A linear chirp microwave signal generating device based on laser phased array

Abstract

The present invention belongs to the field of microwave photon technology. In order to solve the problem that the output power of the existing microwave signal generating device is not high, a linear chirp microwave signal generating device based on a laser phased array is disclosed, which includes: an external light source laser, an optical attenuator, a first polarization controller, an intensity modulator, a waveform generator, a second polarization controller, an optical circulator, a laser phased array and a photodiode. The laser phased array is integrated by multiple node lasers, and the external optical signal is only injected into one node laser in the laser phased array. Under appropriate injection power, the single-cycle oscillation output of the laser phased array is stimulated. A negative refractive index guided and gain guided waveguide structure is adopted between all the node lasers in the laser phased array, so that they have the same oscillation frequency and phase, and the output power is enhanced; it has the advantages of high integration, high power and the generation of multiple parallel linear chirp microwave signals with the same frequency and phase.

Description

Technical Field

[0001] The invention relates to the fields of microwave photon technology and radar, and in particular to a linear chirp microwave signal generating device based on a light injection laser phased array. Background Art

[0002] Semiconductor lasers are devices that use semiconductor materials as working materials to achieve laser output. They are small in size, long in life, and are pumped by a simple current injection method. Their operating voltage and current are compatible with integrated circuits, so they can be monolithically integrated with them. Due to these advantages, semiconductor lasers have been widely used in laser communications, optical storage, optical gyroscopes, laser printing, ranging, and radar. Linear chirp waveforms are the most commonly used transmitting signal waveforms for radars, and can improve the detection distance and detection accuracy of radars through pulse compression technology. In recent years, with the development of photonics technology, researchers have begun to use photonic devices such as semiconductor lasers to replace traditional electronic devices to generate linear chirp microwave signals, thereby solving the limitations of electronic devices in terms of center frequency and bandwidth. For example: a linear chirped microwave signal generation scheme based on a frequency-sweeping optoelectronic oscillator (see [P. Zhou, F. Zhang, and S. Pan, “Generation of linearfrequency-modulated waveforms by a frequency-sweeping optoelectronicoscillator,” Journal of Lightwave Technology 36(18), 3927-3934 (2018).]); a generation scheme based on a dual-polarization parallel Mach-Zehnder modulator (see [P. Li, L. Yan, J. Ye, X. Zou, B.Luo, and W. Pan, “Photonic approach for the generation of switchable down-,up-, and dual-chirped linear frequency-modulated microwave signals,” OpticsLetters 45(7), 1990-1993 (2020).]). These schemes all use semiconductor lasers to generate linear chirped microwave signals. Generally speaking, the higher the temperature of the semiconductor laser, the longer the wavelength, but this also leads to a decrease in the luminous intensity.

[0003] Therefore, the driving current of most semiconductor lasers is limited to about 20 mA, and their output power is about tens of mW. As modern communications have higher and higher requirements for laser output power, a single semiconductor laser can no longer meet the output power requirements. Through waveguide coupling technology, multiple lasers are integrated together to form a linear array or a planar array, which can reach an optical power output of several kW. Summary of the invention

[0004] The main purpose of the present invention is to provide a linear chirped microwave signal generation device and method based on a laser phased array to solve the shortcomings of the existing commonly used methods: (1) the output power of a single semiconductor laser is not high, and (2) the discrete laser system is too large and the energy consumption is too high. Based on the advantages of the phased array, the device also has the characteristic of being able to realize multi-channel parallel output of the same frequency and phase signal.

