Description:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to the field of fiber lasers, and more specifically, relates to systems and methods for pumping kilowatt-class fiber lasers and amplifiers.

BACKGROUND
[0002] High-power fiber lasers and amplifiers are gaining momentum in various industrial applications. Power scaling in fiber lasers has advanced tremendously in the recent past but is limited by power and engineering bottlenecks. Notably, advancements in high-power diode laser technology alleviated the pump power requirement for high-power laser generation. However, thermal management of residual power from diode lasers as well as the active medium remains a critical engineering problem in the practical development of fiber laser sources.
[0003] A few existing systems are recited in US patent US9059555B2, that address some of these challenges by introducing wavelength-stabilized diode lasers utilizing hybrid external cavity laser technology with volume Bragg grating (VBG) technology. This approach enables the pumping of the fiber laser or amplifier using wavelength-stabilized diodes, maximizing pump absorption per unit length by aligning the diode wavelength with the highest absorption wavelength of the active medium. Consequently, the required length of gain fiber is reduced, lowering nonlinearity thresholds and facilitating better thermal management by minimizing unabsorbed pump power. However, this pumping scheme concentrates most of the pump power in the initial length of gain fiber, leading to a high thermal gradient in that region. As a result, thermal modal instabilities (TMI) can occur prematurely, limiting power scaling using wavelength-stabilized pump power.
[0004] To overcome the limitations imposed by the TMI threshold, various techniques have been developed in the field of fiber lasers and amplifiers. One such technique, as disclosed in US patent US9214781B2, involves employing a hybrid fiber with a small-core section followed by a large-core fiber as the gain medium in the fiber amplifier system. By limiting the heat per unit length in the small-core region to a value below the critical threshold for TMI generation, this approach mitigates thermal issues. Another technique, described in US patent US9325151B1, introduces a system for compensating the thermo-optic effect in high-power fiber lasers. This compensation is achieved by using a fiber with a position-varying bending diameter, inducing a high bending radius in the hot regions of the fiber to counteract thermal-induced refractive index gradients.
[0005] Although previous approaches have focused on modelling fibers with specific physical parameters to suppress thermal issues, the customization of these fibers is challenging due to stringent fabrication requirements. Therefore, it is desired to overcome the drawbacks, shortcomings, and limitations associated with existing solutions, and develop a cost-effective solution that can address the challenges encountered in kilowatt-class fiber lasers and amplifiers by providing a unique hybrid pumping technique for fiber lasers and amplifiers capable of generating kilowatt-class laser power.

OBJECTS OF THE PRESENT DISCLOSURE
[0006] An object of the present disclosure relates, in general, to the field of fiber lasers, and more specifically, relates to systems and methods for pumping kilowatt-class fiber lasers and amplifiers.
[0007] Another object of the present disclosure is to provide a system that provides simplified implementation using off-the-shelf components.
[0008] Another object of the present disclosure is to provide a system that improves thermal management and power-limiting factor mitigation.
[0009] Another object of the present disclosure is to provide a system that provides extra control over pump absorption by varying the ambient temperature.
[0010] Another object of the present disclosure is to provide a system that provides precise control of heat load on pump dump/CMS through a unique powering ON sequence.
[0011] Another object of the present disclosure is to provide a cost-effective solution for kW-class fiber lasers and amplifiers.
[0012] Yet another object of the present disclosure is to overcome power scaling bottlenecks efficiently.

SUMMARY
[0013] The present disclosure relates in general, to the field of fiber lasers, and more specifically, relates to systems and methods for pumping kilowatt-class fiber lasers and amplifiers. The main objective of the present disclosure is to overcome the drawback, limitations, and shortcomings of the existing system and solution, by providing a hybrid system and method for pumping kilowatt-class fiber lasers and amplifiers, addressing laser efficiency, thermal management, and power-limiting optical nonlinearities and instabilities. Unlike previous approaches that focused on designing specialty fibers, this invention proposes a careful combination of commercially available pump diodes.
[0014] The present disclosure utilizes a combination of wavelength-stabilized pump diodes and pump diodes without wavelength stabilization. The presence of wavelength-stabilized pump diodes ensures high absorption along the length of the active fiber, reducing its overall length and improving the nonlinearity threshold for high-power lasers. However, the proportion of high absorption pump wavelength is controlled to avoid rapid absorption in the initial length of the active fiber. This suppression of thermal gradient prevents the occurrence of thermal mode instabilities, a critical issue in high-power fiber lasers.
