An ultra-wideband white noise source based on chaotic micro-ring optical frequency comb

Abstract

The present application belongs to the field of communication technology, and particularly relates to a kind of on-chip ultra-wideband white noise generation method based on chaotic micro-ring optical frequency comb, the implementation of the method includes semiconductor laser, micro-ring resonator, photodetector, characterized by: semiconductor laser, micro-ring resonator, photodetector are integrated in the same chip substrate;Semiconductor laser output continuous light injection micro-ring resonator will occur four-wave mixing, self-phase modulation, cross-phase modulation and dispersion combined action, after being output through micro-ring resonator straight-through end, equal-interval chaotic optical frequency comb is generated, and then through the beat of multiple chaotic optical frequency comb, high-bandwidth noise signal can be realized.The present application compared with existing noise source, simple structure and has smaller volume, low power consumption, high stability and bandwidth expandable advantage.

Description

An ultrabandwidth white noise source based on a chaotic micro-ring optical frequency comb Technical Field

[0001] This invention relates to the field of communication technology, and in particular to an ultrawideband white noise source based on a chaotic micro-ring optical frequency comb. Background Technology

[0002] Noise is an unavoidable and necessary problem for most systems. In the early stages of research, efforts were mainly focused on reducing or eliminating noise. However, as research progressed, it was gradually discovered that noise has a significant impact on the anti-interference capabilities of testing instruments and the evaluation of communication system performance. By inputting precisely known noise into the device under test, module, or system, it is possible to measure receiver sensitivity, evaluate antenna performance, analyze amplifier parameters, calibrate radiometer output, and verify radar anti-interference capabilities. Therefore, noise sources are special scientific instruments with important applications in many fields such as communication, remote sensing, military, and astronomy. Furthermore, how to generate high-bandwidth, uniformly spectral density, and easily implementable noise sources has become an important research area.

[0003] Currently, most noise sources are based on random processes in electronic devices. A typical method is to control and amplify the noise in physical devices such as resistors, avalanche diodes, and field-effect transistors to generate Gaussian white noise. However, this method can only generate noise with a bandwidth on the order of MHz. In addition, these noise sources often require the use of electrical amplifiers to amplify the output noise, making the entire system more complex, and the flatness of the output noise deteriorates as the bandwidth increases.

[0004] Photonics-based noise generation devices can overcome the bottleneck of electronic bandwidth, thereby achieving broadband noise signal generation. Typical optical noise includes laser phase noise and amplified spontaneous emission noise. In addition, chaotic lasers, due to their high bandwidth, large amplitude, and noise-like characteristics, can also be used as noise sources. For example, phase noise based on vertical-cavity surface-emitting lasers can generate optical noise signals of nearly 1 GHz [Physical Review E, 2010, 81(5), 051137]; broadband noise signals with a bandwidth of about 12 GHz can also be generated by using superluminescent diodes combined with photoelectric conversion devices [Optics Letters, 2011, 36(6), 1020-1022]; and optical heterodyne can be performed using chaotic lasers generated by two semiconductor lasers with external feedback to generate noise signals with a bandwidth of 16.7 GHz [Optics Letters, 2017, 25(4), 3153-3164]. Compared with noise signals generated by electronic technology, the bandwidth of noise signals obtained by photonics-based noise sources is greatly enhanced.

[0005] However, most of the aforementioned devices are constructed from multiple discrete optical components, resulting in complex structures, large sizes, susceptibility to environmental influences, and poor stability. They also generate limited bandwidths of only tens of gigabits per second, and their noise bandwidth lacks scalability, thus restricting the application of the noise source. Therefore, developing a high-bandwidth, scalable, uniformly spectral density, highly stable, and easily implementable on-chip white noise source is crucial. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an on-chip ultrawideband white noise source based on a chaotic micro-ring optical frequency comb.

[0007] The objective of this invention can be achieved by employing the following technical measures: designing an on-chip ultrawideband white noise source based on a chaotic micro-ring optical frequency comb, comprising:

[0008] The system comprises a chip substrate, a semiconductor laser array, a microring resonator array, a photodetector, and an optical waveguide. The semiconductor laser, microring resonator, and photodetector are all integrated on the same chip substrate, and the devices are connected via optical waveguides. The laser output from the semiconductor laser is coupled into the microring resonator after transmission through the optical waveguide. Due to modulation instabilities and higher-order nonlinear effects within the microring, a chaotic optical frequency comb is generated after output from the microring. This chaotic optical frequency comb appears as equally spaced frequency combs in the optical frequency domain and as a randomly fluctuating chaotic signal in the time domain. By designing the radius of the microring resonator, the free spectral range of the generated chaotic optical frequency comb is altered, resulting in a sequentially increasing free spectral range. Ultimately, the comb couples to the same waveguide, causing beat frequency interactions between modes, resulting in different frequency bands. These spectra are spliced ​​and superimposed, and finally, after photoelectric conversion by the photodetector, ultra-wideband white noise is output.

