Vacuum viewport member

Abstract

A vacuum viewport member comprising: a support body; a plurality of lenses defined by or provided on a first surface of the support body; a plurality of optical fibre receiving members defining a plurality of recesses, wherein at least an axial end of each recess of the plurality of recesses is formed by a portion of a second surface of the support body opposite to the first surface, wherein each recess of the plurality of recesses is arranged to receive an optical fibre corresponding to a respective lens of the plurality of lenses.

Description

[0001] VACUUM VIEWPORT MEMBER

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to illuminating, or collecting light from, objects within a hermetically sealed environment. In particular, but not exclusively, the invention relates to a hermetic microlens assembly.

[0004] BACKGROUND OF THE INVENTION

[0005] A refractive lens is an optical device where a shaped surface of a transparent material modifies the spatial distribution of an incident light field. A single lens, or series of lenses, is commonly used in the transference of light between two objects, one being an emissive source that radiates the light field and the other being a target object that absorbs it. The lens system acts both to delineate an optical pathway between radiation source and target, as well as adapt the radiated pattern of light into that tailored for absorption.

[0006] One application of a refractive lens device is as a sub-system within a class of quantum information processors, which are based on arrays of individual atoms, or objects which possess analogous energetic structures. Quantum information may be encoded within their electronic, nuclear, or motional states, where transitions between states are driven by the absorption or emission of coherent light fields. In general terms, any host of quantum information is referred to as a qubit, and when the type of qubit employed can emit light, it is referred to as a quantum emitter. The construction of a quantum information processor based on quantum emitters must therefore include the necessary optical componentry for routing light to and from its constituent qubits. In such systems, the radiation source may be an external laser system, directed onto the quantum emitter for state initialisation or manipulation. Or the quantum emitter itself may act as a radiation source, with optical componentry employed to route light between qubits for state mapping, or to an external detector for state analysis. As standard, such a quantum processor will possess many optical pathways to facilitate a range of quantum operations and address many qubits. As computational capability is largely driven by the number of qubits, however, there are significant challenges in creating highly compact optical systems within quantum information processors.

[0007] A major performance consideration in driving quantum emitters with laser light is the size of the focal spot at the emitter. For a given laser power, the spot size of the driving laser field on the emitter should be minimized, as to perform fast quantum state manipulations. In a system of a single refractive lens and collimated input laser source, the focused spot size on the emitter is minimised by ensuring a short distance between the lensed surface and the emitter and a large lens diameter. This gives a similar result to optimising the collection of light from the emitter, which equally requires short lens to emitter separation and large lens diameter to maximise the solid angle subtended. However, more complex considerations arise when multiple refractive lenses are required in proximity, as may be required to simultaneously address emitters with light from different lasers, address emitters from different angles of illumination, or to address spatially distinct zones of emitters in the quantum processor. Providing independent lens systems for each task is beneficial in allowing the positioning and surface profile of each to be individually optimised. However, proving multiple lensed surfaces in proximity may limit their respective diameters, preventing physical overlap, and impact performance.

[0008] A requirement to provide many closely arranged lensing surfaces around a quantum processor necessitates a complex optical system for the delivery of light to or from these lenses. In known arrangements, the delivery of light from a laser radiation source to a lens addressing a quantum processor employs several mirrored elements for beam steering. Each of these mirrors will be subject to fluctuation in position, induced by vibration, air currents or temperature shifts, creating optical misalignment. To minimise misalignment, it is therefore recommendable to minimise the optical path length of such beam steering elements. However, providing many optical pathways for the optical processor would generally necessitate a greater number of beam steering elements in proximity, thereby creating longer optical pathways. As beam steering elements usually require individual and iterative positional alignment, commissioning a complex optical delivery system can demand significant time from a trained technician.

[0009] In order to perform quantum information processing with most types of quantum emitters, they must be enclosed within a hermetically sealed environment. In general, this environment is ultra-high vacuum, where all gaseous material is expelled from the proximity of the emitter For free-space emitters, such as neutral atoms or atomic ions, this is chiefly to prevent collisions with background gas molecules, which would cause ballistic loss of the emitter from the quantum processor, or destruction of the quantum state encoded within the emitter. These detrimental effects are further mitigated by operating the system at cryogenic temperatures, which equally requires a hermetically sealed environment to prevent condensation of vaporous material, such as water, onto the cold quantum processor. Solid-state quantum emitters, such as nitrogen vacancies and quantum dots are immune from ballistic loss and therefore can be operated at standard atmospheric pressure. However, there are still significant advantages to operating at cryogenic temperatures, and therefore within a hermetic environment, where the suppression of phonons within the crystal structure preserves quantum states over longer timescales.

[0010] Operation of quantum processors at ultra-high vacuum requires the minimisation of vaporous material produced within the vacuum chamber. This requires use of a limited set of materials with inherently low outgassing rates, while minimising exposed surface area. Such constraints may prevent the use of adhesives, which expel vaporous contamination, or threaded mechanical connections, which trap gas pockets within the hermetic environment. It is therefore very challenging to install complex optical systems within a vacuum environment, such as laser systems, complex lens groups or detectors, given their nominal size and range of materials used in their construction. In known arrangements, a hermetically sealed and optically transparent glass window is included in the vacuum chamber, allowing most optical devices to be situated in standard atmosphere, while retaining optical access to the quantum processor. However, this window generally forms a key restriction in the performance of the system, by increasing the distance between the quantum emitters and optical componentry. This frustrates the minimisation of lens to emitter distance, as desired for performance optimisation, as well as complicates the design of the lensed surfaces, which must accommodate for refraction and partial reflection by the glass window.

[0011] The design and construction of vacuum chamber for quantum information processing must generally support operation at a broad range of temperatures. While continuous cryogenic operation is a common requirement, intermittent periods of high temperature operation are also employed in systems that normally operate at room-temperature, a process referred to as ‘bakeout’. Heating the chamber to high temperatures is performed to expel vaporous contaminants from the internal walls, which can be removed using vacuum pumps, such that when the chamber is cooled, improved pressures are achieved. Operability at extreme temperatures places a range of material and design constrains on the vacuum chamber. Many materials used in the construction of optical systems, such as adhesives, fail at temperatures lower than desired for bake-out Further, optical devices constructed from inhomogeneous materials, being those with different coefficients of thermal expansion (CTEs), may have significant stress induced at extreme temperatures, causing mechanical or material failure. This is most common for glass to metal connections, given the significantly lower CTE of standard glasses when compared to standard metals.

[0012] In the design and construction of complex optical systems, care must be taken to avoid stray reflections from refractive index boundaries or scattering from rough surfaces. This is particularly pertinent in the design of optical delivery systems to quantum emitters, where one must ensure both efficient transfer of radiated light to its target destination and minimise crosstalk between spatially separate emitters, as to avoid computational error. To avoid stray reflections caused by glass-to-air transitions, it is common to provide anti-reflection coatings, which are generally vacuum compatible. To avoid stray reflections caused by glass-to-glass transitions, it is common to ensure each surface is highly flat, to avoid air gaps, a process called optical contacting. If machining the glass element to such a surface quality is impractical, it is then common to use a refractive index matching liquid or adhesive to perform a similar effect. However, the use of such liquids and adhesives comes with significant challenges for vacuum integration, in managing chamber contamination and operational temperatures. Where some stray reflection is unavoidable, such as from rough surfaces within the vacuum chamber, care must be taken to avoid light unintentionally passing between optical channels. This may require restricting the acceptance angle of each lens, by adding an aperture or enclosing its associated optical pathway in non-transmissive material.

[0013] SUMMARY OF THE INVENTION

[0014] In order to mitigate for at least some of the above-described problems, there is provided: a vacuum viewport member comprising: a support body; a plurality of lenses defined by or provided on a first surface of the support body; a plurality of optical fibre receiving members defining a plurality of recesses, wherein at least an axial end of each recess of the plurality of recesses is formed by a portion of a second surface of the support body opposite to the first surface, wherein each recess of the plurality of recesses is arranged to receive an optical fibre corresponding to a respective lens of the plurality of lenses.

[0015] Advantageously, the vacuum viewport member provides a mechanically stable mechanism for the illumination and collection of light from processes performed within a hermetically sealed environment, such as in a vacuum, without requiring complex arrangements, such as those based on free-space optics and / or ultra-high vacuum feedthroughs, to deliver light into, or to collect light from, inside the vacuum environment. Further, not only does the vacuum viewport member enable a pressure differential to be formed across opposing faces of support body such that the plurality of lenses can be placed in-vacuo and optical fibres inserted ex -vacuo, but the arrangement also enables decreased separation of lenses and target objects within the vacuum environment. This in turn facilitates the use of simpler lens profiles and improved resolution and efficiency in light delivery and collection. Furthermore, the pre-defined arrangement results in a drift and maintenance-free arrangement, closer packing of components and hence improved scalability compared with known systems.

[0016] Optionally, the plurality of optical fibre receiving members and respective lenses are arranged: to direct light from optical fibres in the plurality of recesses towards one or more target positions that are predetermined relative to the first surface; and / or to direct light from one or more target positions that are predetermined relative to the first surface towards optical fibres in the plurality of recesses. Beneficially, the vacuum viewport member is commissioned and manufactured to provide compact, predefined measurement capabilities. Optionally, at least a subset of the plurality of lenses has respective optical axes pointing in different directions. Advantageously, the vacuum viewport is configured to optimise both the arrangement of apparatus in-vacuo and ex -vacuo, for example facilitating the accurate control of optical pathways close to a target object.

