CN213602177U - Linear cavity mode-locked fiber laser based on phase offset - Google Patents
Linear cavity mode-locked fiber laser based on phase offset Download PDFInfo
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Abstract
The utility model discloses a line type chamber mode locking fiber laser based on phase place biasing, include: the device comprises a pumping source, a wavelength division multiplexer connected with the pumping source, a polarization maintaining gain optical fiber connected with a common end of the wavelength division multiplexer, and a collimator connected with a transmission end of the wavelength division multiplexer; a birefringent crystal; a Faraday rotator; a half wave plate; a Faraday rotator mirror connected to the polarization maintaining gain fiber; the polarization beam splitter prism is used for generating interference on orthogonal pulse light returned by the birefringent crystal to realize mode locking and then dividing the orthogonal pulse light into two paths; and the high reflecting mirror is used for reflecting one path of transmitted light output by the polarization beam splitter prism back to the linear cavity. The utility model discloses producing in polarization beam splitting prism department and interfering the realization mode locking, greatly reduced the threshold value that the mode locking starts, improved the repetition frequency, improved holistic stability and reliability simultaneously.
Description
Technical Field
The utility model belongs to the technical field of the light laser instrument and specifically relates to a line type chamber mode locking fiber laser based on phase place biasing is related to.
Background
This section merely provides background information related to the present application so as to enable those skilled in the art to more fully and accurately understand the present application, which is not necessarily prior art.
Compared with a solid laser, the ultrafast pulse mode-locked fiber laser has the advantages of low price, compact structure, high conversion efficiency, good beam quality and the like, is widely applied to the fields of medical operations, laser communication, optical frequency combing, material micromachining and the like, and provides higher requirements for the running stability of the ultrafast laser in different environments, while the stability and reliability of industrial ultrafast lasers, particularly seed sources, are not well solved all the time. The seed source technology itself, which replaces the solid state with optical fiber technology, has many advantages, and lasers using fully-polarization maintaining optical fibers are considered to be more effective methods for resisting environmental changes in optical fiber technology.
The current common technology is to use saturable absorber mode locking technology to make full polarization-maintaining fiber laser. However, saturable absorption elements such as semiconductor saturable absorbers (SESAMs), carbon nanotube saturable absorbers, graphene saturable absorbers, etc. all have the disadvantages of low damage threshold and decay over time. These weaknesses limit their exit from the laboratory to a broader industrial market. Conventional non-linear polarization rotating (NPR) fiber laser technology cannot fully utilize a fully polarization-preserving system. Without the application of polarization maintaining fiber, the NPR fiber laser technology is easily interfered by environment. In order to obtain a NPR laser with higher stability, it is attempted to replace the non-polarization maintaining fiber in the laser cavity with a polarization maintaining fiber to improve the stability.
A key problem to be solved in order to achieve NPR mode locking in fully-polarization-maintaining fibers is to compensate for the Group Velocity Mismatch (GVM) between the two orthogonal polarization components. The temporal separation of the orthogonal polarization components by GVM can cause degradation of the pulse quality. In order to solve this problem, those skilled in the art continuously explore and propose different solutions: nielsen et al, in 2007, proposed the use of a Faraday rotator mirror as an end mirror of the laser cavity, and proposed a linear cavity polarization-maintaining fiber laser based on nonlinear polarization rotation mode locking, which can generate pulses with a repetition frequency of 5.96 MHz and a pulse width of 5.6 ps; jiaqi Zhou et al proposed a full polarization-maintaining fiber laser based on nonlinear polarization rotation mode locking in 2008, using a faraday optical rotation mirror to compensate group velocity mismatch and linear phase shift in the laser, which can generate dissipative solitons, and realizing single pulse energy of 2.9nJ and pulse width of 5.9 ps; szczepanek et al propose to fuse three sections of polarization maintaining fibers at a special angle in 2017 to serve as an artificial saturable absorber for realizing NPR mode locking, and the developed full polarization maintaining fiber laser can realize ultrashort pulse output with 150 fs pulse width; wenchao Zhang et al proposed in 2018 to weld some welding points in a ring cavity laser at a certain angle to realize NPR mode locking, thereby increasing the repetition frequency of this type of laser to 111 MHz. However, the technical problems that the conventional mode-locked fiber laser is unstable, the NPR mode-locking technology is difficult to realize in the polarization-preserving fiber, the repetition frequency of the laser is difficult to improve and the like are not completely solved by the schemes.
