WO2019047507A1

WO2019047507A1 - Optical fiber laser

Info

Publication number: WO2019047507A1
Application number: PCT/CN2018/080932
Authority: WO
Inventors: 李程; 郑渚; 杨彬; 徐飞; 丁庆
Original assignee: 深圳市太赫兹科技创新研究院有限公司; 深圳市太赫兹科技创新研究院
Priority date: 2017-09-05
Filing date: 2018-03-28
Publication date: 2019-03-14
Also published as: CN107482429B; CN107482429A

Abstract

An optical fiber laser, comprising a pumping light source (140), a resonant optical circuit (110), a tuning device (120) and a current adjustment device; the pumping light source provides pumping light for the resonant optical circuit; the tuning device is provided on the resonant optical circuit, and the tuning device comprises a grapheme film (121) and a first optical fiber (122), the grapheme film covering the end face of a fiber core on one end of the first optical fiber; and the current adjustment device is connected to the grapheme film, and the current adjustment device is used for energizing the grapheme film and adjusting the current passing through the grapheme film. On one hand, as the current passing through the grapheme film is adjustable, the temperature of the grapheme film is adjustable, and the depth of modulation performed by the tuning device on the laser transmitted therethrough is changed, making the performance of the optical fiber laser tunable. On the other hand, the tuning device is an optical fiber device integrating the first optical fiber and the grapheme film, and therefore, the loss of an optical signal during transmission of same through the tuning device is small, enabling the optical fiber laser to have a better tuning effect.

Description

fiber-optic laser

Technical field

The present invention relates to the field of laser technologies, and in particular, to a fiber laser.

Background technique

Graphene-based fiber lasers have broad prospects in many fields such as optical communication, fiber sensing, detection and diagnosis, biomedicine, precision micromachining, and military, because they can generate ultra-short pulses with high frequency. Graphene is chemically stable, has strong electrical conductivity and light guiding property, and is a novel nano material used as a saturable absorber for fiber laser mode-locking, so that the performance of the fiber laser is better.

If the properties of graphene are tunable, the performance of graphene-based fiber lasers can also be tunable. At present, graphene can be used as a field effect transistor in a fiber laser, and the performance of the graphene can be adjusted by adjusting the gate voltage of the field effect transistor, thereby realizing the performance tuning of the fiber laser. However, graphene-based FETs increase the loss of fiber lasers, resulting in poor tuning of fiber lasers.

Summary of the invention

Based on this, it is necessary to provide a fiber laser for the problem that the tuning effect of the fiber laser is not good in the conventional graphene-based fiber laser.

A fiber laser comprising a pumping source and a resonant optical path; the pumping source providing pumping light to the resonant optical path; wherein the fiber laser further comprises a tuning device and a current regulating device, the tuning device setting In the resonant optical path, the tuning device includes a graphene film covering a end surface of a core of one end of the first optical fiber, and a first optical fiber; the current regulating device is connected to the graphene film The current regulating device is configured to energize the graphene film and regulate current flow through the graphene film.

In the above fiber laser, the tuning device is disposed on the resonant optical path, and the graphene film covers the end face of the core of the first optical fiber, and energizes the graphene film when the resonant cavity operates. On the one hand, the current through the graphene film can be adjusted, and then the temperature of the graphene film can be adjusted, so that the Fermi-Dillac distribution of the graphene film changes, and the tuning device changes the modulation depth of the laser light transmitted through it. This makes the performance of the fiber laser tunable. Moreover, as long as the current through the graphene film is changed, the tuning device can flexibly output the first fiber laser, making the application of the fiber laser wider. On the other hand, the tuning device is composed of a first optical fiber and a graphene film covering the end face of the core at one end of the first optical fiber, that is, the tuning device is a fiber device in which the first optical fiber is integrated with the graphene film, and therefore, the tuning device The optical path of the resonant cavity can be accessed by means of fiber coupling. Thus, the loss of light signals transmitted through the tuning device is small. In summary, the tuning device makes the tuning effect of the fiber laser better.

In one embodiment, the tuning device further includes two electrodes, each of which is coupled to the graphene film to connect the graphene film to the current regulating device.

In one embodiment, the first optical fiber further includes a cladding layer coated on the outside of the core; the core adjacent to the graphene film extends outside the cladding layer to form a protruding end Two of the electrodes are disposed on an end face of the cladding adjacent to the projecting end, and two of the electrodes are separated by the projecting end.

