A mamyshev fiber oscillator based on single and dual channel filters

Abstract

The application discloses a Mamyshev optical fiber oscillator based on single-channel and double-channel filters, and aims to solve the technical problem that the output pulse peak power and energy of a conventional Mamyshev oscillator are limited due to the use of only a single-channel filter in a cavity. The optical fiber oscillator system adopts a ring cavity structure and is composed of a Mamyshev regenerator based on a single-channel optical fiber filter and a Mamyshev regenerator based on a double-channel optical fiber filter in series. The application has the advantages of simple structure, compactness and good stability. By changing the pump power, the output pulse peak power and energy of the oscillator can be increased by 2.8-3.6 times and 2.7-3.1 times, respectively, compared with a conventional Mamyshev oscillator based on two single-channel filters. In application, the oscillator can be directly used as a high-energy ultrashort pulse light source.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser, and particularly relates to a design of a Mamyshev fiber oscillator based on single-channel and double-channel filters. BACKGROUND

[0002] The mode-locked pulse fiber laser is widely used in basic scientific research, high-speed optical communication, micro-machining, ultrafast laser spectroscopy and precision measurement, etc. due to the output pulse with extremely narrow pulse width, high peak power and high energy.

[0003] Generally, the saturable absorber (SA) is used to realize the passive mode-locking of the fiber laser. At present, the commonly used SA is divided into two types: one is the material SA, such as graphene and black phosphorus; and the other is the equivalent SA, such as nonlinear amplifying loop mirror. The damage threshold of the material SA is low, which limits the generation of high peak power and large energy mode-locked pulses; and the transmittance curve of the equivalent SA usually presents a sinusoidal function relative to the peak power of the incident pulse, which means that the in-cavity pulse will be affected by the peak power clamping effect, thus being not conducive to the generation of pulses with extremely high peak power.

[0004] In order to obtain pulses with higher energy and peak power, researchers have proposed a new type of ultra-short pulse fiber laser source, i.e. Mamyshev oscillator. Generally, the Mamyshev oscillator is composed of two Mamyshev regenerators with different filter center wavelengths in series, and its mode-locking mechanism combines the spectral broadening caused by self-phase modulation (SPM) and the spectral bias filtering effect, so that the high peak power pulse can obtain sufficient spectral broadening, thereby passing through the filter with a central wavelength bias. This process realizes the saturable absorption related to the peak power of the pulse. At present, the conventional Mamyshev oscillator is composed of Mamyshev regenerators based on single-channel fiber filters. Although this structure can realize the output of pulses with high peak power and large energy, it also has obvious limitations: the in-cavity single-channel filter with small filter bandwidth inevitably leads to large energy loss, thus limiting the improvement of the energy and peak power of the output pulse. In theory, increasing the bandwidth of the bandpass filter can improve this problem, but in experiments, the increase of the filter bandwidth may cause the overlapping of the filtering ranges of the two bias filters. This overlapping is not conducive to the generation of high peak power pulses, and on the other hand, it is easy to cause the laser to lose lock. In order to solve the above problems, it is necessary to develop a new type of Mamyshev oscillator with filter structure.

[0005] Therefore, we propose a Mamyshev fiber oscillator based on single-channel and double-channel filters to more efficiently realize the output of mode-locked pulses with high peak power and large energy, which will have broad application prospects in the fields of basic scientific research, micro-machining, etc. SUMMARY

[0006] The technical problem to be solved by the present application is to solve the technical problem that the output pulse peak power and energy promotion of the conventional Mamyshev oscillator is limited due to the use of only a single-channel filter in the cavity.

[0007] The technical scheme of the present application is as follows: a Mamyshev fiber oscillator based on a single-channel and double-channel filter, comprising the following devices: a first ordinary single-mode optical fiber, a first pump source, a first wavelength division multiplexer, a first erbium-doped gain optical fiber, a first optical isolator, a single-channel fiber filter, a second ordinary single-mode optical fiber, an output coupler, a second pump source, a second wavelength division multiplexer, a second erbium-doped gain optical fiber, a second optical isolator, and a double-channel fiber filter.

