Multi-parameter SCH-QW semiconductor laser circuit model and construction method thereof

Abstract

The invention discloses a multi-parameter SCH-QW semiconductor laser circuit model. The circuit model comprises an intrinsic network equivalent circuit part and a packaging parasitic network circuit part; the intrinsic network equivalent circuit part comprises an SCH region, a Gateway region, a quantum well (QW) region and a stimulated radiation region; the SCH region exchanges current carriers with the Gateway region in a bipolar diffusion and current carrier release manner; the quantum well QW region has a quantum well structure, and exchanges carriers through capture and thermal excitation; the Gateway region is used as a portal of carrier exchange of the SCH region and the QW region; the packaging parasitic network circuit part comprises a gold wire, a lumped part and a substrate; the gold wire comprises an inductor LB, a resistor RB and a capacitor CB, the lumped part comprises a lumped capacitor CS and a lumped resistor RS, and the substrate comprises a substrate resistor RSUB. The invention further discloses a construction method of the circuit model and application of the circuit model in simulation of influences of saturation nonlinear effect parameters and ABC coefficients on model output.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor lasers, and in particular relates to a multi-parameter SCH-QW semiconductor laser circuit model and a construction method thereof. Background Art

[0002] Among many light source devices, laser light source has significant advantages. It not only has the advantages of pure monochromatic light, strong coherence, and high brightness, but also with the development and maturity of laser technology, the price of laser light source has gradually decreased. Therefore, it is widely used in industry, agriculture, communications, medical treatment, scientific research, national defense and other fields. The birth and development of laser technology has ignited a great change in the field of optics, promoted the rapid development of information technology, and ushered in the era of high-speed optical communication. Among the various types of lasers, semiconductor lasers with small size and direct electrical modulation are widely used in high-speed and long-distance optical fiber communication systems, and as an important component of optoelectronic integrated circuits (emitting light source).

[0003] As we all know, in order to improve the transmission quality and transmission speed of optical fiber communication systems, each part of the optical communication system must be able to complete high-quality, high-speed information transmission and have excellent performance such as high-speed modulation. The core components in optical fiber communication systems include: semiconductor lasers, optical amplifiers, optical detectors, and optical modulators. The quality of the working characteristics of these devices directly affects the improvement of system performance. Therefore, research on high-performance core transceiver components that can be applied to high-speed optical communication systems has become a hot topic today.

[0004] Modeling and simulating lasers is to meet the needs of OEIC design and production. Since optoelectronic integrated circuits are highly integrated circuits, they cannot be modified after design and manufacturing. Therefore, in order to pre-check whether the designed integrated optical circuit meets the requirements and the performance before processing into products, it is necessary to model and simulate the optoelectronic integrated circuits in advance. This method can greatly reduce the loss of bad chips and save costs. Therefore, optoelectronic integrated circuit computer-aided design (OEIC CAD) plays an important role in shortening the circuit design cycle, reducing resource consumption, improving device performance, and accelerating the development process. The core issue is to establish an equivalent circuit model of optoelectronic devices that can fully and comprehensively reflect the performance of optoelectronic devices and can be described by pure electronic components. Semiconductor lasers are an important part of optical transmitters in optical communication systems. It is critical to establish a model that can accurately describe their performance. Although various characteristics of lasers can be directly obtained by numerical analysis, its disadvantage is that it cannot be analyzed when parasitic elements and driving circuits are included. The establishment of an equivalent circuit model of semiconductor lasers can effectively solve this problem.

[0005] On this premise and basis, for quantum well semiconductor lasers, we consider in detail the internal and external characteristics of the well, the packaging characteristics and the gain nonlinear characteristics, and construct an equivalent circuit model that fits reality and can fully reflect the output characteristics of the laser. This model not only meets the technical requirements of today's era of rapid communications, but also combines the model to study the influence of key parameters in the laser, including intrinsic parameters and parasitic parameters, on the response characteristics of the laser. It is also an important way to optimize the design of semiconductor lasers. Summary of the invention

[0006] In order to solve the deficiencies of the above-mentioned technologies, the present invention proposes a multi-parameter SCH-QW (Separately Confined Quantum Well) semiconductor laser circuit model and a construction method thereof, wherein the circuit model includes an intrinsic network equivalent circuit part and a package parasitic network circuit part.

