An optical transistor of the nonlinear resonant structure operating with a single frequency light waves and an optical system including the optical transistor

Abstract

The present invention provides a nonlinear resonant structure phototransistor device operating with a single-frequency light wave that simultaneously implements amplification and switching of an optical signal by applying nonlinear optical phenomena and resonant structure technology. Corresponding to electrical control by potential of an electronic transistor, the phototransistor of the present invention is driven by optical control through a nonlinear medium and selective resonance. In the present invention, the second-order nonlinear optical phenomenon is the interaction of sequential second-order harmonic generation and inverse second-order harmonic generation, and the third-order nonlinear optical phenomenon is the interaction of sequential third-order harmonic generation and inverse third-order harmonic generation. When only a pump wave is input to the emitter of the phototransistor, it is in an off state where no output wave exists at the collector; when a pump wave is input to the emitter and a signal wave is input to the base, it becomes an on state where the signal wave is amplified and output at the collector. The input wave at the base controls the input wave at the emitter to regulate the on-off state and intensity of the output wave at the collector. In this manner, the present invention provides a phototransistor operating with a single-frequency light wave and an optical system including the same.

Description

Technology Field

[0001] The present invention relates to optical devices and optical systems, and more specifically, to a nonlinear resonant structure optical transistor operating with a single frequency light wave and an optical system including the same. Background Technology

[0002] In various fields of modern information and communication, optical devices possessing the various advantages of photons are being researched, developed, and replaced as electronic devices. From this perspective, there is a need for optical transistors to replace electronic transistors—the fundamental components that drove innovation in science, technology, and industry during the era of electronic circuits—and to lead innovation in science, technology, and industry during the next-generation era of optical circuits. Considering that electronic transistors provided the cornerstone and foundation for the development of modern science, technology, and industry, it can be expected that optical transistors, corresponding to the functions and roles of electronic transistors, will also provide innovative advancements in next-generation science, technology, and industry.

[0003] An electronic transistor is a device that amplifies and switches electrical signals. Over the past 120 years since the invention of the vacuum tube in 1906, electronic transistors have made rapid advancements, providing the cornerstone and foundation of digital civilization in modern science, technology, and industry. However, the computational speed of current electronic transistor-based computer processors is approximately 3 GHz ( It is approximately Hz, and semiconductor field-effect transistors are known to have an electrical limit of around 100 GHz. By connecting hundreds of thousands or more of these electronic processors in parallel, a peta( Hz) class or exa( It is possible to implement computing systems capable of performing calculations at the Hz level. However, large systems operating at ultra-high speeds in existing electronic circuits, such as supercomputers or data centers, entail problems of massive heat generation and severe power consumption due to the excessive integration of electronic components.

[0004] A phototransistor is a device that amplifies and switches optical signals. Phototransistor processors overcome the limitations of semiconductor field-effect electronic transistors and 1 THz ( Hz) ~ 1PHz( It is expected that ultra-high-speed computation will be possible in the Hz range or even beyond. Furthermore, if hundreds of thousands of phototransistor processors can be connected in parallel, it is expected that an optical computing system capable of performing computations at astronomical speeds, surpassing exascale computation, can be realized. Various configurations using multiple media have long been proposed to invent such phototransistors. However, phototransistors corresponding to the functions and roles of electronic transistors are known to remain undeveloped worldwide.

[0005] Unlike electrons, photons have zero charge, so control by electric potential is impossible. In addition, in classical linear optics, photons do not interact with each other, making it impossible to control other light waves by light waves. Therefore, according to the conventional technology of phototransistors, there is a problem in that it is not possible to simultaneously implement amplification and switching of optical signals corresponding to the functions and roles of electronic transistors. The problem to be solved

[0006] The problem that the present invention aims to solve is to provide a phototransistor capable of simultaneously implementing amplification and switching of an optical signal while operating with a single frequency light wave, and an optical system including the same. means of solving the problem

[0007] The present invention provides a single-frequency-based nonlinear resonant structure phototransistor device and an optical system including the same, which simultaneously implement amplification and switching of an optical signal by applying nonlinear optical phenomena and selective resonant structure technology. In addition, corresponding to electrical control by the potential of an electronic transistor, the nonlinear resonant structure phototransistor of the present invention is driven by optical control by selective resonance.

[0008] First, a nonlinear resonant structure phototransistor device operating with a single-frequency light wave is provided using a second-order nonlinear medium and a selective resonant structure. In the nonlinear resonant structure phototransistor operating with a single-frequency light wave according to the present invention, the second-order nonlinear interaction is sequential second-order harmonic generation and inverse second-order harmonic generation (Cascaded SHG / iSHG).

[0009] Attenuation of the pump wave due to the generation of second harmonics and amplification of the signal wave due to the generation of inverse second harmonics occur in the following two cases. The first is when the signs of the second nonlinear coefficients are opposite. In this case, if the phase difference between the initial values ​​of the pump wave and the signal wave is input as zero, sequential generation of second harmonics and inverse second harmonics by the pump wave and the signal wave, respectively, are possible. The second is when the signs of the second nonlinear coefficients are the same. In this case, the phase difference between the initial values ​​of the pump wave and the signal wave When input as such, sequential second harmonics and inverse second harmonics can be generated by the pump wave and the signal wave, respectively. In addition, the calculation results for sequential second harmonics and inverse second harmonics generation in both cases are consistent.

[0010] Next, a single-frequency based nonlinear resonant structure phototransistor device using a third-order nonlinear medium and a selective resonant structure is provided. In the nonlinear resonant structure phototransistor of the present invention operating with a single-frequency light wave, the third-order nonlinear interaction is sequential third-order harmonic generation and inverse third-order harmonic generation (Cascaded THG / iTHG).

[0011] When only a pump wave is input to the emitter of a phototransistor, the collector is in an off state where no output wave exists; when a pump wave is input to the emitter and a signal wave is input to the base, the collector becomes an on state where the signal wave is amplified and output. The input wave to the base controls the input wave to the emitter to regulate the on-off state and intensity of the output wave at the collector. In this manner, the present invention provides a nonlinear resonant phototransistor that operates with a single-frequency optical wave and implements the amplification and switching of an optical signal, and an optical system including the same.

[0012] A nonlinear resonant structure optical transistor according to embodiments of the present invention comprises: a nonlinear medium that receives a pump wave polarized in a first direction having a first frequency to generate a second harmonic or a third harmonic, receives a signal wave polarized in a second direction intersecting with the first direction having the first frequency, and amplifies the signal wave through an interaction of generating an inverse second harmonic or an inverse third harmonic between the signal wave and the second harmonic or the third harmonic; a first mirror provided on one side of the nonlinear medium, which transmits the pump wave and the signal wave to the nonlinear medium and reflects the second harmonic or the third harmonic; and a second mirror provided on the other side of the nonlinear medium, which transmits the pump wave and the signal wave and reflects the second harmonic or the third harmonic, and can operate at a single frequency.

[0013] According to embodiments of the present invention, in a first operating mode, the pump wave is incident on the nonlinear medium through the first mirror, and in a second operating mode, the pump wave and the signal wave can be incident on the nonlinear medium through the first mirror.

[0014] According to embodiments of the present invention, in the second operation mode, the pump wave and the signal wave may have polarization directions perpendicular to each other.

[0015] According to embodiments of the present invention, in the second operation mode, the pump wave and the signal wave may have the same optical waveguide effective refractive index.

[0016] According to embodiments of the present invention, in the first operating mode, the resonance length of the nonlinear medium is provided as a length at which the intensity of the pump wave output through the second mirror converges to '0', and in the second operating mode, the logic value of the output wave can be determined according to the intensity of the signal wave output through the second mirror.

[0017] According to embodiments of the present invention, in the second operation mode, if the sign of the second nonlinear coefficient or the third nonlinear coefficient determining the attenuation of the pump wave and the amplification of the signal wave is opposite, the pump wave and the signal wave may have a phase difference of 0 between the initial values.

[0018] According to embodiments of the present invention, in the second operating mode, when the sign of the second nonlinear coefficient determining the attenuation of the pump wave and the amplification of the signal wave is the same, the pump wave and the signal wave have a phase difference between the initial values. Can have as.

[0019] According to embodiments of the present invention, in the second operating mode, when the sign of the third nonlinear coefficient determining the attenuation of the pump wave and the amplification of the signal wave is the same, the pump wave and the signal wave may have a phase difference of ±π between the initial values.