[0009] In this structure, a semiconductor laser, a micro-ring resonator, an optical waveguide, and a photodetector are integrated onto the same substrate by bonding, thereby achieving a hybrid integrated on-chip white noise source structure based on a chaotic micro-ring optical frequency comb.

[0010] In this system, the center wavelength of the output laser light from the semiconductor laser is consistent across all lasers. The linewidth of the output laser light from the semiconductor laser must be smaller than the linewidth of the resonant peak in the microring resonator to ensure that the pump light can couple into the ring waveguide of the microring resonator. Furthermore, the center wavelength of the laser output light must be smaller than the wavelength corresponding to the nearest resonant frequency, i.e., located at the blue detuning point of the resonant peak in the microring resonator.

[0011] The microring resonator includes any one of the following structures: all-through, up-and-down channel, non-concentric circle, and racetrack. The ring waveguide and straight waveguide materials of the microring resonator are silicon, lithium niobate, and high-refractive-index-difference-doped glass. The quality factor Q of the selected microring resonator is greater than 10. 5 .

[0012] The nonlinear effects in the micro-ring resonator include four-wave mixing, self-phase modulation, and cross-phase modulation.

[0013] The free spectral range of the chaotic microring optical frequency comb can be achieved by changing the perimeter of the microring resonator, with the radius of the microring resonator increasing sequentially. The free spectral range of the chaotic microring optical frequency comb is calculated using the following formula: Where Δλ represents the free spectral range of the microring resonator, λ is the center wavelength of the laser output light, and n g Let be the group refractive index of the microring resonator waveguide, and L be the perimeter of the microring resonator.

[0014] In this system, chaotic micro-ring optical frequency combs with different free spectral ranges are coupled onto the same waveguide. Beat frequencies between modes generate white noise with corresponding center frequencies. The center frequency of the white noise is determined by the frequency difference between the corresponding modes. White noise with different center frequencies is spliced ​​together to ultimately produce ultra-wideband white noise. Furthermore, by increasing the number of paths and comb teeth of the chaotic micro-ring optical frequency comb, more modes can beat frequencies, which can further improve the white noise bandwidth.

[0015] The advantages and positive effects of implementing the on-chip ultrawideband white noise source based on chaotic micro-ring optical frequency comb provided by the present invention are as follows:

[0016] 1. This technical solution provides a hybrid integrated on-chip white noise source. It introduces a chaotic micro-ring optical frequency comb and integrates a micro-ring resonator, semiconductor laser, optical waveguide, and photodetector onto the same chip, connected via the optical waveguide. Compared to discrete solutions, it offers advantages such as simpler structure, smaller size, lower power consumption, and higher stability.

[0017] 2. This technical solution utilizes optical methods to generate broadband white noise and effectively avoids the bottleneck of electronic bandwidth through photoelectric conversion. By increasing the number of paths of the chaotic micro-ring optical frequency comb and the number of comb teeth of the single-path optical frequency comb, higher bandwidth white noise generation can be achieved, which has scalability. Attached Figure Description

[0018] Figure 1 is a schematic diagram of an on-chip ultrawideband white noise source based on a chaotic micro-ring optical frequency comb provided by the present invention.

[0019] Figure 2 is a schematic diagram of the spectrum of a single-channel chaotic optical frequency comb of an ultra-wideband white noise source based on a chaotic micro-ring optical frequency comb provided by the present invention.

[0020] Figure 3 is a schematic diagram of the spectrum of a single mode of a ten-channel chaotic optical frequency comb of an ultra-wideband white noise source based on a chaotic micro-ring optical frequency comb provided by the present invention.

[0021] Figure 4 is a schematic diagram of the power spectrum of an on-chip ultrawideband white noise source based on a chaotic micro-ring optical frequency comb provided by the present invention. Detailed Implementation

[0022] The technical measures of the present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can have a clearer understanding of the purpose, advantages, and technical measures of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the practical examples in the present invention, any other practical examples obtained by other skilled in the art without creative effort can be classified as within the protection scope of the present invention.

