Artificial resonator waveguide

Abstract

Photonic circuits and optical resonators are described. An optical resonator element includes: at least one photonic layer formed of a material having selected electro-optical properties; an electrode arrangement comprising at least a first top electrode arrangement and a second bottom electrode arrangement positioned at opposite first and second faces of the at least one photonic layer. At least one of the first top electrode arrangement and the second bottom electrode arrangement includes an electrode arrangement defining an annular or straight artificial resonator structure. In response to a potential applied to the one or more electrodes of the electrode arrangement, the refractive index varies in a respective region of the at least one photonic layer affected by the one or more electrodes, thereby selectively defining an annular or straight waveguide within the at least one photonic layer.

Description

Technical Field

[0001] This disclosure relates to photonic resonators, and more particularly to controllable artificial and virtual photonic resonators. Background Technology

[0002] The growing demand for highly integrated photonic circuits presents even greater challenges to the development of high-fidelity, high-density photonic chips. These challenges are further amplified in the context of photonic circuits operating at the single-photon level for quantum applications.

[0003] Optical resonators, including straight resonators and ring resonators, are typically formed by certain optical paths in which signals with specific parameters (usually wavelengths) resonate. Optical ring resonators are typically formed by ring waveguides, usually associated with one or more input / output waveguides. When light is coupled into the ring resonator through the input waveguide, the coupled light can propagate through the ring, undergoing multiple round trips. Due to constructive and destructive interference, the input signal satisfies the resonance condition if the optical path length around the ring resonator is an integer multiple of the wavelength of the light. Therefore, ring resonators provide sharp transmission and peak amplification at a specific resonant wavelength. A typical straight or linear resonator is formed by two reflecting surfaces (e.g., mirrors) facing each other, with an optical medium such as a waveguide section between them. Linear resonators allow light to bounce back and forth between the mirrors, thus forming a standing wave pattern. The distance between the mirrors and the refractive index of the optical medium determine the resonant frequency of the cavity, thus allowing only certain wavelengths of light to constructively interfere and form resonant modes. This type of resonator is fundamental in laser design, enhancing the coherence and stability of the laser output.

[0004] The fidelity and quality of optical resonators are typically determined by parameters such as the Q factor and fineness. The ever-growing demand for integrated photonic circuits presents similar, and sometimes even more challenging, challenges for developing improved optical resonators.

[0005] To address this challenge, efforts are underway to develop new technologies and materials suitable for photonic circuits and corresponding optical components. Various such studies focus on the electro-optic properties of different materials, typically described by the Pockels or Kerr effect, which defines the material's refractive index in response to changes in an external electric field. See, for example: Ali K. Hamze et al. , Design rules for strong electro-optic materials,NPJ Computational Materials 6, 130 (2020). Beskin et al., Growth and Structure of Strong Pockels Material StrontiumBarium Niobate on SrTiO3and Si by Molecular Beam Epitaxy (2021). Adv. Res., 2: 2100111. https: / / doi.org / 10.1002 / adpr.202100111. Valentin et al. , Lead-Free Perovskite Thin Films with Tailored Pockels-Kerr Effects for Photonics (2023). ACS Applied Materials&Interfaces 15 (31),38039-38048, DOI: 10.1021 / acsami.3c06499. Mian Zhang et al. , Integrated lithium niobate electro-optic modulators:when performance meets scalability (2021). Optica 8, 652-667. Agham B. Posadas et al. , RF-sputtered Z-cut electro-optic bariumtitanate modulator on silicon photonic platform (2023). J. Appl. Phys. 134(7): 073101. K. Nashimoto et al. , High-speed PLZT optical switches for burst andpacket switching (2005). 2nd International Conference on Broadband Networks ,Boston, MA, USA, 2005, pp. 1118-1123, Volume 2, doi: 10.1109 / ICBN.2005.1589732. G. Chen, H. -L. Lin, J. D. Ng, and A. J. Danner, Integrated Electro-Optic Modulator in Z-Cut Lithium Niobate Thin Film With Vertical Structure (2021). IEEE Photonics Technology Letters , Vol. 33, No. 23, pp. 1285 - 1288, doi: 10.1109 / LPT.2021.3114993. A. Karvounis, F. Timpu, V. V. Vogler-Neuling, R. Savo, R. Grange, Barium Titanate Nanostructures and Thin Films for Photonics. Adv. Optical Mater. 2020, 8, 2001249. Chengli Wang et al. , Lithium tantalate electro-optical photonic integrated circuits for high volume manufacturing, arXiv:2306.16492. Quack, N., Takabayashi, A.Y., Sattari, H. And others. Integrated silicon photonic MEMS. Microsyst Nanoeng 9, 27 (2023). https: / / doi.org / 10.1038 / s41378-023-00498-z. Suraj, Shankar Kumar Selvaraja, Highly Oriented PZT Platform for Polarization-Independent Photonic Integrated Circuit and Enhanced Efficiency Electro-Optic Modulation, arXiv:2305.19126. Li, Z., Wang, R.N., Lihachev, G. And others.High density lithium niobate photonic integrated circuits. Nat Commun 14, 4856 (2023). https: / / doi.org / 10.1038 / s41467-023-40502-8. Xianwen Liu, Alexander W. Bruch and Hong. X. Tang, "Aluminum nitride photonic integrated circuits: from piezo-optomechanics to nonlinear optics," Adv. Opt. Photon. 15, 236-317 (2023). Ma, X., Cai, Z., Zhuang, C. And others. Integrated microcavity electric field sensors using Pound-Drever-Hall detection. Nat Commun 15, 1386 (2024). https: / / doi.org / 10.1038 / s41467-024-45699-w. Zhang, K., Sun, W., Chen, Y. And others. A power-efficient integrated lithium niobate electro-optic comb generator. Commun Phys 6, 17 (2023). https: / / doi.org / 10.1038 / s42005-023-01137-9. Churaev, M., Wang, R.N., Riedhauser, A. And others. A heterogeneously integrated lithium niobate-on-silicon nitride photonic platform. Nat Commun 14, 3499 (2023). https: / / doi.org / 10.1038 / s41467-023-39047-7. Li, M., Ling, J., He, Y. And others.Lithium niobate photonic-crystalelectro-optic modulator. Nat Commun 11, 4123 (2020). https: / / doi.org / 10.1038 / s41467-020-17950-7. Various publications relate to circular resonators and EO tunability, including the inventor's work, which utilizes external air for mode confinement, as is common in conventional prior art: M. Rosenblit, P. Horak, E. Fleminger, Y. Japha and R. Folman, Design ofmicrocavity resonators for single-atom detection. J. Nanophoton. 1, 011670(2007), Special issue. M. Rosenblit, Y. Japha, P. Horak, and R. Folman, Simultaneous opticaltrapping and detection of atoms by microdisk resonators. Phys. Rev. A 73,063805 (2006). M. Rosenblit, P. Horak, S. Helsby, and R. Folman, Single-atom detection using whispering gallery modes of microdisk resonators, Phys. Rev. A 70,053808 (2004). The literature describes various materials and techniques that enable electro-optic effects and allow for integration in photonic and electro-optic circuits. These techniques utilize waveguides and electro-optic components formed from barium titanate (BTO), lithium niobate, lead zirconate titanate (PLZT), and other materials with properties that produce significantly large Pockels coefficient values. Summary of the Invention

[0006] Optical processing and photonic circuits enable high-speed computing in both classical and quantum realms and lay the foundation for a wide range of light sources, sensors, and communication systems. Some typical components in such circuits include optical resonators, including linear and ring resonators. The realization of various optical resonators currently faces numerous obstacles. For example, a significant obstacle to utilizing resonators and photonic circuits involves intensity loss due to light scattering. While this can be addressed in some classical photonic circuits by increasing power, this loss limits quantum applications and reduces the Q-factor and fineness of the resonator. In general, waveguide loops typically have several sources of loss, even if the material does not have internal material absorption. These include, for example, bending losses associated with the circuit geometry, losses from internal geometric defects, and losses due to light scattering caused by edge roughness associated with waveguide fabrication techniques. In this regard, edge roughness involves sidewall roughness and surface roughness. Although the top and bottom surfaces can be treated to reduce roughness (e.g., with chemical mechanical polishing (CMP)), sidewall roughness remains a challenge in standard techniques.

