A high-power ultra-wideband wavelength scanning fiber laser system and tuning method

Abstract

The present invention provides a high-power ultra-wideband wavelength scanning fiber laser system, which includes a wavelength tunable seed source, a wavelength tunable pump source array, a pump signal combiner, a Raman gain fiber and a fiber end cap: the wavelength tunable seed source is connected to the signal input arm of the pump signal combiner; the wavelength tunable pump source array is respectively connected to each pump input arm of the pump signal combiner; the output end of the pump signal combiner is connected to one end of the Raman gain fiber, and the other end of the Raman gain fiber is connected to the fiber end cap; the wavelength scanning range of the high-power ultra-wideband wavelength scanning fiber laser system is greater than 900 nanometers, and the typical value is 1050 nanometers to 2000 nanometers; the continuous light output within the wavelength scanning range is greater than 1 kilowatt. The present invention uses a wavelength tunable pump source and a seed source at the same time, and uses an amplifier to amplify the seed source until a tunable cascade Raman light is generated, so as to achieve an ultra-wide tuning range and amplify the power calibration at the same time.

Description

Technical Field

[0001] The present invention generally belongs to the technical field of optical fiber lasers, and in particular relates to a high-power ultra-wideband wavelength scanning optical fiber laser system and a tuning method. Background Art

[0002] High-power fiber lasers have been widely used in many important fields such as scientific research, national defense, medical treatment, and industry. The essence of laser application is actually the process of interaction between laser and matter, and different application fields require different laser wavelengths due to different acting substances. However, due to limited gain bandwidth, its emission wavelength is often fixed at a specific wavelength, and the 3dB bandwidth corresponding to several kilowatts is often less than ten nanometers. With the rapid expansion of the application range of high-power lasers, conventional single wavelengths often cannot match the wavelength corresponding to the best effect. In order to obtain the best effect, not only the laser output power needs to reach the kilowatt level, but also the laser wavelength needs to be able to switch continuously in a wide spectral range to match the optimal wavelength of different acting substances. Therefore, in the face of such applications, high-power fiber lasers with ultra-wideband wavelength scanning functions are conducive to the realization of a high degree of integration of multiple high-power fiber laser systems, which can greatly simplify the laser system, save costs, and improve efficiency.

[0003] However, the conventional 1-micron-band kilowatt-level fiber laser source has a tuning range of only 30-40 nanometers due to the narrow gain range of rare earth ions, which is far from meeting the needs of practical applications. At present, ultra-wide spectral range lasers are mainly achieved through nonlinear effects. According to different nonlinear effects, they are generally divided into two categories. One is a random fiber laser based only on cascade stimulated Raman scattering, which is pumped by a conventional 1-micron-band tunable fiber laser and has achieved continuous adjustment in the 1.1-1.9 micron spectral range, but the maximum power is only in the tens of watts. The other is a supercontinuum light source based on multiple nonlinear effects, whose output spectral bandwidth can reach more than 2.4 microns and the power can reach the kilowatt level. However, its spectral density is low, and the power of a specific wavelength is even less than ten watts. Therefore, there is currently no high-power fiber laser system that can simultaneously cover the 1-2 micron ultra-wideband wavelength scanning function. Summary of the invention

[0004] In order to expand the spectral range of existing kilowatt-level tunable lasers and realize kilowatt-level laser output with ultra-wide wavelength scanning function, the present invention provides a high-power ultra-wideband wavelength scanning fiber laser system and tuning method. The wavelength scanning range of the system covers 1-2 microns, and the continuous laser output power of a single wavelength is greater than 1 kilowatt.

[0005] To achieve the above technical purpose, the technical solution of the present invention is: a high-power ultra-wideband wavelength scanning fiber laser system, which includes a wavelength tunable seed source, a wavelength tunable pump source array, a pump signal combiner, a Raman gain fiber and a fiber end cap: the wavelength tunable seed source is connected to the signal input arm of the pump signal combiner; the wavelength tunable pump source array is respectively connected to each pump input arm of the pump signal combiner; the output end of the pump signal combiner is connected to one end of the Raman gain fiber, and the other end of the Raman gain fiber is connected to the fiber end cap; the wavelength scanning range of the high-power ultra-wideband wavelength scanning fiber laser system is greater than 900 nanometers, and the typical value is 1050 nanometers to 2000 nanometers; the continuous light output of any wavelength within the wavelength scanning range is greater than 1 kilowatt.

