A self-similar optical pulse amplification device based on semiconductor quantum dots

Abstract

The present invention provides a self-similar optical pulse amplifier based on semiconductor quantum dots, which belongs to the field of optical fiber communication technology. It includes an optical pulse source, a pump source, an optical coupler, an optical stretcher, a semiconductor quantum dot, an optical compressor, and an output light beam; the output of the optical pulse source and the pump source are connected to the input of the optical coupler, the output of the optical coupler is connected to the input of the optical stretcher, the output of the optical stretcher is connected to the input of the semiconductor quantum dot, the output of the semiconductor quantum dot is connected to the input of the optical compressor, and the output of the optical compressor is a self-similar amplified optical pulse. The present invention has the advantages of being able to improve the energy and quality of optical pulses.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber communication, and relates to a light pulse self-similar amplification device, and in particular to a device for realizing light pulse self-similar amplification by using semiconductor quantum dot waveguide. Background Art

[0002] In recent years, the generation and transmission of high-energy optical pulses with strict linear chirp characteristics has been one of the research hotspots in the field of optical fiber communications. In order to further increase the output single pulse energy, nonlinear spectral broadening can be used in optical fiber amplifiers to achieve compression from picosecond pulses to femtosecond pulses. However, during the nonlinear amplification of optical pulses, the self-phase modulation (SPM) effect will introduce nonlinear chirp that cannot be compressed, which seriously reduces the quality of the output pulses.

[0003] Self-similar amplification of optical pulses can effectively solve the problem of nonlinear chirp in the process of optical pulse amplification, and can obtain high-intensity, high-quality optical pulses. Self-similar amplification of optical pulses is a kind of progressive pulse generated by the nonlinear characteristics of optical fiber. The energy of this pulse can be significantly amplified and has a strong linear chirp. In particular, since the characteristics of self-similar amplification of optical pulses are only related to the initial energy and optical fiber parameters of the incident pulse, but not to the shape of the incident pulse, self-similar amplification of optical pulses can effectively increase the power of the output pulse. In addition, during high-power transmission, self-similar optical pulses also have the ability to resist light wave splitting. Precisely because self-similar optical pulses have the above advantages, self-similar amplification of optical pulses has important application significance and value for the development of optical fiber communications.

[0004] In 2000, the paper (Fermann ME, Kruglov VI, Thomsen BC, et al. Self-Similar Propagation and Amplification of Parabolic Pulses in Optical Fibers [J]. Physical Review Letters, 2000, 84 (26): 6010-6013) gave a detailed explanation and experimental verification of the self-similar amplification theory. They used non-parabolic pulses in Yb-doped 3+ The parabolic pulse output was obtained by amplifying in a positive dispersion gain fiber, and it was demonstrated that the pulse shape would not change during transmission. At the same time, the pulse width and peak power in the time domain would increase with the increase of transmission distance, and the linear chirp that was easily compensated would be accumulated. The Yb-doped self-similar optical pulse achieved an amplification factor of 30 dB. 3+ The gain fiber length is 3.6m.

[0005] In 2007, Papadopoulos DN et al. realized self-similar pulse amplification in large mode field double-clad photonic crystal fiber and obtained near-transformation-limited pulses of 11.5 W, 29 nJ, and 63 fs, but the length of the photonic crystal fiber used was as long as 6.5 m (Papadopoulos DN, Zauter Y, Hanna M, et al. Generation of 63 fs 4.1 MW peak power pulses from a parabolic fiber amplifier operated beyond the gain bandwidth limit [J]. Optics Letters, 2007, 32 (17): 2520-2.).

[0006] In 2018, the research group of Tianjin University established a compact self-similar optical pulse amplification model and finally 3+ Rapid self-similar evolution was achieved in short optical fibers, and near-transformation-limited pulses of 66 fs and an average power of 6.1 W were obtained (Song Huanyu, Liu Bowen, Chen Wei, et al. Femtosecond laser pulse generation with self-similar amplification of picosecond laser pulses[J]. Optics express, 2018, 26(20)).

