Broadband asynchronous electro-optical sampling device for frequency response measurement of high-speed photoelectric detector

Abstract

The invention discloses a broadband asynchronous electro-optical sampling device for frequency response measurement of a high-speed photoelectric detector, and belongs to the technical field of electro-optical sampling. Comprising a rubidium clock, a frequency synthesizer, a mode-locked femtosecond laser 1, a mode-locked femtosecond laser 2, a nonlinear spectrum spreading module, an optical filter, a 1 / 4 wave plate, a polaroid, a high-speed photoelectric detector, an electro-optical sampling module and a data acquisition module. Through nonlinear spectrum spreading and filtering, the frequency response of the high-speed photoelectric detector at a specific wavelength point in a broadband range is measured, the problem that in the prior art, only 1550 nm wavelength frequency response can be measured is solved, and asynchronous electro-optical sampling does not need two mode-locked femtosecond lasers with the same wavelength any more. And the application range of asynchronous sampling is further expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of electro-optical sampling, and in particular relates to a wide-band asynchronous electro-optical sampling device for measuring the frequency response of a high-speed photoelectric detector. Background Art

[0002] In recent years, with the rapid development of high-speed optical communication technology, high-speed photodetectors are the core components of the receiving end of communication systems. The accurate measurement of their frequency response characteristics has an important impact on the performance of communication systems. For the measurement of the frequency response of high-speed photodetectors, electro-optical sampling technology has been deeply studied and applied with its sub-picosecond time resolution and terahertz bandwidth. Electro-optical sampling can be divided into synchronous electro-optical sampling and asynchronous electro-optical sampling according to different technical solutions. Synchronous electro-optical sampling requires a long-stroke optical delay line to scan the pulse response waveform, and the measurement time is long, generally ranging from tens of minutes to several hours. Asynchronous electro-optical sampling realizes the scanning of the pulse response waveform by controlling the repetition frequency difference between two mode-locked femtosecond lasers, and the measurement time is greatly shortened to the order of seconds, which has great technical advantages over synchronous electro-optical sampling. However, at present, electro-optical sampling technology can only realize the measurement of the frequency response of high-speed photodetectors in the 1550nm band. Due to the lack of mature mode-locked femtosecond lasers at other communication wavelengths, the frequency response of the corresponding wavelength cannot be measured. Summary of the invention

[0003] In view of the above problems existing in the prior art, the present invention proposes a wide-band asynchronous electro-optical sampling device for high-speed photoelectric detector frequency response measurement, which has a reasonable design, solves the shortcomings of the prior art and has good effects.

[0004] A wide-band asynchronous electro-optical sampling device for measuring the frequency response of a high-speed photodetector comprises a rubidium clock, a frequency synthesizer, a mode-locked femtosecond laser 1, a mode-locked femtosecond laser 2, a nonlinear spectrum expansion module, a filter, a quarter-wave plate, a polarizer, a high-speed photodetector, an electro-optical sampling module and a data acquisition module.

[0005] Furthermore, the repetition frequencies of the mode-locked femtosecond laser 1 and the mode-locked femtosecond laser 2 are locked to a rubidium clock through a frequency synthesizer, and a small repetition frequency difference is made between the two. After the output of the mode-locked femtosecond laser 2 passes through a nonlinear spectrum expansion module, the spectrum is broadened to one octave, and then a femtosecond pulse of a specific wavelength is obtained through a filter. The femtosecond pulse is used as an excitation light to excite a high-speed photodetector to generate an ultrafast electrical pulse signal, which enters an electro-optical sampling module through an electrical modulation input port.

[0006] After the output light of the mode-locked femtosecond laser 1 passes through a 1 / 4 wave plate and a polarizer, it enters the electro-optical sampling module through a sampling light input port as a sampling light pulse; the fast axis direction of the 1 / 4 wave plate and the polarization direction of the polarizer are adjusted so that the polarization direction of the sampling light forms an angle of 45° with a certain main axis direction of the electro-optical crystal coplanar waveguide in the electro-optical sampling module; the data acquisition module collects the output signal of the electro-optical sampling module to obtain the time domain pulse waveform of the high-speed photodetector, and after Fourier transformation, the corresponding frequency response curve is obtained.