[0020] According to embodiments of the present invention, in the second operation mode, the amplified signal wave can be output through the second mirror.

[0021] According to embodiments of the present invention, the first operation mode may correspond to an off state or a logic '0' state mode, and the second operation mode may correspond to an on state or a logic '1' state mode, and an amplification mode that amplifies the signal wave by the second harmonic or third harmonic.

[0022] According to embodiments of the present invention, the logic value of an output wave output from the nonlinear medium can be determined as logic '1' when the intensity of the output wave is stronger than a reference intensity, and as logic '0' when the intensity of the output wave is equal to or weaker than the reference intensity.

[0023] According to embodiments of the present invention, each of the first mirror and the second mirror may include at least one of a dispersion Bragg mirror, a lattice crystal mirror, a dielectric mirror, and an optical mirror.

[0024] According to embodiments of the present invention, the nonlinear medium may include at least one of a crystal, a semiconductor, silica, and a polymer having second-order nonlinearity or third-order nonlinearity.

[0025] An optical system according to embodiments of the present invention comprises: a light source generating a light wave having a first frequency; a beam splitter provided adjacent to the light source and separating the light wave into a pump wave and a signal wave; a first polarizer transmitting the pump wave and polarizing the pump wave in a first direction; a second polarizer transmitting the signal wave and polarizing the signal wave in a second direction; and an optical transistor amplifying the signal wave using the pump wave, wherein the optical transistor comprises: a nonlinear medium that receives the pump wave to generate a second harmonic or a third harmonic, receives the signal wave having the first frequency, and amplifies the signal wave through an interaction of generating an inverse second harmonic or an inverse third harmonic between the signal wave and the second harmonic or the third harmonic; and a first mirror provided on one side of the nonlinear medium, transmitting the pump wave and the signal wave to the nonlinear medium and reflecting the second harmonic or the third harmonic. And it may include a second mirror provided on the other side of the above nonlinear medium, which transmits the pump wave and the signal wave and reflects the second harmonic or third harmonic.

[0026] According to embodiments of the present invention, a control mirror provided between the beam splitter and the second polarizer may be further included.

[0027] According to embodiments of the present invention, the pump wave and the signal wave may have polarization directions perpendicular to each other.

[0028] According to embodiments of the present invention, the first polarizer may include a horizontal polarizer, and the second polarizer may include a vertical polarizer.

[0029] According to embodiments of the present invention, a photodetector provided adjacent to the second mirror and detecting the pump wave and the signal wave may be further included. Effects of the invention

[0030] A nonlinear resonant structure phototransistor according to the concept of the present invention can operate with a single-frequency light wave by utilizing a nonlinear medium between first and second mirrors, and can simultaneously implement amplification and switching of an optical signal. According to the configuration of the present invention, a nonlinear resonant structure phototransistor operating with a single-frequency light wave can be implemented. Therefore, there is an advantage in being able to implement a phototransistor that amplifies and switches an optical signal using a single-frequency light source generated from a single light source. The phototransistor can operate with less energy than conventional electronic transistors and enables ultra-high-speed electro-optical processing. Therefore, if the phototransistor of the present invention is implemented, it can be applied to various technologies such as ultra-high-speed information communication including optical amplification and switching and electro-optical communication, ultra-high-speed optical logic circuits and computing, and optical circuits that drive circuits with light waves. Furthermore, considering the impact that electronic transistors have provided to modern science, technology, and industry, it is expected that the effect provided by the implementation of the phototransistor will also be significant. Brief explanation of the drawing

[0031] FIG. 1 is a representative diagram showing the conceptual structure of a nonlinear resonant optical transistor operating with a single frequency light wave according to an embodiment of the present invention. FIG. 2 is a nonlinear resonant structure operating with a single frequency light wave according to an embodiment of the present invention. This is a diagram showing an example of a phototransistor. Figure 3 is a graph showing the intensity of the pump wave according to the resonance length of the nonlinear medium of Figure 2. Figure 4 is a graph showing the intensity of the resonant second harmonic according to the resonance length of the nonlinear medium of Figure 2. FIG. 5 is a diagram showing an example of a phototransistor with a nonlinear resonant structure operating with a single frequency light wave according to an embodiment of the present invention. Figure 6 is a graph showing the intensity of the pump wave and signal wave propagating through the optical waveguide of the nonlinear medium of Figure 5. FIG. 7 is a diagram showing an example of a method for distinguishing on-off states according to switching operation in a nonlinear resonant structure phototransistor operating with a single frequency light wave according to an embodiment of the present invention. Figure 8 is a graph showing an example of the phototransistor intensity transition rate with respect to the change in intensity of the signal wave provided to the first mirror of Figure 5. Figure 9 is a graph showing an example of the phototransistor strength amplification rate for a change in signal wave strength provided to the first mirror of Figure 5. Figure 10 is a graph showing an example of the phototransistor dB scale intensity amplification rate for a change in signal wave intensity provided to the first mirror of Figure 5. FIGS. 11 and FIGS. 12 are drawings showing an example of an optical system according to the concept of the present invention. Specific details for implementing the invention

[0032] As a technical means to solve the aforementioned problems, the present invention provides a single-frequency-based nonlinear resonant structure optical transistor and an optical system device including the same, which simultaneously implement amplification and switching of an optical signal by applying nonlinear optical phenomena and selective resonant structure technology. A nonlinear resonant structure is a structure in which a nonlinear medium exists within the resonant structure, allowing nonlinear interaction and resonance of light waves to proceed simultaneously. Selective resonance is a resonance caused by selective reflection and transmission in which a mirror forming the resonant structure reflects light waves of a specific frequency and transmits light waves of other frequencies.

[0033] An optical transistor is a device that amplifies and switches optical signals using light waves. Optical interaction between light waves is required for the amplification and switching of optical signals by light waves. As with electronic transistors, for the amplification and switching functions of an optical transistor, the input wave at the base must control the input wave at the emitter to regulate the output wave at the collector. In this process, the on / off state and intensity of the collector output wave are controlled. However, in classical linear optics, light waves do not undergo optical interaction, so a medium is required to induce optical interaction between the light waves.

[0034] The key issues in implementing a phototransistor corresponding to an electronic transistor can be briefly explained as follows. While electrons can be electrically controlled by electric potential, photons have zero charge and therefore cannot be controlled by electric potential. Furthermore, in classical linear optics, there is no electromagnetic interaction between photons, making it impossible to control other light waves by one light wave. To solve these technical problems, the present invention utilizes a nonlinear medium and a selective resonance structure to cause light waves to interact and to control another light wave through one light wave. The present invention provides a phototransistor that implements amplification and switching operations through such optical interaction and control.

[0035] First, the case of a single-frequency-based nonlinear resonant structure optotransistor using a second-order nonlinear medium and a selective resonant structure is described. When a pump wave is input to the emitter (E) of the nonlinear resonant structure optotransistor, a second harmonic generating interaction is induced by the second-order nonlinear medium. The second harmonic wave generated at this time resonates within the resonant structure. Next, when a signal wave is input to the base (B), the signal wave is amplified through an inverse second harmonic generating interaction with the resonating second harmonic wave. The amplified signal wave is output through the collector (C). The on / off state and intensity of the signal wave output from the collector are controlled by the base signal wave.

[0036] In an electronic transistor, the currents of the emitter, base, and collector correspond equally to the light waves of the emitter, base, and collector, respectively, in a phototransistor. In a phototransistor, the light waves of the emitter, base, and collector are the pump wave, the signal wave, and the idler wave, respectively. In an electronic transistor, electrical amplification and switching are achieved by the currents of the emitter, base, and collector, while in a phototransistor, optical amplification and switching are achieved by the pump wave of the emitter, the signal wave of the base, and the idler wave of the collector. Furthermore, corresponding to the electrical control by the potential of an electronic transistor, the nonlinear resonant structure phototransistor of the present invention is driven by optical control through selective resonance.

[0037] In the single-frequency-based nonlinear resonant structure phototransistor of the present invention, the second-order nonlinear interactions are sequential second-order harmonic generation and inverse second-order harmonic generation. The sequential second-order harmonic generation and inverse second-order harmonic generation are briefly explained as follows.