SUMMERY OF THE UTILITY MODEL
The utility model discloses aim at solving one of the technical problem that exists among the prior art at least. Therefore, the utility model provides a line type chamber mode locking fiber laser based on phase place biasing has reduced the mode locking threshold value and has improved the repetition frequency.
The utility model provides a linear cavity mode-locked fiber laser based on phase offset, which comprises a pumping source, a wavelength division multiplexer connected with the pumping source, a polarization-maintaining gain fiber connected with the public end of the wavelength division multiplexer, and a collimator connected with the transmission end of the wavelength division multiplexer; the laser further includes:
the double refraction crystal is used for projecting small pulse light formed by laser oscillation at random to the fast axis and the slow axis of the double refraction crystal for phase bias, so that the small pulse light is converted into orthogonal pulse light comprising orthogonal first polarized light and second polarized light;
a Faraday rotator for rotating the polarization direction of the orthogonal pulse light by 45 degrees clockwise;
the half wave plate is used for adjusting the polarization state of the orthogonal pulse light so as to respectively project the first polarized light and the second polarized light onto the fast axis and the slow axis of the collimator;
the Faraday polariscope is connected with the polarization-maintaining gain fiber and is used for rotating the orthogonal pulse light by 90 degrees, so that the orthogonal pulse light and the second polarized light exchange transmission paths and then are transmitted through the polarization-maintaining gain fiber, the wavelength division multiplexer, the collimator, the half wave plate, the Faraday rotator and the birefringent crystal in sequence;
the polarization beam splitter prism is used for generating interference on orthogonal pulse light returned by the birefringent crystal to realize mode locking and then dividing the orthogonal pulse light into two paths;
and the high reflecting mirror is used for reflecting one path of transmitted light output by the polarization beam splitter prism back to the linear cavity.
In a preferred embodiment, the wavelength division multiplexer and the fiber collimator are replaced by a fiber wavelength division multiplexing collimator to which the pump source is connected.
In a preferred embodiment, a dispersive element is arranged between the polarization splitting prism and the high mirror.
In a preferred embodiment, the dispersive elements are grating pairs.
In a preferred embodiment, the grating density of the grating pairs is in the range of 150 to 2000 stripes/mm.
In a preferred embodiment, the polarization-maintaining gain fiber is a large mode area polarization-maintaining fiber, a doped gain polarization-maintaining fiber, a large mode area double-clad polarization-maintaining fiber or a polarization-maintaining photonic crystal fiber.
In a preferred embodiment, the Faraday rotator is a sheet type Faraday rotator or a Faraday rotator formed by inserting a magneto-optical crystal into a permanent magnet.
In a preferred embodiment, the magnitude of the phase offset produced by the birefringent crystal
Is a function of the nature and thickness of the birefringent crystal, i.e.
Wherein, in the step (A),
is the refractive index of the e-light,
is the refractive index of the o light,lλ is the wavelength, which is the thickness of the birefringent crystal.
In a preferred embodiment, the length of the polarization maintaining gain fiber is adjustable to adjust the cavity length of the laser by adjusting the length of the polarization maintaining gain fiber.
