Laser element and information processing device

Abstract

[Problem] To provide a compact structure capable of generating an entangled photon pair with high optical alignment robustness and high efficiency. [Solution] A resonator 2 having a first reflective layer 3, a laminated semiconductor layer 4, a polarization control element 5, a nonlinear crystal 6, and a second reflective layer 7 is irradiated with pump light Lp having a defined polarization state, and a high internal electric field strength generated by the standing wave of the pump light Lp is used to induce spontaneous parametric down-conversion in the nonlinear crystal 6. This increases the probability that the pump light Lp is wavelength-converted into signal light Ls and idler light Li, thereby efficiently generating an entangled photon pair Fa and Fb.

Description

Laser element and information processing device

[0001] The present disclosure relates to a laser device and an information processing device.

[0002] Light sources utilizing quantum entanglement are important elements in applications such as quantum information processing and quantum communication. In particular, entangled light sources that generate entangled photon pairs are expected to be used in key distribution in quantum communication, which realizes secure communication means, and quantum imaging. For example, a method for obtaining entangled photon pairs using a polarized photon pair generator and a half-wave plate has been proposed (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2003-228091

[0004] However, the practical application of quantum entanglement light sources faces the issue of the extremely low generation rate of entangled photon pairs. Currently, entangled photon pairs must be generated in a laboratory environment using highly precise optical alignment, which necessitates the development of large-scale quantum entanglement light sources.

[0005] For example, the polarization-defined photon pair generating device disclosed in Patent Document 1 has a complex structure and is difficult to miniaturize.

[0006] Therefore, the present disclosure provides a laser element and an information processing device that can be miniaturized, have high robustness in optical alignment, and can efficiently generate entangled photon pairs.

[0007] In order to solve the above problems, the present disclosure provides a laser device including a resonator that generates two lights that satisfy a phase matching condition using light with a determined polarization state.

[0008] The resonator may include a polarization control element that generates light with a defined polarization state by controlling the polarization of incident light, and a nonlinear crystal that generates the two lights with the same or different polarization states based on the light generated by the polarization control element.

[0009] The resonator may include a nonlinear crystal that generates light with a defined polarization state by controlling the polarization of incident light, and generates the two lights with the same or different polarization states based on the light with the defined polarization state.

[0010] The nonlinear crystal may have a polarization control section that controls the polarization of the incident light to generate light with the determined polarization state.

[0011] The nonlinear crystal may convert at least a portion of the light with a determined polarization state into the two lights having the same wavelength or wavelengths orthogonal to each other.

[0012] The light with a definite polarization state may be pump light, and the two lights may be signal light and idler light generated by wavelength conversion of the pump light.

[0013] The resonator may include a first reflecting layer and a second reflecting layer spaced apart in the optical axis direction, the second reflecting layer reflecting at least a portion of the light reflected by the first reflecting layer toward the first reflecting layer and transmitting the two lights, and the nonlinear crystal may be disposed between the first reflecting layer and the second reflecting layer.

[0014] The resonator may have a light emitting section disposed between the first reflecting layer and the second reflecting layer, and light emitted by the light emitting section may be polarization-controlled as the incident light.

[0015] The light emitting portion may have a laminated semiconductor layer including an active layer that emits light in response to an injected current.

[0016] The laser device may include a laser medium that accumulates the energy of incident light to generate excitation light.

[0017] The laser device may include a laser medium that accumulates energy of light emitted from the laminated semiconductor layer to generate pumping light, and the resonator may include: a first resonator that has the laminated semiconductor layer and the laser medium and resonates the pumping light; and a second resonator that has the nonlinear crystal and resonates the light with a determined polarization state.

[0018] The first resonator and the second resonator may be arranged so as to partially overlap each other in the optical axis direction.

[0019] The first resonator may have the first reflective layer and a third reflective layer that resonates the excitation light between the first reflective layer and the third reflective layer, and the second resonator may have the second reflective layer and a fourth reflective layer that resonates the light whose polarization state has been determined between the second reflective layer and the fourth reflective layer, and the first reflective layer, the fourth reflective layer, the laser medium, the third reflective layer, and the second reflective layer may be arranged in this order along an optical axis.

[0020] A saturable absorber may be included to generate pulsed laser light.

[0021] The laser may further include a saturable absorber disposed between the laser medium and the nonlinear crystal.

[0022] The laminated semiconductor layer, the laser medium, the saturable absorber, and the nonlinear crystal may be integrally bonded together.

[0023] The resonator may also include a fifth reflecting layer disposed between the first reflecting layer and the nonlinear crystal, which reflects the two light beams generated by the light with a determined polarization state that passes through the nonlinear crystal, is reflected by the second reflecting layer, and is incident on the nonlinear crystal.

[0024] It may also be a VECSEL (Vertical External Cavity Surface Emitting Laser).

[0025] The present disclosure also provides an information processing device comprising: a laser element; a photon detector that detects entangled photon pairs based on the two lights emitted from the laser element; and an information processing unit that performs predetermined information processing based on the entangled photon pairs detected by the photon detector.

[0026] The photon detector may include: a first photon detector that detects one photon of an entangled photon pair based on the two lights emitted from the laser element; and a second photon detector that detects the other photon of the entangled photon pair based on the two lights emitted from the laser element; and the information processing unit may include: a first information processing unit that performs first information processing based on the photons detected by the first photon detector; and a second information processing unit that performs second information processing based on the photons detected by the second photon detector.

[0027] 1 is a cross-sectional view showing a first configuration example of a laser element according to a first embodiment of the present disclosure. FIG. 2 is a diagram showing type I spontaneous parametric down-conversion. FIG. 3 is a schematic diagram showing type I spontaneous parametric down-conversion by a first nonlinear crystal. FIG. 4 is a schematic diagram showing type I spontaneous parametric down-conversion by a second nonlinear crystal. FIG. 5 is a diagram showing the relationship between the wave vectors of pump light, signal light, and idler light. FIG. 6 is a diagram showing the relationship between the frequencies of pump light, signal light, and idler light. FIG. 7 is a diagram showing type II spontaneous parametric down-conversion. FIG. 8 is a schematic diagram showing type II spontaneous parametric down-conversion by a nonlinear crystal. FIG. 9 is a cross-sectional view showing a second configuration example of a laser element according to the first embodiment of the present disclosure. FIG. 10 is a cross-sectional view showing a third configuration example of a laser element according to the first embodiment of the present disclosure. FIG. 11 is a cross-sectional view showing the configuration of a laser element according to a comparative example. FIG. 12 is a cross-sectional view showing the configuration of a laser element according to a second embodiment of the present disclosure. FIG. 13 is a cross-sectional view showing the configuration of a laser element according to a third embodiment of the present disclosure. FIG. 14 is a cross-sectional view showing the configuration of a laser element according to a fourth embodiment of the present disclosure. FIG. 15 is a block diagram showing the configuration of an information processing device according to a fifth embodiment of the present disclosure. FIG. 16 is a block diagram showing an example of a schematic configuration of a vehicle control system. FIG. 17 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit.

[0028] Hereinafter, embodiments of a laser element and an information processing device will be described with reference to the drawings. The following description will focus on the main components of the laser element and the information processing device, but the laser element and the information processing device may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0029] 1 is a cross-sectional view showing a first configuration example of a laser element according to a first embodiment of the present disclosure. The laser element 1 in Fig. 1 has, for example, a VECSEL (Vertical External Cavity Surface Emitting Laser) structure, and is a laser element that emits two light beams (a signal beam and an idler beam, which will be described later) capable of detecting entangled photon pairs. The two light beams emitted from the laser element 1 are detected by a photon detector (not shown in Fig. 1) or the like, and photons Fa and Fb, which are entangled photon pairs, are generated.