[0015] Additionally, the inclusion of pump diodes without wavelength stabilization provides control over laser efficiency. Moreover, by implementing a distinct powering ON sequence for both categories of diodes, the invention regulates the pumpdump temperature, which is crucial for effective thermal management in kilowatt fiber lasers and amplifiers. Furthermore, the present invention does not require any changes to conventional laser-building processes, distinguishing it from prior art approaches. By leveraging easily available standard components, this proposed hybrid pumping technique offers a practical, cost-effective, and efficient solution for overcoming power scaling limitations in kilowatt-class fiber lasers and amplifiers.
[0016] 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
[0017] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0018] FIG. 1 is an illustration showing the schematic block diagram of a typical fiber laser setup, in accordance with an embodiment of the present disclosure.
[0019] FIG. 2 is an illustration showing the schematic block diagram of a typical fiber amplifier setup, in accordance with an embodiment of the present disclosure.
[0020] FIG. 3 is an illustration showing a block diagram of a part of the system and method for pumping, in accordance with an embodiment of the present disclosure.
[0021] FIG. 4 is an illustration showing an extension block diagram of a part of the system and method for pumping, in accordance with an embodiment of the present disclosure.
[0022] FIG. 5 illustrates an exemplary flow chart of a method for pumping a fiber laser or fiber amplifier stage, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0023] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. 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.
[0024] 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.
[0025] The present disclosure relates, in general, to the field of fiber lasers, and more specifically, relates to systems and methods for pumping kilowatt-class fiber lasers and amplifiers. The proposed system disclosed in the present disclosure overcomes the drawbacks, shortcomings, and limitations associated with the conventional system by providing a system and method for pumping kilowatt-class fiber lasers and amplifiers, focusing on addressing the engineering challenges associated with achieving efficient power generation and effective thermal management. It proposes a novel hybrid pumping scheme that combines pump diodes with and without wavelength stabilization techniques. This approach offers exceptional control over laser efficiency, enabling precise thermal management and efficient pump absorption. This innovation is crucial for practical implementations of kilowatt-class fiber lasers and amplifiers, ensuring optimal performance and reliability.
[0026] The present disclosure presents a hybrid system and method for pumping kilowatt-class fiber lasers and amplifiers to control laser efficiency, improve thermal management and mitigate power-limiting optical nonlinearities and instabilities. Unlike, prior arts which concentrate on designing speciality fibers to suppress nonlinearities, this invention proposes the careful combination of commercially available pump diodes. The present invention uses a combination of wavelength-stabilized pump diodes along with pump diodes without wavelength stabilization. The presence of a wavelength stabilized pump ensures relatively high absorption along the length of the active fiber. Reduction in length resulting from high absorption improves nonlinearity threshold for high-power lasers. Yet, the proportion of high absorption pump wavelength is limited to avoid rapid absorption in the initial length of active fiber. Thus, the generation of thermal gradient is suppressed, in turn preventing the undesired build-up of thermal mode instabilities. The presence of pump diodes devoid of wavelength stabilization also provides essential control over laser efficiency. The wavelength tuning available in these diodes with respect to varying ambient temperature can be capitalized to improve the laser efficiency. Moreover, distinct powering ON sequences of both categories of diodes can further regulate the pumpdump temperature, a critical engineering issue in kilowatt fiber lasers and amplifiers. Specifically, contrary to the prior arts, the present invention does not require any change in conventional laser-building processes. The present disclosure can be described in enabling detail in the following examples, which may represent more than one embodiment of the present disclosure.
[0027] In an aspect, the system for pumping a fiber laser or fiber amplifier stage, the system includes a hybrid combination of pump diodes that emits laser power with the appropriate wavelength, the hybrid combination of pump diodes includes a first pump diode that operates using internal or external wavelength stabilizing mechanism and a second pump operates without internal or external stabilizing mechanism. A fiber-fused combiner combines the powers of the first pump diode and second pump diode, the combined power is fed into the doped fiber for amplification in the fiber laser or amplifier system. An external cooling unit configured for controlling the operating temperature of the first pump diode and second pump diode and one or more external electrical power supplies coupled to corresponding pump diodes to provide the required current and voltage control for the first pump diode and second pump diode.