[0008] The first ordinary single-mode optical fiber, the first wavelength division multiplexer, the first erbium-doped gain optical fiber, the first optical isolator, and the single-channel fiber filter are connected in sequence; the first pump source is connected with the input end of the first wavelength division multiplexer; the above devices form a Mamyshev regenerator based on a single-channel fiber filter, marked as Arm1; the second ordinary single-mode optical fiber, the output coupler, the second wavelength division multiplexer, the second erbium-doped gain optical fiber, the second optical isolator, and the double-channel fiber filter are connected in sequence; the second pump source is connected with the input end of the second wavelength division multiplexer; the above devices form a Mamyshev regenerator based on a double-channel fiber filter, marked as Arm2; the Arm1 and the Arm2 are both used for realizing pulse spectrum widening and filtering based on the self-phase modulation effect, and they are connected in series to form a Mamyshev fiber oscillator based on a single-channel and double-channel filter, which is used for realizing high-energy and high-peak-power mode-locked pulse output.

[0009] Preferably, the first pump source and the second pump source are both semiconductor lasers, and the center wavelengths of the output pump light of the semiconductor lasers are both 980 nm.

[0010] Preferably, the first ordinary single-mode optical fiber and the second ordinary single-mode optical fiber are both single-mode optical fibers of the same type, and the lengths of the single-mode optical fibers are both 2 m, and the dispersion coefficients of the single-mode optical fibers at 1550 nm are both -23 ps 2 / km.

[0011] Preferably, the first wavelength division multiplexer and the second wavelength division multiplexer are both fusion-taper-type wavelength division multiplexers of the same type, and the working wavelengths of the wavelength division multiplexers are both 980 / 1550 nm.

[0012] Preferably, the first erbium-doped gain optical fiber and the second erbium-doped gain optical fiber are both gain optical fibers of the same type, and the lengths of the gain optical fibers are both 1 m, and the dispersion coefficients of the gain optical fibers at 1550 nm are both 28 ps 2 / km.

[0013] Preferably, the first optical isolator and the second optical isolator are both polarization independent fiber isolators of the same model, with a central wavelength of 1550 nm and a 3dB bandwidth of 20 nm.

[0014] Preferably, the single-channel fiber filter has a central wavelength of 1550 nm and a 3dB bandwidth of 5 nm.

[0015] Preferably, the two filter channels of the dual-channel fiber filter have central wavelengths of 1537 nm and 1563 nm respectively, and both have a 3dB bandwidth of 5 nm.

[0016] The present application has the following advantages:

[0017] (1) The devices used in the present application are all commercially available, which makes the method of the present application easy to implement;

[0018] (2) The present application adopts an all-fiber structure, has high coupling efficiency, good beam quality, and good heat dissipation;

[0019] (3) The present application has the advantages of simple and compact structure, simple debugging, high stability, etc. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The present application provides a Mamyshev fiber oscillator based on single-channel and dual-channel filters.

[0021] Figure 2 The figure shows the time-domain shape of the output mode-locked pulse of the Mamyshev fiber oscillator based on single-channel and dual-channel filters. It can be seen that the pulse width is 172 fs and the peak power is 188.9 W.

[0022] Figure 3 The figure shows the time-domain shape of the output mode-locked pulse of a conventional Mamyshev fiber oscillator based on two single-channel filters. It can be seen that the pulse width is 297 fs and the peak power is 52.9 W, which is significantly lower than the peak power of the output pulse of the Mamyshev fiber oscillator based on single-channel and dual-channel filters.

[0023] Figure 4 The figure shows the ratio of the peak power of the output pulse of the Mamyshev fiber oscillator of the present application to that of the conventional Mamyshev oscillator with respect to the gain saturation energy E sat1The change (equivalent to pump power) shows that, compared with the conventional Mamyshev oscillator based on two single-channel filters, the Mamyshev fiber oscillator based on single-channel and dual-channel filters can increase the peak output pulse power by 2.8 to 3.6 times under the same cavity parameters.

[0024] Figure 5 The figure shows the ratio of the output pulse energy of the Mamyshev fiber optic oscillator described in this invention to that of a conventional Mamyshev oscillator as a function of the gain saturation energy E. sat1 (Equivalent to pump power) change. It can be seen that compared with the conventional Mamyshev oscillator based on two single-channel filters, the Mamyshev fiber oscillator based on single-channel and dual-channel filters can increase the output pulse energy by 2.7 to 3.1 times under the same cavity parameters.

