A random signal generation device based on a saturable absorber semiconductor laser

Abstract

The application belongs to the technical field of random number generation, and particularly relates to a random signal generation device based on a saturable absorber semiconductor laser. The device comprises a random self-pulsation entropy source, a photodetector and a pulse amplitude quantization module. The random self-pulsation entropy source adopts a saturable absorber semiconductor laser (preferably a DFB-SA structure), generates optical pulses with random amplitudes and stable repetition periods by injecting a driving current in a gain region and applying a reverse bias voltage in an absorption region; the photodetector adopts a PIN photodiode or an avalanche photodiode to convert the optical pulses into corresponding electrical pulses; and the pulse amplitude quantization module comprises a differential comparator and a peak detection circuit, which quantizes the peak value of the electrical pulses in each pulse period by using a fixed threshold or an adaptive threshold to generate a random bit sequence. The application realizes high-speed and high-stability random signal generation without an external electric clock, an ADC and digital post-processing, and has a simple device structure, low power consumption and high integration.

Description

Technical Field

[0001] This invention relates to the field of random number generation technology, and in particular to a random signal generation device based on a saturable absorber semiconductor laser, belonging to the fields of secure communication, quantum cryptography, and high-speed information processing. Background Technology

[0002] In modern secure communication, quantum cryptography, and high-speed information processing systems, secure and reliable random numbers are the core foundation for ensuring system security. Physical random numbers, which originate from unpredictable random physical processes in nature, have advantages over pseudo-random sequences generated by traditional algorithms, such as unpredictability and difficulty in reproduction. Therefore, they have become a key direction for current research and engineering implementation. In particular, chaotic random signals generated by the nonlinear dynamic behavior of laser systems have characteristics such as high bandwidth and large-amplitude random fluctuations, and are widely regarded as the ideal entropy source for building high-speed physical random number generators.

[0003] Currently, existing physical random number generators often use optical feedback, optically injected semiconductor lasers, or electro-optic modulation systems as entropy sources to generate continuous chaotic optical signals with bandwidths up to tens of GHz. However, such signals are essentially analog waveforms with continuously random variations in time-series amplitude and cannot be directly used for digital random number generation. Therefore, in existing random number generators, a high-speed electrical analog-to-digital converter (ADC, including sample-and-hold circuits, comparators, flip-flops, etc.) must be used to sample and quantize the continuous chaotic signal before post-processing to obtain a random bit sequence. However, when the random number generation rate of the device reaches the Gb / s level or higher, the random number generation scheme based on continuous chaotic lasers has significant drawbacks. The electrical sampling process relies on an external high-speed clock, and picosecond-level aperture jitter is unavoidable in actual circuits. This jitter introduces uncertainty in the sampling phase, leading to increased quantization errors, severely degrading the signal-to-noise ratio, and causing synchronization difficulties for subsequent logic circuits such as shift registers and XOR gates. Meanwhile, the quantization threshold based on continuous chaotic signals will drift over time, requiring frequent calibration, which reduces system stability and reliability in engineering applications.

[0004] A search of existing technical literature revealed a patent with application number 201811035134.1, entitled "A High-Speed ​​Physical Random Number Generator Based on a Chaotic Laser Entropy Source." This patent includes an entropy source module and a post-processing module. The entropy source module emits two broadband chaotic signals with suppressed time delay characteristics, enhanced bandwidth, and low cross-correlation. The post-processing module converts the two chaotic signals into digital signals and processes them to obtain high-speed random numbers. Compared to pseudo-random number generators, this patent generates non-periodic random numbers and can generate unreproducible random numbers of arbitrary length. Compared to traditional physical random number generators, the entropy source bandwidth is larger, reaching tens of GHz, and can obtain high-speed physical random numbers with a code rate of hundreds of Gbits / s. However, this patent's solution shares the same limitations as the aforementioned continuous chaotic optical random number generation method: its entropy source output is still a continuous analog waveform, requiring high-speed analog-to-digital conversion and clock sampling to obtain a random number sequence, thus remaining constrained by aperture jitter and the complexity of the optical sampling processing link system.