[0017] Optionally, the optical axes of two or more of the subset of the plurality of lenses substantially intersect with each other at one or more target positions that are predetermined relative to the first surface. Beneficially, the vacuum viewport is provided with accurately aligned optical pathways for the illumination and light collection from target objects, thereby reducing alignment burden, maintaining measurement fidelity and enabling illumination and / or light collection from multiple sources.

[0018] Optionally, the subset of the plurality of lenses has respective optical axes pointing in a direction substantially parallel to the respective longitudinal axes of a subset of the plurality of recesses. Advantageously, optical pathways can be optimised to converge at particular regions in a compact in-vacuo environment whilst making the best use of space ex-vacuo and improving light delivery / collection.

[0019] Optionally, the support body is integrally formed. Beneficially, alignment of lenses and optical fibre receiving members is achieved through processing of a single element, thereby taking advantage of high accuracy manufacture leading to low-burden plug-in optics with high integrity and fewer potential weaknesses in its capacity as a hermetic sealing member.

[0020] Optionally, the support body comprises: a first integrally formed portion comprising the plurality of lenses; and a second integrally formed portion comprising the plurality of recesses. Advantageously, different processes / and or materials can be used to form the vacuum viewport member, enabling efficient parallel processing and bespoke optimisation in the form and function of each integrally formed portion. Further, the use of distinct integrally formed portions provides increased flexibility to repair and / or replace individual portions. For example, where the second integrally formed portion is outside of a hermetically sealed environment, it has the potential to be replaced / repaired without disturbing the hermetically sealed environment.

[0021] Optionally, the first integrally formed portion comprises a mating surface opposite the first surface and the second integrally formed portion comprises a mating surface opposite the second surface, wherein the mating surface of the first integrally formed portion faces the mating surface of the second integrally formed portion. Beneficially, separate integrally formed portions can be brought together with predetermined mating surfaces based on the requirements for joining the different portions.

[0022] Optionally, the support body comprises one or more layers at least partially between the mating surface of the first integrally formed portion and the mating surface of the second integrally formed portion. Advantageously, the use of separate integrally formed portions provides flexibility in the insertion of further materials and / or layers to provide enhanced functionality in the vacuum viewport member.

[0023] Optionally, the one or more layers comprise refractive index matching material. Beneficially, the use of refractive index matching material reduces losses at the interface between different portions.

[0024] Optionally, at least part of the mating surface of the first integrally formed portion is in optical contact with at least part of the mating surface of the second integrally formed portion, thereby to reduce light scattering at the interface between the mating surface of the first integrally formed portion and the mating surface of the second integrally formed portion.

[0025] Optionally, the first integrally formed portion and / or the second integrally formed portion comprise one or more alignment features, thereby to enable alignment of the first integrally formed portion with the second integrally formed portion, optionally wherein the one or more alignment features comprise fiducial markers and / or registration features.

[0026] Optionally, the first surface comprises a coating. Optionally, the coating is an anti- reflective coating. Optionally, the coating comprises an electrically conductive material, optionally wherein the electrically conductive material forms at least part of one or more electrical circuits. Advantageously, the vacuum viewport member is provided with functionality in addition to sealing a hermetic environment whilst allowing optical access.

[0027] Optionally, the vacuum viewport member comprises optical shielding arranged to reduce optical crosstalk associated with light from different lenses of the plurality of lenses. Optionally, the optical shielding comprises one or more shielding layers at least partially between the first surface and the second surface. Optionally, the optical shielding comprises one or more trenches in the support body, optionally the one or more trenches are at least partially filled with an optical shielding material, optionally the optical shielding material comprises a metal Beneficially, optical shielding reduces noise associated with different predetermined optical pathways and can be efficiently provided at the point of manufacture of the vacuum viewport.

[0028] Optionally, the vacuum viewport member comprises a first integrally formed portion comprising a mating surface opposite the first surface and the second integrally formed portion comprising a mating surface opposite the second surface, wherein the mating surface of the first integrally formed portion faces the mating surface of the second integrally formed portion and the vacuum viewport member comprises optical shielding comprising one or more shielding layers positioned at least partially between the mating surface of the first integrally formed portion and the mating surface of the second integrally formed portion. Advantageously, the optical shielding is provided on either mating surface, both mating surfaces, or between mating surfaces, thereby providing efficient routes to optical isolation of different optical pathways through the vacuum viewport member.

[0029] Optionally, the vacuum viewport member comprises refractive index matching material at least partially within at least one of the recesses defined by at least one of the plurality of optical fibre receiving members, thereby to reduce light scattering between an optical fibre in the recess of the at least one of the plurality of recesses and the support body.

[0030] Optionally, the first surface comprises one or more location features configured to locate one or more components relative to the plurality of lenses, optionally wherein the one or more location features comprise one or more fiducial markers and / or registration features. Advantageously, high accuracy alignment is provided within a hermetically sealed environment by the vacuum viewport member acting as both a sealing member and optical component.

[0031] Optionally, the plurality of lenses comprises at least one microlens having an outermost diameter of less than or equal to 1000 microns [ further dimensions?].

[0032] Beneficially, the use of microlenses facilitates high density packing of lenses to provide improved scalability of a wide range of optical processes, such as quantum information processing.

[0033] Optionally, the plurality of lenses comprises at least one lens having a spherical profile and / or at least one lens having an aspherical profile and / or at least one lens having a Fresnel profile. Advantageously, the vacuum viewport is configured to provide illumination and / or collect light associated with different processes.

[0034] Optionally, the support body is at least partially formed from material comprising at least one of: glass, fused silica, borosilicate glass and silicon. Beneficially, the support body is formed from a material that is optically transmissive with material properties suitable for processing and use as a vacuum viewport member.

[0035] There is also provided a vacuum system comprising a vacuum chamber and the vacuum viewport member according to any preceding claim, wherein the vacuum viewport member is configured to form a hermetically sealed part of the vacuum chamber thereby to enable a pressure differential to be created between the environment within the vacuum chamber and the environment outside the vacuum chamber, wherein the first surface faces into the vacuum chamber. Advantageously, the vacuum viewport member can be integrated into a system for providing a pressure differential across the vacuum viewport member such that the vacuum viewport member facilitates processes within the system whilst providing improved means to illuminate and / or collect light from within the system.

[0036] Optionally, the vacuum system further comprises in the vacuum chamber at least one of an ion trap and an atom trap. Optionally, the plurality of optical fibre receiving members and respective lenses are arranged thereby to direct light between optical fibres in the recesses and one or more predetermined target positions within the vacuum chamber, optionally wherein the one or more predetermined target positions are associated with one or more objects, optionally wherein the one or more objects comprise: one or more trapped ions, and / or one or more neutral atoms and / or one or more trapped molecules and / or one or more point-defect lattice vacancies and / or one or more quantum dots. Advantageously, the vacuum system enables improved control and scalability of processes relating to objects on an atomic scale.

[0037] There is also provided a method of producing the viewport vacuum member, the method comprising the steps of: integrally forming the plurality of lenses in the first surface of the support body; and integrally forming the plurality of recesses in the second surface of the support body, optionally wherein integrally forming the plurality of lenses and / or the plurality of optical fibre receiving members comprises selective laser etching and / or focussed ion beam milling. Beneficially, the integral formation of the support body of the vacuum viewport member by selective laser etching and / or focussed ion beam milling and / or ablative laser processing and / or moulding and / or diamond micromilling provides precise control of a robust and elegant vacuum viewport member with improved functionality.

[0038] Further aspects of the invention will be apparent from the description and the appended claims.

[0039] DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

[0040] A detailed description of embodiments of the invention is described, by way of example only, with reference to the figures, in which:

[0041] Figures 1 to 5 show cross-sectional views of portions of vacuum viewport members with different arrangements of lenses and optical fibres;

[0042] Figure 6 shows a cross-sectional view of a portion of a monolithic vacuum viewport member;

[0043] Figures 7 to 11 show cross-sectional views of portions of multi-layer vacuum viewport members with different arrangements;

[0044] Figure 12 shows a cross-sectional view of a portion of a multi-layer vacuum viewport member with alignment features;

[0045] Figure 13 shows a cross-sectional view of a portion of a coated vacuum viewport member;

[0046] Figure 14 shows a perspective view of a portion of a vacuum viewport member comprising an electrical circuit;

[0047] Figures 15 and 16 show cross-sectional views of portions of vacuum viewport members with optical shielding; Figure 17 shows a cross-sectional view of a portion of a vacuum viewport member with improved optical properties;

[0048] Figure 18 shows a cross-sectional view of a portion of a vacuum viewport member with locating features;

[0049] Figure 19 shows a cross-sectional view of a portion of a vacuum viewport member with different lens configurations;

[0050] Figure 20 shows a perspective view of a portion of a vacuum system; and

[0051] Figure 21 shows a perspective view of a portion of a vacuum system and an ion trap within the vacuum system.

[0052] As described above, whilst it is often desirable to perform processes by illuminating, or collecting light from, objects within a hermetically sealed environment, known systems present a number of difficulties. For example, commonly, high numerical aperture (NA) lenses are placed external to a hermetic chamber, allowing illumination, or light collection, from an object within the hermetic chamber through an optically transparent window, such as a viewport having a flat glass window. Whilst the provision of optical apparatus external to the hermetically sealed environment enables control of optical pathways without disturbing components within the hermetically sealed environment, it results in a greater separation between an object being illuminated and / or detected within the hermetically sealed environment and a lens of the optical apparatus. This means that a large diameter lens is required in order to capture light efficiently, or to illuminate the object within the hermetically sealed environment with high resolution. Further complications arise due to the need to compensate for spherical aberration encountered by the light when travelling through the planar surface of the glass window viewport. Furthermore, light passing through the elements of the lens and window also encounter multiple optical surfaces, each of which introduces scatter.

