Broadband chaotic laser generating device based on transistor laser photoelectric feedback structure

Abstract

The invention relates to the field of semiconductor photoelectrons, and discloses a chaotic laser generating device based on a transistor laser photoelectric feedback structure. Comprising a transistor laser, an optical coupler, an adjustable optical attenuator, a photoelectric converter and an electric amplifier, wherein the laser output end of the transistor laser is connected with the input end of the optical coupler, an optical signal output by the first output end of the optical coupler is attenuated by the adjustable optical attenuator and then is received by the photoelectric converter and subjected to photoelectric conversion, and an electric signal subjected to photoelectric conversion is amplified by the electric amplifier and then is output to the output end of the transistor laser. The signal is sent to the base electrode of the transistor laser; the transistor laser adopts a common emitter working mode. According to the invention, relaxation oscillation of the transistor laser can be effectively suppressed or even eliminated, so that the bandwidth of chaotic laser is improved.

Description

Technical Field

[0001] The invention relates to the field of semiconductor optoelectronics, and in particular to a chaotic laser generating device based on a transistor laser photoelectric feedback structure. Background Art

[0002] Chaotic lasers have the characteristics of intrinsic randomness, initial value sensitivity, low coherence, and wide spectrum. In recent years, chaotic lasers have important application value in the fields of secure optical communications, ultra-wideband technology, laser radar, optical fiber network fault detection, and distributed optical fiber sensing.

[0003] With the development of science and technology, people's demand for the security, capacity and transmission rate of information transmission is increasing, and they need high-speed, safe and large-capacity communication methods to meet communication needs. Semiconductor lasers are widely used because of their simple structure, easy integration and small size. Since the chaotic signal it generates has the characteristics of noise-like wide spectrum and can fully hide information, the chaotic laser it generates as a physical entropy source has gradually received strong attention. In the prior art, a single-channel optical feedback semiconductor laser is usually used to generate chaotic signals. However, this method will cause the output chaotic laser to have obvious time delay characteristics (TDS) due to the effects of external cavity feedback, thereby restricting the application of chaotic lasers. For example, the performance of high-speed random numbers generated by chaotic lasers as physical entropy sources will deteriorate, so it is important to take appropriate measures to suppress the delay characteristics. On the other hand, the traditional diode laser will accumulate in the active region at the same time as the carrier recombination, which makes the spontaneous recombination lifetime very high, in the nanosecond range, so that the chaotic bandwidth caused by the relaxation oscillation of the diode laser is also greatly limited.

[0004] Therefore, it is necessary to improve the structure of the chaotic laser generating device in the prior art to increase the bandwidth of the chaotic laser. Summary of the invention

[0005] In order to solve the technical problems in the prior art that the chaotic laser generating device has obvious time delay characteristics and the relaxation oscillation leads to limited chaotic bandwidth, the present invention proposes a chaotic laser generating device based on a transistor laser photoelectric feedback structure to generate a wide chaotic laser signal with ultra-wide bandwidth and good flatness.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a broadband chaotic laser generating device based on a transistor laser photoelectric feedback structure, comprising: a transistor laser, an optical coupler, an adjustable optical attenuator, a photoelectric converter, and an electric amplifier; wherein the laser output end of the transistor laser is connected to the input end of the optical coupler, the optical signal output from the first output end of the optical coupler is attenuated by the adjustable optical attenuator and then received by the photoelectric converter and photoelectrically converted, and the electrical signal after the photoelectric conversion is amplified by the electric amplifier and then sent to the base of the transistor laser;

[0007] The transistor laser adopts a common emitter working mode, the emitter electrode is grounded, the base is connected to a current source, the current source is used to provide a driving current for the base of the transistor laser, the collector and the emitter are respectively connected to the two ends of a voltage source, and the voltage source is used to provide a voltage for the collector-emitter of the transistor laser.

[0008] The transistor laser includes a collector electrode layer, a collector region material layer, a base region buffer layer and a base region material layer arranged in sequence from bottom to top, a ridge waveguide is arranged on the base region material layer, and the ridge waveguide includes a p-type lower cladding layer, an n-type lower cladding layer, a lower confinement layer, a quantum well material layer, an upper confinement layer, an emitter region material layer and an emitter electrode layer arranged in sequence from bottom to top; a base electrode layer isolated from the ridge waveguide is also arranged on the base region material layer.

[0009] The p-type lower cladding layer adopts p-doped InAlAs material, and the n-type lower cladding layer adopts n-doped InAlAs material.

