Hybrid organic electro-optic device for wide bandgap platforms

Abstract

A hybrid electro-optic modulator includes a waveguide including a wide-bandgap material, a first organic electro-optic (OEO) material disposed on a first sidewall of the waveguide, a second OEO material disposed on a second sidewall of the waveguide, a first electrode disposed at a first side of the waveguide, a second electrode disposed at a second side of the waveguide, a first spacer disposed between the OEO material and the first electrode, and a second spacer disposed between the second OEO material and the second electrode.

Description

HYBRID ORGANIC ELECTRO-OPTIC DEVICE FOR WIDE BANDGAPPLATFORMSCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 489,740, filed on March 10, 2023, entitled HYBRID ORGANIC MODULATORS FOR WIDE BANDGAP PLATFORMS, which is hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to electro-optic devices, and more specifically to electro-optic modulators useful for signal conversion and processing within wide bandgap platforms.BACKGROUND

[0003] Electro-optic devices modulate, manipulate, or control properties of light based on an interaction between electrical and optical signals. For example, electro-optic modulators modulate the intensity, phase, polarization, and / or frequency of an optical signal by varying an electric field applied to an electro-optic material. In particular, hybrid electro-optic modulators for wide bandgap platforms, which can achieve high modulation efficiency, delivers high bandwidth, and minimize optical loss (e.g., insertion loss), may be desirable.SUMMARY

[0004] In an embodiment, a hybrid electro-optic modulator includes a waveguide including a wide-bandgap material, a first organic electro-optic (OEO) material disposed on a first sidewall of the waveguide, a second OEO material disposed on a second sidewall of the waveguide, a first electrode disposed at a first side of the waveguide, a second electrode disposed at a second side of the waveguide, a first spacer disposed between the OEO material and the first electrode, and a second spacer disposed between the second OEO material and the second electrode.

[0005] In an embodiment, each of the first and second spacers includes a material having a dielectric constant not less than about 3.9, or a material having a refractive index not greater than about 2.5, or both.

[0006] In an embodiment, the waveguide comprises silicon nitride.

[0007] In an embodiment, the waveguide comprises gallium nitride.

[0008] In an embodiment, a width of each of the first and second spacers is not greater than about 15% of a spacing between the first and second electrodes.

[0009] In an embodiment, a width of each of the first and second OEO materials is in a range from about 20% to about 60% of the spacing between the first and second electrodes.

[0010] In an embodiment, the OEO material comprises polarizable chromophores, capable of undergoing a crosslinking reaction to form a thermoset plastic or polymer.

[0011] In an embodiment, modulation efficiency of the modulator has a value not greater than about 10 V-mm.

[0012] In an embodiment, a photonic integrated circuit includes the modulator, along with other passive and active components.

[0013] In an embodiment, a hybrid electro-optic modulator includes a first wide-bandgap waveguide, a second wide-bandgap waveguide, an organic electro-optic (OEO) material disposed between the first and second waveguides, a first electrode disposed at a first side of the OEO material, a first spacer disposed between the OEO material and the first electrode, and a second spacer disposed between the OEO material and the second electrode.

[0014] In an embodiment, a width of each of the first and second spacers is in a range from about 25% to about 35% of a spacing between the first and second electrodes.

[0015] In an embodiment, a width of each of the first and second waveguides is in a range from about 10% to about 20% of the spacing between the first and second electrodes.

[0016] In an embodiment, a hybrid electro-optic modulator includes a substrate including a silicon carrier wafer and a buried oxide layer, a silicon nitride waveguide, an oxide layer disposed over the waveguide to enclose the waveguide with the buried oxide layer, an OEO material spaced apart from the waveguide by an oxide spacer, the oxide spacer corresponding to a portion of the oxide layer between the OEO material and the waveguide, and first and second electrodes disposed at a first side and a second side of the OEO material, respectively, and vertically spaced apart from the waveguide by the oxide layer.

[0017] In an embodiment, the modulator further includes a first additional oxide spacer between the first electrode and the OEO material and a second additional oxide spacer between the second electrode and the OEO material.

[0018] In an embodiment, a hybrid plasmonic electro-optic modulator includes a substrate including gallium nitride (GaN), a waveguide core including an organic electro-optic (OEO) material, and first and second electrodes disposed at first and second sides of the waveguide core.

[0019] In an embodiment, the first and second electrodes are disposed on first and second sidewalls of the waveguide core, respectively, and each of the first and second electrodes includes gold (Au).