[0053] Whilst lenses might be located wholly within the hermetic enclosure, for example, in order to avoid aberrations due to the glass window, efficient optical coupling of the lenses, for example with optical fibres, is not possible without such optical fibres themselves penetrating the hermetic envelope, which would require bulky, costly and unreliable fibre optical feedthroughs Figures 1 to 20 describe vacuum viewport members addressing difficulties in known systems, thereby enabling improved illumination and / or collection of light from target objects within a hermetically sealed environment.

[0054] Figure 1 shows a cross-sectional view of a portion of a vacuum viewport member 100. The vacuum viewport member 100 comprises: a support body 102; a plurality of lenses 110 defined by a first surface 106 of the support body 102; a plurality of optical fibre receiving members 114 defining a plurality of recesses, wherein at least an axial end 116 of each recess of the plurality of recesses is formed by a portion of a second surface 108 of the support body 102 opposite to the first surface 106, wherein each recess of the plurality of recesses is arranged to receive an optical fibre 112 corresponding to a respective lens of the plurality of lenses 110. There is shown a vacuum viewport member 100 having a support body 102 forming a hermetic seal with part of a vacuum chamber wall 104. The support body 102 forms a hermetic seal with the vacuum chamber wall 104 at a connection region 109 . The connection region 109 comprises suitable means to enable the vacuum viewport member 100 to hermetically seal the vacuum chamber, for example by using suitable combinations of methods such as compressive indium seals and / or compressive o-rings and / or diffusion bonding and / or optical contacting and / or eutectic bonding and / or laser welding.

[0055] The support body 102 has a first surface 106 defining a plurality of lenses 110. The lenses 110 are defined by the first surface 106 using appropriate techniques for shaping the surface of the support body 102. In further examples, alternatively or additionally, the plurality of lenses 110 is provided on the first surface 106. In an example, laser-assisted glass etching is used to form three-dimensional structures into fused silica. In further examples, any suitable alternative or additional methods are used to form the plurality of lenses 110. Whilst the lenses 110 are shown to protrude from a substantially planar first surface 106 of the support body 102, in further examples, the lenses 110 are formed at least partially below a substantially planar first surface 106, for example, as illustrated with reference to Figure 20, which shows the formation of lenses 110 at least partially below a substantially planar first surface 106. Different lenses 110A, 110B, 110C of the plurality of lenses 110 are formed with any appropriate combination of size, location and profile. Whilst the first surface 106 of the support body 102 is shown to be substantially planar, in further examples the first surface 106 of the support body 102 has any appropriate form to enable the functionality described herein. For example, to facilitate conformation with a vacuum chamber and / or to facilitate improved alignment of components.

[0056] In further examples, additionally, or alternatively, lenses 110 are provided on the first surface 106 of the support body 102 using any appropriate means. The lenses 110 are microlenses with a diameter less than or equal to 1000 microns. Advantageously, the use of microlens arrays enables compact systems suitable for processes such as those based on quantum information processing. In further examples, the lenses 110, alternatively or additionally include lenses with different diameters, such as lenses with a diameter greater than 1000 microns and / or microlenses with diameters less than or equal to 500 microns, and / or less than or equal to 100 microns, and / or less than or equal to 10 microns, and / or less than or equal to one micron. The lenses 110 have a spherical profile. In further examples, additionally or alternatively, the lenses 110 have an aspherical profile, Fresnel profile, or combination thereof. The support body 102 has a second surface 108, opposite the first surface 106. A plurality of optical fibre receiving members 114 define a plurality of recesses for receiving a plurality of optical fibres 112. The plurality of optical fibre receiving members 114 are shown as substantially perpendicular recesses in a substantially planar second surface 108 of the support body 102. In further examples, the optical fibre receiving members 114 are formed at any appropriate angle to the second surface 108 of the support body 102, for example at a non- orthogonal angle to a substantially planar second surface 108, or at any appropriate angle to the second surface 108, where the second surface 108 is provided with any appropriate form to enable the functionality described here. For example, to facilitate conformation with a vacuum chamber and / or to facilitate improved alignment of components. Whilst the optical fibre receiving members 114 are shown to define recesses for receiving optical fibres 112 with the axial ends 116 of the recesses below the second surface 108 of the support body 102, in further examples the optical fibre receiving members 114 at least partially protrude from the second surface 108 of the support body 102 of the vacuum viewport 100 and the second surface 108 forms at least an axial end 116 of each recess. The optical fibre receiving members 114 are formed with appropriate dimensions and cross-sectional form to receive optical fibres 112 such that the functionality described herein can be implemented.

[0057] The lenses 110 and the optical fibre receiving members 114 are arranged so that optical fibres 112 received in the recesses of the optical fibre receiving members 114 correspond to a respective lens. For example, as shown at Figure 1, a first optical fibre receiving member 114A corresponds to a respective lens 110A in order to couple light travelling between an optical fibre 112A received in the optical fibre receiving member 114A and the lens 110A. As shown by the exemplary rays 118A, light can be focused by the lens 110A to the optical fibre 112A by focusing the light at the axial end 116A of the optical fibre receiving member 114A receiving the optical fibre 112A.

[0058] Similarly, there is shown a second optical fibre receiving member 114B corresponding to its respective lens 110B and a third optical fibre receiving member 114C corresponding to its respective lens 110C. As shown by the exemplary rays 118B, 118C, light can be coupled between lenses 110B, 110C and optical fibres 112B, 112C in their respective corresponding optical fibre receiving members 114B, 114C, for example by focusing light by the lenses HOB, 110C at the axial ends 116B, 116C of the respective optical fibre receiving members 114B, 114C.

[0059] In an example, the optical fibres 112 positioned in the optical fibre receiving members 114 are single-mode optical fibres. In further examples, the optical fibres 112 are any suitable type of optical fibres, such as multi-mode optical fibres, photonic crystal optical fibres, or a combination thereof. The dimensions and components of the vacuum viewport member 100 are determined in view of the desired wavelength or range of wavelengths of electromagnetic radiation that is to be manipulated, the desired numerical aperture and / or magnification and / or optical axis of each delivery or collection lens 110, and the spatial distribution of the target objects within the hermetically sealed environment.

[0060] The support body 102 is at least partially optically transparent in the region of the support body 102 between an axial end 116 of an optical fibre receiving member 114 and the respective lens 110, such that light can be coupled between the lens 110 and an optical fibre 114 received in its respective optical fibre receiving member 114.

[0061] Beneficially, the lenses 110 provided on the first surface 106 of the support body 102 can be situated within a hermetically sealed environment, such as within an ultra-high vacuum (UHV) chamber, whilst the optical fibre receiving members 114 define recesses in a second surface 108 of the support body 102 that can be situated outside of the hermetically sealed environment, such as in a standard atmosphere. Suitable arrangement of the lenses 110 and the optical fibre receiving members 114 means that simple insertion of the vacuum viewport member 100 in a vacuum chamber can enable accurate alignment of optical fibres 112 and lenses 110 with potential targets within the hermetically sealed environment, whilst also decreasing the target object-lens distance for improved optical performance.

[0062] Beneficially, the present disclosure describes improved illumination, or collection of light from, objects within a hermetically sealed environment.

[0063] Advantageously, the combination of lenses 110 and optical fibre receiving members 114 can be used to provide compact arrangements with each optical pathway or channel optimised with respect to its propagation direction, wavelength of operation, or spot size, for example. Further, the provision of lenses 110 on a vacuum-side of a vacuum viewport member 100 enables simplification of lens profiles compare with known systems that need to address refraction / reflection by the viewport window. Further, beneficially, the use of the vacuum viewport member 100 with a lens array reduces the number of discrete components that would otherwise be needed to be provided within the hermetically sealed environment in order to minimise the distance between target objects and lenses. Reducing the number of components reduces the surface area of material within the hermetically sealed environment which helps to maintain vacuum pressure. Furthermore, by the provision of vacuum viewport member 100 that simultaneously provides a hermetic seal whilst fixing the relative positions of optical fibre receiving members 114 and lenses 110 enables improved compactness of beam steering delivery and collection channels, minimises optical misalignment induced by environmental perturbations and reduces the time required to align and commission the optical system compared with known systems.

[0064] Known ex-vacuo high numerical aperture lenses require intermediary optics and optomechanics to couple light into an optical fibre, typically using ancillary mirrors and lenses for beam shaping and steering, with a nominal pathlength of 1 metre. Commissioning 10 to 15 beamlines associated with a two-species ion trap requires individual, extensive and iterative alignment. In contrast, the vacuum viewport member 100 enables beamlines to be aligned at the point of manufacture, with commissioning requiring simple insertion of a single element into a vacuum assembly. The use of lenses 110 that are micro-lenses with a diameter less than or equal to 1000 microns means that the optical fibre 112 to lens 110 distance can be of the order of millimetres. Further, the use of a homogenous material for the support body 102 means that alignment is significantly more stable with respect to temperature gradients compared with free- space beamlines. Whereas known systems have thermal drift compensated via manual adjustment, or at best electronic feedback and piezoelectric actuation of beam steering optics, these approaches limit scalability. In contrast, the vacuum viewport member 100 enables scalability of processes using multiple optical pathways in vacuum environments.

[0065] Figure 2 shows a cross-sectional view of a portion of a vacuum viewport member 200. The vacuum viewport member 200 is the same as the vacuum viewport member 100 described with reference to Figure 1, where the lenses 110A, 110B, 110C and their respective optical fibre receiving members 114 have been arranged based on the three respective target objects 120A, 120B, 120C located at fixed positions with respect to the vacuum viewport member 200 when the vacuum viewport member is positioned to provide a hermetically sealed environment within which the target objects 120 A, 120B, 120C are located.