[0010] The emitter material layer is n-doped, the base material layer is p-doped, and the collector material layer is n-doped.

[0011] The emission region material layer adopts n-doped InP material; the upper confinement layer adopts InGaAsP material; the quantum well material layer adopts InGaAsP / InP material, and the lower confinement layer adopts InGaAlAs material.

[0012] The base region material layer is made of p-doped InGaAsP material, the base region buffer layer is made of InGaAsP material; and the collector region material layer is made of n-doped InP material.

[0013] The splitting ratio of the second output end of the optical coupler is 10-30%.

[0014] The collector of the transistor laser is connected to an oscilloscope and a spectrum analyzer to characterize the time sequence and spectrum of the chaotic optical signal.

[0015] The transistor laser is an npn type transistor.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention uses a transistor laser to replace the traditional diode laser to generate chaotic laser. The collector junction of the transistor laser is reverse biased, so that the carriers that cannot recombine in a short time in the quantum well are moved to the collector region to form a collector region current, which greatly reduces the recombination life of the base region carriers, thereby effectively suppressing or even eliminating the relaxation oscillation of the transistor laser, thereby improving the bandwidth and making the laser performance better. Moreover, the use of transistor lasers can realize the control of electrical signals and optical signals at the same time, and the bandwidth of transistor lasers can be significantly increased by modulating the collector voltage; therefore, the present invention can generate broadband chaotic laser signals with ultra-wide bandwidth and good flatness.

[0018] 2. Different from the optical feedback and optical injection methods used in the prior art, the photoelectric feedback structure used in the present invention generates chaotic lasers. The optical signal is converted into an electrical signal, which is then injected into the laser after being modulated by a series of nonlinear elements, directly affecting the density of carriers, causing the light field to change. This makes it insensitive to phase changes, and only requires controlling the feedback intensity to achieve adjustable polarization output of the laser. Compared with light, it is easier to control and is more conducive to experimental control and operational stability.

[0019] 3. The broadband chaotic laser generating device of the present invention can simultaneously generate two chaotic signals with high complexity, no delay, and wide bandwidth, one of which is a chaotic electrical signal output from the collector of the transistor, and the other is a chaotic optical signal output from the base of the transistor. It can be used in high-speed confidential optical communication or random number generation, multi-channel laser radar and other fields.

[0020] In summary, the chaotic signal generated by the broadband chaotic laser generating device of the present invention has a lower delay characteristic. It is not only easy to control and has high stability; moreover, a single device outputs two chaotic signals at the same time, which can be used in high-speed secure optical communication or random number generation, multi-channel laser radar and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic structural diagram of a broadband chaotic laser generating device based on a transistor laser photoelectric feedback structure provided by an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of the interface structure of a transistor laser provided by an embodiment of the present invention;

[0023] In the figure: 1-transistor laser, 2-optical coupler, 3-adjustable optical attenuator, 4-photoelectric converter, 5-electric amplifier, 6-emitter electrode, 7-emitter region material layer, 8-upper confinement layer, 9-quantum well material layer, 10-lower confinement layer, 11-n-type lower cladding layer, 12-p-type lower cladding layer, 13-base electrode layer, 14-base region material layer, 15-base region buffer layer, 16-collector region material layer, 17-collector electrode layer. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Embodiment 1

[0026] like Figure 1 As shown, an embodiment of the present invention provides a broadband chaotic laser generating device based on a transistor laser photoelectric feedback structure, comprising: a transistor laser 1, an optical coupler 2, an adjustable optical attenuator 3, a photoelectric converter 4, and an electric amplifier 5; wherein the laser output end of the transistor laser 1 is connected to the input end of the optical coupler 2, the optical signal output from the first output end of the optical coupler 2 is attenuated by the adjustable optical attenuator 3, and then received by the photoelectric converter 4 and photoelectrically converted, and the electrical signal after photoelectric conversion is amplified by the electric amplifier 5 and sent to the base of the transistor laser 1.

[0027] In addition, in this embodiment, the transistor laser 1 adopts an npn transistor structure.

[0028] Specifically, in this embodiment, the splitting ratio of the second output end of the optical coupler 2 is 10-30%. Specifically, in this embodiment, the splitting ratio of the first output end to the second output end of the optical coupler 2 is 20:80, which divides the light into two paths, with the first port outputting 80% of the light and the second port outputting 20% ​​of the light. The adjustable optical attenuator 3 is used to adjust the light intensity entering the photoelectric converter 4.

