A multi-parameter SCH-QW semiconductor laser circuit model and a construction method thereof

Abstract

The application discloses a kind of multi-parameter SCH-QW semiconductor laser circuit model.The circuit model includes intrinsic network equivalent circuit part and encapsulated parasitic network circuit part;The intrinsic network equivalent circuit part includes SCH area, Gateway area, quantum well QW area and stimulated radiation area;The SCH area exchanges carrier with Gateway area by the way of bipolar diffusion and carrier release;The quantum well QW area has quantum well structure, and exchanges carrier by trapping and thermal excitation;The Gateway area is as the door of SCH area and QW area exchange carrier;The encapsulated parasitic network circuit part includes gold wire, lumped part, substrate;The gold wire includes inductance LB, resistance RB, capacitance CB, the lumped part includes lumped capacitance CS, lumped resistance RS, and the substrate includes substrate resistance RSUB.The application also discloses the construction method of the above-mentioned circuit model and the application in the simulation and simulation of the influence of saturation nonlinear effect parameter, ABC coefficient on model output.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser technology, specifically relating to a multi-parameter SCH-QW semiconductor laser circuit model and its construction method. Background Technology

[0002] Among numerous light source devices, laser light sources possess significant advantages. They not only exhibit pure monochromaticity, strong coherence, and high brightness, but also, with the development and maturation of laser technology, their price has gradually decreased. Therefore, they are widely used in industry, agriculture, communications, medicine, scientific research, and national defense. The birth and development of laser technology ignited a major revolution in the field of optics, propelled the rapid development of information technology, and ushered humanity into the era of high-speed optical communication. Among the many types of lasers, semiconductor lasers, with their small size and direct electrical modulation capabilities, are widely used in high-speed, long-distance fiber optic communication systems and serve as an important component (emitting light source) of optoelectronic integrated circuits.

[0003] As is well known, improving the transmission quality and speed of optical fiber communication systems requires that each component of the system can achieve high-quality, high-speed information transmission and possess excellent performance such as high-speed modulation. The core components of an optical fiber communication system include semiconductor lasers, optical amplifiers, photodetectors, and optical modulators. The quality of these components' operating characteristics directly affects the improvement of system performance. Therefore, researching high-performance core transceiver devices applicable to high-speed optical communication systems has become a current research hotspot.

[0004] Modeling and simulating lasers is essential for meeting the design and manufacturing needs of Optoelectronic Integrated Circuits (OEICs). Since optoelectronic integrated circuits are highly integrated circuits, they cannot be modified after design and manufacturing. Therefore, to verify the compliance and performance of the designed integrated optical circuits before manufacturing, it is necessary to model and simulate the optoelectronic integrated circuits in advance. This method can significantly reduce defective chip losses and save costs. Thus, Optoelectronic Integrated Circuit Computer-Aided Design (OEIC CAD) plays a crucial role in shortening circuit design cycles, reducing resource consumption, improving device performance, and accelerating development processes. The core issue is establishing an equivalent circuit model of the optoelectronic device that can comprehensively reflect its performance and can be described using purely electronic components. As a vital component of the optical transmitter in optical communication systems, semiconductor lasers require a model that accurately describes their performance. While numerical analysis can directly obtain various characteristics of the laser, it cannot analyze parasitic elements and driving circuits. Establishing an equivalent circuit model of the semiconductor laser effectively solves this problem.

[0005] Based on this premise, this paper focuses on quantum well semiconductor lasers, taking into account the characteristics inside and outside the well, packaging characteristics, and gain nonlinearity. It constructs an equivalent circuit model that is realistic and can fully reflect the output characteristics of the laser. This model not only meets the technical requirements of today's fast communication era, but also, combined with the model, studies the influence of key parameters in the laser, including intrinsic parameters and parasitic parameters, on the laser response characteristics. This is also an important approach to the optimization design of semiconductor lasers. Summary of the Invention

[0006] To address the shortcomings of the aforementioned technologies, this invention proposes a multi-parameter SCH-QW (separately confined quantum well) semiconductor laser circuit model and its construction method. The circuit model includes an intrinsic network equivalent circuit part and an encapsulated parasitic network circuit part.

[0007] Based on the quantum well effect, packaging characteristics, and gain nonlinearity, this invention constructs a multi-parameter SCH-QW semiconductor laser circuit model.