[0030] The photons F a and F b are in a state of quantum entanglement. Quantum entanglement refers to a state in which two or more particles that are physically separated are correlated with each other. More specifically, the photons F a and F b are in a state of polarization quantum entanglement, where the polarization states of the photons F a and F b are correlated with each other.

[0031] The polarization states of the photons F a and F b are undetermined until they are detected, and for example, horizontal and vertical polarization states overlap. The polarization states of the photons F a and F b can be determined by detection. Furthermore, when the polarization state of one of the photons F a and F b (e.g., photon F a) is determined by detection, the polarization state of the other (e.g., photon F b) is simultaneously determined, which is a non-classical correlation. For this reason, entangled photon pairs are also called quantum entangled photon pairs or polarization-entangled photon pairs.

[0032] Polarization-entangled photon pairs can be generated, for example, by spontaneous parametric down-conversion (SPDC), which is a convenient method because it can generate entangled photon pairs using a relatively simple technique of optically pumping a nonlinear crystal.

[0033] However, the probability of spontaneous parametric down-conversion is known to be extremely low. For example, the generation rate of entangled photon pairs for a photon incident on a nonlinear crystal is 10 －６In contrast to this, the laser device 1 according to this embodiment shown in Fig. 1 is characterized in that it can generate entangled photon pairs more efficiently than conventional devices.

[0034] 1 includes a resonator 2 for resonating light. The resonator 2 includes, for example, a first reflective layer 3, a laminated semiconductor layer 4, a polarization control element (optical element) 5, a nonlinear crystal 6, and a second reflective layer 7.

[0035] The resonator 2 has a structure in which, for example, a first reflective layer 3, a laminated semiconductor layer 4, a polarization control element 5, a nonlinear crystal 6, and a second reflective layer 7 are integrated. The laminated semiconductor layer 4, the polarization control element 5, and the nonlinear crystal 6 are arranged between the first reflective layer 3 and the second reflective layer 7. While Fig. 1 shows an example in which the laminated semiconductor layer 4, the polarization control element 5, and the nonlinear crystal 6 are arranged in this order along the optical axis from the first reflective layer 3 side, the resonator 2 may have any configuration. As will be described later, a configuration in which the polarization control element 5 is built into the nonlinear crystal 6 is also possible.

[0036] The resonator 2 is disposed, for example, on a substrate not shown in Fig. 1. The substrate is preferably thinned to suppress absorption of light resonated by the resonator 2, but is also preferably thick enough to maintain mechanical strength when bonded to other members.

[0037] The first reflective layer 3 and the second reflective layer 7 are, for example, electrically conductive semiconductor distributed Bragg reflectors (DBRs). The first reflective layer 3 and the second reflective layer 7 have, for example, a multi-reflection film in which two or more types of media with different refractive indices are alternately stacked. At least one of the first reflective layer 3 and the second reflective layer 7 may be made of a dielectric multilayer film.

[0038] The first reflective layer 3 may be set to have a higher reflectance for standing waves of light resonating within the resonator 2 than the second reflective layer 7. The second reflective layer 7 may also be a semi-transparent layer that transmits part of the standing waves.

[0039] The laminated semiconductor layer 4 includes a semiconductor layer 11, an active layer (light-emitting portion) 12, and a semiconductor layer 13. The semiconductor layers 11 and 13 are, for example, cladding layers, and confine charges in the active layer 12. The active layer 12 emits light from a surface by injecting charges. The active layer 12 includes, for example, a multiple quantum well layer in which two or more types of media are stacked. The laminated semiconductor layer 4 may include an electrode 14 that injects charges into the active layer 12.

[0040] The laser element 1 in FIG. 1 is a semiconductor laser element because its light emitting portion is composed of laminated semiconductor layers 4 .

[0041] The polarization control element 5 generates light with a definite polarization state by controlling the polarization state of light (incident light) emitted by the active layer 12. In this specification, the light generated by the polarization control element 5 is also referred to as pump light (pump laser light) Lp. The polarization control element 5 has, for example, a diffraction grating or a cleavage structure. The polarization control element 5 may use at least one of a wire grid, a photonic crystal element, a metasurface, or a grating structure.

[0042] The nonlinear crystal 6 generates two lights that satisfy the phase matching condition with the pump light Lp, based on the pump light Lp with a determined polarization state generated by the polarization control element 5. The two lights generated have the same or different polarization states. More specifically, the nonlinear crystal 6 wavelength-converts the pump light Lp into a pair of signal light (signal laser light) Ls and idler light (idler laser light) Li.

[0043] In this specification, the right side of FIG. 1, which is the emission direction of the signal light Ls and the idler light Li, may be referred to as the front of the optical axis, and the left side of FIG. 1 may be referred to as the rear of the optical axis.

[0044] The nonlinear crystal 6 is composed of at least one of a uniaxial crystal such as BBO (Beta Barium Borate), KDP (Potassium Dihydrogen Phosphate), or LN (Lithium Niobate), or a biaxial crystal such as KTP (Potassium Titanyl Phosphate), or LBO (Lithium Triborate). In addition to the above, the nonlinear crystal 6 may be composed of a two-dimensional material such as TMD (Transition Metal Dichalcogenide).

[0045] Next, the operation of the laser device 1 will be described. Light is emitted by injecting charges into the active layer 12 via the electrodes 14 or the like. The light emitted in the active layer 12 resonates between the first reflective layer 3 and the second reflective layer 7, increasing the light intensity. The polarization state of the light emitted in the active layer 12 is controlled by the polarization control element 5, and the polarization-controlled pump light Lp is incident on the nonlinear crystal 6. The pump light Lp is wavelength-converted into signal light Ls and idler light Li by spontaneous parametric down-conversion in the nonlinear crystal 6. Note that the nonlinear crystal 6 does not necessarily wavelength-convert all of the incident pump light Lp into signal light Ls and idler light Li; some of the pump light Lp may pass through the nonlinear crystal 6 without being wavelength-converted into signal light Ls and idler light Li.

[0046] Spontaneous parametric down-conversion can be classified into Type I and Type II conversions. Type I conversion results in entangled photon pairs F and F with the same polarization state. Type II conversion results in entangled photon pairs F and F with orthogonal polarization states.

[0047] 2 is a diagram showing spontaneous parametric down-conversion of Type I. In spontaneous parametric down-conversion of Type I, nonlinear crystals 21 and 22 whose crystal axes are perpendicular to each other are used as the nonlinear crystal 6.

[0048] In Type I spontaneous parametric down-conversion, the signal light Ls and the idler light Li propagate to form two concentric cones. The signal light Ls and the idler light Li have the same polarization state. A photon Fa is obtained from one of the two cones, and a photon Fb is obtained from the other. The photons Fa and Fb are located on a line passing through the centers of the two cones.

[0049] Fig. 3A is a schematic diagram showing spontaneous parametric down-conversion by the nonlinear crystal 21 of Fig. 2. Fig. 3B is a schematic diagram showing spontaneous parametric down-conversion by the nonlinear crystal 22 of Fig. 2. Figs. 3A and 3B show a polarization control element 5 that performs polarization control to determine the polarization state of light Lx emitted by the active layer 12.

[0050] 3A and 3B, pump light Lp controlled to a polarization state Ev (for example, a vertical polarization state) by the polarization control element 5 is incident on the nonlinear crystals 21 and 22. The pump light Lp is in a coherent state.

[0051] The nonlinear crystal 21 simultaneously emits the signal light Ls and the idler light Li, which have the same polarization state Ev as the pump light Lp. The nonlinear crystal 22 simultaneously emits the signal light Ls and the idler light Li, which have a polarization state Eh (e.g., horizontal polarization state) orthogonal to the pump light Lp.