Compared with the prior art, the utility model discloses following beneficial effect has:
1. the utility model adopts a half wave plate to project two beams of orthogonal polarized light to the fast and slow axes of the polarization maintaining gain fiber, and transmits the polarized light along the fast and slow axes of the polarization maintaining gain fiber respectively, and adopts a Faraday polariscope to realize the group velocity mismatch and the linear phase shift compensation; meanwhile, a phase shift unit is formed by the Faraday rotator and the birefringent crystal, the phase difference of pi/2 is generated between the light transmitted by the fast axis and the light transmitted by the slow axis in the orthogonal polarization state, interference is generated at the position of the return polarization beam splitter prism to realize mode locking, and the threshold value for starting the mode locking is greatly reduced after the orthogonal pulse light is subjected to phase shift through the phase shift unit, so that the mode locking can be realized in the structure under high repetition frequency, the repetition frequency is improved, and the integral stability and reliability are improved.
2. The optical fiber wavelength division multiplexing collimator is used for replacing a conventional wavelength division multiplexer and an optical fiber collimator, so that the length of an optical fiber in the optical fiber laser is greatly shortened, a laser system is simplified, the coupling power and efficiency are improved, and the repetition frequency is improved.
3. The utility model provides a conventional mode locking fiber laser unstability, NPR mode locking technique are difficult to realize in polarization maintaining optical fiber, and the difficult scheduling problem that improves of laser repetition frequency to make its ideal seed light source as future industry Burst mode type ultrafast industry laser.
4. The utility model discloses an thereby utilize ultra-thin space component can carry out the limit compression with the length of line die cavity, the length of line die cavity is the more high more of short repetition frequency, can all realize the mode locking on the short cavity when the mode locking threshold value is lower usually, just realize the mode locking when repetition frequency is higher, consequently the utility model discloses a than with the higher repetition frequency of discrete optical fiber polarization maintaining component, can reach more than the hundred megahertz magnitude of orders, thereby the utility model discloses a seed source of laser as high repetition frequency is enlarged in future femto second, and the pulse train mode frequency selection all has very important effect, has extremely wide application prospect.
Drawings
Fig. 1 is a schematic structural diagram of a first embodiment of a linear cavity mode-locked fiber laser disclosed by the present invention.
Fig. 2 is a schematic structural diagram of a second embodiment of the linear cavity mode-locked fiber laser disclosed in the present invention.
Fig. 3 is a schematic structural diagram of a third embodiment of the linear cavity mode-locked fiber laser disclosed in the present invention.
Fig. 4 is a schematic structural diagram of a fourth embodiment of the linear cavity mode-locked fiber laser disclosed in the present invention.
Detailed Description
To further clarify the technical solutions and effects adopted by the present application to achieve the intended purpose, the following detailed description is given with reference to the accompanying drawings and preferred embodiments according to the present application. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Example one
As shown in fig. 1, the present embodiment discloses a phase-bias-based linear cavity mode-locked fiber laser (hereinafter, also referred to as "laser" or "optical laser"), including: the linear cavity is respectively provided with a Faraday rotation mirror 2 and a high reflection mirror 11 at two opposite end surfaces in the linear cavity; the wavelength division multiplexer 4, the collimator 5, the half-wave plate 6, the Faraday rotator 7, the birefringent crystal 8 and the polarization beam splitter prism 9 are sequentially arranged between the Faraday rotation mirror 2 and the high reflecting mirror 11, the wavelength division multiplexer 4 is connected with the Faraday rotation mirror 2 through a polarization-maintaining gain optical fiber 3, and the transmission end of the wavelength division multiplexer 4 is connected with the collimator 5; a high reflecting mirror 11 disposed opposite to the polarization splitting prism 9; the pump source 1 connected with the wavelength division multiplexer 4 is used for providing pump light for the wavelength division multiplexer 4 by the pump source 1, and the wavelength division multiplexer 4 is used for coupling the pump light into the polarization-maintaining gain fiber 3 to generate laser gain.
The birefringent crystal 8 is used for carrying out phase offset adjustment on small pulse light formed randomly by laser oscillation, so that the small pulse light in a linear polarization state is projected onto a fast axis and a slow axis of the birefringent crystal 8, and the small pulse light is divided into orthogonal first polarized light and second polarized light. The intensity ratio between the first polarized light and the second polarized light is determined by the angle between the fast axis of the birefringent crystal 8 and the small pulse light when entering the birefringent crystal 8.
