Full polarization-maintaining ultra-flat ultra-wideband super-continuum spectrum laser based on noise-like pulse pumping

Abstract

The invention discloses a full polarization-maintaining ultra-flat ultra-wideband super-continuum spectrum laser based on noise-like pulse pumping, and the laser comprises a full polarization-maintaining noise-like pulse seed source which outputs 1.55 [mu] m noise-like square wave pulse; the two-stage polarization-maintaining ytterbium-erbium-doped optical fiber amplifier is used for outputting a spectrum of 1.5-2.3 microns; the polarization-maintaining high-nonlinearity optical fiber realizes 0.9-2.9 [mu] m flat type super-continuum source output; the polarization-maintaining large-mode-field ytterbium-erbium-doped optical fiber amplifier is used for amplifying the 1.55 [mu] m position of the super-continuum source; the polarization-maintaining large-mode-field ytterbium-doped optical fiber is used for amplifying the 1.06 mu m position of the super-continuum source; a mode field adapter for matching the mode fields of the optical fibers; the polarization-maintaining photonic crystal fiber expands the short wave to an ultraviolet band; the metafluotellurate is used for maintaining the long wave to be 4 microns; and the spectrum of the polarization-maintaining sulfide optical fiber is further expanded to 12 microns. According to the invention, a full polarization-maintaining structure is adopted, and a super-continuum spectrum with high quality, high stability and high coherence can be output.

Description

Technical Field

[0001] The invention relates to the field of supercontinuum fiber lasers, and in particular to a full polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping. Background Art

[0002] Supercontinuum fiber laser is a laser light source with ultra-wide spectrum coverage. It stimulates nonlinear effects such as Raman scattering, self-phase modulation, and four-wave mixing in nonlinear optical fibers through high peak power pulses, which greatly broadens the initial narrowband light into a broadband supercontinuum light with excellent characteristics such as high power, high coherence, and high brightness. Its wide spectrum characteristics in the mid-infrared band can cover a variety of molecular characteristic absorption peaks, so it is widely used in molecular spectral analysis, biomedical detection, high-resolution imaging, infrared countermeasures, and national defense monitoring.

[0003] With the development of commercial 1μm and 1.55μm ultrafast mode-locked pulse fiber lasers, photonic crystal fibers, and highly nonlinear fluoride fibers, existing research has amplified pulse lasers through MOPA, and then nonlinearly expanded through photonic crystal fibers or highly nonlinear fibers to produce supercontinuum spectra covering the ultraviolet or mid-infrared. However, the supercontinuum spectrum produced has a narrow spectral range and the spectrum has residual pump peaks, resulting in low flatness.

[0004] If the current technology is improved to cover the spectrum from ultraviolet to mid-infrared, making the spectrum flatter across the entire band without residual pump peaks and with higher coherence, this type of supercontinuum spectrum will have higher recognition accuracy and broader monitoring capabilities in molecular recognition and environmental monitoring applications. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a full polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping, comprising:

[0008] Full polarization-maintaining noise-like pulse seed source, outputting 1.55μm noise-like square wave pulses;

[0009] Two-stage polarization-maintaining erbium-doped fiber amplifier, outputting 1.5-2.3μm spectrum;

[0010] Polarization-maintaining high nonlinear optical fiber further broadens the spectrum and realizes 0.9-2.9μm flat supercontinuum source output;

[0011] Polarization-maintaining large-mode-field erbium-doped fiber amplifier to amplify the supercontinuum source at 1.55 μm;

[0012] Polarization-maintaining large-mode-field ytterbium-doped fiber amplifies the supercontinuum source at 1.06 μm;

[0013] Mode field adapter, to match the mode field of the optical fiber;

[0014] Polarization-maintaining photonic crystal fiber, which extends short waves to the ultraviolet band under the action of dispersion and nonlinear effects;

[0015] The polarization-maintaining fluorotellurite extends the long wave to 4 μm under the action of Raman soliton self-frequency shift;

[0016] The polarization-maintaining sulfide optical fiber further expands the spectrum to 12μm under the action of nonlinearity, achieving ultra-flat ultra-wideband supercontinuum laser output with wavelengths covering ultraviolet to mid-infrared.