[0006] The high-power ultra-wideband wavelength scanning fiber laser system of the present invention also includes an isolator, which is arranged between the wavelength tunable seed source and the signal input arm of the pump signal combiner, and between the wavelength tunable pump source array and each pump input arm of the pump signal combiner. The isolator is used to prevent the influence of backward return light and protect the wavelength tunable seed source and the wavelength tunable pump source array.

[0007] Furthermore, the connection of the wavelength tunable seed source, the wavelength tunable pump source array, the pump signal combiner, and the Raman gain fiber forms a cascade amplifier structure; the high-power ultra-wideband wavelength scanning fiber laser system includes more than one group of cascade amplifier structures, which are connected in series in sequence and finally connected to the end caps. The more than one group refers to two groups or more than two groups.

[0008] Furthermore, the wavelength tuning range of the wavelength tunable pump source array is greater than 40 nanometers, and the central wavelength is in the range of 0.9 to 1.1 micrometers, for example, the tuning range is from 1020 nanometers to 1060 nanometers, or the tuning range is from 1060 nanometers to 1100 nanometers.

[0009] Furthermore, the wavelength tunable seed source is a Raman fiber laser or a random fiber laser pumped by a wavelength tunable ytterbium-doped fiber laser, and its wavelength range is within the first-order Raman optical gain spectrum corresponding to the wavelength tunable pump source array, for example, a frequency shift of 13.2 THz, corresponding to the maximum Raman gain coefficient of the quartz Raman gain fiber; the tuning range of the wavelength tuning seed source is greater than 60 nanometers, for example, the tuning range is from 1060 nanometers to 1120 nanometers, or the tuning range is from 1120 nanometers to 1180 nanometers.

[0010] Furthermore, the Raman gain fiber is a large mode field double-clad fiber structure or a graded refractive index fiber structure to achieve high brightness cascade Raman light output.

[0011] Furthermore, the length of the Raman gain fiber is optimized based on the following design factors: the first-order Raman light threshold of the tunable pump source array is calculated based on the specific fiber structure parameters, pump, and seed center wavelengths, so that it is equal to or greater than 1 kilowatt when the wavelength tunable seed source is turned off, and the highest-order cascade Raman light power corresponding to the longest wavelength in the scanning range is equal to or slightly greater than 1 kilowatt when the wavelength tunable seed source is turned on.

[0012] Furthermore, the zero dispersion wavelength of the Raman gain optical fiber is outside the wavelength scanning range.

[0013] Furthermore, the transmission loss and bending loss of the Raman gain optical fiber within the wavelength scanning range are much smaller than the corresponding Raman gain.

[0014] The present invention also provides a high-power ultra-wideband power calibration and amplification method, which uses the above-mentioned high-power ultra-wideband wavelength scanning fiber laser system, and respectively realizes the generation and amplification of high-power lasers in different sub-bands within the ultra-wideband wavelength range through the following steps S1-S3: S1, keeping the wavelength tunable seed source closed, starting the wavelength tunable pump source array to emit pump light into the pump signal combiner for beam combining, at this time, the Raman gain fiber is only used as an energy transmission fiber to directly output the combined pump light, the pump power is lower than the first-order Raman light threshold, and high-power laser output within the pump tuning range is realized; S2, first starting the wavelength tunable seed source to emit seed laser, and then starting the wavelength tunable pump source array to emit pump light, which enters the Raman gain fiber after beam combining by the pump signal combiner, and increases the pump power to the first-order Raman light threshold, so as to realize power calibration and amplification of the wavelength tunable seed source; S3, on the basis of step S2, continuing to increase the pump power until a higher-order cascaded Raman light with a longer wavelength is generated and amplified, so as to realize continuous expansion of the high-power laser output wavelength.