Wherein the fast and slow axes of the birefringent crystal 8 introduce an asymmetric phase shift, resulting in a phase shift difference, i.e. a phase offset, of the light propagating with a polarization parallel to the different axes, the magnitude of the phase shift difference
Determined by the nature and thickness of the birefringent crystal, i.e.
Wherein, in the step (A),
is the refractive index of the e-light,
is the refractive index of the o light,lλ is the wavelength, which is the thickness of the birefringent crystal.
The Faraday rotator 7 is a sheet type Faraday rotator or a Faraday rotator formed by inserting a magneto-optical crystal into a permanent magnet. The faraday rotator 7 is used to rotate the polarization direction of the orthogonal pulsed light by 45 ° clockwise.
The half-wave plate 6 is used for adjusting the polarization state of the orthogonal pulse light, and projecting the first polarized light and the second polarized light of the orthogonal pulse light onto the fast axis and the slow axis of the collimator 5 respectively.
Orthogonal pulses enter the polarization maintaining gain fiber 3 and are transmitted along the fast axis and the fast and slow axes of the polarization maintaining gain fiber 3; at the moment, a pumping source 1 injects pumping light into the linear cavity through a wavelength division multiplexer 4, so that orthogonal pulses enter a polarization-maintaining gain fiber 3 to be amplified to generate laser gain, and finally reach a Faraday optical rotation mirror 2 at one end of the linear cavity.
The polarization-maintaining gain fiber 3 adopts one of a large mode area polarization-maintaining fiber, a doped gain polarization-maintaining fiber, a large mode area double-cladding polarization-maintaining fiber and a polarization-maintaining photonic crystal fiber. One end of the polarization-maintaining gain fiber 3 is connected with the common end of the wavelength division multiplexer 4, and the other end of the polarization-maintaining gain fiber 3 is connected with the Faraday rotator mirror 2. Therefore, the cavity length of the linear cavity can be correspondingly adjusted by adjusting the length of the polarization maintaining gain fiber 3, and the shorter the cavity length of the linear cavity, the higher the repetition frequency of the laser light generated by the laser.
The faraday rotator 2 rotates the orthogonal pulse light by 90 degrees, so that the first polarized light and the second polarized light of the orthogonal pulse exchange transmission paths with each other, and then sequentially transmit the orthogonal pulse light to the polarization splitting prism 9 through the polarization maintaining gain fiber 3, the wavelength division multiplexer 4, the collimator 5, the half wave plate 6, the faraday rotator 7 and the birefringent crystal 8.
When the orthogonal pulse light is transmitted back to the polarization beam splitter prism 9, interference light is formed by interference, the polarization beam splitter prism 9 divides the interference light into two paths, one path of interference light is reflected back to the linear cavity by the high reflector 11, and the other path of interference light is coupled as the output of the laser.
For example, in this embodiment the pump source 1 is a 976nm single mode pump. Correspondingly, the working wavelength of the Faraday rotator mirror 2 is 1550nm, a 976nm high-reflection 1550nm high-transmission optical filter is arranged in the wavelength division multiplexer 4, a 1550nm antireflection film is plated on the collimator 5, 1550nm antireflection films are plated on the front surface and the rear surface of the half wave plate 6, 1550nm antireflection films are plated on the front surface and the rear surface of the birefringent crystal 8, the transmission-reflection ratio of the polarization splitting prism 9 is 50:50, and a 1550nm full-reflection film is plated on the high-reflection mirror 11.
For easy understanding, the control process of the laser disclosed by the utility model is as follows:
and step S1, coupling the pump light of the pump source 1 into the linear cavity through the wavelength division multiplexer 4, and increasing the pump power of the pump source 1 to be above the threshold value of the laser so that the laser can generate small-pulse random oscillation to generate laser.
In step S2, the laser is oscillated to form small pulse light at random by aligning the optical collimator 5 with the high reflection mirror 11.