[0007] Furthermore, the electro-optical sampling module includes a microwave probe, an electro-optical crystal coplanar waveguide, a polarization beam splitter, a balanced detector, a microscope objective lens and a CCD camera.

[0008] Furthermore, the sampling light pulse enters the electro-optical sampling module through the sampling light input port, is focused by the microscope objective lens and transmitted through the electro-optical crystal coplanar waveguide, the position of the focused light spot is monitored by the CCD camera, and an illumination light source is used for auxiliary illumination, and the position of the focused light spot is adjusted to be located at the center of the interval between the coplanar waveguide signal electrode and the ground electrode; the transmitted light passing through the electro-optical crystal coplanar waveguide is focused by the coupling lens, enters the polarization beam splitter, and is divided into two beams with orthogonal polarization directions, and then enters the two optical input ports of the balanced detector for measurement, respectively, to obtain a sampled electrical signal output;

[0009] The ultrafast electrical pulse signal generated by the high-speed photodetector enters the electro-optical sampling module through the electrical modulation input port, and is loaded into the electro-optical crystal coplanar waveguide via the microwave probe to form a modulated electric field.

[0010] Beneficial technical effects brought by the present invention:

[0011] The present invention realizes the measurement of the frequency response of a high-speed photodetector at a specific wavelength point within a wide band through nonlinear spectrum expansion and filtering, thereby solving the problem that the prior art can only measure the frequency response of a 1550nm wavelength. In addition, asynchronous electro-optical sampling no longer requires two mode-locked femtosecond lasers of the same wavelength, further expanding the application scope of asynchronous sampling. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of a wide-band asynchronous electro-optical sampling device in the present invention;

[0013] Figure 2 This is a schematic diagram of the structure of the electro-optical sampling module in the present invention; DETAILED DESCRIPTION

[0014] The specific implementation of the present invention is further described below in conjunction with specific embodiments:

[0015] A wide-band asynchronous electro-optic sampling device for high-speed photodetector frequency response measurement, such as Figure 1 As shown, it includes a rubidium clock, a frequency synthesizer, a mode-locked femtosecond laser 1, a mode-locked femtosecond laser 2, a nonlinear spectrum expansion module, a filter, a quarter wave plate, a polarizer, a high-speed photodetector, an electro-optical sampling module and a data acquisition module.

[0016] The repetition frequencies of the mode-locked femtosecond laser 1 and the mode-locked femtosecond laser 2 are locked to the rubidium clock through a frequency synthesizer, and a small repetition frequency difference is made between the two. After the output of the mode-locked femtosecond laser 2 passes through the nonlinear spectrum expansion module, the spectrum is broadened to one octave, and then a femtosecond pulse of a specific wavelength is obtained through a filter. The femtosecond pulse is used as an excitation light to excite a high-speed photodetector to generate an ultrafast electrical pulse signal, which enters the electro-optical sampling module through the electrical modulation input port.

[0017] After the output light of the mode-locked femtosecond laser 1 passes through a 1 / 4 wave plate and a polarizer, it enters the electro-optical sampling module through a sampling light input port as a sampling light pulse; the fast axis direction of the 1 / 4 wave plate and the polarization direction of the polarizer are adjusted so that the polarization direction of the sampling light forms an angle of 45° with a certain main axis direction of the electro-optical crystal coplanar waveguide in the electro-optical sampling module; the data acquisition module collects the output signal of the electro-optical sampling module to obtain the time domain pulse waveform of the high-speed photodetector, and after Fourier transformation, the corresponding frequency response curve is obtained.

[0018] like Figure 2 As shown, the electro-optic sampling module includes a microwave probe, an electro-optic crystal coplanar waveguide, a polarization beam splitter, a balanced detector, a microscope objective and a CCD camera. Figure 2 The electro-optic sampling module shown is a transmission structure, but a reflection structure may also be adopted.