[0007] An additional obstacle typically associated with conventional photonic circuits involves the control of the phase of propagating light. Conventional waveguides are typically made of materials limited to those without electro-optic (EO) effects, such as silicon nitride (SiN), and phase-shifting elements are usually implemented by heating the waveguide region. This technique suffers from several drawbacks, such as chip thermal load, long rise / fall times due to the thermal capacity and conductivity of the material and its surroundings, and significant crosstalk. The latter drawback relates to the thermal conductivity of the waveguide and its surroundings, as heat is not a highly localized property. Alternatively, efforts are being made to combine EO materials with conventional waveguides, placing the EO material outside the waveguide to interact with the evanescent field of the optical mode. Fabrication of such systems requires complex work and has minimal impact on most optical modes. Another problem with conventional waveguides and photonic circuits involves the stability of the circuit to uncontrollable phase noise caused by thermal and vibrational noise. As indicated above, conventional waveguides are typically made of non-EO materials, resulting in limited ability to correct phase fluctuations with high bandwidth in real time. Another problem in conventional circuits is high fidelity, which is required for high-end applications such as AI accelerators or quantum information processing. This fidelity is often affected by insufficient manufacturing precision (and circuit parameters are fixed during manufacturing and cannot be dynamically changed).

[0008] Another example of the current drawbacks, and perhaps one of the biggest problems, is the fixed nature of existing photonic circuits, which are based on fixed fabricated components. Because waveguides and other photonic components are based on fixed fabricated components, this limits variability (i.e., there is no programmability, as in FPGAs), limits the ability to correct for any changes caused by manufacturing problems, and limits the ability to respond quickly to thermal and vibration noise, as mentioned above.

[0009] For the first time, a new generation of electro-optic materials with sufficiently high Pockels can confine optical modes solely by means of the refractive index difference generated by applying an electric field to the material. That is, the applied electric field can define a waveguide, and since there is no air around the waveguide (or no physical intervention, such as ion implantation, to affect the refractive index), no etching of the waveguide or its surroundings is required. Such etching can include physical and / or chemical etching or other processes that permanently alter the material's structure, including, for example, ion bombardment. For instance, circuits made from the popular EO material lithium niobate (LiNbO3) typically require etching to create the waveguide arrangement.

[0010] In this regard, various materials, including BaTiO3 (BTO) and lithium niobate (LiNbO3 or LN), are first examples of this new generation of materials, while the production roadmap for new materials with a stronger Pockel effect is described in the work of Ali K. Hamze et al. listed above. Therefore, various photonic elements and resonators according to this disclosure can be used with BTO or lithium niobate and can be continuously improved according to the development roadmap listed above. While BTO still exhibits significant internal absorption and is suitable for photonic circuits with classical light (e.g., for AI accelerators), the new materials roadmap will provide materials with lower absorption coefficients, becoming similar to the low absorption of quartz crystals, and thus suitable for quantum optics applications. In some configurations, BTO can have small absorption, whereby a small frequency gap between absorption modes enables narrow-linewidth lasers to operate with low absorption. Alternatively, increasing the band gap of BTO, for example, by stretching the material when thin layers of the material are sandwiched between layers with other lattice constants, can also eliminate or at least significantly reduce the absorption of the BTO layers. Therefore, the technology disclosed herein can be used with BTO, lithium niobate, or any other material having a high Pockel coefficient. For example, this disclosure can utilize materials having a Pockel coefficient of 100 pm / V and higher, or 200 pm / V and higher, or 300 pm / V and higher, or 400 pm / V and higher, or 500 pm / V and higher, or 600 pm / V and higher, or 700 pm / V and higher, or 800 pm / V and higher, or 900 pm / V and higher, or 1000 pm / V and higher.

[0011] The artificial optical resonator elements produced according to the description in this disclosure can provide various advantages over conventional optical resonators manufactured by etching. For example, as described in more detail below, a change in the voltage applied between the electrodes alters the refractive index in the photonic layer. Therefore, by changing the electric field applied by the respective electrodes, the resonant wavelength of the optical resonator can be fine-tuned to a desired wavelength. Similarly, since resonators typically experience resonant wavelength drift due to temperature and acoustic fluctuations, the techniques of this invention enable rapid control of the refractive index (large bandwidth), thereby achieving effective correction (locking) of the resonant wavelength.

[0012] Furthermore, and most importantly, an electric field is used to alter the refractive index of regions of the photonic layer to create artificial waveguides, thereby reducing scattering due to edge (sidewall) roughness. This has the potential to significantly reduce the complexity and cost of resonator fabrication, for example, by eliminating or at least reducing the need for special treatments to reduce roughness, while further improving the quality factor Q, a performance metric for these resonators.

[0013] More specifically, the edge roughness in the resonator according to the embodiments of this disclosure can be reduced for two reasons: 1. There is greater technical knowledge in manufacturing low-roughness edges of the metal layer, especially when the metal layer is very thin; 2. The effective roughness decreases exponentially with the ratio of the distance between the electric field source (in this case, the metal electrode) and the point of interest within the photonic layer to the wavelength used. In practice, this means that if the distance between the metal electrode and the center of the photonic layer is 500 nm, the roughness at wavelengths less than 500 nm will decrease exponentially. Therefore, the roughness of the metal electrode is hardly transferred to the artificial wall of the photonic waveguide generated by the electric field.

[0014] Furthermore, the use of electrode arrangements allows for the controllability of light coupled into or out of the resonator. As described in more detail below, photonic circuits can utilize one or more coupling control electrodes located near one or more ring resonator electrodes. These one or more coupling control electrodes can be configured to generate a controllable coupling gate. Thus, by applying a voltage to the coupling control (or gate) electrode (assuming the resonator electrode is under voltage), the electric field generated by the gate electrode changes the refractive index, thereby achieving optical coupling between the resonator and the waveguide of the circuit. If no voltage is applied to the gate electrode, light crossing is prevented, and the resonator is isolated. For a perfect resonator, a high Q and fineness value will allow light to circulate within the resonator without coupling. Scattering losses are generally minimized by the techniques disclosed herein, thus eliminating rough edges; however, absorption due to material properties can shorten the lifetime of the signal within the resonator. The ability to isolate the ring resonator allows it to be used as a memory cell or delay line. The absence of coupling to a nearby waveguide allows light to circulate undisturbed within the resonator and enables the resonator to achieve a high Q and fineness value. Therefore, the ability to electronically switch the coupling on and off with high precision makes it possible to use a ring resonator as a memory cell or delay line.

[0015] Finally, as indicated above, this disclosure also provides a linear (straight) artificial resonator configuration. Such a linear resonator can be made from a straight waveguide portion forming a Fabry-Perot resonator, with Bragg mirrors on each side, thereby fabricating the Bragg mirrors by modulating an electric field along the waveguide axis (or by some other method, such as ion implantation to modulate the refractive index). In this case, the problem of bending loss disappears, and the resonator can be made to any size using available materials such as lithium niobate, depending on the desired resonant wavelength. The advantages of this new technique are: 1. Edge roughness is again a limiting factor, and as explained, the new technique reduces edge roughness; 2. If the mirror is fabricated by modulating an electric field, the reflectivity of the mirror can be selectively changed at any time by changing the voltage, thereby controlling when light leaves the cavity; 3. Changing the waveguide refractive index can change the effective length of the cavity, thus providing the ability to make high-bandwidth changes to the resonant wavelength (e.g., to suppress acoustic and thermal noise).

[0016] Therefore, according to a broad aspect, this disclosure provides a photonic circuit including at least one resonator element comprising: at least one photonic layer formed of a material having selective electro-optic properties; an electrode arrangement structure including at least a first top electrode arrangement structure and a second bottom electrode arrangement structure positioned at opposing first and second surfaces of the at least one photonic layer; wherein at least one of the first top electrode arrangement structure and the second bottom electrode arrangement structure includes an electrode arrangement structure defining a ring structure, and wherein, in response to a potential applied to one or more electrodes of the electrode arrangement structure, the refractive index varies in a corresponding region of the at least one photonic layer affected by the one or more electrodes, thereby selectively defining a ring waveguide within the at least one photonic layer.

[0017] According to some embodiments, at least one resonator element is an artificial resonator. More specifically, at least one resonator element is defined by a region of at least one photonic layer affected by at least a first top electrode arrangement and a second bottom electrode arrangement. The refractive index of the at least one resonator element through the region of the at least one photonic layer responds to changes in the electric field applied by the electrode arrangement.

[0018] According to some implementations, at least one of the first top electrode arrangement and the second bottom electrode arrangement may include a circular electrode defining a ring resonator waveguide.

[0019] According to some implementation schemes, the photonic circuit may further include a first cladding layer and a second cladding layer located at a first surface and a second surface of at least one photonic layer, the first cladding layer being located between at least one photonic layer and a first top electrode arrangement, and the second cladding layer being located between at least one photonic layer and a second bottom electrode arrangement.