[0007] The present invention constructs a multi-parameter SCH-QW semiconductor laser circuit model based on quantum well effect, packaging characteristics and gain nonlinear characteristics;

[0008] The quantum well effect refers to the fact that the quantum theory characteristics of carriers begin to appear because the thickness of the active area of ​​the laser is close to the electron wavelength, which is manifested as electrons being confined in the quantum well in the x-axis direction, but unrestricted in the yz plane, so this structure is also called a quantum well structure. The effect exhibited by the quantum well structure is called the quantum well effect, including a significant reduction in the threshold current required for the quantum well to achieve population inversion (i.e., to achieve laser radiation), a narrower gain curve and line width, and easier realization of short-wavelength lasing.

[0009] The packaging characteristics refer to the fact that the laser chip will be connected to the carrier by adding gold wires during the packaging process. Therefore, it is necessary to introduce packaging parasitic parameters, including series metal wire resistance, series gold wire inductance, parallel gold wire capacitance, lumped capacitance, lumped resistance and substrate resistance.

[0010] The gain nonlinearity refers to the fact that due to the quantum size effect in the quantum well laser, the state density takes a certain value, the increase in carrier concentration will approach complete distribution inversion, the increase in gain shows a saturation tendency, and eventually tends to the saturation value.

[0011] The present invention proposes a method for constructing a multi-parameter SCH-QW semiconductor laser circuit model, which is used to construct an intrinsic network equivalent circuit and a package parasitic network circuit; wherein:

[0012] The equivalent circuit of the intrinsic network is constructed based on the three-level rate equation of the semiconductor laser:

[0013] The three-level rate equation is universal in the equivalent circuit model, and can be used for the analysis of small signals and large signals. Taking the dynamic transport process of carriers and photons in the InGaAs-AlGaAs single quantum laser as an example, Figure 7 As shown, according to the differential equations describing the dynamic process, the carrier concentration rate equations for the three regions (including the SCH region, the Gateway region, and the quantum well QW region) and a photon concentration rate equation are obtained, that is, the three-level rate equation [1-3] :

[0014] The carrier concentration rate equation in the SCH region is:

[0015]

[0016] The carrier concentration rate equation in the Gateway region is:

[0017]

[0018] The carrier concentration rate equation in the quantum well region is:

[0019]

[0020] Photon concentration rate equation:

[0021]

[0022] The SCH region refers to a separation and confinement heterojunction region, which exchanges carriers with the Gateway region by means of bipolar diffusion and carrier release;

[0023] The Gateway region is a portal for the SCH region and the QW region to exchange carriers, and therefore is also called a channel state;

[0024] The quantum well QW region refers to a region having a quantum well structure that can capture and thermally excite carriers for exchange.

[0025] In the above formulas, n i (t) is the contribution of external injection to SCH carriers; n S 、n G and n Q Respectively represent the carrier concentrations in the SCH region, Gateway region, and QW region; S is the photon density; Γ is the light confinement factor, which represents the ratio of the optical power propagating in the active layer; υ g is the group velocity; ε S is the gain compression factor related to photon density, which describes that the gain is compressed as the photon density increases; τ P is the photon lifetime, which is related to the intracavity loss; τ Dis the transport time constant, which is used to describe the process of carrier diffusion from SCH to Gateway through the bipolar; τ G is the lifetime of carriers in the channel state; τ C is the bipolar capture time constant, which is used to describe the process of carrier transfer from Gateway to QW; τ nS is the carrier lifetime in the SCH region; τ ESC is the carrier escape time; τ nG is the carrier lifetime in the Gateway region; τ nQ is the carrier lifetime in the QW region; β is the spontaneous radiation coupling factor, which indicates the ratio of spontaneous radiation coupling of carriers into the lasing mode; g(n Q ) is the carrier-related material gain.

[0026] According to the theory of saturation nonlinear effect in the well and carrier lifetime dynamic characteristics, the present invention improves the above equation and converts it into the intrinsic network equivalent circuit, such as Figure 1 shown.

[0027] Figure 1 In the figure, the junction capacitance represented by CJ and CP is approximately the parallel plate capacitance composed of the cladding and the active region; E1, E2, and E3 provide current I for C1, C2, and C3 respectively. nS ,I nG ,I AQ voltage source; VIS, VIG, VIQ, VI1, VI2, and VI3 are independent voltage sources with a power supply of 0V and are used as ammeters. This allows the current of a branch to be directly referenced, which is convenient for the expression of the later model; in order to avoid the problem of floating nodes in the simulation, I nS ,I nG ,I AQ Use diode elements to equalize, and the remaining current terms are equivalent to voltage-controlled current sources, that is, I VI1 ,I VI2 ,I VI3 It is the current source of the current value recorded by VI1, VI2, and VI3, and is used to represent other branch currents later. nS ,I nG ,I AQ ,I D ,I G ,I C ,I ESC ,I STIM ,I SPON represents the voltage-controlled current source related to the carrier concentration, RP represents the resistance; I BQ ,I CQ represents a voltage-controlled current source associated with spontaneous radiative recombination and a voltage-controlled current source associated with Auger recombination.