[0052] The nonlinear crystals 21 and 22 are arranged to satisfy a phase matching condition, which is defined as the wave vectors of the pump light Lp, the signal light Ls, and the idler light Li, respectively, being k ｐ , k ｓ , and k ｉ Then, Δk = k ｐ -k ｓ -k ｉ This is the condition under which Δk=0 holds. The conversion efficiency by spontaneous parametric down-conversion is maximized when the phase matching condition is satisfied (i.e., Δk=0). In other words, the phase matching condition means that the laws of conservation of energy and conservation of momentum are maintained between the pump light Lp before wavelength conversion and the signal light Ls and idler light Li after wavelength conversion.

[0053] FIG. 4A shows that the phase matching condition is satisfied (i.e., k ｐ = k ｓ +k ｉ ) wave vector k ｐ , k ｓ , and k ｉ When the pump light Lp, the signal light Ls, and the idler light Li satisfy the phase matching condition, k ｐ = k ｓ +k ｉ FIG. 4B shows the frequency ω of the pump light Lp, the signal light Ls, and the idler light Li. ｐ , ω ｓ , and ω ｉ As shown in FIG. 4B, based on the law of conservation of energy, ｐ =ω ｓ +ω ｉ This becomes:

[0054] One method for satisfying the phase matching condition is, for example, angular phase matching (critical phase matching), which adjusts the angle θ of the crystal axis of the nonlinear crystal 6 with respect to the incident angle of the pump light Lp. Figures 3A and 3B show the crystal axes a, b, and c of the nonlinear crystals 21 and 22. The angle θ is formed between the c-axis of the crystal axes and the optical axis of the pump light Lp.

[0055] Another method for satisfying the phase matching condition is temperature phase matching (non-critical phase matching), which minimizes Δk by adjusting the temperature of the nonlinear crystal 6. Either method may be used to achieve the phase matching condition in the present disclosure. Alternatively, wavelength conversion may be performed after the phase matching condition is satisfied by another method.

[0056] The nonlinear crystals 21 and 22 are thin enough that it is impossible to distinguish which one has caused spontaneous parametric down-conversion. By using the nonlinear crystals 21 and 22, for example, integrated, the laser device 1 can emit entangled photon pairs Fa and Fb having the same polarization state, even though the polarization state is uncertain. Note that although Figure 2 shows an example in which the nonlinear crystal 22 is arranged further forward on the optical axis than the nonlinear crystal 21, the arrangement order of the nonlinear crystals 21 and 22 is arbitrary.

[0057] 5 is a diagram showing type II spontaneous parametric down-conversion. In type II spontaneous parametric down-conversion, a nonlinear crystal 23 is used. The nonlinear crystal 23 emits signal light Ls and idler light Li having mutually orthogonal polarization states. The signal light Ls and idler light Li propagate to form two cones inclined symmetrically with respect to the optical axis direction of the pump light Lp.

[0058] 6 is a schematic diagram showing spontaneous parametric down-conversion by a nonlinear crystal 23. Pump light Lp, whose polarization state is controlled to Ev by the polarization control element 5, is incident on the nonlinear crystal 23. The nonlinear crystal 23 simultaneously emits signal light Ls having the same polarization state Ev as the pump light Lp and idler light Li having a polarization state Eh orthogonal to that of the pump light Lp. The nonlinear crystal 23, like the nonlinear crystals 21 and 22, is arranged so as to satisfy the phase matching condition.

[0059] In Fig. 5, photons detected from the cone that is the propagation range of the signal light Ls have a polarization state Ev. Photons detected from the cone that is the propagation range of the idler light Li have a polarization state Eh. Furthermore, photons detected from the intersection of the two cones have an undetermined polarization state. At the two lines where the two cones intersect, entangled photon pairs Fa and Fb with orthogonal polarization states are obtained.

[0060] If the nonlinear crystal 6 has birefringence that is insufficient to compensate for variations in the linear refractive index over a wide wavelength range, or if the refractive index associated with the signal light Ls approaches the refractive index of the idler light L i as the wavelength of the electromagnetic radiation decreases, the phase matching condition may not be satisfied. In this case, a nonlinear crystal 6 that satisfies the quasi-phase matching condition may be used instead of the nonlinear crystals 21-23 described above.

[0061] A periodically poled down-conversion crystal is used as the nonlinear crystal 6 that satisfies the quasi-phase matching condition. A periodically poled down-conversion crystal is a crystal in which crystal lattices oriented in opposite directions are alternately arranged at a constant period Λ. In this case, the contribution Δk of the waveguide to the phase matching in the nonlinear crystal 6 is ｗｇUsing this, the quasi-phase matching condition is Δk ｑ = k ｐ -k ｓ -k ｉ −(2π / Λ)+Δk ｗｇ = 0. ｑ is compared to Δk, -(2π / Λ)+Δk ｗｇ The wave vector mismatch is compensated for by only the phase matching condition. Note that the phase matching condition in this specification includes the above-mentioned quasi-phase matching condition.

[0062] The resonator 2 in Fig. 1 resonates light emitted from the active layer 12 between the first reflective layer 3 and the second reflective layer 7. Since the light resonated in the resonator 2 does not have a specific polarization state as it is, the polarization state is determined by the polarization control element 5. This allows the resonator 2 to resonate pump light Lp with a determined polarization state and increase the light intensity. Therefore, the resonator 2 can increase the efficiency of spontaneous parametric down-conversion by the nonlinear crystal 6 by using the high internal electric field strength due to the standing wave of the pump light Lp with a determined polarization state.

[0063] 7 is a cross-sectional view showing a second configuration example of a laser element according to the first embodiment of the present disclosure. The laser element 1a in FIG. 7 is a solid-state laser element having a gain medium (laser medium) 31 as a light-emitting section. The gain medium 31 accumulates the energy of light Le_1, for example, incident on the laser element 1a from an external source, and emits pump light when the energy is sufficient to pump the light. Since the pump light emitted from the gain medium does not have a definite polarization state, the polarization control element 5 generates pump light Lp with a definite polarization state. Furthermore, by irradiating the pump light Lp with a definite polarization state into a nonlinear crystal 6, wavelength conversion can be performed to generate signal light Ls and idler light Li, similar to the laser element 1 in FIG. 1, and entangled photon pairs can be generated from these two lights.

[0064] The laser element 1 according to the first embodiment of the present disclosure may be realized as a solid-state laser element as shown in FIG. 8, or may be realized as a liquid laser element or a gas laser element.

[0065] 8 is a cross-sectional view showing a third configuration example of a laser element according to the first embodiment of the present disclosure. The laser element 1b in FIG. 8 differs from the laser element 1 in FIG. 1 in that it has a polarization control element (polarization control section) 5a within a nonlinear crystal 6a. Such a nonlinear crystal 6a can be realized, for example, by microfabricating the surface of the nonlinear crystal 6a and providing a diffraction grating or the like. This eliminates the need to provide a polarization control element 5 separately from the nonlinear crystal 6, allowing the laser element 1b to be miniaturized.

[0066] As in Fig. 8, for example, the laminated semiconductor layer 4 in Fig. 1 may have a polarization control function. For example, by providing a polarization control layer (e.g., an elliptical mesa) in the laminated semiconductor layer 4, it is possible to generate pump light Lp with a definite polarization state. Alternatively, the gain medium 31 in Fig. 7 may have a polarization control function. Specifically, a diffraction grating may be provided on the surface of the gain medium 31, or the crystal orientation of the gain medium 31 may be utilized to generate pump light Lp with a definite polarization state. This allows the polarization control element 5 to be omitted as in Fig. 8, thereby enabling the laser element 1 or 1a to be miniaturized.

[0067] Fig. 9 is a cross-sectional view showing the configuration of a laser element 100 according to a comparative example. The laser element 100 differs from the laser element 1 in Fig. 1 in that it does not have a first reflective layer 3 or a second reflective layer 7, and does not have a resonator 2. Note that the light-emitting portion is not shown in Fig. 9.

