that are coupled to each other contact each other)and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Within the context of this document terms "coupled to" and "coupled with" are also used euphemistically to mean “communicatively coupled with” over a network, where two or more devices are able to exchange data with each other over the network, possibly via one or more intermediary device.
[0073] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C …. N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0074] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0075] The present disclosure provides a simple and efficient solution to overcome the foregoing limitations associated with the conventional fibre laser sources.
[0076] The present disclosure provides a technique for packaging a fibre laser source for efficient thermal management of the fibre laser source.
[0077] The present disclosure provides an improved fibre laser source with an efficient cooling arrangement for thermal management of the fibre laser source.
[0078] The present disclosure provides a simple and cost-effective fibre laser source with better cooling feature as compared to conventional fibre laser sources.
[0079] The present disclosure provides a simple and efficient technique for thermal management method of a hermitically sealed fibre laser source.