[0038] First, by inputting only the pump wave to the emitter and adjusting the intensity, the resonance length at which the entire pump wave generates a second harmonic can be determined. That is, inputting only the pump wave first generates a second harmonic, and subsequent input pump waves interact with the resonating second harmonic due to the resonant feedback condition. When the pump wave interacts with the resonating second harmonic due to the resonant feedback condition, the entire pump wave can be used to generate the second harmonic and thus exhausted. At this point, the generated second harmonic, preferably if resonated with a mirror with 100% reflectivity, cannot be output externally. In other words, all generated second harmonics completely resonate internally and increase in intensity. Consequently, since the pump wave is exhausted and the second harmonic resonates internally within the resonant structure, the intensity of the light wave output from the collector in this case is zero (off state).

[0039] Next, when a signal wave is sequentially input to the base, an idler wave is output from the collector through the interaction of generating a resonant second harmonic and an inverse second harmonic. In the single-frequency-based nonlinear resonant structure phototransistor of the present invention, the idler wave output from the collector is an amplified signal wave. Therefore, the wavelengths of the pump wave, the signal wave, and the idler wave are identical. The intensity of the idler wave, which is the amplified signal wave, is not zero and can be defined as 1 in the ON state. In this way, the present invention provides a phototransistor device that implements amplification and switching.

[0040] Meanwhile, the selective resonance structure transmits the pump wave, signal wave, and idler wave, but resonates with the second harmonic of the pump wave so that it is not transmitted to the outside at all. In this case, the second harmonic resonates while reciprocating or circulating internally. The resonance structure for this purpose is not particularly limited and can include all forms. For example, it can be configured in various ways, such as two reflective mirrors, a distributed Bragg reflector (DBR), a lattice crystal mirror formed by the nonlinear medium itself, or a ring cavity.

[0041] The above objectives, other objectives, features, and advantages of the present invention will be easily understood through the following preferred embodiments associated with the accompanying drawings. However, the following embodiments are provided to enable those skilled in the art to fully understand the present invention. The following embodiments may be modified in various forms, and the scope of the present invention is not limited to the embodiments described below. Hereinafter, in order to understand the technical concept of the present invention and to facilitate its implementation, embodiments of the present invention will be described with reference to the accompanying drawings.

[0042] FIG. 1 is a representative diagram showing the conceptual structure of a phototransistor (100) of a nonlinear resonant structure operating with a single frequency light wave according to an embodiment of the present invention. Referring to FIG. 1, the phototransistor (100) of a nonlinear resonant structure operating with a single frequency light wave according to the present invention may include a nonlinear resonant structure. The emitter, base, and collector of the phototransistor (100) are defined by a second nonlinear medium and a resonant structure constituting the nonlinear resonant structure. When a pump wave (102) is input at the emitter and a signal wave (104) is input at the base, an amplified signal wave (104) is output at the collector.

[0043] In a phototransistor (100) composed of a second-order nonlinear medium and a nonlinear resonant structure, the pump wave (102) and the signal wave (104) interact through the phenomena of sequential second-order harmonic generation and inverse second-order harmonic generation. At this time, the frequency of the pump wave (102) and the frequency of the signal wave (104) It must be identical to mathematical formula 1.

[0044]

[0045] And the polarization of the pump wave (102). and polarization of the signal wave (104) The direction is the direction of light wave transmission. It is perpendicular, and the polarizations of the two light waves must be mutually perpendicular and orthogonal as shown in Equation 2.

[0046]

[0047] The pump wave (102) and the signal wave (104) can be considered physically independent light waves because they have the same frequency but mutually perpendicular polarizations. Here, for the convenience of explanation, the frequency of the light wave is the angular frequency. =2π , polarization is a unit vector It is written as .

[0048] Pump wave (102) and signal wave (104) having the same frequency must each simultaneously satisfy the resonant second harmonic propagating in the same direction and the phase matching condition. The pump wave (102) performs a second harmonic generation interaction with the resonant second harmonic, and the signal wave (104) performs an inverse second harmonic generation interaction with the resonant second harmonic. At this time, the generation of second harmonics and the generation of inverse second harmonics are each included in the Type-I second harmonic generation interaction. To do so, the effective refractive index of the pump wave (102) and the signal wave (104) ( , ) must be identical to mathematical formula 3.

[0049]

[0050] This condition is an essential requirement for a second-order nonlinear medium optical waveguide through which light waves propagate, for the second-order nonlinear optical phenomena occurring in the phototransistor of the present invention. That is, the effective refractive indices of two light waves having mutually perpendicular polarization and propagating at a single frequency must be the same.

[0051] Meanwhile, in the process of generating Type-I second harmonics and Type-I inverse second harmonics, it is assumed that there is no interaction by direct coupling, such as Type-II second harmonic generation, between the Type-I second harmonic, pump wave (102), and signal wave (104). To explain more specifically with an example, the pump wave (102) and the signal wave (104) have a second nonlinear coefficient and If each participates in the sequential generation of Type-I second harmonics and the generation of inverse second harmonics, This means that there is no interaction between the three light waves through direct coupling. However, the pump wave (102) and the signal wave (104) , It participates in the sequential generation of Type-I second harmonics and inverse second harmonics by, but simultaneously Through this, it is possible to participate in the generation of Type-II second harmonics. This will be explained in more detail later.

[0052] The optical phenomena of sequential second harmonic generation and inverse second harmonic generation are described in more detail as follows. The pump wave (102) and the signal wave (104) have mutually perpendicular polarizations and propagate in the same transmission direction. These pump wave (102) and the signal wave (104) each undergo a second nonlinear interaction with a second harmonic that propagates in the same direction among the resonating second harmonics. That is, a second harmonic having a single frequency and polarization undergoes second harmonic generation with the pump wave (102) and inverse second harmonic generation with the signal wave (104). In the optical phenomenon of second harmonic generation, second harmonic generation or inverse second harmonic generation is determined by the second nonlinear coefficient and the initial phase state of the input light wave, such as the pump wave (102) or the signal wave (104). The specific role of the initial phase state in second harmonic generation or inverse second harmonic generation will be described in more detail in Fig. 6, which will be explained later.

[0053] The process of generating a Type-I second harmonic and a Type-I inverse second harmonic is as follows, from the perspective of the nonlinear resonant structure phototransistor (100) of the present invention. First, when a pump wave (102) is input to the emitter, a second harmonic of the pump wave (102) is generated as shown in Equation 4 through the phenomenon of generating a Type-I second harmonic of the pump wave (102).

[0054]

[0055] The generated second harmonic cannot penetrate to the outside of the resonant structure but resonates internally and increases in intensity. The polarization direction of the second harmonic is also the light wave transmission direction. It is perpendicular to and in the polarization direction of the pump wave (102) ( = ) or signal wave (104) polarization direction ( = )am.

[0056] When a signal wave (104) is input to the base sequentially, the signal wave (104) is amplified as in Equation 5 by the Type-I inverse second harmonic generation phenomenon between the signal wave (104) and the resonant second harmonic wave.

[0057]

[0058] According to mathematical formula 5, the signal wave (104) is amplified and output through the collector. That is, when the pump wave (102) is input at the emitter and the signal wave (104) is input at the base, the signal wave (104) is output at the collector. At this time, amplification and switching are implemented by the on-off operation of the signal wave (104) output at the collector according to the on-off operation of the signal wave (104) input at the base. The specific roles of the resonant structure and the second-order nonlinear medium in amplification and switching will be described in more detail in FIGS. 2 and FIGS. 5, which will be explained later.

[0059] FIG. 2 is a nonlinear resonant structure operating with a single frequency light wave according to an embodiment of the present invention. This is a drawing showing an example of a phototransistor (100). Referring to FIG. 2, the phototransistor (100) of the nonlinear resonant structure operating with a single frequency light wave of the present invention can output information data of an off state 0. According to one example, the phototransistor (100) of the nonlinear resonant structure of the present invention may include a nonlinear medium (110), a first mirror (120), and a second mirror (130).

[0060] The nonlinear medium (110) may be located on the same path as the light waves propagate. The nonlinear medium (110) is a material in which secondary nonlinearity is inherently present, such as a crystal, semiconductor, silica, or polymer, or in which secondary nonlinearity can be induced by polarization, etc. That is, the nonlinear medium (110) may be a secondary nonlinear medium. The nonlinear medium (110) may be in the form of an optical waveguide to reduce light wave propagation loss and improve the efficiency of secondary nonlinear interactions. The nonlinear medium (110) satisfies the phase matching condition required for the mixed light waves. In an embodiment of the present invention, the nonlinear medium (110) may have a resonance length (L) to form a resonance structure. For convenience of explanation in FIG. 2, the resonance length and the length of the nonlinear medium (110) may be the same, and the present invention is not limited thereto.