[0017] Further, the fully polarization-maintaining noise-like pulse seed source comprises a nonlinear amplifying loop mirror, a unidirectional ring and a first polarization-maintaining coupler;

[0018] The nonlinear amplifying loop mirror comprises a first polarization-maintaining single-mode optical fiber, a double-clad polarization-maintaining erbium-doped optical fiber, a first LD pump of 976nm and a 976 / 1550 wavelength division multiplexer; the unidirectional loop comprises a second polarization-maintaining single-mode optical fiber, a second polarization-maintaining coupler and a first polarization-maintaining isolator;

[0019] The first LD pump is connected to the pump end of the wavelength division multiplexer, the common end of the wavelength division multiplexer is connected to the double-clad polarization-maintaining erbium-doped fiber, the first polarization-maintaining single-mode fiber, and the first coupling arm of the first polarization-maintaining coupler in sequence, and the signal end of the wavelength division multiplexer is connected to the second coupling arm of the first polarization-maintaining coupler; the common end of the first polarization-maintaining coupler is connected to the input end of the second polarization-maintaining coupler, the 40% port of the second polarization-maintaining coupler outputs a 1.55μm noise-like square wave pulse, and the 60% port of the second polarization-maintaining coupler is respectively connected to the first polarization-maintaining isolator, the second polarization-maintaining single-mode fiber, and the non-common end of the first polarization-maintaining coupler.

[0020] Furthermore, a third polarization-maintaining coupler is arranged between the full polarization-maintaining noise-like pulse seed source and the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier, the 1% port of the third polarization-maintaining coupler outputs a signal monitoring signal, the 99% port of the third polarization-maintaining coupler is connected to the full polarization-maintaining noise-like pulse seed source, and the common end of the third polarization-maintaining coupler is connected to the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier.

[0021] Further, the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier comprises a first-stage polarization-maintaining ytterbium-doped erbium fiber amplifier, a second-stage polarization-maintaining ytterbium-doped erbium fiber amplifier and a third polarization-maintaining single-mode optical fiber connected in sequence;

[0022] The first-stage polarization-maintaining erbium-doped fiber amplifier includes a second LD pump at 976 nm, a first pump combiner, and a first polarization-maintaining erbium-ytterbium co-doped double-clad fiber; the second-stage polarization-maintaining erbium-doped fiber amplifier includes a third LD pump at 976 nm, a second pump combiner, and a second polarization-maintaining erbium-ytterbium co-doped double-clad fiber;

[0023] The pump combining end of the first pump combiner is connected to the second LD pump, the pulse combining end of the first pump combiner is connected to the full polarization-maintaining noise-like pulse seed source, and the combining output end of the first pump combiner is connected to the first polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber; the pump combining end of the second pump combiner is connected to the third LD pump, the pulse combining end of the second pump combiner is connected to the first polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber, and the combining output end of the second pump combiner is respectively connected to the second polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber and the third polarization-maintaining single-mode optical fiber, and the third polarization-maintaining single-mode optical fiber outputs a 1.5-2.3 μm spectrum.

[0024] Furthermore, a second polarization-maintaining isolator is arranged between the full polarization-maintaining noise-like pulse seed source and the first pump combiner, a third polarization-maintaining isolator is arranged between the first polarization-maintaining erbium-ytterbium co-doped double-clad fiber and the second pump combiner, and a fourth polarization-maintaining isolator is arranged between the second polarization-maintaining erbium-ytterbium co-doped double-clad fiber and the third polarization-maintaining single-mode fiber.

[0025] Further, the polarization-maintaining large mode field erbium-doped fiber amplifier comprises a fourth LD pump of 976nm, a third pump combiner, and a polarization-maintaining large mode field erbium-doped fiber;

[0026] The pump combining end of the third pump combiner is connected to the fourth LD pump, the pulse combining end of the third pump combiner is connected to the two-stage polarization-maintaining erbium-doped fiber amplifier, and the combining output end of the third pump combiner is connected to the polarization-maintaining large mode field erbium-doped fiber.