[0028] In another aspect, the external cooling unit, individually, grouped, or combined, using liquid, forced air, thermoelectric coolers, or other temperature stabilizing mechanism for controlling the operating temperature of the first pump diode and second pump diode.
[0029] In another aspect, the system suppresses the nonlinearity threshold by optimizing gain fiber length through improved optical amplification efficiency due to the presence of the first pump diode, wherein the first pump diode is a wavelength-stabilized pump diode. The system enhances thermal management by reducing residual unabsorbed pump after the gain fiber due to the presence of the first pump diode. The system suppresses modal instabilities caused by thermal effects through gradual pump absorption along the length of the fiber due to the presence of the second pump diode without an internal or external wavelength stabilizing mechanism.
[0030] Further, the system allows control over pump absorption due to the presence of the second pump diode without internal or external wavelength stabilizing mechanism through temperature control using the external cooling unit. The system allows thermal management of kilowatt-class lasers by controlling the power ON sequence of the first pump diode and second pump diode through the one or more external electrical power supplies. The system reduces thermal load of unabsorbed pump for kilowatt-class laser power, if electrical power ON is in the sequence of the second pump diode without internal or external wavelength stabilizing mechanism, followed by the first pump diode. This pumping method is valid for pumping configurations such as co-propogation, counter-propogation, bi-directional pumping and side-pumping.
[0031] The expression "active fiber" in the instant disclosure refers to any fiber with doped ions capable of lasing for light amplification, irrespective of its fiber dimensions.
[0032] The expression "pump diodes" in the instant disclosure refers to any component that can provide optical power with appropriate wavelength that can be absorbed by the active fiber using any laser generation technique.
[0033] The expression "pump combiner" in the instant disclosure refers to any component that can combine pump power from different pump diodes along with seed laser power (if present) using any power-combining technique.
[0034] The expression "pumpdump" in the instant disclosure refers to any method for dumping the unabsorbed pump after passing through the active fiber. This can also be referred as ‘cladding mode stripper (CMS)’ in the art.
[0035] The expression "cooling system" in the instant disclosure refers to any method for providing heat dissipation and thermal management for pump diodes. This can also be referred as ‘coolant’ in the art.
[0036] The expression "electric supply" in the instant disclosure refers to any method for providing the required electrical power for the pump diodes.
[0037] The advantages achieved by the system of the present disclosure can be clear from the embodiments provided herein. The system uses pump diodes of with and without wavelength stabilization techniques controlled by an external electrical supply and working at a controlled temperature maintained by the cooling system which is further combined through the pump combiner. The active fiber for the kilo-watt class fiber laser or amplifier when pumped with this method, has an optimized pump absorption leading to efficient lasing and thermal management, circumventing the power-limiting factors of thermal mode instabilities, nonlinearities and pumpdump temperatures. The description of terms and features related to the present disclosure shall be clear from the embodiments that are illustrated and described; however, the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents of the embodiments are possible within the scope of the present disclosure. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect to the following description.
[0038] FIG. 1 is an illustration showing the schematic block diagram of typical fiber laser setup, in accordance with an embodiment of the present disclosure.
[0039] Referring to FIG. 1, fiber laser system 100 is disclosed. The fiber laser system 100 can include pumping section 102, laser cavity 104, pump dump 110, cladding mode stripper (CMS) 112 and delivery fiber 114. The pumping section 102 supplies the energy, the laser cavity 102 amplifies the light using an active fiber 108 and fiber brag grating mirrors106, the pump dump 110 eliminates excess pump power, the cladding mode stripper 112 removes unwanted cladding modes, and the delivery fiber 114 transmits the generated laser power to the desired location.
[0040] The pumping section 102 is responsible for supplying the energy required to stimulate the gain medium and initiate the laser action. It typically includes one or more pump diodes or laser diodes that emit high-power optical pump signals. These pump signals are coupled into the gain fiber to excite the active ions present in the fiber. The laser cavity 104 is the core part of the fiber laser system where the lasing action occurs. It consists of several components such as active fiber or gain fiber 108 and fiber brag grating mirrors 106.
