Device capable of quickly and flexibly regulating and controlling central wavelength of ultrashort light pulse

Abstract

The invention provides a device capable of quickly and flexibly regulating and controlling the central wavelength of an ultrashort light pulse, which relates to the technical field of optics and consists of a mode-locked laser, a Mach-Zehnder interferometer based on phase modulation, an arbitrary waveform generator and a polarization dependent isolator. The mode-locked laser is used for providing a stable single pulse; the Mach-Zehnder interferometer based on phase modulation is used for regulating and controlling the relative phase between pulses; the arbitrary waveform generator is used for providing an electric signal for modulation; and the polarization dependent isolator is used for enabling the polarization states of the two pulses to be consistent. According to the invention, the efficiency and flexibility of adjusting the central wavelength of the spectrum can be improved.

Description

Technical Field

[0001] The invention relates to the field of optical technology, and in particular to a device capable of quickly and flexibly regulating the central wavelength of an ultrashort optical pulse. Background Art

[0002] In the fields of optical communications and photonics, it is often necessary to accurately and flexibly adjust the central wavelength of the spectrum according to specific needs to meet different requirements.

[0003] At present, common means to achieve this regulation function include the use of optical devices such as optical filters and optical parametric oscillators. Although optical filters can filter out specific wavelength components from the spectrum of light pulses, they lack the ability to flexibly control the central wavelength of the spectrum. Optical parametric oscillators are optical devices that use nonlinear effects in optical fibers to achieve wavelength conversion. They can convert input lasers into output light of different wavelengths. However, their output wavelengths are affected by many factors such as ambient temperature. Summary of the invention

[0004] Based on the deficiencies of the above-mentioned technology, the present invention provides a device that can quickly and flexibly adjust the central wavelength of ultrashort optical pulses, which can improve the efficiency and flexibility of adjusting the central wavelength of the spectrum.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] First, a device that can quickly and flexibly adjust the central wavelength of ultrashort optical pulses, consisting of a mode-locked laser, a phase-modulated Mach-Zehnder interferometer, an arbitrary waveform generator, and a polarization-dependent isolator;

[0007] The mode-locked laser is used to provide a stable single pulse;

[0008] The phase-modulated Mach-Zehnder interferometer is used to control the relative phase between pulses;

[0009] The arbitrary waveform generator is used to provide an electrical signal for modulation;

[0010] The polarization-dependent isolator is used to make the polarization states of two pulses consistent.

[0011] Further, the phase modulation-based Mach-Zehnder interferometer includes a first optical coupler, a variable optical attenuator, a phase modulator, an optical fiber delay line, a polarization controller and a second optical coupler;

[0012] The output port of the mode-locked laser is connected to the input port of the first optical coupler; one of the output ports of the first optical coupler is connected to one end of the optical fiber delay line, and the other end of the optical fiber delay line is connected to the input end of the variable optical attenuator; the input end of the phase modulator is connected to the other output end of the first optical coupler through a polarization controller; the output end of the phase modulator and the output end of the variable optical attenuator are respectively connected to the two input ends of the second optical coupler;

[0013] The phase modulator is a phase modulator made of linear electro-optical effect material; the input and output optical fibers of the phase modulator are both polarization-maintaining optical fibers.

[0014] Furthermore, the output end of the arbitrary waveform generator is connected to the voltage input electrode of the phase modulator through a radio frequency line.

[0015] Furthermore, the input end of the polarization-dependent isolator is connected to the output end of the second optical coupler.

[0016] In a second aspect, a method for quickly and flexibly adjusting the central wavelength of an ultrashort optical pulse comprises the following steps:

[0017] S1: Turn on the pump source of the mode-locked laser to obtain a stable single pulse;

[0018] S2: A stable single pulse is input into the first optical coupler, and the first optical coupler divides the stable single pulse into two pulses; one pulse reaches the phase modulator through the polarization controller, and the other pulse reaches the variable optical attenuator through the optical fiber delay line;

[0019] S3: The two pulses are injected into the second optical coupler through the output ends of the phase modulator and the variable optical attenuator for beam combining. Finally, the two beam-combined pulses are input into the polarization-dependent isolator, and the output end of the polarization-dependent isolator is set as the output port of the total device.