[0008] The quantum well effect refers to the phenomenon where, due to the laser's active region thickness approaching the electron wavelength, the quantum theoretical properties of charge carriers begin to manifest. This manifests as electrons being confined within a quantum well along the x-axis, while remaining unconfined in the yz plane. Therefore, this structure is also called a quantum well structure. The effects exhibited by quantum well structures are called quantum well effects, including a significantly reduced threshold current required to achieve population inversion (i.e., laser radiation), narrower gain curves and linewidths, and easier realization of short-wavelength lasing.

[0009] The packaging characteristics refer to the connection between gold wires and the carrier, etc., that is added when the laser chip is packaged into a device. Therefore, it is inevitable 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, etc.

[0010] The aforementioned gain nonlinearity refers to the fact that due to the quantum size effect within the quantum well laser, when the density of states takes a certain value, an increase in carrier concentration will approach a complete distribution reversal, and the increase in gain will show a saturation tendency, eventually tending towards a saturation value.

[0011] This invention proposes a method for constructing a multi-parameter SCH-QW semiconductor laser circuit model, used to construct the intrinsic network equivalent circuit and encapsulate the parasitic network circuit; wherein,

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

[0013] The aforementioned third-order rate equation is universal in the equivalent circuit model and can be used for both small-signal and large-signal analysis. Taking the dynamic transport process of charge carriers and photons in an InGaAs-AlGaAs single quantum laser as an example, such as... Figure 7 As shown, based on the set of differential equations describing the dynamic process, we obtain carrier concentration rate equations for three regions (including the SCH region, Gateway region, and quantum well QW region) and a photon concentration rate equation, i.e., the third-order rate equations. [1-3] :

[0014] SCH region carrier concentration rate equation:

[0015]

[0016] Gateway region carrier concentration rate equation:

[0017]

[0018] Quantum well region carrier concentration rate equation:

[0019]

[0020] Photon concentration rate equation:

[0021]

[0022] The SCH region refers to the separated confined heterojunction region, which exchanges carriers with the Gateway region through bipolar diffusion and carrier release.

[0023] The Gateway region is the gateway for the exchange of carriers between the SCH region and the QW region, and is therefore also referred to as the channel state;

[0024] The quantum well (QW) region refers to a structure with a quantum well that can trap and thermally excite carriers for exchange.

[0025] In the above formulas, n i (t) represents the contribution of external injection to SCH carriers; n S n G and n Q Γ represents the carrier concentrations in the SCH, Gateway, and QW regions, respectively; S is the photon density; Γ is the optical confinement factor, representing the proportion of optical power propagating within the active layer; υ g Group velocity; ε S τ is a photon density-dependent gain compression factor, describing how gain is compressed as photon density increases; P The photon lifetime is related to the cavity loss; τ Dτ is the transport time constant, used to describe the process of charge carriers diffusing from the SCH through the bipolar junction to the Gateway; G τ represents the lifetime of charge carriers in the channel state. C τ is the bipolar trapping time constant, used to describe the process of carrier transport from the Gateway to the QW; nS τ is the carrier lifetime in the SCH region. ESC τ is the carrier escape time; nG The carrier lifetime of the Gateway region; τ nQ β is the carrier lifetime in the QW region; β is the spontaneous emission coupling factor, representing the ratio of carriers spontaneously coupled into the lasing mode; g(n Q ) represents the carrier-related material gain.

[0026] Based on the theory of in-well saturation nonlinearity and carrier lifetime dynamic characteristics, this invention improves the above equations and converts them into an equivalent circuit of the intrinsic network, such as... Figure 1 As shown.

[0027] Figure 1 In the diagram, CJ and CP represent the junction capacitance, which is approximately the parallel-plate capacitance composed of the cladding and active region; E1, E2, and E3 respectively provide currents I to C1, C2, and C3. nS I nG I AQ The voltage sources are: VIS, VIG, VIQ, VI1, VI2, and VI3, which are independent voltage sources with a power supply of 0V and used as ammeters. This allows direct reference to the current of a specific branch, facilitating the later representation of the model. To avoid floating node issues in the simulation, I... nS I nG I AQ We use diodes as an equivalent, and the remaining current terms are equivalent to voltage-controlled current sources, i.e., I0 VI1 I VI2 I VI3 These are the current sources whose current values ​​are recorded by VI1, VI2, and VI3, and are used to subsequently represent the currents of other branches. nS I nG I AQ I D I G I C I ESC I STIM I SPON RP represents a voltage-controlled current source related to carrier concentration; I BQ I CQ This refers to voltage-controlled current sources associated with spontaneous recombination and voltage-controlled current sources associated with Auger recombination.

