All-fiber space-time mode-locking double-optical-comb laser and system

Abstract

The invention provides an all-fiber space-time mode-locking double-optical-comb laser and system, and the laser comprises a wavelength division multiplexer, an output coupler, a space-time mode-locking device, a polarization controller, an isolator and a gain optical fiber which are sequentially connected through a multimode optical fiber, and is used for generating space-time mode-locking double-optical-comb laser. Wherein the output coupler is used for outputting laser, the space-time mode locking device is used for modulating the laser, and the polarization controller is used for adjusting and optimizing a polarization state; the isolator is used for ensuring the unidirectivity of laser operation; the gain optical fiber is used for generating and maintaining space-time mode-locked double-optical-comb laser; an external light source can be connected with the wavelength division multiplexer directly or through a mode field matcher to form an all-fiber space-time mode locking double-optical-comb system. The space-time mode-locked double-optical comb based on mode multiplexing can be generated, and the space-time mode-locked double-optical comb is simple in structure, large in output power and suitable for the fields of precision measurement, optical communication, spectral analysis and the like.

Description

(I) Technical field

[0001] The invention relates to the field of laser technology, and in particular to an all-fiber spatiotemporal mode-locked dual-comb laser and system. (II) Background technology

[0002] The optical frequency comb is a special laser light source that appears as a series of spectral lines with equal frequency intervals in the frequency domain and as optical pulses with equal time intervals in the time domain. The dual optical comb system consists of two optical frequency combs with different repetition frequencies. The outputs of the two optical frequency combs are highly coherent and have a repetition frequency difference. Therefore, the signal generated after the beat is converted from the high-frequency optical frequency domain to the low-frequency radio frequency domain. Therefore, the dual optical comb system can connect the optical frequency domain and the radio frequency domain, and quickly reflect the information obtained from the optical frequency domain detection in the radio frequency domain. At present, spectral detection in the optical frequency domain is more difficult and more expensive than that in the radio frequency domain. The use of dual optical combs can resolve optical frequency information from the radio frequency domain, which has significant advantages in the fields of precision measurement, optical communication, and spectral analysis.

[0003] Optical frequency combs can usually be obtained through mode-locked lasers. In general lasers, the oscillations of the longitudinal modes are independent of each other, and there is no definite relationship between their phases. Affected by frequency pulling and frequency repulsion, the frequency intervals of adjacent longitudinal modes are not strictly equal. However, the frequency intervals between the oscillation modes output by the mode-locked laser remain constant and have a definite phase relationship. The output frequency domain is a series of spectral lines with equal frequency intervals, which can be used as an optical frequency comb after proper stabilization processing. In a dual-comb system, it is necessary to enable the two optical frequency combs of the dual-comb system to be coherently averaged for a long time to improve the signal-to-noise ratio of the interference signal, so it is necessary to improve the mutual coherence of the two optical frequency combs.

[0004] In order to generate two sets of optical frequency combs with high mutual coherence at a lower cost, the concept of single-cavity dual optical combs was proposed. Single-cavity dual optical combs use one laser to generate two sets of optical combs, which can be mainly classified into wavelength multiplexing, direction multiplexing, polarization multiplexing, etc. based on their formation mechanism. These two sets of optical combs have natural mutual coherence because they are generated from the same laser while having a repetition frequency difference, making single-cavity dual optical combs an important way to generate dual optical combs.

[0005] The output of dual-comb pulses has been widely studied only in single-mode lasers. There are multiple transverse modes in multimode optical fibers, and the modes will affect each other during transmission. It is also of great significance to study the various complex phenomena in multimode lasers that are generated by utilizing this characteristic. Furthermore, combining multimode optical fibers with the output of dual-comb asynchronous mode-locked pulses can also provide new ideas for the realization of dual-combs. In multimode fiber lasers, the situation in which the longitudinal mode and the transverse mode of the laser are locked at the same time is called space-time mode locking. The characteristics of space-time mode locking match the concept of dual-combs. When different modes in space-time mode locking are locked into two groups with a small repetition frequency difference, a mode-division multiplexed dual-comb is generated. The invention of all-fiber space-time mode-locked dual-comb lasers and systems provides new ideas for the realization of dual-combs. (III) Summary of the invention

[0006] In view of this, an object of the present invention is to provide an all-fiber spatiotemporally mode-locked dual-comb laser and system.

