A device comprising a lasing component for emitting laser light

Abstract

A device comprising a lasing component for emitting laser light, a mode selection component for selectively transmitting and / or reflecting at least one mode of the emitted laser light and a detection component for detecting the at least one mode, the device comprising a casing, wherein at least two of the lasing component, the mode selection component and the detection component arranged relative to each other within the casing in a non-collinear way to direct light from the laser component into the detection component.

Description

[0001] A DEVICE COMPRISING A LASING COMPONENT FOR EMITTING LASER LIGHT

[0002] The present disclosure concerns a device comprising a lasing component for emitting laser light, with at least one random characteristic, such as, but without limitation, the one set out in appended claim 1 , and a device comprising a lasing component for emitting laser light with at least one random characteristic, such as, but without limitation, the one set out in appended claim 12.

[0003] BACKGROUND

[0004] Devices comprising lasing components for emitting laser light are known to the skilled person. Such devices are used in various systems, such as communications technology, data transmission technology, 3D sensing, and LIDAR systems.

[0005] Particularly, lasing components like vertical cavity surface emitting lasers (VCSEL) are known in the above- referred technical fields. Apart from their use in communication technology, VCSELs provide the advantage that they may also be driven to emit laser light (particularly pulses of laser light), with most of this emission focused on one of two or more distinct laser light emission patterns (sometimes also referred to as laser modes). Separation of these modes allows the amplitude or the intensity of the emitted laser light to be used to create random numbers, extending the application range of VCSELs into fields such as cryptography.

[0006] When VCSELs or other lasing components are used, especially in combination with other kinds of electronic components, it is required that the optical components comprising the VCSEL device are packaged together. This arrangement allows the isolation of the optical and the electronic sections of the VCSEL and ensure the proper arrangement of the optical components so that the lasing capabilities of the VCSEL are as desired. Likewise, it must be ensured that the respective lasing component and other components are provided with electrical energy for their functioning.

[0007] However, a proper implementation of packaging deals with plenty of different objectives, with some of those opposing each other. Examples of these challenging objectives are, for example, providing mechanical stability (as the package must withstand physical stress, whilst preserving the alignment of the optical components), enabling miniaturization (providing small form factors that enable the integration of the VCSEL device into smaller optoelectronic devices), providing thermal stability (as the package must help the heat dissipation processes to avoid overheating of the optical devices, which may degrade the performance and the lifetime of the VCSEL device), providing environmental protection (avoiding the ingress of dust, moisture, and any other contaminant that interferes with the optical process), providing optimal power supply (by distributing the electrical current required by the VCSEL components), accommodating any other component required by the VCSEL to operate, and providing the interface between the VCSEL and the rest of the optoelectronic design in which it integrates.

[0008] From both a traditional and pragmatic point of view, VCSEL integrations are naturally vertical and colinear, arranged around the axis of symmetry of the epitaxial growth. This design, characterized by the emission of laser beams perpendicular to the surface, is facilitated by the construction of a vertical resonant cavity formed between two distributed Bragg reflectors (DBRs). Such a configuration ensures a symmetric and uniform optical field, fundamental for the laser's operational efficiency and beam quality.

[0009] However, the vertical and colinear design of VCSELs has disadvantages. The design inherently limits the output power due to the finite size of the emitting surface and the cavity volume of the VCSEL itself, posing challenges for applications demanding higher power levels. Additionally, effective thermal management becomes a critical concern, as the compact structure complicates heat dissipation, potentially affecting performance and longevity. Furthermore, the fabrication process of VCSELs, requiring precise control over the multilayer structure, introduces complexity and cost. Moreover, the fixed vertical cavity offers limited tunability in terms of wavelength, which may restrict the versatility of VCSELs in certain applications.

[0010] Additionally, the packaging of VCSEL integrations mostly serves a passive role, focusing on mechanical protection and structural support. The only active roles played by the packaging relate to heat dissipation and power supply. Though essential for safeguarding and maintaining the VCSEL’s integrity, this approach limits the packaging and casing potential to a mere container, providing power, physical security, and thermal management.

[0011] Furthermore, any other active components, such as the control electronics, are also placed out of the VCSEL package device. This serves principally two purposes: on one hand, it provides modularity between the photonic and the electronic components, as these two are not placed together; on the other hand, it eases the fabrication of the components themselves, as the materials making the VCSEL device and the electronic devices are typically different, making their integration challenging, at least.

[0012] SUMMARY In view of the foregoing, an object of the present disclosure is to provide for a lasing component and a device including a lasing component and components interacting therewith, for example, for producing or outputting a signal, that preferably has reduced space requirements while achieving reliable and stable functionality of the device.

[0013] According to this disclosure, random laser light refers to any laser emission scheme in which at least one characteristic or performance component of the laser light includes uncertainty. Examples of these performance components or qualities include, but are not limited to, one or more of: polarization, average light intensity, phase, mode distribution, and frequency distribution. In some embodiments, the uncertainty of at least one of the qualities has a quantum origin.

[0014] In the context of the present disclosure, a mode of laser light encompasses at least one distinguishable physical or operational characteristic of laser light, including but not limited to polarization, frequency or frequency region, wavelength or wavelength region, spatial distribution, temporal properties (such as pulse duration and repetition rate), and / or modulation (amplitude or phase), based on which constituent components or characteristics of the laser light may be differentiated or independently described.