[0025] Explanation of reference numerals in the attached figures: 1—First ordinary single-mode fiber, 2—First pump source, 3—First wavelength division multiplexer, 4—First erbium-doped gain fiber, 5—First optical isolator, 6—Single-channel fiber filter, 7—Second ordinary single-mode fiber, 8—Output coupler, 9—Second pump source, 10—Second wavelength division multiplexer, 11—Second erbium-doped gain fiber, 12—Second optical isolator, 13—Dual-channel fiber filter. Detailed Implementation

[0026] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0027] This invention provides a Mamyshev fiber optic oscillator based on single-channel and dual-channel filters, such as... Figure 1 As shown, the included devices are: a first ordinary single-mode fiber 1, a first pump source 2, a first wavelength division multiplexer 3, a first erbium-doped gain fiber 4, a first optical isolator 5, a single-channel fiber filter 6, a second ordinary single-mode fiber 7, an output coupler 8, a second pump source 9, a second wavelength division multiplexer 10, a second erbium-doped gain fiber 11, a second optical isolator 12, and a dual-channel fiber filter 13;

[0028] The first common single-mode optical fiber 1, the first wavelength division multiplexer 3, the first erbium-doped gain optical fiber 4, the first optical isolator 5 and the single-channel optical fiber filter 6 are connected in sequence; the first pump source 2 is connected with the input end of the first wavelength division multiplexer 3; the devices 1-6 form a Mamyshev regenerator based on a single-channel optical fiber filter, marked as Arm1; the second common single-mode optical fiber 7, the output coupler 8, the second wavelength division multiplexer 10, the second erbium-doped gain optical fiber 11, the second optical isolator 12 and the double-channel optical fiber filter 13 are connected in sequence; the second pump source 9 is connected with the input end of the second wavelength division multiplexer 10; the devices 7-13 form a Mamyshev regenerator based on a double-channel optical fiber filter, marked as Arm2; the Arm1 and the Arm2 are both used for realizing pulse spectrum widening and filtering based on a self-phase modulation effect, and they are connected in series to form a Mamyshev optical fiber oscillator based on single-channel and double-channel filters, used for realizing high-energy and high-peak-power mode-locked pulse output.

[0029] The first common single-mode optical fiber 1 and the second common single-mode optical fiber 7 in the embodiment both adopt common single-mode optical fibers of the model SMF-28e of the Nufern company, and the lengths of the two are both 2m, and the dispersion coefficients at 1550nm are both -23ps 2 / km.

[0030] The first wavelength division multiplexer 3 and the second wavelength division multiplexer 10 in the embodiment both adopt fused-taper type wavelength division multiplexers of the Guangku Science and Technology Company, and the working wavelengths are 980 / 1550nm.

[0031] The first erbium-doped gain optical fiber and the second erbium-doped gain optical fiber in the embodiment both adopt erbium-doped gain optical fibers of the model L1500 of the CorActive company, and the lengths of the two are both 1m, and the dispersion coefficients at 1550nm are both 28ps 2 / km.

[0032] The first optical isolator and the second optical isolator in the embodiment both adopt polarization-independent optical fiber isolators of the Guangku Science and Technology Company, and the center wavelengths are both 1550nm, and the 3dB bandwidths are both 20nm.

[0033] The single-channel optical fiber filter in the embodiment adopts a single-channel optical fiber filter of the WL Photonics company, and the center wavelength is 1550nm, and the 3dB bandwidth is 5nm.

[0034] The double-channel optical fiber filter in the embodiment adopts a double-channel optical fiber filter of the WL Photonics company, and the center wavelengths of the two channels are 1537nm and 1563nm respectively, and the 3dB bandwidths are both 5nm.

[0035] The main working principle involved in the present application is specifically as follows:

[0036] In order to simulate the generation and evolution process of the multi-wavelength laser pulse in the system provided by the present application truly and accurately, the physical model adopted fully considers the influence of each discrete device in the system on the transmission of the pulse in the cavity, and is solved by a step-by-step Fourier algorithm. When the optical pulse passes through the cavity device, the optical field is multiplied by the transmission matrix corresponding to the device; when the optical pulse passes through the cavity fiber filter, the optical field is multiplied by the transmission equation corresponding to the device:

[0037]

[0038] In the formula, Δω is the angular frequency offset, and σ is the filter bandwidth.

[0039] When the optical pulse passes through the cavity fiber, the Ginzburg-Landau equation is adopted to describe the transmission characteristics of the pulse in the fiber:

[0040]

[0041] In the formula, A represents the amplitude envelope of the optical field; t and z are time and transmission distance respectively; i is the imaginary unit; β2, γ and Ω g represent the second-order dispersion of the fiber, the nonlinear parameter and the gain bandwidth of the fiber respectively. g is the gain coefficient of the fiber, and for ordinary fiber, g=0. Considering the gain saturation effect, the gain coefficient g can be expressed as:

[0042] g=g0 exp(-E p / E sat ) (3)

[0043] In the formula, g0, E p and E sat represent the small-signal gain coefficient, the pulse energy and the saturation energy of the gain fiber respectively, and in the simulation, changing E sat is equivalent to changing the power of the pump source.