[0028] The in-well saturation nonlinear effect refers to the quantum size effect in the quantum well laser. When the state density takes a certain value, the increase of carrier concentration will approach the complete distribution inversion, and the increase of gain will show a saturation tendency and eventually tend to a saturation value, rather than a linear representation.

[0029] The carrier lifetime dynamic characteristics theory means that due to the violent fluctuation of carriers in the quantum well region of the semiconductor laser, the carrier lifetime is not a constant, but a function related to the carrier concentration, which is expressed as the ABC coefficient expression of the carrier lifetime: 1 / τ nQ (n Q )≈A+Bn Q +Cn Q 2 , where A is the Shockley-Read-Hall (SRH) recombination coefficient, B is the spontaneous emission coefficient, and C is the Auger recombination coefficient [4] .

[0030] According to the saturation nonlinear effect existing in quantum well laser, the present invention calculates g(n Q ) has been improved. Before the improvement, it was g(n Q )=g0(n Q -n0), the improved present invention adds the saturation gain coefficient g in the equation s , so that the gain is expressed from linear to nonlinear, which is closer to reality. The saturation gain coefficient g is increased s The improved g(n Q )The expression of nonlinear expression is:

[0031]

[0032] Where g0 is the differential gain, also known as the gain slope; n0 is the transparent carrier concentration. When the injected carrier concentration exceeds this value, the population inversion is achieved. s It is the optical gain coefficient when the laser is in the saturation state, which is determined by multiple factors such as the band structure, state density, and distribution function.

[0033] According to the carrier lifetime dynamic characteristic theory, the present invention adds a carrier ABC recombination mechanism to the intrinsic network equivalent circuit model.

[0034] The carrier ABC recombination mechanism refers to the use of the ABC model of the dependence of different recombination processes on carrier concentration to replace the carrier recombination rate described by the average carrier lifetime. The carrier recombination mechanism described by the ABC model includes three processes: Shockley-Read-Hall (SRH) recombination, radiative recombination and Auger recombination. That is, the average carrier lifetime 1 / τnQ (n Q )≈A+Bn Q +Cn Q 2 , where A is the Shockley-Read-Hall (SRH) recombination coefficient, B is the spontaneous emission coefficient, and C is the Auger recombination coefficient.

[0035] The influence of the ABC recombination mechanism in the model is reflected in the rate equation (3) for the carrier concentration in the quantum well region, where the average carrier lifetime τ nQ is replaced by the more accurate ABC model and is replaced by I in the equivalent circuit equation (11). AQ ,I BQ ,I CQ to represent the impact of three different compound mechanisms in the ABC model.

[0036] The improved three-level rate equation of the semiconductor laser of the present invention can be converted into the circuit equation shown below:

[0037] The third-order rate equation (1-4) is a rate equation related to concentration. In the equivalent circuit model, it needs to be converted into a rate equation with electrical related parameters. By introducing Q=nqV, where Q is the charge, q is the charge per unit electron, n is the carrier concentration, and V is the volume of the quantum well region, both ends of the rate equation are multiplied by qV. In this way, the relationship between dn / dt and n / t can be converted into dQ / dt and Q / t, which is related to current and converted into a charge equation (5-8).

[0038]

[0039]

[0040]

[0041]

[0042] In the formula, I i is the current injected from the n-type cladding into the SCH; Q S , Q G , Q Q They are the charges in the SCH, Gateway, and QW regions, which also become current variables after being divided by the corresponding time constants; P is the photon density S multiplied by the volume V of the quantum well region QW Obtained, that is, the total number of photons; ε P is the gain compression factor related to the total number of photons, and its value is given by ε P =ε S / V QW Calculated.

