Apparatus for Modulating the Physical Properties of a Light Beam in Response to an Electrical Signal

Abstract

There is provided an apparatus (1) for modulating a physical property of a light beam in response to an electrical signal, comprising at least one optical modulation element (13) capable of modulating the physical property of the light beam in response to the electrical signal and a housing (10) enclosing the at least one optical modulation element (13). The housing (10) is configured to be integrated on a printed circuit board (40, 100).

Description

Technical Field

[0001] The present invention relates to a device for modulating the physical properties of a light beam in response to an electrical signal, and more particularly to a device integrated with or configured to be integrated with other electronic, optoelectronic, and optical components on a printed circuit board. The present invention also relates to a method for manufacturing such a device. Background Art

[0002] Currently, lasers are used in a large number of different application fields ranging from high-power applications such as material processing and welding to high-frequency applications in measurement technology, medicine, and optical communication technology. In the future, it is expected that the range of applications of laser beams will further grow.

[0003] Future applications are, for example, in the field of quantum technology (QT), which is an upcoming technology being researched and developed worldwide. This includes experiments for very promising everyday applications in fields such as computing, cryptography, sensors, telecommunications, holography, etc.

[0004] For many applications of lasers, not only in quantum technology, the light beam, the physical properties of the corresponding laser beam, need to be prepared in a special way. Not only the intensity of the laser beam must be controlled as in most current applications, but also other parameters such as phase, polarization, position, direction, frequency, noise, etc. must be adjusted very precisely. To prepare a laser beam, various electronic, mechanical, and optical components are required, including electro-optic modulators.

[0005] Currently, experimental equipment for new technologies requires a large amount of space. Figure 8 An example of a conventional device of such a system is shown. In a rack 900, space-consuming electronic devices such as a laser driver 901, an RF device 902, etc. are accommodated. Optical and optoelectronic devices such as a laser 903, an electro-optic modulator 904, a detector 905, and various components such as isolators, lenses, mirrors, etc. (not shown in the figure) are arranged on an optical unit 906 and are precisely adjusted in relation to each other. The laser beam 907 propagates from the laser 903 through free space via various components to the detector 905.

[0006] This system is accommodated in a protected environment, such as in a laboratory with controlled temperature, humidity, and cleanliness. With such a device, new functions can be achieved, but the complexity of the device prevents the transformation of these functions into industrial utilization.

[0007] In order to put new technologies into the practice of everyday applications, it is required that all components of the equipment (including electronic, optical, mechanical, etc.) must become more robust, smaller, less sensitive to dirt, environmental changes (temperature, pressure, etc.), and especially integratable with each other.

[0008] In the past, the miniaturization of electronic circuits and their integration on printed circuit boards have reached a high level. At the same time, some solutions are known in which some components of complex laser devices are also miniaturized and can be integrated with electronic circuits. These components of the laser system can include, for example, the laser itself, only optical devices such as mirrors, lenses, etc., and optoelectronic components such as photodetectors. However, in order to manipulate, stabilize, control, or adjust (which is generally summarized as the term "modulation" hereinafter) the properties of a laser beam in a desired manner, large-scale equipment still needs to be constructed, which prevents such systems from being put into daily practice.

[0009] The key component of the system is a device for modulating the physical properties of a light beam. A specific example of such a device is an electro-optic modulator. The electro-optic modulator changes the properties of light in response to an electrical signal applied to a piece of material having an electro-optic effect.

[0010] US 5,189,547 describes an electro-optic modulator that includes an electro-optic crystal and a resonant circuit mounted on a substrate and included in a package. Since the electro-optic effect is very small, a large voltage usually has to be applied to the crystal to achieve the desired effect. Therefore, by using such a modulator in a laser application, space-consuming experimental equipment will be required. In US 5,189,547, the voltage applied to the crystal is increased by a resonant circuit.

[0011] In order to reduce the voltage required to drive an electro-optic modulator, attempts have been made to reduce the size of the electro-optic component so as to enhance the electric field generated internally by the applied voltage. For example, EP2884331A1 describes an electro-optic modulator structure integrated on a silicon-on-insulator (SOI) substrate. The electro-optic component is formed by an optical waveguide made of an electro-optic polymer integrated on the substrate. An electro-optic modulator including an optical waveguide integrated on the substrate is commercially available. The waveguide generally has a thickness of about 50 μm. However, a waveguide with such a small cross-section can only be used for a limited wavelength range and a light beam with low power. In addition, the aperture of the waveguide is small, making free-space coupling of the light beam almost impossible. Therefore, the light must be coupled into the waveguide through an optical fiber. The optical fiber itself must be precisely aligned with respect to the waveguide.