[0023] As shown in Figure 1, the structure of an ultrawideband white noise source based on a chaotic micro-ring optical frequency comb provided by the present invention includes: a chip substrate 1, a semiconductor laser 2, a micro-ring resonant cavity 3, an optical waveguide 4, and a photodetector 5.

[0024] In this system, the semiconductor laser 2, microring resonator 3, optical waveguide 4, and photodetector 5 are all integrated on the chip substrate 1. The laser emitted by the semiconductor laser 2 is used as pump light and coupled into the microring resonator 3. Due to modulation instability and higher-order nonlinear effects within the microring, a microring chaotic comb is generated. All connections between the devices are made via the optical waveguide 4 to achieve optical signal transmission throughout the optical path. The microring resonator 3 generates m chaotic microring optical frequency combs with different free spectral ranges. After being transmitted through the waveguide and converged into a single comb, beat frequencies occur between the corresponding longitudinal modes, generating different frequency bands. The spacing between these bands is determined by the frequency difference between the comb teeth. By appropriately selecting the optical frequency difference between each band, the resulting frequency bands with different center frequencies are spliced ​​together, ultimately outputting ultra-wideband white noise by the photodetector 5.

[0025] The pump light of the chaotic micro-ring optical frequency comb is defined as mode 0, and the two adjacent modes of the pump light are defined as +1 mode and -1 mode, respectively. Taking the beat frequency between a single mode (+1 mode) of two chaotic micro-ring optical frequency combs as an example, assuming that the center wavelengths of the two modes are λ1 and λ2, the beat frequency between these two modes will generate two bands of white noise. The center frequency of one band is at the DC component, and the center frequency of the other band is f. th Determined by the optical frequency difference between the two modes, it can be expressed as f th = c / l1 - c / l2. The beat frequency interaction between modes corresponds to the convolution principle. In principle, the photogenerated current i(t) of the photodetector can be expressed as the convolution of the detector response function r(t) with the two laser beam fields E1(t) and E2(t): Therefore, the power spectrum S(f) of the detector output electrical signal is expressed as:

[0026] S(f)=|F{i(t}| 2=|R(f)| 2 ×[S1(v)*S1(v)+S2(v)*S2(v)+2S1(v)*S2(v)], where S(v1) represents the spectral density of the first mode and S(v2) represents the spectral density of the second mode. v1 and v2 are the center frequencies of the two modes, respectively.

[0027] Specifically, this invention uses a silicon photonics chip as a substrate and integrates a semiconductor laser, a microring resonator, an optical waveguide, and a photodetector onto the chip via bonding. The microring resonator adopts an all-through structure and is fabricated from high-refractive-index-difference-doped glass, with a Q value ranging from 2 × 10⁻⁶. 6 ~3×10 6 As shown in Figure 2, the chaotic microring optical frequency comb is a broadband light source composed of a series of discrete, equally spaced laser modes. It contains hundreds of modes in the 1500nm–1600nm range, with adjacent longitudinal modes spaced approximately 0.4nm apart. The center wavelength of each longitudinal mode (except the pump light) in each chaotic microring optical frequency comb can be adjusted by changing the radius of the microring resonator. After m chaotic microring optical frequency combs with different center wavelengths are coupled to one waveguide via m waveguides, beat frequencies occur between the modes, generating a spectrum with a corresponding center frequency. The center frequency of the spectrum is determined by the frequency difference between the modes. The resulting spectra are spliced ​​together to ultimately produce ultra-wideband white noise.

[0028] Specifically, we take a ten-channel chaotic micro-ring optical frequency comb as an example. The center wavelength of the semiconductor laser output is 1553nm. By changing the radius of the micro-ring resonator, the free spectral ranges of the resulting ten-channel chaotic micro-ring optical frequency comb are successively 41GHz, 42GHz, ..., 50GHz. As shown in Figure 3, the first mode (λ1, λ2, ..., λ...) of the ten-channel chaotic micro-ring optical frequency comb... 10 The frequency difference between the ten modes is 1 GHz. After the beat frequency between the ten modes is passed through a photodetector, it can generate white noise in ten frequency bands. The center frequency of each band increases by 1 GHz, which can generate white noise with a bandwidth of 10 GHz (10 × 1 GHz). The second mode (λ) 11 , λ 12 、…、λ 20 The frequency difference between each mode is 2 GHz, and the center frequency of the corresponding frequency band increases by 2 GHz sequentially. The frequency of the nth mode is (λ). 10n+1 , λ 10n+2 、…、λ 10n+10The frequency difference between the bands is n GHz, and the center frequency of the corresponding generated bands increases by n GHz sequentially. Bands with different center frequencies are spliced ​​together to ultimately generate broadband white noise. Since the coverage range of the chaotic micro-ring optical frequency comb can reach several hundred nm and n can reach more than 100, if the number of paths m and the number of comb teeth n of the chaotic optical frequency comb are increased, white noise with a wider bandwidth can be generated, as shown in Figure 4.