[0005] In conclusion, to simultaneously meet the current application requirements for high speed, high stability, and miniaturization of random signals, it is essential to develop an integrated high-speed random signal generation device that does not require electrical sampling. Summary of the Invention

[0006] The purpose of this invention is to provide a random signal generation device based on a saturable absorber semiconductor laser, which enables high-speed and high-stability random signal generation and has the advantages of simple structure and easy integration. This invention aims to overcome the problem in existing technologies of difficulty in achieving a high-speed random signal generation device with high integration and no need for electrical sampling.

[0007] This invention provides a random signal generation device based on a saturable absorber semiconductor laser, comprising a random self-pulsating entropy source, a photodetector, and a pulse amplitude quantization module connected in sequence. The random self-pulsating entropy source is a saturable absorber semiconductor laser used to generate optical pulses with random amplitude and stable repetition period; the photodetector converts the optical pulses emitted by the random self-pulsating entropy source into electrical pulses corresponding to the pulse waveform; the pulse amplitude quantization module quantizes the peak value of the electrical pulses converted by the photodetector in each pulse period to generate a random bit sequence.

[0008] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, after injecting a driving current into the gain region of the saturable absorber semiconductor laser and applying a reverse bias voltage to the absorption region of the saturable absorber semiconductor laser, the saturable absorber semiconductor laser generates optical pulses with random amplitude and stable repetition period.

[0009] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, the frequency of the optical pulse is increased by adjusting the driving current injected into the gain region.

[0010] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, the frequency of the optical pulse is increased by adjusting the reverse bias voltage applied to the absorption region.

[0011] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, the saturable absorber semiconductor laser adopts an integrated dual-region structure, including: a first region as a distributed feedback region and a second region as a saturable absorber region; The distributed feedback region and the saturable absorber region share a ridge waveguide, and the two regions are electrically isolated from each other. The distributed feedback region is coated with an antireflective film, and the saturable absorber region is coated with a reflective film.

[0012] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, the photodetector includes a PIN photodiode or an avalanche photodiode.

[0013] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, the pulse amplitude quantization module includes a differential comparator.

[0014] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, the threshold of the differential comparator includes a fixed threshold or an adaptive threshold adjusted according to the peak amplitude of the electrical pulse.

[0015] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, a fixed threshold is higher than the noise level in the electrical pulse and is located in the middle region of the random fluctuation of the peak value of the electrical pulse.

[0016] In the random signal generation device based on a saturable absorber semiconductor laser described in this invention, the pulse amplitude quantization module includes a peak detection circuit.

[0017] The advantages and positive effects of the random signal generation device based on a saturable absorber semiconductor laser provided by the present invention are as follows: 1. This technical solution uses a saturable absorber semiconductor laser to generate a sequence of optical pulses with random amplitude fluctuations through a self-pulsating mechanism. After photoelectric conversion, the peak values ​​of each electrical pulse are quantized in real time. No external electrical clock, ADC, or post-processing is required, which avoids the limitations of high-speed electrical sampling and external clock-triggered sampling, and achieves high-speed and high-stability random signal generation effect. 2. The device has a simple overall structure and low power consumption, enabling highly integrated design and facilitating engineering applications; 3. The optical pulse frequency can be flexibly adjusted by changing the drive current in the gain region or the reverse bias voltage in the absorption region to suit different application scenarios with different rate requirements. Attached Figure Description

[0018] Figure 1 A schematic diagram of a random signal generation device based on a saturable absorber semiconductor laser provided by the present invention; Figure 2 A schematic diagram of a random signal generation device based on a saturable absorber semiconductor laser, provided by the present invention, using a single differential comparator structure; Figure 3 This invention provides a schematic diagram of the timing pulses and spectrum of a random signal generation device based on a saturable absorber semiconductor laser when the operating current is increased by increasing the fixed bias voltage of the laser. Figure 4 A schematic diagram of the timing pulses and spectrum of a laser based on a saturable absorber semiconductor laser, provided by the present invention, when the bias voltage is increased while the fixed operating current is increased; Figure 5 A schematic diagram of a random signal generation device based on a saturable absorber semiconductor laser, provided by the present invention, employing a structure of multiple differential comparators; 1. Saturable absorber semiconductor DFB laser; 2. Photodetector; 3. Differential comparator; 4. Encoder. Detailed Implementation

[0019] The technical measures of the present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can have a clearer understanding of the purpose, advantages, and technical solutions of the present invention. Any other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the protection scope of the present invention.