[0012] The prior art known so far is not suitable for providing an overall fully miniaturized integrated optoelectronic system. Electro-optic modulators including electro-optic crystals in US 5,189,547 typically have dimensions of several centimeters. In addition, even in electro-optic modulators including optical waveguide structures as in EP 2884331 A1 where the electro-optic components themselves are small, the entire modulator has dimensions of several centimeters because the thin and sensitive electro-optic components must be mounted on a carrier and the optical fibers must also be fixed to and aligned with the electro-optic components. Therefore, neither type of electro-optic modulator can be integrated into a miniaturized electro-optic system. Summary of the Invention

[0013] Accordingly, an object of the present invention is to provide an electro-optic modulator that is small in size and can be easily integrated with different electronic, optoelectronic, and optical components.

[0014] The foregoing and other objects are achieved by the subject matter of the independent claims. Further embodiments are indicated in the dependent claims. Among them, method claims may also be further limited by the features of dependent product claims and vice versa.

[0015] A device for modulating the physical properties of a light beam in response to an electrical signal according to the present invention includes at least one light modulation element and a housing enclosing the at least one light modulation element, and the at least one light modulation element is capable of modulating the physical properties of a light beam in response to an electrical signal. The housing is configured to be integrated on a printed circuit board.

[0016] With such a device, for example, the function of modulating the physical properties of a light beam can be integrated with other electronic, optoelectronic, and optical components on a single printed circuit board, thereby integrating optical devices and electronic devices. In this way, for example, a complete laser system including a laser source and various optical and / or optoelectronic components (including their entire driver electronics) can be integrated with a device for modulating the physical properties of a light beam (as a device for preparing the properties of a laser beam in a desired manner) on a single printed circuit board, so that the size of such a device can be reduced by more than 1000 times compared to the size of current systems.

[0017] The term "modulating the physical properties of a light beam" herein means any change in the properties of a light beam, including manipulating, stabilizing, controlling, or adjusting the properties. Such properties are, for example, the intensity, phase, polarization, position, direction, frequency, noise, or any other property of the light beam.

[0018] The term "integrated on a printed circuit board" herein means that the housing is configured to be fixedly attached to the printed circuit board, for example, by gluing, bonding, and / or soldering. This also means that the housing has appropriate dimensions for integration on the printed circuit board, that is, dimensions comparable to other components on the printed circuit board.

[0019] The housing can be an outer shell, such as a standard through-hole or surface-mount package used in electronic devices. Thus, for example, the device can be easily handled as any other electronic component. By fixedly attaching the outer shell to a printed circuit board, the components housed in the outer shell are simultaneously electrically connected to the printed circuit board. If the outer shell is a metal outer shell, it also achieves shielding from its interior to the exterior, thereby enhancing electromagnetic compatibility.

[0020] The device may further include an insulating substrate, preferably made of a ceramic material, to which at least one light modulation element is attached, and the insulating substrate together with at least one light modulation element is housed within the housing. Thus, for example, the components of the device, such as the light modulation element and possible other circuits and components formed or mounted on the substrate within the housing, can be easily arranged.

[0021] Alternatively, the at least one light modulation element can be directly mounted on the printed circuit board, and the housing can be mounted on the printed circuit board in such a way as to enclose the at least one light modulation element. Thus, for example, the device for modulating the physical properties of a light beam can be directly integrated on the printed circuit board instead of being provided as a separate component that can be integrated on the printed circuit board. If the housing is a metal housing, it also achieves shielding from its interior to the exterior, thereby enhancing electromagnetic compatibility.

[0022] The housing may include: a light entrance window configured to allow a light beam from the outside to be guided to the input surface of the light modulation element; and a light exit window configured to allow the light beam leaving the output surface of the light modulation element to be transmitted to the outside. Thus, for example, a free-space light beam can be processed in the optical path formed on the printed circuit board.

[0023] The device may further include a signal input terminal for receiving an electrical signal for modulating the physical properties of a light beam, wherein the input impedance of the signal input terminal can match the characteristic impedance of the signal line formed on the printed circuit board, or match the characteristic impedance defined for the frequency range of the input signal, and the characteristic impedance is preferably 50Ω, 75Ω or 600Ω. Thus, for example, reflection of the input signal at the signal input terminal can be avoided, thereby enhancing electromagnetic compatibility. In the prior art, specific characteristic impedances of circuits and transmission lines are jointly defined for a specific signal frequency range. For example, for signals in the audio range, a standard characteristic impedance of 600Ω is defined. For high frequencies, characteristic impedances of 50Ω or Ω75 are defined.

[0024] The device may further include a resonant element having a resonant frequency and configured to provide a signal to the light modulation element having an amplitude greater than the amplitude of the electrical signal for modulating the physical properties of the light beam at the resonant frequency. Thus, for example, the voltage required to achieve the desired modulation of the light beam can be reduced.