[0068] 9 is configured such that the pump light Lp generated by the polarization control element 5 passes through the nonlinear crystal 6 only once, which significantly reduces the probability that the pump light Lp will be wavelength-converted into the signal light Ls and the idler light Li, making it difficult to generate entangled photon pairs.

[0069] In contrast, in the laser element 1 according to the first embodiment of the present disclosure, the pump light Lp with a definite polarization state is resonated in the resonator 2 to increase the light intensity, so that the probability of wavelength conversion into the signal light Ls and the idler light Li in the nonlinear crystal 6 can be made higher than that of the laser element 100 in Figure 9, and entangled photon pairs can be generated efficiently.

[0070] As described above, the laser device 1 according to the first embodiment of the present disclosure has the polarization control element 5 and the nonlinear crystal 6 provided inside the resonator 2, and the nonlinear crystal 6 emits the signal light Ls and the idler light Li that satisfy the phase matching condition with the pump light Lp whose polarization is controlled by the polarization control element 5. This allows the laser device 1 to efficiently generate entangled photon pairs using the signal light Ls and the idler light Li.

[0071] Furthermore, in the laser device 1 according to the first embodiment, spontaneous parametric down-conversion is performed in the nonlinear crystal 6 using a high internal electric field strength due to a standing wave of the pump light Lp, the polarization state of which is determined and which is resonated in the resonator 2, and therefore the probability of wavelength conversion from the pump light Lp to the signal light Ls and the idler light Li can be increased. Therefore, entangled photon pairs can be efficiently generated using the signal light Ls and the idler light Li.

[0072] Furthermore, the laser element 1 according to the first embodiment can be constructed with a simple structure in which a polarization control element 5 and a nonlinear crystal 6 are provided inside the resonator 2, and therefore can be made compact and has excellent optical alignment robustness in which misalignment of the optical axis is unlikely to occur.

[0073] Second Embodiment Fig. 10 is a cross-sectional view showing the configuration of a laser device 1c according to a second embodiment of the present disclosure. The laser device 1c in Fig. 10 has a saturable absorber 41 in the resonator 2 and functions as a passive Q-switched laser device. The laser device 1c has a structure in which a first reflective layer 3, a gain medium 31, a polarization control element 5, a saturable absorber 41, a nonlinear crystal 6, and a second reflective layer 7 are integrated.

[0074] 10 shows an example in which the saturable absorber 41 is disposed between the polarization control element 5 and the nonlinear crystal 6. The location of the saturable absorber 41 is arbitrary, and it may be disposed, for example, behind the polarization control element 5 on the optical axis.

[0075] The saturable absorber 41 may have a polarization control function. For example, the polarization state of the pump light Lp can be controlled by controlling the crystal orientation of the saturable absorber 41 or by forming a diffraction grating by surface processing. In this case, the polarization control element 5 can be omitted from the laser element 1c.

[0076] In the initial stage when the gain medium 31 is excited by the saturable absorber 41, the pump light Lp is absorbed by the saturable absorber 41. When the optical intensity of the pump light Lp increases in the resonator 2 and exceeds a predetermined threshold, the optical absorption rate in the saturable absorber 41 drops sharply. As a result, the resonator 2 resonates the pump light Lp as a Q-switched pulse wave.

[0077] In this way, the laser device 1c according to the second embodiment can further improve the conversion efficiency of spontaneous parametric down-conversion in the nonlinear crystal 6 by converting the pump light Lp into a high-peak pulse using the saturable absorber 41.

[0078] 11 is a cross-sectional view showing the configuration of a laser device 1d according to a third embodiment of the present disclosure. The laser device 1d in FIG. 11 has a structure in which two resonators overlap on the same optical axis.

[0079] Specifically, in the laser element 1d of FIG. 11, the first reflective layer 3, the laminated semiconductor layer 4 (i.e., the semiconductor layer 11, the active layer 12, and the semiconductor layer 13), the fourth reflective layer 52, the gain medium 31, the third reflective layer 53, the polarization control element 5, the saturable absorber 41, the nonlinear crystal 6, and the second reflective layer 7 are arranged in this order from the rear side of the optical axis along the optical axis and are bonded together.

[0080] The first reflective layer 3 and the third reflective layer 53 constitute a part of a first resonator 2a that resonates the pumping light Le_2 emitted from the gain medium 31. The gain medium 31 accumulates the energy of the light emitted from the laminated semiconductor layer 4 to generate the pumping light Le_2. The first resonator 2a has the laminated semiconductor layer 4 and the gain medium 31.

[0081] The fourth reflective layer 52 and the second reflective layer 7 constitute a part of the second resonator 2b that resonates the pump light Lp. The second resonator 2b has a gain medium 31, a polarization control element 5, a saturable absorber 41, and a nonlinear crystal 6. The arrangement order of the polarization control element 5, the saturable absorber 41, and the nonlinear crystal 6 is not limited to the example in Fig. 11 and may be arbitrary. The laser element 1d may have a configuration in which the saturable absorber 41 is omitted.

[0082] As described above, the first resonator 2 a and the second resonator 2 b have the gain medium 31 in common.

[0083] The fourth reflective layer 52 is configured to transmit at least a portion of the excitation light Le_2 and reflect the pump light Lp at a predetermined reflectance. The third reflective layer 53 is configured to transmit at least a portion of the pump light Lp and reflect the excitation light Le_2 at a predetermined reflectance. The fourth reflective layer 52 and the third reflective layer 53 are formed, for example, by a dielectric multilayer film in which layers made of a high refractive index material and layers made of a low refractive index material are alternately stacked.

[0084] In the first resonator 2a, surface emission of the laminated semiconductor layer 4 is performed by injecting charge into the active layer 12. The light emitted from the laminated semiconductor layer 4 excites the gain medium 31, generating pump light Le_2. The first resonator 2a confines the power of the pump light Le_2 between the first reflective layer 3 and the third reflective layer 53, thereby increasing the light intensity of the pump light Le_2. The polarization control element 5 controls the polarization of the incident pump light Le_2 to generate pump light Lp with a determined polarization state. In the second resonator 2b, similar to FIG. 10 , the saturable absorber 41 can resonate the pump light Lp as a Q-switched pulse wave.

[0085] 10 , the laser device 1d according to the third embodiment of the present disclosure can further improve the conversion efficiency of spontaneous parametric down-conversion by using the saturable absorber 41. Furthermore, the laser device 1d can inject charges into the active layer 12 to cause the laminated semiconductor layer 4 to emit surface light, thereby exciting the gain medium 31 and generating pump light Le_2, thereby eliminating the need for external incidence of light Le_1. The laser device 1d can achieve miniaturization by overlapping the first resonator 2a and the second resonator 2b, and has excellent optical alignment robustness that can prevent misalignment of the optical axis. Furthermore, the use of high-peak pulses can further improve the conversion efficiency of spontaneous parametric down-conversion.

[0086] 12 is a cross-sectional view showing the configuration of a laser device 1e according to a fourth embodiment of the present disclosure. The laser device 1e in Fig. 12 differs from the laser device 1e in Fig. 1 in that it includes a reflective film (fifth reflective layer) 61 having high reflectivity for the signal light Ls and the idler light Li. The reflective film 61 is configured to transmit at least a portion of the pump light Lp.

[0087] 12 is disposed behind the nonlinear crystal 6 on the optical axis. That is, the nonlinear crystal 6 is disposed between the reflective film 61 and the second reflective layer 7. Although an example in which the reflective film 61 is disposed between the polarization control element 5 and the nonlinear crystal 6 is shown in FIG. 12 , the reflective film 61 may be disposed behind the polarization control element 5 on the optical axis.