[0020] Example 1 like Figure 1 As shown, this embodiment proposes a random signal generation device based on a saturable absorber semiconductor laser, including a random self-pulsating entropy source, a photodetector 2, and a pulse amplitude quantization module. The random self-pulsating entropy source includes a saturable absorber semiconductor laser, used to generate optical pulse signals with random amplitude and stable repetition period. The photodetector 2 is used to convert the optical pulses emitted by the random self-pulsating entropy source into electrical pulses corresponding to the pulse waveform. The pulse amplitude quantization module is used to quantize the peak value of the electrical pulses converted by the photodetector 2 in each pulse period, generating a random bit sequence. Figure 2As shown, the random self-pulsating entropy source includes a saturable absorber semiconductor DFB laser 1, and the pulse amplitude quantization module includes a differential comparator 3. The optical pulse sequence with a stable repetition period and random peak fluctuations output by the saturable absorber semiconductor DFB laser 1 is sent to a photodetector 2, which is a high-speed PIN photodiode. The photodetector 2 converts the optical pulse sequence into an electrical pulse signal corresponding to the pulse waveform. This electrical pulse signal maintains the periodicity and peak randomness of the optical pulses and serves as a reliable input for the electronic entropy source. The negative terminal of the differential comparator 3 receives a reference voltage. The reference voltage A level value set between the peak value and the minimum value of the electrical pulse signal is used for threshold quantization of the electrical pulse signal; wherein, and These represent the maximum and minimum values ​​of the electrical pulse signal output by photodetector 2, respectively. The positive terminal of differential comparator 3 receives the electrical pulse signal converted from photodetector 2 and samples it using the repetition frequency of the saturable absorber semiconductor DFB laser 1 as the clock signal. When the sampled voltage is higher than the reference voltage... When the sampled voltage is lower than the reference voltage, differential comparator 3 outputs a high level (logic "1"); when the sampled voltage is lower than the reference voltage... When the time is right, differential comparator 3 outputs a low level (logic "0").

[0021] Through the above comparison and quantization process, random optical pulse signals are converted into random binary bit streams, thereby generating gigabit-level random signals.

[0022] Example 2 This embodiment further provides a supplementary description of the random signal generation device based on a saturable absorber semiconductor laser proposed in the above embodiment.

[0023] By injecting a driving current into the gain region of a saturable absorber semiconductor laser and applying a reverse bias voltage to the absorption region, the saturable absorber semiconductor laser generates optical pulses with random amplitudes and stable repetition periods.

[0024] In practice, a driving current is injected into the gain region and a reverse bias voltage is applied to the absorption region. The saturable absorber semiconductor laser enters a random self-pulsating state. The optical pulse sequence output by the random self-pulsation has a fixed time repetition period, while the peak amplitude of the pulses fluctuates randomly due to the nonlinear dynamics of carrier-photon interaction within the laser. This randomness originates from the mutual coupling between carrier density and optical field intensity, as well as the perturbation amplification effect during the regeneration process, and can serve as the physical entropy source of the random number generator.

[0025] The frequency of the optical pulse is increased by adjusting the driving current injected into the gain region.

[0026] In specific implementation, such as Figure 3 As shown, with a fixed bias voltage, increasing the operating current increases the optical pulse repetition rate. When the injection current in the gain region increases, the number of electrons and holes injected into the quantum well increases, the carrier density increases, more photons are generated in the cavity, and the pulse intensity increases. However, the overall carrier pumping rate of the saturable absorber remains unchanged, i.e., the recovery speed does not change. The increase in intensity reduces the pulse duty cycle, thereby increasing the repetition frequency.