[0043] Since the third-order rate equation can only obtain the total number of photons, in general, it is more appropriate to establish an equivalent circuit model using the optical parameters of the laser output optical power model. Therefore, the relationship between the total number of photons and the laser output optical power is introduced in the present invention:

[0044]

[0045] in Represents the output power value contributed by a single photon, which is a certain constant. out and Substituting into equation (5-8) we get the circuit equation (9-12):

[0046]

[0047]

[0048]

[0049]

[0050] in

[0051]

[0052]

[0053] I AQ =qV QW An Q I BQ =qV QW Bn Q 2 I CQ =qV QW Cn Q 3

[0054] I SPON =βqV QW Bn Q 2

[0055] C1=τ nS C2=τ nG

[0056] According to the above equation, we established Figure 1 The equivalent circuit model of the intrinsic network is shown in Figure 1, where I nS ,I nG ,I AQis equivalent to the current flowing through the diode element, and the remaining current terms are equivalent to the voltage-controlled current source; among them, the change of the charge in each region (SCH region, Gateway region, quantum well region) with time is equivalent to the current flowing through C1, C2, and C3; through the resistor RP, capacitor CP, voltage-controlled current source SPON and STIM, equation (12) is equivalent.

[0057] The intrinsic network equivalent circuit includes the SCH area, the exchange area between the SCH area and the Gateway area, the Gateway area, the exchange area between the Gateway area and the QW area, the QW area, the stimulated radiation area, etc. The structures of each area are shown in Figure 1 .

[0058] The package parasitic network circuit part of the present invention is constructed by gold wire, lumps and substrate; the gold wire includes inductance LB, resistance RB and capacitance CB, the lumps include lumped capacitance CS and lumped resistance RS, and the substrate includes substrate resistance RSUB;

[0059] The role of the package parasitic network circuit in the entire circuit model is mainly the parasitic effect brought by the packaged laser chip. The package parasitic network circuit can improve the impedance mismatch caused by the small internal resistance of the laser.

[0060] In the construction of the package parasitic network circuit, three sets of parameters are included:

[0061] 1) Parasitic parameters of gold wire: the series gold wire resistance RB introduced by the resistance of the gold wire, the series gold wire inductance LB introduced by the inductance of the gold wire, and the parallel gold wire capacitance CB introduced when the gold wire contacts the chip;

[0062] 2) Lumped parasitic parameters: represents the parallel lumped capacitance CS from the top metal plating layer to the substrate outside the ridge and the series lumped resistance RS contributed by the contact, ridge strip, and plating layer;

[0063] 3) Substrate parasitic parameters: substrate resistance RSUB introduced by the substrate and connected in series with CS.

[0064] The present invention also proposes a multi-parameter SCH-QW semiconductor laser circuit model constructed by the above construction method, wherein the circuit model includes an intrinsic network equivalent circuit part and a package parasitic parameter network circuit part;

[0065] The intrinsic network equivalent circuit part includes an SCH region, a Gateway region, a quantum well QW region and a stimulated radiation region; an SCH region and a Gateway region exchange region and / or a Gateway region and a QW region exchange region are respectively arranged between the Gateway region and the SCH region and / or the quantum well QW region; the SCH region and the Gateway region exchange region is used to represent the dynamic transport process of the carriers in the SCH region diffusing to the Gateway region and returning from the Gateway region to the SCH region; the Gateway region and the QW region exchange region is used to represent the dynamic transport process of the carriers in the Gateway region being captured by the QW region and the carriers in the QW region being excited to the Gateway region; the stimulated radiation region is used to represent the stimulated radiation and / or spontaneous radiation generating photons and emitting lasers.

[0066] The package parasitic parameter network circuit part includes a gold wire, a lumped part, and a substrate; the gold wire includes an inductor LB, a resistor RB, and a capacitor CB, the lumped part includes a lumped capacitor CS and a lumped resistor RS, and the substrate includes a substrate resistor RSUB.

[0067] The present invention also proposes the application of the above circuit model in circuit simulation; the circuit model described in the present invention can be used to simulate and simulate circuit characteristics including: saturation nonlinear effect parameters, the influence of ABC coefficient on model output; the saturation nonlinear effect parameters include: saturation gain coefficient g s , gain compression factor ε P The ABC coefficients for the model output include quantum well laser PI characteristics, small signal modulation response characteristics, and gain switching characteristics.

[0068] Gain compression refers to the downward compression of the gain curve and frequency hole burning caused by nonlinear phenomena such as gain saturation, that is, the gain decreases and is compressed as the photon density increases.

[0069] Package parasitics refer to the fact that during the process of packaging the laser chip into a device, gold wires are added to connect it to the carrier, etc., so package parasitic parameters are inevitably introduced, affecting the output characteristics of the laser.

[0070] The multi-parameters in the present invention are embodied in that different laser output characteristic simulations can be obtained by adjusting multiple parameters, including the values ​​of Auger recombination coefficient, gain saturation coefficient, capacitance CB and DC bias current, etc., which provides a certain reference for obtaining a laser design with narrow pulse width, high power and low threshold.