[0015] The present invention also provides a wavelength matching method for a high-power wavelength tunable pump and a seed source, which uses the above-mentioned high-power ultra-wideband wavelength scanning fiber laser system and is operated as follows: first, the tunable seed source is turned on, the seed output center wavelength is adjusted, and then the wavelength tunable pump source array is started to emit pump light, which enters the Raman gain fiber after being combined by a pump signal combiner. When the pump power is lower than the first-order Raman light threshold, the pump center wavelength is adjusted so that the seed wavelength is equal to the wavelength of the pump Raman peak gain, and then the power is continued to be increased to be greater than the first-order Raman light threshold, so as to achieve wavelength matching between the tunable pump and the seed source and maximize the Raman gain.

[0016] The present invention also provides a high-power ultra-wideband wavelength continuous scanning method, which uses the above-mentioned high-power ultra-wideband wavelength scanning fiber laser system to respectively realize wavelength scanning and power amplification of different bands through the following steps S1-S3: S1, short-wave pump light scanning: keep the wavelength tunable seed source closed, start the wavelength tunable pump source array to emit pump light, enter the pump signal combiner for beam combining, at this time, the Raman gain fiber is only used as an energy transmission fiber to directly output the combined pump light, the pump power is lower than the first-order Raman light threshold, and the wavelength scanning within the pump tuning range is realized; S2, conventional band scanning and power amplification: start the wavelength tunable seed source to emit seed laser, then start the wavelength tunable pump source array to emit pump light, and the pump signal combiner combines the pump light. beam and then enter the Raman gain fiber; when scanning the wavelength, first adjust the seed wavelength, and then adjust the pump center wavelength when the pump power is lower than the first-order Raman light threshold so that the seed wavelength is equal to the wavelength of the pump Raman peak gain, so as to achieve wavelength matching between the tunable pump and the seed source; then continue to increase the pump power to be greater than the first-order Raman light threshold, so as to achieve wavelength scanning and power amplification within the seed tuning range; S3, long-wave and ultra-long-wave band scanning and power amplification: on the basis of step S2, calculate the corresponding seed and pump wavelengths according to the target wavelength, and then adjust the seed and pump wavelengths to the wavelength in turn when the pump power is lower than the first-order Raman light threshold; then continue to increase the pump power until the secondary and cascade Raman light are generated and amplified, so as to achieve wavelength scanning and power amplification within the long-wave and ultra-long-wave band range.

[0017] It can be seen that the short-wave part of ultra-wide spectrum tuning is realized by controlling the pump power to be lower than the first-order Raman light threshold when only the wavelength tunable pump source array emits light, and the amplifier directly outputs the pump laser. The conventional band part of ultra-wide spectrum tuning is realized by increasing the output power of the wavelength tunable pump source array to the first-order Raman light threshold when the wavelength tunable seed source emits light, and by adjusting the wavelength tunable pump source array and the wavelength tunable seed source wavelength, the two are matched to obtain the highest Raman gain, thereby realizing the power amplification of the wavelength tunable seed source. The long-wave part of ultra-wide spectrum tuning is realized by further increasing the output power of the wavelength tunable pump source array on the basis of maintaining the wavelength tunable seed source output, so that the seed light power reaches the second-order Raman light threshold, and by adjusting the wavelength tunable pump array and the wavelength tunable seed source wavelength, the corresponding second-order Raman wavelength is tuned and the power amplification is realized. The ultra-long-wave portion of ultra-wide spectrum tuning is achieved by gradually increasing the output power of the wavelength-tunable pump source array while maintaining the wavelength-tunable seed source output, gradually generating and amplifying higher Raman orders, adjusting the wavelength-tunable pump array and the wavelength-tunable seed source wavelength, and achieving tuning of higher-order Raman to longer wavelengths. So far, the cascaded Raman fiber amplifier system can ensure the simultaneous realization of ultra-wide tuning range and single-wavelength high-power output.

