阅读说明：本技术 近简并多模微腔激光器、随机数产生装置及应用 (Near-degenerate multimode microcavity laser, random number generation device and application ) 是由 肖金龙 马春光 肖志雄 郝友增 杨跃德 黄永箴 于 2020-03-20 设计创作，主要内容包括：一种自发混沌的近简并多模微腔激光器、随机数产生装置及应用,该自发混沌的近简并多模微腔激光器包括一N电极层、一N型衬底、一第一限制层、一有源区层、一第二限制层、一欧姆接触层以及一P电极层；所述第一限制层、有源区层、第二限制层、欧姆接触层、P电极层形成自发混沌的近简并多模谐振腔和耦合于近简并多模谐振腔的直连光波导,所述直连光波导端面设有出光口。本发明的近简并多模微腔激光器具有体积小和不需要外光反馈或光电反馈的优点,使混沌信号在保密通讯、光纤故障检测、随机数产生等领域的应用更加有利,并有效推动了混沌激光在科学研究、工程技术等领域的价值。(A spontaneous chaotic near-degenerate multimode microcavity laser, a random number generation device and application thereof are provided, the spontaneous chaotic near-degenerate multimode microcavity laser comprises an N electrode layer, an N-type substrate, a first limiting layer, an active region layer, a second limiting layer, an ohmic contact layer and a P electrode layer; the first limiting layer, the active region layer, the second limiting layer, the ohmic contact layer and the P electrode layer form a spontaneous chaotic near-degenerate multimode resonant cavity and a direct-connection optical waveguide coupled with the near-degenerate multimode resonant cavity, and an optical outlet is formed in the end face of the direct-connection optical waveguide. The near-degenerate multimode microcavity laser has the advantages of small volume and no need of external light feedback or photoelectric feedback, so that the application of chaotic signals in the fields of secret communication, optical fiber fault detection, random number generation and the like is more favorable, and the value of the chaotic laser in the fields of scientific research, engineering technology and the like is effectively promoted.)

1. A spontaneously chaotic nearly degenerate multimode microcavity laser, comprising:

an N electrode layer (101) for providing a current injection path;

an N-type substrate (102) for providing mechanical support for the laser;

a first confinement layer (103) for providing confinement of the laser optical field;

an active region layer (104) for providing a laser gain medium;

a second confinement layer (105) for providing confinement of the laser optical field;

an ohmic contact layer (106) for reducing contact resistance; and

a P electrode layer (107) for providing a current injection path;

the first limiting layer (103), the active region layer (104), the second limiting layer (105), the ohmic contact layer (106) and the P electrode layer (107) form a spontaneous chaotic near degenerate multimode resonant cavity (11) and a direct-connected optical waveguide (12) coupled with the near degenerate multimode resonant cavity (11), and an optical outlet (108) is formed in the end face of the direct-connected optical waveguide.

2. The nearly degenerate multimode microcavity laser of claim 1,

the nearly degenerate multimode resonator (11) is based on a total internal reflection mode or a whispering gallery mode.

3. The nearly degenerate multimode microcavity laser of claim 1,

the light outlet (108) is of a film coating structure of a cleavage surface or an end surface.

4. The nearly degenerate multimode microcavity laser of claim 1,

the nearly degenerate multimode resonant cavity (11) comprises structures of an arc-edge hexagon, an arc-edge quadrangle and an arc-edge octagon.

5. The nearly degenerate multimode microcavity laser of claim 1,

the active region layer (104) is an undoped multiple quantum well or quantum dot structure.

6. The nearly degenerate multimode microcavity laser of claim 1,

the ohmic contact layer (106) is of a P-type doped structure.

7. The nearly degenerate multimode microcavity laser of claim 1,

the nearly degenerate multimode microcavity laser does not require external light injection, optical or electrical feedback.