[0020] S4: Adjust the polarization controller to ensure that the light input to the phase modulator is linearly polarized light and the polarization direction is parallel to the fast axis or slow axis of the polarization-maintaining fiber;

[0021] S5: The optical path difference between the two arms of the phase-modulated Mach-Zehnder interferometer is controlled by adjusting the knob of the optical fiber delay line; the power of the two optical pulses is precisely controlled by rotating the knob on the variable optical attenuator until the peak powers of the two pulses output from the output end of the polarization-dependent isolator are completely equal;

[0022] S6: The electrical signal from the arbitrary waveform generator acts on the voltage input electrode of the phase modulator to change the relative phase between pulses.

[0023] The above solution of the present invention includes at least the following beneficial effects:

[0024] The present invention uses a phase modulator in conjunction with a Mach-Zehnder interferometer to act together on the transmission process of the pulse, so that parameters such as the relative phase can be accurately adjusted as expected, and the central wavelength of the spectrum can be flexibly and efficiently controlled in the spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the overall structure of a device provided by the present invention that can quickly and flexibly adjust the central wavelength of ultrashort optical pulses.

[0026] Figure 2 Schematic diagram of the autocorrelation trace of the double pulse provided by the present invention.

[0027] Figure 3 The schematic diagram of the spectrum evolution of the relative phase change presented by the present invention presents a sinusoidal waveform. Figure (a): relative phase change curve; Figure (b): corresponding spectrum evolution schematic diagram.

[0028] Figure 4 The present invention provides a schematic diagram of the spectrum evolution in which the relative phase change presents a square waveform, wherein Figure (a) represents a relative phase change curve diagram; Figure (b) represents a corresponding spectrum evolution schematic diagram.

[0029] Figure 5 The present invention provides a curve diagram showing the relationship between the change in the central wavelength of the spectrum and the peak-to-peak voltage applied to the phase modulator electrode. DETAILED DESCRIPTION

[0030] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0031] like Figure 1 As shown, an embodiment of the present invention proposes a device that can quickly and flexibly adjust the central wavelength of an ultrashort optical pulse, including: a mode-locked laser 1, a first 1×2 optical coupler (OC-1) 2, a polarization controller (PC) 3, a phase modulator (PM) 4, an optical fiber delay line (ODL) 5, a variable optical attenuator (VOA) 6, a second 1×2 optical coupler (OC-2) 7, a polarization dependent isolator (PS-ISO) 8, and an arbitrary waveform generator (AWG) 9.

[0032] The key parts of the device are composed of a first optical coupler 2, a polarization controller 3, a phase modulator 4, an optical fiber delay line 5, a variable optical attenuator 6 and a second optical coupler 7, which together constitute a Mach-Zehnder interferometer based on phase modulation.

[0033] From the mode-locked fiber laser 1 , a stable single pulse output can be obtained.

[0034] The stable single pulse is input to the first optical coupler 2 (coupling ratio 50:50) for beam splitting, and is divided into two identical pulses. One pulse reaches the phase modulator 4 through the polarization controller 3, and the other pulse reaches the variable optical attenuator 6 through the optical fiber delay line 5.

[0035] The two pulses are further injected into the second optical coupler 7 (coupling ratio 50:50) through the output ends of the phase modulator 4 and the variable optical attenuator 6 for beam combining. Finally, the two combined pulses are input into the polarization-dependent isolator 8, and the output end of the polarization-dependent isolator 8 is set as the total output port of the device.

[0036] The polarization-dependent optical isolator 8 can effectively make the polarization states of the two pulses consistent. Such a setting can avoid optical signal interference caused by different polarization states.

[0037] Furthermore, the voltage input electrode of the phase modulator 4 is connected to the output end of the arbitrary waveform generator 9 via a radio frequency line.

