CN103326222A - Controllable dual-wavelength mode-locking pulse fiber laser - Google Patents

Abstract

The invention provides a controllable dual-wavelength mode-locked pulsed laser, which includes a pump source, a wavelength division multiplexer, a doped optical fiber, an output coupler, a mode-locked device, and a wavelength division multiplexer that sequentially form an optical circuit. It is used to couple the pump light and the signal light output by the mode-locking device into the doped fiber; the laser also includes a three-port circulator and a polarization controller. After port b of the port circulator, the first fiber grating and the second fiber grating with different central wavelengths are reflected to the three-port circulator c port and output to the mode-locking device. The polarization controller is used to control and adjust the first fiber grating and the second fiber grating In order to realize the controllable conversion of single-wavelength and dual-wavelength laser output. The fiber laser has the advantages of stable mode-locked operation, convenient tuning, low cost and normal temperature operation.

Description

Controllable dual-wavelength mode-locked pulsed fiber laser

technical field

The invention relates to a fiber laser, in particular to a controllable dual-wavelength mode-locked pulse fiber laser.

Background technique

Dual-wavelength mode-locked pulsed fiber lasers have very important applications in many fields of modern science and technology, such as dense wavelength division multiplexing systems, fiber optic sensing, fiber dispersion measurement, etc. In some applications, it is required that the laser can be switched back and forth between single wavelength and dual wavelength to achieve controllability.

At present, in order to realize the dual-wavelength mode-locked pulse output of fiber lasers, there are two options: active mode-locked technology and passive mode-locked technology. Active mode-locked technology has the advantages of high repetition frequency and narrow line width. Adding it not only increases the cost of the laser, but also greatly increases the loss in the cavity and reduces the pulse energy of the laser; the dual-wavelength mode-locked pulsed fiber laser using passive mode-locking technology has also been extensively studied, but in dual-wavelength In passive mode-locked fiber optics, the formation mechanism of dual wavelengths is often the spectral filtering effect formed by the structure of the cavity itself. The position of the mode-locked wavelength is seriously affected by the surrounding environment, resulting in instability of the position of the mode-locked wavelength, which has a great impact on practical applications. Impact.

Contents of the invention

In order to overcome the defects in the above-mentioned background technology, the present invention provides a controllable dual-wavelength mode-locked pulsed fiber laser with simple structure, convenient implementation, stable operation at room temperature, and the ability to switch back and forth between single-wavelength and dual-wavelength to achieve mode-locking.

Technical solution of the present invention is as follows:

A controllable dual-wavelength mode-locked pulsed laser, the laser includes a pump source and a wavelength division multiplexer, a doped optical fiber, an output coupler, and a mode-locked device that sequentially form an optical circuit, and the wavelength division multiplexer is used for The pump light and the signal light output by the mode-locking device are coupled into the doped fiber; the special feature is that the laser also includes a three-port circulator and a polarization controller. After the light passes through the output coupler, the a-port of the three-port circulator Enter, then pass through the b port of the three-port circulator, and then pass through the first fiber grating and the second fiber grating with different center wavelengths to reflect to the c port of the three-port circulator and output to the mode-locking device. The polarization controller is used to control and adjust the first A fiber grating and a second fiber grating are used to realize the controllable conversion of single-wavelength and dual-wavelength laser output.

The above pump source, wavelength division multiplexer, doped fiber, output coupler, mode-locking device, three-port circulator, first fiber grating and second fiber grating are all spliced by single-mode fiber, and the polarization controller clamp On the single-mode fiber between the first fiber grating and the second fiber grating.

The above-mentioned mode-locking device is a carbon nanotube mode-locking device, and its main body is a thin film made by mixing a carbon nanotube solution and a polyvinyl alcohol solution and evaporating it.

The output ratio of the above output coupler is 10%.