In one embodiment, the two electrodes are all semi-cylindrical, the bottom surfaces of the two electrodes are parallel to the graphene film; the bottoms of the two electrodes are close to the bottom of the graphene film Both are covered by the graphene film.

In one of the embodiments, both of the electrodes are metal electrodes.

In one embodiment, the resonant optical path is a ring resonant optical path; the fiber laser further includes a transmission fiber through which light propagates through the transmission fiber.

In one embodiment, the fiber laser further includes a gain fiber and a first coupling element, the gain fiber is disposed on the resonant optical path, the pump light is incident on the gain fiber, and the gain fiber is pumped a laser is generated by the light, and the laser light emitted from the gain fiber is incident on the tuning device; the first coupling element is disposed on the resonant optical path, and the first coupling element receives the outgoing light of the tuning device The first coupling element is configured to split the received optical signal, wherein an optical signal is emitted as an output laser of the fiber laser to the resonant optical path.

In one embodiment, the first coupling element includes a first output end for splitting the optical signal into two beams, and a second output end as the output laser light from the The first exit end emits, the other optical signal exits through the second exit end, and continues to propagate on the resonant optical path; the fiber laser further includes a second coupling element, the second coupling element is disposed at the On the resonant optical path, the second coupling element receives the pump light and the optical signal of the second exit end, and the second coupling element is configured to combine the pump light and the optical signal emitted by the second exit end The exiting light of the second coupling element is incident on the gain fiber.

In one embodiment, the fiber laser further includes an isolation element having a split ratio of 9:1, and 10% of the optical signal is emitted as an output laser from the first exit end, 90% of An optical signal is emitted through the second exit end.

In one embodiment, the fiber laser further includes an isolation element and a polarization control element, the isolation element being disposed on the optical path of the gain fiber to the tuning device.

In one embodiment, the isolation element is for ensuring unidirectional transmission of light; the polarization control element is disposed on an optical path of the isolation element to the tuning device, and the polarization control element is for adjusting an optical signal The state of polarization.

DRAWINGS

1 is a schematic view of a fiber laser of an embodiment;

2 is a schematic structural view of the tuning device shown in FIG. 1.

Detailed ways

The above described objects, features and advantages of the present invention will become more apparent from the aspects of the appended claims.

FIG. 1 is a schematic view of a fiber laser 100 of the present embodiment. As shown in FIG. 1, a fiber laser 100 includes a resonant optical path 110, a tuning device 120, and a current regulating device (not shown). The tuning device 120 is disposed on the resonant optical path 110, and the tuning device 120 includes a graphene film (not shown in FIG. 1) and a first optical fiber (not shown in FIG. 1). In this embodiment, the first optical fiber is a single mode optical fiber. The graphene film covers the end face of the core at one end of the first fiber. A current regulating device is coupled to the graphene film, and the current regulating device is used to energize the graphene film and regulate the current through the graphene film.

Specifically, the Fermi-Dirac distribution of graphene is:

In the formula (1), k _B is a Boltzmann constant, E is the energy of the quantum state of graphene, E _f is the chemical potential of graphene, and T is the temperature of graphene. For graphene, E and E _f are constant, so the temperature of graphene determines its Fermi Dillac distribution. The optical conductivity or saturable absorption characteristics of graphene are determined by the Fermi Dirac distribution. Therefore, the optical conductivity or the saturable absorption characteristic of the graphene can be changed by changing the temperature, that is, the purpose of tuning the graphene performance can be achieved by changing the temperature.

The graphene film has electrical resistance, and due to the ohmic effect, the graphene film generates heat when energized, so that the temperature of the graphene film rises. Further, by changing the current passing through the graphene film, the temperature of the graphene film can be changed, so that the optical conductivity or the saturable absorption property of the tuned graphene can be achieved.

In the present embodiment, the tuning device 120 mainly achieves the purpose of tunable the output laser of the fiber laser 100 by tuning the performance of the graphene. In particular, the current of the graphene film can be adjusted to allow the temperature of the graphene film to be adjusted such that the tuning device 120 can achieve an output laser tunability of the fiber laser 100.