[0041] Active fiber or gain fiber 108: This is the main component of the laser cavity and is made of a specialty optical fiber doped with rare earth ions such as erbium, ytterbium, or neodymium that can amplify light signals. The active ions in the fiber are excited by the pump signals from the pumping section, leading to the emission of stimulated photons.
[0042] Fiber bragg grating mirrors 106: The mirrors are used to form an optical resonator within the laser cavity. They are typically created by fabricating fiber Bragg gratings, which are periodic variations in the refractive index of the fiber core. These gratings reflect specific wavelengths of light and allow the formation of a standing wave within the cavity, enabling the amplification of the desired laser wavelength.
[0043] The pump dump 110 is designed to eliminate or redirect the unabsorbed optical pump power that is not utilized for laser amplification. It can be a separate element or integrated into the laser system. The pump dump absorbs or redirects the excess pump power to prevent it from interfering with the laser operation or causing any damage.
[0044] In some fiber laser systems, the pump light that propagates in the cladding of the gain fiber can interfere with the laser performance or cause unwanted effects. The cladding mode stripper 112 is used to remove or suppress these cladding modes by selectively stripping the unwanted light from the cladding and allowing only the desired laser light to propagate. When the laser power is generated and amplified within the laser cavity 104, it needs to be delivered to the desired location for applications or further processing. The delivery fiber 114 serves this purpose by acting as a waveguide to transmit the laser output from the laser cavity 104 to the output port or delivery point of the fiber laser system.
[0045] FIG. 2 is an illustration showing the schematic block diagram of a typical fiber amplifier setup, in accordance with an embodiment of the present disclosure.
[0046] Referring to FIG.2, the fiber amplifier system 200 can include pumping section 202, input from the seed stage 204, amplifier stage 206, pump dump 210, cladding mode stripper (CMS) 212 and delivery fiber 214. The pumping section 202 supplies the energy, the seed stage provides the initial input signal, the amplifier stage 206 amplifies the signal using an active fiber, the pump dump 210 eliminates excess pump power, the cladding mode stripper 212 removes unwanted cladding modes, and the delivery fiber 214 transmits the amplified signal to the desired location.
[0047] The pumping section 202 is responsible for providing the energy required to amplify the optical signal. It typically includes high-power pump diodes or laser diodes that emit optical pump signals. These pump signals are coupled into the gain fiber of the amplifier stage to excite the active ions.
[0048] Input from the seed stage 204 provides the optical seed signal. It involves injecting a low-power optical seed signal into the amplifier system. The seed signal serves as the input signal that can be amplified in the subsequent amplifier stage.
[0049] The amplifier stage 206 is the core component of the fiber amplifier system where the signal amplification occurs. It consists of the following:
[0050] a. Active fiber or gain fiber 208: This is the main component of the amplifier stage and is made of a specialty optical fiber doped with rare earth ions such as erbium, ytterbium, or neodymium that can amplify light signals. The active ions in the fiber are excited by the pump signals from the pumping section, leading to the amplification of the injected seed signal.
[0051] Similar to the previous system, the pump dump 210 in the fiber amplifier system is designed to eliminate or redirect the unabsorbed optical pump power that is not utilized for signal amplification. It prevents the excess pump power from interfering with the amplification process or causing any damage.
[0052] Further, the cladding mode stripper (CMS) 212 in the fiber amplifier system serves the same purpose as described in the previous system. It removes or suppresses unwanted cladding modes and ensures that only the desired signal and amplified light propagate through the system. Once the signal has been amplified in the amplifier stage, it needs to be delivered to the desired location or further processing. The delivery fiber 214 acts as a waveguide to transmit the amplified signal from the amplifier stage to the output port or delivery point of the fiber amplifier system.
[0053] FIG. 3 is an illustration showing a block diagram of a part of the system and method disclosed in this invention for pumping, in accordance with an embodiment of the present disclosure. The system and method for pumping kilowatt class fiber lasers and amplifiers disclosed in this invention is illustrated in FIG.3. The pumping section 300 can include a cooling system 302 along with a conductive plate to improve heat dissipation, internal/external wavelength stabilized pump diode 304-1, pump diode 304-2 without internal/external wavelength stabilization, along with separate electric power supplies (306-1, 306-2) for pump diodes (304-1, 304-2) respectively. The pump power along with the seed laser power (if present) is combined by a pump combiner 308 (also referred to as fiber fused combiner, 308) and is fed into the doped fiber through the output port of the pump combiner 308. The doped fiber is either part of a fiber laser or a fiber amplifier system. The cooling system 302 is responsible for cooling the system and improving heat dissipation. It helps maintain the desired temperature for efficient operation of the pump diodes and the overall system. The conductive plate works in conjunction with the cooling system to enhance heat dissipation. It helps spread and dissipate heat more effectively, preventing overheating and ensuring the system operates within optimal temperature ranges.