[0007] In a first aspect, an embodiment of the present invention provides an all-fiber space-time mode-locked dual-comb laser, characterized in that the system includes a wavelength division multiplexer, an output coupler, a space-time mode-locked device, a polarization controller, an isolator, and a gain fiber connected in sequence by a multimode optical fiber, for generating a space-time mode-locked dual-comb laser; wherein the wavelength division multiplexer is used to couple pump light into the space-time mode-locked dual-comb laser; and the output coupler is used to output the space-time mode-locked dual-comb laser. The space-time mode-locked device is used to modulate the space-time mode-locked dual-comb laser; the polarization controller is used to adjust and optimize the polarization state in the space-time mode-locked dual-comb laser; the isolator is used to ensure the unidirectionality of the laser running in the space-time mode-locked dual-comb laser; the gain fiber is used to absorb pump light and use the energy of the pump light to amplify and maintain the space-time mode-locked dual-comb laser, wherein, according to the requirements of the laser band, the gain fibers that can be used include erbium-doped fiber, ytterbium-doped fiber, thulium-doped fiber, erbium-ytterbium co-doped fiber, thulium-holmium co-doped fiber, thulium-doped fluoride fiber, and ZBLAN fiber; the output coupler, space-time mode-locked device, polarization controller, and isolator pigtail are all multimode fibers.

[0008] In combination with the first aspect, an embodiment of the present invention provides a first possible implementation manner of the first aspect, wherein the mode-locked device includes: the active mode-locked device is an electro-optic modulation device or an acousto-optic modulation device; the equivalent saturable absorber is a nonlinear polarization rotation device, a nonlinear fiber loop mirror or a nonlinear amplifying loop mirror; the natural saturable absorber is a dye, a semiconductor saturable absorber mirror, graphene, carbon nanotubes, topological insulators, transition metal chalcogenides, black phosphorus, metal and its oxide nanomaterials, transition metal carbon / nitrogen / carbon nitrides, metasurface materials or composite materials formed by the above-mentioned natural saturable absorber materials.

[0009] In a second aspect, an embodiment of the present invention provides an all-fiber space-time mode-locked dual-comb system, wherein the all-fiber space-time mode-locked dual-comb system comprises an external pump light source and the all-fiber space-time mode-locked dual-comb laser described in the first aspect, which are connected in sequence.

[0010] In combination with the second aspect, an embodiment of the present invention provides a first possible implementation method of the second aspect, wherein the external pump light source is a single-mode or multi-mode laser diode, a continuous light laser or a pulsed laser, wherein the external pump light source can be connected to the wavelength division multiplexer directly or through a mode field matcher; the mode field matcher is used to broaden the mode field in the external pump light source pigtail and match it with the mode field in the wavelength division multiplexer pigtail. (IV) Description of the drawings

[0011] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1 A schematic diagram of the structure of an all-fiber spatiotemporally mode-locked dual-comb laser provided by an embodiment of the present invention;

[0013] Figure 2 A schematic structural diagram of an all-fiber spatiotemporal mode-locked dual-comb system provided in an embodiment of the present invention.

[0014] Icon: 100-wavelength division multiplexer; 110-output coupler; 120-saturable absorber; 130-polarization controller; 140-isolator; 150-gain fiber; 161-pump light source; 162-mode field matcher. (V) Specific implementation methods

[0015] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are 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.

[0016] At present, the existing single-cavity dual-comb system usually generates dual-comb output based on wavelength multiplexing, direction multiplexing or polarization multiplexing, and the output power is limited by the single-mode fiber. Based on this, the embodiment of the present invention provides an all-fiber spatiotemporal mode-locked dual-comb laser and system, in which the laser cavity loop is mainly a multimode fiber, which can generate higher power output without adding an amplifier, which is beneficial to subsequent measurement applications.

[0017] To facilitate understanding of this embodiment, firstly, an all-fiber spatiotemporal mode-locked dual-comb laser disclosed in an embodiment of the present invention is described in detail, see Figure 1 Schematic diagram of an all-fiber spatiotemporally mode-locked dual-comb laser.