[0029] In this embodiment, the transistor laser 1 adopts a common emitter working mode, the emitter electrode is grounded, the base is connected to a current source, the current source is used to provide a driving current for the base of the transistor laser 1, and the collector and the emitter are respectively connected to the two ends of a voltage source, and the voltage source is used to provide a voltage for the collector-emitter of the transistor laser 1.

[0030] The transistor laser 1 starts to work when the base-emitter is forward biased and the base-collector is reverse biased. The electrons injected from the emitter terminal recombine with the holes provided to the base terminal by the base current in the quantum well. Since the concentration of the minority electrons injected into the base is the highest in the emission region, a tilted carrier distribution is formed in the base. Due to the tilted charge distribution, the minority electrons diffuse on the base region. When the electrons diffuse through the active region, the electrons with a recombination lifetime shorter than the transmission time of the base region will radiatively recombine with most of the holes. The carriers with a long recombination time will move to the collector to form a collector current due to the reverse bias at the base-collector junction. By only allowing electrons with a recombination lifetime shorter than the transition time to participate in radiative recombination, the recombination lifetime of the carriers in the base region of the transistor laser is limited to the picosecond range, effectively suppressing the influence of relaxation oscillation, greatly improving the direct modulation bandwidth, and thus obtaining a continuous laser with a high modulation bandwidth and a low relaxation oscillation peak. Therefore, in terms of optical modulation speed performance, transistor lasers are inherently superior to diode lasers.

[0031] In specific implementation, the continuous laser output from the laser output port of the transistor laser 1 passes through the optical coupler 2 and is then divided into two parts by the optical coupler 2. One part of the light is used to output a broadband chaotic laser, and the other part of the light passes through the adjustable optical attenuator 3 and then enters the photoelectric converter 4 to convert the optical signal into an electrical signal, and then enters the electrical amplifier 5 so that the power of the electrical signal can be amplified, and finally injected into the base of the transistor laser 1 together with the bias current provided by the current source, resulting in a change in the carrier density in the quantum well of the transistor laser 1. This causes nonlinear perturbations in the photon number density and the phase of the light field, thereby generating a chaotic laser. At the same time, the collector of the transistor laser 1 can output a chaotic electrical signal. The collector of the transistor laser 1 is connected to an oscilloscope and a spectrum analyzer to monitor the chaotic laser characteristics output by the broadband chaotic laser generating device of the present invention.

[0032] Embodiment 2

[0033] Similar to the first embodiment, the first embodiment of the present invention provides a broadband chaotic laser generating device based on transistor laser photoelectric feedback, including: a transistor laser 1, an optical coupler 2, an adjustable optical attenuator 3, a photoelectric converter 4, and an electric amplifier 5; wherein the laser output end of the transistor laser 1 is connected to the input end of the optical coupler 2, the optical signal output from the first output end of the optical coupler 2 is attenuated by the adjustable optical attenuator 3 and then received by the photoelectric converter 4 and photoelectrically converted, and the photoelectrically converted electrical signal is amplified by the electric amplifier 5 and sent to the base of the transistor laser 1. The transistor laser 1 adopts a common emitter working mode, the emitter electrode is grounded, the base is connected to a current source, the current source is used to provide a driving current for the base of the transistor laser 1, and the collector is connected to a voltage source, the voltage source is used to provide a voltage for the collector-emitter of the transistor laser 1.

[0034] Different from the first embodiment, in this embodiment, Figure 2 As shown, the transistor laser 1 includes a collector electrode layer 17, a collector region material layer 16, a base region buffer layer 15 and a base region material layer 14 which are arranged in sequence from bottom to top, and a ridge waveguide protruding relative to the chip surface is arranged on the base region material layer 14, and the ridge waveguide includes a p-type lower cladding layer 12, an n-type lower cladding layer 11, a lower confinement layer 10, a quantum well material layer 9, an upper confinement layer 8, an emitter region material layer 7 and an emitter electrode layer 6 which are arranged in sequence from bottom to top; a base electrode layer 13 isolated from the ridge waveguide is also arranged on the base region material layer 14.

[0035] Furthermore, in this embodiment, the emitter material layer 7 is n-doped, the base material layer 14 is p-doped, and the collector material layer 16 is n-doped. Therefore, the transistor laser 1 includes an n-type material layer, a p-type material layer, a quantum well layer, and an n-type material layer arranged in sequence from bottom to top. The quantum well layer is arranged above the base region and below the emitter region, which can reduce the contact between the quantum well and the p-type base material compared to the traditional structure, prevent the diffusion of impurity Zn, and reduce the pollution to the quantum well.