[0025] The resonant element can be enclosed by a housing and / or it can act as an impedance matching element for matching the input impedance at the signal input to the characteristic impedance of the signal line formed on the printed circuit board or to the characteristic impedance defined for the frequency range of the electrical signal. Thus, for example, electromagnetic radiation emitted from the resonant element can be shielded by the housing and / or reflection of the electrical signal at the signal input can be avoided, thereby enhancing electromagnetic compatibility.

[0026] The resonant element can be mounted on a wiring pattern formed on a printed circuit board or a substrate, or it can be formed by multiple parts of the wiring pattern. Thereby, for example, it is possible to easily implement a resonant element integrated on a substrate included in an electro-optic modulator.

[0027] The resonant frequency of the resonant element can be adjustable. Thus, for example, the electro-optic modulator can be adapted to changes in the input frequency.

[0028] The device can include a traveling wave element configured to provide an electrical signal for modulating the physical properties of a light beam to a light modulation element, wherein the traveling wave element is enclosed by a housing and / or the traveling wave element acts as an impedance matching element for matching the input impedance at the signal input to the characteristic impedance of the signal line formed on the printed circuit board or to the characteristic impedance defined for the frequency range of the electrical signal. Thus, for example, electromagnetic radiation emitted from the traveling wave element can be shielded by the housing and / or reflection of the electrical signal at the signal input can be avoided, thereby enhancing electromagnetic compatibility.

[0029] The device can include at least one electro-optic modulator, wherein the electro-optic modulator includes a crystal made of a material having an electro-optic effect, and the crystal is the light modulation element of the device. Thus, for example, an electro-optic modulator can be provided as a device for modulating the physical properties of a light beam in response to an electrical signal, which can be integrated with a laser and / or other electronic, optoelectronic, and optical components on a single printed circuit board, thereby integrating optical devices and electronic devices and facilitating the creation of a small-sized micro-integrated electro-optic system.

[0030] The term "crystal" as used herein refers to a bulk crystal, wherein the electro-optic material is formed as a separate monolithic free-space crystal. In contrast, a waveguide formed integrally on a substrate as described above is not considered a "crystal" in the sense of the present invention. The term "free space" as used herein means that light freely propagates through space into the crystal and is not guided through an optical waveguide such as an optical fiber, where the optical waveguide is attached to the crystal in a fixed relationship.

[0031] A printed circuit board according to the present invention includes means for modulating the physical properties of a light beam in response to an electrical signal. Thus, for example, a printed circuit board can be provided on which an electro-optical modulator is integrated with other electronic, optoelectronic, and optical components, thereby integrating optical and electronic devices and facilitating the creation of a small-sized micro-integrated electro-optical system.

[0032] A method of manufacturing a device for modulating the physical properties of a light beam in response to an electrical signal according to the present invention includes: providing at least one light modulation element capable of modulating the physical properties of a light beam in response to an electrical signal; and enclosing the at least one light modulation element with a housing configured to be integrated on a printed circuit board. Using this method, for example, a device for modulating the physical properties of a light beam in response to an electrical signal can be manufactured, which can be easily integrated with other electronic, optoelectronic, and optical components on a single printed circuit board, thereby facilitating the creation of a small-sized micro-integrated electro-optical system.

[0033] The method can include manufacturing an electro-optical modulator by: providing an insulating substrate having a wiring pattern on at least one surface of the insulating substrate, providing a crystal made of a material having an electro-optic effect, the crystal being a light modulation element and having a set of electrodes so that an electric field is generated in the bulk crystal when a voltage is applied to the electrodes, attaching a bulk crystal to the insulating substrate, forming a resonant element on or through the wiring pattern, the resonant element having a resonant frequency and being configured to apply a signal having an increased amplitude compared to an input signal at the resonant frequency to the set of electrodes, and housing the substrate having the bulk crystal and the resonant element. Using this method, for example, an electro-optical modulator can be manufactured, which can be easily integrated with other electronic and optoelectronic components on a printed circuit board, thereby facilitating the creation of a small-sized integrated system.

[0034] A method of producing a printed circuit board according to the present invention includes: providing a printed circuit board, providing a device for modulating the physical properties of a light beam in response to an electrical signal according to the present invention, and integrating the device for modulating the physical properties of a light beam on the printed circuit board. In addition, electronic, optoelectronic, and / or optical components can also be integrated on the printed circuit board. Using this method, for example, a printed circuit board can be manufactured on which a device for modulating the physical properties of a light beam is integrated with other electronic, optoelectronic, and optical components, thereby facilitating the creation of a small-sized micro-integrated electro-optical system.

