Broadband chaotic laser generation device based on optical feedback structure of transistor laser

Abstract

The application relates to the field of semiconductor optoelectronics and discloses a wideband chaotic laser generation device based on a transistor laser optical feedback structure, which comprises a transistor laser, an optical circulator, an optical fiber coupler, an attenuation controller and a polarization controller. The transistor laser comprises an emitter electrode, an emitter region material layer, an upper confinement layer, a quantum well material layer, a current confinement layer, a base electrode, a base region material layer, a base region buffer layer, a collector region material layer and a collector electrode. The application overcomes the problem of narrow chaotic laser spectrum bandwidth generated by the existing diode laser optical feedback structure, adopts a transistor laser with a three-port structure to replace a diode laser to generate chaotic laser, and has the advantages of simple structure, high stability and low cost. The application is suitable for the fields of chaotic synchronization and secure optical communication, high-speed random number key generation, laser radar, fiber network fault detection, ultra-wideband technology and distributed fiber sensing.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor optoelectronics, and particularly to a chaotic laser generation device based on a transistor laser optical feedback structure. BACKGROUND

[0002] Chaotic laser has the characteristics of inherent randomness, initial value sensitivity, low coherence, wide spectrum, etc. In recent years, chaotic laser has important application value in the fields of secure optical communication, ultra-wideband technology, laser radar, optical fiber network fault detection, distributed optical fiber sensing, etc. At present, the methods of generating chaos by semiconductor lasers include optical feedback, optical injection and optoelectronic feedback.

[0003] Diode structure semiconductor lasers have become the preferred light source for generating chaotic laser due to their low power consumption, long service life and easy integration. However, the relaxation oscillation frequency of diode lasers is only several GHz, and the energy is mainly concentrated near the relaxation oscillation frequency, resulting in narrow bandwidth and uneven spectrum of the generated chaotic laser, which greatly limits the practical application of chaotic laser (IEEE Journal on Selected Topics in Quantum Electronics, 21(6):531-540, 2015).

[0004] In view of the above problems, researchers have proposed various methods for improving the bandwidth of chaotic laser, in 2003, Uchida et al. of the University of Tsukuba injected chaotic laser generated by external optical feedback into another semiconductor laser, at this time, the bandwidth of chaotic laser generated by the semiconductor laser with a relaxation oscillation frequency of only 6.4 GHz is increased to 22 GHz (Optics Express, 2010, 18(6): 5512-24); in 2008, Wang Anbang et al. of Taiyuan University of Technology proposed injecting continuous light into a semiconductor laser with external cavity optical feedback, and by controlling the frequency detuning and optical injection intensity, the bandwidth of chaotic signal is increased from 6.2 GHz to 16.8 GHz (IEEE Photonics Technology Letters, 2008, 20(19): 1633-1635); in 2011, Zhang Mingjiang et al. obtained broadband chaotic laser with a bandwidth of 32.3 GHz by 80% through double-wavelength external optical injection of an external cavity optical feedback Fabry-Pérot laser (IEEE Photonics Technology Letters, 2011, 23(24): 1872-1874), but the above schemes need a photodetector to realize the detection of the timing and spectrum of the chaotic signal, but the photodetector is easy to be damaged by electrostatic breakdown, thereby greatly affecting the stability and cost of the chaotic laser generation device; and the above schemes are based on diode lasers, and the chaotic laser bandwidth and flatness are improved by means of a complex perturbation system, and the spectral bandwidth is limited.

[0005] A transistor laser is a transistor that has both the current control function of a transistor and the light emission function of a laser. The transistor laser can simultaneously obtain an electrical signal output (collector current) and an optical signal output by using an electrical signal input (e.g., base current). Based on this functional characteristic, the transistor laser has important potential application value in the fields of optical communication and optical signal processing. SUMMARY

[0006] The present application overcomes the problem of narrow chaotic laser spectrum bandwidth based on the existing diode laser optical feedback structure, and provides a chaotic laser generation device based on a transistor laser optical feedback structure. The transistor laser has high bandwidth and low relaxation oscillation peak, and is used to generate broadband chaotic laser signals with wide bandwidth and good flatness.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a broadband chaotic laser generation device based on a transistor laser optical feedback structure, comprising: a transistor laser, an optical circulator, a beam splitter, an attenuation controller, and a polarization controller.

[0008] The laser output end of the transistor laser is connected with the first port of the optical circulator, the second port of the optical circulator is connected with the output end of the optical splitter, the optical splitter divides the light beam into two paths, one path is used for outputting chaotic laser, the other path is connected with the input end of the attenuation controller, the output end of the attenuation controller is connected with the input end of the polarization controller, and the output end of the polarization controller is connected with the third port of the optical circulator.