[0005] The invention provides a linear chirp microwave signal generating device based on a laser phased array, comprising: an external light source laser, an optical attenuator, a first polarization controller, an intensity modulator, a waveform generator, a second polarization controller, an optical circulator, a laser phased array and a photodiode; wherein: the laser phased array is integrated by packaging a plurality of node lasers under specific planar waveguide coupling, the external light source laser, the optical attenuator, the first polarization controller, the intensity modulator and the second polarization controller are connected in sequence through optical fibers; the output end of the waveform generator is connected to the radio frequency end of the intensity modulator through a radio frequency line; the output end of the second polarization controller is connected to the first port of the optical circulator; the output end of the laser phased array is connected to the second port of the optical circulator; the third port of the optical circulator is connected to the photodiode; and the linear chirp microwave signal is derived from the output end of the photodiode.

[0006] The node lasers in the array are connected together by evanescent field coupling. Evanescent field coupling is to periodically change the real part of the refractive index so that the peak value of each unit light field is distributed in the low refractive index area when the array is running. Therefore, the output beams of each light-emitting unit can have coherence, that is, phase locking is achieved, so that coherent light output can be obtained, which not only improves the beam quality, but also concentrates and increases the output coherent energy. The laser phased array is an integrated device that is grown and packaged together with multiple node lasers coupled by a specific planar waveguide structure. The external optical signal is only injected into one node laser in the laser phased array. Under appropriate injection power, the single-cycle oscillation output of the laser phased array is stimulated. The waveguide structure of negative refractive index guidance and gain guidance is used between all node lasers in the laser phased array, so that they have the same oscillation frequency and phase, so the output power can be increased. The injected optical signal is intensity modulated, and a linear chirp microwave signal can be obtained after photoelectric conversion. By external coupling and output selection, the simultaneous generation of multiple linear chirp signals can be achieved.

[0007] A further solution is that the node laser spacing is 1 μm~100 μm.

[0008] A better solution is: the emission frequency of the external light source laser is greater than the total electric field free resonance frequency of the laser phased array, that is, positive frequency detuning; the external light source laser is only injected into one node laser in the laser phased array, and the remaining node lasers in the laser phased array maintain the same frequency offset as the injected node laser, and the frequency offset size is equal to the detuning frequency size.

[0009] A better solution is: the external light source laser is injected into a node laser in the laser phased array, the node laser exhibits a single-cycle oscillation state, all other node lasers in the laser phased array are excited to a single-cycle oscillation state, and the oscillation frequency and phase of all node lasers in the laser phased array are the same.

[0010] A better solution is: the sawtooth-like waveform generated by the waveform generator is input into the intensity modulator to modulate the intensity of the optical signal output by the external light source laser, and the optical signal output by the laser phased array is converted into photoelectricity by the photodiode to generate a linear chirped microwave signal.

[0011] The linear chirp microwave signal generating device based on a laser phased array proposed in the present invention has the following advantages compared with the current technology:

[0012] 1. This device is highly integrable. The laser phased array is integrated by packaging multiple lasers under specific planar waveguide coupling, and the spacing between each laser node is 1 μm~100 μm, which is much smaller than the current discrete laser device.

[0013] 2. This device has high power and multi-channel parallelism. It only needs to be injected into a node laser in the laser phased array to achieve the same frequency and phase oscillation behavior of all node lasers in the array. Not only is the output power of the laser phased array much higher than the output power of a single semiconductor laser, but it can also generate multi-channel parallel linear chirped microwave signals with the same frequency and phase.

[0014] The accompanying drawings are as follows:

[0015] Figure 1 A schematic diagram of a linear chirped microwave signal generating device based on a laser phased array provided by the present invention;

[0016] Figure 2 is the spectrum output by node laser a;

[0017] Figure 3 is the spectrum output by node laser b;

[0018] Figure 4 It is the spectrum diagram of the output single-frequency microwave signal;

[0019] Figure 5 is the time domain waveform of the output linear chirped microwave signal;

[0020] Figure 6 is the time-frequency diagram of the output linear chirped microwave signal;

[0021] Among them: 1-external light source laser, 2-optical attenuator, 3-first polarization controller, 4-intensity modulator, 5-waveform generator, 6-second polarization controller, 7-optical circulator, 8-laser phased array, 9-photodiode. DETAILED DESCRIPTION

[0022] As attached Figure 1 , which is a system block diagram of a linear chirped microwave signal generating device based on a laser phased array of the present invention. The device can generate a linear chirped microwave waveform with a bandwidth of 3 GHz and a time width of 1 μs.