[0020] According to some embodiments, at least one of the first top electrode arrangement and the second bottom electrode arrangement may include a plurality of independently controlled point electrodes positioned on at least one surface of at least one photonic layer, and wherein applying a voltage to a set of point electrodes along a selected region defines a photonic circuit in which light propagates in a corresponding region of at least one photonic layer.

[0021] According to some implementation schemes, the selected electro-optic properties include the Pockel coefficient, which defines the response to changes in refractive index in response to a DC electric field.

[0022] According to some embodiments, at least one photonic layer comprises a material having at least one Pockel coefficient of 100 pm / V or higher. According to some embodiments, at least one photonic layer comprises a material having at least one Pockel coefficient of 200 pm / V and higher, or 300 pm / V and higher, or 400 pm / V and higher, or 500 pm / V and higher, or 600 pm / V and higher, or 700 pm / V and higher, or 800 pm / V and higher, or 900 pm / V and higher, or 1000 pm / V and higher.

[0023] According to some implementation schemes, at least one photonic layer is formed of lithium niobate or BTO (BaTiO3).

[0024] According to some embodiments, the photonic circuit may also include a control unit, which includes at least one processor and memory circuit, the control unit being electrically connected to the electrodes of the first top electrode arrangement and the electrodes of the second bottom electrode arrangement, and being configured to selectively apply voltage to the electrodes to operate at least one resonator element.

[0025] According to some implementations, the control unit is also configured to selectively apply voltage to the electrodes to determine one or more resonant wavelengths of at least one resonator element.

[0026] According to some implementation schemes, the electrode arrangement structure includes electrodes formed of a transparent conductive material.

[0027] According to some implementation schemes, the electrode arrangement structure includes metal electrodes, wherein the metal electrodes are thin enough to eliminate the absorption of light by the metal electrodes.

[0028] According to some implementation schemes, the electrode arrangement includes crystalline electrodes characterized by narrow absorption peaks. For example, the crystalline electrodes can be formed on graphene or other crystalline materials.

[0029] According to some embodiments, the photonic circuit may also include at least one top gate electrode located near a first top electrode arrangement defining at least one resonator element, such that applying a voltage to the at least one top gate electrode provides a varying refractive index in a region of the photonic layer, thereby operating as a gate for coupling an optical signal to at least one resonator element.

[0030] According to some implementation schemes, at least one resonator element can operate as a filter.

[0031] According to some implementation schemes, at least one resonator element can operate as a switch.

[0032] According to some implementations, at least one resonator element can operate as a reflector or a delay line.

[0033] According to some implementation schemes, at least one resonator element can be operated as a reference standard for frequency locking.

[0034] According to some implementations, at least one resonator element can be operated as a sensor or detector for single or microparticles.

[0035] According to some implementations, at least one resonator element can operate as a quantum device, such as a frequency comb, or an entanglement of photons and / or atoms.

[0036] According to some implementations, the photonic circuit may include at least a first ring resonator element and a second ring resonator element coupled therebetween, wherein each of the first and second resonator elements is defined by at least a first top electrode arrangement having a circular portion.

[0037] According to some embodiments, the photonic circuit may also include at least one additional electrode arrangement configured to define at least one linear waveguide configured to couple an optical signal into or out of at least one resonator element.

[0038] According to some implementation schemes, a change in the potential applied to one or more electrodes of the electrode arrangement structure enables control over the change in the resonant wavelength of at least the resonant element.

[0039] According to another broad aspect, this disclosure provides a photonic circuit including at least one resonator element comprising: at least one photonic layer formed of a material having selected electro-optic properties; an electrode arrangement including at least a first top electrode arrangement and a second bottom electrode arrangement positioned at opposing first and second surfaces of the at least one photonic layer; wherein at least one of the first top electrode arrangement and the second bottom electrode arrangement includes an electrode arrangement defining at least a first discontinuity region and a second discontinuity region in the electrodes along an elongated region; and wherein, in response to a potential applied to one or more electrodes of the electrode arrangement, the refractive index varies in a corresponding region of the at least one photonic layer affected by the one or more electrodes, thereby selectively defining at least a first refractive index interface and a second refractive index interface associated with the first discontinuity region and the second discontinuity region, thereby defining a resonator within the at least one photonic layer.

[0040] According to some embodiments, at least one resonator element is an artificial resonator. More specifically, at least one resonator element is defined by a region of at least one photonic layer affected by at least a first top electrode arrangement and a second bottom electrode arrangement. The refractive index of the at least one resonator element through the region of the at least one photonic layer responds to changes in the electric field applied by the electrode arrangement.

[0041] According to some embodiments, the artificial resonator is defined by a straight waveguide electrode portion and two or more electrodes, the two or more electrodes defining the at least first discontinuity region and the second discontinuity region and configured to change the refractive index at both ends of the straight waveguide electrode portion, thereby defining a straight waveguide portion forming a Fabry-Perot resonator with a Bragg mirror on each side.

[0042] According to some implementation schemes, the photonic circuit may further include a first cladding layer and a second cladding layer located at a first surface and a second surface of at least one photonic layer, the first cladding layer being located between at least one photonic layer and a first top electrode arrangement, and the second cladding layer being located between at least one photonic layer and a second bottom electrode arrangement.

[0043] According to some embodiments, at least one of the first top electrode arrangement and the second bottom electrode arrangement includes a plurality of independently controlled point electrodes positioned on at least one surface of at least one photonic layer, and wherein applying a voltage to a set of point electrodes along a selected region defines a photonic circuit in which light propagates in a corresponding region of at least one photonic layer.

[0044] According to some implementation schemes, the selected electro-optic properties include the Pockel coefficient, which defines the response to changes in refractive index in response to a DC electric field.

[0045] According to some embodiments, at least one photonic layer comprises a material having at least one Pockel coefficient of 100 pm / V or higher. According to some embodiments, at least one photonic layer comprises a material having at least one Pockel coefficient of 200 pm / V and higher, or 300 pm / V and higher, or 400 pm / V and higher, or 500 pm / V and higher, or 600 pm / V and higher, or 700 pm / V and higher, or 800 pm / V and higher, or 900 pm / V and higher, or 1000 pm / V and higher.

[0046] According to some implementation schemes, at least one photonic layer is formed of lithium niobate or BTO (BaTiO3).

[0047] According to some embodiments, at least one photonic circuit may further include a control unit, which includes at least one processor and memory circuit, the control unit being electrically connected to the electrodes of the first top electrode arrangement and the electrodes of the second bottom electrode arrangement, and being configured to selectively apply voltage to the electrodes to operate at least one resonator element.

[0048] According to some implementations, the control unit is also configured to selectively apply voltage to the electrodes to determine one or more resonant wavelengths of at least one resonator element.

[0049] According to some implementations, at least one electrode arrangement structure includes electrodes formed of a transparent conductive material.

[0050] According to some embodiments, at least one electrode arrangement structure includes a metal electrode, wherein the metal electrode is thin enough to eliminate the absorption of light by the metal electrode.

[0051] According to some implementation schemes, at least one electrode arrangement includes a crystalline electrode characterized by a narrow absorption peak. Attached Figure Description

[0052] To better understand the subject matter disclosed herein and to illustrate how it can be implemented in practice, implementation methods will now be described by way of non-limiting example only, with reference to the accompanying drawings, in which: Figure 1 A photonic circuit system including at least one ring resonator element according to some embodiments of the present disclosure is schematically illustrated; Figure 2 An additional photonic circuit system comprising at least one ring resonator element and utilizing a cladding is schematically illustrated according to some embodiments of the present disclosure; Figure 3 The Pockels coefficients of several materials exhibiting electro-optic response are shown; Figure 4A and Figure 4B This illustrates a BTO waveguide (BTO waveguide) formed according to some embodiments of this disclosure. Figure 4A ) and lithium niobate waveguide ( Figure 4B Comsol simulation of the optical modes supported by the system; Figure 5 A side view of a portion of a photonic circuit system according to some embodiments of the present disclosure is illustrated, and waveguide formation in the circuit is also illustrated. Figure 6 Photonic circuits including ring resonators according to some embodiments of the present disclosure are illustrated; Figure 7A and Figure 7B Examples of ring resonators coupled to waveguide sections according to some embodiments of this disclosure are illustrated. Figure 7A ) and ring resonators coupled via controlled coupling (gated resonators) Figure 7B ); Figure 8 An arrangement of two coupled ring resonators providing selective (filtering) reflection elements according to some embodiments of this disclosure is illustrated; Figure 9A and Figure 9B An example is illustrated of a ring resonator coupled to both sides of a waveguide according to some embodiments of the present disclosure, which provides a filter transfer element from one waveguide to another. Figure 9A A parallel waveguide is illustrated, and Figure 9B An example of a cross waveguide is shown; Figure 10 An additional arrangement of two coupled ring resonators according to some embodiments of this disclosure is illustrated; Figure 11 Pixel-shaped electrode configurations of configurable photonic circuit systems according to some embodiments of the present disclosure are illustrated; Figure 12 The simulation fineness (number of turns) of a resonator formed using the techniques of this disclosure is shown, wherein 10-1 turns are present in a 1 μm thick layer of LiNbO3 (δn=0.0016) and BaTiO3 (δn=0.06) with currently existing absorption coefficients. 7 Vertical electric field of V / m; Figure 13 It shows the use of 10 7 Analytical calculations and numerical simulations of electric field V / m, quality factor and lifetime of BTO ring resonators with different radii assuming BTO Pockel coefficient; Figure 14 The analytical calculations and numerical simulations of the quality factor and lifetime of ring resonators with different radii and different refractive index variations are shown.