[0088] The nonlinear crystal 6 converts a portion Lp_1 of the pump light Lp incident from the rear side of the optical axis into signal light Ls_1 and idler light Li_1 and emits them toward the front side of the optical axis. Furthermore, the remaining portion Lp_2 of the pump light Lp incident from the rear side of the optical axis passes through the nonlinear crystal 6, is reflected by the second reflective layer 7, and is re-incident on the nonlinear crystal 6 where it is converted into signal light Ls_2 and idler light Li_2. The signal light Ls_2 and idler light Li_2 are emitted toward the rear side of the optical axis and reflected by the reflective film 61. The signal light Ls_2 and idler light Li_2 reflected by the reflective film 61 pass through the nonlinear crystal 6 and are emitted toward the front side of the optical axis.

[0089] That is, the laser element 1e can emit signal light Ls_1 and idler light Li_1 based on the pump light Lp_1, signal light Ls_2 and idler light Li_2 based on the pump light Lp_2, and signal light Ls and idler light Li.

[0090] 12 can perform spontaneous parametric down-conversion using not only the pump light Lp_1 incident from the rear side of the optical axis, but also the pump light Lp_2 reflected by the second reflective layer 7 and incident from the front side of the optical axis. This can further improve the conversion efficiency of spontaneous parametric down-conversion and increase the number of entangled photon pairs.

[0091] The reflective film 61 according to the fourth embodiment of the present disclosure can be applied to any of the laser elements 1 to 1d according to the first to third embodiments.

[0092] Fifth Embodiment Fig. 13 is a block diagram showing the configuration of an information processing device 70 according to a fifth embodiment of the present disclosure. The information processing device 70 of Fig. 13 performs encrypted communication using entangled photon pairs. The information processing device 70 includes a laser element 1f, a first entangled light detection unit 71, a second entangled light detection unit 72, a first private key generation unit 73, a second private key generation unit 74, a first information processing unit 75, a second information processing unit 76, a first communication unit 77, and a second communication unit 78.

[0093] The laser element 1f is any one of the laser elements 1 to 1e according to the first to fourth embodiments. The laser element 1f emits signal light Ls and idler light Li.

[0094] 13 are collectively referred to as a photon detector. The photon detector detects entangled photon pairs based on two beams of light (signal light Ls and idler light Li) emitted from the laser element 1f.

[0095] 13 are collectively referred to as an information processing unit. The information processing unit performs predetermined information processing based on the entangled photon pairs detected by the photon detector.

[0096] More specifically, the first entangled light detection unit (first photon detector) 71 receives the signal light Ls and the idler light Li and detects the first entangled light Fc, which is one of the entangled photon pair. The second entangled light detection unit (second photon detector) 72 receives the signal light Ls and the idler light Li and detects the second entangled light Fd, which is the other of the entangled photon pair. The first entangled light Fc and the second entangled light Fd are, for example, the photons Fa and Fb shown in FIG. 1 .

[0097] The first entangled light detector 71 and the second entangled light detector 72 can be configured by, for example, a polarizing beam splitter (PBS) and a single photon avalanche diode (SPAD), etc. The first entangled light Fc and the second entangled light Fd are propagated to the first private key generator 73 and the second private key generator 74 by, for example, an optical fiber, etc.

[0098] The first private key generation unit 73 generates a first private key based on the first entangled light Fc and a shared key shared with the second private key generation unit 74. The second private key generation unit 74 generates a second private key based on the second entangled light Fd and the shared key.

[0099] The first information processing unit 75 encrypts data to be transmitted to the second communication unit 78 based on the first private key, and decrypts data received from the second communication unit 78. The second information processing unit 76 encrypts data to be transmitted to the first communication unit 77 based on the second private key, and decrypts data received from the first communication unit 77.

[0100] The first communication unit 77 transmits encrypted transmission data to the second communication unit 78, and receives transmission data from the second communication unit 78. The second communication unit 78 transmits encrypted transmission data to the first communication unit 77, and receives transmission data from the first communication unit 77.

[0101] When either the first entangled light detection unit 71 or the second entangled light detection unit 72 detects the polarization state of the entangled light, the polarization state of the other entangled light is determined instantaneously, providing excellent confidentiality. If a malicious third party detects one of the entangled photon pairs, the polarization states of the entangled light detected by the first entangled light detection unit 71 and the second entangled light detection unit 72 will change at that moment, allowing the presence of the third party to be instantly detected.

[0102] In this way, by detecting entangled photon pairs and generating a private key, quantum cryptography communication with excellent confidentiality can be performed with a simple configuration.

[0103] In addition, the entangled photon pairs generated by the laser element 1f can also be used, for example, in quantum imaging. In quantum imaging, one of the entangled photon pairs is used in an observation system that irradiates an object to be imaged, and the other is used in a reference system that does not irradiate the object to be imaged. For example, by measuring the spatial distribution of photons in the reference system, it is possible to indirectly obtain the spatial distribution of photons in the observation system that has spatial correlation. Quantum imaging enables highly sensitive imaging with excellent noise resistance and little influence from stray light.

[0104] (Application Examples) The technology according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of moving body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, a robot, construction machinery, or agricultural machinery (tractor).

[0105] 14 is a block diagram showing a schematic configuration example of a vehicle control system 7000, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied. The vehicle control system 7000 includes a plurality of electronic control units connected via a communication network 7010. In the example shown in FIG. 14 , the vehicle control system 7000 includes a drive system control unit 7100, a body system control unit 7200, a battery control unit 7300, an outside-vehicle information detection unit 7400, an inside-vehicle information detection unit 7500, and an integrated control unit 7600. The communication network 7010 connecting these multiple control units may be an in-vehicle communication network conforming to any standard, such as a Controller Area Network (CAN), a Local Interconnect Network (LIN), a Local Area Network (LAN), or FlexRay (registered trademark).

[0106] Each control unit includes a microcomputer that performs arithmetic processing according to various programs, a memory unit that stores the programs executed by the microcomputer or parameters used in various calculations, and a drive circuit that drives various controlled devices. Each control unit includes a network I / F for communicating with other control units via a communication network 7010, and a communication I / F for communicating with devices or sensors inside and outside the vehicle via wired or wireless communication. Figure 14 illustrates the functional configuration of the integrated control unit 7600, including a microcomputer 7610, a general-purpose communication I / F 7620, a dedicated communication I / F 7630, a positioning unit 7640, a beacon receiving unit 7650, an in-vehicle device I / F 7660, an audio / video output unit 7670, an in-vehicle network I / F 7680, and a memory unit 7690. The other control units also include a microcomputer, a communication I / F, a memory unit, and the like.

[0107] The drivetrain control unit 7100 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 7100 functions as a control device for a drive force generating device for generating drive force for the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating braking force for the vehicle. The drivetrain control unit 7100 may also function as a control device for an ABS (Antilock Brake System) or an ESC (Electronic Stability Control), etc.

[0108] A vehicle state detection unit 7110 is connected to the drivetrain control unit 7100. The vehicle state detection unit 7110 includes at least one of a gyro sensor that detects the angular velocity of the axial rotational motion of the vehicle body, an acceleration sensor that detects the acceleration of the vehicle, or a sensor that detects the amount of operation of the accelerator pedal, the amount of operation of the brake pedal, the steering angle of the steering wheel, the engine rotation speed, the rotation speed of the wheels, etc. The drivetrain control unit 7100 performs arithmetic processing using signals input from the vehicle state detection unit 7110, and controls the internal combustion engine, the drive motor, the electric power steering device, the brake device, etc.