[0038] Since the input and output optical fibers of the phase modulator 4 are both polarization-maintaining optical fibers, the bias state of the polarization controller 3 is adjusted to ensure that the light input to the phase modulator 4 is linearly polarized light and the polarization direction is parallel to the fast axis or slow axis of the polarization-maintaining optical fiber.

[0039] Furthermore, the optical path difference between the two arms of the phase-modulated Mach-Zehnder interferometer is controlled by adjusting the knob of the optical fiber delay line 5, and the number of spectral interference fringes decreases as the optical path difference between the two arms decreases. In order to make the intensity of the two pulses output from the output end of the polarization-dependent isolator 8 consistent, the power of the two optical pulses is precisely controlled by rotating the knob on the variable optical attenuator 6 until the peak powers of the two output pulses are completely equal, and an interference spectrum with high contrast can also be obtained in this way.

[0040] When the electrical signal emitted by the arbitrary waveform generator 9 acts on the voltage input electrode of the phase modulator 4, it will change the phase delay of the pulse after passing through the phase modulator 4, thereby causing the relative phase between the pulses to change.

[0041] Since the phase modulator 4 is made of a linear electro-optical effect material, the change in relative phase is proportional to the input voltage.

[0042] Through the above-mentioned use method, two completely identical pulses with a certain relative phase and time interval can be obtained from the output end of the polarization-dependent isolator 8 .

[0043] Furthermore, the spectral intensity expression at the total output port after phase modulation is:

[0044]

[0045] Wherein, R represents the modulation coefficient of the phase modulator, and V(t) represents the electrical signal applied to the voltage input electrode of the phase modulator.

[0046] According to the expression of the spectral intensity, if the relative pulse spacing τ is small enough, the relative phase The change of (i.e. the change of the voltage applied to the input electrode of the phase modulator) can cause the change of the center wavelength of the spectrum. The change of the center wavelength of the spectrum is consistent with the change of the voltage applied to the input electrode of the phase modulator; and the change range of the center wavelength of the spectrum increases with the increase of the peak-to-peak voltage.

[0047] Furthermore, by performing Fourier transform on the interference spectrum, the corresponding autocorrelation trace curve can be obtained, such as Figure 2 As shown in the figure, it can be seen that the time interval between pulses is 1.9ps, and the peak power is basically consistent, which further verifies the reliability of the device.

[0048] Furthermore, through the above operations, various types of modulation are performed on the relative phase of the pulse:

[0049] Embodiment 1

[0050] If the electrical signal applied by the arbitrary waveform generator 9 to the phase modulator 4 is a sinusoidal electrical signal, such as Figure 3 As shown in (a), the repetition frequency of the sinusoidal electrical signal is 100KHz, and we can get Figure 3 (b) shows the spectrum evolution diagram. The central wavelength of the spectrum changes sinusoidally with the change of the electrical signal, and the frequency of the change is consistent with the repetition frequency of the electrical signal.

[0051] Embodiment 2

[0052] Change the waveform of the electrical signal to a square wave signal, such as Figure 4 As shown in (a), the repetition frequency of the signal is 50KHz, and the following is obtained: Figure 4 (b) shows the spectrum evolution diagram. The central wavelength of the spectrum jumps as the electrical signal changes, and the frequency of the jump is consistent with the repetition frequency of the electrical signal.

[0053] It should be noted that the pulse time interval in the second embodiment is the same as the pulse time interval described in the first embodiment, both of which are Figure 2 The 1.9ps shown in the figure; the change in relative phase is proportional to the input voltage.

[0054] As described in the first and second embodiments, if the time interval τ of the pulses is small enough, the relative phase The change of (i.e. the change of the voltage applied to the input electrode of the phase modulator) can cause the change of the center wavelength position of the spectrum. Changing the waveform of the electrical signal will cause the position of the center wavelength of the spectrum to produce a corresponding waveform change, and the frequency of the change is consistent with the frequency of the electrical signal. Since the response of the spectrum to the electrical signal occurs instantaneously, the device also reflects the characteristics of fast response.

[0055] Figure 5 The graph shows the relationship between the change in the center wavelength of the spectrum and the peak-to-peak voltage applied to the phase modulator electrode, and the change in the center wavelength position of the ultrashort pulse is proportional to the peak-to-peak voltage. The points on the graph represent the experimental results, and the solid line represents the result of linear fitting.