In the above fiber laser 100, the tuning device 120 is disposed on the resonant optical path 110 to connect the tuning device 120 to the resonant optical path 110. And the graphene film covers the end faces of the core of the first optical fiber. When the resonant optical path 110 is operating, the current regulating device energizes the graphene film and regulates the current through the graphene film. On the one hand, the current through the graphene film is adjustable, and then the temperature of the graphene film is adjustable, so that the Fermi-Dillac distribution of the graphene film changes, and thus the modulation depth of the tuning device 120 for the laser light transmitted therethrough is changed. Thus, the performance of the fiber laser 100 is tunable. Moreover, by varying the magnitude of the current through the graphene film, the tuning device 120 can flexibly output the output of the first fiber laser 100, making the fiber laser 100 more widely applicable. For example, when the current through the graphene film is 0 A (amperes), the modulation depth of the laser of the tuning device 120 is 2.3%, and the mode locking of the fiber laser 100 can be realized, and the pulse laser with a large output line width can be applied to the laser processing. Technical field. When the current through the graphene film is adjusted to 9 A, the temperature of the graphene film is increased, the modulation depth of the tuning device 120 to the laser is 0.9%, and the tuning device 120 has almost no mode-locking effect on the laser, so the output of the fiber laser 100 is A continuous laser, which is a monochromatic laser with a small line width, can be applied to the field of communication. On the other hand, the tuning device 120 is composed of a first optical fiber and a graphene film covering the end face of the core at one end of the first optical fiber, that is, the tuning device 120 is a fiber device in which the first optical fiber is integrated with the graphene film, and therefore, The tuning device 120 can be connected to the resonant optical path 110 by means of fiber coupling. Thus, the loss of light signals transmitted through the tuning device 120 is small. In summary, the tuning device 120 makes the tuning effect of the fiber laser 100 better.

It should be noted that the propagation of an optical signal from one device to another means that the optical signal propagates directly from one device to another, or the optical signal is emitted by one device and propagates through the intermediate device to another device.

This embodiment takes an all-fiber laser as an example, that is, each device in the fiber laser 100 is a fiber component. The resonant optical path 110 is a ring-shaped resonant optical path, and the optical fiber elements are integrated by the optical fiber to form the whole resonant optical path 110. In this embodiment, the resonant optical path 110 where each optical fiber element is located constitutes an optical resonant cavity and is a ring-shaped resonant cavity. This structure not only makes the structure of the fiber laser 100 simple, compact, and maintenance-free, but also has high coupling efficiency of pump light.

The fiber laser 100 also includes a transmission fiber (not shown) through which light propagates through the transmission fiber. Specifically, each of the fiber optic components is fused to the transmission fiber to achieve an all-fiber transmission of the optical signal. Further, the transmission fiber is a single mode fiber. For example, in this embodiment, the transmission fiber can be a single mode fiber of Corning SMF-28, and has a length of about 60 m.

In this embodiment, the fiber laser 100 further includes a pumping source 140 and a gain fiber 150. The pumping source 140 provides pumping light to the resonant beam path 110. For example, pump source 140 is a semiconductor laser diode having a wavelength of 980 nm. The gain fiber 150 is disposed on the resonant optical path 110, and the pump light emitted from the pump light source 140 is incident on the gain fiber 150. The gain medium 150 contains a working medium of a laser. Under the action of the pump light, electrons in the working medium are excited to a higher excitation level, thereby realizing ion number reversal. In order to transfer from the high energy level to the ground state, the inverted particles radiate photoelectrons outward to form a laser. The working medium may be a rare earth ion, that is, the gain fiber 150 is an optical fiber doped with rare earth ions, such as an erbium doped fiber, a doped fiber, or the like. In this embodiment, the gain fiber 150 is a doped fiber. The gain fiber 150 is a doped fiber using OFS EDF80 and has a length of about 1.2 m. The wavelength of the laser light formed by the pump light passing through the gain fiber 150 is 1550 nm. The laser light emitted from the gain fiber 150 is incident on the tuning device 120, and the tuning device 120 tunes the laser.