[0061] The off-state configuration is described in more detail as follows. A first mirror (120) may be provided on one side of a nonlinear medium (110) into which a pump wave (102) from the emitter or a signal wave (104) from the base is incident. A second mirror (130) may be provided on the other side of the nonlinear medium (110) into which a pump wave (102) or a signal wave (104) is output from the collector. The second mirror (130) may be parallel to the first mirror (120). Each of the first mirror (120) and the second mirror (130) transmits the pump wave (102) or the signal wave (104). On the other hand, each of the first mirror (120) and the second mirror (130) may reflect the second harmonic of the pump wave (102).

[0062] A pump wave (102) is incident on a first mirror (120), and the incident pump wave (102) can generate a second harmonic by a nonlinear medium (110) inside a resonant structure. The generated second harmonic can be selectively reflected by the first mirror (120) and the second mirror (130) arranged facing each other and parallel. Then, the second harmonic of the pump wave (102) can form a resonant wave by the first mirror (120) and the second mirror (130). Preferably, the reflectance of the first mirror (120) and the second mirror (130) for the resonating second harmonic is 100%. When the reflectance is 100%, the first mirror (120) and the second mirror (130) can form a complete internal resonant structure for the second harmonic. In this case, the resonant second harmonic is not output at all outside the first mirror (120) and the second mirror (130). That is, the resonant second harmonic is not output at all outside the phototransistor (100) of the nonlinear resonant structure of the present invention.

[0063] Meanwhile, the pump wave (102) that did not participate in the generation of a second harmonic in the optical transistor (100) of the nonlinear resonant structure of the present invention can be transmitted to the side of the second mirror (130) and output. However, if the resonance length of the nonlinear medium (110) is appropriately set with respect to the intensity of the input pump wave (102), the output of the pump wave (102) converges to '0'. This is because if the pump wave (102) interacts with the second harmonic that resonates due to the resonance feedback condition, the entire pump wave (102) can be used to generate the second harmonic and be exhausted. Alternatively, in the opposite case, the intensity of the input pump wave (102) can be appropriately set with respect to the resonance length of the nonlinear medium (110). In either case, the pump wave (102) can be completely exhausted inside the resonant structure due to the conversion to a second harmonic and the transmission loss of the nonlinear medium (110).

[0064] Accordingly, the nonlinear resonant structure of the present invention operating with a single frequency light wave The phototransistor (100) can make the output of the pump wave (102) transmitted to the side of the second mirror (130) of the resonant structure into a '0' state. Consequently, when only the pump wave (102) is input to the emitter, the output of the pump wave (102) at the collector can be made into an off state of '0', and since the second harmonic is not output externally at all, the off state can be implemented according to the configuration of FIG. 2.

[0065] The first mirror (120) and the second mirror (130) for forming a resonant structure can be implemented in various ways. Preferably, the first mirror (120) and the second mirror (130) need to be able to withstand second harmonics resonating with strong intensity. In one embodiment, the first mirror (120) and the second mirror (130) can be implemented as semiconductor dispersed Bragg mirrors formed on both sides of the nonlinear medium (110). In another embodiment, the first mirror (120) and the second mirror (130) can be implemented as lattice crystal mirrors formed by the nonlinear medium (110) itself on both sides of the nonlinear medium (110). In yet another embodiment, the first mirror (120) and the second mirror (130) may be implemented as dielectric mirrors formed on both sides of the nonlinear medium (110). Here, it will be well understood that the nonlinear medium (110) forming the resonant structure and the first mirror (120) and second mirror (130) formed on both sides thereof can be implemented in various ways or modified.

[0066] FIG. 3 is a graph showing the intensity of the pump wave (102) according to the resonance length of the nonlinear medium (110) of FIG. 2. The horizontal axis is the resonance length, and the vertical axis is the intensity of the pump wave (102) output from the collector. Referring to FIG. 3, the pump wave (102) may have an intensity that tends to decrease as the resonance length increases.

[0067] The pump wave (102) provided within the nonlinear medium (110) through the first mirror (120) is =10mW / It can have a strength. The strength of the pump wave (102) output through the second mirror (130) is It was indicated by . The resonance lengths are 0.5 cm, 1 cm, 2 cm, 3 cm, 4 cm, and 5 cm. The points on the graph represent the second-order nonlinear coefficients dil = 3 pm / V, 7 pm / V, 10 pm / V, 15 pm / V, 30 pm / V and the transmission loss coefficient These are simulation data calculated for the cases of =0.3, 0.03, and 0.003 dB / cm. These simulation data points are displayed by connecting points with the same second-order nonlinear coefficient and transmission loss coefficient with a smooth curve.

[0068] The effective second-order nonlinear coefficient d in the simulation of the off-state configuration of Fig. 3 or in the simulation calculations described later eff It can be equal to mathematical formula 6.

[0069]

[0070] Here is a valid argument by quasi-phase matching, = / 2 is the second-order nonlinear coefficient, is the Effective Mode Factor of a Wave. In waveguide modes, the Effective Mode Factor is generally 0 ≤ ≤1. In the simulation of the present invention, the light waves participating in the nonlinear interaction are A plane wave mode with =1 was used. In the calculation of nonlinear equations describing the interaction of light waves, there is no significant physical difference between plane wave modes and optical waveguide modes, and qualitatively ( Qualitatively ) are equivalent.

[0071] In a resonant structure, the resonant wave and single-pass light waves mix together and interact nonlinearly. If the number of resonance cycles n of the resonant wave is introduced into the nonlinear equation describing the nonlinear interaction of the single-pass light waves, theoretically, the interaction between the resonant wave and the single-pass light waves can be described by the nonlinear equation of the single-pass light waves. That is, the interaction between the resonating second harmonic wave and the input pump wave (102) or signal wave (104) can be simplified to the interaction between the single-pass second harmonic wave and the pump wave (102) or the second harmonic wave and the signal wave (104) at the resonance cycle number n stage. In FIG. 3, the intensity of the pump wave (102) and the second harmonic wave converges to a constant value and saturates at a resonance cycle number n=100 due to the balance between the second nonlinear interaction and the transmission loss. Of course, it will be well understood that the number of resonances n = 100 is merely an exemplary number representing the saturation state of the corresponding light wave due to resonance.

[0072] Now, in the phototransistor (100) of the nonlinear resonant structure of the present invention, we examine a curve representing the intensity Ip100(L) of the pump wave (102) output from the collector according to the resonance length. In FIG. 3, the same second-order nonlinear coefficient is the same data symbol, and the same transmission loss coefficient is from top to bottom within the same symbol. It represents =0.3, 0.03, and 0.003 dB / cm. Near a short resonance length L = 0.5 cm to 1 cm, the output collector intensity is Ip100(L) ≈ 0 to 10 mW / It is distributed generally around (=Ip100(0)). As the resonance length L increases, the collector intensity Ip100(L) decreases sharply overall due to the influence of second harmonic generation interactions and transmission losses. If the second nonlinear coefficient increases, the efficiency of second harmonic generation interactions increases, resulting in Ip100(L) ~ 0mW / in the off state at short resonance lengths. We show that it is possible to implement this. If the second-order nonlinear coefficient is small, the second-order harmonic generation efficiency is low, so Ip100(L) ~ 0mW / in the off state at long resonance lengths It shows that it is possible to implement.

[0073] Let's look at the change in collector strength Ip100 (z=L) with respect to the change in transmission loss. Near L=0.5cm ~ 1cm At dB / cm As it decreases in dB / cm, Ip100(L) decreases significantly overall. However, At dB / cm When reduced by dB / cm, the decrease in Ip100(L) is relatively small. The intensity of the pump wave (102) Ip100(0) input from the emitter is converted into a second harmonic by a second harmonic generating interaction, thereby implementing an off state at the collector where Ip100(L)=0. In implementing the off state, a high second-order nonlinear coefficient and a strong intensity resonant second harmonic are essential for the strong conversion of the pump wave (102) Ip100(0) input from the emitter. If the second-order nonlinear coefficient is approximately dil=3pm / V or 7pm / V, the transmission loss is required to implement the off state near L=0.5cm to 1cm. This suggests that it is important to lower it below dB / cm. In addition, if the second-order nonlinear coefficient dil is approximately 30 pm / V At 0.03dB / cm, L=1cm, It suggests that an off state can be implemented at L=0.5cm at 0.003dB / cm.