[0029] It is particularly noteworthy that the on-chip ultrawide white noise source based on a chaotic micro-ring optical frequency comb disclosed in this invention utilizes the beat frequency effect of multiple chaotic micro-ring optical frequency combs and generates white noise through photoelectric conversion. The spectral range of the chaotic micro-ring optical frequency comb can reach several hundred nm, containing hundreds of modes; therefore, beat frequency generation by multiple chaotic micro-ring optical frequency combs can achieve broadband white noise. By introducing a chaotic micro-ring optical frequency comb and integrating a micro-ring resonator, semiconductor laser, waveguide, and photodetector onto the same chip and connecting them via optical waveguides, a compact, highly integrated, and small-sized on-chip white noise source is obtained. Unlike existing technologies, its structure is relatively simple, offering advantages such as high stability and low power consumption. Furthermore, this invention can significantly increase the bandwidth of white noise generation by increasing the number of chaotic micro-ring optical frequency combs and the number of comb teeth in a single comb, demonstrating scalability. The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A superbandwidth white noise source based on a chaotic microring optical frequency comb, comprising 10 semiconductor lasers (2) with the same center wavelength, a microring resonator (3) having the same number of semiconductor lasers (2), and a photodetector (5); wherein, The semiconductor laser (2), micro-ring resonator (3), and photodetector (5) are all integrated on the same chip substrate (1), and the devices are connected by optical waveguides (4); the continuous light output from the semiconductor laser (2) is transmitted through the optical waveguide and then injected into the micro-ring resonator (3); the center wavelength of the laser output from the semiconductor laser is located at the blue detuning point of the resonance peak of the micro-ring resonator, that is, the pump wavelength is smaller than the wavelength corresponding to the nearest resonant frequency. A series of nonlinear effects and dispersion will occur in the micro-ring resonator (3), resulting in a large broadening of the spectrum; after passing through the micro-ring resonator... The cavity (3) outputs chaotic optical frequency combs with equal frequency spacing at the through port; by designing the radius of the micro-ring resonant cavity (3) to generate chaotic optical frequency combs with different free spectral ranges, the chaotic optical frequency combs generated by each micro-ring resonant cavity are coupled to a waveguide and then input into the photodetector (5). After the multiple chaotic optical frequency combs are combined into a waveguide, the beat frequencies of different frequency detuned modes generate white noise with corresponding center frequencies. The generated spectra can be spliced ​​together, and finally ultra-wideband white noise is output from the photodetector (5). The number of chaotic optical frequency combs m and the number of chaotic optical frequency comb teeth n are increased to achieve white noise generation with a bandwidth of (n+1)*10 GHz or more, where n≥100.

2. The ultra-wideband white noise source based on chaotic micro-ring optical frequency comb as described in claim 1, characterized in that: The linewidth of the laser output from a semiconductor laser must be smaller than the linewidth of the resonant peak of the microring resonator.

3. The ultra-wideband white noise source based on chaotic micro-ring optical frequency comb as described in claim 1, characterized in that: Its micro-ring resonator structure can be all-through, up-and-down channel, non-concentric circle, or racetrack type.

4. The ultra-wideband white noise source based on a chaotic micro-ring optical frequency comb as described in claim 1, characterized in that: When the laser output from a semiconductor laser is injected into a microring resonant cavity, it undergoes a combination of four-wave mixing, self-phase modulation, cross-phase modulation, and dispersion.

5. The ultra-wideband white noise source based on a chaotic micro-ring optical frequency comb as described in claim 1, characterized in that: The free spectral range of a chaotic optical frequency comb can be tuned by changing the radius of the microring resonator, and the free spectral ranges of the resulting multiple chaotic optical frequency combs increase sequentially, while the frequency detuning between corresponding modes of the chaotic optical frequency comb gradually increases. The free spectral range of the chaotic microring optical frequency comb is calculated using the following formula: ;in, λ represents the free spectral range of the microring resonator, λ is the center wavelength of the laser output light, and n g Let be the group refractive index of the microring resonator waveguide, and L be the perimeter of the microring resonator.

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