[0035] A method of operating a device for modulating a physical property of a light beam in response to an electrical signal includes: guiding the light beam from the outside to an input surface of a light modulation element; and providing an input signal to a signal input terminal of the device. Thus, for example, a device for modulating a physical property of a light beam in response to an electrical signal can be operated, which is integrated with other electronic, optoelectronic, and optical components, thereby facilitating the creation of a small-sized micro-integrated electro-optical system.

[0036] The use of a device for modulating a physical property of a light beam in response to an electrical signal according to the present invention includes performing modulation of the light beam. Thus, for example, the light beam can be modulated by an electro-optical modulator integrated with other electronic, optoelectronic, and optical components, thereby facilitating the creation of a small-sized micro-integrated electro-optical system.

[0037] A method for performing light beam modulation includes: guiding the light beam from the outside to an input surface of a light modulation element of a device for modulating a physical property of a light beam in response to an electrical signal according to the present invention, and providing an input signal to a signal input terminal of the device. Thus, for example, the light beam can be modulated by an electro-optical modulator integrated with other electronic, optoelectronic, and optical components, thereby facilitating the creation of a small-sized micro-integrated electro-optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further features and useful aspects of the present invention can be found in the description of the exemplary embodiments with reference to the accompanying drawings.

[0039] Figure 1 A schematic diagram of a printed circuit board according to the present invention is shown.

[0040] FIG. 2 shows a schematic diagram of an electro-optical modulator according to an embodiment of the present invention, wherein Figure 2a a schematic perspective view is shown, Figure 2b a schematic top view is shown, Figure 2c a schematic side view is shown, and Figure 2d a schematic front view is shown.

[0041] Figure 3 A schematic plan view of a substrate included in the electro-optical modulator shown in FIG. 2 is shown.

[0042] Figure 4 A schematic plan view of a modification of the substrate included in the electro-optical modulator shown in FIG. 2 is shown.

[0043] Figure 5 An exemplary arrangement of the electro-optical modulator shown in FIG. 2 on a printed circuit board is shown.

[0044] Figure 6 A schematic plan view of another modification of the substrate included in the electro-optical modulator shown in FIG. 2 is shown.

[0045] FIG. 7 shows a schematic diagram of an electro - optical modulator according to another embodiment of the present invention, wherein, Figure 7a a schematic top view is shown, Figure 7b a schematic front view is shown, Figure 7c a schematic side view is shown, Figure 7d a schematic pad pattern is shown, and Figure 7e a schematic bottom view is shown.

[0046] Figure 8 A conventional laser system is shown. DETAILED DESCRIPTION

[0047] Hereinafter, embodiments of the present invention will be described with reference to Figures 1 to 6 FIG. A schematic diagram of a printed circuit board 100 integrated with a laser system is shown. The printed circuit board has an electronic area 2 and an optical area 3. In the optical area 3, a laser 4, an electro - optical modulator 5, a photodetector 6, and optical elements 7 such as beam splitters and mirrors are mounted. In the electronic device area 2, electronic components 8 are mounted, such as drivers for optoelectronic components, signal processing circuits, or microcontrollers. The laser beam 9 propagating through free space is guided by optical components, for example, through a beam splitter to the photodetector 6 or through the electro - optical modulator 5 to another photodetector 6. The electro - optical modulator 5 serves as a device for modulating the physical properties of the light beam and as a means for preparing the properties of the laser beam in a desired manner. All components 4, 5, 6, 7, 8 are integrated on a single printed circuit board 100.

[0048] Figure 1 As an alternative, the laser can be omitted from the printed circuit board, and an external laser beam can be guided along the optical axis A shown by the dashed line to the optical and optoelectronic components integrated on the printed circuit board 100.

[0049]

[0050] Figures 2a to 2d Figure 2a FIG. shows a schematic diagram of a device in the form of an electro - optical modulator for modulating the physical properties of a light beam in response to an electrical signal. Wherein, Figure 2b a schematic perspective view is shown, Figure 2c a schematic top view is shown, Figure 2c a schematic side view is shown, and a schematic front view is shown.

[0051] The electro - optical modulator 1 includes a housing 10 having a first opening 11a formed on its front side and a second opening 11b formed on its rear side. The housing also has leads (pins) 12 for external electrical connection. At least one lead 12 serves as a signal input terminal for receiving an input signal.