[0027] The frequency of the optical pulse is increased by adjusting the reverse bias voltage applied to the absorption region.

[0028] In specific implementation, such as Figure 4 As shown, with a fixed operating current and a changing bias voltage, the optical pulse repetition rate first increases and then decreases. When the bias voltage increases, the carrier pumping rate increases accordingly, but at the same time, the loss effect increases. As the negative voltage increases, the electric field in the saturable absorber region is enhanced, causing carriers to be extracted or recombine more quickly, i.e., increasing the repetition rate. As the negative voltage continues to increase, the electric field in the saturable absorber region is further enhanced, which will over-consume carriers, leading to increased losses. The carrier replenishment rate cannot keep up with the depletion rate, i.e., the repetition rate decreases.

[0029] The saturable absorber semiconductor laser adopts an integrated dual-region structure, including: a first region as a distributed feedback region and a second region as a saturable absorber region; The distributed feedback region and the saturable absorber region share a ridge waveguide, and the two regions are electrically isolated from each other. In the device structure, the end face of the distributed feedback region is designed with an anti-reflection film to reduce light reflection and ensure output stability; while the end face of the saturable absorber region is coated with a high-reflection film to enhance the resonant cavity feedback.

[0030] In practical implementation, the cavity length of the saturable absorber semiconductor DFB laser 1 is 500 mm. This includes providing a gain medium with a length of 490. The distributed feedback region and the length of the saturable absorption effect are 10 The saturable absorber region. No grating is added to the saturable absorber region. The two sections of the structure share a single 2... A wide, straight waveguide is used, electrically isolated in the middle to allow for individual power application and avoid current crosstalk. A reflectivity antireflection coating is deposited on one side of the distributed semiconductor laser region to output pulsed light. A high-reflectivity coating is deposited on one side of the saturable absorption region to cause the laser to reflect and resonate within the cavity.

[0031] The gain region and absorption region of the saturable absorber semiconductor DFB laser 1 are integrated along the longitudinal direction of the laser chip. A driving current is applied to the gain region and a reverse bias voltage is applied to the absorption region. When the gain region of the saturable absorber semiconductor DFB laser 1 is in the stimulated emission region above the threshold and the absorption region is in the saturable absorption operating point with reverse bias, a dynamic imbalance is formed between the gain recovery time and the absorption recovery time, resulting in periodic oscillations between the optical field and the carrier density inside the laser. The laser enters a self-pulsating chaotic state and outputs a sequence of optical pulses with a stable repetitive period and random fluctuations in pulse peaks.

[0032] The photodetector 2 includes a PIN photodiode or an avalanche photodiode.

[0033] In practice, the photodetector 2 can use any component that can provide sufficient bandwidth to maintain the pulse shape, such as a PIN photodiode or an avalanche photodiode. The converted electrical pulse signal maintains the periodic characteristics and peak randomness of the optical pulse.

[0034] The pulse amplitude quantization module includes a differential comparator 3.

[0035] In practical implementation, the pulse amplitude quantization module includes at least one differential comparator 3. This differential comparator 3 performs threshold comparison on the amplitude of the electrical pulse signal and quantizes the pulse peak once within each optical pulse period to generate a corresponding discrete random bit sequence. The triggering timing of the differential comparator 3 is naturally limited by the optical pulse period, thus eliminating the need for a sample-and-hold circuit or a high-speed ADC.

[0036] The threshold of differential comparator 3 includes a fixed threshold or an adaptive threshold adjusted according to the peak amplitude of the electrical pulse (e.g., the threshold is set to the midpoint between the maximum and minimum peak voltages). The fixed threshold is higher than the noise level in the electrical pulse and is located in the middle region of the random fluctuations in the peak value of the electrical pulse. The pulse amplitude quantization module includes a peak detection circuit functionally equivalent to that of differential comparator 3.