[0109] The body system control unit 7200 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 7200 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 7200. The body system control unit 7200 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0110] The battery control unit 7300 controls the secondary battery 7310, which is the power supply source for the drive motor, in accordance with various programs. For example, information such as battery temperature, battery output voltage, or remaining battery capacity is input to the battery control unit 7300 from a battery device equipped with the secondary battery 7310. The battery control unit 7300 performs arithmetic processing using these signals, and controls the temperature regulation of the secondary battery 7310 or a cooling device or the like equipped in the battery device.

[0111] The outside vehicle information detection unit 7400 detects information outside the vehicle equipped with the vehicle control system 7000. For example, at least one of an imaging unit 7410 and an outside vehicle information detection unit 7420 is connected to the outside vehicle information detection unit 7400. The imaging unit 7410 includes at least one of a time-of-flight (ToF) camera, a stereo camera, a monocular camera, an infrared camera, and other cameras. The outside vehicle information detection unit 7420 includes at least one of an environmental sensor for detecting the current weather or climate, or a surrounding information detection sensor for detecting other vehicles, obstacles, pedestrians, etc. around the vehicle equipped with the vehicle control system 7000.

[0112] The environmental sensor may be, for example, at least one of a raindrop sensor that detects rain, a fog sensor that detects fog, a sunshine sensor that detects the degree of sunshine, and a snow sensor that detects snowfall. The surrounding information detection sensor may be at least one of an ultrasonic sensor, a radar device, and a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) device. The imaging unit 7410 and the outside vehicle information detection unit 7420 may each be provided as an independent sensor or device, or may be provided as a device in which multiple sensors or devices are integrated.

[0113] 15 shows an example of the installation positions of the imaging unit 7410 and the vehicle exterior information detection unit 7420. The imaging units 7910, 7912, 7914, 7916, and 7918 are provided, for example, at least one of the front nose, side mirrors, rear bumper, back door, and upper part of the windshield inside the vehicle cabin of the vehicle 7900. The imaging unit 7910 provided on the front nose and the imaging unit 7918 provided on the upper part of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 7900. The imaging units 7912 and 7914 provided on the side mirrors mainly acquire images of the sides of the vehicle 7900. The imaging unit 7916 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 7900. The imaging unit 7918 provided on the upper part of the windshield inside the vehicle cabin is mainly used to detect leading vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0114] 15 shows an example of the imaging ranges of the imaging units 7910, 7912, 7914, and 7916. Imaging range a indicates the imaging range of the imaging unit 7910 provided on the front nose, imaging ranges b and c indicate the imaging ranges of the imaging units 7912 and 7914 provided on the side mirrors, respectively, and imaging range d indicates the imaging range of the imaging unit 7916 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 7910, 7912, 7914, and 7916, a bird's-eye view image of the vehicle 7900 viewed from above can be obtained.

[0115] The outside vehicle information detection units 7920, 7922, 7924, 7926, 7928, and 7930 provided on the front, rear, sides, corners, and above the windshield inside the vehicle cabin of the vehicle 7900 may be, for example, ultrasonic sensors or radar devices. The outside vehicle information detection units 7920, 7926, and 7930 provided on the front nose, rear bumper, back door, and above the windshield inside the vehicle cabin of the vehicle 7900 may be, for example, LIDAR devices. These outside vehicle information detection units 7920 to 7930 are mainly used to detect preceding vehicles, pedestrians, obstacles, etc.

[0116] Returning to FIG. 14 , the explanation will be continued. The outside vehicle information detection unit 7400 causes the imaging unit 7410 to capture an image outside the vehicle and receives the captured image data. The outside vehicle information detection unit 7400 also receives detection information from the connected outside vehicle information detection unit 7420. If the outside vehicle information detection unit 7420 is an ultrasonic sensor, a radar device, or a LIDAR device, the outside vehicle information detection unit 7400 emits ultrasonic waves or electromagnetic waves and receives information on the received reflected waves. Based on the received information, the outside vehicle information detection unit 7400 may perform object detection processing or distance detection processing for people, vehicles, obstacles, signs, text on the road, etc. Based on the received information, the outside vehicle information detection unit 7400 may also perform environmental recognition processing for recognizing rainfall, fog, road conditions, etc. Based on the received information, the outside vehicle information detection unit 7400 may also calculate the distance to an object outside the vehicle.

[0117] The outside vehicle information detection unit 7400 may also perform image recognition processing or distance detection processing to recognize people, vehicles, obstacles, signs, or characters on the road surface based on the received image data. The outside vehicle information detection unit 7400 may perform processing such as distortion correction or alignment on the received image data, and may also generate an overhead image or a panoramic image by combining image data captured by different image capturing units 7410. The outside vehicle information detection unit 7400 may also perform viewpoint conversion processing using image data captured by different image capturing units 7410.

[0118] The interior information detection unit 7500 detects information inside the vehicle. A driver state detection unit 7510 that detects the driver's state is connected to the interior information detection unit 7500, for example. The driver state detection unit 7510 may include a camera that captures an image of the driver, a biosensor that detects the driver's biometric information, or a microphone that collects sound from within the vehicle cabin. The biosensor is provided, for example, on the seat or steering wheel, and detects the biometric information of a passenger sitting in the seat or the driver gripping the steering wheel. The interior information detection unit 7500 may calculate the driver's level of fatigue or concentration based on the detection information input from the driver state detection unit 7510, or may determine whether the driver is dozing off. The interior information detection unit 7500 may perform processing such as noise canceling on the collected audio signal.

[0119] The integrated control unit 7600 controls the overall operation of the vehicle control system 7000 according to various programs. An input unit 7800 is connected to the integrated control unit 7600. The input unit 7800 may be implemented by a device that can be operated by a passenger, such as a touch panel, a button, a microphone, a switch, or a lever. Data obtained by voice recognition of a voice input through a microphone may be input to the integrated control unit 7600. The input unit 7800 may be, for example, a remote control device using infrared or other radio waves, or an externally connected device such as a mobile phone or a personal digital assistant (PDA) that can operate the vehicle control system 7000. The input unit 7800 may be, for example, a camera, in which case the passenger can input information using gestures. Alternatively, data obtained by detecting the movement of a wearable device worn by the passenger may be input. Furthermore, the input unit 7800 may include, for example, an input control circuit that generates an input signal based on information input by the passenger using the input unit 7800 and outputs the input signal to the integrated control unit 7600. Passengers and the like operate this input unit 7800 to input various data to the vehicle control system 7000 and to instruct processing operations.

[0120] The storage unit 7690 may include a ROM (Read Only Memory) that stores various programs executed by the microcomputer, and a RAM (Random Access Memory) that stores various parameters, calculation results, sensor values, etc. The storage unit 7690 may also be realized by a magnetic storage device such as an HDD (Hard Disc Drive), a semiconductor storage device, an optical storage device, a magneto-optical storage device, or the like.

[0121] The general-purpose communication I / F 7620 is a general-purpose communication I / F that mediates communication with various devices present in the external environment 7750. The general-purpose communication I / F 7620 may implement a cellular communication protocol such as GSM (Global System of Mobile communications), WiMAX (registered trademark), LTE (Long Term Evolution), or LTE-Advanced (LTE-A), or other wireless communication protocols such as a wireless LAN (also referred to as Wi-Fi (registered trademark)) or Bluetooth (registered trademark). The general-purpose communication I / F 7620 may connect to a device (e.g., an application server or a control server) present on an external network (e.g., the Internet, a cloud network, or an operator-specific network) via, for example, a base station or an access point. In addition, the general-purpose communication I / F 7620 may connect to a terminal located near the vehicle (e.g., a terminal of a driver, pedestrian, or store, or an MTC (Machine Type Communication) terminal) using, for example, P2P (Peer To Peer) technology.