8. A random number generating apparatus, comprising:

a nearly degenerate multimode microcavity laser (1) as claimed in any one of claims 1 to 7 for generating chaotic laser light;

the photoelectric detector (2) is used for converting the optical signal of the chaotic laser into an electric signal;

a blocking capacitor (3) for filtering the direct current component of the electrical signal, retaining only the alternating current component; and

and the analog-to-digital converter (5) converts the analog electric signal into a digital signal at a high speed, extracts the ADC least significant bit as a true random number, converts the analog filtered electric signal into the digital signal and extracts the ADC least significant bit as the true random number.

9. The random number generating apparatus according to claim 8,

the random number generating device further comprises an electrical amplifier (4) for amplifying the electrical signal, the electrical amplifier (4) being arranged between the blocking capacitor (3) and the analog-to-digital converter (5).

10. Use of the nearly degenerate multimode microcavity laser according to any one of claims 1 to 7 or the random number generating device according to claim 8 or 9 in the fields of monte carlo simulation, massively parallel computing and secure communications.

Technical Field

The invention relates to the field of semiconductor optoelectronics, optical communication and scientific calculation, in particular to a spontaneous chaotic near-degenerate multimode microcavity laser, a random number generation device and application.

Background

The random number is used as a key sampling source of Monte Carlo simulation and secret communication, and has important application value in scientific calculation, communication safety and daily life of people. Random numbers play a crucial role in key generation of classical and quantum cryptography systems, reliability and random simulation of modern network society, and the like. The generation of random numbers can be divided into two types, one type is a pseudo-random number generator based on an algorithm seed source, but unpredictability is limited, along with the continuous improvement of the computing capability of a computer, the event cracked by taking a pseudo-random number as a secret key is endless, and national defense safety, financial safety and personal privacy are greatly threatened; another type is a true random number generator based on a natural physical entropy source, including resistance thermal noise, chaotic circuits, oscillator phase noise, single photon randomness, etc., which has been applied to generate non-deterministic true random number sequences. However, due to the low signal level of physical noise and post-processing amplification requirements, the random process produces a non-deterministic sequence of random numbers with a yield of less than 100 Mbps. There is still a large gap between this and the speed of current scientific computing and communication systems.

The chaotic semiconductor laser has been widely researched to generate true random numbers and secure communication in order to realize the chaotic laser, and the current research is mainly focused on an external optical feedback semiconductor laser, an optical injection semiconductor laser, a passive feedback cavity integrated laser and the like. The chaotic semiconductor laser with external optical feedback is generally used for random number generation, optical time domain reflectometry, chaotic laser radar, and the like. However, the time-lapse periodicity in the laser output reduces the safety and randomness of the system, often requiring post-processing.

All the chaos laser chips developed at present adopt a time delay optical feedback structure. The feedback cavity length of the multi-feedback cavity or the single-feedback cavity is a fixed value. The fixed feedback cavity length can enable the generated chaotic signal to carry a time delay characteristic, so that the chaotic signal has certain periodicity, which is very unfavorable for the application of chaotic laser in the fields of secret communication, high-speed random number generation and the like.

An optical microcavity laser represented by a whispering gallery mode microdisk laser realizes strong limitation on an optical field by utilizing side wall total reflection, generates a whispering gallery mode with extremely high quality factor (Q factor) in a microcavity, and has the characteristics of small mode volume, low power consumption and high speed. Through reasonable design, the micro-cavity can realize that the basic transverse mode and the first-order transverse mode of different longitudinal modes of the micro-cavity have higher quality factors, and can control the wavelength intervals of different transverse modes, thereby obtaining nearly degenerate multimode and further generating chaotic signals. Compared with other chaotic signal generating methods such as external light injection or light feedback of the laser, the chaotic signal generating system utilizing the microcavity laser has the advantages of simple structure, small volume, low cost, easy integration and the like.

Disclosure of Invention

It is therefore one of the primary objectives of the claimed invention to provide a nearly degenerate multimode microcavity laser, a random number generator and an application thereof, so as to at least partially solve at least one of the above technical problems.