[0071] The beneficial effects of the present invention are as follows: the model of the present invention is applicable to various EDA tools with SPICE simulation function, and since the gain saturation nonlinear effect and the dynamic change of carriers are taken into consideration, the saturation nonlinear effect parameters (saturation gain coefficient g s , gain compression factor ε P ), ABC coefficients and other intrinsic parameters on the model output (quantum well laser PI characteristics, small signal modulation response characteristics, gain switching characteristics, etc.). The model of the present invention can also be used to analyze and discuss the influence of package parasitic parameters on the output characteristics of the laser. By adjusting the corresponding model parameters, the output characteristics of the laser are greatly improved. Taking the modulation response characteristics of the laser as an example, the laser modulation bandwidth is extended to 100GHz by adjusting the parameters, providing a design basis and reference for the actual production and design of high-speed semiconductor lasers used in 5G communications. Therefore, after considering factors such as gain compression, thermal electron emission, Gateway state, and package parasitics, the model can more comprehensively and completely reflect the working characteristics of the laser, can be used as a key basic model for OEIC design, and can also achieve the optimal design of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0073] Figure 1 This is the equivalent circuit diagram of the intrinsic network of the present invention.

[0074] Figure 2 This is the equivalent circuit diagram of the SCH-QW semiconductor laser of the present invention.

[0075] Figure 3 This is the PI characteristic related to C (Auger recombination coefficient) of the present invention.

[0076] Figure 4 For the present invention s (saturation gain coefficient) related to the short pulse characteristics of the gain switch.

[0077] Figure 5 This is the modulation response characteristic related to CB (gold wire capacitance) of the present invention.

[0078] Figure 6 This is the variable modulation current frequency response characteristic of the model after the parameters are changed in the present invention.

[0079] Figure 7It is a schematic diagram of the dynamic transport process of carriers and photons of the single quantum laser of the present invention. DETAILED DESCRIPTION

[0080] The invention is further described in detail with reference to the following specific embodiments and drawings. The process, conditions, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and common common sense in the art and are not particularly limited by the present invention.

[0081] With the rapid development of 5G communications, optical communications are the key to 5G technology, and semiconductor lasers play an irreplaceable and important role in it. Under ultra-high-speed modulation greater than 25GHz, quantum well effects, packaging effects, and gain nonlinear effects significantly affect the output effects of quantum well semiconductor lasers, and are important physical considerations in the design process of quantum well semiconductor lasers applied to 5G ultra-high-speed modulation scenarios. Combined with the above background, the circuit model described in the present invention has a good circuit logic mapping for the above three key physical mechanisms, including intrinsic network equivalent circuits and package parasitic network circuits.

[0082] The intrinsic network equivalent circuit is partially constructed based on the three-level rate equation, taking into account the Gateway state and the thermal electron emission effect, and taking into account the saturation nonlinear effect in the quantum well and the dynamic characteristics of the carrier lifetime; the package parasitic network circuit is a circuit construction for the parasitic effects generated in the production process of semiconductor lasers. The model disclosed in the present invention is suitable for various EDA tools with SPICE simulation functions. Based on this model, the design output of the semiconductor laser can be analyzed in advance and the design input can be optimized, which can escort the research and development of semiconductor lasers in actual application scenarios (such as 5G ultra-high-speed modulation).

[0083] Example

[0084] This embodiment takes the establishment of an equivalent circuit model of a ridge-stripe semiconductor laser with InGaAs quantum well and AlGaAs SCH as an example to further explain the present invention in detail.

[0085] The SCH-QW semiconductor laser circuit model in this embodiment is specifically implemented as follows:

[0086] Step 1: Construct the equivalent circuit of the intrinsic network based on the three-level rate equation. After considering the gain saturation nonlinear effect and the carrier ABC recombination mechanism, the rate equation is in the form of:

[0087]

[0088]

[0089]

[0090]

[0091] In the formula, τ nS , τ nG and τ nQ are the carrier lifetimes in the SCH, Gateway, and QW regions respectively; τ D is the transport time constant; τ G is the lifetime of carriers in the channel state; τ C is the bipolar capture time constant; τ ESC is the escape time constant caused by thermal emission; Γ is the light confinement factor; υ g is the group velocity; τ P is the photon lifetime; β is the spontaneous radiation coupling factor; g(n Q ) is the carrier-related material gain; I i is the current injected from the n-type cladding into the SCH; Q S , Q G , Q Q are the charges of SCH, Gateway, and QW regions respectively; ε P is the gain compression factor related to the total number of photons; V OUT represents the output power of the equivalent circuit model; p represents the output power value contributed by a single photon; V QW is the volume of the quantum well; A is the SRH recombination coefficient, B is the spontaneous emission coefficient, and C is the Auger recombination coefficient.