[0074] The second-order nonlinear coefficient is large, around dil=30pm / V, and the transmission loss is In the curve, which is small at approximately 0.003 dB / cm, it increases sharply after Ip100(L) L=2 cm. This is because, as explained later in Figure 4, the second-order nonlinear coefficient is large at approximately dil=30 pm / V and the transmission loss is This contrasts with the fact that the second harmonic intensity Ih100(L) decreases sharply after L=2cm on a curve as small as approximately 0.003dB / cm. This is the intensity exchange oscillation, which is well known in the phenomenon of second harmonic generation. Intensity exchange oscillation occurs at the solution (here Ip100(z), Ih100(z)) of the second nonlinear equation for nonzero initial values ​​(here Ip100(0), Ih100(0)).

[0075] FIG. 4 is a graph showing the intensity of the resonant second harmonic according to the resonance length of the nonlinear medium (110) of FIG. 2. Referring to FIG. 4, the intensity of the resonant second harmonic tends to decrease as the resonance length increases and can be distributed according to the second nonlinear coefficient and the transmission loss coefficient. The data points for the resonant second harmonic intensity Ih100(L) are the results calculated under the same conditions as those of FIG. 3. These simulation data are displayed by connecting points with the same second nonlinear coefficient and transmission loss coefficient with a smooth curve.

[0076] Now, we examine the curve representing the resonant second harmonic intensity Ih100(L) according to the resonance length of the phototransistor (100) of the nonlinear resonant structure of the present invention. In FIG. 4, the same second nonlinear coefficient is represented by the same data symbol, and the same transmission loss coefficient is represented from top to bottom within the same symbol. It represents =0.3, 0.03, and 0.003 dB / cm. Near a short resonance length L = 0.5 cm to 1 cm, the resonance second harmonic intensity is Ih100(L) ≈ 0 to 900 mW / It is widely distributed to that extent. As the resonance length L increases, the intensity of the resonance second harmonic is particularly decisively affected by propagation loss. The propagation loss coefficient In the case of dB / cm, Ih100(L) decreases, In the case of dB / cm, Ih100(L) decreases or increases and then decreases. In the case of dB / cm, Ih100(L) increases and then decreases. If the second nonlinear coefficient is large, the second harmonic generation interaction efficiency is high, making it possible to achieve a strong resonant second harmonic intensity Ih100(L) at a short resonance length. If the second nonlinear coefficient is small, the resonant second harmonic intensity is relatively weak.

[0077] Let's examine the change in the resonant second harmonic intensity Ih100(L) with respect to the change in transmission loss. Near L = 0.5 cm to 1 cm At dB / cm As it decreases in dB / cm, Ih100(L) generally increases significantly. Also At dB / cm As it decreases in dB / cm, Ih100(L) increases significantly. At a relatively long resonance length, the intensity of the resonance second harmonic is the transmission loss coefficient independent of the second nonlinear coefficient. They form groups with identical ones and converge near a constant resonant second harmonic intensity for each. Each converging resonant second harmonic intensity is In the case of dB / cm, Ih100(L) ~ 10mW / , In the case of dB / cm, Ih100(L) ~ 150mW / A relatively low value to that extent, or In the case of dB / cm, Ih100(L) ~ 700mW / It is a relatively very high value. This is the optical waveguide transmission loss of a nonlinear resonant structure phototransistor. This means that it is important to lower it to near dB / cm.

[0078] The second-order nonlinear coefficient is large, around dil=30pm / V, and the transmission loss is In the curve with a small value of approximately 0.003 dB / cm, the intensity of the resonant second harmonic decreases sharply after L=2 cm. This is because, as seen in Figure 3, the second nonlinear coefficient is large at approximately dil=30 pm / V and the transmission loss is This contrasts with the point where the pump wave (102) intensity Ip100(L) increases rapidly after L=2cm in a curve of about 0.003dB / cm. This is a well-known intensity exchange oscillation between the solutions Ip100(z) and Ih100(z) of the second-order nonlinear equation for non-zero initial values ​​Ip100(0) and Ih100(0).

[0079] In the simulation results of Figures 3 and 4 regarding the off-state configuration of Figure 2 above, it can be seen that when the intensity of the pump wave (102) input to the emitter and the resonance length by the nonlinear medium (110) are adjusted in the phototransistor (100) of the nonlinear resonant structure operating with a single frequency light wave of the present invention, the intensity of the light wave output to the collector can be off-state '0'.

[0080] FIG. 5 is a diagram showing an example of a nonlinear resonant optical transistor (100) operating with a single frequency light wave according to an embodiment of the present invention. Here, FIG. 5 is a schematic diagram, and a pump wave (102) and a signal wave (104) separated in two directions from a light source (200) can be combined again (not shown) and input on the same line. Referring to FIG. 5, the nonlinear resonant optical transistor (100) operating with a single frequency light wave according to the present invention can output information data in an ON state 1. The nonlinear medium (110), the first mirror (120), and the second mirror (130) can be configured in the same way as in FIG. 2.

[0081] Hereinafter, the method for outputting information data in the ON state 1 of the optical transistor (100) of the nonlinear resonant structure operating with a single frequency light wave according to the present invention is described as follows. The pump wave (102) of the emitter and the signal wave (104) of the base are input to one side of the first mirror (120). At this time, the frequencies of the pump wave (102) and the signal wave (104) are the same, and their polarization directions are perpendicular to each other. Then, the pump wave (102) and the signal wave (104) can be transmitted and output to one side of the second mirror (130) formed on the other side of the nonlinear medium (110). The pump wave (102) or the signal wave (104) is input to the side of the first mirror (120) either directly from a light source (e.g., a laser diode) or induced through an optical fiber. Likewise, a pump wave (102) or signal wave (104) transmitted from the interior of the non-linear medium (110) to one side of the second mirror (130) can also be output directly or induced into an optical fiber.

[0082] The ON state configuration is examined in more detail as follows. A pump wave (102) of relatively strong intensity is first input to the side emitter of the first mirror (120). Then, as described in FIG. 2, the pump wave (102) is attenuated by a second harmonic generating interaction. The generated second harmonic undergoes complete internal resonance and increases in strength. At this time, a signal wave (104) of relatively weak intensity is input to the side base of the first mirror (120). Then, the signal wave (104) is amplified by a resonant second harmonic and an inverse second harmonic generating interaction. The amplified signal wave (104) is output to the side collector of the second mirror (130). In conclusion, when the pump wave (102) is input to the emitter and the signal wave (104) is input to the base, the signal wave (104) is amplified, and the signal wave (104) output of the collector can be made to a state of '1', thus enabling the ON state to be implemented according to the configuration of FIG. 5.

[0083] FIG. 6 is a graph showing the intensity of a pump wave (102) and a signal wave (104) as they travel along the optical waveguide of the nonlinear medium (110) of FIG. 5. Referring to FIG. 6, the intensity of the pump wave (102) decreases as it travels along the optical waveguide of the nonlinear medium (110), and the intensity of the signal wave (104) may increase as it travels along the optical waveguide.

[0084] Pump wave (102) =10mW / The signal wave (104) has an initial intensity and can be provided within the first mirror (120) and the nonlinear medium (110). =1mW / It has an initial intensity and can be provided within the first mirror (120) and the nonlinear medium (110). The horizontal axis optical waveguide coordinates of the graph are the optical wave transmission direction z (0 ≤ z ≤ L) coordinates in the laboratory coordinate system (Lab Frame) of the optical waveguide forming the nonlinear resonant structure. The intensity of the pump wave and signal wave (104) output from the second mirror (130) is Ip,s(z) (mW / It was indicated as ). The graphs in Fig. 6 are second-order nonlinear coefficients =7pm / V, transmission loss This is the simulation result under conditions of =0.03dB / cm, resonance length L=3cm, and resonance cycle n=100. For the convenience of the simulation below, it is assumed that the signal wave (104) is input together with the pump wave (102).

[0085] Referring to FIG. 6, in an optical waveguide with a resonant length L=3cm, the pump wave (102) intensity at z=0 is 10mW / And the signal wave (104) intensity is 1mW / The initial value of was input. The pump wave (102) input to the emitter is attenuated by the generation of a second harmonic as it travels from z=0 to the resonance length z=L=3cm, and the signal wave (104) input to the base is amplified by the generation of an inverse second harmonic. In FIG. 6, the strength of the signal wave (104) output from the collector is 7.68mW / is. Under the simulation conditions of the graph in Fig. 6, the intensity transition rate of the phototransistor is = is approximately 0.768, and the intensity amplification rate is = approximately 7.68. The intensity transition rate and intensity amplification rate of the phototransistor will be explained in more detail in Figures 8 and 9, which will be described later.