[0036] Furthermore, in this embodiment, the p-type lower cladding layer 12 is made of p-doped InAlAs material, and the n-type lower cladding layer 11 is made of n-doped InAlAs material. By adding the n-type lower cladding layer 11 made of n-doped InAlAs material to the ridge waveguide structure of the transistor laser 1, it is helpful to reduce the high energy barrier between the p-type InAlAs lower cladding layer 12 and the p-type InGaAsP14 base material layer in the traditional deep ridge transistor laser, so that more electrons can be diffused into the base region, providing enough electrons for the base region, increasing the collector current, and improving the common emitter current gain.

[0037] Furthermore, in this embodiment, the emitter material layer 7 is made of n-doped InP material; the upper confinement layer 8 is made of InGaAsP material; the quantum well material layer 9 is made of InGaAsP / InP material, and the lower confinement layer 10 is made of InGaAlAs material.

[0038] Furthermore, in this embodiment, the base material layer 14 is made of p-doped InGaAsP material, the base buffer layer 15 is made of InGaAsP material; and the collector material layer 16 is made of n-doped InP material.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A broadband chaotic laser generating device based on a transistor laser photoelectric feedback structure, characterized in that: include: A transistor laser (1), an optical coupler (2), an adjustable optical attenuator (3), a photoelectric converter (4), and an electric amplifier (5); wherein the laser output end of the transistor laser (1) is connected to the input end of the optical coupler (2); the optical signal output from the first output end of the optical coupler (2) is attenuated by the adjustable optical attenuator (3) and then received by the photoelectric converter (4) for photoelectric conversion; the electric signal after photoelectric conversion is amplified by the electric amplifier (5) and then sent to the base of the transistor laser (1); The transistor laser (1) adopts a common emitter working mode, the emitter electrode is grounded, the base is connected to a current source, the current source is used to provide a driving current for the base of the transistor laser (1), and the collector and the emitter are respectively connected to two ends of a voltage source, and the voltage source is used to provide a voltage for the collector-emitter of the transistor laser (1).

2. The broadband chaotic laser generating device based on transistor laser photoelectric feedback structure according to claim 1 is characterized in that: The transistor laser (1) comprises a collector electrode layer (17), a collector region material layer (16), a base region buffer layer (15) and a base region material layer (14) which are arranged in sequence from bottom to top; a ridge waveguide is arranged on the base region material layer (14); the ridge waveguide comprises a p-type lower cladding layer (12), an n-type lower cladding layer (11), a lower confinement layer (10), a quantum well material layer (9), an upper confinement layer (8), an emitter region material layer (7) and an emitter electrode layer (6) which are arranged in sequence from bottom to top; and a base electrode layer (13) which is isolated from the ridge waveguide is also arranged on the base region material layer (14).

3. The broadband chaotic laser generating device based on transistor laser photoelectric feedback structure according to claim 2 is characterized in that: The p-type lower cladding layer (12) is made of p-doped InAlAs material, and the n-type lower cladding layer (11) is made of n-doped InAlAs material.

4. The broadband chaotic laser generating device based on transistor laser photoelectric feedback structure according to claim 2 is characterized in that: The emitter region material layer (7) is n-doped, the base region material layer (14) is p-doped, and the collector region material layer (16) is n-doped.

5. The broadband chaotic laser generating device based on transistor laser current feedback according to claim 2, characterized in that: The emission region material layer (7) is made of n-doped InP material; the upper confinement layer (8) is made of InGaAsP material; the quantum well material layer (9) is made of InGaAsP / InP material; and the lower confinement layer (10) is made of InGaAlAs material.

6. The broadband chaotic laser generating device based on transistor laser current feedback according to claim 2, characterized in that: The base region material layer (14) is made of p-doped InGaAsP material, the base region buffer layer (15) is made of InGaAsP material; and the collector region material layer (16) is made of n-doped InP material.

7. The broadband chaotic laser generating device based on transistor laser current feedback according to claim 1, characterized in that: The splitting ratio of the second output end of the optical coupler (2) is 10-30%.

8. The broadband chaotic laser generating device based on transistor laser optical feedback structure according to claim 1, characterized in that: The collector of the transistor laser (1) is connected to an oscilloscope and a spectrum analyzer to characterize the time sequence and spectrum of the chaotic optical signal.

9. The broadband chaotic laser generating device based on transistor laser optical feedback structure according to claim 1, characterized in that: The transistor laser (1) is an npn-type transistor.

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