[0052] Inside the housing 10, a light modulation element in the form of a crystal 13 is arranged in such a way that a light beam passing through the first opening 11a (light entrance window) of the housing 10 is incident on the front surface of the crystal 13, passes through the crystal 13 and exits the housing 10 through the second opening 11b (light exit window) on the opposite side of the housing 10. The crystal 13 is made of a material having an electro-optic effect. It can be any material commonly used in electro-optic modulators, having a linear electro-optic effect (also known as the Pockels effect), a quadratic electro-optic effect (also known as the Kerr effect) or any higher-order electro-optic effect. Examples of such materials include ammonium dihydrogen phosphate (ADP), potassium dihydrogen phosphate (KDP), deuterated potassium dihydrogen phosphate (DKDP or KD*P), potassium tantalate niobate (KTN), lithium niobate (LN), lithium tantalate (LT), etc. For infrared applications, gallium arsenide (GaAs) is particularly suitable.

[0053] The crystal is formed as a bulk crystal and preferably has the shape of a rectangular parallelepiped. The cross-section is selected to provide a sufficiently large aperture for the light beam used. For example, its dimensions can range from 0.5 mm × 0.5 mm to 20 mm × 20 mm, which is well-suited for an open-space laser beam with a beam width of 0.5 to 1 mm, which can be expected in an airborne electro-optic system. The length of the crystal depends on the required modulation magnitude. It can generally range from 5 to 30 mm.

[0054] In this embodiment, the crystal 13 and other elements are accommodated inside the housing 10. Exemplary examples of how this is achieved are described below, but the present invention is not limited to these examples.

[0055] Figure 3 A schematic plan view of a substrate 20 included in the electro-optic modulator 1 is shown. The substrate 20 is an insulating substrate, for example made of a ceramic material.

[0056] On the front surface 21 of the substrate 20, a wiring pattern 22 is arranged. The wiring pattern 22 can be formed, for example, by transmission lines, connection pads for connecting electronic components, and a ground pattern. Some of the connection pads can be used to connect the leads 12. On the back surface of the substrate 20, which is not shown in the figure, another wiring pattern can be formed, or the entire back surface can be covered with a ground plane.

[0057] The electro-optic crystal 13 is mounted on the substrate 20. A set of electrodes 14 is provided on the crystal 13 so as to generate an electric field inside the crystal 13 when a voltage is applied to the electrodes. The electrodes are connected to the connection pads of the wiring pattern 22 through bonding wires 15.

[0058] Also accommodated within the housing 10 is a resonant element having a resonant frequency for applying a signal with an amplitude increased relative to an input signal at the resonant frequency to the electrode group 14 of the crystal 13. In the present example, the resonant element is formed by a discrete LRC network mounted on a wiring pattern of a substrate. The LRC network is schematically represented in the figure by an electronic component 24 mounted, for example, by soldering to the wiring pattern 22. The electronic component 24 may also include an adjustable element, such as an adjustable inductor or capacitor, so that the resonant frequency of the LRC network can be changed.

[0059] Figure 4 Another example is shown. It differs from the Figure 3 example shown only in the form of the resonant element. Therefore, only the differences in the resonant element will be described below.

[0060] In this example, the resonant element 33 is integrated on the substrate 30 and is formed by a plurality of portions of the wiring pattern 32 formed on the front surface 31 of the substrate 30. These portions of the wiring pattern 32 forming the resonant element 33 may include, for example, transmission lines, shorting stubs or open stubs having a specific length relative to the electrical wavelength of a signal having an intended resonant frequency.

[0061] As an alternative to the above-described resonant element, split rings or cavities can be used to extend the frequency range to higher resonant frequencies.

[0062] The size of the entire electro-optic modulator is designed such that it can be easily mounted on a printed circuit board. The housing 10 shown in FIG. 2 is a customized specific surface-mount package. Alternatively, a standard package such as the SOT 23-6 type (SOT 23 with 6 leads) can be used. However, the housing can be any type of through-hole or surface-mount package used in electronic devices, such as TO-18, TO-263, DIL, LGA, PGA, etc., or any other type of package suitable for mounting on a printed circuit board. For example, it can be a metal housing or a plastic housing. The advantage of using a metal housing is that electromagnetic radiation generated within the package is effectively shielded.

[0063] Figure 5 A top view showing an exemplary arrangement of the electro-optic modulator 1 on a printed circuit board is shown.

[0064] On the front surface of the printed circuit board 40, a planar transmission line 41 is formed. The remaining portion of the front surface not covered by the transmission line 41 is covered by a ground pattern 42, with a gap 43 left between the transmission line 41 and the ground pattern 42.

[0065] The electro - optical modulator 1 is mounted on the printed circuit board 40, for example, by soldering its leads 12 to the transmission line 41 and the ground pattern 42 respectively. In this example, a single lead 12a is connected to the transmission line 41 and serves as a signal input, while the remaining leads 12b are connected to the ground pattern 42. Preferably, the electro - optical modulator 1 is mounted on the printed circuit board 40 in such a way that the two openings 11 through the housing 10 and the optical axis A of the crystal 13 are not blocked by other components mounted on the printed circuit board 40.