[0122] The dedicated communication I / F 7630 is a communication I / F that supports a communication protocol designed for use in vehicles. The dedicated communication I / F 7630 may implement a standard protocol such as WAVE (Wireless Access in Vehicle Environment), which is a combination of a lower layer IEEE 802.11p and an upper layer IEEE 1609, DSRC (Dedicated Short Range Communications), or a cellular communication protocol. The dedicated communication I / F 7630 typically performs V2X communication, which is a concept including one or more of vehicle-to-vehicle communication, vehicle-to-infrastructure communication, vehicle-to-home communication, and vehicle-to-pedestrian communication.

[0123] The positioning unit 7640 performs positioning by receiving, for example, GNSS signals from GNSS (Global Navigation Satellite System) satellites (for example, GPS signals from GPS (Global Positioning System) satellites), and generates position information including the latitude, longitude, and altitude of the vehicle. Note that the positioning unit 7640 may identify the current position by exchanging signals with a wireless access point, or may obtain position information from a terminal such as a mobile phone, PHS, or smartphone that has a positioning function.

[0124] The beacon receiving unit 7650 receives, for example, radio waves or electromagnetic waves transmitted from radio stations or the like installed on the road, and acquires information such as the current location, congestion, road closures, required travel time, etc. The function of the beacon receiving unit 7650 may be included in the dedicated communication I / F 7630 described above.

[0125] The in-vehicle device I / F 7660 is a communication interface that mediates connections between the microcomputer 7610 and various in-vehicle devices 7760 present in the vehicle. The in-vehicle device I / F 7660 may establish wireless connections using wireless communication protocols such as wireless LAN, Bluetooth (registered trademark), NFC (Near Field Communication), or WUSB (Wireless USB). Furthermore, the in-vehicle device I / F 7660 may establish a wired connection such as USB (Universal Serial Bus), HDMI (High-Definition Multimedia Interface), or MHL (Mobile High-Definition Link) via a connection terminal (and a cable, if necessary) not shown. The in-vehicle device 7760 may include, for example, at least one of a mobile device or a wearable device owned by a passenger, or an information device carried into or attached to the vehicle. The in-vehicle device 7760 may also include a navigation device that searches for a route to an arbitrary destination. The in-vehicle device I / F 7660 exchanges control signals or data signals with these in-vehicle devices 7760.

[0126] The in-vehicle network I / F 7680 is an interface that mediates communication between the microcomputer 7610 and the communication network 7010. The in-vehicle network I / F 7680 transmits and receives signals in accordance with a predetermined protocol supported by the communication network 7010.

[0127] The microcomputer 7610 of the integrated control unit 7600 controls the vehicle control system 7000 in accordance with various programs based on information acquired via at least one of the general-purpose communication I / F 7620, the dedicated communication I / F 7630, the positioning unit 7640, the beacon receiving unit 7650, the in-vehicle device I / F 7660, and the in-vehicle network I / F 7680. For example, the microcomputer 7610 may calculate control target values ​​for the driving force generating device, the steering mechanism, or the braking device based on the acquired information inside and outside the vehicle, and output control commands to the drivetrain control unit 7100. For example, the microcomputer 7610 may perform cooperative control aimed at realizing functions of an Advanced Driver Assistance System (ADAS), including vehicle collision avoidance or impact mitigation, following driving based on the following distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc. In addition, the microcomputer 7610 may perform cooperative control for the purpose of autonomous driving, in which the vehicle travels autonomously without relying on driver operation, by controlling a driving force generating device, a steering mechanism, a braking device, etc. based on information acquired about the vehicle's surroundings.

[0128] The microcomputer 7610 may generate three-dimensional distance information between the vehicle and objects such as surrounding structures and people, and create local map information including information about the vicinity of the vehicle's current location, based on information acquired via at least one of the general-purpose communication I / F 7620, the dedicated communication I / F 7630, the positioning unit 7640, the beacon receiving unit 7650, the in-vehicle device I / F 7660, and the in-vehicle network I / F 7680. Furthermore, the microcomputer 7610 may predict dangers, such as a vehicle collision, the approach of a pedestrian, or entry into a closed road, based on the acquired information, and generate a warning signal. The warning signal may be, for example, a signal for generating a warning sound or turning on a warning lamp.

[0129] The audio / image output unit 7670 transmits at least one audio and / or image output signal to an output device capable of visually or audibly notifying the vehicle occupants or the outside of the vehicle of information. In the example of FIG. 14 , an audio speaker 7710, a display unit 7720, and an instrument panel 7730 are illustrated as examples of the output devices. The display unit 7720 may include, for example, at least one of an on-board display and a head-up display. The display unit 7720 may have an AR (Augmented Reality) display function. The output device may also be other devices, such as headphones, a wearable device such as an eyeglass-type display worn by the occupant, a projector, or a lamp. When the output device is a display device, the display device visually displays results obtained by various processes performed by the microcomputer 7610 or information received from other control units in various formats, such as text, images, tables, and graphs. When the output device is an audio output device, the audio output device converts audio signals, such as reproduced audio data or acoustic data, into analog signals and audibly outputs the analog signals.

[0130] In the example shown in FIG. 14 , at least two control units connected via the communication network 7010 may be integrated into a single control unit. Alternatively, each control unit may be composed of multiple control units. Furthermore, the vehicle control system 7000 may include another control unit not shown. In the above description, some or all of the functions performed by one of the control units may be assigned to another control unit. In other words, as long as information is transmitted and received via the communication network 7010, predetermined arithmetic processing may be performed by one of the control units. Similarly, a sensor or device connected to one of the control units may be connected to another control unit, and multiple control units may transmit and receive detection information to and from each other via the communication network 7010.

[0131] A computer program for realizing each function of the information processing device 70 according to this embodiment described with reference to FIG. 13 can be implemented in any control unit or the like. A computer-readable recording medium storing such a computer program can also be provided. Examples of the recording medium include a magnetic disk, an optical disk, a magneto-optical disk, and a flash memory. The computer program may also be distributed, for example, via a network without using a recording medium.

[0132] In the vehicle control system 7000 described above, the laser element 1 according to this embodiment described with reference to Fig. 1 can be applied to the imaging unit 7410 of the application example shown in Fig. 14. For example, by using the laser element 1 to generate entangled photon pairs for quantum imaging, a quantum imaging device that is small and has high robustness in optical alignment can be realized, enabling highly sensitive imaging with excellent noise resistance.

[0133] Furthermore, at least some of the components of the information processing device 70 described using Fig. 13 may be realized in a module (for example, an integrated circuit module configured on a single die) for the integrated control unit 7600 shown in Fig. 14. Alternatively, the information processing device 70 described using Fig. 13 may be realized by a plurality of control units of the vehicle control system 7000 shown in Fig. 14.