[0028] The in-well saturation nonlinearity refers to the quantum size effect within the quantum well laser. When the density of states takes a certain value, the increase in carrier concentration will approach a complete reversal of the distribution. The increase in gain shows a saturation tendency and eventually tends to a saturation value, rather than a linear representation.

[0029] The aforementioned theory of carrier lifetime dynamic characteristics states that, due to the drastic fluctuations in carriers within the quantum well region of a semiconductor laser, the carrier lifetime is not a constant but a function related to the carrier concentration, expressed as the ABC coefficient expression for 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] Based on the saturation nonlinearity effect present in quantum well lasers, this invention addresses the g(n) in equations (3) and (4). Q The purely linear representation of g(n) has been improved; before the improvement, it was g(n) Q )=g0(n Q -n0), the improved version of this invention adds a saturation gain coefficient g to the equation. s This changes the gain from a linear to a nonlinear representation, making it closer to reality. A saturation gain coefficient g is added. s Improved g(n) Q The expression for the nonlinear representation is:

[0031]

[0032] In the formula, 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, population inversion is achieved. s This is the optical gain coefficient of the laser when it is in saturation. This coefficient is determined by multiple factors such as the band structure, density of states, and distribution function.

[0033] Based on the theory of carrier lifetime dynamic characteristics, this invention adds a carrier ABC recombination mechanism to the intrinsic network equivalent circuit model.

[0034] The aforementioned carrier ABC recombination mechanism refers to replacing the carrier recombination rate described by the average carrier lifetime with an ABC model that utilizes the dependence of different recombination processes on carrier concentration. The carrier recombination mechanisms described by the ABC model include three processes: Shockley-Read-Hall (SRH) recombination, radiative recombination, and Auger recombination. That is, the average carrier lifetime is 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.

[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 It was replaced by a more accurate ABC model, and I was used in the equivalent circuit equation (11). AQ I BQ I CQ This represents the influence of three different composite mechanisms in the ABC model.

[0036] The improved third-order rate equation of the semiconductor laser of this invention can be converted into the following circuit equation:

[0037] The third-order rate equation (1-4) is a rate equation related to concentration. In the equivalent circuit model, it needs to be transformed into a rate equation related to electrical 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, multiplying both sides of the rate equation by qV, the relationship between dn / dt and n / t can be transformed into dQ / dt and Q / t, which are related to current, and thus transformed into the charge equation (5-8).

[0038]

[0039]

[0040]

[0041]

[0042] In the formula, I i Q represents the current injected from the n-type cladding into the SCH. S Q G Q Q These represent the charges in the SCH, Gateway, and QW regions, respectively, which, when divided by the corresponding time constants, also become the current variables; P is the photon density S multiplied by the volume V of the quantum well region. QW The total number of photons obtained; ε P The gain compression factor is 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 yield the total number of photons, but in general, it is more appropriate to establish an equivalent circuit model using the laser output power as the optical parameter, this invention introduces the relationship between the total number of photons and the laser output power:

[0044]

[0045] in The output power contributed by a single photon is a definite constant. This relates to the ABC recombination mechanism and V... out and Substituting into equation (5-8), we obtain 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] Based on the above equation, the following was established: Figure 1 The intrinsic network equivalent circuit model shown is shown, where I nS I nG I AQThe equivalent current is 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 charge over time in each region (SCH region, Gateway region, quantum well region) is equivalent to the current flowing through C1, C2, and C3; the equation (12) is derived by using resistor RP, capacitor CP, voltage-controlled current source SPON, and STIM.

[0057] The intrinsic network equivalent circuit includes the SCH region, the SCH-Gateway region exchange region, the Gateway region, the Gateway-QW region exchange region, the QW region, and the stimulated emission region, etc. The structures of each region are shown in [the diagram]. Figure 1 .

[0058] The parasitic network circuit portion of the present invention is constructed using gold wires, lumped elements, and a substrate; the gold wires include inductors LB, resistors RB, and capacitors CB; the lumped elements include lumped capacitors CS and lumped resistors RS; and the substrate includes a substrate resistor RSUB.