[0015] According to an embodiment of the disclosure, a device is provided, the device comprising a lasing component for emitting random laser light, a mode selection component for selectively transmitting and / or reflecting at least one mode of the emitted random laser light, and a detection component for detecting the at least one mode, the device comprising a casing, wherein the lasing component, the mode selection component, and the detection component are not collinearly arranged relative to their axes of symmetry within the casing.

[0016] According to this disclosure, collinear arrangement refers to a configuration where the geometric center (the arithmetic mean position of all the points in a surface) of all elements lie in the same straight line or substantially lie in the same straight line (i.e. , the geometric center of all elements in close proximity to the same straight line). Additionally, collinearly arranged relative to their axes of symmetry refers to a configuration in which the straight line coincides, or substantially coincides, with the axis of symmetry of the components that comprise the device; for example, the axis of epitaxial growth in the case of wafer designs. Examples of non-collinear arrangements include, but are not limited to, those in which the lasing component, the mode selection component, and the detection component are not arranged in a straight line.

[0017] In some embodiments, the lasing component comprises any component that is adapted for emitting laser light. In preferred embodiments, the lasing component is adapted for emitting random laser light, including (but not limited to) pulsed light. For instance, the random performance component or quality includes, in some embodiments, random energy distribution in distinct laser modes, a random polarization, or a combination of both effects. In preferred embodiments, the lasing component is a lasing component that is adapted to and is driven to emit laser pulses, where the laser pulses have at least one quality (polarization, phase, amplitude, frequency distribution, or the like) that is random for each pulse. In some embodiments, the lasing component is a VCSEL, preferably driven in pulsed mode.

[0018] The mode selection component is not restricted in any way as long as it allows for separating the modes of the received laser light. In some embodiments, the mode selection component causes different propagation directions of different modes of incident laser light emitted by the lasing component or causes one or more modes to be dampened while one or more other modes pass the mode selection component.

[0019] The detection component is adapted to detect light emitted from the mode selection component. As a non-limiting example, in some embodiments, the detection component comprises at least a photodetector.

[0020] The casing is not restricted in any way, as long as its dimensions are such that they allow for encompassing at least two components but preferably do not to occupy more space or much more space than is required by these at least two components. In some embodiments, these at least two components includes two or more of: lasing component, detection component and mode selection component. As non-limiting examples, the casing has an internal volume that is larger than the sum of the volumes of the components inside it but smaller than two times or smaller than three times or smaller than four times the aggregated volume of the components arranged within the casing. As non-limiting examples, the casing has a surface that is larger than the sum of the surfaces of the components inside it but smaller than two times or smaller than three times or smaller than four times the aggregated surface of the components arranged within the casing.

[0021] In some embodiments, the casing comprises at least a gas-tight casing, and a gas, for instance an isolating gas such as for example Neon or alike. Said gas-tight casing including said at least two components is configured not to exchange gas - such with the surrounding environment. In some embodiments, the casing comprises at least a fluid-tight casing, realized so that no fluids pass through the boundary surfaces of the casing.

[0022] In some embodiments, the casing comprises at least one electrical contact for connecting at least one of the at least two components with a source of electrical power or outputting electrical signals. In some embodiments, one or more contacts for contacting the casing with a cooling system are provided, where these contacts facilitate heat transfer from inside the casing or the casing to the cooling system.

[0023] In some embodiments, at least one of the lasing component, the mode selection component, and the detection component are integrated on a semiconductor unit arranged within the casing or forming part of the casing.

[0024] In some embodiments, the semiconductor unit comprises a wafer. By placing the semiconductor unit within the casing or by realizing the device so that the semiconductor unit forms part of the casing, manufacturing of the device is simplified while at the same time achieving reliable integration of the components.

[0025] In some preferred embodiments at least a section of the casing includes part of the mode selection function and component. For instance, in a preferred embodiment a section of the casing is the mode selection component. In some embodiments, the mode selection component is integrated partially or totally as part of the casing. In some embodiments, this provides further miniaturization of the device.

[0026] In some embodiments, the mode selection component is arranged, in propagation direction of light from the lasing component to the detection component, between the lasing component and the detection component, and the propagation direction is a straight line, different from that of the collinear axis. In such embodiments, the three components are arranged beside each other. This further enhances miniaturization of the device and allows for easier manufacturing. Additionally, also feedback effects to the laser component are limited or even avoided.

[0027] In some embodiments a propagation direction of light from the lasing component to the mode selection component is different from a propagation direction of light from the mode selection component to the detection component. Thereby, the space inside the casing is used more efficiently as the components are stacked at least partially overlapping. Additionally, also feedback effects to the laser component are limited or even avoided.

[0028] In some embodiments, the mode selection component comprises at least one grating, wherein, optionally, the grating is formed integrally with the casing. A grating is a realization of a mode selection component. In some embodiments, the grating is miniaturized to a certain extent, thereby reducing the space requirements of the device. The casing comprises in some embodiments a reflective surface for reflecting light from the lasing component in a direction towards the mode selection component. The casing in these embodiments interacts with the laser light, thereby reducing the number of components that must be provided separately.