To achieve the above object, as one aspect of the present invention, there is provided a near degenerate multimode microcavity laser of spontaneous chaos, comprising:

an N electrode layer for providing a current injection channel;

an N-type substrate for providing mechanical support for the laser;

a first confinement layer for providing laser optical field confinement;

an active region layer for providing a laser gain medium;

a second confinement layer for providing confinement of the laser optical field;

an ohmic contact layer for reducing contact resistance; and

a P electrode layer for providing a current injection channel;

the first limiting layer, the active region layer, the second limiting layer, the ohmic contact layer and the P electrode layer form a spontaneous chaotic near-degenerate multimode resonant cavity and a direct-connection optical waveguide coupled with the near-degenerate multimode resonant cavity, and an optical outlet is formed in the end face of the direct-connection optical waveguide.

As another aspect of the present invention, there is also provided a random number generating apparatus including:

the nearly degenerate multimode microcavity laser is used for generating chaotic laser;

the photoelectric detector is used for converting the optical signal of the chaotic laser into an electric signal;

a DC blocking capacitor for filtering the DC component of the electrical signal and retaining only the AC component; and

and the analog-to-digital converter is used for converting the analog electric signal into a digital signal at a high speed, extracting the ADC least significant bit as a true random number, converting the analog filtered electric signal into the digital signal and extracting the ADC least significant bit as the true random number.

As a further aspect of the present invention, there is also provided an application of the nearly degenerate multimode microcavity laser or the random number generation device as described above in the fields of monte carlo simulation, massively parallel computing and secure communication.

Based on the above technical solution, the nearly degenerate multimode microcavity laser, the random number generator and the application of the invention have at least one of the following advantages compared with the prior art:

the near-degenerate multimode microcavity laser with the spontaneous chaos provided by the invention has the advantages of small volume and no need of external light feedback or photoelectric feedback, so that the chaotic signal is more favorably applied to the fields of secret communication, optical fiber fault detection, random number generation and the like, and the value of the chaotic laser in the fields of scientific research, engineering technology and the like is effectively promoted;

the spontaneous chaotic near-degenerate multimode microcavity laser and the random number generating device have simple structure and stable performance, and finally can obtain a broadband chaotic laser signal and a true random number without time delay;

the invention is suitable for the fields of chaotic secure communication, chaotic laser radar, high-speed random number generation, distributed optical fiber sensing, optical fiber network fault detection, Monte Carlo simulation, large-scale parallel computation and the like.

Drawings

FIG. 1 is a schematic diagram of a random number generator according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a spontaneously chaotic nearly degenerate multimode microcavity laser according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an arc-edge hexagonal cavity structure with an output waveguide according to an embodiment of the present invention;

FIG. 4 is a graph of fundamental transverse mode H at a wavelength of 1551.6nm, corresponding to the structure of FIG. 2, in accordance with an example of the present invention₀And a first order transverse mode H₁A magnetic field | Hz | mode field distribution diagram in the z direction is obtained;

FIG. 5 is a graph of power-current, voltage-current curves for a microcavity laser in accordance with an example provided by the present invention;

FIG. 6 is a fine spectrum of a microcavity laser at an injection current of 24.7mA in accordance with an embodiment of the present invention;

FIG. 7 is a frequency spectrum diagram of a microcavity laser at an injection current of 24.7mA according to an embodiment of the present invention;

FIG. 8 is a graph of intensity series (a graph) and a probability density distribution graph (b graph) of the intensity series over time obtained by an example random number generation apparatus provided in the present invention;

FIG. 9 is a graph of an autocorrelation function of a broadband chaotic waveform in an example provided by the present invention;

FIG. 10 is a graph showing the correlation dimensions of the intensity sequence computational dynamics obtained experimentally in the examples provided by the present invention.

Description of reference numerals:

1-a nearly degenerate multimode microcavity laser, 2-a high-speed photodetector, 3-a blocking capacitor, 4-an electrical amplifier and 5-an analog-to-digital converter (ADC);

11-resonant cavity, 12-direct connection optical waveguide, 101-N electrode layer, 102-N type substrate, 103-lower limiting layer, 104-active region layer, 105-upper limiting layer, 106-ohmic contact layer, 107-P electrode layer and 108-light outlet.