[0018] like Figure 1 As shown, the laser includes a wavelength division multiplexer 100, an output coupler 110, a time-space mode-locking device 120, a polarization controller 130, an isolator 140, and a gain fiber 150, which are sequentially connected into a ring structure through a multimode optical fiber.

[0019] The gain fiber 150 is used to absorb the pump light and use the energy of the pump light to amplify and maintain the spatiotemporal mode-locked dual-comb laser, wherein the gain fiber can be erbium-doped fiber (Er-doped fiber), ytterbium-doped fiber (Yb-doped fiber), thulium-doped fiber (Tm-doped fiber), erbium-ytterbium co-doped fiber (Er / Yb-codoped fiber), thulium-holmium co-doped fiber (Tm / Ho-codoped fiber), thulium-doped fluoride fiber (Tm-doped fluoride fiber), ZBLAN fiber (ZBLAN fiber). Lasers of different wavelengths can be generated using different gain fibers. Generally, when there is no mode-locking device or equivalent mode-locking effect in the laser cavity, the laser cavity containing the gain fiber can generate a continuous laser with a wavelength consistent with the gain fiber based on the pump light.

[0020] The spatiotemporal mode-locking device 120 is used to modulate the spatiotemporal mode-locked dual-comb laser. The mode-locking device includes an active mode-locking device, an equivalent saturable absorber or a natural saturable absorber, wherein the active mode-locking device is an electro-optical modulation device or an acousto-optic modulation device; the equivalent saturable absorber is a nonlinear polarization rotation device, a nonlinear optical loop mirror or a nonlinear amplifying loop mirror; the natural saturable absorber is a dye, a semiconductor saturable absorber mirror, graphene, carbon nanotubes, topological insulators, transition metal chalcogenides, black phosphorus, metal and oxide nanomaterials, transition metal carbon / nitrogen / carbon nitrides or a composite material composed of the above natural saturable absorber materials.

[0021] The wavelength division multiplexer 100 (Wavelength division multiplexer) is used to couple the pump light into the space-time mode-locked dual-comb laser; the polarization controller 130 (Polarization controller) is used to adjust and optimize the polarization state in the space-time mode-locked dual-comb laser; the isolator 140 (Isolator) is used to ensure the unidirectionality of the laser in the space-time mode-locked dual-comb laser; the output coupler 110 (Output coupler) is used to finally output the space-time mode-locked dual-comb laser.

[0022] When the laser is connected to a pump light source, the laser output by the pump light source will enter the gain fiber 150. The doped ions inside the gain fiber 150 absorb the pump laser, enter an excited state, and emit lasers of the desired wavelength to both ends of the gain fiber through stimulated radiation. When the two laser beams encounter the isolator 140, the laser beam in the direction consistent with the isolator 140 will continue to propagate, while the laser beam in the opposite direction will be isolated. The laser beams in the remaining directions will continuously propagate in the ring-structured laser, where they will be amplified after passing through the gain fiber 150, and gradually modulated into longitudinal mode-locked pulsed laser beams after passing through the spatiotemporal mode-locking device 120. Furthermore, adjusting the polarization controller 130 can promote the locking of the transverse mode by causing a slight deformation of the laser. When different modes are locked into two groups with a slight repetition frequency difference, a dual-comb of mode division multiplexing is generated.

[0023] Next, an all-fiber spatiotemporal mode-locked dual-comb system disclosed in an embodiment of the present invention is described in detail. Figure 2 Schematic diagram of an all-fiber spatiotemporal mode-locked dual-comb system.

[0024] like Figure 2As shown, in Figure 1 On the basis of the all-fiber spatiotemporally mode-locked dual-comb laser shown, a pump light source 161 and a mode field matcher 162 are added. The pump light source 161 is a single-mode or multi-mode laser diode, a continuous light laser or a pulsed laser, which is connected to the laser through a mode field matcher 162 to provide pump light for the laser. The mode field matcher 162 is used to broaden the mode field in the pigtail of the external pump light source and match it with the mode field in the pigtail of the wavelength division multiplexer. When the mode number of the pump light source matches the mode number accommodated by the multimode optical fiber, the pump light source 161 can be directly connected to the laser without passing through the mode field matcher.