[0029] In some embodiments, the mode selection component comprises a waveguide for guiding light from the lasing component to the detection component. The waveguide extends from an output region of the lasing component to a receiving region of the detection component, thereby determining a path of the laser light or at least one mode of the laser light that takes from emission to detection. By including such a waveguide in some embodiments, the reliability of laser light output and detection is improved.

[0030] In some examples of the disclosure, the waveguide is a polarizing waveguide that is adapted to guide the at least one mode of the emitted laser light to the detection component and to not guide at least one other mode of the emitted laser light to the detection component. In these embodiments, the propagation of the laser light is directly connected with mode separation so that the number of distinct components of the device is reduced.

[0031] In some embodiments, the mode selection component comprises miniaturized optical components. Examples of these include, but are not limited to, one or more polarizers, one or more prisms, one or more mirrors, etc. In these embodiments, the manufacturing of the device is simplified, thereby reducing its costs.

[0032] The lasing component, the mode selection component and the detection component are fixedly arranged relative to each other within the casing in one or more preferred embodiments of the disclosure as described throughout this document.

[0033] According to the disclosure, there is further provided a device comprising a lasing component for emitting, random laser light, a mode selection component for selectively transmitting and / or reflecting at least one mode of the emitted laser light and a detection component for detecting the at least one mode, wherein at least two of the lasing component, the mode selection component and the detection component are integrated on a semiconductor unit.

[0034] A semiconductor unit includes, for example, a wafer from which the lasing component and / or any of the detection component and the mode selection component are manufactured. Preferably in some embodiments, at least one of two components is the lasing component, where additionally either the mode selection component or the detection component are likewise integrated on the same semiconductor wafer unit. With this, the lasing component is fixedly arranged relative to at least one other component that interacts with the laser light emitted from the lasing component, thereby achieving miniaturization and ease of control of the functionalities of the device.

[0035] In some embodiments, the lasing component, the mode selection component, and the detection component are integrated on the semiconductor unit. This device is miniaturized as far as possible, while at the same time ensuring reliable control of the functionality of the device.

[0036] In some embodiments, at least one of the detection components is integrated in the semiconductor unit together with additional electronic components, thus increasing the miniaturization of the device. Examples of these electronic components include, but are not limited to, digitizers, analog-to-digital converters, and impedance matching networks.

[0037] In some embodiments, at least one of the lasing components is integrated in the semiconductor unit together with additional electronic components, thus increasing the miniaturization of the device. Examples of these electronic components include, but are not limited to, current sources, laser driving networks, and impedance matching networks.

[0038] In some embodiments, the lasing component comprises a Vertical Cavity Surface Emitting Laser, VCSEL. Thereby, the advantages of using VCSELs are combined with a further miniaturization of corresponding device.

[0039] In some embodiments, the device is adapted to produce an entropy signal based on the laser light output by the lasing component and by the light detected by the detection component. With this, an integrated and miniaturized entropy source is provided. Nonlimiting examples of this in the form of a system on a chip, which allows for multitude applications.

[0040] Brief description of the drawings

[0041] Figure 1 shows a schematic depiction of a device according to some embodiments

[0042] Figure 2 shows an embodiment of the device

[0043] Figure 3 shows an embodiment of the device with a reflective part of the casing

[0044] Figure 4 shows an embodiment of the device with a tilted part of the casing

[0045] Figure 5 shows an embodiment of the device with a mode selection component comprising a grating Figure 6 shows an embodiment of the device with a mode selection component comprising a polarizer and a prism

[0046] Figure 7 shows an embodiment of the device comprising a mode selection component with a waveguide

[0047] Figure 8 shows an embodiment of a device comprising a vertical surface cavity emitting laser integrated with a polarization filter

[0048] Figure 9 shows an embodiment of a device comprising a vertical cavity surface emitting laser integrated with a polarization filter and a photo detector

[0049] DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0050] Figure 1 shows a general schematic depiction of a device 100 according to some embodiments of the present disclosure.

[0051] The device 100 comprises a lasing component 101. This lasing component comprises any component that is adapted to emit laser light. As a non-limiting example, the lasing component comprises one or more laser diodes or any other sources of laser light. In preferred embodiments, the lasing component 101 comprises a vertical cavity surface emitting laser (VCSEL).

[0052] The device 100 further comprises a mode selection component 102. The mode selection component 102 is arranged so that the light emitted from the lasing component propagates to the mode selection component before it propagates to the detection component 103 described further below. The mode selection component 102 is realized to selectively transmit and / or reflect at least one mode of the emitted laser light whereas at least one other mode of the emitted laser light is either not transmitted and / or not reflected in the manner as the laser mode previously mentioned is transmitted or reflected. Thereby, preferably the laser light propagating from the mode selection component to the detection component is only comprised of a main mode whereas any other mode of the laser light is damped out or propagates in a different direction. By a main mode it is meant a mode where its associated light power is sufficiently larger than that of any other mode. For instance, and without any limiting purpose, such power of a main mode might be at least 10% larger, at least 50% larger, at least 100% larger, at least 1000% larger or alike. In a decibel (dB) scale, a power difference between a main mode and other modes might be equal or larger to 1 dB, 3dB, 6 dB, 10 dB, 20 dB, 30 dB and beyond. Examples of suitable mode selection components include, but are not limited to, gratings or polarizers (either circular or linear) that allow for separating particular modes of laser light.