[0020] In an embodiment, hybrid electro-optic modulator includes a waveguide core including an organic electro-optic (OEO) material, first and second electrodes disposed at first and second sides of the waveguide core, a first waveguide rail including GaN and being disposed on a first sidewall of the waveguide core, a second waveguide rail including GaN and being disposed on a second sidewall of the waveguide core, a first transmission line including doped GaN and connecting the first electrode and the first waveguide rail, and a second transmission line including doped GaN and connecting the second electrode and the second waveguide rail.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 illustrates an electro-optic device according to an embodiment of the present disclosure.

[0022] FIG. 2 illustrates an electro-optic device according to an embodiment of the present disclosure.

[0023] FIG. 3 illustrates a plasmonic device according to an embodiment of the present disclosure.

[0024] FIG. 4 illustrates a non-plasmonic device according to an embodiment of the present disclosure.

[0025] FIG. 5 illustrates an electro-optic device according to an embodiment of the present disclosure.

[0026] FIG. 6 an electro-optic device according to an embodiment of the present disclosure.DETAILED DESCRIPTION

[0027] In the following description, certain illustrative embodiments have been illustrated and described. As those skilled in the art would realize, these embodiments may be modified in various different ways without departing from the scope of the present disclosure.Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals may designate like elements in the specification.

[0028] FIG. 1 shows an electro-optic device 100 according to an embodiment of the present disclosure. In the embodiment of FIG. 1 , the electro-optic device (e g., a silicon nitrideorganic hybrid device) 100 includes a substrate (e.g., SiCh substrate) 102, first and second electrodes 104A and 104B, a wide-bandgap material waveguide (e.g., silicon nitride or gallium nitride waveguide) 106, first and second organic electro-optic materials (e.g., JRD1 or HLD) 108A and 108B, first and second spacers 1 10A and HOB, and cladding (e.g. an upper cladding layer) 112. For example, "a wide-bandgap material” may refer to a material having a band gap greater than 3eV.

[0029] The wide-bandgap material waveguide 106 in FIG. 1 is disposed between the first and second organic electro-optic (OEO) materials 108A and 108B. In an embodiment, the waveguide 106 has first and second sidewalls (e.g., left and right sidewalls in FIG. 1) on which the first and second OEO materials 108A and 108B are disposed, respectively. For example, the first and second sidewalls of the waveguide 106 may contact the first and second OEO materials 108A and 108B, respectively.

[0030] The first spacer 110A in FIG. 1 is disposed between the first OEO material 108 A and the first electrode 104 A, and the second spacer 110B in FIG. 1 is disposed between the second OEO material 108B and the second electrode 104B. In an embodiment, the first spacer 110A and the second spacer HOB each have substantially the same length LSP in a specific direction (e.g.. a horizontal direction in FIG. 1). The length in the specific direction (e.g.. a width) LSP of each of the spacers 110A and HOB may be in a range not greater than about 15% (e.g., 14.5-15.4%) of a spacing LEL between the electrodes 104A and 104B. For example, the width LSP of each of the spacers 110A and 110B may be in a range from about 5% to about 15%. When the length LSP of each of the spacers 110A and 110B is shorter thanabout 5% of the spacing LEL between the electrodes 104A and 104B, the electrodes 104A and 10B may be excessively proximate to the OEO materials 108 A and 108B and the waveguide 106 to significantly increase an insertion loss of the device 100. Despite this, it may occasionally be desirable, for fabrication or performance reasons, to eliminate the spacers entirely (i.e. LSP = 0). When the length LSP of each of the spacers 110A and 110B is longer than about 15% of the spacing LEL between the electrodes 104A and 104B, a value (VnL, that is, the voltage XL needed to shift the phase of light by half a wavelength over an interaction length L) of the device 100 may be excessively increased, which indicates excessively low modulation efficiency of the device 100 to result in high operating voltages, large device size, and / or increased power consumption. For example, the length LSP of each of the spacers 110A and HOB may be about 500 nm when the spacing LEL between the electrodes 104A and 104B is about 5000 nm.