[0007] In summary, the current devices and technologies for amplifying self-similar optical pulses are Figure 1 As shown, ytterbium-doped fiber is used as a gain medium to implement self-similar amplification of optical pulses. However, in order to provide a sufficiently long evolution distance for self-similar evolution, this optical pulse self-similar amplification system generally requires a longer ytterbium-doped fiber as a gain medium, which, on the one hand, requires more ytterbium-doped fiber materials, increasing production consumables and costs; on the other hand, it makes it easier to produce stimulated Raman effect, thereby limiting the output energy of optical pulse self-similar amplification. Summary of the invention

[0008] The purpose of the present invention is to solve the problem that the existing technology of self-similar amplification of optical pulses requires a longer gain medium, and propose a self-similar optical pulse amplification device based on semiconductor quantum dot waveguide. The nonlinearity generated by quantum dots and the third-order nonlinearity of the gradient semiconductor waveguide cancel each other out, so that the effective fifth-order nonlinear coefficient of the semiconductor waveguide is negative, thereby realizing high-intensity ultrashort pulses in the semiconductor quantum dot waveguide. The technical problem to be solved by the present invention is to achieve a greater self-similar amplification factor of optical pulses with a shorter gain medium length, and further improve the energy and quality of optical pulses.

[0009] The object of the present invention can be achieved by the following technical solutions: A light pulse self-similar amplification device based on semiconductor quantum dots, characterized by comprising: a light pulse source, a pump source, an optical coupler, a light stretcher, semiconductor quantum dots, a light compressor, and an output light beam;

[0010] The outputs of the optical pulse source and the pump source are connected to the input of the optical coupler, the output of the optical coupler is connected to the input of the optical stretcher, the output of the optical stretcher is connected to the input of the semiconductor quantum dot, the output of the semiconductor quantum dot is connected to the input of the optical compressor, and the output of the optical compressor is a self-similar amplified optical pulse;

[0011] The optical pulse source is a signal light source that needs to be amplified, and the pump source provides external energy for the optical amplification system. The two light beams of the optical pulse source and the pump source are coupled into one light beam through the optical coupler and transmitted to the optical pulse self-similar amplification device composed of the optical stretcher, the semiconductor quantum dots, and the optical compressor. The output light beam is the self-similar amplified optical pulse of the optical pulse.

[0012] Furthermore, the semiconductor quantum dots are composed of epoxy resin, semiconductor waveguide, and quantum dots. The epoxy resin is an external package of the semiconductor quantum dots. Light holes are provided at positions corresponding to the input and output light beams. The semiconductor waveguide is composed of ZnSe material, and the quantum dots are composed of CdSe material.

[0013] Furthermore, the semiconductor waveguide is a ZnSe planar semiconductor waveguide with a thickness of 1 mm, and the quantum dots are obtained by doping CdSe quantum dots in the semiconductor waveguide, with a doping concentration of N≈10 14 cm -3 , which can be obtained by molecular beam epitaxy growth method in thermal activation process;

[0014] Furthermore, the wavelength of the optical pulse source is selected to be 500 nm, and the typical value of the dipole matrix element of the quantum dot material CdSe is |d ge |≈10 -28 Transverse γ of Cm, CdSe atomic dipole (reversal)⊥ and the longitudinal attenuation rate γ || The ratio is 2.5 (i.e. γ ⊥ =2.5γ || );

[0015] Furthermore, when the wavelength of the optical pulse source is 500 nm, the refractive index n0 of the ZnSe waveguide is 2.7, and the linear part coefficient n1 of the refractive index of the high-order nonlinear effect is 0.1 cm -2 , the third-order nonlinear coefficient n2 is -7×10 -14 cm 2 / W, effective fifth-order nonlinear coefficient n 4eff -10 -22 cm 4 / W 2 , the frequency detuning amount between the optical pulse frequency and the resonance frequency of the CdSe quantum dots is Δ≈10 13 s -1 ;