[0027] Furthermore, the gain optical fibers in the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier and the polarization-maintaining large mode field ytterbium-doped erbium fiber amplifier are both placed on a water-cooled plate, and water is dripped at the melting point.

[0028] Furthermore, the output end of the polarization-maintaining sulfide optical fiber is cut at a bevel angle of 7 degrees.

[0029] The beneficial effects of the present invention are:

[0030] In an exemplary embodiment of the present invention, a fully polarization-maintaining structure is adopted to output a supercontinuum spectrum with high quality, high stability and high coherence; a noise-like pulse is used as a seed source to minimize residual pumping and greatly improve the flatness of the entire supercontinuum spectrum; at the same time, a seed source is used to achieve dual-wavelength pumping, and through a multi-stage cascade amplification structure and multi-stage nonlinear media, an ultra-flat ultra-wideband spectral output covering ultraviolet to mid-infrared can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic structural diagram of a fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping is provided in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that the directions or positional relationships indicated by "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are directions or positional relationships based on the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] See also Figure 1 , Figure 1 The structure diagram of a fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping is shown in an exemplary embodiment of the present invention, including the following components connected in sequence:

[0037] Full polarization-maintaining noise-like pulse seed source, outputting 1.55μm noise-like square wave pulses;

[0038] Two-stage polarization-maintaining erbium-doped fiber amplifier, outputting 1.5-2.3μm spectrum;

[0039] The polarization-maintaining high nonlinear fiber PM-HNLF further broadens the spectrum and achieves 0.9-2.9μm flat supercontinuum source output;

[0040] Polarization-maintaining large-mode-field erbium-doped fiber amplifier to amplify the supercontinuum source at 1.55 μm;

[0041] Polarization-maintaining large mode field ytterbium-doped fiber PLMA-YDF amplifies the supercontinuum source at 1.06μm;

[0042] Mode field adapter MFA, to match the mode field of the optical fiber;

[0043] Polarization-maintaining photonic crystal fiber PM-PCF, which extends short waves to the ultraviolet band under the action of dispersion and nonlinear effects;

[0044] The polarization-maintaining fluorotellurite PM-TBY extends the long wave to 4 μm under the action of Raman soliton self-frequency shift;

[0045] The polarization-maintaining sulfide fiber PM-As2S3 further expands its spectrum to 12μm under the action of nonlinearity, achieving ultra-flat ultra-wideband supercontinuum laser output with wavelengths covering ultraviolet to mid-infrared.

[0046] Specifically, in this exemplary embodiment, a fully polarization-maintaining noise-like pulse seed source outputs a 1.55 μm noise-like square wave pulse, and then a two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier (PM-EYDFs) is connected to the polarization-maintaining seed source to amplify and pre-broaden the seed light, and preliminarily achieve a 1.5-2.3 μm spectral output; a polarization-maintaining high nonlinear fiber PM-HNLF is connected to the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier to further broaden the spectrum and achieve a 0.9-2.9 μm flat supercontinuum output; a polarization-maintaining large mode field ytterbium-doped erbium fiber amplifier is connected to the polarization-maintaining high nonlinear fiber PM-HNLF to amplify the supercontinuum source at 1.55 μm; a polarization-maintaining large mode field ytterbium-doped fiber PLMA-YDF is connected to a polarization-maintaining large mode field ytterbium-doped The erbium fiber amplifier is connected to amplify the supercontinuum source at 1.06μm; the mode field adapter MFA is connected to the polarization-maintaining large mode field erbium-doped ytterbium fiber PLMA-YDF to match the mode field of the fiber, thereby reducing the loss and reflection caused by mode mismatch; the polarization-maintaining photonic crystal fiber PM-PCF is connected to the mode field adapter MFA to extend the short wave to the ultraviolet band under the action of dispersion and nonlinear effects; the polarization-maintaining fluorotellurite PM-TBY is connected to the polarization-maintaining photonic crystal fiber PM-PCF to extend the long wave to 4μm under the action of Raman soliton self-frequency shift; the polarization-maintaining sulfide fiber PM-As2S3 is connected to the polarization-maintaining fluorotellurite PM-TBY, and the spectrum can be further extended to 12μm under the action of nonlinearity. Ultimately, an ultra-flat ultra-wideband supercontinuum laser output with a wavelength covering ultraviolet to mid-infrared is achieved.