[0056] With the technical solution designed above, the flexible adjustment of the central wavelength position of the ultrashort pulse can be achieved accurately and effectively. In the implementation process of this technical solution, various technical links work closely together to act on the regulation of the central wavelength position of the spectrum. Although the present invention has been explained in detail with reference to specific embodiments, it should be clear that the scope of the present invention is by no means limited to the disclosed implementation methods and corresponding embodiments. For those technicians who have a certain knowledge reserve and practical experience in their professional fields, based on the core idea of ​​the present invention, improvements or appropriate changes can be implemented according to the above description. As long as such improvements and changes do not deviate from the principles and essence of the present invention, all these changes should be included in the protection scope of the present invention.

Claims

1. A device for quickly and flexibly adjusting the central wavelength of ultrashort optical pulses, characterized in that: It consists of a mode-locked laser, a phase-modulated Mach-Zehnder interferometer, an arbitrary waveform generator and a polarization-dependent isolator. The mode-locked laser is used to provide a stable single pulse; The phase-modulated Mach-Zehnder interferometer is used to control the relative phase between pulses; The arbitrary waveform generator is used to provide an electrical signal for modulation; The polarization-dependent isolator is used to make the polarization states of two pulses consistent.

2. The device for quickly and flexibly adjusting the central wavelength of ultrashort optical pulses according to claim 1, characterized in that: The phase-modulated Mach-Zehnder interferometer comprises a first optical coupler, a variable optical attenuator, a phase modulator, an optical fiber delay line, a polarization controller and a second optical coupler; The output port of the mode-locked laser is connected to the input port of the first optical coupler; one of the output ports of the first optical coupler is connected to one end of the optical fiber delay line, and the other end of the optical fiber delay line is connected to the input end of the variable optical attenuator; the input end of the phase modulator is connected to the other output end of the first optical coupler through a polarization controller; the output end of the phase modulator and the output end of the variable optical attenuator are respectively connected to the two input ends of the second optical coupler; The phase modulator is a phase modulator made of linear electro-optical effect material; the input and output optical fibers of the phase modulator are both polarization-maintaining optical fibers.

3. The device for quickly and flexibly adjusting the central wavelength of ultrashort optical pulses according to claim 2, characterized in that: The output end of the arbitrary waveform generator is connected to the voltage input electrode of the phase modulator through a radio frequency line.

4. The device for quickly and flexibly adjusting the central wavelength of ultrashort optical pulses according to claim 3, characterized in that: The input end of the polarization dependent isolator is connected to the output end of the second optical coupler.

5. A method for quickly and flexibly adjusting the central wavelength of ultrashort optical pulses, characterized in that: The method is used to execute the device according to any one of claims 1 to 4, comprising the following steps: S1: Turn on the pump source of the mode-locked laser to obtain a stable single pulse; S2: A stable single pulse is input into the first optical coupler, and the first optical coupler divides the stable single pulse into two pulses; one pulse reaches the phase modulator through the polarization controller, and the other pulse reaches the variable optical attenuator through the optical fiber delay line; S3: The two pulses are injected into the second optical coupler through the output ends of the phase modulator and the variable optical attenuator for beam combining. Finally, the two beam-combined pulses are input into the polarization-dependent isolator, and the output end of the polarization-dependent isolator is set as the output port of the total device. S4: Adjust the polarization controller to ensure that the light input to the phase modulator is linearly polarized light and the polarization direction is parallel to the fast axis or slow axis of the polarization-maintaining fiber; S5: The optical path difference between the two arms of the phase-modulated Mach-Zehnder interferometer is controlled by adjusting the knob of the optical fiber delay line; the power of the two optical pulses is precisely controlled by rotating the knob on the variable optical attenuator until the peak powers of the two pulses output from the output end of the polarization-dependent isolator are completely equal; S6: The electrical signal from the arbitrary waveform generator acts on the voltage input electrode of the phase modulator to change the relative phase between pulses.

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