[0016] Furthermore, in the device of the present invention, the thickness of the semiconductor waveguide is set to 1 mm, the light pulse is confined in the vertical direction, the lifetime of the CdSe quantum dot is 100 ps, ​​and the lateral decay rate of the CdSe atomic dipole is γ ⊥ ≈10 10 s -1 , thus satisfying the condition Δ>>γ ⊥ ;

[0017] Furthermore, the lateral scale parameter w0 of the ZnSe waveguide is 34 μm, and the diffraction length L D is 3.7 cm. After the light pulse propagates a diffraction length in the semiconductor waveguide, the light pulse amplification factor E satisfies E 2 >>1.

[0018] Preferably, the pulse laser generating the optical pulse source and pump source is a fully positive dispersion mode-locked Yb-doped 3+ Fiber lasers;

[0019] Preferably, the optical stretcher is a blazed grating pair stretcher;

[0020] Preferably, the optical compressor is a blazed grating pair compressor.

[0021] Compared with the current self-similar optical pulse amplification device, the present invention has the following advantages:

[0022] (1) The device proposed in the present invention can achieve rapid amplification of self-similar optical pulses, and the amplification speed is more advantageous than that of traditional semiconductor optical amplifiers. This means that to amplify the optical signal to the same multiple, the quantum dot semiconductor optical amplifier material required for design is much less than that of traditional semiconductor optical amplifiers. This will save a lot of production consumables and costs, and obtain more economic and social benefits.

[0023] (2) The interaction between the optical pulses in the device of the present invention does not significantly affect each other's transmission, and can be used for multi-channel transmission design in optical communications.

[0024] (3) The device proposed in the present invention can realize rapid amplification of optical pulses. The structure is simple. The quantum dot semiconductor optical amplifier can be obtained by molecular beam epitaxial growth technology in the thermal activation process. It can be applied to related fields such as fiber optical soliton communication, semiconductor optical devices and optical amplifiers. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A diagram of an existing optical pulse self-similar amplification device using ytterbium-doped optical fiber as a gain medium;

[0026] Figure 2 This is a diagram of a device for realizing self-similar amplification of optical pulses using semiconductor quantum dot waveguides according to the present invention;

[0027] Figure 3 for Figure 2 A cross-sectional view of the semiconductor quantum dot waveguide 5;

[0028] Figure 4 for Figure 2 A cross-sectional view of a semiconductor quantum dot waveguide 5;

[0029] Figure 5 The output optical pulse waveform obtained by using the device of the present invention, the dotted line is the input optical pulse, the solid line is the Figure 1 The output light pulse waveform measured by the semiconductor quantum dot waveguide 5 has a transmission distance of 18.5 cm.

[0030] In the figure, 1, optical pulse source; 2, pump source; 3, optical coupler; 4, optical stretcher; 5, semiconductor quantum dots; 501, epoxy resin; 502, semiconductor waveguide; 503, quantum dots; 6, optical compressor; 7, output light beam. DETAILED DESCRIPTION

[0031] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0032] like Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown, a light pulse self-similar amplification device based on semiconductor quantum dots is characterized by comprising: a light pulse source 1, a pump source 2, an optical coupler 3, an optical stretcher 4, a semiconductor quantum dot 5, an optical compressor 6, and an output light beam 7;

[0033] The outputs of the optical pulse source 1 and the pump source 2 are connected to the input of the optical coupler 3, the output of the optical coupler 3 is connected to the input of the optical stretcher 4, the output of the optical stretcher 4 is connected to the input of the semiconductor quantum dot 5, the output of the semiconductor quantum dot 5 is connected to the input of the optical compressor 6, and the output light beam 7 of the optical compressor 6 is a self-similar amplified optical pulse;

[0034] The optical pulse source 1 is the signal light source to be amplified, and the pump source 2 provides external energy for the optical amplification system. The two light beams of the optical pulse source 1 and the pump source 2 are coupled into one light beam through the optical coupler 3 and transmitted to the optical pulse self-similar amplification device composed of the optical stretcher 4, the semiconductor quantum dot 5, and the optical compressor 6. The output light beam 7 is the self-similar amplified optical pulse of the optical pulse 1.