[0031] The first and second spacers 110A and 100B may include one or more materials selected to increase electric field intensity in the OEO materials 108 A and 108B while reducing capacitance of the device 100 to achieve sufficiently high bandwidths thereof. In an embodiment, the first and second spacers 110A and HOB may include a low refractive index material, or a high dielectric constant material, or both. Such a low refractive index material may be a material having a refractive index not greater than about 2.5 (e g. 2.45-2.54), and may include silicon nitride, silicon oxynitride, silicon dioxide, or the like. Such a high dielectric constant material may be a material having a dielectric constant not less than that (e.g., about 3.9) of conventional silicon dioxide, and may include hafnium dioxide (HfCh). zirconium dioxide (ZrCh), or the like. For example, the first and second 100A and HOB may include at least one of silicon nitride, silicon oxynitride, silicon dioxide, hafnium dioxide (HfCh), or zirconium dioxide (ZrCh).

[0032] The first and second OEO materials 108A and 108B in FIG. 1 may surround the waveguide 106 together with the upper cladding layer 112. The first and second OEO materials 108 A and 108B each have substantially the same length LOEO in the specific direction (e.g., the horizontal direction in FIG. 1). In an embodiment, the length in the specific direction (e.g., a width) LOEO of each of the OEO materials 108A and 108B may be in a range from about 20% to about 60% of the spacing LEL between the electrodes 104A and 104B. For example, the length LOEO of each of the OEO materials 108A and 108B may beabout 1500 nm when the spacing LEL between the electrodes 104A and 104B is about 5000 nm.

[0033] In an embodiment, the waveguide 106 in FIG. 1 may have a length in a specific direction (e.g., a width) Lwcin a range about 15% to about 25% the spacing LEL between the electrodes 104A and 104B. For example, the length Lwc of the waveguide 106 may be about 1000 nm when the spacing LEL between the electrodes 104A and 104B is about 5000 nm. In an embodiment, a thickness T of a device layer in FIG. 1 may be in a range from about 2% to about 15% of the spacing LEL between the electrodes 104A and 104B. For example, the thickness T of the device layer may be about 220 nm when the spacing LEL between the electrodes 104 A and 104B is about 5000 nm.

[0034] The upper cladding layer 112 in FIG. 1 may include a low-index material (e.g., silicon dioxide), or an OEO material. The first electrode 104A in FIG. 1 is disposed at a first side (e.g., a left side in FIG. 1) of the waveguide 106 and the second electrode 104B in FIG. 1 is disposed at a second side (e.g., a right side in FIG. 1) of the waveguide 106. Each of the first and second electrodes 104A and 104B may include a metal (e.g., copper).

[0035] One or more of the composition of the OEO materials 108 A and 108B, the spacing LEL between the electrodes 104A and 104B, the width Lwc and the thickness of the waveguide 106, the composition of the electrodes 104 A and 104B, the width LSP and composition of the spacers 110A and HOB, and the composition and thickness of the upper cladding layer 112 may vary according to embodiments. For example, modulation efficiency was estimated using finite different eigenmode (FDE) calculations in Ansys Lumerical, using a refractive index of 1.979 for the silicon nitride and 1.44 for the SiCh. Both SiO2 and OEO material were examined as cladding options, and four OEO materials were examined as follows: the JRD1 chromophore (JRD1) having refractive index of 1.848 and EO coefficient of 320 pm / V, 25% JRD1 (25% JRD1) by weight in polymethylmethacrylate (PMMA) having refractive index of 1.571 and EO coefficient of 100 pm / V, and two materials with EO coefficient of 150 pm / V and similar loss to 25% JRD1 in PMMA (i.e., one (LL-JRD1) with the same refractive index as JRD1 and the other (LL-LI) with a refractive index of 1.7). Electro-optic response of the material w as estimated in the DC limit by finite field perturbations of V=±10 volts, where An =- !4*n3*r33*(V / d); where V is the applied voltage and d is the electrode spacing. Given the relatively large electrode spacing, the perturbationto the material was assumed to be uniform. Response was calculated for the fundamental TE eigenmode of the system. The effective index of the unperturbed and perturbed modes are shown in Table 1. Modulation efficiency, assuming a balanced push-pull Mach-Zehnder modulator, is calculated as X / (4*|dN / dV)|), where X is the wavelength and N is the effective index of the mode. The length LSP of each of the spacers 110A and 110B is 500 nm, the length LOEO of each of the OEO materials 108A and 108B is 1500 nm, the length Lwc of the waveguide 106 is 1000 nm, and the spacing LEL between the electrodes 104 A and 104B is 5000 nm.