[0086] For convenience of explanation and understanding, the second harmonic generating interaction second nonlinear coefficient of the pump wave (102) , the second harmonic generation interaction second nonlinear coefficient of the signal wave (104) Let's assume that. Here is a second-order nonlinear coefficient tensor, and X, Y, and Z are the principal coordinate axes of the crystal frame. Then the pump wave (102) is By means of X-axis polarization, the signal wave (104) is By means of Y-axis polarization, the Y-axis polarization of the second harmonic is combined with the Y-axis polarization of the second harmonic. If the two light waves satisfy the phase matching condition for generating a second harmonic, the pump wave (102) can participate in the Type-I second harmonic generation and the signal wave (104) can participate in the Type-I inverse second harmonic generation interaction.

[0087] The attenuation of the pump wave (102) by the generation of a second harmonic and the amplification of the signal wave (104) by the generation of an inverse second harmonic occur in the following two cases. The first is This is the case where the signs of the second-order nonlinear coefficients are opposite. This also applies to cases including the case where sequential second harmonics and inverse second harmonics can be generated by the pump wave (102) and the signal wave (104), respectively. To this end, the phase difference of the electric field amplitudes of the pump wave (102) and the signal wave (104) must be initially input as 0 at z=0. Here, z is the z-coordinate of the laboratory coordinate system. In the graph simulation of FIG. 6, the pump wave (102) is 10mW / , and the signal wave (104) 1mW / =1mW / The initial value of the century was entered.

[0088] The second one is This is the case where the signs of the second-order nonlinear coefficients are the same. This also applies to cases including the case where the pump wave (102) and the signal wave (104) can generate sequential second harmonics and inverse second harmonics, respectively. To this end, the phase difference between the electric field amplitudes of the pump wave (102) and the signal wave (104) is at z=0 It must be initially input as follows. The pump wave (102) is 10mW / , and the signal wave (104) 1mW / = (±i)1mW / When an initial value of the intensity is input, a graph identical to the simulation graph in Fig. 6 can be obtained. In other words, the calculation results in the two cases match perfectly.

[0089] FIG. 7 is a diagram showing an example of a method for distinguishing on-off states according to switching operation in a nonlinear resonant structure phototransistor (100) operating with a single frequency light wave according to an embodiment of the present invention. Referring to FIG. 7, the operating state ('On' or 'Off') or the logic state ('0' or '1') of the nonlinear resonant structure phototransistor (100) can be determined depending on whether a light wave output from the collector is present.

[0090] To determine the logic value of the signal wave (104) output from the collector on the second mirror (130) side, the strength of the signal wave (104) can be compared with a reference value. If the strength of the signal wave (104) is weaker than the reference value, the operation of the non-linear resonant optical transistor (100) operating at a single frequency can be determined to be off. Alternatively, the logic value of the signal wave (104) can be determined to be logic '0'. On the other hand, if the strength of the signal wave (104) is stronger than the reference value, the operation of the non-linear resonant optical transistor (100) operating at a single frequency can be determined to be on. Alternatively, the logic value of the output signal wave (104) can be determined to be logic '1'. In conclusion, when a pump wave (102) is input to the emitter, the signal wave (104) output from the collector can be made to a state of '0' or '1' depending on whether a signal wave (104) is input to the base, so on-off switching can be implemented by the distinction method of FIG. 7.

[0091] Similar to the case of the Current Transfer Ratio of an electronic transistor, the Intensity Transfer Ratio of a phototransistor It can be equal to mathematical formula 7.

[0092]

[0093] That is, the intensity transition rate of the phototransistor can be defined as the ratio of the intensity of the signal wave (104) output from the collector to the intensity of the pump wave (102) input to the emitter.

[0094] FIG. 8 is a graph showing an example of the phototransistor intensity transition rate for changes in the intensity of the signal wave (104) provided to the first mirror (120) of FIG. 5. The intensity transition rate simulation data of FIG. 8 are results calculated by the definition of the intensity transition rate of the phototransistor from various simulation results that can represent an on state '1' as in FIG. 6. The data points of FIG. 8 represent the intensity of the pump wave (102) to the emitter through the first mirror (120). =10mW / , signal wave (104) intensity at the base 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0mW / When input, the strength of the signal wave (104) output from the collector through the second mirror (130) It was calculated from. These points are second-order nonlinear coefficients =7pm / V, transmission loss factor This is simulation data calculated for the cases of = 0.3, 0.03, and 0.003 dB / cm. Points with the same transmission loss coefficient can be connected by a smooth curve. In Fig. 8, identical data symbols correspond to identical second-order nonlinear coefficients, and identical transmission loss coefficients correspond to the same symbol from bottom to top. = represents 0.3, 0.03, and 0.003 dB / cm.

[0095] Referring to Fig. 8, A nonlinear medium (110) having a transmission loss factor of =0.003dB / cm can have an excellent intensity transition rate. The transmission loss factor When =0.3dB / cm, the change in bass intensity is 0 ~ 1.0mW / For the interval, the intensity transition rate increases almost linearly between 0 and 0.2. The transmission loss coefficient is When =0.03 dB / cm, base intensity change 0 ~ 1.0mW / For the interval, the intensity transition rate increases strongly and reaches about 0.7. The transmission loss coefficient is When =0.003 dB / cm, base intensity change 0 ~ 0.2mW / In the interval, the intensity transition rate increases rapidly to about 0.9 and then saturates near 1 in the subsequent interval. These results indicate that in order to increase the intensity transition rate of the nonlinear resonant structure phototransistor of the present invention, it is important to lower the transmission loss.

[0096] Similar to the case of the Current Amplification Factor of an electronic transistor, the Intensity Amplification Factor of a phototransistor It can be equal to mathematical formula 8.

[0097]

[0098] That is, the intensity amplification rate of the phototransistor can be defined as the ratio of the intensity of the signal wave (104) output from the collector to the intensity of the signal wave (104) input to the base.

[0099] FIG. 9 is a graph showing an example of the phototransistor intensity amplification rate for changes in the intensity of the signal wave (104) provided to the first mirror (120) of FIG. 5. The intensity amplification rate simulation data of FIG. 9 are results calculated by the definition of the intensity amplification rate of the phototransistor from various simulation results that can represent the digital 'on' '1' state in FIG. 6. The data points of FIG. 9 represent the pump wave (102) intensity to the emitter through the first mirror (120). =10mW / , signal wave (104) intensity at the base 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0mW / When input, the strength of the signal wave (104) output from the collector through the second mirror (130) It was calculated from. These points are second-order nonlinear coefficients =7pm / V, transmission loss factor This is simulation data calculated for the cases of = 0.3, 0.03, and 0.003 dB / cm. Points with the same transmission loss coefficient can be connected by a smooth curve. In Fig. 9, identical data symbols correspond to identical second-order nonlinear coefficients, and identical transmission loss coefficients correspond to the same symbol from bottom to top. = represents 0.3, 0.03, and 0.003 dB / cm.

[0100] Referring to Fig. 9, A nonlinear medium (110) having a transmission loss factor of =0.003 dB / cm can have an excellent intensity amplification rate. The transmission loss factor When =0.3dB / cm or 0.03dB / cm, the change in base intensity is 0 to 1.0mW / For the interval, the intensity amplification rate is nearly constant or decreases slightly. The transmission loss coefficient is When =0.003dB / cm, base intensity change 0 ~ 0.2mW / In the range, the intensity amplification rate decreases sharply at approximately 3,800 and then saturates at a constant value in the subsequent range. From these results, it can be seen that in order to increase the intensity amplification rate of the nonlinear resonant structure phototransistor of the present invention, it is important to lower the transmission loss.

[0101] Figure 9 is a linear scale graph. The transmission loss coefficient is In the case where =0.003dB / cm, the intensity amplification factor decreases sharply at a relatively very large value. Therefore It is difficult to distinguish between the other two cases of intensity amplification rates, which are 0.3dB / cm or 0.03dB / cm, as they overlap significantly. To compare the changes in intensity amplification rates in more detail, it is necessary to compare them on a log scale.

[0102] dB Scale Intensity Amplification Factor of a Phototransistor It can be equal to mathematical formula 9.

[0103]

[0104] In other words, the dB scale intensity amplification rate of a phototransistor is the definition of the dB scale applied to the definition of the intensity amplification rate of a phototransistor.