[0053] Figure 15A and Figure 15B Linear resonator configurations according to some embodiments of this disclosure are illustrated. Figure 15A A side view of a linear resonator is illustrated, showing the electrode arrangement placed at the top and bottom of the photonic layer. Figure 15B A top view of a linear resonator illustrating the resonator cavity and the reflecting end is shown. Detailed Implementation

[0054] As indicated above, this disclosure provides a photonic circuit system suitable for a wide range of applications, such as photonic sensors, clocks, information processing and communications, and quantum photonics, as well as one or more photonic resonator elements suitable for photonic circuits. Such photonic resonator elements may include one or more ring resonators formed by a circular electrode arrangement defining a ring resonator, and linear resonator elements formed by an electrode arrangement defining a linear waveguide portion including a back-reflection region and a front-reflection region (e.g., a mirror). The photonic circuit system of this disclosure utilizes at least one optical resonator based on at least one photonic layer (also referred to as an active substrate layer (ASL)), and an electrode arrangement positioned and operable to apply an electric field to selected regions of the photonic layer. The at least one photonic layer is formed of a material having selected electro-optic properties, and more specifically, of a material having a refractive index that varies in response to an electric field applied thereto.

[0055] refer to Figure 1 The figure schematically illustrates a photonic circuit system 100 including at least one ring resonator element according to some embodiments of the present disclosure. The system 100 includes at least one photonic layer 50 and an electrode arrangement structure 110 positioned on the surface of the photonic layer 50. Figure 1 A top electrode arrangement 110 and a bottom electrode 120 are illustrated. In this non-limiting example, the top electrode arrangement includes electrodes 112, 114, 116, and 118. Generally, the bottom electrode 120 can be used as a common electrode, a conductive substrate, or it can be formed as an additional electrode arrangement having multiple electrode portions, which is a mirror image of the arrangement of the electrode arrangement 110 placed on the top surface of the photonic layer 50. When used as a common bottom electrode or a conductive substrate, the bottom electrode 120 can be maintained at a ground potential. It should be understood, and as described in more detail below, that the electrode arrangement can vary according to the desired layout of the photonic circuit. Furthermore, as described below, the electrode arrangement can support a variety of possible photonic circuit layouts depending on the operation of the electrodes.

[0056] exist Figure 1 In this design, top electrodes 112, 114, and 116 are illustrated as elongated electrodes, typically defining waveguides 52a, 52b, and 54. Additionally, top electrode 118 is a circular electrode. Therefore, when a voltage is maintained between the first top electrode 118 and the bottom electrode 120, the electric field between the top and bottom electrodes defines a circular waveguide within at least one photonic layer 50. Such a circular waveguide functions as an optical ring resonator.

[0057] The electrodes of the electrode arrangement 110 can be operatively connected to a control unit 500, which is configured to selectively apply a voltage to selected electrodes at selected times and voltage values ​​based on the desired waveguide arrangement of the photonic circuit 100 and operation. The control unit 500 may include one or more processor and memory circuits (PMCs) and input / output interfaces. Additionally, the control unit 500 may include electronic circuitry configured to apply a selected voltage to selected electrodes of the electrode arrangement 110, specifically to the top electrode 118. Generally, one or more PMCs of the control unit can operate based on selected inputs and / or pre-stored data to operate the electronic circuitry for applying the selected voltage to selected electrodes of the electrode arrangement 110, thereby forming and operating the selected photonic circuitry within at least one photonic layer 50.

[0058] During operation, the control unit 500 can utilize its electronic circuitry to generate a selected voltage difference between selected electrodes, thereby applying a selected electric field to a region of the photonic layer 50. For example, the voltage difference between electrodes 118 and 120 generates an electric field in the region between the electrodes forming the waveguides of the ring resonator. Changing the magnitude of the voltage alters the resonant conditions of the resonator. Furthermore, applying a voltage difference between electrodes 112, 114, and / or 116 and electrode 120 generates waveguides 52a, 52b, and 54 in the region between the electrodes. Waveguide 52b can be used to couple optical signals into and / or out of the ring resonator, or as a coupling gate for coupling signals from waveguide 54 into the ring resonator. Additionally, the waveguide can be operated to apply a phase shift to light passing through it. For example, waveguide region 54 can be used to promote optical coupling between two waveguides 52a and 52b by increasing the refractive index in the region between the waveguides, thereby increasing the coupling between waveguides 52a and 52b.

[0059] Generally, waveguide sections and / or ring resonators can be formed by two or more electrodes that together form the spatial structure of the waveguide / resonator and are maintained at approximately similar or identical voltages. These two or more electrodes can be separated from each other while forming a common waveguide. The spacing between the electrodes is chosen to maintain electrical insulation between them, where the distance is typically less than the distance between the electrodes and the mode supported by the respective waveguide to maintain a continuous waveguide, or less than the wavelength of the light radiation used within the waveguide.

[0060] Although waveguides 52a, 52b, 54 and / or the ring resonator formed by electrode 118 are formed within photonic layer 50, i.e., in the region where the refractive index varies based on the electric field, the mode of light passing through the waveguides can extend beyond photonic layer 50. To prevent the electrodes of electrode arrangement 110 from absorbing light, the electrodes can be formed of a material selected to suppress absorption. For example, the electrodes can be formed of a crystalline material whose absorption peak is far from the wavelength of light propagating in the waveguide. In some other embodiments, the electrodes can be formed of a transparent conductive material (such as indium tin oxide (ITO)) or of a thin metal layer (e.g., with a thickness in the tens of nanometers range), thereby making the electrodes effectively transparent. Generally, it should be understood that the electrodes of electrode arrangements 110 and 120 are configured to maintain voltage and do not need to carry current except for accumulating the required voltage. Therefore, the electrodes can be conductive (e.g., metallic electrodes) or have a limited conductivity, such as the conductivity provided in ITO electrodes or other non-metallic electrodes. Furthermore, graphite and / or graphene electrodes can also be used.

[0061] In some other implementations, for example, such as Figure 2 As shown, the photonic circuit system can utilize a cladding 60 located on both sides of the photonic layer 50, situated between the photonic layer 50 and electrodes 110 and 120. The cladding 60 isolates the electrodes from the optical modes of the waveguide within the photonic layer 50. This configuration allows for the use of electrodes of various types and materials. This is partly due to the fact that the use of the cladding 60 creates a distance between the electrodes of the electrode arrangement 110 and the photonic layer 50, resulting in reduced interaction / absorption between the optical modes of the waveguide and the electrodes. Additionally, the use of the cladding 60 allows the electric field at the photonic layer to act as a far-field, further eliminating abrupt field changes caused by the corners or edges of the electrodes. The use of the cladding 60 also provides for distancing the electrodes from the optical modes supported by the waveguide, allowing various combinations of two or more electrodes to operate together, forming a common waveguide. This enables the electrode arrangement to include dot-like or pixel-like electrodes (e.g., as shown below). Figure 11 As illustrated in the example (arranged as pixels in a CCD), these dot-shaped or pixel electrodes can operate together to produce various spatial formations of photonic circuits, as described in more detail below.

[0062] As indicated above, at least one photonic layer 50 is formed of a material having selective electro-optic properties. More specifically, the photonic layer 50 may be formed of a material having a selective and sufficiently high Pockel coefficient, which is equal to the second-order polarizability χ. (2) The Pockel coefficient indicates the level of the Pockel effect, or DC Kernel effect, in a material, where an electric field applied to the material causes a change in the material's refractive index.