[0036] Table 1. Silicon nitride-organic hybrid modulator simulation results

[0037] Using these designs, modulation efficiencies of about 10 V-mm or lower can be achieved, superior to modulation efficiencies of conventional devices (e.g.. those based on film lithium niobate (TFLN) platforms of about 22 V-mm). If a constraint of 1 dB of optical loss per phase shifter is applied, the maximum phase shifter length can be estimated from the imaginary component of N, allowing estimation of the drive voltage. While a drive voltage of over 70V would be required with JRD1, only 0.47V would be required with JRD1 in PMMA due to the lower refractive index of the material.

[0038] FIG. 2 shows an electro-optic device 200 according to an embodiment of the present disclosure. In the embodiment of FIG. 2, the electro-optic device (e g., a silicon nitrideorganic hybrid device) 200 includes a substrate (e.g., SiCh substrate) 202, first and second electrodes 204A and 204B, an electro-optic material (e.g., OEO material) 206, first and second waveguides (e.g., silicon nitride or gallium nitride waveguide rails) 214A and 214B, first and second spacers 210A and 210B, and cladding (e.g. upper cladding layer) 212. Somedescriptions overlapping with those described above with reference to FIG. 1 may be omitted for the interest of brevity.

[0039] The OEO material 206 in FIG. 2 is disposed between the first and second waveguides 214A and 214B to form a slot waveguide structure. For example, the OEO material 206 may be disposed on a first sidewall of the first waveguide 214A and a second sidewall of the second waveguide 214B. In an embodiment, the OEO materials 206 may be an organic electro-optic material with an electro-optic coefficient ns greater than about 30 pm / V. For example, the OEO material 206 may include one or more of the above-described materials (e.g., the JRD1, 25% JRD1 in PMMA, LL-JRD1, and LL-LI) or HLD suitable for use as the OEO materials 108 A and 108B in the embodiment of FIG. 1.

[0040] The first spacer 210A in FIG. 2 is disposed between the first electrode 204A and the first waveguide 214A, and the second spacer 210B in FIG. 2 is disposed between the second electrode 204B and the second waveguide 214B. In some embodiments, the first and second spacers 210A and 210B in FIG. 2 each may have substantially the same length (e.g., a width) LSP in a specific direction (e.g., a horizontal direction in FIG. 2). For example, the length LSP of each of the spacers 210A and 210B may be in a range from about 25% to about 35% of a spacing LEL between the electrodes 204A and 204B. When the length LSP of each of the spacers 210A and 210B is shorter than about 25% of the spacing LEL between the electrodes 204 A and 204B, the electrodes 204 A and 204B may be excessively proximate to the waveguide 214A and 214B and the OEO material 206 to significantly increase an insertion loss of the device 200. When the length LSP of each of the spacers 210A and 210B is longer than about 35% of the spacing LEL between the electrodes 204A and 204B. a value (VnL) of the device 200 may be excessively reduce modulation efficiency of the device 200. For example, the length LSP of each of the spacers 210A and 210B may be about 1250 when the spacing LEL between the electrodes 204A and 204B is about 4000 nm.

[0041] In some embodiments, each of the first and second spacers 210A and 210B in FIG. 2 may include a thickness greater than that of the spacers 110A and 110B in FIG. 1, or a material having a refractive index lower than the spacers 110A and 110B in FIG. 1, or both, to more effectively confine the optical mode. For example, the first and second spacers 210A and 210B in FIG. 2 may include 50% oxygenated silicon oxynitride, with a refractive indexof about 1.7 at 1550 nm, when the first and second spacers 110A and HOB in FIG. 1 may include silicon nitride with a refractive index of about 2.0 at 1550 nm.

[0042] The first and second waveguides 214A and 214B in FIG. 2 may surround the OEO material 206 together with the upper cladding layer 212. The first and second waveguide rails 214A and 214B each have substantially the same length LWR in a specific direction (e.g., the horizontal direction in FIG. 2). In an embodiment, the length LWR (e.g., a width) of each of the first and second waveguides 214A and 214B may be in a range from about 10% to about 20% of the spacing LEL between the electrodes 204A and 204B. For example, the length LWR of each of the first and second waveguides 214A and 214B may be about 500 nm when the spacing LEL between the electrodes 204A and 204B is about 4000 nm.