[0053] In propagation direction of the at least one mode mentioned previously, the device comprises a detection component 103 for detecting the respective mode. In some embodiments, the detection component outputs a signal based on at least one quality of the detected mode. Examples of these qualities include, but are not limited to, mode power, intensity, or energy. In some embodiments, the detection component comprises a photodetector.

[0054] According to embodiments of the disclosure, the device further comprises a casing 104. The casing 104 preferably is a casing that seals an interior space 143 from the surrounding environment, for example in a manner that is fluid-tight or gas-tight or both. Exchange of material with the outside environment is thereby prevented, thus protecting the components arranged in the casing from environmental influences. According to embodiments of the disclosure, at least two of the lasing component 101 , the mode selection component 102 and the detection component 103 are arranged inside the casing in a manner so that they are fixedly arranged relative to each other. This means that without damaging or destroying the device, at least partially, it is not possible to change the relative position of the at least two components arranged inside the casing.

[0055] In the embodiments depicted in figure 1 , the lasing component 101 and the mode selection component 102 are arranged inside the casing. In some other embodiments, the lasing component 101 and the detection component 103 are arranged inside the casing, but the mode selection component 102 is arranged outside the case. Likewise, in some other embodiments, the lasing component is arranged outside the casing, whereas the mode selection component and the detection component are arranged inside the casing.

[0056] In embodiments where at least one of the referred to three components is arranged outside the casing, the casing comprises at least one surface that is transparent to the laser light emitted by the lasing component 101.

[0057] However, in some preferred embodiments, the lasing component 101 , the mode selection component 102 and the detection component 103 are all fixedly arranged relative to each other inside the casing 104. Thereby, a reliable relative arrangement of these components is ensured and they are furthermore all secured against negative environmental influences like, for example, corrosive liquids. In some embodiments, the casing is opaque at least with respect to the laser light emitted by the lasing component. In some preferred embodiments, the casing is completely opaque for visible and / or infrared and / or UV-light. In some embodiments, the interior of the casing 104, independent of how many components there are arranged inside the casing 104, is empty or evacuated (i.e. , filled with vacuum). In some embodiments, the interior of the casing 104 is filled with gas that is at least partially transparent to at least one of the modes of the light emitted by the lasing component. Alternatively or additionally, the inside of the casing is at least partially filled with a solid material that is at least partially transparent to at least one of the modes of the light emitted by the lasing component. In some embodiments, such solid material is an at least transparent resin. In some embodiments, such filling element provides thermal dissipation capabilities; thereby improving thermal conductivity within the casing, so that thermal stress to the casing 104 itself and / or the components arranged therein is reduced as heat is reliably dissipated within either the casing 104, the outside environment, or both.

[0058] The casing is configurable from any material. In some preferred embodiments, however, non-corrosive and / or electrically insulating materials are used.

[0059] In some embodiments, the casing 104 comprises one or more electrical connections 141 that allow for connecting the casing and the lasing component and / or the detection component, to an electrical power source 151. Additionally or alternatively, in some embodiments the electrical connections 141 allow for outputting an electrical signal from inside the casing 104 to the outside. In a non-limiting example, the detection component

[0060] 103 is designed to output a signal based on the received laser light. In some embodiments, this signal comprises an electrical signal transmitted via the electrical connections 141 to other devices. Examples of these receiving devices include, but are not limited to, control units, processors, microcontrollers, and FPGAs. In some embodiments, said receiving devices further process the received electrical signal by, for example, translating the signal into a sequence of bits.

[0061] Additionally or alternatively, in some embodiments the casing 104 comprises one or more heat transmission elements 142 that allow for dissipating heat, preferably from the casing

[0062] 104 to a cooling sink 152 or cooling device 152. Thereby, heat produced by the lasing component or detection component is dissipated from inside the casing to the outer environment in a reliable manner.

[0063] While the lasing component, the mode selection component, and the detection component have been described as components that are independent from the casing 104 itself, in one or more embodiments at least one of these components is at least partially integrated with the casing itself or (at least a part of) the casing constitutes the respective component. As a non-limiting example, if the casing or at least part of the casing is provided as a semiconductor or manufactured from a semiconductor material, in some embodiments the lasing component or the detection component is manufactured as part of the casing in the manufacturing process in which the casing is formed, for example, by etching or doping portions of the original wafer or semiconductor material from which the casing is at least partially formed.

[0064] Alternatively or additionally, in some embodiments one or more of the lasing component, the mode selection component, and the detection component is manufactured independently from the casing and later on assembled together with the casing to form the device 100. In some embodiments, at least one of these components is connected with the casing 104 by means of one or more connecting elements, not shown in figure 1. In some embodiments, the connecting elements have at least the function of establishing of a physical connection of the lasing component with at least part of the casing. Alternatively or additionally, in some embodiments the connecting elements have at least the function of providing power and electrical connections to at least one of the internal components inside the casing. Alternatively or additionally, in some embodiments the connecting elements have at least the function of providing heat dissipation from the component connected thereto.

[0065] Alternatively or additionally, in some embodiments at least one of the components is fixed to the casing by gluing. In some preferred embodiments, the adhesive material used for gluing the component to part of the casing has high heat conductivity, so that preferably any excess heat emitted by the component glued to the casing 104 by the adhesive material is dissipated via the adhesive material. In some preferred embodiments, the specific heat conductivity of the adhesive material is at least as high as the specific heat conductivity of the component and / or the casing, so that no heat is trapped inside the casing.