[0066] The first lens 110A and corresponding optical fibre receiving member 114A are arranged such that the optical axis of the first lens 110A is substantially parallel to the longitudinal axis of the corresponding optical fibre receiving member 114A and such that light travelling through an optical fibre 112A positioned in the optical fibre receiving member 114A is focused in the direction of the arrow 122A to a spot coinciding with a first target object 120A.

[0067] The second lens HOB and corresponding optical fibre receiving member 114B are arranged such that the optical axis of the second lens 110B is substantially parallel to the longitudinal axis of the corresponding optical fibre receiving member 114B and such that light travelling in the direction of the arrow 122B from a target object 120B located in a hermetically sealed environment is focused by the second lens 110B to a spot coinciding with the end of the optical fibre 112B positioned in the optical fibre receiving member 114B corresponding to the second lens HOB. The third lens 1 IOC and corresponding optical fibre receiving member 114C are arranged such that the optical axis of the third lens 1 IOC is substantially parallel to the longitudinal axis of the optical fibre receiving member 114C and such that light travelling through an optical fibre 112C positioned in the optical fibre receiving member 114C is focused in the direction of the arrow 122C to a spot coinciding with a third target object 120C.

[0068] In the examples of Figure 2, the optical axes of the lenses 110 are substantially parallel to the optical axes of the corresponding respective optical fibre receiving members 114, such that the targets 120 are illuminated and / or light is collected from the targets 120 in a direction that is substantially perpendicular to the first surface 106 of the support body 102.

[0069] Alternatively and / or additionally, as illustrated with reference to the cross-sectional view of a portion of a vacuum viewport member 300 in Figure 3, the lenses 110A, HOB, 110C are arranged such that the optical axes of the lenses 110A, HOB, 110C are directed in different directions. In the example of Figure 3, the longitudinal axes of the optical fibre receiving members 114 are substantially parallel with one another. However, compared with the vacuum viewport members 100, 200 of Figures 1 and 2, the optical axes of the lenses are directed to target objects 120A, 120B, 120C located at different positions within a hermetically sealed environment. Therefore, Figure 3 illustrates an example wherein at least a subset of the plurality of lenses 110 has respective optical axes pointing in different directions. Accordingly, the profile and functionality of the lenses 110 are determined such that optical fibres 112 are received in an efficiently packed manner in the vacuum viewport member 300 and coupled with lenses 110 that are precisely directed to perform their appropriate task of illuminating and / or collecting light associated with particular locations within an apparatus in a hermetically sealed environment.

[0070] Figure 4 illustrates a further cross-sectional view of a portion of a vacuum viewport member 400. In a similar manner to the vacuum viewport member 300 shown at Figure 3, the vacuum viewport member 400 is arranged such that the longitudinal axes of the optical fibre receiving members 114 are substantially parallel with one another and the optical axes of different lenses 110 point in different directions. However, in contrast to the arrangement shown at Figure 3, that the optical axis of the second lens 110B is shown to intersect the optical axis of the third lens 110B at the position of a target object 120B located at a fixed position relative to the vacuum viewport member 400. Accordingly, light may be directed along one of the optical fibres 112B, 112C positioned in the respective optical fibre receiving member 114B, 114C and focused at the target 120B by the respective lens 110B, 110C. The other of the lenses HOB, HOC may be used to focus light from the illuminated target object 120B to the other of the optical fibres 112B, 112C positioned in the respective optical fibre receiving member 114B, 114C, thereby facilitating measurements of the target object 120B located in the hermetically sealed environment. Therefore, Figure 4 shows an example of the vacuum viewport member wherein at least a subset of the plurality of lenses 110 has respective optical axes pointing in different directions, wherein the optical axes of two or more of the subset of the plurality of lenses 110 substantially intersect with each other at one or more target positions that are predetermined relative to the first surface 106.

[0071] Figure 5 shows a further cross-sectional view of a portion of a vacuum viewport member 500. In contrast to the vacuum viewport members 100, 200, 300, 400 of Figures 1 to 4, the longitudinal axes of the optical fibre receiving members 514 are shown in a non -parallel configuration. The lenses 110 and optical fibre receiving members 514 are arranged in a suitable configuration based on the particular application. The longitudinal axes of the optical fibre receiving members 514 are shown to be substantially parallel to the optical axes of the respective lenses 110. Accordingly, the first lens 110A and corresponding respective optical fibre receiving member 514A are arranged such light from an optical fibre 112A positioned in the optical fibre receiving member 514A illuminates a target object 520A in a hermetically sealed environment in a direction in line with the longitudinal axis of the optical fibre receiving member 514A and the optical axis of the lens 110A.

[0072] The optical axis of the second lens 110B is shown to intersect the optical axis of the third lens 110B at the position of a target object 520B located at a fixed position relative to the vacuum viewport member 500. The optical axis of the second lens 110B is substantially parallel to the longitudinal axis of the second optical fibre receiving member 514B and the optical axis of the third lens 110C is substantially parallel to the longitudinal axis of the third optical fibre receiving member 514C. Accordingly, light may be directed along one of the optical fibres 112B, 112C positioned in the respective optical fibre receiving member 514B, 514C and focused at the target 520B by the respective lens HOB, 110C. The other of the lenses 110B, 110C may be used to focus light from the illuminated target object 120B to the other of the optical fibres 112B, 112C positioned in the respective optical fibre receiving member 514B, 514C, thereby facilitating measurements of the target object 520B located in the hermetically sealed environment. Therefore, Figure 5 shows an example of a vacuum viewport member wherein at least a subset of the plurality of lenses 110 has respective optical axes pointing in different directions, wherein the subset of the plurality of lenses 110 has respective optical axes pointing in a direction substantially parallel to the respective longitudinal axes of a subset of the plurality of recesses, optionally wherein the optical axes of two or more of the subset of the plurality of lenses 110 substantially intersect with each other at one or more target positions that are predetermined relative to the first surface 106. Figures 1 to 5 show examples of the vacuum viewport member viewport member comprising: a support body 102; a plurality of lenses 110 defined by or provided on a first surface 106 of the support body 102; a plurality of optical fibre receiving members 114 defining a plurality of recesses, wherein at least an axial end 116 of each recess of the plurality of recesses is formed by a portion of a second surface 108 of the support body 102 opposite to the first surface 106, wherein each recess of the plurality of recesses is arranged to receive an optical fibre 112 corresponding to a respective lens of the plurality of lenses 110, wherein the plurality of optical fibre receiving members 114 and respective lenses 110 are arranged to direct light from optical fibres 112 in the plurality of recesses towards one or more target positions that are predetermined relative to the first surface 106 and / or to direct light from one or more target positions that are predetermined relative to the first surface towards optical fibres 112 in the plurality of recesses.

[0073] The support body 102 of the vacuum viewport members 100, 200, 300, 400, 500 described with reference to Figures 1 to 5 is optionally an integrally formed, monolithic support body 102. A monolithic support body 602 is shown at Figure 6. Figure 6 shows a cross- sectional view of a portion of a monolithic vacuum viewport member 600. The vacuum viewport member 600 is integrally formed to provide lenses 610 defined by a first surface 606 of the support body 602. The vacuum viewport member 600 is integrally formed to provide optical fibre receiving members 614 defining recesses in a second surface 608 of the support body 602 opposite the first surface 606.

[0074] The monolithic support body 602 is formed by selective laser etching of glass material. A solid piece of glass material is subject to femtosecond laser pulses in order selectively to weaken the structure of the material with high accuracy. The selectively weakened regions of glass are considerably more susceptible to etching, e.g., by hot KOH. The removal of material is controlled to provide a structure such as that shown at Figure 6. Alternatively, or additionally, the support body 602 is formed using any other appropriate method, such as focused ion beam milling and / or ablative laser processing and / or moulding and / or diamond micromilling, for example.

[0075] Whilst the support body 602 is formed from glass, in further examples the support body 602 is formed from any suitable material, including, but not limited to, fused silica, borosilicate glass and silicon.

[0076] Advantageously, the monolithic support body 602 enables and maintains precise alignment between the plurality of lenses 610 and the optical fibre receiving members 614. The optical fibre receiving members 614 can be formed with appropriate tolerances for maintaining and aligning optical fibres. The monolithic support body 602 is determined at the point of manufacture, thereby improving the reliability of the alignment compared with the use of known systems, which introduce errors associated with the positioning of two or more discrete optical components. Further, the monolithic support body 602 provides a more robust interface between lenses 610 and optical fibre receiving members 614 with respect to mechanical vibrations and / or thermal gradients. Furthermore, the use of a monolithic support body 602 engineer to provide lenses 610 and optical fibre receiving members 614 on opposite sides means that there is no intermediary surface between the lenses 610 and the optical fibre receiving members 614, thereby avoiding reflections from refractive index boundaries that may otherwise be introduced. Whilst the vacuum viewport members 100, 200, 300, 400, 500 described with reference to Figures 1 to 5 can be formed from a monolithic, integrally formed support body, as described with reference to Figure 6, in further examples, optionally the vacuum viewport members 100, 200, 300, 400, 500 are formed from an integrally formed portion comprising lenses and an integrally formed portion comprising recesses.