[0043] In an embodiment, the OEO material 206 in FIG. 2 may have a length LOEO (e.g., a width) in a range about 10% to about 15% the spacing LEL between the electrodes 204A and 204B. For example, the length LOEO of each of the first and second waveguides 214A and 214B may be about 500 nm when the spacing LEL between the electrodes 204A and 204B is about 4000 nm. In an embodiment, a thickness T of a device layer in FIG. 2 may be in a range from about 2% to about 15% of the spacing LEL between the electrodes 204 A and 204B. For example, the thickness T of a device layer in FIG. 2 may be about 220 nm when the spacing LEL between the electrodes 204A and 204B is about 4000 nm.

[0044] Using the computational methodology as described above with reference to the examples of Table 1, the device 200 exhibited a fundamental TE mode with N = 1.50941 + 0.0001056106i and a VnL of 13.3 V-mm; with a loss of 37.2 dB / cm, the maximum phase shifter length for 1 dB loss in this embodiment is 270 microns, for a drive voltage of 49. 12 V. Accordingly, the device 200 according to the embodiment of FIG. 2 achieves high modulation efficiency while delivering high bandwidth and low insertion loss, compared to those of conventional devices.

[0045] Electro-optic devices (e.g., the devices 100 in FIG. 1 and 200 in FIG. 2) according to embodiments of the present disclosure differ from conventional electro-optic devices (e.g.. silicon nitride / OEO polymer modulators) in that they neither require mode conversion to a separate layer on a photonic integrated circuit nor require changing the composition of the silicon nitride waveguide itself (e.g. to silicon -rich silicon nitride). These electro-optic devices according to embodiments of the presentdisclosure may also exhibit superior modulation efficiencies compared to the conventional electro-optic devices.

[0046] Other embodiments of the present disclosure include electro-optic devices with a slot waveguide based on gallium nitride (GaN), a wide bandgap semiconductor suitable for use in high-frequency and radiation-resistant applications. Some of these embodiments will be described in more detail hereinafter with reference to FIGS. 3 and 4.

[0047] FIG. 3 illustrates a plasmonic device (e.g., a GaN plasmonic-organic hybrid (POH) modulator) 300 according to an embodiment of the present disclosure. The device 300 in FIG. 3 includes a substrate 302, first and second electrodes 304A and 304B, and an OEO material 320.

[0048] The substrate 302 in FIG. 3 may be a GaN substrate or an insulating substrate with a GaN device layer (or GaN on insulator GaNOI). For example, the insulating substrate with a GaN device layer includes GaN on sapphire (AI2O3). However, embodiments of the present disclosure are not limited thereto. For example, the substrate 302 may include other substrate material(s) such as silicon carbide (SiC).

[0049] The first and second electrodes 304A and 304B in FIG. 3 are disposed at first and second sides (e.g., left and right sides in FIG. 3), respectively, to define a slot (or a waveguide core) therebetween. For example, the first and second electrodes 304A and 304B are disposed on first and second sidewalls (e.g., left and right sidewalls in FIG. 3) of the waveguide core, respectively. In an embodiment, the waveguide core has a length (e.g., a width) Lsw in a specific direction (e.g., a horizontal direction in FIG. 3) in a range from about 20% to about 90% of a thickness TLE of each of the first and second electrodes 304A and 304B. For example, the width Lsw of the waveguide core may be from about 75 nm where the thickness TEL of the electrodes 304A and 304B is about 220 nm.

[0050] In some embodiments, the first and second electrodes 304A and 304B include gold (Au). Since gold is often an acceptable material in back end of line (BEOL) processing of GaN based integrated circuits whereas gold is typically disallowed in standard silicon CMOS and silicon photonics BEOL, use of GaN as the semiconductor platform may increase feasibility for deployment of the plasmonic device 300 according to these embodiments of the present disclosure.

[0051] The OEO material 320 in FIG. 3 includes one or more of the above-described materials for the OEO materials 108A and 108B in FIG. 1 and the OEO material 206 in FIG.2. When the JRD1 was used as the OEO material 320, based on the above-describe simulation approach except using a previously reported anisotropic-inhomogeneous model to represent the EO coefficient throughout the slot due to the small slot width and increased interfacial effects, the following simulation results are obtained as shown in Table 2:

[0052] Table 2. Gallium nitride plasmonic-organic hybrid (POH) modulator simulation results

[0053] The results of Table 2 indicate an improvement of the device 300 according to an embodiment of the present disclosure over conventional POH devices. Accordingly, a POH device according to an embodiment of the present disclosure may be manufactured on a GaN platform with high-speed electronics and using a gold-compatible BEOL process.