[0092] Step 2: Convert the rate equation described in step 1 into a circuit equation:

[0093]

[0094]

[0095]

[0096]

[0097] Among them I nS ,I nG ,I AQ is equivalent to the current flowing through the diode element, and the remaining current terms are equivalent to the voltage-controlled current source; among them, the change of the charge in each region (SCH region, Gateway region, quantum well region) with time is equivalent to the current flowing through C1, C2, and C3; through the resistor RP, the capacitor CP, the voltage-controlled current source SPON and STIM, the equation (8) is equivalent, and the equivalent components are connected according to the relationship described in the equation to obtain the equivalent circuit part of the intrinsic network, as shown in Figure 1 shown.

[0098] Step 3: Considering the impact of the actual package, add and establish the corresponding package parasitic network circuit part based on the intrinsic network equivalent circuit part. The package parasitic network circuit part includes three groups of parameters:

[0099] 1) Gold wire parasitic parameters: the series gold wire resistance RB introduced by the gold wire's resistance, the series gold wire inductance LB introduced by the gold wire's inductance, and the parallel gold wire capacitance CB introduced when the gold wire contacts the chip.

[0100] 2) Lumped parasitic parameters: represents the parallel lumped capacitance CS from the top metal plating layer to the substrate outside the ridge and the series lumped resistance RS contributed by the contact, ridge strips and plating layer.

[0101] 3) Substrate parasitic parameters: substrate resistance RSUB introduced by the substrate and connected in series with CS.

[0102] Step 4: Connect the above-mentioned package parasitic network circuit part with Figure 1 By connecting the laser intrinsic network equivalent circuit shown in FIG. 1 , the complete SCH-QW equivalent circuit model can be obtained, as shown in FIG. Figure 2 Then, the model parameters are set to further improve the output characteristics of the laser by adjusting the corresponding model parameters. The model parameters are set as shown in Table 1:

[0103] Table 1 Main parameters in the equivalent circuit model

[0104]

[0105]

[0106] By constructing and implementing the above SCH-QW equivalent circuit model, the corresponding simulation analysis results can be obtained, such as Figure 3 The figure shows the PI characteristic curve of the laser when the Auger recombination coefficient C is changed. It can be seen that as C increases, the laser threshold gradually increases. This is because the increase in the Auger recombination coefficient will lead to an increase in the carrier lifetime, thereby affecting the laser threshold. This conclusion can also be obtained by solving the threshold current analytical formula of the rate equation.

[0107] Figure 4 To change the saturation gain factor g s , the gain switching short pulse characteristics of the laser. The pulse change trend in the figure is that the pulse occurrence time moves forward, the pulse width becomes narrower, and the peak power first increases and then decreases. Since the saturation gain plays a decisive role in the upper limit of the gain, when the differential gain can make the overall gain quickly reach saturation, that is, the saturation gain, the size of the saturation gain determines the intensity of the stimulated radiation.

[0108] Figure 5To change the gold wire capacitance, the laser's small signal frequency response characteristics. As can be seen from the figure, at the beginning, as CB increases, the peak-to-peak value of the curve resonance increases, and the 3dB bandwidth also increases accordingly. However, when CB increases to 6pF, the peak-to-peak value of the resonance begins to decline, and the 3dB bandwidth also begins to decrease. It can be seen that the value of CB can well improve the flatness of the low-frequency response, reduce the resonance peak to avoid distortion caused by higher response, and has little effect on the 3dB bandwidth. Therefore, a reasonable choice of CB value is an important factor in ensuring that the laser has a good small signal frequency response.

[0109] In addition, by adjusting the intrinsic parameters and parasitic parameters of the laser, an LD with better small signal frequency response characteristics can be obtained. Figure 6 This is the small signal frequency response curve of the variable modulation current obtained after adjusting the parameters. It can be seen from the figure that after adjusting the parameters, the laser bandwidth response is greatly improved, the laser 3dB bandwidth reaches 30GHz, and the low-frequency response does not roll off, the flatness is high, and there is no distortion at the resonant peak response. Therefore, the actual modulation bandwidth is close to 30GHz when the laser works at 42.7mW. Therefore, a very large bandwidth laser model can be obtained by changing the LD parameters, which provides a reference method for the actual design and production of 25GHz bandwidth lasers used in 5G communications.