[0025] For this system, the pump power of the pump light source 161 is gradually increased, and the laser system will output continuous wave laser from the output coupler 110. Further increase the pump power and adjust the polarization controller 130, and the laser system will output spatiotemporally mode-locked dual-comb laser from the output coupler 110.

[0026] In summary, the present invention provides an all-fiber spatiotemporally mode-locked dual-comb laser and system, which can generate higher power output without adding an amplifier, which is beneficial for subsequent measurement applications.

[0027] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the real-time switching method of laser pulse types described above can refer to the corresponding device in the aforementioned embodiment and will not be repeated here.

[0028] In addition, in the description of the embodiments of this patent, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 this patent can be understood according to specific circumstances.

[0029] In the description of this patent, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this patent and simplifying the description, rather than indicating or implying 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 a limitation of this patent. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0030] Finally, it should be noted that the above-mentioned embodiments are only specific implementation methods of this patent, which are used to illustrate the technical solution of this patent, rather than to limit it. The protection scope of this patent is not limited to this. Although this patent is described in detail with reference to the above-mentioned embodiments, ordinary technicians in this field should understand that any technician familiar with this technical field can still modify the technical solution recorded in the above-mentioned embodiments within the technical scope disclosed by this patent, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiment of this patent, and should be covered within the protection scope of this patent. Therefore, the protection scope of this patent should be based on the protection scope of the claims.

Claims

1. An all-fiber spatiotemporally mode-locked dual-comb laser, characterized in that: The system includes a wavelength division multiplexer, an output coupler, a time-space mode-locking device, a polarization controller, an isolator, and a gain fiber connected in sequence by a multimode optical fiber, and is used to generate a time-space mode-locked dual-comb laser; Wherein, the wavelength division multiplexer is used to couple the pump light into the spatiotemporally mode-locked dual-comb laser; The output coupler is used to output the spatiotemporally mode-locked dual-comb laser; The space-time mode-locked device is used to modulate the space-time mode-locked dual-comb laser; The polarization controller is used to adjust and optimize the polarization state in the spatiotemporally mode-locked dual-comb laser; The isolator is used to ensure the unidirectionality of the laser running in the spatiotemporal mode-locked dual-comb laser; The gain fiber is used to absorb the pump light and use the energy of the pump light to amplify and maintain the spatiotemporally locked dual-comb laser. According to the requirements of the laser band, the gain fiber that can be used includes erbium-doped fiber, ytterbium-doped fiber, thulium-doped fiber, erbium-ytterbium co-doped fiber, thulium-holmium co-doped fiber, thulium-doped fluoride fiber, and ZBLAN fiber. The output coupler, the spatiotemporal mode locking device, the polarization controller and the isolator pigtail are all multimode optical fibers.

2. The method according to claim 1, characterized in that: The spatiotemporal mode-locking device comprises an active mode-locking device, an equivalent saturable absorber or a natural saturable absorber; Wherein, the active mode locking device is an electro-optic modulation device or an acousto-optic modulation device; The equivalent saturable absorber is a nonlinear polarization rotation device, a nonlinear optical fiber loop mirror or a nonlinear amplifying loop mirror; The natural saturable absorber is a dye, a semiconductor saturable absorber mirror, graphene, a carbon nanotube, a topological insulator, a transition metal chalcogenide, black phosphorus, a metal and its oxide nanomaterial, a transition metal carbon / nitrogen / carbonitride, a supersurface material or a composite material formed by the above natural saturable absorber materials.

3. An all-fiber tunable spatiotemporal mode-locking system, characterized in that: The invention comprises an external pump light source and an all-fiber spatiotemporally mode-locked dual-comb laser as claimed in any one of claims 1 and 2 which are connected in sequence.

4. The method according to claim 1, characterized in that: The external pump light source is a single-mode or multi-mode laser diode, a continuous light laser or a pulsed laser, wherein the external pump light source can be connected to the wavelength division multiplexer directly or through a mode field matcher; the mode field matcher is used to broaden the mode field in the external pump light source pigtail and match it with the mode field in the wavelength division multiplexer pigtail.

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