[0054] FIG. 4 illustrates a non-plasmonic device (e.g., a GaN non-plasmonic organic hybrid modulator) 400 according to an embodiment of the present disclosure. The device 400 in FIG. 4 includes a substrate 402, first and second electrodes 404A and 404B, first and second transmission lines 422A and 422B, first and second waveguide rails 424A and 424B, and an OEO waveguide core material 420.

[0055] The substrate 402 in FIG. 4 may be a GaN or GaNOI substrate. The first and second GaN waveguide rails 424A and 424B in FIG. 4 define a slot (or a waveguide core) therebetween. For example, the first GaN waveguide rail 424A is disposed on a first sidewall (e.g., a left sidewall in FIG. 4) of the OEO waveguide core, and the second GaN waveguide rail 424B is disposed on a second sidewall (e.g., a right sidewall in FIG. 4) of the OEO waveguide core. In an embodiment, the OEO waveguide core has a length (e.g., a width) Lsw in a specific direction (e.g., a horizontal direction in FIG. 4) in a range from about 40% to about 80% of a length (e.g., a width) LR of each of the first and second GaN waveguide rails 424A and 424B in the specific direction. For example, the width Lsw of the OEOwaveguide core may be from about 150 nm where the width LR of the rail 424A or 424B is about 240 nm.

[0056] The first transmission line 422A in FIG. 4 connects the first electrode 404A and the first rail 424A, and the second transmission lines 422B in FIG. 4 connects the second electrode 404B and the second rail 424B. Each of the first and second transmission lines 422A and 422B may be a highly doped GaN transmission line. In an embodiment, each of the first and second transmission lines 422A and 422B has a length (e.g., a width) LTL in a specific direction (e.g.. the horizontal direction in FIG. 4) in a range from about 25% to about 55% of the width LR of each of the first and second rails 424A and 424B. For example, the width LTL of the transmission line 422A or 422B may be about 70 nm where the width LR of each of the rails 424A and 424B is about 240 nm. In an embodiment, a thickness T of a device layer may be in a range from about 85% to 100% of the width LR of each of the first and second rails 424A and 424B. For example, the thickness T may be about 220 nm where the width LR of the rail 424A or 424B is about 240 nm.

[0057] The device 400 in FIG. 4 achieves simulated mode index of 1.687779+5.229197E-6 and modulation efficiency of 0.749 V-mm. Accordingly, an electro-optic device (e.g., the device 400 in FIG. 4) according to an embodiment of the present disclosure may demonstrate wide bandgap and high frequency electronics capabilities of the GaN platform by performing sub-volt and sub-dB loss electro-optic modulation on a GaN platform.

[0058] In the embodiments shown in FIGS. 1 and 2, drive electrodes (e.g., the electrodes 104 A and 104B in FIG. 1) for a device (e.g., the device 100 in FIG. 1) and one or more OEO materials (e g., the OEO materials 108A and 108B in FIG. 1) are substantially coplanar with a wide-band waveguide (e.g., the waveguide 106 in FIG. 1). However, embodiments of the present disclosure are not limited thereto. In some embodiments of the present disclosure, drive electrodes for an electro-optic device (e.g., modulator) and OEO material(s) are not coplanar with a wide-bandgap waveguide (e.g., silicon nitride, gallium nitride, or the like), and are instead vertically separated by a thin oxide spacer, as will be described below with reference to FIGS. 5 and 6. These embodiments can provide various beneficial aspects that include simplified processing by keeping the wide-bandgap waveguide (silicon nitride or similar material) physically separated from the OEO layer and facilitating use of higher refractive index OEO materials.