[0059] The role of the encapsulated parasitic network circuit in the overall circuit model is mainly to mitigate the parasitic effects brought about by the encapsulation of the laser chip. By encapsulating the parasitic network circuit, the impedance mismatch caused by the low internal resistance of the laser can be improved.

[0060] The construction of encapsulated parasitic network circuits includes three sets of parameters:

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

[0062] 2) Lumped parasitic parameters: These represent the parallel lumped capacitance CS from the top metal plating layer to the outer substrate of the ridge, and the series lumped resistance RS contributed by the contacts, ridges, and plating layer.

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

[0064] This invention also proposes a multi-parameter SCH-QW semiconductor laser circuit model constructed by the above construction method. The circuit model includes an intrinsic network equivalent circuit part and a packaged parasitic parameter network circuit part.

[0065] The intrinsic network equivalent circuit includes a SCH region, a Gateway region, a quantum well (QW) region, and a stimulated emission region. Exchange regions between the Gateway region and the SCH region and / or the quantum well (QW) region are respectively provided. The SCH region-Gateway region exchange region represents the dynamic transport process of carriers in the SCH region diffusing into the Gateway region and returning from the Gateway region to the SCH region. The Gateway region-QW region exchange region represents the dynamic transport process of carriers in the Gateway region being captured by the QW region and carriers in the QW region being excited into the Gateway region. The stimulated emission region represents the generation of photons through stimulated emission and / or spontaneous emission, emitting laser light.

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

[0067] This invention also proposes the application of the above-mentioned circuit model in circuit simulation; the circuit characteristics that the circuit model described in this invention can be used to simulate include: the influence of saturated nonlinear effect parameters and ABC coefficients on the model output; the saturated nonlinear effect parameters include: the saturated gain coefficient g. s Gain compression factor ε P The ABC coefficients in the model output include the quantum well laser's 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 burning caused by nonlinear phenomena such as gain saturation. In other words, the gain decreases and is compressed as the photon density increases.

[0069] Packaging parasitics refers to the parasitic parameters that inevitably arise during the packaging process of laser chips, which involves the addition of gold wires and carriers for connection. These parasitic parameters affect the output characteristics of the laser.

[0070] The multi-parameter feature in this invention is that different laser output characteristics can be simulated by adjusting the values ​​of multiple parameters, including Auger recombination coefficient, gain saturation coefficient, capacitor CB, and DC bias current. This provides a certain reference for the design of lasers with narrow pulse width, high power, and low threshold.

[0071] The beneficial effects of this invention are as follows: the model of this invention is applicable to various EDA tools with SPICE simulation capabilities. Because it considers the gain saturation nonlinearity effect and the dynamic changes of charge carriers, it can effectively simulate and model parameters including saturation nonlinearity (saturation gain coefficient g). s Gain compression factor ε P The model of this invention examines the influence of intrinsic parameters such as gain compression, thermionic emission, gateway state, and packaging parasitics on the model output (quantum well laser PI characteristics, small-signal modulation response characteristics, gain switching characteristics, etc.). The model can also be used to analyze and discuss the impact of packaging parasitic parameters on laser output characteristics. By adjusting the corresponding model parameters, the laser output characteristics can be significantly improved. Taking the laser's modulation response characteristics as an example, parameter adjustments can extend the laser's modulation bandwidth to 100GHz, providing a 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, thermionic emission, gateway state, and packaging parasitics, the model can comprehensively and completely reflect the laser's operating characteristics, serving as a key foundational model for OEIC design and enabling optimized laser design. Attached Figure Description

[0072] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or 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 creative effort.

[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 relates to the PI characteristics of C (Auger composite coefficient) in this invention.

[0076] Figure 4 For the present invention g s Gain-switching short-pulse characteristics related to (saturation gain coefficient).

[0077] Figure 5 This relates to the modulation response characteristics of the CB (gold wire capacitor) in this invention.

[0078] Figure 6 This describes the variable modulation current frequency response characteristics of the model after changing the parameters in this invention.

[0079] Figure 7This is a schematic diagram of the dynamic transport process of charge carriers and photons in the single quantum laser of this invention. Detailed Implementation

[0080] The invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the invention are all common knowledge and general knowledge in the art, and the invention does not have any particular limitations.