[0063] Generally speaking, the Pockel effect is an electro-optic effect in which the refractive index of an optical medium can be changed by applying an electric field to the medium. The Pockel effect is typically a linear electro-optic effect, where the change in refractive index (Δn) is proportional to the intensity of the electric field (E) applied to the medium. This effect usually occurs in crystals lacking inversion symmetry, such as the materials listed above. Although the Pockel coefficient measured for most known materials is very small, various materials such as barium titanate (BaTiO3 or BTO) exhibit a relatively large Pockel effect, characterized by r 42 The stress-free Pockel coefficient is approximately 1300 ± 100 pm / V. Ongoing research is underway to develop additional materials with an increased Pockel effect. Generally, the techniques disclosed herein can utilize materials with significantly large Pockel coefficients. For example, the material of a photonic layer can be characterized by a Pockel coefficient of 100 pm / V or higher. In some examples, the Pockel coefficient of the material can be 200 pm / V or higher, or 300 pm / V or higher, or 400 pm / V or higher, or 500 pm / V or higher, or 600 pm / V or higher, or 700 pm / V or higher, or 800 pm / V or higher, or 900 pm / V or higher, or 1000 pm / V or higher.

[0064] The Pockel effect originates from the behavior of polarization, which can be expressed as a power series of the electric field E in nonlinear media. Higher-order terms are the reason why the dielectric constant (also related to the refractive index) varies with the external electric field applied to the material. Specifically, the quadratic term χ... (2) i,j,k E j E k This causes the Pockel effect. The Pockel coefficients depend on the orientation. They are typically different for the three principal axes of the crystal lattice structure of the medium. Figure 3 The Pockel coefficients of several selected materials are shown. As illustrated, some materials, such as gallium arsenide (GaAs) and silicon (Si), exhibit minimal response to an electric field. Other materials, such as lithium niobate (LiNbO3), lead zirconate titanate (PZT), and various organic compounds, exhibit enhanced electro-optic properties. The current known "champion" in the art is barium titanate (BTO), which has a stress-free Pockel coefficient of approximately 1300 pm / V. It should be noted that the techniques disclosed herein are not limited to the use of specific materials and generally involve the use of the Pockel effect and materials with significantly large Pockel coefficients. Such materials, including, for example, BTO and lithium niobate, can be used in at least one photonic layer of the photonic circuit system described herein.

[0065] Typically, in order to maintain light trapping within a ring resonator without a physical (etched) waveguide, the refractive index difference between the resonator waveguide and the surrounding environment should be high enough to overcome output coupling (tunneling) associated with waveguide bending. The stress-free Pockel factor of lithium niobate or BTO can support ring resonators with larger radii to reduce bending losses.

[0066] Figure 4A and Figure 4B The dimensions of the optical mode (wavelength 1000 nm) calculated by COMSOL are illustrated, and this optical mode is applied to the BTO photonic layer under the electric field generated by electrodes 110 and 120. Figure 4A ) and lithium niobate photonic layer ( Figure 4B It is formed in the straight waveguide generated in the process. Figure 4A An example is shown: a BTO photonic layer with a thickness of 1000 nm. Figure 4B Examples of lithium niobate photonic layers of equal thickness are illustrated. The photonic layer is formed from a continuous layer of BTO or LN placed on a cladding layer formed of SiO2, and then placed in an air environment. For example, BTO has a refractive index of n=2.4517 at a wavelength of 550 nm, and SiO2 has a refractive index of n=1.46 at a wavelength of 550 nm, or n=1.4585 at a wavelength of 1550 nm. Lithium niobate has a refractive index of n=2.3149 at a wavelength of 550 nm and a refractive index of n=2.2128 at a wavelength of 1550 nm. In these simulated examples, electrodes 110 and 120 maintain a voltage difference of 1V between them, thereby generating 10 in the direction between the electrodes. 6 An electric field of V / m. Due to the electric field, the refractive index in the BTO region between the electrodes changes according to the wavelength r for 1550 nm. 42 The Pockel coefficient change Δn = 0.005 is 1300 ± 100 pm / V. The refractive index of the BTO layer on the sides of the region associated with electrodes 110 and 120 remains unchanged and is therefore lower than the refractive index between the electrodes. The LN photonic layer has a low Pockel coefficient, resulting in a refractive index change Δn = 0.00017, and as... Figure 4B As can be seen, the optical mode is significantly larger. Data on the optical and electro-optical properties are well known and can be found, for example, in A. Karvounis et al., Barium Titanate Nanostructures and Thin Films for Photonics. Adv. Optical Mater. Found in 2020, 8, 2001249. (For example...) Figure 4A and Figure 4B As illustrated, in order to support optical modes, waveguides can be formed with a width of 10,000 nm (or 10 micrometers).

[0067] These results indicate the use of 10 6 The ability of an applied voltage within the V / m electric field limit to maintain waveguides and stable modes in lithium niobate and BTO, thereby preventing spontaneous discharge (typically limited to 10 V / m). 7 (V / m). Furthermore, flexible photonic circuits can be provided for a variety of applications using a photonic layer with a thickness of 1 μm and electrodes using a 10 μm wide waveguide.

[0068] Now for reference Figure 5 This figure illustrates a cross-sectional view of a portion of a photonic circuit system 100 according to some embodiments of the present disclosure. As shown, the photonic circuit system 100 includes at least one photonic layer 50 formed of a material having selected electro-optic properties. The photonic layer 50 may be sandwiched between layers 60. Additionally, the photonic circuit system 100 includes a top electrode arrangement 110 and a bottom electrode 120. In this example, the top electrode arrangement includes an electrode 112 and a ring electrode 118, and the bottom electrode 120 includes two separate electrode regions, one aligned with a portion of the electrode 112 and the ring electrode 118, and the other aligned with another portion of the ring electrode 118. Generally, the bottom electrode 120 may be grounded, while a voltage may be applied to a selected top electrode 110.

[0069] Cladding 60 is formed of a selected material with a refractive index lower than that of photonic layer 50. When a voltage is applied between selected electrodes, such as electrodes 112 and 120, the electric field between the electrodes changes the refractive index of photonic layer 50 and generates one or more waveguides, such as waveguide 52 and waveguide ring resonator 58. More specifically, given that photonic layer 50 is aligned such that the electric field affects the inherent axis of photonic layer 50, the refractive index in the region between the electrodes increases and reaches a value n1, which is greater than the refractive index n2 in the region outside the electrodes and the refractive index n3 of cladding 60, i.e., n1>n2>n3. This change in refractive index in the region between the electrodes generates waveguide 52 and ring waveguide 58 in this region. Generally speaking, in Figure 5 In the example, light can be coupled from waveguide 52 into ring waveguide 58 depending on the distance between them and the length of the coupling region. In some embodiments, the photonic circuit can utilize a gate waveguide, typically formed by one or more additional electrodes. The gate waveguide enables controlled coupling of optical signals into and out of ring waveguide 58.

[0070] Generally speaking, due to the anisotropy of the Pockels effect, the refractive index variation of photon layer 50 depends on its orientation relative to the electrodes. More specifically, in some materials, when the refractive index n of the ordinary axis... o As the electric field increases, the refractive index n along the unusual axis... eAs the electric field decreases, it should be understood that the photonic circuit system described herein can be operated by oriented fields along any of these axes. For orientations along unusual axes, waveguides are formed outside the electrode regions.

[0071] Furthermore, some organic and polymeric materials exhibit the Pockel effect. According to some embodiments of this disclosure, such materials can be advantageously used to provide photonic layers. For example, it may be easier to fabricate at least one photonic layer 50 using organic or polymeric materials than using crystalline materials.

[0072] Generally, as described above, this disclosure provides a photonic circuit system including one or more artificial ring resonator elements. Alternatively, this disclosure provides an artificial ring resonator element for use with a photonic circuit. According to this disclosure, a ring resonator waveguide and optionally one or more additional waveguides of the photonic circuit are formed based on an electric field applied to at least one photonic layer using an electrode arrangement. Using an electric field to influence the refractive index of the photonic layer simplifies the photonic circuit and provides various photonic elements that influence the transmission of optical signals through the photonic circuit.

[0073] For example, Figure 6 An example of a photonic circuit includes electrode arrangements 110 and 120. The electrode arrangements include a top electrode 110 and a bottom electrode 120. The bottom electrode 120 may be formed as an electrode arrangement or a single common electrode maintained at a selected (e.g., ground) potential. The top electrode arrangement 110 includes a ring electrode 118, a coupling gate electrode 116, and a waveguide electrode 112. When operated at a selected voltage, the electrodes generate waveguide segments in the photonic layer region beneath the electrodes.