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

The invention provides a spontaneous chaotic near-degenerate multimode microcavity laser and a random number generating device, aiming at solving the problems that chaotic laser generated by the conventional chaotic semiconductor laser has a time delay characteristic and a generated true random number has a certain weak periodicity.

The invention discloses a spontaneous chaotic near-degenerate multimode microcavity laser, which comprises:

an N electrode layer for providing a current injection channel;

an N-type substrate for providing mechanical support for the laser;

a first confinement layer for providing laser optical field confinement;

an active region layer for providing a laser gain medium;

a second confinement layer for providing confinement of the laser optical field;

an ohmic contact layer for reducing contact resistance; and

a P electrode layer for providing a current injection channel;

the first limiting layer, the active region layer, the second limiting layer, the ohmic contact layer and the P electrode layer form a spontaneous chaotic near-degenerate multimode resonant cavity and a direct-connected optical waveguide coupled with the resonant cavity, and an optical outlet is formed in the end face of the direct-connected optical waveguide.

In some embodiments of the invention, the nearly degenerate multimode resonator is based on total internal reflection modes or whispering gallery modes.

In some embodiments of the present invention, the light outlet is a cleavage plane or an end-face coating structure.

In some embodiments of the present invention, the nearly degenerate multimode resonator comprises an arc-sided hexagonal, arc-sided quadrangular, or arc-sided octagonal structure.

In some embodiments of the invention, the active region layer is an undoped multiple quantum well or quantum dot structure.

In some embodiments of the present invention, the ohmic contact layer is a P-type doped structure.

In some embodiments of the present invention, the nearly degenerate multimode microcavity laser does not require external light injection, optical or electrical feedback.

The invention also discloses a random number generating device, comprising:

the nearly degenerate multimode microcavity laser is used for generating chaotic laser;

the photoelectric detector is used for converting the optical signal of the chaotic laser into an electric signal;

a DC blocking capacitor for filtering the DC component of the electrical signal and retaining only the AC component; and

and the analog-to-digital converter is used for converting the analog electric signal into a digital signal at a high speed, extracting the ADC least significant bit as a true random number, converting the analog filtered electric signal into the digital signal and extracting the ADC least significant bit as the true random number.

In some embodiments of the invention, the random number generating means further comprises an electrical amplifier for amplifying the electrical signal, the electrical amplifier being arranged between the blocking capacitor and the analog-to-digital converter.

The invention also discloses the application of the near-degenerate multimode microcavity laser or the random number generation device in the fields of Monte Carlo simulation, large-scale parallel computation and secret communication.

In an exemplary embodiment, the random number generating apparatus of the near-degenerate multimode microcavity laser based on spontaneous chaos of the present invention comprises the following structure:

a nearly degenerate multi-mode microcavity semiconductor laser 1 capable of generating high quality factor (Q factor) based transverse mode, first order transverse mode;

a high-speed photodetector 2;

a blocking capacitor 3;

an electric amplifier 4;

an analog-to-digital converter ADC 5.

The spontaneous chaotic near-degenerate multimode microcavity laser 1 comprises the following structure:

a resonator 11 based on total internal reflection mode (whispering gallery mode);

a direct-coupled optical waveguide 12 directly coupled to the resonant cavity, wherein a light outlet formed on the end surface of the waveguide is a cleavage surface or an end surface coating structure;

an N electrode layer 101;

an N-type substrate 102;

a lower confinement layer 103 (i.e., a first confinement layer);

an undoped multiple quantum well active region layer 104;

an upper confinement layer 105 (i.e., a second confinement layer);

a P-type heavily doped ohmic contact layer 106;

a P electrode layer 107;

a light outlet 108.

The whispering gallery mode resonant cavity 11 and the direct-connected waveguide 12 are used together as an integral resonant cavity, an amplified stimulated radiation optical field is formed in the resonant cavity due to spontaneous radiation of a semiconductor and external current injection, a fundamental transverse mode, a first-order transverse mode and the like corresponding to different longitudinal mode orders are formed in the optical field in the resonant cavity, and the near degenerate multimode beat frequency forms chaotic laser. Due to the appropriate resonant cavity structure parameters and/or the appropriate current injection parameters, the generated different mode intervals can not be too large, and meanwhile, the nonlinear processes of single-period oscillation, double-period oscillation, four-wave mixing and the like of the semiconductor laser are avoided. The Q factors of different modes are relatively close to each other, and a nearly degenerate mode is formed. The chaotic laser is output at the light outlet 108 along the direct-connected optical waveguide 12 under the condition of external current injection.