[0044] The all-fiber laser system proposed in the present application is simulated numerically. In order to accurately simulate the system proposed in the present application, the following simulation parameters are set: the center wavelength of the single-channel fiber filter 6 is 1550 nm, and the 3dB bandwidth is 5 nm; the center wavelengths of the two filter channels of the double-channel fiber filter 13 are 1537 nm and 1563 nm respectively, and the 3dB bandwidths are both 5 nm; the lengths of the first ordinary single-mode fiber 1 and the second ordinary single-mode fiber 7 are both 2 m, the dispersion coefficient at 1550 nm is-23 ps 2 / km, and the nonlinear parameter γ is 1.3 / W / km; the lengths of the first erbium-doped gain fiber 4 and the second erbium-doped gain fiber 11 are both 1 m, the dispersion coefficient at 1550 nm is 28 ps 2km, nonlinear parameter γ is 4.7 / W / km, gain bandwidth Ω g is 40 nm, and small signal gain g0 is 5 / m; gain saturation energy E sat1 and E sat2 is 450 pJ; output coupling ratio of the output coupler 8 is 10%; for simulation comparison, other cavity parameters are kept unchanged, and the two-channel fiber filter 13 is replaced by another single-channel fiber filter with a center wavelength of 1563 nm and a 3dB bandwidth of 5 nm.

[0045] The specific principle and numerical simulation results of the present application are as follows:

[0046] The Mamyshev fiber oscillator based on single-channel and double-channel filters provided by the present application is composed of two Mamyshev regenerators (labeled as Arm1 and Arm2, respectively). The working principle of a single Mamyshev regenerator is as follows: after the pulse enters the nonlinear medium (including a passive or gain fiber), the spectral broadening is realized through the SPM effect, and the broadened pulse is filtered through a band-pass filter with a center wavelength offset. Through cascading the Mamyshev regenerators, the equivalent saturated absorption effect can be realized: the SPM broadening of the pulse with low intensity is insufficient, and the pulse cannot pass through the filter with a center wavelength offset, only the pulse with high enough intensity can produce sufficient SPM broadening and pass through the filter, which makes the pulse with intensity higher than a certain threshold continuously amplified and narrowed, realizing the output of the mode-locked pulse. It is worth mentioning that a double-channel fiber filter is used in Arm2 of the Mamyshev fiber oscillator, compared with the single-channel fiber filter, it can transmit more spectral components, according to the time-frequency correspondence of energy, the peak power and energy of the single pulse running in the cavity are higher. Correspondingly, the mode-locked pulse output with higher peak power and energy can be obtained at the output coupler 8.

[0047] The Mamyshev fiber oscillator based on single-channel and double-channel filters proposed by the present application is numerically simulated. In addition, for simulation comparison, the Mamyshev fiber oscillator based on two single-channel filters is also numerically simulated. The simulation results are as follows:

[0048] Figure 2 The time-domain shape diagram of the mode-locked pulse output by the Mamyshev fiber oscillator based on single-channel and double-channel filters is shown. It can be seen that the pulse width is 172 fs, and the peak power is 188.9 W.

[0049] Figure 3The time-domain shape of the output mode-locked pulse of the conventional two single-channel filter based Mamyshev fiber oscillator is shown. It can be seen that the pulse width is 297 fs and the peak power is 52.9 W, which is obviously lower than the peak power of the output pulse of the single-channel and double-channel filter based Mamyshev fiber oscillator.

[0050] Figure 4 The ratio of the output pulse peak power of the Mamyshev fiber oscillator according to the present application to that of the conventional Mamyshev oscillator with the variation of the gain saturation energy E sat1 (equivalent to the pump power) is shown. It can be seen that compared with the conventional two single-channel filter based Mamyshev oscillator, the output pulse peak power of the single-channel and double-channel filter based Mamyshev fiber oscillator can be increased by 2.8-3.6 times with the same other cavity parameters.