[0054] The internal/external wavelength stabilized pump diode 304-1 is designed to provide stable and controlled wavelengths of light for pumping the doped fiber. It ensures consistent absorption of pump power by the fiber and reduces the amount of unabsorbed pump power that needs to be dissipated as heat. The pump diode 304-2 without internal/external wavelength stabilization operates without internal or external mechanisms to stabilize its wavelength. The wavelength of the emitted light varies with the driving current. It produces a higher load on the pumpdump and requires careful thermal management.
[0055] Separate electric power supplies (306-1 and 306-2) are used to independently control and provide electric power to the pump diodes (304-1 and 304-2) respectively. By having separate power supplies, the system can control and manage the power ON sequence to reduce heat load on the pumpdump and optimize thermal management.
[0056] The pump combiner 308 combines the pump power from the pump diodes (304-1, 304-2) with the seed laser power (if present). It ensures the combined power is coupled into the doped fiber, which can be part of a fiber laser system or a fiber amplifier system. The doped fiber is the fiber medium that is doped with specific materials to enable laser amplification or lasing action. It receives the combined power from the pump combiner and generates the desired laser output or amplifies an existing laser signal.
[0057] With the arrangement of the system and method disclosed, the thermal mode instability threshold, nonlinearity threshold, and reduction of heat load on the pumpdump can be effectively improved. Fine control of the pump absorption can be obtained by varying the temperature set by the cooling system 302. Variation of ambient temperature varies the pump wavelength, affecting the unabsorbed pump power and heat load at the pumpdump. Controlling the temperature of pumpdump is crucial for thermal management of high power fiber lasers. If not successfully controlled, this temperature might turn out to be the limiting factor for power scaling.
[0058] To better manage the temperature of the pumpdump, separate power supplies 306-1 and 306-2 are used for pump diodes (304-1, 304-2). The power ON sequence is designed to reduce the heat load on pumpdump for all power levels. Firstly, the power supply 306-2, for pump diode without internal/external wavelength stabilization 304-2, is powered ON. For this diode, the wavelength changes with increase in driving current. Thus, the pumpdump load also varies with current. Moreover, the pumpdump load is more in the case of pump diode 304-2 compared to pump diode 304-1. At the maximum power of the pump diode 304-2, the pumpdump temperature is stabilized. Subsequently, the wavelength stabilized pump diode 304-1 is powered ON. Due to wavelength stabilized nature of the pump diode 304-1, less unabsorbed pump power needs to be dissipated at pumpdump. Also, the proportion of unabsorbed pump is similar for all driving currents. This powering ON sequence for power supply (306-1, 306-2) allows better thermal management for kilowatt class fiber lasers and amplifiers.
[0059] The pumping method uses pump diodes of varying wavelength stability, controlled by external electrical supply and working at a controlled temperature maintained by the cooling system which is further combined through the pump combiner. The active fiber for the kilo-watt class fiber laser or amplifier when pumped with this method, has an optimized pump absorption leading to efficient lasing and thermal management, circumventing the power-limiting factors of thermal mode instabilities, nonlinearities and pumpdump temperatures.
[0060] FIG. 4 is an illustration showing a block diagram of a part of the system and method disclosed in this invention for pumping, in accordance with an embodiment of the present disclosure. The system and method for pumping kilowatt class fiber lasers and amplifiers disclosed in FIG.4. The cooling system 402 maintains temperature control, the conductive plate aids in heat dissipation, the wavelength-stabilized pump diodes 404-1 and additional pump diodes 404-2 without wavelength stabilization provide pump power, separate power supplies (406-1 and 406-2) drive the respective pump diodes, the pump combiner 408 combines the pump and seed laser power, and the combined power is fed into the doped fiber for amplification in the fiber laser or amplifier system.