Above-mentioned doped optical fiber is erbium-doped optical fiber, preferred model is the erbium-doped optical fiber of Coractive C600, and the working wavelength of pumping source is 980nm, and the frequency division range of wavelength division multiplexer is 980/1550nm, and the central wavelength of the first fiber grating is 1549.5nm, the center wavelength of the second fiber Bragg grating is 1559.5nm, the reflection bandwidth of the first fiber Bragg grating and the second fiber Bragg grating are both 1nm.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the spectrogram when dual-wavelength mode-locking of the present invention;

Fig. 3 is a pulse sequence diagram during dual-wavelength mode-locking of the present invention;

Fig. 4 is the spectrogram when the first fiber grating of the present invention is mode-locked;

Fig. 5 is the spectrogram when the second fiber grating of the present invention is mode-locked;

Wherein reference sign is:

1-pump light source; 2-wavelength division multiplexer; 3-erbium-doped fiber; 4-output coupler; 5-circulator; 6-polarization controller; 7-carbon nanotube mode-locking device; 8-first Fiber Bragg grating; 9 - the second fiber Bragg grating. The beneficial effects of the present invention are as follows:

1. The fiber laser uses a fiber grating as a wavelength selection device, which has the advantages of stable wavelength and normal temperature operation.

2. The fiber laser uses carbon nanotubes as the mode-locking device, which has the advantage of stable mode-locking operation.

3. The fiber laser adopts the adjustment polarization controller to realize the conversion of single wavelength and double wavelength, which has the advantage of convenient tuning.

4. The fiber laser adopts an all-fiber structure without spatial light adjustment devices, so its structure is simple and easy to adjust, and its stability is good.

5. The application of carbon nanotube mode-locking device greatly reduces the loss in the cavity and improves the laser pulse energy.

6. The components used in the fiber laser are all common components used in common fiber lasers, and all of them have been commercialized, so the cost is very low.

Detailed ways

As shown in Figure 1, the controllable dual-wavelength mode-locked pulsed fiber laser provided by the present invention includes a pump light source 1, a wavelength division multiplexer 2, an erbium-doped fiber 3, an output coupler 4, a three-port circulator 5, a A fiber Bragg grating 8, a second fiber Bragg grating 9, and a carbon nanotube mode-locking device 7, each of which is welded with a single-mode fiber, and the polarization controller 6 is a single-mode fiber sandwiched between the first fiber Bragg grating and the second fiber Bragg grating superior.

The pump light source 1 is a single-mode semiconductor laser with an operating wavelength of 980nm, the frequency division range of the wavelength division multiplexer 2 is 980nm/1550nm, the model of the erbium-doped fiber 3 is Coractive C600, and the dispersion coefficient at 1550nm is -9ps/nm /km, the length is 5m, the output ratio of the output coupler 4 is 10%, the reflection bandwidth of the first fiber Bragg grating 8 and the second fiber Bragg grating 9 are both 1nm, and the corresponding center wavelengths are 1549.5nm and 1559.5nm respectively, and the polarization controller 6 It is a commonly used standard device, the polarization controller 6 is between the first fiber Bragg grating 8 and the second fiber Bragg grating 9, and the three-port circulator 5, wherein port a is connected to the output coupler 4, port b is connected to the first fiber Bragg grating 8, Port c is connected to the carbon nanotube mode-locking device 7; light enters from the a port, then passes through the b-port and is reflected to the c-port output through the first fiber grating 8 and the second fiber grating 9; the carbon nanotube mode-locking device 7 is a self-made lock Molded device, a film made by mixing carbon nanotube solution and polyvinyl alcohol solution and evaporating, then sandwiching the film between two jumper heads, and fixing the jumper head with a flange; intracavity optical fiber refers to Except for all other optical fibers except the input and output two sections of optical fiber, the optical fiber connects various devices to form a ring laser cavity. The other optical fibers in the cavity are standard single-mode optical fibers with a total length of about 28m. The dispersion parameter coefficient at 1550nm is 17ps/ nm/km.