[0018] The advancement of the present invention lies in: using wavelength tunable pump source and seed source at the same time, using amplifier structure to amplify the seed source until tunable cascade Raman light is generated, achieving ultra-wide tuning range and being able to calibrate and amplify power at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] These and / or other aspects and advantages of the present invention will become more clear and easier to understand from the following detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0020] Figure 1 The present invention is a schematic structural diagram of a high-power ultra-wideband wavelength scanning fiber laser system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0022] Example 1

[0023] A high-power ultra-wideband wavelength scanning fiber laser system, the structure of which is as follows Figure 1 As shown, it includes a wavelength tunable seed source, a wavelength tunable pump source array, a pump signal combiner, a Raman gain fiber and a fiber end cap. In terms of the overall structure, the wavelength tunable seed source is connected to the signal input arm of the pump signal combiner; the wavelength tunable pump source array is respectively connected to each pump input arm of the pump signal combiner; the output end of the pump signal combiner is connected to one end of the Raman gain fiber, and the other end of the Raman gain fiber is connected to the fiber end cap; wherein an isolator is further arranged between the wavelength tunable seed source and the signal input arm of the pump signal combiner and between the wavelength tunable pump source array and each pump input arm of the pump signal combiner, so as to prevent the influence of backward return light and protect the wavelength tunable seed source and the wavelength tunable pump source array.

[0024] More specifically, the parameters and performance of each component are as follows: the wavelength tuning range of the wavelength tunable pump source array is greater than 40 nanometers, the central wavelength is in the range of 0.9 to 1.1 microns, and the first-order Raman light threshold is equal to or greater than 1 kilowatt when the wavelength tunable seed source is turned off. The wavelength tunable seed source is a Raman fiber laser or a random fiber laser pumped by a tunable ytterbium-doped fiber laser, and its wavelength range is within the first-order Raman light gain spectrum corresponding to the tunable pump source array, and the tuning range of the tunable seed source is greater than 60 nanometers; the Raman gain fiber is a large mode field double-clad fiber structure or a gradient refractive index fiber structure, and its zero dispersion wavelength is outside the wavelength scanning range, and the transmission loss and bending loss within the wavelength scanning range are much smaller than the corresponding Raman gain.

[0025] The wavelength scanning range of the high-power ultra-wideband wavelength scanning fiber laser system is greater than 900 nanometers, with a typical value of 1050 nanometers to 2000 nanometers; the continuous light output within the wavelength scanning range is greater than 1 kilowatt.

[0026] Example 2

[0027] A high-power ultra-wideband wavelength scanning fiber laser system includes multiple groups of wavelength tunable seed sources, wavelength tunable pump source arrays, pump signal combiners, and Raman gain fibers. The connection relationship of each group of wavelength tunable seed sources, wavelength tunable pump source arrays, pump signal combiners, and Raman gain fibers is the same as that in Example 1, except that the multiple groups are connected in series in sequence and the rear ends are then connected to end caps; of course, an isolator with the same connection method and function as in Example 1 is also preferably included.

[0028] The above-mentioned multiple groups refer to more than one group, typically including two groups, or more than two groups.

[0029] The high-power ultra-wideband wavelength scanning fiber laser system of this embodiment can obtain higher power output compared with the first embodiment.

[0030] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be subject to the scope of protection of the claims.