[0037] Example 3 To improve the generation rate of random sequences, this embodiment provides a multi-bit random number generation device. For example... Figure 5 As shown, the device includes a saturable absorber semiconductor DFB laser 1, a photodetector 2, multiple differential comparators 3, and an encoder 4. Bit random numbers require ( The differential comparator 3 converts the optical pulse sequence into a random number sequence. The threshold voltage generation circuit is configured to: based on the peak value of the electrical pulse signal... With peak minimum Generate a set of numbers ( ) and the level value is and The threshold voltages that increase sequentially between them ( , , ... ),in The number of bits in the random number to be generated. It is an integer greater than 1.

[0038] The ( The non-inverting input terminals of the three differential comparators 3 are connected together to the output terminal of the photodetector 2 to receive the electrical pulse signal.

[0039] The inverting input of each differential comparator 3 is connected to the threshold voltage generation circuit to receive a corresponding threshold voltage. ( =1 to ( )).

[0040] The input terminal of the encoder 4 is connected to the output terminals of all differential comparators 3, and is used to convert ( The quantized signal output by the differential comparator 3 at the peak moment of the electrical pulse signal is converted into a set of... A sequence of binary random numbers.

[0041] Specifically, at the peak quantization moment of each optical pulse, if the instantaneous voltage of the electrical pulse signal is higher than the threshold voltage corresponding to a certain differential comparator 3, then the differential comparator 3 outputs a high level; otherwise, it outputs a low level. The encoder 4 operates according to this... The combination of ) logic levels is output through encoder 4 to represent the corresponding state. Bit random number.

Claims

1. A random signal generation device based on a saturable absorber semiconductor laser, characterized in that, It includes a random self-pulsating entropy source, a photodetector, and a pulse amplitude quantization module connected in sequence; The random self-pulsating entropy source includes a saturable absorber semiconductor laser for generating optical pulses with random amplitude and stable repetition period. The photodetector is used to convert the light pulses emitted by the random self-pulsating entropy source into electrical pulses corresponding to the pulse waveform; The pulse amplitude quantization module is used to quantize the peak value of the electrical pulse converted by the photodetector in each pulse period to generate a random bit sequence.

2. The random signal generation device based on a saturable absorber semiconductor laser according to claim 1, characterized in that, After injecting a driving current into the gain region of the saturable absorber semiconductor laser and applying a reverse bias voltage to the absorption region of the saturable absorber semiconductor laser, the saturable absorber semiconductor laser generates optical pulses with random amplitude and stable repetition period.

3. The random signal generation device based on a saturable absorber semiconductor laser according to claim 2, characterized in that, The frequency of the optical pulse is increased by adjusting the driving current injected into the gain region.

4. The random signal generation device based on a saturable absorber semiconductor laser according to claim 2, characterized in that, The frequency of the optical pulse is increased by adjusting the reverse bias voltage applied to the absorption region.

5. The random signal generation device based on a saturable absorber semiconductor laser according to claim 1, characterized in that, The saturable absorber semiconductor laser adopts a DFB-SA structure, including: a distributed feedback region of a first preset length and a saturable absorber region of a second preset length. The distributed feedback region and the saturable absorber region share a straight waveguide of a preset width and are electrically isolated from each other. The end face of the distributed feedback region is designed as an antireflective film, and the end face of the saturable absorber region is coated with a high-reflective film.

6. The random signal generation device based on a saturable absorber semiconductor laser according to claim 1, characterized in that, The photodetector includes a PIN photodiode or an avalanche photodiode.

7. The random signal generation device based on a saturable absorber semiconductor laser according to claim 1, characterized in that, The pulse amplitude quantization module includes a differential comparator.

8. The random signal generation device based on a saturable absorber semiconductor laser according to claim 7, characterized in that, The threshold of the differential comparator includes a fixed threshold or an adaptive threshold adjusted according to the peak amplitude of the electrical pulse.

9. The random signal generation device based on a saturable absorber semiconductor laser according to claim 8, characterized in that, The fixed threshold is higher than the noise level in the electrical pulse and is located in the middle region of the random fluctuations in the peak value of the electrical pulse.

10. The random signal generation device based on a saturable absorber semiconductor laser according to claim 7, characterized in that, The pulse amplitude quantization module includes a peak detection circuit.

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