[0047] The advantages of this exemplary embodiment are:

[0048] (1) This exemplary embodiment uses noise-like pulses as seed sources, which can minimize residual pumping and greatly improve the flatness of the entire supercontinuum spectrum: a noise-like pulse is a pulse envelope composed of a large number of ultrashort femtosecond pulses with randomly changing amplitudes and phases; the high peak power of its sub-pulses and the interaction between them can be used to promote the formation of a broadband flat spectrum through effects such as soliton splitting and Raman soliton self-frequency shift; at the same time, using noise-like pulses as pumps helps to minimize residual pumping and greatly improve the flatness of the entire supercontinuum spectrum.

[0049] (2) This exemplary embodiment realizes dual-wavelength pumping through a seed source, and through a multi-stage cascade amplification structure and a multi-stage nonlinear medium structure, it can effectively integrate the supercontinuum spectra generated by the two wavelength pumps into one spectrum, greatly improving the spectral coverage of the supercontinuum spectrum, and thus realizing an ultra-wideband supercontinuum spectrum output covering the ultraviolet to mid-infrared.

[0050] (3) This exemplary embodiment adopts a full polarization-maintaining structure, which can output a supercontinuum with high quality, high stability and high coherence: This exemplary embodiment adopts a full polarization-maintaining seed source and the subsequent amplification and broadening system all uses polarization-maintaining optical fiber and polarization-maintaining devices, which can largely eliminate polarization-related disturbances or distortions. Since the output supercontinuum has a linear polarization characteristic, its high coherence can be widely used in biomedical imaging, gas sensing, infrared countermeasures and other fields.

[0051] The following content will explain the preferred embodiment examples:

[0052] More preferably, in an exemplary embodiment, if Figure 1 As shown, the fully polarization-maintaining noise pulse seed source includes a nonlinear amplifying loop mirror NALM, a unidirectional ring UR and a first polarization-maintaining coupler coupler1;

[0053] The nonlinear amplifying ring mirror NALM includes a first polarization-maintaining single-mode optical fiber PM-SMF1, a double-clad polarization-maintaining erbium-doped optical fiber PM-EDF, a first LD pump LD1 of 976nm and a 976 / 1550 wavelength division multiplexer PM-WDM; the unidirectional ring UR includes a second polarization-maintaining single-mode optical fiber PM-SMF2, a second polarization-maintaining coupler coupler2 and a first polarization-maintaining isolator ISO;

[0054] The first LD pump LD1 is connected to the pump end of the wavelength division multiplexer PM-WDM, the common end of the wavelength division multiplexer PM-WDM is connected to the double-clad polarization-maintaining erbium-doped fiber PM-EDF, the first polarization-maintaining single-mode fiber PM-SMF1, and the first coupling arm of the first polarization-maintaining coupler coupler1 in sequence, and the signal end of the wavelength division multiplexer PM-WDM is connected to the second coupling arm of the first polarization-maintaining coupler coupler1; the common end of the first polarization-maintaining coupler coupler1 is connected to the input end of the second polarization-maintaining coupler coupler2, the 40% port of the second polarization-maintaining coupler coupler2 outputs a 1.55μm noise-like square wave pulse, and the 60% port of the second polarization-maintaining coupler coupler2 is respectively connected to the first polarization-maintaining isolator ISO, the second polarization-maintaining single-mode fiber PM-SMF2, and the non-common end of the first polarization-maintaining coupler coupler1.