[0066] In some embodiments, the casing is fabricated from at least one of a given range of materials, including, but not limited to, metals such as stainless steel, aluminum, and titanium, which offer enhanced durability and corrosion resistance. Furthermore, in some embodiments, the casing incorporates or is entirely composed of one or more semiconducting materials, such as silicon, gallium arsenide (GaAs), indium phosphide (InP), and analogous compounds. The material(s) of such embodiments have superior electrical properties and compatibility with the manufacturing processes of electronic devices.

[0067] As shown in figure 1 , in some embodiments the device 100 is connected to a computing device 180, like a processor, which optionally comprises associated memory. In some embodiments, the detection component 103 outputs an electrical signal based on the received laser light from the lasing component 101 and this signal is transferred to the computing device for detection and optionally further processing.

[0068] Preferably the device 100 according to any of the described embodiments, also including the embodiments of figures 8 and 9, is adapted in several embodiments to produce an entropy signal based on the laser light output by the lasing component and / or by the light detected by the detection component. For example, in those embodiments where the lasing component 101 is realized as a VCSEL and is driven in pulse mode, the lasing component will arbitrarily emit a laser pulse in one of two specific distinct laser modes where, without loss of generality, it is assumed that most of the energy of the laser pulse is provided in one of the distinct laser modes. As it is impossible to predicted which of the modes will actually carry the energy of the laser pulse, it is possible to obtain a truly random signal by the detection component 103 because the detection component will either detect (a mode of) the laser pulse if the mode propagates through the mode selection component or will not detect the laser pulse if the mode does not propagate through the mode selection component.

[0069] The detection component 103 will thus output either no signal or an electrical signal corresponding to the detected amount of energy to the computing device 180. In some embodiments, the received electrical signal is binarized by, for example, comparing the received electrical signal against a threshold value using a subtractor or corresponding component. As a non-limiting example, if the received electrical signal is above the threshold value, a bit with a first state, e.g. value 1 is output, whereas if the signal is below the threshold value, a bit with a second state, e.g. value 0 is output; thus generating a random bit stream. These embodiments enable the usage of some disclosed embodiments in applications that require access to an entropy source. Such applications include, but are not limited to, cryptography, secure communications, and random number generation.

[0070] Some of the embodiments in the present disclosure facilitate the miniaturization of components necessary for processing laser signals, especially random laser pulses. This advancement enables simpler manufacturing processes for the device and broadens its applicability across numerous fields. Examples of these integrations include, but are not limited to, a system on a chip, complete with predetermined connections for interfaces such as printed circuit boards. This design feature simplifies the integration of the device into existing devices, enhancing its versatility and ease of adoption. The embodiments described in relation to Figures 2 to 7 show different realizations of the device and specifically the mode selection component. In these embodiments, all three components, i.e. the lasing component 101 , the mode selection component 102, and the detection component 103, are shown to be provided inside the casing 104. This, however, is not to be understood as limiting the disclosure, as in those embodiments, the alignment between the three elements is not collinear. Apart from that, the embodiments explained in relation to figures 2 to 7 are combinable with any of the embodiments discussed in relation to figure 1 .

[0071] Figure 2 shows an embodiment of a device 200. The mode selection component 202 is arranged inside the casing 204, with the mode selection component being arranged, in propagation direction of the laser light from the lasing component 201 to the detection component 203, between the lasing component 201 and the detection component 203. In some embodiments, the propagation direction of laser light is a straight line, which does not necessarily have to be perpendicular to a plane of the mode selection component, but the mode selection component is arranged so that the laser light, when propagating from the lasing component 201 to the detection component 203, passes the mode selection component 202.

[0072] As a non-limiting example, in the embodiment shown in figure 2, the mode selection component 202 comprises a polarization filter, like a linear polarization filter or a circular polarization filter, as is as such known in the art. Laser light passing the mode selection component 202 will thus be filtered depending on the characteristics of the mode selection component 202 so that preferably at least one mode of laser light passes the mode selection component 202 and propagates to the detection component 203 and at least one mode of laser light does not pass the mode selection component 202 and / or is redirected so that it does not propagate to the detection component 202. In some embodiments, as is further shown in figure 2 and as was already explained above, the lasing component 201 and / or the detection component 203 are connected via connecting means 211 and 231 , respectively, with the casing, so as to establish electrical and / or thermal connections to components that are arranged preferably outside of the casing.

[0073] As a non-limiting example, in the embodiment of figure 2, the mode selection component is realized so as to allow transmission of a first mode of laser light and block or reflect a second mode of laser, so that only one of these at least two modes propagates through the mode selection component 202 to the detection component. In this context, laser light 251 emitted from the laser component in the direction of the mode selection component is filtered (including redirection compared to another mode) so that only one specific mode or only a plurality of specific modes is transmitted through the mode selection component 202 as modes 252 in the direction of the detection component 203, where they are detected. This embodiment is particularly advantageous if the lasing component 201 is realized, for example, as a VCSEL. Such lasers generally emit laser light in two distinct modes, where usually the full energy or almost the full energy of a given laser pulse is emitted in one of the modes. By separating the emitted laser light according to these two modes using the mode selection component 202, it is ensured that irrespective of the mode in which the VCSEL emits the laser light for a given pulse, only laser light with a predetermined mode will reach the detection component. With this, it is possible to generate random numbers as it is uncertain, due to the laws of quantum mechanics, in which mode the VCSEL will emit laser light.