[0009] The transistor laser adopts a common emitter working mode, the emitter electrode is grounded, the base electrode is connected with a current source as the driving current of the transistor laser, and the collector electrode is connected with a voltage source as the collector-emitter voltage source.

[0010] The transistor laser comprises a collector electrode layer, a collector region material layer, a base region buffer layer and a base region material layer arranged in sequence, a base electrode layer and a current limiting layer which are not connected are arranged on the side of the base region material layer away from the base region buffer layer, and a quantum well material layer, an upper limiting layer, an emission region material layer and an emitter electrode layer are arranged in sequence on the current limiting layer.

[0011] The emission region material layer adopts n-doped InP material, the upper limiting layer adopts InGaAsP material, the quantum well material layer adopts InGaAsP / InP material, the current limiting layer adopts n-doped InP and p-doped InP material to form a pn junction, the base region material layer adopts p-doped InGaAsP material, the base region buffer layer adopts InGaAsP material, and the collector region material layer adopts n-doped InP material.

[0012] The current limiting layer is arranged in two regions, and the base electrode layer is arranged on both sides of the current limiting layer.

[0013] The optical splitter is a 1*2 optical fiber coupler.

[0014] The polarization controller is used for controlling the polarization state of the light.

[0015] The collector current output end of the transistor laser is connected with an oscilloscope and a spectrum analyzer, and is used for outputting the time sequence and spectrum of the chaotic light signal.

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

[0017] 1. The transistor laser with a three-port structure is used to replace the diode laser to generate chaotic laser, and the limitation of internal relaxation oscillation of the laser is broken.

[0018] 2. Through theoretical derivation verification, the present application can generate broadband chaotic laser with a bandwidth of more than 50GHz and a flatness of less than 3.5dB, which is difficult to achieve by using a traditional method.

[0019] 3、The application utilizes the collector current output of the transistor laser itself to monitor the timing and spectrum of the chaotic light signal output by the device, without the need for an external photodetector, effectively reducing the complexity of the structure of the device.

[0020] 4、The application adopts a transistor laser with a three-port structure, overcoming the problem of narrow spectrum bandwidth of chaotic laser generated by existing structures based on optical feedback of a diode laser, and has the advantages of simple structure, high stability and low cost, and has good popularization and application value, and is suitable for fields of chaotic synchronization and secure optical communication, high-speed random number key generation, laser radar, optical fiber network fault detection, ultra-wideband technology and distributed optical fiber sensing. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A structure schematic diagram of a wideband chaotic laser generation device based on a transistor laser optical feedback structure is provided for the embodiment of the application;

[0022] In the figure: 1-transistor laser, 2-optical circulator, 3-optical splitter, 4-attenuator, 5-polarization controller.

[0023] Figure 2 An interface structure schematic diagram of a transistor laser is provided for the embodiment of the application;

[0024] Figure 3 A top view of Figure 2 , in which the emitter electrode, the emitter region material layer, the upper confinement layer and the quantum well material layer above the base electrode layer are removed;

[0025] Figure 4 A carrier distribution schematic diagram in the transistor laser in the embodiment of the application.

[0026] In the figure: 6-emitter electrode, 7-emitter region material layer, 8-upper confinement layer, 9-quantum well material layer, 10-current confinement layer, 11-base electrode layer, 12-base region material layer, 13-base region buffer layer, 14-collector region material layer, 15-collector electrode. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiment of the application more clear, the technical scheme in the embodiment of the application will be clearly and completely described below. Obviously, the described embodiment is a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0028] Embodiment one

[0029] AsFigure 1 As shown in the figure, the embodiment one of the present application provides a wideband chaotic laser generating device based on a transistor laser light feedback structure, comprising: a transistor laser 1, an optical circulator 2, a beam splitter 3, an attenuation controller 4, a polarization controller 5; wherein the laser output end of the transistor laser 1 is connected with the first port of the optical circulator 2, the second port of the optical circulator 2 is connected with the output end of the beam splitter 3; the beam splitter 3 divides the light beam into two paths, one path is used for outputting chaotic laser, and the other path is connected with the input end of the attenuation controller 4, the output end of the attenuation controller 4 is connected with the input end of the polarization controller 5, and the output end of the polarization controller 5 is connected with the third port of the optical circulator 2.

[0030] In addition, in the embodiment, the transistor laser 1 adopts npn transistor structure.