[0105] FIG. 10 is a graph showing an example of the phototransistor dB scale intensity amplification rate for changes in the intensity of the signal wave (104) provided to the first mirror (120) of FIG. 5. The simulation result of FIG. 10 is a calculation result obtained by applying the simulation result of FIG. 9 directly to the definition of the dB scale. Points having the same transmission loss coefficient can be connected by a smooth curve.

[0106] Referring to Fig. 10, A nonlinear medium (110) having a transmission loss factor of =0.003dB / cm can have an excellent dB scale intensity amplification rate. The transmission loss factor When =0.3 dB / cm, base intensity change 0 ~ 1.0mW / For the interval, the dB scale intensity amplification factor decreases almost linearly between approximately 3 and 5. The transmission loss coefficient is When =0.03dB / cm, base intensity change 0 ~ 1.0mW / For the interval, the dB scale intensity amplification factor decreases sharply, reaching from 20 to about 9. The transmission loss coefficient is When =0.003dB / cm, base intensity change 0 ~ 0.2mW / In the interval, the dB scale intensity amplification rate decreases sharply from 36 to about 16, and then decreases strongly to around 10 in the subsequent interval. It can be seen that the change in intensity amplification rate can be compared in more detail through the comparison of dB scale intensity amplification rates.

[0107] The following are the second-order nonlinear coefficients mentioned in the description of Fig. 1. Let us examine the effect of the Type-II second harmonic generation interaction. As mentioned in the description of FIG. 1, in a nonlinear resonant structure phototransistor, the pump wave (102) and the signal wave (104) are physically independent light waves that have the same frequency but are orthogonal to each other in polarization. Although the term "orthogonal" is used in the description for physical accuracy, the term "intersecting" may be used in the claims to comprehensively secure the scope of rights.

[0108] The pump wave (102) and the signal wave (104) are second-order nonlinear coefficients , It participates in sequential Type-I second harmonic generation and inverse second harmonic generation by. However, if the second nonlinear coefficient If exists, simultaneously It can also participate in the generation of Type-II second harmonics through this. It is assumed that... This means there is no interaction due to direct coupling between the three light waves participating in the generation of Type-I second harmonics. As explained in Fig. 6, the second nonlinear coefficients , The second harmonic participating in the interaction by is Y-polarized, and The second harmonic participating in the interaction is X-polarized light. The two second harmonics are physically independent light waves with the same frequency but mutually perpendicular polarizations.

[0109] The pump wave (102) input with a relatively strong intensity rapidly attenuates through the simultaneous participation of sequential Type-I second harmonic generation, inverse second harmonic generation, and Type-II second harmonic generation interactions. The intensity of the Type-I Y-polarized second harmonic generated by the interaction of the strong intensity pump wave (102) and the pump wave (102) is relatively strong. The intensity of the Type-II X-polarized second harmonic generated by the interaction of the strong intensity pump wave (102) and the weak intensity signal wave (104) is relatively weak. Therefore, the resonating Y-polarized second harmonic intensity is relatively stronger than the resonating X-polarized second harmonic intensity.

[0110] The sequential Type-I second harmonic generation and inverse second harmonic generation interaction attenuates the intensity of the pump wave (102), generates a Y-polarized second harmonic, and amplifies the intensity of the signal wave (104). The Type-II second harmonic generation interaction attenuates the intensity of the pump wave (102) and the signal wave (104), and generates an X-polarized second harmonic. A signal wave (104) input with a relatively weak intensity is amplified in the sequential Type-I second harmonic generation and inverse second harmonic generation interaction and attenuated in the Type-II second harmonic generation interaction. Therefore, if the Type-II second harmonic generation interaction is present, the degree of amplification of the signal wave (104) amplified in the sequential Type-I second harmonic generation and inverse second harmonic generation interaction is reduced.

[0111] Additionally, the Y-polarized second harmonic generated by the input of the pump wave (102) before the signal wave (104) is input resonates within the resonant structure with a strong intensity, balancing the transmission loss. At this time, when the signal wave (104) is input sequentially, the Y-polarized second harmonic amplifies the signal wave (104), and the X-polarized second harmonic is generated and attenuates the signal wave (104). That is, the generation of the X-polarized second harmonic by the Type-II second harmonic generation interaction reduces the degree of amplification of the signal wave (104) by the sequential Type-I second harmonic generation and the inverse second harmonic generation interaction. In this case, the degree of amplification of the signal wave (104) by the inverse second harmonic generation is greater than the degree of attenuation of the signal wave (104) by the Type-II second harmonic generation, so the signal wave (104) is expected to be amplified overall.

[0112] In conclusion, to avoid Type-II second harmonic generation interactions, if artificially possible, during the nonlinear crystal growth process It is necessary to make it zero. In addition, for the implementation of an efficient nonlinear resonant structure phototransistor, an optical waveguide of a nonlinear medium is required that has large Type-I second harmonic generation and inverse second harmonic generation nonlinear coefficients but small transmission loss coefficients.

[0113] Next, the case of a single-frequency based nonlinear resonant structure phototransistor using a third-order nonlinear medium and a selective resonant structure is briefly described. The phototransistor of the present invention based on third-order nonlinear interaction is equivalent to the phototransistor of the present invention based on second-order nonlinear interaction. That is, the nonlinear medium (110) may be a third-order nonlinear medium, and a third-order nonlinear interaction is used instead of a second-order nonlinear interaction, and the rest is equivalent. In the nonlinear resonant structure phototransistor of the present invention operating with a single-frequency light wave, the third-order nonlinear interaction is sequential third-order harmonic generation and inverse third-order harmonic generation (Cascaded THG / iTHG). A brief summary is as follows.

[0114] When a pump wave (102) is input to the emitter of a nonlinear resonant structure phototransistor, a third harmonic generating interaction is induced by the third nonlinear medium. The third harmonic wave generated at this time resonates within the resonant structure. Then, when a signal wave (104) is input to the base, the signal wave (104) is amplified by an inverse third harmonic generating interaction with the resonating third harmonic wave. The amplified signal wave (104) is output through the collector. The on-off and intensity of the signal wave (104) output from the collector are controlled by the signal wave (104) of the base.

[0115] Looking at the structure of the phototransistor (100) of the nonlinear resonant structure of the present invention, the nonlinear medium (110) is third-order nonlinear, and the nonlinear interaction is third-order nonlinear interaction. In FIG. 1, a pump wave (102) is input at the emitter, and a signal wave (104) is input at the base. First, when the pump wave (102) is input at the emitter, the third-order harmonic of the pump wave (102) is generated as shown in Equation 10 through the phenomenon of generating the third-order harmonic of the pump wave (102).

[0116]

[0117] The generated third harmonic cannot penetrate to the outside of the resonant structure but resonates internally, increasing in intensity. The polarization direction of the third harmonic is also the light wave transmission direction. It is perpendicular to and in the polarization direction of the pump wave (102) ( = ) or signal wave (104) polarization direction ( = )am.

[0118] When a signal wave (104) is input to the base sequentially, the signal wave (104) is amplified as in Equation 11 by the phenomenon of generating an inverse third harmonic between the signal wave (104) and the resonant third harmonic.

[0119]

[0120] Here, the signal wave (104) is output through the collector. That is, when the pump wave (102) is input at the emitter and the signal wave (104) is input at the base, the signal wave (104) is output at the collector. At this time, amplification and switching are implemented by the on-off operation of the signal wave (104) output at the collector according to the on-off operation of the signal wave (104) input at the base.

[0121] That is, the role of the resonant structure and the third nonlinear medium in amplification and switching is equivalent to that of the second harmonic described in FIGS. 2 and FIGS. 5. Consequently, a single-frequency-based nonlinear resonant structure phototransistor using a third nonlinear medium (110) and an optional resonant structure is also possible.

[0122] FIGS. 11 and FIGS. 12 are drawings showing an example of an optical system (1000) according to the concept of the present invention.

[0123] Referring to FIGS. 11 and 12, the optical system (1000) of the present invention may include a phototransistor (100), a light source (200), a beam splitter (300), a control mirror (400), a first polarizer (500), a second polarizer (600), and a photodetector (800).

[0124] The phototransistor (100) may be a phototransistor of a nonlinear resonant structure operating at a single frequency. The phototransistor (100) may generate digital information data including 0 of a pump wave (102) and 1 of a signal wave (104) using a light wave (101). According to one example, the phototransistor (100) may include a nonlinear medium (110), a first mirror (120), and a second mirror (130).