[0019] The sampling light pulse enters the electro-optic sampling module through the sampling light input port, is focused by the microscope objective lens and transmits through the electro-optic crystal coplanar waveguide. The position of the focused light spot is monitored by the CCD camera, and an illumination light source is used for auxiliary illumination. The position of the focused light spot is adjusted to be located at the center of the interval between the coplanar waveguide signal electrode and the ground electrode. The transmitted light passing through the electro-optic crystal coplanar waveguide is focused by the coupling lens and enters the polarization beam splitter to be divided into two beams with orthogonal polarization directions. Then, the two light input ports of the balanced detector are respectively entered for measurement to obtain the sampled electrical signal output.

[0020] The ultrafast electrical pulse signal generated by the high-speed photodetector enters the electro-optical sampling module through the electrical modulation input port, and is loaded into the electro-optical crystal coplanar waveguide via the microwave probe to form a modulated electric field.

[0021] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A wide-band asynchronous electro-optical sampling device for high-speed photodetector frequency response measurement, characterized in that: It includes a rubidium clock, a frequency synthesizer, a mode-locked femtosecond laser 1, a mode-locked femtosecond laser 2, a nonlinear spectrum expansion module, a filter, a quarter wave plate, a polarizer, a high-speed photodetector, an electro-optical sampling module and a data acquisition module.

2. A wide-band asynchronous electro-optical sampling device for high-speed photodetector frequency response measurement according to claim 1, characterized in that: The repetition frequencies of the mode-locked femtosecond laser 1 and the mode-locked femtosecond laser 2 are locked to a rubidium clock through a frequency synthesizer, and a small repetition frequency difference is made between the two. After the output of the mode-locked femtosecond laser 2 passes through a nonlinear spectrum expansion module, the spectrum is broadened to one octave, and then a femtosecond pulse of a specific wavelength is obtained through a filter. The femtosecond pulse is used as an excitation light to excite a high-speed photodetector to generate an ultrafast electrical pulse signal, which enters an electro-optical sampling module through an electrical modulation input port. The output light of the mode-locked femtosecond laser 1 passes through a quarter wave plate and a polarizer, and then enters the electro-optical sampling module through a sampling light input port as a sampling light pulse; The fast axis direction of the 1 / 4 wave plate and the polarization direction of the polarizer are adjusted so that the polarization direction of the sampling light forms a 45° angle with a main axis direction of the electro-optic crystal coplanar waveguide in the electro-optic sampling module. The data acquisition module collects the output signal of the electro-optic sampling module to obtain the time domain pulse waveform of the high-speed photodetector. After Fourier transform, the corresponding frequency response curve is obtained.

3. A wide-band asynchronous electro-optical sampling device for high-speed photodetector frequency response measurement according to claim 2, characterized in that: The electro-optic sampling module includes a microwave probe, an electro-optic crystal coplanar waveguide, a polarization beam splitter, a balanced detector, a microscope objective lens and a CCD camera.

4. A wide-band asynchronous electro-optical sampling device for high-speed photodetector frequency response measurement according to claim 3, characterized in that: The sampling light pulse enters the electro-optic sampling module through the sampling light input port, is focused by the microscope objective lens and transmits through the electro-optic crystal coplanar waveguide. The position of the focused light spot is monitored by the CCD camera, and an illumination light source is used for auxiliary illumination. The position of the focused light spot is adjusted to be located at the center of the interval between the coplanar waveguide signal electrode and the ground electrode. The transmitted light passing through the electro-optic crystal coplanar waveguide is focused by the coupling lens and enters the polarization beam splitter to be divided into two beams with orthogonal polarization directions. Then, the two light input ports of the balanced detector are respectively entered for measurement to obtain the sampled electrical signal output. The ultrafast electrical pulse signal generated by the high-speed photodetector enters the electro-optical sampling module through the electrical modulation input port, and is loaded into the electro-optical crystal coplanar waveguide via the microwave probe to form a modulated electric field.

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