Microelectromechanical-System-Based Design of a High-Finesse Fiber Cavity Integrated with an Ion Trap

Abstract

We present a numerical study of a MEMS-based design of a fiber cavity integrated with an ion trap system. Each fiber mirror is supported by a microactuator that controls the mirror's position in three dimensions. The mechanical stability is investigated by a feasibility analysis showing that the actuator offers a stable support of the fiber. The actuators move the fibers' positions continuously with a stroke of more than 10 µm, with mechanical resonance frequencies on the order of kHz. A calculation of the trapping potential shows that a separation between ion and fiber consistent with strong ion-cavity coupling is feasible. Our miniaturized ion-photon interface constitutes a viable approach to integrated hardware for quantum information. * These authors contributed equally to this work. † tracy.northup@uibk.ac.at ‡ dicho@snu.ac.kr Au electrodes on fused silica. A MEMS surface ion trap has smaller trap depth than a three-dimensional Paul trap [19] but has the advantage of a reconfigurable planar trapping geometry, along with extensive optical access for laser beams, as required for a large-scale ion trap quantum computer. In 2016, a MEMS trap called the High Optical Access 2.0 trap was developed by Sandia National Laboratory [20], which is widely used by many ion trap researchers today. Topics of active research include the question of how to reduce stray charge accumulation, e.g., on the trap sidewalls [21] or via in situ cleaning [22,23], and how to build increasingly sophisticated structures, e.g., junction traps [24,25] for ion transport, and two-or three-dimensional electrode arrays [26,27].MEMS-based ion traps have advantages in scalability and ease of fabrication, and they can also be easily integrated with other type of MEMS devices. MEMS techniques can also reduce the footprint of the optical cavity system [28,29], particularly for the mirror actuators. The replacement of standard high-finesse mirrors by fiber mirrors has already reduced the physical cavity volume significantly [30,31]; however, when commercial nanopositioning stages are used, they place significant space demands on the in-vacuum assembly. Here, we propose and investigate a novel design for a MEMS-based fibercavity system integrated with a surface ion trap. The fiber system is studied by analyzing the mechanical stability, resonances, and stroke. Furthermore, we calculate the trapping potential seen by the ions in order to discuss the prospects for strong ion-cavity coupling. II. BASIC CONCEPTThe main structure consists of a surface ion trap integrated with a MEMS-based fiber cavity system ( Fig. 1(a)). The starting point is a microfabricated chip, arXiv:1907.07594v1 [quant-ph]

Achievements and perspectives of optical fiber Fabry–Perot cavities

“…via piezo-electric elements [6,27,28]. This design paradigm is achieved through rigid device geometries, where the opposing mirrors of the FFPC are supported in close vicinity to a common base [27,28,31].…”

“…To increase the functionality of FFPCs other elements such as mechanical or electrical components can be integrated into the FFPC geometry or the FFPC itself is embedded into miniaturized experiment designs e.g. chip-based ion trap experiments [31]. In the particular example of ion traps the advantage of small mode-volumes of FFPCs is usually not fully exploited because of uncontrolled charging of the dielectric fiber mirrors.…”

“…At the present time investigations are underway with respect to numerous technical improvements especially with regard to ion coupled FFPCs: Unwanted stray fields are to be controlled by means of integrated electrodes (see Sect. 2.8); a natural extension of FFPCs is integration with miniaturized ion traps [42,44,48]; improved mirror fabrication for long cavities can mitigate problems with charging of dielectric surfaces [31].…”

“…Whilst FFPCs like macroscopic optical cavities can make use of large intracavity photon numbers n c (up to Watts of optical power in high finesse cavities) to boost the linearized optomechanical coupling strength g = √ n c ⋅ g 0 , other platforms experience limitations caused by heating and thermal instabilities. As FFPCs can be integrated to on-chip platforms [31], be used to interface very miniaturized mechanical elements, and as they are able to reach large finesse together with strong optomechanical coupling strengths [26], they continue to be a favorable platform for cavity optomechanical experiments, especially superior where large intracavity optical powers are required.…”

Achievements and Perspectives of Optical Fiber Fabry-Perot Cavities

“…via piezo-electric elements [5,22,23]. This design paradigm is achieved through rigid device geometries, where the opposing mirrors of the FFPC are supported in close vicinity to a common base [22,23,26].…”