[0074] Figure 3 shows a further embodiment of a device 300. In this embodiment, two of the components 302, 303 are stacked together. The casing 304 comprises a reflective element 341 , like for example a metallic lid or a lid that has a reflective coating. In the embodiment of figure 3, the mode selection component 302 and the detection component 303 are stacked together, whereas the lasing component 301 is arranged beside these stacked components. Laser light 351 emitted from the lasing component 301 is reflected by the reflective element 341 as laser light 352 in the direction of the mode selection component 302. The mode selection component then filters the incident laser light 352 as explained above, so that only one or a plurality of predetermined modes of the incident laser light propagate further to the detection component 303, whereas other modes are blocked or propagated in a different direction.

[0075] In this embodiment, additionally, the separation between the lasing component and the mode selection component reduces the effect of feedback dynamics, in which the mode selector partially reflects the laser light back into the cavity, inducing additional dynamics into the laser cavity. This fact could compromise the quality of the VCSEL scheme for applications such as random number generation, as the light coming back into the cavity would induce autocorrelations between the cavity configurations at different times, which translate into autocorrelations in the generated bit stream, resulting in predictable patterns, which are totally undesirable in the case of a random number generator. Additionally, these feedback effects reduce the stability of the VCSEL, when considered as a dynamical system, making it harder to control in the long-term. By non-stacking the laser component and the mode selection component, we reduce or even suppress these feedback dynamics.

[0076] However, in contrast to the stacking as described in relation to figure 3, in some embodiments the stack lasing component 301 and the mode selection component 302 are stacked together, with the detector component 303 non-stacked with them, so that the laser light 351 , 352 comprise those modes of laser light that pass the mode selection component 302.

[0077] In some embodiments, the reflective element 341 is coated or comprises an at least partially reflective material. Examples of these materials include, but are not limited to, stainless steel or polished silicon. In some embodiments, the material of the reflective element 341 is different from the material of the rest of the casing 341 . For some of those embodiments, the reflective element 341 and the remainder of the casing 304 are glued together or otherwise fixedly connected with each other, so that preferably a gas-tight and / or fluid-tight connection is established and the casing tightly seals the interior from the outside environment.

[0078] In the embodiment of figure 3, the reflective surface 341 is a plain surface that is, for example, in parallel to a ground surface of the casing on which the lasing component 301 is arranged and / or that is parallel to an emitting surface of the lasing component. These embodiments are easy to manufacture, but provide for a comparably large lower limit of extension of the casing in a horizontal direction, as depicted in figure 3. By parallel it is meant substantially parallel, in practice within the tolerance of available manufacturing techniques.

[0079] Figure 4 shows an embodiment that is an alternative to the embodiment of figure 3, where the reflective element 441 comprises an inclined reflective surface with respect to a ground surface of the casing 404 or a surface of the lasing component 401 emitting laser light. Examples of these tilting angles include, but are not limited to, 1°, 5°, 10°, 15°, and 20°.

[0080] By inclining the reflective surface 441 , it is possible to change the angle under which light incident on the reflective surface further propagates. While the inclination of the reflective surface is shown here so that the reflective surface has a distance to a ground surface of the casing (surface opposite the reflective surface) that increases when moving from one end to the opposite end (e.g. from 401 to 403, from lasing component to detector component, left to right in the drawing of viceversa). In some embodiments, the distance of the reflective surface to the ground surface of the casing decreases in the opposite direction.

[0081] Additionally, by inclining the reflective surface 441 , it is possible to avoid that the reflections coming from the casing come back to the laser cavity itself, as the reflections no longer come back through the same path as the transmitted laser light due to the geometry of the device. Furthermore, by inclining the reflective surface 441 , we avoid unwanted optical feedbacks from the reflections into the cavity, which could compromise the quality of the VCSEL scheme for applications such as random number generation, as the light coming back into the cavity would induce autocorrelations between the cavity configurations at different times, which translate into autocorrelations in the generated bit stream, resulting in predictable patterns, which are totally undesirable in the case of a random number generator. Additionally, these feedback effects reduce the stability of the VCSEL, when considered as a dynamical system, making it harder to control in the long-term. Tilting the reflective surface 441 reduces or even removes these reflections, therefore reducing or even removing these feedback effects.

[0082] Furthermore, by tilting the reflective surface 441 , we also avoid any unwanted mode misalignments, which may arise when feedback light gets into the laser cavity and interferes with the mode distributions, generating spurious modes and potentially reducing the efficiency of the laser mode of interest. As a non-limiting example, the presence of these imperious modes impacts the quality of the random numbers being digitized, as any reduction in intensity on the modes of interest results in a lower signal-to-noise ratio once these laser beams are digitized, therefore potentially reducing the quality metrics of the generated bitstream, including (but not limited to) the estimation of the entropy bounds. By avoiding these mode misalignments, we reduce these mode interferences and, therefore, avoid any further impact on the quality metrics of the digitization process.