The nearly degenerate multimode microcavity laser 1 does not require external light injection and/or optical (electrical) feedback.

In the nearly degenerate multimode microcavity laser 1, a current is applied to a directly connected optical waveguide 12 directly coupled to the cavity, and the directly connected optical waveguide can be used as an optical amplifier.

The high-speed photodetector 2 converts an optical signal into an electrical signal.

The blocking capacitor 3 filters the dc component of the electrical signal and only keeps the ac component.

The electrical amplifier 4 amplifies the ac electrical signal. The electrical amplifier 4 can be omitted from the system if the strength of the ac signal is sufficient.

The ADC5 converts the analog electrical signal into a digital signal at a high speed, and extracts the ADC least significant bit as a true random number.

The resonant cavity structure can be, but is not limited to, the shape of the example of the invention, and can also be other resonant cavity structures. The resonant cavity can generate nearly degenerate multimode.

The technical solution of the present invention is further illustrated by the following specific embodiments in conjunction with the accompanying drawings. It should be noted that the following specific examples are given by way of illustration only and the scope of the present invention is not limited thereto.

Referring to fig. 1, the random number generating apparatus of the present embodiment includes: a nearly degenerate multimode microcavity laser 1 capable of generating high Q-factor fundamental transverse mode and first-order transverse mode, a high-speed photodetector 2, a blocking capacitor 3, an electrical amplifier 4, and an analog-to-digital converter ADC 5.

A nearly degenerate multimode microcavity laser 1 capable of generating high Q-factor fundamental transverse mode and first-order transverse mode includes: the optical waveguide structure comprises a resonant cavity 11 based on a total internal reflection mode (whispering gallery mode), a direct-coupled optical waveguide 12 directly coupled to the resonant cavity, a waveguide end face which is a cleavage face or an end face coating structure, an N electrode layer 101, an N-type substrate 102, a lower limiting layer 103, an undoped multi-quantum well active region layer 104, an upper limiting layer 105, a P-type heavily doped ohmic contact layer 106, a P electrode layer 107 and a light outlet 108.

The chaotic light signal output by the near-degenerate multimode microcavity laser 1 is received by the high-speed photoelectric detector 2, is converted into an electric signal through the photoelectric conversion process, the direct-current component of the electric signal is filtered through the blocking capacitor 3 to retain an alternating-current signal, the alternating-current signal is amplified through the electric amplifier 4 (when the intensity of the alternating-current signal can meet the requirement, the electric amplifier 4 can be omitted from the system), the alternating-current signal is accessed into the 8-bit high-speed ADC5, the sampling frequency is 5GSa/s, and the lowest 2-bit effective bit is selected to be output as a true random number. Wherein the current is applied to a directly connected optical waveguide 12 directly coupled to the resonant cavity in the nearly degenerate multimode microcavity laser 1, and the directly connected optical waveguide can be used as an optical amplifier.

The purpose and advantages of the present invention will be described by taking an arc-edge hexagon as an example of a whispering gallery mode resonator, which will be described with reference to the examples and the accompanying drawings.

The whispering gallery modes have high Q factors, and the period lengths of different transverse modes caused by the arc edges are different, so that the multi-transverse-mode laser with adjustable mode intervals can be realized. The mode Q factor can be further improved by replacing the hexagonal flat edge with the arc edge, and the frequency interval of the transverse modes with different longitudinal moduli is adjusted to the GHz magnitude. In an actual non-ideal smooth boundary microresonator, there are two degenerate modes with the same number of transverse and longitudinal modes in addition to different transverse modes, and the degenerate modes split. The frequency separation of the four modes is accordingly designed to be in the GHz range, which results in a nearly degenerate multimode beat frequency inside the microresonator.