[0081] With the rapid development of 5G communication, optical communication, as a key carrier of 5G technology, relies heavily on semiconductor lasers. In ultra-high-speed modulation above 25 GHz, the quantum well effect, packaging characteristics, and gain nonlinearity significantly influence the output characteristics of quantum well semiconductor lasers, making them crucial physical considerations for their application in 5G ultra-high-speed modulation scenarios. Against this backdrop, the circuit model described in this invention provides a good circuit logic mapping for all three key physical mechanisms, including intrinsic network equivalent circuits and packaging parasitic network circuits.

[0082] The intrinsic network equivalent circuit is constructed based on a third-order rate equation, considering gateway states and hot electron emission effects, as well as the saturation nonlinearity and dynamic characteristics of carrier lifetime within the quantum well. The encapsulated parasitic network circuit is a circuit construction designed to address parasitic effects generated during the semiconductor laser manufacturing process. The model disclosed in this invention is applicable to various EDA tools with SPICE simulation capabilities. Based on this model, the design output of semiconductor lasers can be pre-analyzed and the design input optimized, providing support for the research and development of semiconductor lasers in practical application scenarios (such as 5G ultra-high-speed modulation).

[0083] Example

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

[0085] The specific implementation method of the SCH-QW semiconductor laser circuit model in this embodiment is as follows:

[0086] Step 1: Construct the equivalent circuit part of the intrinsic network based on the third-order rate equation. Considering the gain saturation nonlinearity effect and the carrier ABC recombination mechanism, the rate equation takes the following form:

[0087]

[0088]

[0089]

[0090]

[0091] In the formula, τ nS τ nG and τ nQ These represent the carrier lifetimes of the SCH, Gateway, and QW regions, respectively; τ D τ is the transport time constant; G τ represents the lifetime of charge carriers in the channel state. C τ is the bipolar capture time constant; ESC Γ is the escape time constant caused by thermal emission; Γ is the optical confinement factor; υ g Group velocity; τ P β is the photon lifetime; β is the spontaneous emission coupling factor; g(n) Q ) represents the carrier-related material gain; I i Q represents the current injected from the n-type cladding into the SCH. S Q G Q Q These are the charge quantities of the SCH, Gateway, and QW regions, respectively; ε P V is the gain compression factor related to the total number of photons. OUT V represents the output power of the equivalent circuit model; p represents the output power contributed by a single photon; V QW denoted as 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: Transform the rate equation described in Step 1 into a circuit equation:

[0093]

[0094]

[0095]

[0096]

[0097] Among them I nS I nG I AQ The equivalent current is 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 charge over time in each region (SCH region, Gateway region, quantum well region) 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 (8) is derived, and by connecting the equivalent elements according to the relationship described by the equation, the equivalent circuit part of the intrinsic network can be obtained, such as Figure 1 As shown.

[0098] Step 3: Considering the impact of actual packaging, a corresponding packaging parasitic network circuit is added and established based on the intrinsic network equivalent circuit. This packaging parasitic network circuit includes three sets of parameters:

[0099] 1) Parasitic parameters of gold wire: series resistance RB introduced by the resistivity of gold wire, series inductance LB introduced by the inductivity of gold wire, and parallel capacitance CB introduced when gold wire is in contact with chip.

[0100] 2) Lumped parasitic parameters: These represent the parallel lumped capacitance CS from the top metal plating layer to the outer substrate of the ridge, and the series lumped resistance RS contributed by the contacts, ridges, 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 packaged parasitic network circuit section with... Figure 1 By connecting the equivalent circuit parts of the laser intrinsic network shown, the complete SCH-QW equivalent circuit model can be obtained, as follows. Figure 2 As shown in Table 1, the model parameters are then set, and the output characteristics of the laser are further improved by adjusting the corresponding model parameters.

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

[0104]

[0105]

[0106] By constructing and implementing the above SCH-QW equivalent circuit model, 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 of the Auger recombination coefficient leads to the increase of carrier lifetime, which in turn affects the laser threshold. This conclusion can also be obtained by solving the analytical expression of the threshold current in the rate equation.

[0107] Figure 4 To change the saturation gain coefficient g s The gain switching short pulse characteristics of the laser are shown in the figure. The pulse change trend is that the pulse occurrence time is moved forward, the pulse width is narrowed, 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, i.e., the saturation gain, the magnitude of the saturation gain determines the intensity of stimulated emission.