The fiber laser 100 further includes a first coupling element 160 disposed on the resonant optical path 110, the first coupling element 160 receiving the outgoing light of the tuning device 120. The first coupling element 160 is used to split the optical signal to achieve optical signal power distribution among different transmission fibers. One of the optical signals split by the first coupling element 160 is emitted as an output laser of the fiber laser 100 to the outside of the resonant optical path 110. In this embodiment, the first coupling element 160 is a fiber coupler. The first coupling element 160 includes a first exit end and a second exit end. The first coupling element 160 is configured to split the received optical signal into two beams, wherein one of the optical signals is emitted as the output laser from the first output end, and the other optical signal is emitted through the second output end, and continues Propagating on the resonant optical path. Specifically, the first coupling element 160 has a split ratio of 9:1, 10% of the optical signal is emitted as an output laser from the first exit end, and 90% of the optical signal is emitted through the second exit end. The optical signal of the second exit end continues to propagate on the resonant optical path 110 to cause the fiber laser 100 to operate stably to output the laser light.

The fiber laser 100 further includes a second coupling element 170 disposed on the resonant optical path 110, and the second coupling element 170 is disposed on the optical path of the first coupling element 160 to the gain fiber 150. That is, the second coupling element 170 receives the light signal of the pump light and the second exit end, and the second coupling element 170 is used to combine the pump light and the optical signal emitted by the second exit end, the second coupling element 170 The outgoing light is incident on the gain fiber 150. In this way, the pump light and the optical signal emitted from the second exit end can be simultaneously transmitted in the transmission fiber to improve the transmission efficiency. It is also possible to couple the pump light into the gain fiber 150. In this embodiment, the second coupling element 170 is a wavelength division multiplexer.

It should be noted that, in other embodiments, the first coupling element 160 is not limited to a fiber coupler, and may be other devices having functions similar to those of a fiber coupler. The second coupling element 170 is not limited to a wavelength division multiplexer, but may be other devices having functions similar to those of a wavelength division multiplexer.

The fiber laser 100 further includes an isolation element 180 disposed on the optical path of the gain fiber 150 to the tuning device 120 for ensuring unidirectional transmission of light. Specifically, after the pump light passes through the gain fiber 150, laser light in multiple directions may be generated, and the isolation element 180 is disposed on the optical path of the gain fiber 150 to the tuning device 120, so that the isolation element 180 can select an optical signal propagating in a predetermined direction. It is incident on the tuning device 120 to ensure unidirectional propagation of the pulsed laser, so that the performance of the fiber laser 100 is better. In this embodiment, isolation element 180 is a polarization independent isolator.

Fiber laser 100 also includes a polarization control element 190. Polarization control element 190 is disposed on the optical path of isolation element 180 to tuning device 120, and polarization control element 190 is used to adjust the polarization state of the optical signal. The polarization control element 190 receives the outgoing light of the isolation element 180 and controls the polarization state of the received optical signal, thereby controlling the polarization state of the output laser such that the polarization state of the output laser satisfies the demand. In this embodiment, the polarization control element 190 can employ a fiber polarization controller such that the polarization control element 190 is very easy to access to an all-fiber system.

Tuning device 120 receives the outgoing light of polarization control element 190 and tunes the received optical signal. Since the pump light is incident on the gain fiber 150, a laser has been generated in the gain fiber 150, and the laser light is transmitted through the transmission fiber and transmitted to the first fiber through the isolation element 180 and the polarization control element 190, respectively, and thus the optical signal received by the first fiber. For the laser. The tuning device 120 tunes the laser to achieve tunability of the output laser of the fiber laser 100.

In the above fiber laser 100, the optical signal of the pumping source 140 to the second coupling element 170, the optical signal of the second coupling element 170 to the gain fiber 150, the optical signal of the gain fiber 150 to the isolation element 180, and the isolation element 180 to polarization control The optical signal of the component 190, the optical signal of the polarization control component 190 to the tuning device 120, the optical signal of the tuning device 120 to the first coupling component 160, and the optical signals of the first coupling component 160 to the second coupling component 170 are transmitted through a transmission fiber. . Thus, the optical signal loss is small and the transmission efficiency is high.

FIG. 2 is a schematic structural view of the tuning device 120 shown in FIG. 1. As shown in FIG. 2, the tuning device 120 includes a graphene film 121 and a first optical fiber 122. The first optical fiber includes a core 122A and a cladding 122B that is coated on the outside of the core. The graphene film 121 covers the end surface of the core 122A at one end of the first optical fiber 122. In tuning device 120, tuning device 120 also includes two electrodes, electrode 1 and electrode 2. The electrode 1 and the electrode 2 are respectively connected to the graphene film 121 to connect the graphene film 121 to the current regulating device. Since the graphene film 121 is thin and is not easily directly connected to the power source, after the graphene film 121 and the two electrodes are respectively connected, as long as the electrode 1 and the electrode 2 are connected to the current regulator, there is a graphene film 121. Current is passed. This makes it easy to connect the graphene film 121 to the power source, and stably connects the power source through the two electrodes.