[0110] The circuit model of the present invention can be applied to the design of quantum well semiconductor lasers with low threshold, high power and high modulation bandwidth. In this scenario, the various parts of the circuit model are composed of parasitic network parameters, SCH region, Gateway region, quantum well region and stimulated emission region. It has a certain guiding role in designing low threshold and high power quantum well lasers using electronic design automation tools.

[0111] In summary, the model of the present invention is suitable for various EDA tools with SPICE simulation function. Due to the consideration of the gain saturation nonlinear effect and the dynamic change of carriers, it can well simulate and simulate the influence of intrinsic parameters such as saturation nonlinear effect parameters (saturation gain coefficient, gain compression factor), ABC coefficient on model output (quantum well laser PI characteristics, small signal modulation response characteristics, gain switch characteristics, etc.), and the reliability of the simulation results is verified by solving the rate equation analysis. The model of the present invention can also be used to analyze and discuss the influence of package parasitic parameters on the output characteristics of the laser, such as by adjusting the corresponding model parameters to improve the output characteristics of the laser, and provide design basis and reference for the actual production and design of high-speed semiconductor lasers used in 5G communication. Therefore, after considering factors such as gain compression, thermal electron emission, Gateway state, and package parasitics, the model can fully and comprehensively reflect the working characteristics of the laser, can be used as a key basic model for OEIC design, and can also achieve the optimization design of the laser.

[0112] References

[0113] [1]BPTsou,DLPulfrey.A versatile SPICE model for quantum-welllasers[J].IEEE Journal of Quantum Electronics,1997,33(2):246-254.

[0114] [2]DWLim,Cho HU,Jang HT,et al.PSPICE Modeling ofInAlGaN LDs Using the Multistate Rate Equations[C].IEEE Region 10Conference.IEEE,2018:1065-1069.

[0115] [3]D.McDonald,RFO'Dowd.Comparison oftwo-and three-level rateequations in the modeling ofquantum-well lasers[J].IEEEjournal ofquantumelectronics,1995,31(11):1927-1934.

[0116] [4] J. Piprek, F. B.Witzigmann.On the uncertainty of the Augerrecombination coefficient extracted from InGaN / GaN light-emitting diodeefficiency droop measurements[J].Applied Physics Letters, 2015,106(10):101101.

[0117] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the attached claims.

Claims

1. A multi-parameter SCH-QW semiconductor laser circuit model, characterized in that: The circuit model is constructed based on quantum well effect, packaging characteristics and gain nonlinear characteristics, including an intrinsic network equivalent circuit part and a packaging parasitic network circuit part; The intrinsic network equivalent circuit part includes a SCH region, a Gateway region, a quantum well QW region and a stimulated radiation region; The SCH region exchanges carriers with the Gateway region by means of bipolar diffusion and carrier release; The quantum well QW region has a quantum well structure, and exchanges carriers through capture and thermal excitation; The Gateway region serves as a portal for the SCH region and the QW region to exchange carriers; The stimulated emission zone can generate photons and emit laser light through stimulated emission and / or spontaneous emission; The package parasitic network circuit part includes a gold wire, a lumped part, and a substrate; the gold wire includes an inductor LB, a resistor RB, and a capacitor CB; the lumped part includes a lumped capacitor CS and a lumped resistor RS; and the substrate includes a substrate resistor RSUB.

2. The circuit model according to claim 1, characterized in that An exchange region between the SCH region and the Gateway region and / or an exchange region between the Gateway region and the QW region are respectively arranged between the Gateway region and the SCH region and / or the quantum well QW region. The exchange region between the SCH region and the Gateway region is used to represent the dynamic transport process of the carriers in the SCH region diffusing to the Gateway region and returning from the Gateway region to the SCH region. The exchange region between the Gateway region and the QW region is used to represent the dynamic transport process of the carriers in the Gateway region being captured by the QW region and the carriers in the QW region being excited to the Gateway region.

3. A method for constructing a circuit model as claimed in claim 1 or 2, characterized in that: It includes the construction of the intrinsic network equivalent circuit part and the construction of the package parasitic network circuit part.