[0077] Figure 7 shows an exploded cross-sectional view of a portion of a vacuum viewport member 700 formed from a first integrally formed portion 702A and a second integrally formed portion 702B. The first integrally formed portion 702A comprises lenses 710, analogous to the lenses described with reference to Figures 1 to 6. The first integrally formed portion 702A provides a first surface 706 of the support body 702 and the second integrally formed portion 702B provides a second surface 708 of the support body 702. The first integrally formed portion 702A has a further surface 707 opposite the first surface 706 of the support body 702 and the second integrally formed portion 702B has a further surface 709 opposite the second surface of the support body 702. The further surface 707 of the first integrally formed portion 702A faces the further surface 709 of the second integrally formed portion 702B.

[0078] The second integrally formed portion 702B comprises the recesses defined by optical fibre receiving members 714, analogous to the recesses defined by optical fibre receiving members described with reference to Figures 1 to 6. The optical fibre receiving members 714 of the second integrally formed portion 702B have axial ends 716 forming blind holes within the second integrally formed portion 702B. Beneficially, the second integrally formed portion 702B is formed from a continuous piece of material enhancing the sealing integrity of the vacuum viewport member 700 within the second integrally formed portion 702B.

[0079] The first integrally formed portion 702A and the second integrally formed portion 702B are integrally formed from glass by any appropriate method, for example by selective laser etching or focussed ion beam milling, in an analogous fashion as described with reference to Figure 6. In further examples, additional and / or alternative methods are used to provide the first integrally formed portion 702A and / or the second integrally formed portion 702B. In further examples, additional and / or alternative materials are used to form the first integrally formed portion 702A and / or the second integrally formed portion 702B, including, but not limited to fused silica, borosilicate glass and / or silicon, for example.

[0080] The first integrally formed portion 702A and the second integrally formed portion 702B are formed by the same or different manufacturing process. In examples, two or more glass manufacturing technologies are used to form the vacuum viewport member 700. For example, laser assisted etching and / or additive printing of silica are used to provide small angled ion illumination lenses 710 and optical fibre receiving members 714, whilst ablative techniques are used for large fluorescence collection lenses 710. Advantageously, the vacuum viewport member 700 is formed in a flexible and efficient manner.

[0081] Whilst the first integrally formed portion 702A and the second integrally formed portion 702B are not shown to contact each other in the exploded cross-sectional view of Figure 7, the skilled person understands that the first integrally formed portion 702A and the second integrally formed portion 702B are arranged to provide the functionality described herein in the form of a vacuum viewport member 700 that can be used to form a hermetic seal and enable illumination / light collection from one or more target objects in a hermetically sealed environment. For example, combination by any appropriate method of the first integrally formed portion 702A and the second integrally formed portion 702B at an interface between the surface 707 of the first integrally formed portion 702A and the surface 709 of the second integrally formed portion 702B results in a vacuum viewport member 700 having lenses 710 that can be positioned in a vacuum chamber and optical fibre receiving members 714 that can receive optical fibres outside of the vacuum chamber. The interface between the internal surfaces 707, 709 facing one another may comprise one or more gaps and / or layers to provide enhanced functionality. In an example, the first integrally formed portion 702A and the second integrally formed portion 702B are mechanically fixed, thereby to form the vacuum viewport member 700. In a further example, the first integrally formed portion 702A is bonded to the second integrally formed portion 702B using an adhesive material. In a further example, the first integrally formed portion 702A is bonded to the second integrally formed portion 702B using anodic bonding. In further examples, the first integrally formed portion 702A is bonded to the second integrally formed portion 702B using any appropriate additional or alternative bonding mechanism.

[0082] Where the interface between the internal surfaces 707, 709 is between the material forming the first integrally formed portion 702A and the material second integrally formed portion 702B, optical contact between the internal surfaces 707, 709 reduces light scattering at the interface formed by the internal surfaces 707, 709. Direct physical and optical contact between the first integrally formed portion and the second integrally formed portion is shown at Figure 11. Figure 11 shows a vacuum viewport member 1100 with a first integrally formed portion 1102A in direct physical and optical contact with a second integrally formed portion 1102B. Optical contact between the first integrally formed portion 1102A and the second integrally formed portion 1102B results in reduced light scattering between lenses 1110 and optical fibres positioned in the optical fibre receiving members 1114, and optionally provides the structural bond between the two integrally formed portions.

[0083] Figure 8 shows an exploded cross-sectional view of a portion of an alternative vacuum viewport member 800 formed from a first integrally formed portion 802A and a second integrally formed portion 802B. The first integrally formed portion 802A comprises lenses 810, analogous to the lenses described with reference to Figures 1 to 6. The second integrally formed portion 802B comprises the recesses defined by optical fibre receiving members 814, analogous to the recesses defined by optical fibre receiving members described with reference to Figures 1 to 6. The first integrally formed portion 802A has a further surface 807 opposite the first surface

[0084] 806 of the support body 802 and the second integrally formed portion 802B has a further surface 809 opposite the second surface of the support body 802. The further surface 807 of the first integrally formed portion 802A faces the further surface 809 of the second integrally formed portion 802B.

[0085] In contrast to the optical fibre receiving members 714 of the second integrally formed portion 702B of the vacuum viewport member 700 described with reference to Figure 7, the optical fibre receiving members 814 of the vacuum viewport member 800 are provided by through-holes formed within the second integrally formed portion 802B.

[0086] Whilst the first integrally formed portion 802A and the second integrally formed portion 802B are not shown to contact each other in the exploded cross-sectional view of Figure 8, the skilled person understands that the first integrally formed portion 802A and the second integrally formed portion 802B are arranged to provide the functionality described herein in the form of a vacuum viewport member 800 that can be used to form a hermetic seal and enable illumination / light collection from one or more target objects in a hermetically sealed environment.

[0087] For example, combination by any appropriate method of the first integrally formed portion 802A and the second integrally formed portion 802B at an interface between a surface

[0088] 807 of the first integrally formed portion 802A and a surface 809 of the second integrally formed portion 802B results in a vacuum viewport member 800 having lenses 810 that can be positioned in a vacuum chamber and optical fibre receiving members 814 that can receive optical fibres outside of the vacuum chamber. The optical fibre receiving members 814 are configured to receive optical fibres 812. The interface between the internal surfaces 807, 809 facing one another may comprise one or more gaps and / or layers to provide enhanced functionality. The first integrally formed portion 802A and the second integrally formed portion 802B work together to provide a vacuum viewport member whereby axial ends of the optical fibre receiving members 814 are provided by the surface 807 of the first integrally formed portion 802A, or by any surface of a layer positioned between the first integrally formed portion 802A and the second integrally formed portion 802B. In further examples, additionally or alternatively, there is a gap between the axial end of an optical fibre received in at least one of the optical fibre receiving members 812 and the first integrally formed portion 802A.

[0089] In a manner similar to the vacuum viewport member 700 of Figure 7, the first integrally formed portion 802A and the second integrally formed portion 802B are integrally formed from glass by any appropriate method, for example by selective laser etching or focussed ion beam milling, in an analogous fashion as described with reference to Figure 6. In further examples, additional and / or alternative methods are used to provide the first integrally formed portion 802A and / or the second integrally formed portion 802B. In further examples, additional and / or alternative materials are used to form the first integrally formed portion 802A and / or the second integrally formed portion 802B, including, but not limited to fused silica, borosilicate glass and / or silicon, for example. In an example, the first integrally formed portion 802A and the second integrally formed portion 802B are mechanically fixed, thereby to form the vacuum viewport member 800. In a further example, the first integrally formed portion 802A is bonded to the second integrally formed portion 802B using an adhesive material.

[0090] In a further example, the first integrally formed portion 802A is bonded to the second integrally formed portion 802B using anodic bonding. In further examples, the first integrally formed portion 802A is bonded to the second integrally formed portion 802B using any appropriate alternative or additional bonding mechanism.

[0091] Where the interface between the internal surfaces 807, 809 is between the material forming the first integrally formed portion 802A and the material second integrally formed portion 802B, optical contact between the internal surfaces 807, 809 reduces light scattering at the interface formed by the internal surfaces 807, 809. Direct physical and optical contact between the first integrally formed portion and the second integrally formed portion is shown at Figure 11. Figure 11 shows a cross-sectional view of a portion of a vacuum viewport member 1100 with a first integrally formed portion 1102A in direct physical and optical contact with a second integrally formed portion 1102B. Optical contact between the first integrally formed portion 1102A and the second integrally formed portion 1102B results in reduced light scattering between lenses 1110 and optical fibres positioned in the optical fibre receiving members 1114. Figure 9 shows a cross-sectional view of a portion of a vacuum viewport member 900 formed from a first integrally formed portion 902A in combination with a second integrally formed portion 902B, as described with reference to Figures 7 and 8. The vacuum viewport member 900 of Figure 9 additionally shows two further layers 903, 905 positioned between the surface 907 of the first integrally formed portion 902A and the surface 909 of the second integrally formed portion 902B. The further layers 903, 905 are mating surfaces of the first integrally formed portion 902A and the second integrally formed portion 902B, respectively. Accordingly, Figure 9 shows an example wherein the first integrally formed portion 902A comprises a mating surface 905 opposite the first surface 906 and the second integrally formed portion 902B comprises a mating surface 903 opposite the second surface 908, wherein the mating surface 905 of the first integrally formed portion 902A faces the mating surface 905 of the second integrally formed portion 902B. Whilst the further layer 905 is shown as a distinct layer adjacent to the surface 907 of the first integrally formed portion 902A, in further examples the further layer 905 provides an integrally formed mating surface 905 of the first integrally formed portion 902A. Whilst the further layer 903 is shown as a distinct layer adjacent to the surface 909 of the second integrally formed portion 902B, in further examples the further layer 903 provides an integrally formed mating surface 909 of the second integrally formed portion 902B. The mating surface provided by the further layer 905 of the first integrally formed portion 902A faces the mating surface provided by the further layer 903 of the second integrally formed portion 902B. The layers 905, 903 are bonded together, thereby to fix the first integrally formed portion 902A to the second integrally formed portion 902B. In an example, the layers 905, 903 provide the means for eutectic bonding of the first integrally formed portion 902A with the second integrally formed portion 902B. In further examples, there is only one of the layers 905, 903 to provide eutectic bonding of the first integrally formed portion 902A with the second integrally formed portion 902B. In further examples, there are additional or alternative layers between the first integrally formed portion 902A and the second integrally formed portion 902B to facilitate bonding of the first integrally formed portion 902A and the second integrally formed portion 902B.