[0031] The transistor laser 1 adopts common emitter working mode, the emitter electrode is grounded, the base electrode is connected with a current source as the driving current of the transistor laser, and the collector electrode is connected with a voltage source as the collector-emitter voltage source, the current source and the voltage source can control the line width broadening factor, the base region carrier spontaneous radiation lifetime and other internal parameters of the transistor laser. When the collector junction of the transistor laser is reverse biased, the minority carriers in the base region are distributed in a tilt, as shown in the figure, wherein, E Figure 4 c : conduction band; E v : valence band; I E : emitter current; I C : collector current; I B ​: base current; e: electron; h: hole; hv: photon; QW: quantum well; n-Emitter: n-doped emitter region; p-Base: p-doped base region; n-Collector: n-doped collector region. Part of the minority carriers are trapped by the quantum well material layer and recombine by stimulated emission in the quantum well material layer, and continuous laser light is emitted at the laser output end. The remaining minority carriers reach the base-collector boundary and diffuse due to the difference in doping between the base and collector materials, forming a diffusion current, i.e. the collector current output by the transistor laser collector. The optical signal is generated by the stimulated emission of the minority carriers in the base region. The collector current and the output laser signal are both derived from the dynamic changes of the minority carriers in the base region, so their trends on the oscilloscope and spectrum analyzer are basically the same, and the collector current can be used to reflect and monitor the timing and spectrum of the chaotic optical signal and monitor its working state. Because the generation of chaotic laser and the generation of collector current are essentially related to the distribution of minority carriers in the base region, the collector current of the transistor laser can reflect the output characteristics of the chaotic laser of the transistor laser, so the chaotic electrical signal at the collector current output end can be used to monitor the output characteristics of the chaotic laser output by the chaotic laser generation device of the embodiment. Due to the tilted distribution of the minority carriers in the base region, the spontaneous emission recombination lifetime of the base region is only ps, which is much smaller than the spontaneous emission recombination lifetime of the traditional diode laser ns, which can effectively suppress the influence of relaxation oscillation and greatly improve the direct modulation bandwidth, thereby obtaining continuous laser with high modulation bandwidth and low relaxation oscillation peak.

[0032] In specific implementation, the optical splitter 3 can be a 1x2 fiber coupler, and the continuous laser output by the transistor laser 1 enters the 1x2 fiber coupler through the optical circulator 2; the 1x2 fiber coupler divides the light beam into two paths, one of which is used to output chaotic laser, and the other of which enters the attenuation controller 4, which is used to precisely control the feedback intensity, so that the frequency spectrum of the output chaotic laser is further broadened, and then enters the polarization controller 5, which is used to control the polarization state, and finally returns to the transistor laser 1 through the optical circulator 2 to form an optical feedback loop. The continuous laser output by the transistor laser 1 circulates and oscillates in the fiber loop, and finally produces broadband chaotic laser. At the same time, the chaotic electrical signal output by the collector current output end of the transistor laser 1 is connected to an oscilloscope and a spectrum analyzer for monitoring the output characteristics of the chaotic laser of the device.

[0033] Embodiment two

[0034] The embodiment two of the present application provides a wideband chaotic laser generating device based on a transistor laser light feedback structure. The same as the embodiment one, it comprises: a transistor laser 1, an optical circulator 2, a beam splitter 3, an attenuation controller 4, a polarization controller 5; wherein the laser output end of the transistor laser 1 is connected with the first port of the optical circulator 2, the second port of the optical circulator 2 is connected with the output end of the beam splitter 3; the beam splitter 3 divides the light beam into two paths, one path is used for outputting chaotic laser, the other path is connected with the input end of the attenuation controller 4, the output end of the attenuation controller 4 is connected with the input end of the polarization controller 5, and the output end of the polarization controller 5 is connected with the third port of the optical circulator 2; the transistor laser 1 adopts a common emitter operating mode, the emitter electrode is grounded, the base electrode is connected with a current source as the driving current of the transistor laser, and the collector electrode is connected with a voltage source as the collector-emitter voltage source.

[0035] Different from the embodiment one, in the embodiment, the transistor laser 1 comprises a collector electrode layer 15, a collector region material layer 14, a base region buffer layer 13 and a base region material layer 12 which are sequentially arranged, a base electrode layer 11 and a current limiting layer 10 which are not connected and are arranged on one side of the base region material layer 12 away from the base region buffer layer 13, and a quantum well material layer 9, an upper limiting layer 8, an emission region material layer 7 and an emitter electrode layer 6 which are sequentially arranged on the current limiting layer 10.