After the laser can generate small pulse random oscillation, the generated random small pulse light can form stable ultrashort pulse light, namely small pulse light after oscillating for many times in the online cavity.
Step S3, when the small pulse light passes through the birefringent crystal 8 with the polarization splitting prism 9 as a starting point, the birefringent crystal 8 performs phase offset adjustment on the pulse light, specifically, the small pulse light in a linear polarization state is projected onto the fast axis and the slow axis of the birefringent crystal 8, so that the small pulse light is converted into orthogonal pulse light, where the orthogonal pulse light includes a first polarized light and a second polarized light orthogonal to the first polarized light.
In step S3, the orthogonal pulse light enters the faraday rotator 7, and the polarization direction of the orthogonal pulse light is rotated by 45 ° clockwise by the faraday rotator 7.
Step S4, the orthogonal pulse light is subjected to polarization state adjustment through a half wave plate 6, and the half wave plate 6 projects the polarization direction of the orthogonal pulse light to the fast axis and the slow axis of the collimator 5; then, the orthogonal pulse enters the polarization maintaining gain fiber 3 and is transmitted along the fast axis and the fast and slow axis of the polarization maintaining gain fiber 3; at the moment, a pumping source 1 injects pumping light into the linear cavity through a wavelength division multiplexer 4, so that orthogonal pulses enter a polarization-maintaining gain fiber 3 to be amplified to generate laser gain, and finally reach a Faraday optical rotation mirror 2 at one end of the linear cavity.
Step S5 is that the faraday rotator 2 rotates the orthogonal pulse light by 90 °, and after the first polarized light and the second polarized light of the orthogonal pulse light exchange transmission paths with each other, the orthogonal pulse light is transmitted to the polarization splitting prism 9 through the polarization maintaining gain fiber 3, the wavelength division multiplexer 4, the collimator 5, the half wave plate 6, the faraday rotator 7, and the birefringent crystal 8 in this order.
Wherein, the first polarized light and the second polarized light of orthogonal pulse light exchange transmission path each other, refer to: if the first polarized light is transmitted along the fast axis of each device on the transmission path in the process of transmitting the first polarized light to the Faraday rotation mirror 2, the second polarized light is transmitted along the slow axis of each device on the transmission path in the process of transmitting the second polarized light to the Faraday rotation mirror 2; correspondingly, after the orthogonal pulse light is rotated by 90 ° by the faraday rotator 2, the orthogonal pulse light is transmitted from the faraday rotator 2 toward the polarization beam splitter prism 9, and at this time, the first polarized light is transmitted along the slow axis of each device on the transmission path, and the second polarized light is transmitted along the fast axis of each device on the transmission path.
And step S6, the orthogonal pulse light passes through the half wave plate 6, the Faraday rotator 7 and the birefringent crystal 8 in sequence, the orthogonal pulse light generates interference to realize mode locking when returning to the polarization beam splitter prism 9, the polarization beam splitter prism 9 divides the interference light into two paths, one path of transmission light is reflected back to the linear cavity by the high reflector 11 to be used as small pulse light formed by the next laser oscillation, and the other path of reflection light is coupled to be output laser of the laser.
When a first polarized light and a second polarized light of orthogonal pulse light enter the collimator 5 and are transmitted on a fast axis and a slow axis respectively, due to the fact that refractive indexes of the fast axis and the slow axis are different, group velocity mismatch and linear phase shift difference can be generated between the first polarized light and the second polarized light; when the faraday rotator mirror 2 rotates the orthogonal pulse light by 90 degrees, the transmission paths of the first polarized light and the second polarized light are mutually exchanged, so that the transmission paths of the two polarized component lights from the collimator 5 to the return collimator 5 are completely the same, and the group velocity mismatch and the linear phase shift caused by the dispersion of the optical fiber material are equal, so that the group velocity mismatch and the linear phase shift can be perfectly compensated when the orthogonal pulse light returns to the collimator 5, and only the nonlinear phase shift characteristic is left when the orthogonal pulse light returns to the collimator 5.