[0055] Specifically, in this exemplary embodiment, the full polarization-maintaining noise-like pulse seed source is specifically a full polarization-maintaining "8"-shaped cavity erbium-doped mode-locked seed source including a nonlinear amplifying loop mirror NALM and a unidirectional ring UR. The nonlinear amplifying loop mirror NALM includes a polarization-maintaining single-mode fiber PM-SMF1, a double-clad polarization-maintaining erbium-doped fiber PM-EDF and a 976 / 1550 wavelength division multiplexer PM-WDM. The 976nm LD pump is coupled into the cavity through the wavelength division multiplexer PM-WDM. The nonlinear amplifying loop mirror NALM and the unidirectional ring UR are connected through a 2×2 3dB polarization-maintaining coupler coupler1. The unidirectional ring UR uses a second polarization-maintaining single-mode fiber PM-SMF2 to increase the cavity length, and the first polarization-maintaining isolator ISO is used to ensure the unidirectional transmission of the pulse in the unidirectional ring. Finally, a 1.55μm noise-like NLP seed pulse is output through the 40% port of the 40:60 second polarization-maintaining coupler coupler2.

[0056] By adopting the method of this exemplary embodiment, no polarization controller is required in the cavity, and self-starting of the mode-locked state can be achieved by simply adjusting the pump input, which can ensure long-term stable output of the seed source; the unidirectional ring UR uses the second polarization-maintaining single-mode optical fiber PM-SMF2 to increase the cavity length, which can effectively reduce the repetition frequency of the mode-locked pulse and increase the single pulse energy.

[0057] More preferably, in an exemplary embodiment, if Figure 1 As shown, a third polarization-maintaining coupler coupler3 is further arranged between the full polarization-maintaining noise-like pulse seed source and the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier, the 1% port of the third polarization-maintaining coupler coupler3 outputs a signal monitoring signal Monitoring, the 99% port of the third polarization-maintaining coupler coupler3 is connected to the full polarization-maintaining noise-like pulse seed source, and the common end of the third polarization-maintaining coupler coupler3 is connected to the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier.

[0058] Specifically, in this exemplary embodiment, a 1:99 third polarization-maintaining coupler Coupler3 is connected to the seed source, and a 1% port thereof is used for signal monitoring.

[0059] More preferably, in an exemplary embodiment, if Figure 1 As shown, the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier comprises a first-stage polarization-maintaining ytterbium-doped erbium fiber amplifier, a second-stage polarization-maintaining ytterbium-doped erbium fiber amplifier and a third polarization-maintaining single-mode fiber PM-SMF3 connected in sequence;

[0060] The first-stage polarization-maintaining erbium-doped fiber amplifier includes a second LD pump LD2 of 976nm, a first pump combiner and a first polarization-maintaining erbium-ytterbium co-doped double-clad fiber PM-EYDF1; the second-stage polarization-maintaining erbium-doped fiber amplifier includes a third LD pump LD3 of 976nm, a second pump combiner and a second polarization-maintaining erbium-ytterbium co-doped double-clad fiber PM-EYDF2;

[0061] The pump combining end of the first pump combiner is connected to the second LD pump LD2, the pulse combining end of the first pump combiner is connected to the full polarization-maintaining noise-like pulse seed source, and the combining output end of the first pump combiner is connected to the first polarization-maintaining erbium-ytterbium co-doped double-clad fiber PM-EYDF1; the pump combining end of the second pump combiner is connected to the third LD pump, the pulse combining end of the second pump combiner is connected to the first polarization-maintaining erbium-ytterbium co-doped double-clad fiber PM-EYDF1, and the combining output end of the second pump combiner is respectively connected to the second polarization-maintaining erbium-ytterbium co-doped double-clad fiber PM-EYDF2 and the third polarization-maintaining single-mode fiber PM-SMF3, and the third polarization-maintaining single-mode fiber PM-SMF3 outputs a 1.5-2.3μm spectrum.