[0092] Whilst the optical fibre receiving members 914 are shown as blind holes in the second integrally formed portion 902B, in further examples the optical receiving members 914 are additionally, or alternatively, through holes in the second integrally formed portion 902B, with the axial ends of the optical fibre receiving members 914 being provided by the layer 903 positioned between the first integrally formed portion 902A and the second integrally formed portion 902B, for example in an analogous manner to that described with reference to Figure 8. In order to reduce optical losses, for example due to scattered light, between the first integrally formed portion and the second integrally formed portion described with reference to Figures 7 to 9, one or more refractive index matching materials can be positioned between the first integrally formed portion and the second integrally formed portion. Figure 10 shows a cross-sectional view of a portion of a vacuum viewport member 1000 with a first integrally formed portion 1002A comprising lenses 1010 and a second integrally formed portion 1002B comprising optical fibre receiving members 1014, as described with reference to Figures 1 to 9. The first integrally formed portion 1002A is associated with a mating surface 1005 facing a mating surface 1003 associated with the second integrally formed portion 1002B. In between the mating surfaces 1005, 1003, there is positioned a refractive index matching material 1007.

[0093] Figure 10 shows an example wherein the support body 1002 comprises one or more layers at least partially between the mating surface 1005 of the first integrally formed portion 1002A and the mating surface 1003 of the second integrally formed portion 1002, wherein the one or more layers comprise refractive index matching material 1007. In further examples, the support body 1002 comprises one or more additional or alternative layers at least partially between the mating surfaces 1005, 1003. Alternatively, or additionally, as shown with reference to Figure 7, at least part of the mating surface 905 of the first integrally formed portion 902A is in optical contact with at least part of the mating surface 903 of the second integrally formed portion 902B, thereby to reduce light scattering at the interface between the mating surface 905 of the first integrally formed portion 902A and the mating surface 903 of the second integrally formed portion 902B.

[0094] Where a vacuum viewport member is formed from a first integrally formed portion and a second integrally formed portion, for example as described with reference to Figures 7 to 11, one or more alignment features may be implemented in order to facilitate precise alignment of lenses with optical fibre receiving members. Figure 12 shows a cross-sectional view of a portion of a vacuum viewport member 1200 comprising a first integrally formed portion 1202A and a second integrally formed portion 1202B. In order to align the lenses 1210 with the optical fibre receiving members 1214, alignment features are used Figure 12 shows different implementations of alignment features. For example, fiducial markers 1209 are included in one or both of the first integrally formed portion 1202A and the second integrally formed portion 1202B in order to facilitate alignment with respect to one another. Registration features 1211, such as cross-hair type features are alternatively or additionally included in one or both of the first integrally formed portion 1202A and the second integrally formed portion 1202B in order to facilitate alignment with respect to one another. Alignment features that provide the means to physically associate the first integrally formed portion 1202A and the second integrally formed portion 1202B, such as alignment location features 1213 are included, additionally or alternatively, to facilitate alignment. In an example, alignment location features 1213 comprise one or more recesses and one or more protrusions that cooperate with one another in order to physically locate the first integrally formed portion 1202A with respect to the second integrally formed portion 1202B. Accordingly, Figure 12 shows an example wherein the first integrally formed portion 1202A and / or the second integrally formed portion 1202B comprise one or more alignment features, thereby to enable alignment of the first integrally formed portion 1202A with the second integrally formed portion 1202B. Optionally, the one or more alignment features comprise fiducial markers and / or registration features.

[0095] The vacuum viewport members described with reference to Figures 1 to 12 may be provided with enhanced functionality through the use of one or more surface coatings. Whilst Figure 13 shows a cross-sectional view of a portion of a vacuum viewport member 1300 comprising a first integrally formed portion 1302A and a second integrally formed portion 1302B, the functionality described with reference to Figure 13 is also applicable to monolithically formed vacuum viewport members. The support body 1302 (optionally formed from separate pieces) comprises lenses 1310 defined by, or provided on, a first surface 1306. A further coating 1315 is provided on the first surface 1306. The further coating 1315 is a continuous or discontinuous coating to provide functionality. For example, the further coating 1315 is an anti -reflective coating.

[0096] Alternatively, or additionally, the further coating comprises an electrically conductive material. Electrically conductive material can be used to form at least part of one or more electrical circuits. Figure 14 shows a perspective view of a portion of a vacuum viewport member 1400. The vacuum viewport member 1400 has a support body 1402, lenses 1410 and optical fibre receiving members 1414 analogous to those described with reference to Figures 1 to 13. In a manner analogous to the surface coating 1315 described with reference to Figure 13, there is shown an electrically conductive coating 1417 forming part of an electrical circuit. The electrically conductive coating 1417 is formed in an appropriate manner to provide electrical communication as desired within a hermetically sealed environment. The electrically conductive coating 1417 optionally connects one or more components (not shown). In an example, the electrically conductive coating 1417 is patterned to provide electrodes. Advantageously, electrically functional devices can be arranged in close proximity to the optical components of the vacuum viewport 100 and inserted into a vacuum chamber at the same time. Electrically conductive material can also be used to provide further functionality. For example, the electrically conductive coating 1418 shown to surround the lenses 1410 at Figure 14 is optionally provided in order to enable electrical shielding. In an example, the electrically conductive coating 1418 is an optically-transparent, electrically-conductive material, such as indium tin oxide (ITO) that is applied to coat a lens 1410A. In further examples, the electrically conductive coating 1418 is formed from any appropriate alternative or additional material. Advantageously, the electrically conductive coating 1418 may be connected to ground or another controlled potential, thereby to prevent unwanted perturbations of the electric field within the system within which it is operating, due to the dielectric surface of the lens 1410. Whilst Figure 14 shows particular arrangements of coatings of electrically conductive material 1417, 1418 to provide electrodes and electrical shielding, in further examples, electrically conductive coatings are provided in any suitable arrangement in order to implement the functionality described herein. In order to reduce optical crosstalk associated with light travelling between different lenses and optical fibres positioned in their corresponding respective optical fibre receiving members, optical shielding may be provided in the vacuum viewport member, such as in the vacuum viewport members described with reference to Figures 1 to 14. Figures 15 and 16 illustrate examples wherein the vacuum viewport member comprises optical shielding arranged to reduce optical crosstalk associated with light from different lenses of the plurality of lenses.

[0097] Figure 15 shows a cross-sectional view of a portion of a vacuum viewport member 1500 with optical shielding. The vacuum viewport member 1500 comprises lenses 1510 and optical fibre receiving members 1514 analogous to those described with reference to Figures 1 to 14. Additionally, the vacuum viewport member 1500 comprises an optical shielding layer 1519. The optical shielding layer 1519 is a continuous or discontinuous layer with one or more regions that enable light to be communicated between a lens 1510 and an optical fibre located in a corresponding optical fibre receiving member 1514 whilst reducing optical cross-talk between the lens 1510 and different optical fibres located in optical fibre receiving members 1514 not corresponding to the lens 1510. For example, as shown at Figure 15, light leaving an optical fibre 1512A located in the corresponding optical fibre receiving member 1514A (illustrated by arrows representing light rays) is allowed to pass through an aperture 1521 A in the optical shielding layer 1519 such that it is refracted by a first lens 1510A for delivery to a corresponding target site However, the optical shielding layer 1519 prevents light reflected or scattered by the first lens 1510A from reaching the second optical fibre 1512B, or the third optical fibre 1512C, located in their respective optical fibre receiving members 1514B, 1514C. Accordingly, the optical shielding comprises one or more shielding layers 1519 at least partially between the first surface 1506 and the second surface 1508. Optionally, the optical shielding layers 1519 are positioned at least partially between the mating surface of a first integrally formed portion and the mating surface of a second integrally formed portion, such as the mating surfaces described with reference to Figures 9 and 10. The optical shielding layer 1519 is provided by any appropriate method. In an example, the optical shielding layer 1519 is formed on at least one of the internal surfaces of a first integrally formed portion and a second integrally formed portion, such that assembly of a vacuum viewport member from such integrally formed portions results in the optical shielding layer being positioned between the lenses 1510 and the optical fibre receiving members such as to provide the functionality described herein.