An arc-edge hexagonal resonant cavity structure with an output waveguide as shown in fig. 3 on an x-y plane is simulated by a two-dimensional finite element method, wherein r is the radius of an arc edge, a is the length of a flat edge of an original hexagon, w is the width of the output waveguide connected with a vertex at an angle of theta, and delta is a deformation parameter. The effective refractive index of the AlGaInAs/InP multi-quantum well laser resonant cavity is taken as 3.2, and the effective refractive index outside the resonant cavity is taken as 1.54. For a resonant cavity with a of 10 μm, w of 1.5 μm and θ of 55 °, all modes with high Q-factors around the lasing wavelength are calculated, with two fundamental transverse modes H at δ of 1.015 μm₀The Q factor of the degenerate mode of (a) is about 6.0X 10⁵Two first order transverse modes H₁Has a Q factor of about 1.0X 10⁴。

The z-direction magnetic field (| H) is plotted in FIG. 4_z|) distribution in which the waveguide section field strength is amplified by a factor of 10. For a wavelength of 1551.6nm with a higher Q factorH₀And H₁Mode, the field in the output waveguide is amplified by a factor of 5, as shown in fig. 4a and 4 b. Due to the concave mirror effect of the arc edge, the mode field distribution of the hexagon is well limited, the mode field distribution at the vertex of the hexagon is weak, the radiation loss is small, and the Q factor is high.

Considering degenerate modes, there are four high Q modes, labeled H_0，1And H_0，2，H_1，1And H_1，2The first subscript and the second subscript denote the transverse modulus and the degenerate modulus, respectively. To simulate a real device, a sidewall-deformed hexagonal resonator modulated by random fluctuations was simulated. Taking the fluctuation amplitude, H, of 50nm₀And H₁The Q factors of the modes are respectively 0.3 multiplied by 10⁵And 0.8X 10⁴Splitting degenerate mode H_0，1And H_0，2The modal frequency separation of (a) is in the order of GHz.

Fig. 5 shows the power-current, voltage-current curves of the microcavity laser in this example. The curve shows that the device achieves room temperature continuous electro-injection lasing.

Fig. 6 shows a fine spectrum of the microcavity laser at an injection current of 24.7mA in this example. The spectral line of the spectrum is broadened, and the whole observed spectrum is represented as a chaotic spectrum.

Fig. 7 shows the power spectrum of the electrical signal generated by amplifying the output optical signal of the microcavity laser and converting the amplified output optical signal on the high-speed photodetector, and the gray color is the noise of the spectrometer. The injection current is 24.7mA, and the result proves that the micro-cavity laser generates chaos in the example.

Fig. 8 is a graph showing intensity sequences (a) and a graph showing probability density distribution (b) of the intensity sequences over time obtained by the random number generation apparatus described in this example, and this result demonstrates that random sequences are generated in this example.

Fig. 9 shows that in this example, since the method does not adopt a feedback manner and does not involve time lag, the autocorrelation function table of the broadband chaotic waveform is in a delta function form, and no correlation occurs for a time width exceeding a central peak value.

Fig. 10 shows that in the example provided by the present invention, in order to determine the dimension of the chaotic attractor, the correlation dimension of dynamics is calculated by using the GP algorithm (correlation dimension algorithm) under different embedding dimensions d for the intensity sequence obtained by the random number generation apparatus, and the result shows that the correlation dimension of the random number obtained by the example provided by the present invention is 5.4.

Table 1 shows that the random bits obtained in the random number generating apparatus provided in this example were tested by the national institute of standards and technology NIST 800-22 random number sequence test template, indicating that the generated bits are true random numbers.

It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. In addition, the above definitions of the various elements are not limited to the specific structures, shapes or modes mentioned in the embodiments, and those skilled in the art may easily modify or replace them, for example:

(1) directional phrases used in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., refer only to the orientation of the drawings and are not intended to limit the scope of the present disclosure;

(2) the embodiments described above may be mixed and matched with each other or with other embodiments based on design and reliability considerations, i.e. technical features in different embodiments may be freely combined to form further embodiments.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.