[0062] Specifically, in this exemplary embodiment, the seed pulse is first amplified and pre-broadened by a two-stage polarization-maintaining erbium-doped fiber amplifier: first, in the first stage of the polarization-maintaining erbium-doped fiber amplifier, a 976nm multimode laser diode, namely the second LD pump LD2, is used to provide pumping for the seed source through the first pump combiner Combiner, and the first polarization-maintaining erbium-ytterbium co-doped double-clad fiber PM-EYDF1 is used as the gain medium. This stage of amplification can increase the seed light power to the watt level; then, in the second stage of the polarization-maintaining erbium-doped fiber amplifier, a 976nm multimode laser diode, namely the third LD pump LD3, is also used to provide pumping, and the gain fiber is the same as the first stage (the second polarization-maintaining erbium-ytterbium co-doped double-clad fiber PM-EYDF1), which can increase the 1.55μm seed light to the ten-watt level, and finally, a section of polarization-maintaining single-mode quartz, namely the third polarization-maintaining single-mode fiber PM-SMF3, is connected to the gain fiber of the second stage as a pump stripper. That is to say, after the 1.55μm seed pulse laser passes through a two-stage polarization-maintaining erbium-ytterbium fiber amplifier and the third polarization-maintaining single-mode fiber PM-SMF3, the power is amplified and expanded to 2.3μm through nonlinear effects such as self-phase modulation, modulation instability and soliton self-frequency shift, achieving a 1.5-2.3μm pre-broadened spectrum output.

[0063] More preferably, in an exemplary embodiment, if Figure 1 As shown, a second polarization-maintaining isolator ISO is arranged between the full polarization-maintaining noise-like pulse seed source and the first pump combiner, a third polarization-maintaining isolator ISO is arranged between the first polarization-maintaining erbium ytterbium co-doped double-clad fiber PM-EYDF1 and the second pump combiner, and a fourth polarization-maintaining isolator ISO is arranged between the second polarization-maintaining erbium ytterbium co-doped double-clad fiber PM-EYDF2 and the third polarization-maintaining single-mode fiber PM-SMF3.

[0064] Specifically, in this exemplary embodiment, the second polarization-maintaining isolator ISO is connected to the 99% port of the polarization-maintaining coupler to prevent back light; the third polarization-maintaining isolator ISO prevents back light between the first-stage polarization-maintaining ytterbium-doped erbium fiber amplifier and the second-stage polarization-maintaining ytterbium-doped erbium fiber amplifier; and the fourth polarization-maintaining isolator ISO prevents back light between the second-stage polarization-maintaining ytterbium-doped erbium fiber amplifier and the third polarization-maintaining single-mode fiber PM-SMF3.

[0065] More preferably, in an exemplary embodiment, if Figure 1 As shown, the third polarization-maintaining single-mode fiber PM-SMF3 is subsequently connected to a section of polarization-maintaining high-nonlinear fiber PM-HNLF, the zero dispersion point of which is located at 1550nm. By pumping in the anomalous dispersion region, sufficient nonlinear effect can be obtained to further broaden the spectrum and obtain a 0.9-2.9μm flat supercontinuum output.

[0066] More preferably, in an exemplary embodiment, if Figure 1 As shown, the polarization-maintaining large mode field erbium-doped fiber amplifier includes a fourth LD pump LD4 of 976nm, a third pump combiner combiner, and a polarization-maintaining large mode field erbium-doped fiber PLMA-EYDF;

[0067] The pump combining end of the third pump combiner is connected to the fourth LD pump LD4, the pulse combining end of the third pump combiner is connected to the two-stage polarization-maintaining erbium-doped fiber amplifier, and the combining output end of the third pump combiner is connected to the polarization-maintaining large mode field erbium-doped fiber PLMA-EYDF.

[0068] Specifically, in this exemplary embodiment, a polarization-maintaining large mode field erbium-doped fiber amplifier is entered, which uses a 976nm multimode laser diode, i.e., the fourth LD pump LD4, to provide pumping for the seed source through the third pump combiner, and a section of polarization-maintaining large mode field erbium-doped fiber PLMA-EYDF is used as the gain medium to amplify the supercontinuum source at 1.55μm.

[0069] More preferably, in an exemplary embodiment, if Figure 1 As shown, a section of polarization-maintaining large mode field ytterbium-doped fiber PLMA-YDF is then cascaded to amplify the supercontinuum source at 1.06μm, thereby obtaining a supercontinuum spectrum containing two peaks at 1.06μm and 1.55μm.