The orthogonal pulse light is formed by changing the polarization direction of the small pulse light, so that the orthogonal pulse light has the characteristic of uneven light intensity distribution as the small pulse light, the light intensity at the center is strong, the light intensities at two sides are weak, the transmittance at the center is high, the transmittances at two sides are low, and the pulse of the orthogonal pulse light is narrower after the orthogonal pulse light penetrates through the polarization beam splitter prism 9. The orthogonal pulse light interferes at the polarization beam splitter prism 9, the stronger the light intensity of the orthogonal pulse light is, the larger the nonlinear phase difference between the two polarized component lights is, and the larger the transmissivity of the polarization beam splitter prism 9 is; on the contrary, the weaker the light intensity of the orthogonal pulse light, the lower the transmittance of the polarization beam splitter prism 9 relative to the orthogonal pulse light is, and the orthogonal pulse light is mainly used as the output laser of the laser through the reflective optical coupling output line cavity, so that the effect of saturable absorption is achieved to realize mode locking.
Because two beams of polarized component light of orthogonal pulse light pass through the Faraday rotator 7 and the birefringent crystal 8 in positive and negative twice, the orthogonal pulse generates non-anisotropic non-linear phase shift, and the non-linear phase shift and the non-anisotropic phase shift generated in the polarization-preserving gain fiber 3 form phase offset, so that a reflectivity curve is changed, and the orthogonal pulse light serves as a rapid saturable absorber in a laser. The reflectivity of the orthogonal pulse light in the polarization beam splitter prism 9 is related to the nonlinear phase shift amount of the two polarization component lights, the reflectivity is a function of the phase shift difference of the two polarization component lights, the larger the introduced phase shift offset phase shift amount is, the higher the reflectivity is, the lower the phase shift amount is, the lower the reflectivity is, the central part of the orthogonal pulse light is strong, the phase shift amount generated in a linear cavity of the laser is large, so the reflectivity is high, the pulse is easy to form oscillation, and the mode locking of the laser is realized to form ultrashort pulse output.
Example two
As shown in fig. 2. Compared with the first embodiment shown in fig. 1, the present embodiment uses a fiber wdm collimator 5 'instead of the wdm 4 and the fiber collimator 5, and the pump source 1 is connected to the fiber wdm collimator 5'. The adoption of the optical fiber wavelength division multiplexing collimator 5' is favorable for greatly shortening the length of the optical fiber in the optical fiber laser, simplifying the system of the laser, improving the coupling power and efficiency of the laser and improving the repetition frequency.
EXAMPLE III
As shown in fig. 3. Compared with the first embodiment shown in fig. 1, in the present embodiment, a dispersion element is disposed between the polarization splitting prism 9 and the high reflection mirror 11, and dispersion compensation is performed by using the dispersion element, so that the laser can obtain a shorter pulse width, thereby improving the performance of the laser. For example, the dispersive element is a grating pair 10, and the grating density of the grating pair 10 is in a range of 150 to 2000 lines/mm.
For example, in the third embodiment, the pump source 1 adopts a 976nm single-mode pump, the faraday rotator 2 has an operating wavelength of 1030nm, the wavelength division multiplexer 4 is internally provided with a 976nm high-reflection 1030nm high-transmission optical filter, the collimator 5 is coated with a 1030nm antireflection film, the front and back of the half-wave plate 6 are coated with 1030nm antireflection films, the front and back of the birefringent crystal 8 are coated with 1550nm antireflection films, the transmission-reflection ratio of the polarization beam splitter 9 is 50:50, the grating pair 10 adopts a 1600-line transmission grating, and the high reflector 11 is coated with a 1030nm total reflection film.