[0108] Figure 5To modify the small-signal frequency response characteristics of the laser by changing the gold wire capacitance, the figure shows that initially, as the CB increases, the peak value of the resonant peak increases, and the 3dB bandwidth also increases. However, when CB increases to 6pF, the peak value of the resonant peak begins to decline, and the 3dB bandwidth also begins to decrease. It can be seen that the value of CB can effectively improve the flatness of the low-frequency response, reduce the resonant peak value to avoid distortion caused by a higher response, and has a relatively small impact on the 3dB bandwidth. Therefore, a reasonable selection of the CB value is an important factor in ensuring that the laser has a good small-signal frequency response.

[0109] Furthermore, by adjusting the intrinsic and parasitic parameters of the laser, an LD with better small-signal frequency response characteristics can be obtained. Figure 6 The figure shows the small-signal frequency response curve of the modulated current after parameter adjustment. As can be seen from the figure, the laser bandwidth response is greatly improved after parameter adjustment. The 3dB bandwidth of the laser reaches 30GHz, and there is no roll-off in the low-frequency response. 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 is working at 42.7mW. Thus, a laser model with a maximum bandwidth can be obtained by changing the LD parameters. This provides a reference method for the actual design and production of 25GHz bandwidth lasers used in 5G communication.

[0110] The circuit model of this invention can be applied to the design of quantum well semiconductor lasers with low threshold power, high power, and high modulation bandwidth. In this scenario, the circuit model consists of parasitic network parameters, a SCH region, a Gateway region, a quantum well region, and a stimulated emission region. It provides guidance for designing low-threshold, high-power quantum well lasers using electronic design automation (EDA) tools.

[0111] In summary, the model of this invention is applicable to various EDA tools with SPICE simulation capabilities. Because it considers gain saturation nonlinearity and carrier dynamics, it can effectively simulate and model the influence of intrinsic parameters, including saturation nonlinearity parameters (saturation gain coefficient, gain compression factor), ABC coefficients, and other intrinsic parameters, on the model output (quantum well laser PI characteristics, small-signal modulation response characteristics, gain switching characteristics, etc.). Furthermore, the reliability of the simulation results is verified through solving the rate equations. The model of this invention can also be used to analyze and discuss the influence of packaging parasitic parameters on laser output characteristics. For example, by adjusting the corresponding model parameters, the laser output characteristics can be significantly improved, providing a 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, thermionic emission, gateway state, and packaging parasitics, the model can comprehensively and completely reflect the laser's operating characteristics. It can serve as a key foundational model for OEIC design and can also enable optimized laser design.

[0112] References

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[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.

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[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 scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in this invention and are protected by the appended claims.