[0070] More preferably, in an exemplary embodiment, if Figure 1 As shown in the figure, the mode field adapter MFA is used to match the mode fields of the two optical fibers to reduce the loss and reflection caused by mode mismatch; then the polarization-maintaining photonic crystal fiber PM-PCF is pumped by a supercontinuum source, and its zero dispersion wavelength is located at 1μm. Through 1.06μm pump spike pumping, under the action of nonlinear mechanisms such as modulation instability, self-phase modulation, Raman soliton self-frequency shift and dispersion waves, the spectrum is rapidly broadened from the vicinity of the pump wavelength to both sides, forming a supercontinuum spectrum. Under the joint action of this high peak power and high nonlinear fiber , the supercontinuum can cover the ultraviolet band to the near-infrared band; then it enters the polarization-maintaining fluorotellurite fiber PM-TBY, whose zero dispersion wavelength is at 1.55μm. Under the pumping of the 1.55μm pump peak, the spectrum rapidly broadens from the vicinity of the pump wavelength to both sides, forming a supercontinuum spanning the near-infrared band to the mid-infrared band, of which the infrared band can cover 4μm; finally it enters a section of polarization-maintaining sulfide fiber PM-As2S3, whose zero dispersion wavelength is at 4μm, and the spectrum can be further extended to 12μm under the action of nonlinearity. Ultimately, an ultra-flat ultra-wideband supercontinuum laser output with a wavelength covering the ultraviolet to the mid-infrared can be achieved.

[0071] More preferably, in an exemplary embodiment, if Figure 1As shown, the gain fibers in the two-stage polarization-maintaining erbium-doped fiber amplifier and the polarization-maintaining large mode field erbium-doped fiber amplifier are both placed on a water-cooled plate, and water is dripped at the melting point.

[0072] Specifically, in this exemplary embodiment, each level of gain optical fiber is placed on a water-cooled plate, and water is dripped at the melting point to achieve cooling while refracting the pump light from the cladding to protect the melting point.

[0073] The gain optical fiber specifically includes: the first polarization maintaining erbium ytterbium co-doped double cladding optical fiber PM-EYDF1 in the first-stage polarization maintaining ytterbium erbium doped fiber amplifier, the first polarization maintaining erbium ytterbium co-doped double cladding optical fiber PM-EYDF2 in the second-stage polarization maintaining ytterbium erbium doped fiber amplifier, and the polarization maintaining large mode field erbium ytterbium doped optical fiber PLMA-EYDF of the polarization maintaining large mode field ytterbium erbium doped fiber amplifier.

[0074] More preferably, in an exemplary embodiment, if Figure 1 As shown, the output end of the polarization-maintaining sulfide optical fiber is cut at a 7-degree bevel to prevent light return.

[0075] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping, characterized by: Includes sequential connections: Full polarization-maintaining noise-like pulse seed source, outputting 1.55μm noise-like square wave pulses; Two-stage polarization-maintaining erbium-doped fiber amplifier, outputting 1.5-2.3μm spectrum; Polarization-maintaining high nonlinear optical fiber further broadens the spectrum and realizes 0.9-2.9μm flat supercontinuum source output; Polarization-maintaining large-mode-field erbium-doped fiber amplifier to amplify the supercontinuum source at 1.55 μm; Polarization-maintaining large-mode-field ytterbium-doped fiber amplifies the supercontinuum source at 1.06 μm; Mode field adapter, to match the mode field of the optical fiber; Polarization-maintaining photonic crystal fiber, which extends short waves to the ultraviolet band under the action of dispersion and nonlinear effects; The polarization-maintaining fluorotellurite extends the long wave to 4 μm under the action of Raman soliton self-frequency shift; The polarization-maintaining sulfide optical fiber further expands the spectrum to 12μm under the action of nonlinearity, achieving ultra-flat ultra-wideband supercontinuum laser output with wavelengths covering ultraviolet to mid-infrared.