[0125] A nonlinear medium (110) may be provided between the first mirror (120) and the second mirror (130). The nonlinear medium (110) may include at least one of a crystal, semiconductor, silica, and polymer having second-order nonlinearity or third-order nonlinearity.

[0126] The first mirror (120) may be provided on one side wall of the nonlinear medium (110). The first mirror (120) transmits the pump wave (102) and the signal wave (104) into the nonlinear medium (110) and may reflect the second harmonic or third harmonic.

[0127] A second mirror (130) may be provided on the other side wall of the nonlinear medium (110) facing the first mirror (120). The second mirror (130) transmits the pump wave (102) and signal wave (104) that have traveled through the nonlinear medium (110) and may reflect second harmonics or third harmonics. For example, each of the first mirror (120) and the second mirror (130) may include at least one of a dispersion Bragg mirror, a lattice crystal mirror, a dielectric mirror, and an optical mirror.

[0128] A light source (200) may be provided to one side of a phototransistor (100). The light source (200) may generate a light wave (101) and provide the light wave (101) to the phototransistor (100). The light wave (101) may include a laser beam.

[0129] A beam splitter (300) can be provided between a light source (200) and a phototransistor (100). The beam splitter (300) can separate the light wave (101) into a pump wave (102) and a signal wave (104).

[0130] Referring again to FIGS. 11 and 12, a first polarizer (500) may be provided between a beam splitter (300) and a phototransistor (100). The first polarizer (500) may polarize a pump wave (102). For example, the first polarizer (500) may include a horizontal polarizer. The pump wave (102) may include a horizontally polarized beam.

[0131] Referring again to FIGS. 11 and 12, a second polarizer (600) may be provided between the control mirror (400) and the phototransistor (100). The second polarizer (600) may polarize the signal wave (104). The first polarizer (500) and the second polarizer (600) may include mutually orthogonal polarizers. If the first polarizer (500) is a horizontal polarizer, the second polarizer (600) may include a vertical polarizer. The signal wave (104) may include a vertically polarized beam.

[0132] A control mirror (400) may be provided between the beam splitter (300) and the second polarizer (600). The control mirror (400) may switch the signal wave (104). The control mirror (400) may selectively provide the signal wave (104) to the phototransistor (100) according to a control signal from a control unit (not shown).

[0133] Referring to FIGS. 11 and FIGS. 12, FIGS. 11 and FIGS. 12 are schematic diagrams in which the actual pump wave (102) and the signal wave (104) can be combined again by a mirror and a coupler (not shown) and input on the same line.

[0134] Referring to FIG. 11, if the control mirror (400) does not reflect the signal wave (104) to the second polarizer (600) and thus does not input it to the phototransistor (100), the phototransistor (100) cannot output the pump wave (102) to the photodetector (800), that is, the phototransistor (100) can output an off state 0.

[0135] Referring to FIG. 12, when the control mirror (400) reflects the signal wave (104) to the second polarizer (600) and inputs it to the phototransistor (100), the phototransistor (100) can amplify the signal wave (104) and output the signal wave (104) to the photodetector (800). That is, the phototransistor (100) can output an ON state of 1.

[0136] A photodetector (800) may be provided on the other side of the phototransistor (100). The photodetector (800) may detect a pump wave (102) and a signal wave (104). The photodetector (800) may include a photodiode. Alternatively, the photodetector (800) may include a CMOS image sensor or a CCD image sensor, but the invention is not limited thereto.

[0137] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 In a nonlinear resonant structure phototransistor; a nonlinear medium that receives a pump wave polarized in a first direction having a first frequency to generate a second harmonic or a third harmonic, and receives a signal wave to amplify the signal wave through an interaction of generating an inverse second harmonic or an inverse third harmonic with the signal wave and the second harmonic or the third harmonic; a first mirror provided on one side of the nonlinear medium, transmitting the pump wave and the signal wave to the nonlinear medium and reflecting the second harmonic or the third harmonic; A nonlinear resonant optical transistor comprising a second mirror provided on the other side of the nonlinear medium, transmitting the pump wave and the signal wave and reflecting the second harmonic or the third harmonic, wherein in a first operating mode the pump wave is incident on the nonlinear medium through the first mirror, and in a second operating mode the pump wave and the signal wave are incident on the nonlinear medium through the first mirror, and in the second operating mode the pump wave and the signal wave operate at a single frequency having polarization directions perpendicular to each other. Claim 2 In claim 1, the signal wave is a nonlinear resonant structure phototransistor operating at a single frequency, polarized in a second direction intersecting the first direction and having the first frequency. Claim 3 delete Claim 4 In claim 2, in the second operating mode, the pump wave and the signal wave are nonlinear resonant optical transistors that operate at a single frequency having the same optical waveguide effective refractive index. Claim 5 In claim 2, a nonlinear resonant structure phototransistor operating at a single frequency, wherein in the first operating mode, the resonance length of the nonlinear medium is provided as a length at which the intensity of the pump wave output through the second mirror converges to '0', and in the second operating mode, the logic value of the output wave is determined according to the intensity of the signal wave output through the second mirror. Claim 6 In claim 2, a nonlinear resonant optical transistor in which, in the second operating mode, when the signs of the second nonlinear coefficient or the third nonlinear coefficient determining the attenuation of the pump wave and the amplification of the signal wave are opposite, the pump wave and the signal wave operate at a single frequency having a phase difference of 0 between the initial values. Claim 7 In claim 2, in the second operating mode, when the sign of the second nonlinear coefficient determining the attenuation of the pump wave and the amplification of the signal wave is the same, the pump wave and the signal wave have a phase difference between the initial values A nonlinear resonant structure phototransistor operating at a single frequency having Claim 8 In claim 2, when the sign of the third nonlinear coefficient determining the attenuation of the pump wave and the amplification of the signal wave is the same in the second operating mode, the pump wave and the signal wave are a nonlinear resonant structure phototransistor operating at a single frequency having a phase difference of ±π between the initial values. Claim 9 In claim 2, a nonlinear resonant optical transistor that operates at a single frequency in which the amplified signal wave is output through the second mirror in the second operating mode. Claim 10 A nonlinear resonant optical transistor according to claim 2, wherein the first operating mode is in an off state or logic '0' state mode, and the second operating mode is in an on state or logic '1' state mode, and operates at a single frequency corresponding to an amplification mode that amplifies the signal wave by the second harmonic or third harmonic. Claim 11 A nonlinear resonant optical transistor operating at a single frequency, wherein the logic value of the output wave output from the nonlinear medium is determined as logic '1' when the intensity of the output wave is stronger than the reference intensity, and logic '0' when the intensity of the output wave is equal to or weaker than the reference intensity. Claim 12 In claim 1, each of the first mirror and the second mirror is a nonlinear resonant structure phototransistor operating at a single frequency, comprising at least one of a dispersion Bragg mirror, a lattice crystal mirror, a dielectric mirror, and an optical mirror. Claim 13 In claim 1, the nonlinear medium comprises at least one of a crystal, semiconductor, silica, and polymer having second-order or third-order nonlinearity, and is a nonlinear resonant structure phototransistor operating at a single frequency. Claim 14 A light source generating a light wave having a first frequency; a beam splitter provided adjacent to the light source and separating the light wave into a pump wave and a signal wave; a first polarizer transmitting the pump wave and polarizing the pump wave in a first direction; a second polarizer transmitting the signal wave and polarizing the signal wave in a second direction; and an optical transistor amplifying the signal wave using the pump wave, wherein the optical transistor comprises: a nonlinear medium that receives the pump wave to generate a second harmonic or a third harmonic, receives the signal wave having the first frequency, and amplifies the signal wave through an interaction between the signal wave and the second harmonic or the third harmonic to generate an inverse second harmonic or an inverse third harmonic; a first mirror provided on one side of the nonlinear medium, transmitting the pump wave and the signal wave to the nonlinear medium, and reflecting the second harmonic or the third harmonic; An optical system comprising a second mirror provided on the other side of the above-mentioned nonlinear medium, transmitting the pump wave and the signal wave, and reflecting the second harmonic or third harmonic. Claim 15 An optical system according to claim 14, further comprising a control mirror provided between the beam splitter and the second polarizer. Claim 16 In claim 14, the above pump wave and the above signal wave are an optical system having polarization directions perpendicular to each other. Claim 17 An optical system according to claim 14, wherein the first polarizer comprises a horizontal polarizer and the second polarizer comprises a vertical polarizer. Claim 18 An optical system according to claim 14, further comprising a photodetector provided adjacent to the second mirror and detecting the pump wave and the signal wave.

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