[0074] Generally, light propagating through the waveguide generated by electrode 112 can be coupled into the ring resonator (generated by electrode 118) by changing the refractive index below electrode 116, thereby creating a coupling gate. This allows for controlled coupling of light into and out of the ring resonator.

[0075] Figure 7A and Figure 7B Two configurations of the photonic circuit section 250 are illustrated, both of which include at least a ring resonator waveguide 254 coupled to the input / output waveguide 52. Figure 7A In the example, the ring resonator 254 is directly coupled to the input / output waveguide 52, and... Figure 7B In the example, coupling gate 252 is used to control the coupling between waveguide 52 and ring resonator 254. Although Figure 7A The configuration in the middle can also act as a passive delay line, but Figure 7BThe configuration in the image can serve as an active delay line. More advanced passive delay lines can be made from helical waveguides that achieve very long paths. Such helical waveguides can be formed using corresponding helical electrode arrangements that apply a corresponding electric field to the photonic layer.

[0076] Figure 8 An example is illustrated by a photonic circuit section 250 comprising two ring resonators 254a and 254b coupled to an input / output waveguide section 52. This configuration can be used to provide a selective reflection element in which the signal is filtered and the element reflects only the portion of the signal selected according to the resonant frequencies (wavelengths) of the ring resonators 254a and 254b. Figure 9A and Figure 9B An example of a photonic circuit section 250 configured to selectively transmit a portion of a signal between waveguides 52 and 54 is illustrated. The transmission element includes a ring resonator 254 placed between and coupled to both waveguides 52 and 54, such that an optical input signal in one waveguide can be transmitted through the other. A selected (filtered) portion of the input signal is coupled to the resonator 254 and from there to the other waveguide. Figure 9A This illustrates the propagation between parallel waveguides. Figure 9B The propagation between intersecting waveguides is illustrated. Figure 10 An example is shown of a photonic circuit portion including a first waveguide 52 coupled to a first ring resonator 254a. The first ring resonator 254a is coupled to a second ring resonator 254b, which in turn is coupled to a second waveguide 54.

[0077] Various configurations of ring resonator circuits, including one or more ring resonators and corresponding to one or more waveguides as illustrated herein, can provide a variety of photonic circuit components, such as transmission filters, reflector filters, switches, memory elements, delay lines, narrow laser linewidth formation, and micro-frequency combs.

[0078] like Figures 6 to 10As shown, one or more waveguide electrodes 118 can be operated to define a corresponding resonator waveguide within the photonic layer. The resonator can be defined by a circular electrode 118, which, when operated to maintain a selected voltage, defines a corresponding circular waveguide within the photonic layer. Although most circular resonators (so-called microrings, microdisks, or toroidal resonators) do not use a coupling control gate, as illustrated in the inventors' references listed above in relation to circular resonators, a coupling electrode 116 can be placed between the waveguide electrode 112 and the resonator electrode 118 to form a coupling gate 252. The voltage applied to the coupling electrode 116 can change the refractive index with the space between the waveguide and the resonator defined by the circular electrode 118, thereby changing the coupling of light entering and leaving the resonator. Furthermore, coupling can be controlled by narrowing the waveguide 112 to make the evanescent field larger, thus increasing the coupling through the gap. For example, the waveguide 112 can be defined using an arrangement of several parallel electrodes or multiple point electrodes (e.g., Figure 11 (As illustrated in the illustration). In such configurations, the width of waveguide 52 can be controlled by selecting the number of electrodes 112 defining the waveguide. Additionally, the selection of the voltage applied to the resonator electrodes 118 can be used to determine and / or fine-tune the resonant frequency and its operating characteristics. In some configurations, an optical resonator 254, such as that formed by the resonator electrodes 118, can operate in a photonic circuit as a delay line, filter, reflector, switch, or other circuit element. In some configurations, the photonic circuit system may include one or more electrodes or groups of electrodes configured and positioned to define a bent or kinked waveguide portion when activated with a selected voltage to define a delay line (e.g., spiral) in the photonic circuit.

[0079] It should be noted that ring resonators typically require enhanced light-trapping conditions compared to straight waveguides. This is due to the bending of the resonator waveguide, which can lead to bending losses. Therefore, the greater the refractive index difference between the waveguide and its surroundings, the smaller the resonator radius can be. However, for relatively low refractive index differences, based on what is achievable within voltage constraints and using the Pockels coefficient of available materials, ring resonators may require relatively large radii to maintain light trapping.

[0080] Artificial resonators can also be made from the straight waveguide portion forming a Fabry-Perot resonator, with Bragg mirrors on each side, thereby creating the Bragg mirrors by modulating the electric field along the waveguide axis. In this type of resonator, the bending loss described above does not exist. This is discussed below. Figure 15A and Figure 15B Example in.

[0081] Generally, in some embodiments, the photonic circuit system of this disclosure can utilize selected photonic structures for a variety of applications. For example, one or more optical resonators can be used as delay lines, frequency filters, narrow-linewidth lasers, micro-frequency combs, quantum memories, and various other photonic applications. Additionally, typical waveguide structures can be operated with selected voltages, thereby altering their refractive index and thus affecting the optical path and phase accumulated by the optical signals transmitted in the photonic circuit. The high bandwidth variation of the voltage, and therefore the high bandwidth variation of the resonator's refractive index, makes it possible to effectively compensate for the acoustic and thermal noise prevalent in chip-level devices.

[0082] The electrode arrangement 110 used in the different photonic circuit configurations described above may include various electrodes. During operation, selected electrodes can be activated using selected voltages to define corresponding waveguides, couplings between waveguides, phase-influencing elements, and other optical elements required for the operation of the selected photonic circuit. Furthermore, the elements of the photonic circuit can be dynamically changed by altering the voltage on the corresponding electrodes. This can be used to dynamically change the coupling between waveguides, phase changes along selected waveguides or through selected phase elements, the operation of selected resonators, reduce and / or compensate for noise or other fluctuations, etc. Therefore, the photonic circuit system of this disclosure provides flexibility in circuit design and operation and provides a basis for dynamically changing photonic circuits.

[0083] According to some embodiments of this disclosure, the photonic circuit system 100 can be configured to provide increased flexibility in supported photonic circuits. Figure 11 A photonic circuit system 100 according to some embodiments of the present disclosure is illustrated. Figure 11 The illustrated photonic circuit system 100 includes an electrode arrangement structure 110 located on one surface of at least one photonic layer 50, wherein one or more additional electrodes are located on the other surface of at least one photonic layer 50 and Figure 11Not specifically shown. The electrode arrangement 110 is formed by a two-dimensional array of a plurality of electrodes 112. The electrodes 112 preferably have a size not exceeding the wavelength of the light used in the photonic circuit 100 (so as not to cause reflections due to changes in refractive index). This size of the electrodes 112 allows groups of two or more electrodes to operate together to form a common waveguide, or a common region within the photonic layer 50 with an effective refractive index. More specifically, the operation of two or more electrodes at a selected voltage V provides an electric field applied to the photonic layer 50 by the two or more electrodes 112. In order to provide an effectively smooth electric field within the photonic layer, the spacing between the electrodes 112 is preferably chosen to be much smaller than the wavelength of the light used, and preferably on the order of tens of nanometers or less. Thus, the different electrodes 112 of the electrode arrangement 110 are preferably configured with a lateral (x-axis or y-axis) dimension smaller than the wavelength of the light used in the photonic circuit. This configuration of the electrodes enables increased flexibility (similar to an FPGA) in photonic circuit structures that can be formed from the electrode arrangement 110, allowing the operation of one or more selected electrode groups to be combined within the photonic layer 50 to form straight or curved (e.g., toroidal or spiral) artificial waveguide arrangements and / or a wide variety of optical elements with selected or varying widths and refractive indices. For example, in the case of a photonic circuit configured for use in infrared illumination at a wavelength of 1550 nm, the width and / or length of the electrode 112 can range from 10 nm to 100 nm.

[0084] As indicated above, bending loss is one of the loss sources in photonic circuits. Specifically, bending loss can limit the ability to retain optical signals within a ring resonator and limit the possible radius of such ring resonators.

[0085] The inventors have performed analytical calculations and numerical analyses on this ring resonator using available materials and those expected to be available soon, with moderate improvements in the Pockel coefficient and transparency compared to existing materials.