Example four
As shown in fig. 4. In contrast to the first embodiment shown in fig. 3, the present example employs a fiber wdm collimator 5' instead of the wdm 4 and the fiber collimator 5. The adoption of the optical fiber wavelength division multiplexing collimator 5' is favorable for greatly shortening the length of the optical fiber in the optical fiber laser and simplifying the system of the laser.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (9)
1. A linear cavity mode-locked fiber laser based on phase offset comprises a pumping source, a wavelength division multiplexer connected with the pumping source, a polarization-maintaining gain fiber connected with a common end of the wavelength division multiplexer, and a collimator connected with a transmission end of the wavelength division multiplexer; characterized in that, this laser instrument still includes:
the double refraction crystal is used for projecting small pulse light formed by laser oscillation at random to the fast axis and the slow axis of the double refraction crystal for phase bias, so that the small pulse light is converted into orthogonal pulse light comprising orthogonal first polarized light and second polarized light;
a Faraday rotator for rotating the polarization direction of the orthogonal pulse light by 45 degrees clockwise;
the half wave plate is used for adjusting the polarization state of the orthogonal pulse light so as to respectively project the first polarized light and the second polarized light onto the fast axis and the slow axis of the collimator;
the Faraday polariscope is connected with the polarization-maintaining gain fiber and is used for rotating the orthogonal pulse light by 90 degrees, so that the orthogonal pulse light and the second polarized light exchange transmission paths and then are transmitted through the polarization-maintaining gain fiber, the wavelength division multiplexer, the collimator, the half wave plate, the Faraday rotator and the birefringent crystal in sequence;
the polarization beam splitter prism is used for generating interference on orthogonal pulse light returned by the birefringent crystal to realize mode locking and then dividing the orthogonal pulse light into two paths;
and the high reflecting mirror is used for reflecting one path of transmitted light output by the polarization beam splitter prism back to the linear cavity.
2. The phase-bias based line-cavity mode-locked fiber laser according to claim 1, wherein the wavelength division multiplexer and the fiber collimator are replaced by a fiber wavelength division multiplexing collimator, and the pump source is connected to the fiber wavelength division multiplexing collimator.
3. The phase-bias based linear cavity mode-locked fiber laser according to claim 1, wherein a dispersion element is disposed between the polarization splitting prism and the high reflection mirror.
4. The phase-bias based linear cavity mode-locked fiber laser according to claim 3, wherein the dispersive element is a grating pair.
5. The phase bias based linear cavity mode-locked fiber laser according to claim 4, wherein the grating density of the grating pairs is in a range of 150 to 2000 lines/mm.
6. The phase-bias based linear cavity mode-locked fiber laser according to claim 1, wherein the polarization-maintaining gain fiber is a large mode area polarization-maintaining fiber, a doped gain polarization-maintaining fiber, a large mode area double-clad polarization-maintaining fiber or a polarization-maintaining photonic crystal fiber.
7. The phase bias based linear cavity mode-locked fiber laser according to claim 1, wherein the faraday rotator is a thin-sheet faraday rotator or a faraday rotator formed by inserting a magneto-optical crystal into a permanent magnet.
8. The phase-bias based linear cavity mode-locked fiber laser of claim 1, wherein the birefringent crystal generates the magnitude of the phase bias
Determined by the nature and thickness of the birefringent crystal, i.e.
Wherein, in the step (A),
is the refractive index of the e-light,
is the refractive index of the o light,lλ is the wavelength, which is the thickness of the birefringent crystal.
9. The phase-bias based linear cavity mode-locked fiber laser according to claim 1, wherein the length of the polarization-maintaining gain fiber is adjustable to adjust the cavity length of the laser by adjusting the length of the polarization-maintaining gain fiber.
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Address after: No. 25 Sanle East Road, Shunjiang Community, Beijiao Town, Shunde District, Foshan City, Guangdong Province, 528311, Building 5, Block A, 701, Integrated Science and Technology Innovation Park Phase 1 (Residence Application) Patentee after: PulseX Laser Technology Co.,Ltd. Address before: No.2-18, Chenggong Road, Fengfeng Industrial Zone, Gujian village, Daliang street, Shunde District, Foshan City, Guangdong Province 528300 Patentee before: Foshan pacos Laser Technology Co.,Ltd. |