[0083] In some embodiments, the reflective surface 441 comprises a curvature. In some embodiments, this allows for further reducing the horizontal extension of the casing so as to miniaturize the device further by controlling the propagation of light in the horizontal direction.

[0084] As explained in relation to figure 3, in some embodiments the reflective surface 441 comprises a coated surface of the casing 404. In some embodiments, the reflective surface 441 is a separate component that consists of or comprises a reflective material. In this context, the same embodiments for connecting such a separate component with the remainder of the casing as explained in relation to figure 3 apply in the embodiments described in relation to figure 4.

[0085] In the embodiment of figure 5, the mode selection component 502 comprises a grating or the mode selection component 502 is realized in the form of a grating. Such gratings have the advantage of frequency or wavelength dependent reflection so that depending on the frequency of the incident laser modes 551 , the transmission angle of the laser modes 552 that are transmitted from the grating 502 change. Thereby, in some embodiments the grating is used to control that only a given mode or particular modes 552 propagate further to the detection component 503 and are detected by the detection component 503, whereas other modes that are transmitted from the grating 502 under a different angle do not reach the detection component 503.

[0086] In this embodiment, the mode selection component 502 is preferably arranged on a surface of the casing 504 that is opposite to a surface on which the lasing component 501 and the detection component 503 are arranged.

[0087] While in the embodiment of figure 5, the mode selection component 502 comprises a grating that is fixed on an interior surface of the casing 504, in some embodiments the grating is realized as part of or integral with the casing 504. In some embodiments, the grating is formed when producing the respective surface of the casing. Thereby, the grating and the casing are made from the same material and there is no further connecting means connecting the grating to the casing. In some embodiments in which the grating is an integral part of the casing, the mode selection component 502 comprises the casing or a part of the casing. As a non-limiting example, in figure 5 it comprises the surface comprising the grating.

[0088] In the embodiment of figure 6, the mode selection component 602 comprises at least one prism 621 and 623 and a linear polarizer 622 that are arranged so that light emitted from the lasing component 601 propagates through the at least one prism and the linear polarizer. Due to the prism causing different propagation directions for different frequencies of light and the linear polarizer further selecting particularly linearly polarized portions of incident light, in some embodiments laser modes emitted from the lasing component 601 are selectively propagated to the detection component depending on both their frequency and their (linear) polarization, thereby allowing for improved mode selection.

[0089] Like for the embodiment of figure 5, for some embodiments the mode selection component, including the at least one prism and the linear polarizer, is arranged on an opposite surface of the casing compared to the surface where the lasing component 601 and the detection component 603 are arranged.

[0090] In the embodiment of figure 7, the mode selection component 702 comprises a waveguide 721. In some embodiments, the waveguide is arranged so that laser light emitted from the lasing component 701 propagates through the waveguide 721 to the detection component 703. Thereby intensity losses and internal reflection inside the casing 704 are reduced, allowing for a highly accurate detection of the laser light at the detection component 703. In order to achieve mode selection, in some embodiments the mode selection component 702 either comprises a polarizer 722 within the waveguide 721 through which the laser light has to pass from the lasing component 701 to the detection component 703. In some embodiments of the configuration of Fig.7, a mode selection element 722 is stacked adjacent to (e.g., underneath) at least one of a laser light component 701 or a photodetector 703.

[0091] Alternatively, in some embodiments, the waveguide 721 is provided as a polarizing waveguide or comprises a portion that acts as a polarizing waveguide so that laser modes propagating through the waveguide are damped out or selectively guided through the waveguide to detection component 703. In these embodiments, reliable mode selection and reliable relative arrangement of the lasing component 701 , the mode selection component 702 and the detection component 703 is achieved.

[0092] In some embodiments, the waveguide (irrespective of whether it is a polarizing waveguide or a waveguide with an integrated polarizer) is manufactured as part of the casing or integral with the casing, thus allowing in some embodiments the reduction of the number of separate components and / or the number of separate manufacturing steps.

[0093] Figure 8 shows an embodiment of a device according to the present disclosure that is different to the embodiments described in relation to figures 1 to 7. In this embodiment, the lasing component 801 is integrally formed with a mode selection component 802, preferably on a semiconductor substrate 803. In some embodiments, lasing component 801 comprises an active region 811 that is connected to contacts 814 and 815 that provide electrical energy to the active region 811 so as to excite the active region 811 to transmit light. On opposing surfaces of the active region 811 , the lasing component 801 comprises reflective mirrors 812 and 813, where the reflective mirror 813 is preferably fully reflective and the reflective mirror 812 is only partially reflective so that lasing is obtained in the direction of the mode selection component 802. The mode selection component, in this embodiment, preferably is or comprises a polarizer (including, but not limited to, linear polarizers) that filters at least one mode and allows for transmission of at least one other mode of the laser light.

[0094] With this integrated or stack arrangement, creation of laser light and simultaneous mode selection is obtained so that laser light 851 emitted from the active region 811 in the direction of the mode selection component is filtered so that at least one predefined laser mode 852 leaves the stacked arrangement preferably in a direction of a detection component 850. This detection component is, in this embodiment, not provided as part of the stack arrangement but as part of the device and, in some embodiments, is encased with the stack arrangement in a casing (not shown).