[0086] Figure 12 and Figure 13 Analytical calculations and numerical analysis data of the Q factor and fineness of a ring resonator formed according to some embodiments of the present disclosure are shown, wherein the photonic layer is formed of BTO or LiNbO3.

[0087] Figure 12 The fineness of analytical calculations according to some embodiments of this disclosure is shown, indicating the number of disk turns caused by the circular electrode. The electrode operates on a photonic layer of LiNbO3 or BTO, providing 10 turns on a 1 μm thick photonic layer. 7An electric field of V / m. The refractive index variation for LiNbO3 is δn = 0.0016 (dashed curve), and for BTO it is δn = 0.06. In practice, the fineness is limited to an absorption of 1 dB / cm, and for BTO, the fineness reaches its maximum F ≈ 27 at a ring radius of approximately 0.3 mm. For LiNbO3, the absorption is taken as 0.28 dB / m, and the fineness is limited to approximately F ≈ 40 at a ring radius of approximately 57 mm. The term "approximately" refers to the standard error in the numerical calculations, including a maximum variation of 20%.

[0088] in addition, Figure 13 The analytical calculations and numerical analyses of the quality factor and corresponding mode lifetime for a microdisk mode as a function of disk radius R and refractive index variation δn = 0.06 for BTO are presented. Solid curves and markings relate to the calculation of bending losses, which are typically ignored, and horizontal dashed lines represent the absorption limits set by BTO (BaTiO3), SiN, and SiO2, respectively. For BTO, the absorption limit is set at 1 dB / cm; for SiN, it is set at 0.13 dB / cm; and for SiO2, it is set at 0.1 dB / km.

[0089] Analytical calculations are based on quantum tunneling (QT) and numerical simulations of the 1D Bessel function using COMSOL. The data demonstrate that stable resonator modes are possible using the δn of the BTO photonic layer for R ≥ 40 μm. For these calculations, the disk thickness was taken as 1 μm and the electric field as 10. 7 V / m. The dashed line represents the Q value corresponding to a precision of 100 for providing a 100-turn signal within the resonator. It is clear from this graph that even with the existing Pockel coefficient of BTO, small resonators of a few hundred micrometers in size can achieve up to Q=10 if greater transparency is achieved. 10 The Q factor.

[0090] Therefore, while BTO and LiNbO3 may offer limited functionality, the techniques disclosed herein can be efficiently implemented using existing known materials. As indicated above, efforts are underway worldwide to find new materials with higher Pockel coefficients and / or lower absorption, and it is hoped that these materials will be found in the near future according to new existing materials roadmaps.

[0091] Figure 14The intended quality factor of a ring resonator formed using the techniques of this disclosure is illustrated for different ring radii between 10 μm and 100 μm, and for different refractive index variations δn expected to be available soon. As shown, for larger refractive index variations, the ring resonator provides a larger Q factor for smaller ring radii. For example, for low absorption, a refractive index variation δn of 0.3 (only 6 times the refractive index variation of BTO) has already enabled a ring with a radius of 40 μm to achieve Q=10. 12 .

[0092] In summary, the technology disclosed herein enables ring resonators to achieve a fineness of 30 using BTO and 40 using a LiNbO3 photonic layer. Various material improvements, such as reducing BTO absorption to the level of quartz crystals (e.g., 1.7 dB / km), will provide 10 at a radius R = 400 μm. 6 The precision (with existing BTO Pockel coefficients). For a ring resonator with radius R = 40 μm, using a material with a refractive index change of 0.3 will provide 10 6 The level of precision.

[0093] Furthermore, as indicated above, the optical (artificial) resonator can also be constructed from a straight waveguide section having a rear reflector and a front reflector (e.g., Bragg mirrors on each side). This configuration can form a Fabry-Perot resonator, whereby, according to this disclosure, the front and rear reflectors (Bragg mirrors) are fabricated by modulating an electric field along the waveguide axis at two selected regions along the waveguide section. In this case, the problem of bending loss is eliminated, and the optical resonator can be formed to the desired size using available materials such as lithium niobate. Linear optical resonators according to some embodiments of this disclosure offer various advantages over conventional photonic linear resonators, including, for example: 1. Edge roughness again becomes a limiting factor, which, as explained above, is eliminated or at least significantly reduced by using an electric field applied to the photonic layer; 2. The use of an electric field to generate and / or modulate the mirrors makes it possible to selectively change the reflectivity of the mirrors by varying the voltage applied to the respective electrodes, thereby controlling when light leaves the cavity. 3. By changing the waveguide refractive index within the waveguide portion defining the cavity of the resonator through altering the electric field applied by the corresponding electrodes, the effective length of the cavity can be changed, thereby enabling a high-bandwidth modification of the resonant wavelength (e.g., to suppress acoustic and thermal noise). Therefore, refer to... Figure 15A and Figure 15B Examples of direct (e.g., Fabry-Perot) resonators according to some embodiments of this disclosure are shown. Figure 15A The layered structure of the direct resonator, exemplified by electrode arrangement structure 110 and electrode arrangement structure 120, is shown. Figure 15BA top view illustrating an effective waveguide region is shown, which includes areas that produce the selected refractive index variation for the resonator structure.

[0094] exist Figure 15A In the example, the region of the photonic layer is used to define a waveguide using electrode arrangements 110 (top) and 120 (bottom). Electrode 116 extends beyond the page region defining the waveguide, electrode 114 defines the front and rear reflection regions or interfaces of the resonator, and electrode 112 defines the resonator cavity. Figure 15B A top view of a similar structure is illustrated, wherein waveguide 52 is defined by electrode 116, resonator interfaces 256 and 258 are defined by electrode 114, and resonator cavity 250 is defined by electrode 112. Straight / linear resonators can provide a variety of characteristics within photonic circuits while eliminating problems associated with bending losses. Such a straight resonator 350 can be formed from any available material, such as lithium niobate, with sufficient Pockels coefficient and finite absorption.

[0095] Generally, electrode 114 can be formed by multiple electrodes that create structured interfaces such as dichroic reflectors or Bragg reflectors. This can be used to control the reflection / transmission properties of interfaces 256 and 258, thereby providing control over the Q factor, resonant wavelength, etc. of resonator 350.

[0096] Generally, pixel-like electrode arrangements can be operated together to form ring resonator waveguides or straight waveguide resonators within photonic circuits. This allows for increased flexibility in circuit configuration and enables the operation of photonic circuits based on digital diagrams of the circuit layout.

[0097] Therefore, this disclosure provides a photonic circuit system utilizing at least one photonic layer and at least one electrode arrangement positioned to apply an electric field over selected regions of the photonic layer. The use of the electric field applied by the selected electrodes of the electrode arrangement defines selected arrangements of one or more waveguides, wherein the intensity of the electric field is used to determine the refractive index variation in the corresponding regions of the photonic layer. In some embodiments, the selected arrangements of one or more waveguides are formed without etching or structural manipulation of the photonic layer.

[0098] As indicated above, photonic circuits and photonic resonators according to various embodiments of this disclosure can provide a wide range of applications, including, for example, elements of photonic circuits, delay lines, filters, etc. Furthermore, such resonators, and particularly ring resonators, can provide a reference standard for frequency locking of other devices (such as lasers), operate as sensors or detectors for single or minute particles, or operate as quantum devices (e.g., frequency combs) or entanglers of photons and / or atoms.

[0099] In this regard, atomic clocks currently providing the best frequency standards utilize short-term and long-term stability control modules. Long-term stability is provided by atoms, while short-term stability is provided by high-precision optical cavities. Currently, such cavities are very large and bulky. Using high-precision, high-stability photonic resonators fabricated in chip-level devices according to the above-described technology, the current large cavities can be replaced in frequency standards, thereby providing enhanced short-term stability control.

[0100] Furthermore, as described in the provided references by Rosenblit et al., ring resonators can be used to form detectors (sensors) for trace materials down to a single atom. Therefore, creating high-quality chip-scale ring resonators will enable high-performance chip-scale sensors for trace materials (e.g., contaminants).

[0101] Furthermore, frequency combs are currently a crucial component of any optical atomic clock. However, they are currently bulky and cumbersome. Generally, frequency combs can be formed by nonlinear phenomena within waveguides. However, this requires high light intensity. High-precision resonators precisely generate these high intensities as they accumulate light entering the cavity (resonator), enabling such photonic resonators according to some embodiments of this disclosure to form miniature frequency combs. This nonlinear effect occurs even in materials with relatively weak nonlinear properties, such as those currently implemented using SiO or SiN, under high light intensity.

[0102] It should be noted that the various features described in the various implementation schemes can be combined according to all possible combinations of technologies.