[0098] Figure 16 shows an alternative way of providing optical shielding in a vacuum viewport member, such as the vacuum viewport members described with reference to Figures 1 to 15, such that the vacuum viewport member comprises optical shielding arranged to reduce optical crosstalk associated with light from different lenses of the plurality of lenses. At Figure 16 there is shown a cross-sectional view of a portion of a vacuum viewport member 1600. The vacuum viewport member 1600 comprises lenses 1610 and optical fibre receiving members 1614 analogous to those described with reference to Figures 1 to 15. Additionally, the vacuum viewport member 1600 comprises trenches 1623 positioned at least partially between two or more optical fibre receiving members 1614. The trenches 1623 are at least partially filled with an optical shielding material, such as a metal. Accordingly, the optical shielding comprises one or more trenches 1623 in the support body 1602, optionally wherein the one or more trenches 1623 are at least partially filled with an optical shielding material 1625, optionally wherein the optical shielding material 1625 comprises a metal. The optical shielding material 1625 in the trenches 1623 enables light to be communicated between a lens 1610 and an optical fibre located in a corresponding optical fibre receiving member 1614 whilst reducing optical cross-talk between the lens 1610 and different optical fibres located in optical fibre receiving members 1614 not corresponding to the lens 1610. For example, as shown at Figure 16, light leaving an optical fibre 1612A located in the corresponding optical fibre receiving member 1614A (illustrated by arrows representing light rays) is allowed to pass between optical shielding material 1625 in trenches 1623 such that it is refracted by a first lens 1610A for delivery to a corresponding target site. However, the optical shielding material 1625 in the trenches 1623 prevents light reflected or scattered by the first lens 1610A from reaching the second optical fibre 1612B, or the third optical fibre 1612C, located in their respective optical fibre receiving members 1614B, 1614C. The trenches 1623 and optical shielding material 1625 are provided by any appropriate method to provide the functionality described herein. In an example, the trenches are 1623 formed in the support body 1602 and subsequently filled with optical shielding material 1625.

[0099] Whilst the trenches 1623 are shown with optical shielding material 1625 in the trenches, in further examples, additionally and / or alternatively, the trenches 1623 are not filled with material and reduce optical cross-talk by virtue of total internal reflection, for example. As described with reference to Figures 1 to 16, optical fibre receiving members are provided in the vacuum viewport members in order to receive optical fibres. In order to reduce light scattering between optical fibres and the recesses formed by the optical fibre receiving members, such as those described with reference to Figures 1 to 16, refractive index matching material is implemented. An example of a vacuum viewport member as described herein comprising refractive index matching material at least partially within at least one of the recesses defined by at least one of the plurality of optical fibre receiving members, thereby to reduce light scattering between an optical fibre in the recess of the at least one of the plurality of recesses and the support body is described with reference to Figure 17. Figure 17 shows a cross-sectional view of a portion of a vacuum viewport member 1700, which has a support body 1702, lens 1710 and optical fibre receiving member defining a recess, analogous to those described with reference to Figures 1 to 16. At an axial end 1716 of the optical fibre receiving member, there is shown refractive index matching material 1727 in the recess, thereby to reduce light scattering between the optical fibre 1712 in the recess of the optical fibre receiving member 1714 and the support body 1702. Whilst only one optical fibre receiving member 1714 and corresponding lens 1710 is shown at Figure 17, the skilled person understands that refractive index matching material may be implemented in a number of optical fibre receiving members to provide the functionality described herein. Whilst index matching between fibres 1712 and optical fibre receiving members 1714 is provided by a refractive index matching material, in further examples, additionally and / or alternatively, index matching is provided through the use of laser welding, for example.

[0100] In order to perform stable and compact processes in a hermetically sealed environment, vacuum viewport members, such as those described with reference to Figures 1 to 17, may be provided with one or more location features configured to locate one or more components relative to the lenses of a vacuum viewport member. A vacuum viewport member as described herein, wherein the first surface comprises one or more location features configured to locate one or more components relative to the plurality of lenses is described with reference to Figure 18. Optionally, the one or more location features comprise one or more fiducial markers and / or registration features. Figure 18 shows a cross-sectional view of a portion of a vacuum viewport member 1800. The vacuum viewport member has a support body 1802, lenses 1810 and optical fibre receiving members 1814 analogous to those described with reference to Figures 1 to 17. Additionally, location features 1809, 1813 are shown to be associated with the first surface 1806 of the vacuum viewport member 1800. Figure 18 shows different implementations of location features that can be implemented in the vacuum viewport members described herein. For example, fiducial markers 1809 are included in one or both of the support body 1802 and the component 1829 in order to locate the component 1829 with respect to the vacuum viewport member 1800. Alternatively, or additionally, location features that provide the means to physically associate the support body 1802 and a component 1831 are provided, such as location features 1813. In an example, location features 1813 comprise one or more recesses and one or more protrusions that cooperate with one another in order to physically locate the component 1831 in position with respect to the support body 1802 of the vacuum viewport member 1800. The location features 1813 may be arranged such that the support body 1802 comprises a recess for receiving a protrusion from a component 1831. Alternatively, or additionally, the support body 1802 comprises a protrusion that is received in a recess of a component 1831, thereby to locate the component with respect to the support body 1802. Alternatively, or additionally, both the component 1831 and support body 1802 comprise recesses for receiving a member collocating the component 1831 and the support body 1802. In further examples, any suitable arrangement of location features is used to locate components 1829, 1831 with respect to the vacuum viewport member 1800. Additionally, or alternatively, the components 1829, 1831 are fixed to the vacuum viewport member 1800 by one or more fixings and / or by the one or more location features 1813.

[0101] Whilst the lens described with reference to Figures 1 to 18 are shown to have particular cross-sectional profiles, the vacuum viewport members described with reference to Figures 1 to 18 may be provided with lenses, or define lenses, with any appropriate configuration in order to provide the functionality required for the processes that they are being used with.

[0102] Figure 1 shows a cross-sectional view of a portion of a vacuum viewport member 1900 showing different types of lenses 1910 that can be implemented in the vacuum viewport members described herein. The vacuum viewport member 1900 is provided with a support body 1902, lenses 1910 and optical fibre receiving members 1914 analogous to those described with reference to Figures 1 to 18. Figure 19 shows a first lens 1910A with a spherical profile, a second lens 1910B with an aspherical profile and a third lens 1910C with a Fresnel profile. The lenses 1910 defined by, or provided on, a first surface 1906 of the support body 1902 of the vacuum viewport member 1900 are provided with profiles in any appropriate combination in accordance with the processes that they are supporting. Whilst the lenses 1910 are shown to form an integral part of the vacuum viewport member 1900, formed for example in accordance with the methods described herein, in further examples, additionally and / or alternatively lenses 1910 are formed separately and provided on the surface 1 06 of the support body 1902 with a suitable distribution. Whilst the lenses 1910 are shown to be at least partially proud of the substantially planar first surface 1906 in further examples, alternatively or additionally, lenses 1910 are defined or provided by the first surface such that at least a portion of the lenses 1910 is below the first substantially planar first surface 1906.

[0103] The support body of the vacuum viewport members described with reference to Figures 1 to 19 is at least partially formed from material that is optically transmissive and vacuum compatible. In particular, regions of the support body between the lenses and their respective optical fibre receiving members are optically transmissive, thereby to enable light to travel between a lens and an optical fibre in a respective optical fibre receiving member. Advantageously, formation of a support body from material that is optical transmissive serves a dual purpose of retaining the orientation of components whilst enabling optical access between the inside and outside of a hermetically sealed environment. In an example, the support body is at least partially formed from a material comprising at least one of: glass, fused silica, borosilicate glass and silicon. In some examples, some portions of the support body are not optically transmissive. For example, where a support body is formed by the combination of a first integrally portion comprising lenses and a second integrally formed portion comprising optical fibre receiving members, as described herein, the second integrally formed portion may be formed from a material that is not optically transmissive as long as light can be communicated to lenses from the optical fibre receiving members (for example, when the optical fibre receiving members are not blind holes in an optically opaque material). Advantageously, forming a second integrally formed portion with optical fibre receiving members from a material that is not optically transmissive widens the possibility of materials that can be used, exploiting different properties (e.g., ease of machining and / or structural integrity). Beneficially, forming the support body from a single material, or forming the first integrally formed portion and the second integrally formed portion from the same material also results in advantageous properties, such as by matching the coefficient of thermal expansion in the support body. This permits a greater operational temperature range. Fused silica is a particularly beneficial material to use for formation of the support body, as it has a very low coefficient of thermal expansion and works well in mechanical contact with other fused silica elements and / or those with some compressibility.

[0104] Whilst the lenses shown in cross-sectional views with reference to Figures 1 to 19 are arranged in a row, in further examples the vacuum viewport members comprise any appropriate number of lenses in regular or irregular arrays of lenses as needed. In an example, the plurality of lenses described with reference to Figures 1 to 21 comprise at least one microlens having an outermost diameter of less than or equal to 1000 microns. In an example, the plurality of lenses described with reference to Figures 1 to 21 comprises at least one lens having a spherical profile and / or at least one lens having an aspherical profile and / or at least one lens having a Fresnel profile.

[0105] Figure 20 shows a perspective view of a cross section of a vacuum chamber 2000 that provides a hermetically sealed environment in which processes, such as those requiring ultra- high vacuum pressures, can be performed. There is shown a vacuum chamber wall 204. There is also shown an aperture filled by a vacuum viewport support body 102 with a connection region 109 that work together to hermetically seal the vacuum chamber 2000. The support body 102 of the vacuum viewport 500 of Figure 5 is shown in combination with the vacuum chamber 2000, however, any of the vacuum viewport members described herein with reference to Figures 1 to 19 may be used to provide a hermetic seal of the vacuum chamber 2000. As described with reference to Figure 5, the optical fibre receiving members 514 and lenses 110 are arranged to direct light between a target object 520 located within the hermetically sealed environment within the vacuum chamber 2000 and optical fibres 112 that can be located in the optical fibre receiving members 514. In an example, the optical axes of the optical fibre receiving members 514 are angled such that the principal optical axes 512 of respective optical fibre receiving members 514 align with the respective principal optical axes 512 of the optical fibres 112 received in the optical fibre receiving members, such that the respective principal optical axes 512 coincide at a particular position. Advantageously, a vacuum system is provided, the vacuum system comprising the vacuum viewport member, wherein the vacuum viewport member is configured to form a hermetically sealed part of the vacuum chamber 2000 thereby to enable a pressure differential to be created between the environment within the vacuum chamber 2000 and the environment outside the vacuum chamber 2000, wherein the first surface 106 faces into the vacuum chamber 2000.