[0023] exist Figure 1The invention comprises: an external light source laser 1, an optical attenuator 2, a first polarization controller 3, an intensity modulator 4, a waveform generator 5, a second polarization controller 6, an optical circulator 7, a laser phased array 8 and a photodiode 9, wherein: the laser phased array 8 is integrated by a plurality of node laser packages, and the external light source laser, the optical attenuator 2, the first polarization controller 3, the intensity modulator 4 and the second polarization controller 6 are connected in sequence through optical fibers; the output end of the waveform generator 5 is connected to the radio frequency end of the intensity modulator through a radio frequency line; the output end of the second polarization controller 6 is connected to the first port of the optical circulator 7; the output end of the laser phased array 8 is connected to the second port of the optical circulator 7; the third port of the optical circulator 7 is connected to the photodiode 9; and the linear chirp microwave signal is derived from the output end of the photodiode 9.

[0024] Figure 1 It is only a schematic diagram of the connection relationship between the various technical features of the device of this scheme. Figure 1 The shapes of the components are merely schematic and do not constitute limitations on their shapes and structures.

[0025] The specific working process of the linear chirp microwave signal generating device based on the laser phased array involved in the present invention is as follows:

[0026] The present invention is mainly based on the light injection structure of external light injected into the laser phased array to excite the single-cycle oscillation nonlinear dynamic state of the laser phased array 8. The emission frequency of the external light source laser is set to be greater than the total electric field free resonance frequency of the laser phased array 8, that is, positive frequency detuning. The external light source laser is only injected into one node laser in the laser phased array 8, and the remaining node lasers in the laser phased array 8 maintain the same frequency offset as the injected node laser, and the frequency offset size is equal to the detuning frequency size. The optical attenuator 2 is adjusted to control the intensity of the injected light signal. Within the appropriate injection power range, all node lasers in the laser phased array 8 achieve single-cycle oscillation nonlinear dynamic output, and the oscillation frequency is the same. After the photoelectric conversion is completed by the photodiode 9, a single-frequency microwave signal is generated. On this basis, the waveform generator 5 outputs a sawtooth-like waveform signal, and the waveform signal is modulated to the intensity modulator 4 to perform intensity modulation on the output light of the external light source laser 1. The single-frequency microwave signal output by the photodiode 9 is converted into a linear chirped microwave signal. By adjusting the frequency emitted by the external light source laser, the frequency range of the generated linear chirp microwave signal can be changed; by adjusting the amplitude of the waveform output by the waveform generator 5, the bandwidth of the generated linear chirp microwave signal can be changed; by adjusting the time period of the waveform output by the waveform generator 5, the time period of the generated linear chirp microwave signal can be changed.

[0027] Taking the laser phased array 8 formed by packaging two node lasers as an example, the effect of the device of the present invention in generating a linear chirped microwave signal is described:

[0028] The two node lasers in the laser phased array 8 are node laser a and node laser b. The optical signal emitted by the external light source laser is only injected into the node laser a, and the node laser b is not injected. The emission frequency of the node laser a is 230.6096 THz, and the emission frequency of the external light source laser is 15 GHz higher than that of the node laser a, that is, the frequency detuning between the external light source laser and the node laser a is 15 GHz, and the emission frequency of the node laser b is 15 GHz higher than that of the node laser a, that is, the frequency offset between the node laser b and the node laser a is 15 GHz. Under appropriate injection power, the laser phased array 8 operates in a single-cycle oscillation state. Figure 2 is the spectrum of node laser a; Figure 3 is the spectrum diagram of node laser b. It can be seen that the oscillation frequency of node laser a is the same as that of node laser b. After the photoelectric conversion is completed by the photodiode 9, a single-frequency microwave signal is generated. Figure 4 The waveform generator 5 outputs a sawtooth-like waveform signal with a frequency of 1 MHz, and the single-frequency microwave signal output by the photodiode 9 is converted into a linear chirped microwave signal. Figure 5 It is the time domain waveform diagram of the linear chirp microwave signal; Figure 6 is a time-frequency diagram of a linear chirped microwave signal. It can be seen that the frequency of the linear chirped microwave signal increases linearly with time within a period of 1 μs. Therefore, the present invention can obtain a linear chirped microwave signal by adopting the above technical solution. Therefore, it has the advantages of high integration, high power and the generation of multiple parallel linear chirped microwave signals of the same frequency and phase.