[0103] It should be understood that the invention is not limited in its application to the details set forth in the specification or shown in the drawings contained herein. The invention is capable of other embodiments and can be practiced and performed in various ways. Therefore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be construed as limiting. Consequently, those skilled in the art will recognize that the concepts upon which this disclosure is based can readily be used as the basis for designing other structures, methods, and systems for achieving several of the objectives of the subject matter currently disclosed.

[0104] Those skilled in the art will readily understand that various modifications and alterations can be applied to embodiments of the invention as described above without departing from the scope of the invention as defined by the appended claims.

Claims

1. A photonic circuit, the photonic circuit comprising at least one resonator element, the at least one resonator element comprising: At least one photonic layer formed of a material having selective electro-optic properties; An electrode arrangement structure, the electrode arrangement structure including at least a first top electrode arrangement structure and a second bottom electrode arrangement structure positioned at opposite first and second surfaces of the at least one photonic layer; At least one of the first top electrode arrangement and the second bottom electrode arrangement includes an electrode arrangement that defines a ring structure, and wherein, in response to a potential applied to one or more electrodes of the electrode arrangement, the refractive index varies in a corresponding region of the at least one photonic layer affected by the one or more electrodes, thereby selectively defining a ring waveguide within the at least one photonic layer.

2. The photonic circuit of claim 1, wherein at least one of the first top electrode arrangement and the second bottom electrode arrangement comprises a circular electrode defining a ring resonator waveguide.

3. The photonic circuit according to claim 1 or 2, the photonic circuit further comprising a first cladding layer and a second cladding layer located at a first surface and a second surface of the at least one photonic layer, the first cladding layer being located between the at least one photonic layer and the first top electrode arrangement structure, and the second cladding layer being located between the at least one photonic layer and the second bottom electrode arrangement structure.

4. The photonic circuit according to any one of claims 1 to 3, wherein at least one of the first top electrode arrangement and the second bottom electrode arrangement comprises a plurality of independently controlled point electrodes positioned on at least one surface of the at least one photonic layer, and wherein applying a voltage to a set of point electrodes along a selected region defines the photonic circuit in which light propagates within a corresponding region of the at least one photonic layer.

5. The photonic circuit according to any one of claims 1 to 4, wherein the selected electro-optic property includes the Pockel coefficient, the Pockel coefficient defining the refractive index change in response to a DC electric field.

6. The photonic circuit of claim 5, wherein the at least one photonic layer comprises a material having at least one Pockel coefficient of 100 pm / V or higher.

7. The photonic circuit according to any one of claims 1 to 6, wherein the at least one photonic layer is formed of lithium niobate or BTO (BaTiO3).

8. The photonic circuit according to any one of claims 1 to 7, the photonic circuit further comprising a control unit, the control unit including at least one processor and memory circuit, the control unit being electrically connected to the electrodes of the first top electrode arrangement and the electrodes of the second bottom electrode arrangement, and configured to selectively apply a voltage to the electrodes to operate the at least one resonator element.

9. The photonic circuit of claim 8, wherein the control unit is further configured to selectively apply a voltage to the electrodes to determine one or more resonant wavelengths of the at least one resonator element.

10. The photonic circuit according to any one of claims 1 to 9, wherein the electrode arrangement structure comprises electrodes formed of a transparent conductive material.

11. The photonic circuit according to any one of claims 1 to 10, wherein the electrode arrangement comprises a metal electrode, wherein the metal electrode is thin enough to eliminate the absorption of light by the metal electrode.

12. The photonic circuit according to any one of claims 1 to 11, wherein the electrode arrangement structure comprises crystal electrodes characterized by narrow absorption peaks.

13. The photonic circuit according to any one of claims 1 to 12, the photonic circuit further comprising at least one top gate electrode located near the first top electrode arrangement defining the at least one resonator element, such that applying a voltage to the at least one top gate electrode provides a varying refractive index in the region of the photonic layer, thereby operating as a gate for coupling an optical signal to the at least one resonator element.

14. The photonic circuit according to any one of claims 1 to 13, wherein the at least one resonator element is operable as a filter.

15. The photonic circuit according to any one of claims 1 to 14, wherein the at least one resonator element is operable as a switch.

16. The photonic circuit according to any one of claims 1 to 15, wherein the at least one resonator element is operable as a reflector or a delay line.

17. The photonic circuit according to any one of claims 1 to 16, wherein the at least one resonator element is operable as a reference standard for frequency locking.

18. The photonic circuit according to any one of claims 1 to 17, wherein the at least one resonator element is operable as a sensor or detector for single or microparticles.

19. The photonic circuit according to any one of claims 1 to 18, wherein the at least one resonator element is operable as a quantum device, such as a frequency comb, or an entanglement of photons and / or atoms.

20. The photonic circuit according to any one of claims 1 to 19, the photonic circuit comprising at least a first ring resonator element and a second ring resonator element coupled therebetween, wherein each of the first resonator element and the second resonator element is defined by at least a first top electrode arrangement having a circular portion.

21. The photonic circuit according to any one of claims 1 to 20, the photonic circuit further comprising at least one additional electrode arrangement configured to define at least one linear waveguide configured to couple an optical signal into or out of the at least one resonator element.

22. The photonic circuit according to any one of claims 1 to 21, wherein a change in the potential applied to one or more electrodes of the electrode arrangement enables control over a change in the resonant wavelength of the at least one resonator element.

23. A photonic circuit, the photonic circuit comprising at least one resonator element, the at least one resonator element comprising: At least one photonic layer formed of a material having selective electro-optic properties; An electrode arrangement structure, the electrode arrangement structure including at least a first top electrode arrangement structure and a second bottom electrode arrangement structure positioned at opposite first and second surfaces of the at least one photonic layer; At least one of the first top electrode arrangement and the second bottom electrode arrangement includes an electrode arrangement that defines at least a first discontinuous region and a second discontinuous region in the electrode along an elongated region; and wherein, in response to a potential applied to one or more electrodes of the electrode arrangement, the refractive index in a corresponding region of the at least one photonic layer is affected by the one or more electrodes, thereby selectively defining at least a first refractive index interface and a second refractive index interface associated with the first discontinuous region and the second discontinuous region, thereby defining the resonator within the at least one photonic layer.

24. The photonic circuit of claim 23, wherein the resonator is defined by a straight waveguide electrode portion and two or more electrodes defining the at least first discontinuity region and the second discontinuity region and configured to change the refractive index at both ends of the straight waveguide electrode portion, thereby defining a straight waveguide portion forming a Fabry-Perot resonator with a Bragg mirror on each side.

25. The photonic circuit according to claim 23 or 24, the photonic circuit further comprising a first cladding layer and a second cladding layer located at a first surface and a second surface of the at least one photonic layer, the first cladding layer being located between the at least one photonic layer and the first top electrode arrangement, and the second cladding layer being located between the at least one photonic layer and the second bottom electrode arrangement.

26. The photonic circuit according to any one of claims 23 to 25, wherein at least one of the first top electrode arrangement and the second bottom electrode arrangement comprises a plurality of independently controlled point electrodes positioned on at least one surface of the at least one photonic layer, and wherein applying a voltage to a set of point electrodes along a selected region defines the photonic circuit in which light propagates within a corresponding region of the at least one photonic layer.

27. The photonic circuit according to any one of claims 23 to 26, wherein the selected electro-optic property includes a Pockel coefficient, the Pockel coefficient defining a change in refractive index in response to a DC electric field.

28. The photonic circuit according to any one of claims 23 to 27, wherein the at least one photonic layer is formed of lithium niobate or BTO (BaTiO3).

29. The photonic circuit according to any one of claims 23 to 28, the photonic circuit further comprising a control unit, the control unit including at least one processor and memory circuit, the control unit being electrically connected to the electrodes of the first top electrode arrangement and the electrodes of the second bottom electrode arrangement, and configured to selectively apply a voltage to the electrodes to operate the at least one resonator element.

30. The photonic circuit of claim 29, wherein the control unit is further configured to selectively apply a voltage to the electrodes to determine one or more resonant wavelengths of the at least one resonator element.

31. The photonic circuit according to any one of claims 23 to 30, wherein the electrode arrangement structure comprises electrodes formed of a non-absorbing conductive material.

32. The photonic circuit according to any one of claims 23 to 31, wherein the electrode arrangement comprises metal electrodes, wherein the metal electrodes are thin enough to eliminate the absorption of light by the metal electrodes.

33. The photonic circuit according to any one of claims 23 to 31, wherein the electrode arrangement structure comprises a crystal electrode characterized by a narrow absorption peak.

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