[0106] The target object 520 located within the hermetically sealed environment is one of any number of target objects of interest in a hermetically sealed environment. For example, the target object is a trapped ion, neutral atom, nitrogen vacancy or quantum dot. Whilst not shown in Figure 20, in examples, the vacuum chamber 2000 comprises further apparatus for generating and / or controlling and / or characterising one or more target objects 520. For example, the vacuum chamber comprises an ion-trap and / or atom trap subsystem. The ion-trap and / or atom trap subsystem, or other subsystem, are fixed in position with respect to the vacuum viewport member 100, for example as described with reference to the components 1829, 1831 of Figure 18.

[0107] Figure 21 shows a perspective view 2100 of a portion of the vacuum chamber 2000 shown at Figure 20 with an ion trap 2102 included within the vacuum chamber 2000. Figure 21 illustrate a vacuum system comprising a vacuum chamber 2000 and a vacuum viewport member. In the example of Figure 21, the ion trap 2102 is positioned such that ions may be trapped between pole electrodes 2104 of the ion trap 2102. Advantageously, the principal optical axes 512 of respective optical fibre receiving members 514 and optical fibres 112 received therein are aligned to coincide at a point 520 within the ion trap 2102, thereby to enable illumination and collection of trapped ions at the point 520 within the ion trap 2102. Whilst the arrangement shown at Figure 21 illustrates an example of a number of principal optical axes 512 corresponding to optical fibres 112 received in optical fibre receiving members 514 of a support body 102, in further examples, the vacuum viewport support body 102 is arranged to enable any appropriate number of optical pathways to coincide within the ion trap 2102 within the hermetically sealed vacuum chamber 2000. Whilst Figure 21 illustrates a vacuum system comprising an ion trap, in further examples the vacuum system alternatively or additionally comprises an atom trap. In further examples, the vacuum system comprises any appropriate additional or alternative apparatus to provide one or more target positions for the illumination and / or collection of light.

[0108] Figures 20 and 21 illustrate vacuum systems wherein the plurality of optical fibre receiving members and respective lenses are arranged thereby to direct light between optical fibres in the recesses and one or more predetermined target positions within the vacuum chamber. Optionally the one or more predetermined target positions are associated with one or more objects. Optionally the one or more objects comprise: one or more trapped ions, and / or one or more neutral atoms and / or one or more nitrogen vacancies and / or one or more quantum dots.

[0109] The vacuum viewport member described with reference to Figures 1 to 21 may be produced by integrally forming the plurality of lenses in the first surface of the support body and integrally forming the plurality of recesses in the second surface of the support body. Optionally, integrally forming the plurality of lenses and / or the plurality of optical fibre receiving members comprises selective laser etching and / or focussed ion beam milling.

[0110] Advantageously, the use of vacuum viewport members described herein, in combination with subsystems in a vacuum chamber can provide compact optical apparatuses that enable optical processes, such as quantum computing processes, to be scaled through the provision of multiple, compact, systems. Beneficially, the arrangement of lenses in vacuo and optical fibre receiving members ex vacuo provides an elegant, compact hermetically sealed system in which target objects can be illuminated / measured in an improved manner, in three dimensions, whilst under different environmental conditions to further apparatus that can be positioned ex vacuo. CROSS REFERENCE TO RELATED APPLICATIONS

[0111] This application claims priority from GB 2407986.5 filed on 5 June 2024, the contents of which are hereby incorporated by reference.

Claims

CLAIMS:

1. A vacuum viewport member comprising: a support body; a plurality of lenses defined by or provided on a first surface of the support body; a plurality of optical fibre receiving members defining a plurality of recesses, wherein at least an axial end of each recess of the plurality of recesses is formed by a portion of a second surface of the support body opposite to the first surface, wherein each recess of the plurality of recesses is arranged to receive an optical fibre corresponding to a respective lens of the plurality of lenses.

2. The vacuum viewport member according to claim 1, wherein the plurality of optical fibre receiving members and respective lenses are arranged: to direct light from optical fibres in the plurality of recesses towards one or more target positions that are predetermined relative to the first surface; and / or to direct light from one or more target positions that are predetermined relative to the first surface towards optical fibres in the plurality of recesses.

3. The vacuum viewport member according to any preceding claim, wherein at least a subset of the plurality of lenses has respective optical axes pointing in different directions.

4. The vacuum viewport member according to claim 3, wherein the optical axes of two or more of the subset of the plurality of lenses substantially intersect with each other at one or more target positions that are predetermined relative to the first surface.

5. The vacuum viewport member according to claim 3 or 4, wherein the subset of the plurality of lenses has respective optical axes pointing in a direction substantially parallel to the respective longitudinal axes of a subset of the plurality of recesses.

6. The vacuum viewport member according any preceding claim, wherein the support body is integrally formed7. The vacuum viewport member according to any of claims 1 to 5, wherein the support body comprises: a first integrally formed portion comprising the plurality of lenses; and a second integrally formed portion comprising the plurality of recesses.

8. The vacuum viewport member according to claim 7, wherein the first integrally formed portion comprises a mating surface opposite the first surface and the second integrally formed portion comprises a mating surface opposite the second surface, wherein the mating surface of the first integrally formed portion faces the mating surface of the second integrally formed portion.

9. The vacuum viewport member according to claim 8, wherein the support body comprises one or more layers at least partially between the mating surface of the first integrally formed portion and the mating surface of the second integrally formed portion.

10. The vacuum viewport member according to claim 9, wherein the one or more layers comprise refractive index matching material.

11. The vacuum viewport member according to claim 8, wherein at least part of the mating surface of the first integrally formed portion is in optical contact with at least part of the mating surface of the second integrally formed portion, thereby to reduce light scattering at the interface between the mating surface of the first integrally formed portion and the mating surface of the second integrally formed portion.

12. The vacuum viewport member according to any of claims 7 to 11, wherein the first integrally formed portion and / or the second integrally formed portion comprise one or more alignment features, thereby to enable alignment of the first integrally formed portion with the second integrally formed portion, optionally wherein the one or more alignment features comprise fiducial markers and / or registration features.

13. The vacuum viewport member according to any preceding claim, wherein the first surface comprises a coating.

14. The vacuum viewport member according to claim 12, wherein the coating is an anti- reflective coating.

15. The vacuum viewport member according to claim 13 or claim 14, wherein the coating comprises an electrically conductive material, optionally wherein the electrically conductive material forms at least part of one or more electrical circuits.

16. The vacuum viewport member according to any preceding claim, wherein the vacuum viewport member comprises optical shielding arranged to reduce optical crosstalk associated with light from different lenses of the plurality of lenses.

17. The vacuum viewport member according to claim 16, wherein the optical shielding comprises one or more shielding layers at least partially between the first surface and the second surface, optionally wherein, when dependent on any of claims 8 to 12, the one or more shielding layers are positioned at least partially between the mating surface of the first integrally formed portion and the mating surface of the second integrally formed portion.

18. The vacuum viewport member according to claim 16 or 17, wherein the optical shielding comprises one or more trenches in the support body, optionally wherein the one or more trenches are at least partially filled with an optical shielding material, optionally wherein the optical shielding material comprises a metal.

19. The vacuum viewport member according to any preceding claim, comprising refractive index matching material at least partially within at least one of the recesses defined by at least one of the plurality of optical fibre receiving members, thereby to reduce light scattering between an optical fibre in the recess of the at least one of the plurality of recesses and the support body.

20. The vacuum viewport member according to any preceding claim, wherein the first surface comprises one or more location features configured to locate one or more components relative to the plurality of lenses, optionally wherein the one or more location features comprise one or more fiducial markers and / or registration features.

21. The vacuum viewport member according to any preceding claim, wherein the plurality of lenses comprises at least one microlens having an outermost diameter of less than or equal to 1000 microns.

22. The vacuum viewport member according to any preceding claim, wherein the plurality of lenses comprises at least one lens having a spherical profile and / or at least one lens having an aspherical profile and / or at least one lens having a Fresnel profile.

23. The vacuum viewport member according to any preceding claim, wherein the support body is at least partially formed from material comprising at least one of: glass, fused silica, borosilicate glass and silicon.

24. A vacuum system comprising a vacuum chamber and the vacuum viewport member according to any preceding claim, wherein the vacuum viewport member is configured to form a hermetically sealed part of the vacuum chamber thereby to enable a pressure differential to be created between the environment within the vacuum chamber and the environment outside the vacuum chamber, wherein the first surface faces into the vacuum chamber.

25. The vacuum system according to claim 24, wherein the vacuum system further comprises in the vacuum chamber at least one of: an ion trap and an atom trap.

26. The vacuum system according to claim 24 or claim 25, wherein the plurality of optical fibre receiving members and respective lenses are arranged thereby to direct light between optical fibres in the recesses and one or more predetermined target positions within the vacuum chamber, optionally wherein the one or more predetermined target positions are associated with one or more objects, optionally wherein the one or more objects comprise: one or more trapped ions, and / or one or more neutral atoms and / or one or more nitrogen vacancies and / or one or more quantum dots.

27. A method of producing the vacuum viewport member according to any of claims 1 to 24, the method comprising the steps of: integrally forming the plurality of lenses in the first surface of the support body; andintegrally forming the plurality of recesses in the second surface of the support body, optionally wherein integrally forming the plurality of lenses and / or the plurality of optical fibre receiving members comprises selective laser etching and / or focussed ion beam milling.

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