The invention adopts the carbon nanotube mode-locking device 7 and saturable absorber to realize self-starting mode-locking. Two fiber gratings with different wavelengths are inserted into the cavity through the three-port circulator 5 for spectral filtering, only the light corresponding to the center wavelength of the fiber grating can be transmitted in the cavity, and the two fiber gratings are connected by a single-mode fiber. The polarization controller 6 is clamped on the single-mode fiber between the two fiber gratings, and the polarization controller 6 changes the reflection loss of the fiber grating by squeezing and rotating the single-mode fiber between the two fiber gratings. When the loss corresponding to the wavelength of the first fiber grating 8 is small, and the wavelength loss corresponding to the second fiber grating 9 is large enough, the laser cavity will amplify the wavelength with small loss and suppress the wavelength with large loss, thus corresponding to The single-wavelength mode-locked state of the first fiber Bragg grating wavelength 8 can be realized; conversely, the single-wavelength mode-locked state corresponding to the wavelength of the second fiber Bragg grating 9 can be realized. When the losses of the two wavelengths corresponding to the two fiber gratings are equal and the power of the pumping light source 1 is large enough, the laser cavity will simultaneously amplify the two wavelengths and realize dual-wavelength mode locking. Therefore, by adjusting the polarization controller, different single-wavelength mode-locking and dual-wavelength mode-locking can be easily converted and completed.

The present invention realizes that the threshold power of dual-wavelength self-starting mode-locking is about 20mw, and the spectrum of the output laser is measured by a spectrum analyzer and the pulse sequence is observed by an oscilloscope, as shown in Figure 2 and Figure 3. At this time, the laser implements dual-wavelength mode-locking and is stable Then, by adjusting the polarization controller, the dual-wavelength mode-locking can be converted into a different single-wavelength mode-locking state, and the spectrum of the output laser is measured by a spectrum analyzer, as shown in Figure 4 and Figure 5.

Claims (5)

1. controlled dual wavelength Mode-locked laser device, this laser comprises pumping source and forms successively the wavelength division multiplexer of light circuit, doped fiber, output coupler, locked mode device, and described wavelength division multiplexer is used for the flashlight of pump light and the output of locked mode device is coupled into doped fiber; It is characterized in that: this laser also comprises three port circulator and Polarization Controllers, light is entered by three port circulator a ports through behind the output coupler, then reflex to three port circulator c ports via the first fiber grating that passes through successively different centre wavelengths behind the three port circulator b ports and the second fiber grating and export the locked mode device to, described Polarization Controller is used for regulating and controlling the first fiber grating and the controlled conversion of the second fiber grating to realize that single wavelength and dual-wavelength laser are exported.

2. controlled dual wavelength Mode-locked laser device according to claim 1, it is characterized in that: pumping source, wavelength division multiplexer, doped fiber, output coupler, locked mode device, three port circulators, the first fiber grating and the second fiber grating all adopt the monomode fiber welding, and described Polarization Controller is clipped on the monomode fiber between the first fiber grating and the second fiber grating.

3. controlled dual wavelength Mode-locked laser device according to claim 2, it is characterized in that: described locked mode device is carbon nano-tube locked mode device, its main body is the film that evaporation is made after being mixed with poly-vinyl alcohol solution by carbon nano-tube solution.

4. controlled dual wavelength Mode-locked laser device according to claim 3, it is characterized in that: the export ratio of output coupler is 10%.

5. according to claim 1 to 4 arbitrary described controlled dual wavelength Mode-locked laser devices, it is characterized in that: doped fiber is Er-doped fiber, the operation wavelength of pumping source is 980nm, the frequency division scope of wavelength division multiplexer is 980/1550nm, the centre wavelength of the first fiber grating is 1549.5nm, the centre wavelength of the second fiber grating is 1559.5nm, and the first fiber grating and the second fiber grating reflection bandwidth are 1nm.

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