[0035] Furthermore, the semiconductor quantum dot 5 is composed of epoxy resin 501, semiconductor waveguide 502, and quantum dot 503. The epoxy resin 501 is an external package of the semiconductor quantum dot 5. Light holes are provided at positions corresponding to the input and output light beams. The semiconductor waveguide 502 is composed of ZnSe material, and the quantum dot 503 is composed of CdSe material.

[0036] The semiconductor waveguide 502 is a ZnSe planar semiconductor waveguide with a thickness of 1 um. The quantum dots 503 are obtained by doping CdSe quantum dots in the semiconductor waveguide 502. The doping concentration is N≈10 14 cm -3 , which can be obtained by molecular beam epitaxy growth method in thermal activation process;

[0037] The wavelength of the optical pulse source 1 is selected to be 500 nm, and the typical value of the dipole matrix element of the quantum dot 503 material CdSe is |d ge |≈10 -28 Transverse γ of Cm, CdSe atomic dipole (reversal) ⊥ and the longitudinal attenuation rate γ || The ratio is 2.5 (i.e. γ ⊥ =2.5γ || );

[0038] When the wavelength of light pulse 1 is 500 nm, the refractive index n0 of the ZnSe waveguide is 2.7, and the linear part coefficient n1 of the refractive index of the high-order nonlinear effect is 0.1 cm -2 , the third-order nonlinear coefficient n2 is -7×10 -14 cm 2 / W, so the effective fifth-order nonlinear coefficient n4eff -10 -22 cm 4 / W 2 , the frequency detuning amount between the optical pulse frequency and the resonance frequency of the CdSe quantum dots is Δ≈10 13 s -1 .

[0039] In the device of the present invention, the thickness of the semiconductor waveguide 502 is set to 1 μm, the light pulse 1 is confined in the vertical direction, the lifetime of the CdSe quantum dot is 100 ps, ​​and the lateral decay rate of the CdSe atomic dipole is γ ⊥ ≈10 10 s -1 , thus satisfying the condition Δ>>γ ⊥ ;

[0040] The lateral scale parameter w0 of the ZnSe waveguide is 34 μm, and the diffraction length L D is 3.7 cm. After the light pulse 1 propagates a diffraction length in the semiconductor waveguide 502, the light pulse amplification factor E satisfies E 2 >>1.

[0041] Preferably, the pulse lasers generating the optical pulse source 1 and the pump source 2 are all positive dispersion mode-locked Yb-doped 3+ Fiber lasers;

[0042] Preferably, the light stretcher 4 is a blazed grating pair stretcher;

[0043] Preferably, the optical compressor 6 is a blazed grating pair compressor.

[0044] Figure 5 The output light pulse waveform and the input light pulse waveform obtained by using the device of the present invention are shown in FIG. 1 , wherein the dotted line is the normalized input light pulse and the solid line is the Figure 1 The output light pulse waveform measured by the semiconductor quantum dot waveguide 5 shows a transmission distance of 18.5 cm. Figure 5 It can be seen that the gain medium length is only 18.5 cm, the amplitude of the light pulse is amplified 5.5 times, and the power of the light pulse is amplified 70 times. It can be seen that the device proposed by the present invention can achieve the purpose of self-similar amplification of light pulses with a shorter gain medium length.