Specifically, the core 122A of the first optical fiber 122 near the graphene film 121 extends beyond the cladding 122B of the first optical fiber 122 to form an extended end. Two electrodes are disposed on the end faces of the cladding 122B near the projecting end, and the two electrodes are separated by the projecting ends. Thus, by integrating the two electrodes on the first optical fiber 122 and separating the two electrodes by the projecting end of the core 122A, the structure of the tuning device 120 can be made simple and compact.

In this embodiment, the shapes of the two electrodes are all semi-cylindrical, and the bottom surfaces of the two electrodes are parallel to the graphene film 121. The bottoms of the two electrodes adjacent to the graphene film 121 are covered by the graphene film 121 to connect the graphene film 121 and the two electrodes, respectively. Thus, the graphene film 121 can be connected to the two electrodes as long as it is in contact with the two electrodes, and the connection between the graphene film 121 and the two electrodes is simple.

Further, both electrodes are metal electrodes. The metal electrode has a high conductivity. Thus, energizing the graphene film 121 by the metal electrode can make the current loss through the graphene film 121 small, so that the tuning of the fiber laser 100 by the tuning device 120 is accurate.

The technical features of the above-described embodiments may be arbitrarily combined. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be considered as the scope of this manual.

The above-described embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A fiber laser comprising a pumping source and a resonant optical path; the pumping source providing pumping light to the resonant optical path; wherein the fiber laser further comprises a tuning device and a current regulating device, the tuning device setting In the resonant optical path, the tuning device includes a graphene film covering a end surface of a core of one end of the first optical fiber, and a first optical fiber; the current regulating device is connected to the graphene film The current regulating device is configured to energize the graphene film and regulate current flow through the graphene film.
The fiber laser according to claim 1, wherein said tuning device further comprises two electrodes, said two electrodes being respectively connected to said graphene film to connect said graphene film to said current Adjust the device.
The fiber laser according to claim 2, wherein said first optical fiber further comprises a cladding coated on an outer portion of said core; said core adjacent said graphene film extending to said cladding In addition, a projecting end is formed; two of the electrodes are disposed on an end face of the cladding adjacent to the projecting end, and two of the electrodes are separated by the projecting end.
The fiber laser according to claim 3, wherein both of said electrodes are in the shape of a semi-cylindrical body, and bottom surfaces of said two electrodes are parallel to said graphene film; The bottom of the graphene film is covered by the graphene film.
A fiber laser according to claim 4, wherein both of said electrodes are metal electrodes.
The fiber laser according to claim 1, further comprising a gain fiber and a first coupling element, wherein the gain fiber is disposed on the resonant optical path, and the pump light is incident on the gain fiber, the gain fiber Generating a laser light under the action of pump light, the laser light emitted by the gain fiber is incident on the tuning device; the first coupling element is disposed on the resonant optical path, and the first coupling element receives the tuning device The outgoing light is used to split the received optical signal, wherein a light signal is emitted as an output laser of the fiber laser to the resonant optical path.
A fiber laser according to claim 6, wherein said first coupling element comprises a first exit end and a second exit end, said first coupling element for splitting the optical signal into two beams, wherein the light is split a signal is emitted from the first exit end as an output laser, and another light signal is emitted through the second exit end and continues to propagate on the resonant optical path; the fiber laser further includes a second coupling element, a second coupling element is disposed on the resonant optical path, the second coupling element receives an optical signal of the pump light and the second exit end, and the second coupling element is configured to pump light and the second exit The optical signals exiting the ends are combined, and the outgoing light of the second coupling element is incident on the gain fiber.
The fiber laser according to claim 7, wherein the first coupling element has a split ratio of 9:1, and 10% of the optical signal is emitted as an output laser from the first exit end, and 90% of the optical signal Exiting through the second exit end.
A fiber laser according to claim 6, further comprising an isolating member disposed on an optical path of said gain fiber to said tuning device, said isolating member for ensuring one-way transmission of light .
A fiber laser according to claim 9, further comprising a polarization control element disposed on an optical path of said isolation element to said tuning device, said polarization control element for adjusting an optical signal The state of polarization.