4. The construction method according to claim 3, characterized in that: The intrinsic network equivalent circuit is partially constructed based on the three-level rate equation of the semiconductor laser, which includes the carrier concentration rate equation of the SCH region, the Gateway region, and the quantum well QW region, and a photon concentration rate equation; wherein, The carrier concentration rate equation in the SCH region is: The carrier concentration rate equation in the Gateway region is: The carrier concentration rate equation in the quantum well region is: Photon concentration rate equation: Among them, n i (t) is the contribution of external injection to SCH carriers; n S 、n G and n Q Respectively represent the carrier concentrations in the SCH region, Gateway region, and QW region; S is the photon density; Γ is the light confinement factor, which represents the ratio of the optical power propagating in the active layer; υ g is the group velocity; ε S is the gain compression factor related to photon density, which describes that the gain is compressed as the photon density increases; τ P is the photon lifetime, which is related to the intracavity loss; τ D is the transport time constant, which is used to describe the process of carrier diffusion from SCH to Gateway through the bipolar; τ G is the lifetime of carriers in the channel state; τ C is the bipolar capture time constant, which is used to describe the process of carrier transfer from Gateway to QW; τ nS is the carrier lifetime in the SCH region; τ ESC is the carrier escape time; τ nG is the carrier lifetime in the Gateway region; τ nQ is the carrier lifetime in the QW region; β is the spontaneous radiation coupling factor, which indicates the ratio of spontaneous radiation coupling of carriers into the lasing mode; g(n Q ) is the carrier-related material gain.

5. The construction method according to claim 4, characterized in that: In the carrier-dependent material gain g(n Q ) adds the saturation gain factor g s Improved, the improved g(n Q ) is a nonlinear expression, and the expression is as follows: Where g0 is the differential gain, n Q is the carrier concentration in the QW region, n0 is the transparent carrier concentration, g s is the optical gain coefficient when the laser is in saturation state.

6. The construction method according to claim 3, characterized in that: The carrier ABC recombination mechanism is also added to the intrinsic network equivalent circuit model. The concentration dependence of different recombination processes on carriers reflected by the ABC recombination mechanism replaces the average carrier lifetime to describe the carrier recombination rate. The carrier lifetime in the quantum well region of the semiconductor laser is a function related to the carrier concentration, which is expressed as the ABC coefficient expression of the carrier lifetime: 1 / τ nQ (n Q )≈A+Bn Q +Cn Q 2 , where A is the Shockley-Read-Hall recombination coefficient, B is the spontaneous emission coefficient, and C is the Auger recombination coefficient.

7. The construction method according to claim 4, characterized in that: The third-level rate equation of the equivalent circuit model is converted into a rate equation of electrical related parameters, and Q=nqV is introduced, where Q is the charge, q is the charge per unit electron, n is the carrier concentration, and V is the volume of the quantum well region. Both ends of the rate equation are multiplied by qV, and the relationship between dn / dt and n / t is converted to dQ / dt and Q / t:; The relationship between the total number of photons and the output optical power of the laser is introduced: in Represents the output power value contributed by a single photon, and finally obtains the converted equation: in I AQ =qV QW An Q ,I BQ =qV QW Bn Q 2 ,I CQ =qV QW Cn Q 3 , I SPON =βqV QW Bn Q 2 , C1=τ nS ,C2=τ nG , I i is the current injected from the n-type cladding into the SCH; Q S , Q G , Q Q They are the charges of the SCH, Gateway, and QW regions, which become current variables after being divided by the corresponding time constants; the total number of photons P is the photon density S multiplied by the volume V of the quantum well region. QW ; ε P is the gain compression factor related to the total number of photons, and its value is given by ε P =ε S / V QW Calculated; I nS ,I nG ,I AQ It is equivalent to the current flowing through the diode element, and the other current terms are equivalent to the voltage-controlled current source; among them, the change of the charge in the SCH area, Gateway area, and quantum well area over time is equivalent to the current flowing through C1, C2, and C3; through the resistor RP, capacitor CP, voltage-controlled current source SPON and STIM, the equation is equivalent 8. The construction method according to claim 3, characterized in that: The construction of the package parasitic network circuit part includes three sets of parameters: 1) Parasitic parameters of gold wire: the series gold wire resistance RB introduced by the resistance of the gold wire, the series gold wire inductance LB introduced by the inductance of the gold wire, and the parallel gold wire capacitance CB introduced when the gold wire contacts the chip; 2) Lumped parasitic parameters: represents the parallel lumped capacitance CS from the top metal plating layer to the substrate outside the ridge and the series lumped resistance RS contributed by the contact, ridge strip, and plating layer; 3) Substrate parasitic parameters: substrate resistance RSUB introduced by the substrate and connected in series with CS.

9. Application of the circuit model according to claim 1 or 2 in simulation and emulation of the influence of saturation nonlinear effect parameters and ABC coefficients on model output; the saturation nonlinear effect parameters include: Saturation gain factor g s , gain compression factor ε P The ABC coefficients for the model output include quantum well laser PI characteristics, small signal modulation response characteristics, and gain switching characteristics.

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