[0134] The present technology may have the following configurations: (1) A laser element including a resonator that generates two lights that satisfy a phase matching condition using light with a definite polarization state. (2) The laser element according to (1), wherein the resonator includes: a polarization control element that generates light with a definite polarization state by polarization-controlling incident light; and a nonlinear crystal that generates the two lights with the same or different polarization states based on the light generated by the polarization control element. (3) The laser element according to (1), wherein the resonator includes: a nonlinear crystal that generates light with a definite polarization state by polarization-controlling incident light, and generates the two lights with the same or different polarization states based on the light with the definite polarization state. (4) The laser element according to (3), wherein the nonlinear crystal has a polarization control section that generates the light with the definite polarization state by polarization-controlling the incident light. (5) The laser element according to any one of (2) to (4), wherein the nonlinear crystal wavelength-converts at least a portion of the light with the definite polarization state into the two lights that are the same or orthogonal to each other. (6) The laser element according to any one of (2) to (5), wherein the light with a determined polarization state is pump light, and the two lights are signal light and idler light generated by wavelength conversion of the pump light. (7) The laser element according to any one of (2) to (6), wherein the resonator includes a first reflective layer and a second reflective layer spaced apart in the optical axis direction, and the second reflective layer reflects at least a portion of the light reflected by the first reflective layer toward the first reflective layer and transmits the two lights, and the nonlinear crystal is disposed between the first reflective layer and the second reflective layer. (8) The laser element according to (7), wherein the resonator has a light emitting unit disposed between the first reflective layer and the second reflective layer, and the light emitted by the light emitting unit is polarization-controlled as the incident light. (9) The laser element according to (8), wherein the light emitting unit has a laminated semiconductor layer including an active layer that emits light in response to an injected current. (10) The laser element according to any one of (1) to (9), comprising a laser medium that accumulates the energy of incident light to generate excitation light.(11) The laser element according to (9), comprising: a laser medium that accumulates energy of light emitted from the laminated semiconductor layer to generate pumping light, wherein the resonator comprises: a first resonator having the laminated semiconductor layer and the laser medium and resonating the pumping light, and a second resonator having the nonlinear crystal and resonating the light with the definite polarization state. (12) The laser element according to (11), wherein the first resonator and the second resonator are arranged to partially overlap in the optical axis direction. (13) The laser element according to (11) or (12), wherein the first resonator comprises the first reflective layer and a third reflective layer that resonates the pumping light between it and the first reflective layer, the second resonator comprises the second reflective layer and a fourth reflective layer that resonates the light with the definite polarization state between it and the second reflective layer, and the first reflective layer, the fourth reflective layer, the laser medium, the third reflective layer, and the second reflective layer are arranged in this order along the optical axis. (14) The laser element according to any one of (1) to (13), comprising a saturable absorber that generates pulsed laser light. (15) The laser element according to any one of (11) to (13), comprising a saturable absorber disposed between the laser medium and the nonlinear crystal. (16) The laser element according to (15), wherein the laminated semiconductor layer, the laser medium, the saturable absorber, and the nonlinear crystal are bonded together. (17) The laser element according to any one of (7) to (9), (11) to (13), (15), and (16), wherein the resonator comprises a fifth reflecting layer disposed between the first reflecting layer and the nonlinear crystal, and reflects the two light beams generated by the light, the polarization state of which has been determined, transmitted through the nonlinear crystal, reflected by the second reflecting layer, and then incident on the nonlinear crystal. (18) The laser element according to any one of (1) to (17), which is a VECSEL (Vertical External Cavity Surface Emitting Laser).(19) An information processing device comprising: the laser element according to any one of (1) to (18), a photon detector that detects an entangled photon pair based on the two lights emitted from the laser element, and an information processing unit that performs predetermined information processing based on the entangled photon pair detected by the photon detector. (20) The information processing device according to (19), wherein the photon detector has: a first photon detector that detects one photon of the entangled photon pair based on the two lights emitted from the laser element, and a second photon detector that detects the other photon of the entangled photon pair based on the two lights emitted from the laser element, and the information processing unit has: a first information processing unit that performs first information processing based on the photons detected by the first photon detector, and a second information processing unit that performs second information processing based on the photons detected by the second photon detector.

[0135] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents.

[0136] 1, 1a, 1b, 1c, 1d, 1e, 1f, 100 laser element, 2 resonator, 2a first resonator, 2b second resonator, 3 first reflective layer, 4 laminated semiconductor layer, 5, 5a polarization control element, 6, 6a, 21, 22, 23 nonlinear crystal, 7 second reflective layer, 11, 13 semiconductor layer, 12 active layer, 14 electrode, 31 gain medium, 41 saturable absorber, 52 fourth reflective layer, 53 third reflective layer, 61 reflective film, 70 information processing device, 71 first entangled light detection unit, 72 second entangled light detection unit, 73 first private key generation unit, 74 second private key generation unit, 75 first information processing unit, 76 second information processing unit, 77 first communication unit, 78 second communication unit

Claims

1. A laser element having a resonator that generates two beams of light that satisfy the phase matching condition using light with a defined polarization state.

2. The laser element according to claim 1, wherein the resonator comprises: a polarization control element that generates light with a definite polarization state by controlling the polarization of incident light; and a nonlinear crystal that generates the two lights with the same or different polarization states based on the light generated by the polarization control element.

3. The laser element according to claim 1, wherein the resonator generates light with a definite polarization state by controlling the polarization of incident light, and further comprises a nonlinear crystal that generates the two lights with the same or different polarization states based on the light with the definite polarization state.

4. The laser element according to claim 3, wherein the nonlinear crystal has a polarization control section that controls the polarization of the incident light to generate light with a definite polarization state.

5. The laser device according to claim 2, wherein the nonlinear crystal converts at least a portion of the light with a definite polarization state into the two lights of the same wavelength or wavelengths orthogonal to each other.

6. The laser device according to claim 2, wherein the light with a definite polarization state is pump light, and the two lights are signal light and idler light generated by wavelength conversion of the pump light.

7. The laser device according to claim 2, wherein the resonator comprises a first reflecting layer and a second reflecting layer spaced apart in the optical axis direction, the second reflecting layer reflects at least a portion of the light reflected by the first reflecting layer toward the first reflecting layer and transmits the two beams of light, and the nonlinear crystal is disposed between the first reflecting layer and the second reflecting layer.

8. The laser element according to claim 7, wherein the resonator has a light emitting section disposed between the first reflecting layer and the second reflecting layer, and light emitted by the light emitting section is polarization-controlled as the incident light.

9. The laser element according to claim 8, wherein the light emitting section has a laminated semiconductor layer including an active layer that emits light in response to an injected current.

10. The laser device according to claim 1, comprising a laser medium that accumulates the energy of incident light to generate pump light.

11. A laser element according to claim 9, comprising a laser medium that accumulates energy of light emitted from the laminated semiconductor layer to generate pump light, wherein the resonators comprise: a first resonator having the laminated semiconductor layer and the laser medium, and resonating the pump light; and a second resonator having the nonlinear crystal, and resonating the light with a determined polarization state.

12. The laser device according to claim 11, wherein the first resonator and the second resonator are arranged so as to partially overlap in the optical axis direction.

13. The laser element described in claim 11, wherein the first resonator has the first reflective layer and a third reflective layer that resonates the excitation light between it and the first reflective layer, the second resonator has the second reflective layer and a fourth reflective layer that resonates the light whose polarization state has been determined between it and the second reflective layer, and the first reflective layer, the fourth reflective layer, the laser medium, the third reflective layer, and the second reflective layer are arranged in this order along the optical axis.

14. The laser device according to claim 1, comprising a saturable absorber for generating pulsed laser light.

15. The laser device according to claim 11, further comprising a saturable absorber disposed between the laser medium and the nonlinear crystal.

16. The laser device according to claim 15, wherein the laminated semiconductor layer, the laser medium, the saturable absorber, and the nonlinear crystal are integrally bonded together.

17. The laser element according to claim 7, wherein the resonator comprises a fifth reflecting layer disposed between the first reflecting layer and the nonlinear crystal, which reflects the two beams of light generated by the light with a determined polarization state that passes through the nonlinear crystal, is reflected by the second reflecting layer, and is then incident on the nonlinear crystal.

18. The laser device according to claim 1, which is a VECSEL (Vertical External Cavity Surface Emitting Laser).

19. An information processing device comprising: a laser element according to claim 1; a photon detector that detects entangled photon pairs based on the two beams of light emitted from the laser element; and an information processing unit that performs predetermined information processing based on the entangled photon pairs detected by the photon detector.

20. The information processing device according to claim 19, wherein the photon detector comprises: a first photon detector that detects one photon of an entangled photon pair based on the two lights emitted from the laser element; and a second photon detector that detects the other photon of the entangled photon pair based on the two lights emitted from the laser element; and the information processing unit comprises: a first information processing unit that performs first information processing based on the photons detected by the first photon detector; and a second information processing unit that performs second information processing based on the photons detected by the second photon detector.

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