[0036] Specifically, the emission region material layer 7 adopts n-doped InP material; the upper limiting layer 8 adopts InGaAsP material; the quantum well material layer 9 adopts InGaAsP / InP material; the current limiting layer 10 adopts n-doped InP and p-doped InP material to form a pn junction; the base region material layer 12 adopts p-doped InGaAsP material; the base region buffer layer 13 adopts InGaAsP material; and the collector region material layer 14 adopts n-doped InP material.

[0037] Among them, the emission region material layer is n-doped, the base region material layer is p-doped, and the collector region material layer is n-doped, so it comprises n-type material layer, p-type material layer, quantum well layer and n-type material layer which are sequentially arranged from bottom to top. The quantum well layer is arranged above the p-type material layer, which can reduce the pollution of P-doping to the quantum well layer, compared with the structure that the quantum well layer is arranged in the middle of the p-type material layer in the prior art.

[0038] Specifically, in the embodiment, the quantum well material layer 9, the upper limiting layer 8, the emission region material layer 7 and the emitter electrode layer 6 are raised relative to the chip surface to form a ridge waveguide, and the base electrode layer 11 is arranged outside the current limiting layer 10. The current limiting layer 10 functions to make the carriers injected from the emitter pass through only from the current limiting channel, thereby reducing the influence of the surface non-radiative recombination center, so in the embodiment, one current limiting layer 10 is arranged on each side of the ridge waveguide, as shown in the figure.Figures 2-3 In addition, as shown, the two base electrode layers 11 can also be annularly arranged outside the current limiting layer 10 and connected together.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A wideband chaotic laser generation apparatus based on optical feedback structure of a transistor laser, characterized in that, The application relates to a transistor laser (1), an optical circulator (2), a beam splitter (3), an attenuation controller (4) and a polarization controller (5). The laser output end of the transistor laser (1) is connected with the first port of the optical circulator (2), the second port of the optical circulator (2) is connected with the output end of the beam splitter (3), the beam splitter (3) divides the light beam into two paths, one path is used for outputting chaotic laser, the other path is connected with the input end of the attenuation controller (4), the output end of the attenuation controller (4) is connected with the input end of the polarization controller (5), and the output end of the polarization controller (5) is connected with the third port of the optical circulator (2). The transistor laser (1) adopts a common-emitter working mode, the emitter electrode is grounded, a current source is connected with the base electrode as a driving current of the transistor laser, and a voltage source is connected with the collector electrode as a collector-emitter voltage source; a base buffer layer (13) is arranged between the collector region material layer (14) and the base region material layer (12) of the transistor laser (1). The collector current output end of the transistor laser (1) is used for outputting chaotic electrical signals to monitor the output characteristics of the chaotic laser, including time sequence and spectrum. The transistor laser (1) comprises, in sequence, a collector electrode layer (15), a collector region material layer (14), a base buffer layer (13) and a base region material layer (12), a base electrode layer (11) and a current limiting layer (10) which are not connected are arranged on the side of the base region material layer (12) away from the base buffer layer (13), and a quantum well material layer (9), an upper limiting layer (8), an emission region material layer (7) and an emitter electrode layer (6) are sequentially arranged on the current limiting layer (10).

2. The wideband chaotic laser generation apparatus based on a transistor laser optical feedback structure according to claim 1, characterized in that, The emission region material layer (7) adopts n-doped InP material; the upper limiting layer (8) adopts InGaAsP material; the quantum well material layer (9) adopts InGaAsP / InP material; the current limiting layer (10) adopts n-doped InP and p-doped InP material to form a pn junction; the base region material layer (12) adopts p-doped InGaAsP material; the base buffer layer (13) adopts InGaAsP material; and the collector region material layer (14) adopts n-doped InP material.

3. The wideband chaotic laser generation apparatus based on a transistor laser optical feedback structure according to claim 2, characterized in that, The current limiting layer is arranged in two regions, and the base electrode layer (11) is arranged on the two sides of the current limiting layer (10).

4. The wideband chaotic laser generation apparatus based on the optical feedback structure of transistor laser according to claim 2, characterized in that, The beam splitter (3) is a 1*2 optical fiber coupler.

5. The wideband chaotic laser generation apparatus based on a transistor laser optical feedback structure according to claim 1, characterized in that, The polarization controller (5) is used for controlling the polarization state of light.

6. The wideband chaotic laser generation apparatus based on a transistor laser optical feedback structure according to claim 1, characterized in that, The collector current output end of the transistor laser (1) is connected with an oscilloscope and a spectrum analyzer, and is used for outputting the time sequence and spectrum of the chaotic light signal.

7. The wideband chaotic laser generation apparatus based on a transistor laser optical feedback structure according to claim 1, characterized in that, ​

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