[0061] The cooling system 402 is responsible for managing the temperature of the system and dissipating heat generated during operation. The cooling system ensures that the components, especially the pump diodes, operate within their optimal temperature range to maintain performance and reliability. The conductive plate is used to enhance heat dissipation within the system. It helps in spreading and dissipating heat more effectively, improving thermal management and preventing overheating of critical components.
[0062] Internal/external wavelength stabilized pump diodes 404-1 are high-power pump diodes that emit optical pump signals at specific wavelengths. They are designed to have wavelength stabilization mechanisms, either internally or externally, to ensure consistent and precise pump wavelengths. The number of pump diodes denoted as 'n' can be determined based on the system thermal and optical output power optimizations of the fiber laser or amplifier system.
[0063] Pump diodes without internal/external wavelength stabilization 404-2 are additional pump diodes that do not have wavelength stabilization mechanisms. They are used to provide supplementary pump power to the system. The number of pump diodes denoted as 'm' can be adjusted based on system optimization.
[0064] Separate electric power supplies 406-1 and 406-2 are dedicated to driving the corresponding pump diodes. Power supply 406-1 is specifically connected to the internal/external wavelength stabilized pump diodes 404-1, while power supply 406-2 is connected to the pump diodes 404-2 without wavelength stabilization. By having separate power supplies, fine control over the pump absorption and thermal management can be achieved.
[0065] The pump combiner 408 is responsible for combining the pump power from the different pump diodes (404-1, 404-2) with the seed laser power (if present). It ensures efficient power coupling and delivery into the doped fiber of the fiber laser or amplifier system. The combined power is then fed into the doped fiber through the output port of the pump combiner. The combined pump power, along with the seed laser power if applicable, is injected into the doped fiber to stimulate the amplification process.
[0066] The pumping section 400 consists of a cooling system 402 along with a conductive plate to improve heat dissipation, multiple internal/external wavelength stabilized pump diodes 404-1, multiple pump diodes without internal/external wavelength stabilization 404-2, along with separate electric power supplies 406-1 and 406-2 for pump diodes 404-1 and 404-2 respectively. The figure denotes ‘n’ 404-1 pump diodes and ‘m’ 404-2 pump diodes in the system. The ration of n:m can be decided according to corresponding the fiber laser or fiber amplifier system optimization. The pump power along with the seed laser power (if present) is combined by the pump combiner 408 and is fed into the doped fiber through the output port of the pump combiner 408. The doped fiber can be part of a fiber laser system or a fiber amplifier system. Fine control on the pump absorption can be obtained through varying the temperature set by the cooling system 402. To better manage the temperature of pumpdump, separate power supplies 406-1 and 406-2 are used for pump diodes, 404-1and 404-2. Firstly, the pump diodes 404-1 should be powered ON followed by pump diodes 404-2. This powering ON sequence for 404-1 and 404-2 allows better thermal management for kilowatt class fiber lasers and amplifiers.
[0067] FIG. 5 illustrates an exemplary flow chart of a method for pumping a fiber laser or fiber amplifier stage, in accordance with an embodiment of the present disclosure.
[0068] The method 500 includes at block 502, the external cooling unit is configured for controlling the operating temperature of the first pump diode and second pump diode. At block 504, one or more external electrical power is coupled to corresponding pump diodes to provide the required current and voltage control for the first pump diode and second pump diode. At block 506, the hybrid combination of pump diodes that emits laser power with appropriate wavelength, the hybrid combination of pump diodes includes first pump diode that operates using an internal or external wavelength stabilizing mechanism and a second pump diode that operates without internal or external stabilizing mechanism.
[0069] At block 508, the fiber fused combiner combines the powers of the first pump diode and second pump diode, the combined power is fed into the doped fiber for amplification in the fiber laser or amplifier system.
[0070] Thus, the present invention overcomes the drawbacks, shortcomings, and limitations associated with existing solutions, and provides a system and method which direct use of off-the-shelf components for pumping can result in better thermal management and mitigation of power-limiting factors. The system and method disclosed in this invention allow extra control of pump absorption through temperature variations. Further, the system and method disclosed in this invention allow control of heat load on pumpdump/cladding mode stripper (CMS) through unique powering ON sequence. Hence, the system and method disclosed here offer simple and more efficient way for pumping kW-class fiber lasers and amplifiers.