[0051] Figure 5 The ratio of the output pulse energy of the Mamyshev fiber oscillator according to the present application to that of the conventional Mamyshev oscillator with the variation of the gain saturation energy E sat1 (equivalent to the pump power) is shown. It can be seen that compared with the conventional two single-channel filter based Mamyshev oscillator, the output pulse energy of the single-channel and double-channel filter based Mamyshev fiber oscillator can be increased by 2.7-3.1 times with the same other cavity parameters.

[0052] Those skilled in the art will appreciate that the embodiments described herein are presented for the purpose of understanding the principles of the present application and should be understood as not limiting the scope of protection of the present application to such specific recitations and embodiments. Those skilled in the art can make various other specific modifications and combinations according to the technical inspiration disclosed by the present application without departing from the spirit of the present application, and these modifications and combinations are still within the scope of protection of the present application.

Claims

1. A Mamyshev fiber optic oscillator based on single-channel and dual-channel filters, characterized in that, The included devices are: a first ordinary single-mode fiber (1), a first pump source (2), a first wavelength division multiplexer (3), a first erbium-doped gain fiber (4), a first optical isolator (5), a single-channel fiber filter (6), a second ordinary single-mode fiber (7), an output coupler (8), a second pump source (9), a second wavelength division multiplexer (10), a second erbium-doped gain fiber (11), a second optical isolator (12), and a dual-channel fiber filter (13); The first ordinary single-mode fiber (1), the first wavelength division multiplexer (3), the first erbium-doped gain fiber (4), the first optical isolator (5), and the single-channel fiber filter (6) are connected in sequence; the first pump source (2) is connected to the input end of the first wavelength division multiplexer (3); devices (1) to (6) form a Mamyshev regenerator based on a single-channel fiber filter, labeled Arm1; the second ordinary single-mode fiber (7), the output coupler (8), the second wavelength division multiplexer (10), the second erbium-doped gain fiber (11), the second optical isolator (12), and the dual-channel fiber filter (13) are connected in sequence; the second pump source (9) is connected to the second wavelength division multiplexer (3). The input end of the multiplexer (10) is connected; devices (7) to (13) form a Mamyshev regenerator based on a dual-channel fiber filter, labeled Arm2; the single-channel fiber filter (6) in Arm1 is connected to the second ordinary single-mode fiber (7) in Arm2, and the dual-channel fiber filter (13) in Arm2 is connected to the first ordinary single-mode fiber (1) in Arm1; Arm1 and Arm2 are both used to realize pulse spectrum broadening and filtering based on self-phase modulation effect. They are connected in series to form a Mamyshev fiber oscillator based on single-channel and dual-channel filters, which is used to realize high-energy, high-peak-power mode-locked pulse output.

2. The Mamyshev fiber optic oscillator based on single-channel and dual-channel filters according to claim 1, characterized in that, The first pump source (2) and the second pump source (9) are both semiconductor lasers, and the center wavelength of their output pump light is 980nm.

3. The Mamyshev fiber optic oscillator based on single-channel and dual-channel filters according to claim 1, characterized in that, The first ordinary single-mode fiber (1) and the second ordinary single-mode fiber (7) are both single-mode fibers of the same type, both with a length of 2m and a dispersion coefficient of -23ps at 1550nm. 2 / km.

4. The Mamyshev fiber optic oscillator based on single-channel and dual-channel filters according to claim 1, characterized in that, The first wavelength division multiplexer (3) and the second wavelength division multiplexer (10) are both fused conical wavelength division multiplexers of the same type, with operating wavelengths of 980 / 1550nm.

5. A Mamyshev fiber optic oscillator based on single-channel and dual-channel filters according to claim 1, characterized in that, The first erbium-doped gain fiber (4) and the second erbium-doped gain fiber (11) are both gain fibers of the same type, each 1m in length, with a dispersion coefficient of 28ps at 1550nm. 2 / km.

6. The Mamyshev fiber optic oscillator based on single-channel and dual-channel filters according to claim 1, characterized in that, The first optical isolator (5) and the second optical isolator (12) are both polarization-independent fiber isolators of the same type, with a center wavelength of 1550nm and a 3dB bandwidth of 20nm.

7. A Mamyshev fiber optic oscillator based on single-channel and dual-channel filters according to claim 1, characterized in that, The center wavelength of the single-channel fiber filter (6) is 1550nm, and the 3dB bandwidth is 5nm.

8. A Mamyshev fiber optic oscillator based on single-channel and dual-channel filters according to claim 1, characterized in that, The center wavelengths of the two filtering channels of the dual-channel fiber filter (13) are 1537nm and 1563nm, respectively, and the 3dB bandwidth is 5nm.

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