Claims

1. A method for constructing a multi-parameter SCH-QW semiconductor laser circuit model, characterized in that, The circuit model is constructed based on quantum well effect, package characteristics and gain nonlinear characteristics, and includes construction of an intrinsic network equivalent circuit part and a package parasitic network circuit part; The intrinsic network equivalent circuit part includes an SCH region, a Gateway region, a quantum well QW region and a stimulated radiation region; The Gateway region is respectively provided with an SCH region and Gateway region exchange area and / or Gateway region and QW region exchange area between the SCH region and the Gateway region and / or the quantum well QW region, the SCH region and Gateway region exchange area is used to represent the dynamic transport process of carrier diffusion in the SCH region to the Gateway region and return from the Gateway region to the SCH region, and the Gateway region and QW region exchange area is used to represent the dynamic transport process of carrier capture in the Gateway region by the QW region and carrier excitation in the QW region to the Gateway 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 by means of capture and thermal excitation; The Gateway region serves as a gateway for the SCH region and the QW region to exchange carriers; The stimulated radiation region can generate photons through stimulated radiation and / or spontaneous radiation to emit laser; The intrinsic network equivalent circuit part is constructed based on a three-level rate equation of a semiconductor laser, the three-level rate equation includes carrier concentration rate equations 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 of the SCH region is: The carrier concentration rate equation of the Gateway region is: The carrier concentration rate equation of the quantum well region is: The photon concentration rate equation is: where n i (t) is the contribution of the external injection of SCH carriers; n S , n G and n Q are the carrier concentrations in the SCH, Gateway and QW regions, respectively; S is the photon density; Γ is the optical confinement factor, representing the ratio of the portion of the optical power that propagates within the active layer; υ g is the group velocity; ε S is the photon density dependent gain compression factor, describing the compression of the gain with increasing photon density; τ P is the photon lifetime, related to the intra-cavity losses; τ D is the transport time constant, describing the process of carrier diffusion from the SCH through the double barrier to the Gateway; τ G is the carrier lifetime in the channel state; τ C is the double barrier capture time constant, describing the process of carrier transport from the Gateway to the QW; τ nS is the SCH region carrier lifetime; τ ESC is the carrier escape time; τ nG is the Gateway region carrier lifetime; τ nQ is the QW region carrier lifetime; β is the spontaneous emission coupling factor, representing the ratio of the spontaneous emission of carriers into the lasing mode; g(n Q ) is the carrier dependent material gain; In the carrier dependent material gain g(n Q ) the saturation gain coefficient g s is increased. The improved g(n Q ) is a non-linear representation and is expressed as follows: where g0 is a differential gain, n Q is a carrier concentration of the QW region, n0 is a transparent carrier concentration, g s is an optical gain coefficient when the laser is in a saturated state; The package parasitic network circuit part includes a gold wire, a lumped part and a substrate; the gold wire includes an inductance LB, a resistance RB and a capacitance CB, the lumped part includes a lumped capacitance CS and a lumped resistance RS, and the substrate includes a substrate resistance RSUB; The construction of the package parasitic network circuit part includes three groups of parameters: 1) Gold wire parasitic parameters: series gold wire resistance RB introduced by the inductive property of the gold wire, series gold wire inductance LB introduced by the resistive property of the gold wire and parallel gold wire capacitance CB introduced when the gold wire contacts the chip; 2) Lumped parasitic parameters: parallel lumped capacitance CS from the top metal plating layer to the ridge outer substrate and series lumped resistance RS contributed by the contact, ridge and plating layer; 3) Substrate parasitic parameters: substrate resistance RSUB in series with CS.

2. The construction method of claim 1, wherein, The intrinsic network equivalent circuit model is also increased with the carrier ABC recombination mechanism, and the different recombination processes reflected by the ABC recombination mechanism are replaced by the concentration dependence of the carrier to describe the recombination rate of the carrier. 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 Wherein A is the Shockley-Read-Hall recombination coefficient, B is the spontaneous radiation coefficient, and C is the Auger recombination coefficient.

3. The construction method of claim 2, wherein, The three-level rate equation of the equivalent circuit model is converted into a rate equation of electrical related parameters, Q=nqV is introduced, wherein Q is the charge amount, q is the charge amount of a unit electron, n is the carrier concentration, and V is the volume of the quantum well region, qV is multiplied by both ends of the rate equation, and the relationship between dn / dt and n / t is converted into dQ / dt and Q / t; the relationship between the total number of photons and the output optical power of the laser is introduced: wherein representing the output power value contributed by a single photon, the transformed equation is finally obtained: where I D , I G , I C , I ESC , I STIM , I SPON represents a voltage-controlled current source related to the carrier concentration; I BQ , I CQ represents a voltage-controlled current source related to the spontaneous emission recombination and a voltage-controlled current source related to the Auger recombination; 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 to the SCH; Q S , Q G , Q Q are the charge amounts of the SCH, Gateway, QW regions respectively, which become current variables after divided by the corresponding time constants; the total photon number P is the photon density S multiplied by the volume V of the QW region QW ; ε P is the gain compression factor related to the total photon number, whose value is calculated by ε P = ε S / V QW ; I nS , I nG , I AQ are equivalent to the current flowing through the diode element, and the rest of the current terms are equivalent to the voltage-controlled current sources; among them, the changes of the electric charges of the SCH region, the Gateway region, and the QW region with time are equivalent to the currents flowing through C1, C2, C3; the equation 4. The application method of the circuit model established by any one of claims 1-3 in the simulation and modeling of the influence of saturated nonlinear effect parameters and ABC coefficients on the model output; wherein the saturated nonlinear effect parameters include: Saturation gain coefficient g s Gain compression factor ε P The ABC coefficients include a quantum well laser P-I characteristic, a small signal modulation response characteristic, and a gain switching characteristic.

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