[0071] It will be apparent to those skilled in the art that the system of the disclosure may be provided using some or all of the mentioned features and components without departing from the scope of the present disclosure. While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure 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 disclosure, as described in the claims.

ADVANTAGES OF THE PRESENT INVENTION
[0072] The present invention provides a system that provides simplified implementation using off-the-shelf components.
[0073] The present disclosure provides optimized pump absorption that maximizes the conversion of input pump power into laser output power, ensuring high efficiency in kilo-watt class fiber lasers or amplifiers.
[0074] The present disclosure addresses thermal mode instabilities, nonlinearities, and pumpdump temperatures improves power handling capabilities and enhances operational stability.
[0075] The present disclosure provides pump diodes with varying wavelength stability to enable precise control over the pump wavelength, ensuring optimal energy transfer and consistent performance.
[0076] The present disclosure provides an external electrical supply that offers fine-grained control over pump diodes, allowing for precise adjustment of pump power and optimization of the laser or amplifier performance.
[0077] The present disclosure provides the pumping method that is suitable for kilo-watt class fiber lasers or amplifiers, making it applicable for systems with higher power requirements, thus supporting future power scaling needs.
[0078] The present disclosure provides optimized pump absorption and improved thermal management to reduce power losses, resulting in lower power consumption and potentially extended component lifetimes, leading to cost savings.
, Claims:
1. A system (300) for pumping a fiber laser or fiber amplifier stage, the system comprising:
a hybrid combination of pump diodes emits laser power with appropriate wavelength, the hybrid combination of pump diodes comprising:
a first pump diode (304-1) that operates using internal or external wavelength stabilizing mechanism;
a second pump diode (304-2) that operates without internal or external stabilizing mechanism;
a fiber fused combiner (308) to combine the powers of the first pump diode and second pump diode, the combined power is fed into a doped fiber for amplification in the fiber laser or amplifier stage;
an external cooling unit (302) configured for controlling the operating temperature of the first pump diode and the second pump diode; and
one or more external electrical power supplies (306-1, 306-2) coupled to corresponding pump diodes to provide the required current and voltage control for the first pump diode and the second pump diode.
2. The system as claimed in claim 1, wherein the system suppresses nonlinearity threshold by optimizing gain fiber length through improved optical amplification efficiency due to presence of the first pump diode, wherein the first pump diode is wavelength-stabilized pump diode.
3. The system as claimed in claim 1, wherein the system enhances thermal management by reducing residual unabsorbed pump after the gain fiber due to presence of the first pump diode.
4. The system as claimed in claim 1, wherein the system suppresses modal instabilities caused by thermal effects through gradual pump absorption along the length of the fiber due to presence of the second pump diode without internal or external wavelength stabilizing mechanism.
5. The system as claimed in claim 1, wherein the system allows control over pump absorption due to presence of the second pump diode without internal or external wavelength stabilizing mechanism through temperature control using the external cooling unit.
6. The system as claimed in claim 1, wherein the system allows thermal management of kilowatt-class lasers by controlling the power ON sequence of the first pump diode and second pump diode through the one or more external electrical power supplies.
7. The system as claimed in claim 7, wherein the system reduces thermal load of unabsorbed pump for kilowatt-class laser power, if electrical power ON is in the sequence of the second pump diode without internal or external wavelength stabilizing mechanism, followed by the first pump diode.
8. The system as claimed in claim 1, wherein the pumping method is valid for all pumping configurations that comprises co-propagation, counter-propagation, bi-directional pumping and side pumping.
9. A method (500) for pumping a fiber laser or fiber amplifier stage, the method comprising:
controlling (502), by an external cooling unit, the operating temperature of the first pump diode and second pump diode;
supplying (504), by one or more external electrical power, the required current and voltage control for the first pump diode and second pump diode, the one or more external electrical power supplies coupled to corresponding pump diodes;
emitting (506), by a hybrid combination of pump diodes, laser power with appropriate wavelength, the hybrid combination of pump diodes comprising:
a first pump diode (304-1) that operates using internal or external wavelength stabilizing mechanism;
 
a second pump diode (304-2) that operates without internal or external stabilizing mechanism; and
combining (508), by a fiber fused combiner, the powers of the first pump diode and the second pump diode, the combined power is fed into the doped fiber for amplification in the fiber laser or amplifier stage.