[0029] The above description is only a preferred embodiment of the device of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A linear chirp microwave signal generating device based on a laser phased array, characterized in that include: An external light source laser (1), an optical attenuator (2), a first polarization controller (3), an intensity modulator (4), a waveform generator (5), a second polarization controller (6), an optical circulator (7), a laser phased array (8) and a photodiode (9), wherein: the laser phased array is integrated by packaging a plurality of node lasers; the external light source laser (1), the optical attenuator (2), the first polarization controller (3), the intensity modulator (4) and the second polarization controller (6) are connected in sequence through optical fibers; the output end of the waveform generator (5) is connected to the radio frequency end of the intensity modulator (6) through a radio frequency line; the output end of the second polarization controller (6) is connected to the first port of the optical circulator (7); the output end of the laser phased array (8) is connected to the second port of the optical circulator (7); the third port of the optical circulator (7) is connected to the photodiode (9); and a linear chirp microwave signal is derived from the output end of the photodiode (9); The node lasers in the laser phased array are connected together by evanescent field coupling. The evanescent field coupling is to make the peak value of each unit light field distributed in the low refractive index area when the laser phased array is running by periodically changing the real part of the refractive index. Negative refractive index guided and gain guided waveguide structures are used between all node lasers in the laser phased array, so that all node lasers have the same oscillation frequency and phase; The working process of the linear chirp microwave signal generation device based on the laser phased array is as follows: The emission frequency of the external light source laser is set to be greater than the total electric field free resonance frequency of the laser phased array, the external light source laser is only injected into one node laser in the laser phased array, and the remaining node lasers in the laser phased array maintain the same frequency offset as the injected node laser, and the frequency offset magnitude is equal to the detuning frequency magnitude; the optical attenuator is adjusted to control the intensity of the injected light signal so that all the node lasers in the laser phased array are single-cycle oscillation nonlinear dynamic outputs, and the oscillation frequencies are the same; after the photoelectric conversion is completed by the photodiode, a single-frequency microwave signal is generated; the waveform generator outputs a sawtooth-like waveform signal, and the waveform signal is modulated to the intensity modulator to perform intensity modulation on the output light of the external light source laser; the single-frequency microwave signal output by the photodiode is converted into a linear chirped microwave signal; The frequency range of the generated linear chirp microwave signal is changed by adjusting the frequency emitted by the external light source laser; The bandwidth of the generated linear chirped microwave signal is changed by adjusting the amplitude of the waveform output by the waveform generator; The time period of the generated linear chirped microwave signal is changed by adjusting the time period of the waveform output by the waveform generator.

2. The linear chirp microwave signal generating device based on a laser phased array according to claim 1, characterized in that: The laser node spacing of each node in the laser phased array is 1 μm to 100 μm.

3. The linear chirp microwave signal generating device based on a laser phased array according to claim 1, characterized in that The external light source laser (1) is injected into a node laser in the laser phased array (8), the node laser presents a single-cycle oscillation state, all other node lasers in the laser phased array (8) are excited into a single-cycle oscillation state, the oscillation frequency and phase of all node lasers in the laser phased array (8) are the same, and the total output power of the laser phased array is the sum of the light intensities of all node lasers.

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