[0066] The input impedance of the signal input terminal 12a matches the characteristic impedance of the transmission line 41, or generally matches the characteristic impedance defined for the frequency range of the input signal. In the prior art, the specific characteristic impedance of the circuit and the transmission line is jointly defined for a specific signal frequency range. For example, for signals in the audio range, a standard characteristic impedance of 600Ω is defined. For high frequencies, characteristic impedances of 50Ω or 75Ω are defined. Depending on the internal structure of the electro - optical modulator 1, the impedance matching of the signal input terminal 12a can be performed in different ways.

[0067] For example, if the resonant element is implemented by a discrete LRC network as described above with reference to Figure 3 or by multiple parts of the wiring pattern as described above with reference to Figure 4 the design methods for adjusting the frequency and input impedance to the desired values are known. In addition, if the input impedance is different from the desired value, the design method for transforming the input impedance to the desired value by multiple parts of the wiring pattern is known. Due to the resonant operation of the electro - optical modulator in a small frequency range near the resonant frequency, it is only necessary to provide such impedance matching in this small frequency range. Using a resonant element for impedance matching has the advantage of very effective signal enhancement, while the bandwidth is limited.

[0068] As an alternative to matching the impedance of the signal input terminal 12a, the traveling - wave method can be used. Figure 6 A schematic plan view of another substrate 35 that can be included in the electro - optical modulator 1 is shown. On the front surface 36 of the substrate 35, a transmission line 37 is formed between the signal input terminal 12a and the signal output terminal 12c. The electro - optical crystal 13 is bonded to the transmission line 37 such that the transmission line 37 extends in the length direction of the crystal. Then, the input signal propagates in - phase with the light beam passing through the electro - optical crystal 13 on the transmission line 37. The impedance at the input end of the transmission line 37, i.e., at the signal input terminal 12a, can be adjusted by a load connected to the end of the transmission line 37, for example, connected to the signal output terminal 12c. This alternative method of implementing the impedance - matching element achieves impedance matching over a wide frequency range, but does not provide resonant enhancement of the input signal.

[0069] At the boundary of the printed circuit board 40, the connector 45 is also connected to the transmission line 41 and the ground pattern 42. The connector 45 is used to supply a modulation signal to the electro-optic modulator 1. Any type of connector suitable for the corresponding signal frequency can be used. Preferably, the connector is a coaxial connector, such as a BNC connector or an SMA connector.

[0070] The printed circuit board can be a double-sided European card defined in IEC-60297-3 or a related IEEE standard, or any other form of printed circuit board with wiring layers on one or both sides, or a multi-layer printed circuit board. It can be designed for through-hole technology and / or surface-mount technology.

[0071] In operation, a light beam, such as a laser beam, is provided along the optical axis A of the electro-optic modulator 1. The modulation signal is supplied to the signal input lead 12a of the electro-optic modulator 1 through the connector 45 and the transmission line 41. Inside the electro-optic modulator 1, the signal is amplified by the resonant element and applied to the electrodes of the crystal 13. According to the amplified modulation signal, the refractive index of the crystal 13 changes, and the light beam is modulated accordingly.

[0072] The printed circuit board 40 shown in the figure is only an example. Other electronic, optoelectronic, and optical components, such as signal generators, laser drivers, and lasers, as well as mirrors, prisms, and / or lenses, can also be integrated on the printed circuit board. Among them, the optical axes of the laser and the optical receiver are aligned with the optical axis A of the electro-optic modulator 1, so as to achieve free-space propagation of the laser beam from the laser to the crystal 13, and free-space propagation of the modulated laser beam from the crystal 13 to the optical receiver. In this way, the electro-optic modulator 1 can be easily integrated with other components of the electro-optic system on the same printed circuit board. Through its optical window, the electro-optic modulator is well adapted to the free-space propagation of the laser, which is most suitable for such airborne electro-optic systems. For many applications, this provides a space-saving and easy-to-manufacture solution.

[0073] FIG. 7 shows a schematic diagram of an electro-optic modulator according to another embodiment of the present invention, in which Figure 7a a schematic top view is shown, Figure 7b a schematic front view is shown, Figure 7c a schematic side view is shown, and Figure 7e a schematic bottom view is shown.

[0074] In this example, the housing 80 is not a standard package for electronic components, but a customer-customized housing. It is preferably made of metal. Similar to the housing 10 shown in FIG. 2, the housing 80 has an opening 81 formed on its front side to allow the light beam to enter the electro-optic crystal (and another opening formed on its rear side is not shown in the figure to allow the light beam to leave the housing).