[0095] This embodiment of the device provides for easier manufacture of the components of the device because, in some embodiments, the mode selection component and the lasing component are manufactured in a single manufacturing process from a single semiconductor substrate 803.

[0096] Figure 9 shows a further embodiment of a device according to figure 8 where the lasing component 901 , the mode selection component 902 and the detection component 903 are provided as a single stacked structure on a semiconductor substrate 904.

[0097] In this embodiment the lasing component 901 again comprises an active region 911 with electrical connections 914 and 915 as well as a totally reflective mirror 912 on one side and a semi-transparent mirror 913 on the other side, where the semi-transparent mirror 913 is highly reflective but not totally reflective. On the semi-transparent mirror 913, on a side opposite to the active region 911 , the mode selection component 902 is arranged. Incident laser light 951 propagates through the mode selection component 902 and is filtered with respect to at least one mode whereas at least one other mode 952 propagates through the mode selection component 902 in the direction of the detection component 903 where it is detected and digitized to, for example, output a digital electrical signal.

[0098] This embodiment, like the embodiment of figure 1 , allows for improved manufacturing of the device as, in some particular embodiments, all components are manufactured in a single manufacturing process from a single semiconductor unit like a wafer.

[0099] For some embodiments, the integration of part of the electronics with the photonic device as in Figure 9 allows an improved efficiency of the device: for these embodiments, as the digitization is already done within the same chip, the interface to the external electronics is already digital. This reduces the effect of the noise and any parasitic effects, such as coupling to the wire bondings, on the signal: since it is digitized, the probability that these effects modify the signal is reduced. In contrast, when the digitizer is outside, the signal propagated through the wire bonding is of analog kind; thus, the effect of noise could be of a greater impact on it.

Claims

Claims1. A device comprising a lasing component for emitting laser light, a mode selection component for selectively transmitting and / or reflecting at least one mode of the emitted laser light and a detection component for detecting the at least one mode, the device comprising a casing, wherein the lasing component, the mode selection component and the detection component are arranged relative to each other within the casing in a non-collinear way to direct light from the laser component into the detection component.

2. The device according to claim 1 , wherein at least two of the lasing components, the mode selection component and the detection component are integrated on a semiconductor unit arranged within the casing or forming part of the casing.

3. The device according to claim 1 or 2, wherein a section of the casing is part of the mode selection component or wherein a section of the casing is the mode selection component.

4. The device according to any of claims 1 to 3, wherein the mode selection component is arranged, in propagation direction of light from the lasing component to the detection component, between the lasing component and the detection component, and the propagation direction is a straight line.

5. The device according to any of claims 1 to 3, wherein a propagation direction of light from the lasing component to the mode selection component is different from a propagation direction of light from the mode selection component to the detection component.

6. The device according to any of claims 1 to 5, wherein the mode selection component comprises at least one grating, wherein, optionally, the grating is formed integral with the casing.

7. The device according to any of claims 1 to 6 wherein the casing comprises a reflective surface for reflecting light from the lasing component in a direction towards the mode selection component.

8. The device according to any of claims 1 to 7, wherein the mode selection component comprises a waveguide for guiding light from the lasing component to the detection component.

9. The device according to claim 8, wherein the waveguide is a polarizing waveguide that is adapted to guide the at least one mode of the emitted laser light to the detection component and to not guide at least one other mode of the emitted laser light to the detection component.

10. The device according to claim 8, wherein the mode selection component comprises a polarizer and at least one mirror.

11. The device according to any of claims 1 to 10, wherein the lasing component, the mode selection component and the detection component are fixedly arranged relative to each other within the casing.

12. A device comprising a lasing component for emitting, preferably randomly, laser light, a mode selection component for selectively transmitting and / or reflecting at least one mode of the emitted laser light and a detection component for detecting the at least one mode, wherein at least one of the lasing component, the mode selection component and the detection component are integrated on a semiconductor unit.

13. The device according to claim 12, wherein the lasing component, the mode selection component and the detection component are integrated on the semiconductor unit, and in which the detection component is configured to generate digital signals.

14. The device according to any of claims 1 to 13, wherein the lasing component is or comprises a Vertical Cavity Surface Emitting Laser, VCSEL.

15. The device according to any of claims 1 to 14, wherein the device is adapted to produce an entropy signal based on the laser light output by the lasing component and by the light detected by the detection component.

16. A method comprising: emitting laser light with a lasing component of a device; selectively transmitting and / or reflecting at least one mode of the emitted laser light with a mode selection component of the device; detecting the selectively transmitted and / or reflected at least one mode of the emitted laser light with a detection component of the device; andarranging the device with a casing such that the lasing component, the mode selection component and the detection component are arranged relative to each other within the casing in a non-collinear way to direct light from the laser component into the detection component.

17. The method according to claim 16, wherein the device is the device according to any of claims 1-11 , 14-15.

18. A method comprising: emitting laser light with a lasing component; selectively transmitting and / or reflecting at least one mode of the emitted laser light with a mode selection component of the device; detecting the selectively transmitted and / or reflected at least one mode of the emitted laser light with a detection component of the device; and integrating at least one of the lasing component, the mode selection component and the detection component on a semiconductor unit.

19. The method according to claim 18, wherein the device is the device according to any of claims 12-15.

Images