Claims

1. A high-power ultra-wideband wavelength continuous scanning method, characterized in that: It uses a high-power ultra-wideband wavelength scanning fiber laser system, which includes a wavelength tunable seed source, a wavelength tunable pump source array, a pump signal combiner, a Raman gain fiber and a fiber end cap: The wavelength tunable seed source is connected to the signal input arm of the pump signal combiner; The wavelength tunable pump source array is respectively connected to each pump input arm of the pump signal combiner; The output end of the pump signal combiner is connected to one end of the Raman gain fiber, and the other end of the Raman gain fiber is connected to the fiber end cap; The wavelength scanning range of the high-power ultra-wideband wavelength scanning fiber laser system is greater than 900 nanometers, with a typical value of 1050 nanometers to 2000 nanometers; the continuous light output of any wavelength within the wavelength scanning range is greater than 1 kilowatt; The method implements wavelength scanning and power amplification of different bands respectively through the following steps S1-S3: S1, short-wave pump light scanning: keep the wavelength tunable seed source closed, start the wavelength tunable pump source array to send pump light into the pump signal combiner for beam combining, at this time, the Raman gain fiber is only used as an energy transmission fiber to directly output the combined pump light, the pump power is lower than the first-order Raman light threshold, and the wavelength scanning within the pump tuning range is realized; S2, conventional band scanning and power amplification: start the wavelength tunable seed source to emit seed laser, then start the wavelength tunable pump source array to emit pump light, which enters the Raman gain fiber after being combined by the pump signal combiner; when scanning the wavelength, first adjust the seed wavelength, and then adjust the pump center wavelength when the pump power is lower than the first-order Raman light threshold so that the seed wavelength is equal to the wavelength of the pump Raman peak gain, so as to achieve wavelength matching between the tunable pump and the seed source; then continue to increase the pump power to be greater than the first-order Raman light threshold, so as to achieve wavelength scanning and power amplification within the seed tuning range; S3, long-wave and ultra-long-wave band scanning and power amplification: Based on step S2, the corresponding seed and pump wavelengths are calculated according to the target wavelength, and then the seed and pump wavelengths are adjusted to the wavelengths in turn when the pump power is lower than the first-order Raman light threshold; then the pump power is continued to be increased until the secondary and cascade Raman light are generated and amplified, thereby realizing wavelength scanning and power amplification within the long-wave and ultra-long-wave band range.

2. The high-power ultra-wideband wavelength continuous scanning method according to claim 1, characterized in that: The high-power ultra-wideband wavelength scanning fiber laser system also includes an isolator, which is arranged between the wavelength tunable seed source and the signal input arm of the pump signal combiner, and between the wavelength tunable pump source array and each pump input arm of the pump signal combiner.

3. The high-power ultra-wideband wavelength continuous scanning method according to claim 1 or 2, characterized in that: The wavelength tunable seed source, wavelength tunable pump source array, pump signal combiner and Raman gain fiber of the high-power ultra-wideband wavelength scanning fiber laser system are connected to form a cascade amplifier structure; the high-power ultra-wideband wavelength scanning fiber laser system includes more than one group of cascade amplifier structures, which are connected in series in sequence and finally connected to end caps.

4. The high-power ultra-wideband wavelength continuous scanning method according to claim 1, characterized in that: The wavelength tuning range of the wavelength tunable pump source array of the high-power ultra-wideband wavelength scanning fiber laser system is greater than 40 nanometers, and the central wavelength is in the range of 0.9 to 1.1 micrometers.

5. The high-power ultra-wideband wavelength continuous scanning method according to claim 1, characterized in that: The wavelength tunable seed source of the high-power ultra-wideband wavelength scanning fiber laser system is a Raman fiber laser or a random fiber laser pumped by a wavelength tunable ytterbium-doped fiber laser, and its wavelength range is within the first-order Raman optical gain spectrum corresponding to the wavelength tunable pump source array, and the tuning range of the wavelength tunable seed source is greater than 60 nanometers.

6. The high-power ultra-wideband wavelength continuous scanning method according to claim 1, characterized in that: The Raman gain fiber of the high-power ultra-wideband wavelength scanning fiber laser system is a large-mode-field double-cladding fiber structure or a gradient refractive index fiber structure.

7. The high-power ultra-wideband wavelength continuous scanning method according to claim 1, characterized in that: The zero dispersion wavelength of the Raman gain fiber of the high-power ultra-wideband wavelength scanning fiber laser system is outside the wavelength scanning range.

8. The high-power ultra-wideband wavelength continuous scanning method according to claim 1, characterized in that: The transmission loss and bending loss of the Raman gain optical fiber of the high-power ultra-wideband wavelength scanning optical fiber laser system within the wavelength scanning range are much smaller than the corresponding Raman gain.

9. The high-power ultra-wideband wavelength continuous scanning method according to claim 1, characterized in that: The first-order Raman light threshold of the wavelength tunable pump source array of the high-power ultra-wideband wavelength scanning fiber laser system is equal to or greater than 1 kilowatt when the wavelength tunable seed source is turned off.

Images