[0075] The housing also has connection elements 82 for connecting the housing 80 to a printed circuit board. The connection elements 82 are formed as grooves in the metal housing and are adapted to receive solder for mounting the housing on the printed circuit board. One of the connection elements 82 is electrically insulated from the metal housing (in a specific example by an opening 83 in the housing 80). At the top of the housing 80, an (optional) opening 84 is provided for enabling the resonant frequency to be adjusted from the outside. At the bottom of the housing 80, a bottom metallization 85 is provided for soldering the housing 80 to the printed circuit board.

[0076] Figure 7d A schematic pad pattern to be provided on the printed circuit board is shown. Pads 87 are provided for soldering to the connection elements 82, and a metallization 88 is provided for soldering to the bottom metallization 85.

[0077] Any other housing suitable for integration on a printed circuit board can be used.

[0078] In the above embodiment, the electro - optical modulator 1 is described as a separate component having a housing that houses a plurality of components. Alternatively, components of the electro - optical modulator 1, such as the crystal 13 and the resonant element 23, can also be directly mounted on the printed circuit board 40 or 100 and covered by a cover housing. Thus, the separate substrate 20 within the electro - optical modulator 1 is no longer required, since the printed circuit board 40 or 100 has the function of the substrate 20. As the housing in the above embodiment, the cover housing can be made of metal to ensure that the electromagnetic radiation generated within the package is effectively shielded.

[0079] The electro - optical modulator according to the invention is suitable for integration into such an optoelectronic system, since it meets the requirements regarding size and electromagnetic compatibility (EMC). Regarding electromagnetic compatibility, it provides shielding of the components themselves as well as impedance matching to avoid signal back - reflection on the printed circuit board.

[0080] Wherein, the electro - optical modulator according to the invention has the following characteristics:

[0081] While a standard - sized electro - optical modulator has dimensions of approximately 40×40 mm 3 the electro - optical modulator according to the invention has dimensions comparable to other components of the system. The internal structure of the modulator, i.e., the way the individual components are arranged within the housing and connected to each other, is very flexible. In principle, such an electro - optical modulator can be implemented in the form of any standard package for electronic devices.

[0082] All the elements required for a fully - functional electro - optical modulator, i.e., the electro - optical crystal, the resonant and / or impedance - matching circuits, and the wiring pattern connecting the individual components, are integrated in a compact package that provides electromagnetic shielding and is comparable in size to other electronic and optoelectronic components integrated on the same printed circuit board.

[0083] A sufficiently large optical aperture is ensured because a bulk crystal with a cross-sectional dimension comparable to the collimated laser beam width desired for an airborne electro-optical system is used instead of an integrated optical waveguide. In addition, alignment requirements are significantly reduced compared to fiber optic solutions.

[0084] By using a resonant element, the modulation efficiency is greatly improved. The experimental setup increased the efficiency by up to 400. This means that the same effect can be achieved with only 2.5 V instead of 1 kV. However, this improvement strongly depends on the frequency.

[0085] Due to impedance matching, only a small fraction or no signal supplied to the signal input terminal is reflected, which may affect noise-sensitive components arranged on a printed circuit board, such as lasers, microcontrollers, and photodetectors. Therefore, good electromagnetic compatibility can be achieved. In addition, by using a metal housing that acts as a Faraday cage, proper shielding of the inside of the electro-optic modulator from the outside can be achieved. On the other hand, even if the signal line is used as an antenna, the magnitude of the signal on this line is greatly reduced due to resonance enhancement, so that the emission from this line is also significantly reduced, further improving electromagnetic compatibility.

[0086] The arrangement of the entire electro-optic modulator within a housing configured to be integrated on a printed circuit board allows for easy manipulation of the device. Due to the use of a bulk crystal and an optical window, complex fiber optic connections and adjustments are not required. The housing also makes the device robust and protects its contents from damage.

[0087] The electro-optic modulator according to the present invention is suitable for a large application spectrum: depending on the resonant element used, a modulation frequency of up to 20 GHz can be achieved. By using a suitable crystal material, a wide range of wavelengths can be covered. Due to the use of a bulk crystal, a sufficiently high optical power for most applications can be handled.

[0088] Of course, the present invention can be applied to a wider range of applications than quantum technology, which is described as an exemplary application in the background art section of this specification.

Claims

1. A printed circuit board (40, 100), comprising means (1) for modulating the physical properties of a light beam in response to an electrical signal, said means (1) comprising: At least one light modulation element (13) capable of modulating the physical properties of a light beam in response to an electrical signal, wherein said light modulation element comprises a bulk crystal formed as a separate monolithic free - space crystal, and A housing (10) enclosing said at least one light modulation element (13), Wherein said housing (10) and said at least one light modulation element (13) are integrally and fixedly attached to said printed circuit board (40, 100).