[0045] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A light pulse self-similar amplification device based on semiconductor quantum dots, characterized in that: It comprises an optical pulse source (1), a pump source (2), an optical coupler (3), an optical stretcher (4), a semiconductor quantum dot (5), an optical compressor (6), and an output light beam (7); The outputs of the optical pulse source (1) and the pump source (2) are connected to the input of the optical coupler (3), the output of the optical coupler (3) is connected to the input of the optical stretcher (4), the output of the optical stretcher (4) is connected to the input of the semiconductor quantum dot (5), the output of the semiconductor quantum dot (5) is connected to the input of the optical compressor (6), and the output of the optical compressor (6) is a self-similar amplified optical pulse; The optical pulse source (1) is a signal light source to be amplified, the pump source (2) provides external energy for the optical pulse self-similar amplifier, the two light beams of the optical pulse source (1) and the pump source (2) are coupled into one light beam through the optical coupler (3) and transmitted to the optical pulse self-similar amplifier composed of the optical stretcher (4), the semiconductor quantum dot (5) and the optical compressor (6), and the output light beam (7) is the self-similar amplified optical pulse of the optical pulse; The semiconductor quantum dots (5) are composed of an epoxy resin (501), a semiconductor waveguide (502), and a quantum dot (503); the epoxy resin (501) is an external package for the semiconductor quantum dots (5); light holes are provided at positions corresponding to the input and output light beams (7); the semiconductor waveguide (502) is composed of a ZnSe material; and the quantum dots (503) are composed of a CdSe material; The semiconductor waveguide (502) is a ZnSe planar semiconductor waveguide (502) with a thickness of 1 um, and the quantum dots (503) are obtained by doping CdSe quantum dots (503) in the semiconductor waveguide (502), with a doping concentration of N≈10 14 cm -3 , which can be obtained by molecular beam epitaxy growth method in thermal activation process; The wavelength of the optical pulse source (1) is selected to be 500 nm, and the typical value of the CdSe dipole matrix element of the quantum dot (503) material is |d ge |≈10 -28 The lateral decay rate of Cm, CdSe atomic dipole γ ⊥ and the longitudinal attenuation rate γ || The ratio is 2.

5.

2. According to claim 1, a semiconductor quantum dot-based optical pulse self-similar amplification device is characterized in that: When the wavelength of the optical pulse source (1) is 500 nm, the refractive index n0 of the semiconductor waveguide (502) is 2.7, and the linear part coefficient n1 of the refractive index of the high-order nonlinear effect is 0.1 cm -2 , the third-order nonlinear coefficient n2 is -7×10 -14 cm 2 / W, so the effective fifth-order nonlinear coefficient n 4eff For 10 -22 cm 4 / W 2 The frequency detuning amount between the optical pulse frequency and the resonance frequency of the CdSe quantum dot (503) is Δ≈10 13 s -1 .

3. According to claim 2, a semiconductor quantum dot-based optical pulse self-similar amplification device is characterized in that: The thickness of the semiconductor waveguide (502) is set to 1 μm, the light pulse is confined in the vertical direction, the lifetime of the CdSe quantum dot (503) is 100 ps, ​​and the lateral decay rate of the CdSe atomic dipole is γ ⊥ ≈10 10 s -1 , thus satisfying the condition Δ>>γ ⊥ .

4. The optical pulse self-similar amplification device based on semiconductor quantum dots according to claim 1, characterized in that: The lateral scale parameter w0 of the semiconductor waveguide (502) is 34 um, and the diffraction length L D is 3.7 cm, and after the light pulse propagates a diffraction length in the semiconductor waveguide (502), the light pulse amplification factor E satisfies E 2 >>1.

5. The optical pulse self-similar amplification device based on semiconductor quantum dots according to claim 1, characterized in that: The pulse lasers that generate the optical pulse source (1) and the pump source (2) are all positive dispersion mode-locked Yb-doped 3+ Fiber laser.

6. The optical pulse self-similar amplification device based on semiconductor quantum dots according to claim 1, characterized in that: The light stretcher (4) is a blazed grating pair stretcher.

7. The optical pulse self-similar amplification device based on semiconductor quantum dots according to claim 1, characterized in that: The optical compressor (6) is a blazed grating pair compressor.

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