2. The fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping according to claim 1, characterized in that: The fully polarization-maintaining noise-like pulse seed source comprises a nonlinear amplifying ring mirror, a unidirectional ring and a first polarization-maintaining coupler; The nonlinear amplifying loop mirror comprises a first polarization-maintaining single-mode optical fiber, a double-clad polarization-maintaining erbium-doped optical fiber, a first LD pump of 976nm and a 976 / 1550 wavelength division multiplexer; the unidirectional loop comprises a second polarization-maintaining single-mode optical fiber, a second polarization-maintaining coupler and a first polarization-maintaining isolator; The first LD pump is connected to the pump end of the wavelength division multiplexer, the common end of the wavelength division multiplexer is connected to the double-clad polarization-maintaining erbium-doped fiber, the first polarization-maintaining single-mode fiber, and the first coupling arm of the first polarization-maintaining coupler in sequence, and the signal end of the wavelength division multiplexer is connected to the second coupling arm of the first polarization-maintaining coupler; the common end of the first polarization-maintaining coupler is connected to the input end of the second polarization-maintaining coupler, the 40% port of the second polarization-maintaining coupler outputs a 1.55μm noise-like square wave pulse, and the 60% port of the second polarization-maintaining coupler is respectively connected to the first polarization-maintaining isolator, the second polarization-maintaining single-mode fiber, and the non-common end of the first polarization-maintaining coupler.

3. The fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping according to claim 1, characterized in that: A third polarization-maintaining coupler is also arranged between the full polarization-maintaining noise-like pulse seed source and the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier. The 1% port of the third polarization-maintaining coupler outputs a signal monitoring signal, the 99% port of the third polarization-maintaining coupler is connected to the full polarization-maintaining noise-like pulse seed source, and the common end of the third polarization-maintaining coupler is connected to the two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier.

4. The fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping according to claim 1, characterized in that: The two-stage polarization-maintaining ytterbium-doped erbium fiber amplifier comprises a first-stage polarization-maintaining ytterbium-doped erbium fiber amplifier, a second-stage polarization-maintaining ytterbium-doped erbium fiber amplifier and a third polarization-maintaining single-mode optical fiber connected in sequence; The first-stage polarization-maintaining erbium-doped fiber amplifier includes a second LD pump at 976 nm, a first pump combiner, and a first polarization-maintaining erbium-ytterbium co-doped double-clad fiber; the second-stage polarization-maintaining erbium-doped fiber amplifier includes a third LD pump at 976 nm, a second pump combiner, and a second polarization-maintaining erbium-ytterbium co-doped double-clad fiber; The pump combining end of the first pump combiner is connected to the second LD pump, the pulse combining end of the first pump combiner is connected to the full polarization-maintaining noise-like pulse seed source, and the combining output end of the first pump combiner is connected to the first polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber; the pump combining end of the second pump combiner is connected to the third LD pump, the pulse combining end of the second pump combiner is connected to the first polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber, and the combining output end of the second pump combiner is respectively connected to the second polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber and the third polarization-maintaining single-mode optical fiber, and the third polarization-maintaining single-mode optical fiber outputs a 1.5-2.3 μm spectrum.

5. The fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping according to claim 4, characterized in that: A second polarization-maintaining isolator is arranged between the full polarization-maintaining noise-like pulse seed source and the first pump combiner, a third polarization-maintaining isolator is arranged between the first polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber and the second pump combiner, and a fourth polarization-maintaining isolator is arranged between the second polarization-maintaining erbium-ytterbium co-doped double-clad optical fiber and the third polarization-maintaining single-mode optical fiber.

6. The fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping according to claim 1, characterized in that: The polarization-maintaining large mode field erbium-doped fiber amplifier comprises a fourth LD pump of 976nm, a third pump combiner, and a polarization-maintaining large mode field erbium-doped fiber; The pump combining end of the third pump combiner is connected to the fourth LD pump, the pulse combining end of the third pump combiner is connected to the two-stage polarization-maintaining erbium-doped fiber amplifier, and the combining output end of the third pump combiner is connected to the polarization-maintaining large mode field erbium-doped fiber.

7. The fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping according to claim 1, characterized in that: The gain optical fibers in the two-stage polarization-maintaining ytterbium-doped erbium optical fiber amplifier and the polarization-maintaining large-mode-field ytterbium-doped erbium optical fiber amplifier are both placed on a water-cooling plate, and water is dripped at the melting point at the same time.

8. The fully polarization-maintaining ultra-flat ultra-wideband supercontinuum laser based on noise-like pulse pumping according to claim 1, characterized in that: The output end of the polarization-maintaining sulfide optical fiber is cut at a 7-degree bevel angle.

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