2. The printed circuit board according to claim 1, wherein Said housing (10) is a casing for accommodating said at least one light modulation element (13).

3. The printed circuit board according to claim 2, wherein, Said casing is a standard through - hole package or surface - mount package used in electronic devices, or said casing is a metal casing.

4. The printed circuit board according to claim 2, further comprising an insulating substrate (20, 30), wherein Said at least one light modulation element (13) is attached to said insulating substrate (20, 30), and Said insulating substrate and said at least one light modulation element (13) are accommodated within said casing.

5. The printed circuit board according to claim 4, wherein, Said insulating substrate (20, 30) is made of a ceramic material.

6. The printed circuit board according to claim 1, wherein Said at least one light modulation element (13) is mounted on said printed circuit board (40, 100), and Said housing (10) is mounted on said printed circuit board (40, 100) in a manner that encloses said at least one light modulation element (13).

7. The printed circuit board according to claim 6, wherein, Said housing is a metal housing.

8. The printed circuit board according to claim 1 or 2, wherein said housing (10) comprises: A light input window (11a) configured to allow a light beam from the outside to be guided to the input surface of said light modulation element (13), and A light output window (11b) configured to allow a light beam leaving the output surface of said light modulation element (13) to be transmitted to the outside.

9. The printed circuit board according to claim 1 or 2, further comprising a signal input terminal (12a) for receiving an electrical signal for modulating the physical properties of said light beam, Among them, The input impedance of said signal input terminal (12a) matches the characteristic impedance of a signal line formed on said printed circuit board (40, 100), or matches a characteristic impedance defined for the frequency range of said electrical signal.

10. The printed circuit board according to claim 9, wherein said input impedance is 50Ω, 75Ω or 600Ω.

11. The printed circuit board according to claim 1, further comprising a first resonant element (23) and / or a second resonant element (33), said first resonant element and second resonant element having a resonant frequency and configured to provide a signal to said light modulation element (13) having an amplitude greater than the amplitude of an electrical signal for modulating the physical properties of said light beam at said resonant frequency.

12. The printed circuit board according to claim 11, wherein Said first resonant element (23) and second resonant element (33) are enclosed by said housing (10) and / or The device further includes a signal input terminal (12a) for receiving an electrical signal for modulating a physical property of the light beam, and the first resonant element (23) and the second resonant element (33) serve as impedance matching elements for matching the input impedance of the signal input terminal (12a) with the characteristic impedance of a signal line formed on the printed circuit board (40, 100), or with a characteristic impedance defined for the frequency range of the electrical signal.

13. The printed circuit board according to claim 11 or 12, further comprising a first wiring pattern (22) and / or a second wiring pattern (32) formed on the printed circuit board (40, 100) or on an insulating substrate (20) of the device, wherein the first resonant element (23) is mounted on the first wiring pattern (22) and / or the second resonant element (33) is formed by a plurality of portions of the second wiring pattern (32).

14. The printed circuit board according to claim 11 or 12, wherein the resonant frequencies of the first resonant element (23) and the second resonant element (33) are adjustable.

15. The printed circuit board according to claim 1 or 2, further comprising a traveling wave element (37) configured to provide an electrical signal for modulating a physical property of the light beam to the optical modulation element (13), wherein the traveling wave element (37) is enclosed by the housing (10) and / or the device further includes a signal input terminal (12a) for receiving the electrical signal for modulating a physical property of the light beam, and the traveling wave element (37) serves as an impedance matching element for matching the input impedance of the signal input terminal (12a) with the characteristic impedance of a signal line formed on the printed circuit board (40, 100), or with a characteristic impedance defined for the frequency range of the electrical signal.

16. The printed circuit board according to claim 1 or 2, including at least one electro-optic modulator (1), wherein the electro-optic modulator includes a crystal (13) made of a material having an electro-optic effect, and the crystal is an optical modulation element of the device.

17. A method of manufacturing a printed circuit board (40, 100) having integrated thereon a device (1) for modulating a physical property of a light beam in response to an electrical signal, the method comprising: providing a printed circuit board (40, 100), providing a device (1) for modulating a physical property of a light beam in response to an electrical signal, the device (1) including: at least one optical modulation element (13) capable of modulating a physical property of a light beam in response to an electrical signal, wherein the optical modulation element includes a bulk crystal formed as a separate monolithic free-space crystal, and a housing (10) enclosing the at least one optical modulation element (13), integrating and fixedly attaching the housing (10) and the at least one optical modulation element (13) to the printed circuit board (40, 100).

18. The method according to claim 17, wherein The method includes integrating additional electronic, optoelectronic, and / or optical components (4, 6, 7, 8) on the printed circuit board (40, 100).

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