[0059] FIG. 5 shows an electro-optic device 500 according to an embodiment of the present disclosure. In the embodiment of FIG. 5, the electro-optic device (e.g., a silicon nitrideorganic hybrid modulator) 500 includes a carrier wafer (e.g., Si carrier wafer) 502, a buried oxide layer (e.g., a buried SiCh layer) 520, an oxide layer (e.g., an upper SiCh layer) 522, a wide-bandgap material waveguide (e.g., silicon nitride or gallium nitride waveguide) 506, first and second electrodes (e.g., metal electrodes) 504A and 504B, and an OEO material (e.g., JRD1 or HLD) 508. A structure including the silicon earner wafer 502 and the buried oxide layer 250 may be referred to as a substrate. In the embodiment of FIG. 5, the waveguide 506 is embedded within the upper oxide layer 522, such that the upper oxide layer 522 may be disposed over the waveguide 506 to enclose the waveguide 506 together with the buried oxide layer 520. A portion of the upper oxide layer 522 between the OEO material 508 and the waveguide 506 may be referred to as an oxide spacer (or vertical spacer). The OEO material 508 is vertically spaced apart from the waveguide 506 by the oxide spacer. A cavity is disposed over the waveguide 506 and spaced apart from the waveguide 506 by a spacer distance (e.g., vertical spacer distance) DSP. The cavity may be formed by etching an oxide layer to a depth corresponding to the vertical spacer distance DSP above the top of the waveguide 506, and the cavity may be filled with metal electrodes 504A and 504B. The electrodes 504A and 504B in FIG. 5 are disposed at a first side (e.g., left side in FIG. 5) and a second side (e.g., right side in FIG. 5) of the OEO material 508, and are vertically spaced apart from the waveguide 506 by the upper oxide layer 522.

[0060] FIG. 6 shows an electro-optic device 600 according to an embodiment of the present disclosure. The device 600 in FIG. 6 differs from the device 500 in FIG. 5 in that the device 600 in FIG. 6 further includes first and second horizontal spacers (e.g., additional oxide spacers) 624A and 624B. The first additional oxide spacer 624A is disposed between the first electrode 604Aand the OEO material 608. and the second additional oxide spacer 624B is disposed between the second electrode 604B and the OEO material 608. The metal electrodes 604A and 604B may be fabricated within a cavity in a subsequent fabrication step after forming the horizontal oxide spacers 624A and 624B, so that the electrodes 604A and 604B are optionally protected by the horizontal oxide spacers 624A and 624B similarly to other embodiments of the present disclosure. However, in some embodiments, the metal electrodes 604A and 604B may be fabricated within the cavity in a fabrication step before forming the horizontal oxide spacers 624 A and 624B. The vertical spacer distance DSP inFIGS. 5 and 6 may range from about 50 to about 200 nanometers. An electrode spacing (e.g., horizontal spacing) LEL between the inner edges of the electrodes (504 A and 504B in FIG. 5 or 604A and 604B in FIG. 6) is between about 5 and about 9 microns. With a 1 -micron wide silicon nitride waveguide 506 or 606, horizontal stand-off distances DHOR from the waveguide 506 may be between 2-4 microns on each side. In some embodiments, the electrodes (504A and 504B in FIG. 5 or 604A and 604B in FIG. 6) each may extend to the outer edge of the cavity etched in the oxide, but embodiments of the present disclosure are not limited thereto. For example, the electrodes may extend according to the critical dimensions for the etch process used to open the cavity in the oxide. The metal electrodes may be connected to other metal layers or vias as appropriate to integrate the modulator 500 or 600 into one or more circuits.

[0061] In an embodiment (e.g., the embodiment of FIG. 5) including 1 micron wide x 800 nm high silicon nitnde waveguides and a 60 nm vertical spacer distance and using the OEO material JRD1, assuming an operating wavelength of 1550 nm and an achievable electrooptic coefficient of 200 pm / V for the material, this embodiment can provide highly competitive modulation efficiencies and low optical loss. In the representative calculations using previously described methodology and summarized below in Table 2, the horizontal stand-off distance is 3 microns, which corresponds to the horizontal spacing between the electrodes (including two horizontal stand-off distances and the waveguide width) of 7 microns. The metal electrodes used in the simulations include gold. However, in some embodiments, the electrodes may include copper, aluminum, tungsten, or the like.

[0062] [Table 2]In this embodiment (e.g., the embodiment of FIG. 5), devices can achieve drive voltages below 3 V and insertion losses below 1 dB, with the tradeoff between insertion loss and drive voltage depending on device length. Although this embodiment may require longer phase shifters than the co-planar embodiment (e.g., the embodiment in FIG. 1 or FIG. 2), theembodiment provides the benefit of lower drive voltages compared to the co-planar embodiment. Loss can be further reduced by use of horizontal spacers as in the other embodiments (e.g.. the embodiment of FIG. 6).

[0063] Embodiments of the present disclosure may include crosslinkable OEO materials in order to improve thermal and photochemical stability. Such materials may include in part of one or more polarizable chromophores, small-molecule crosslinking agents, or polymers. In an embodiment, the OEO material may include polarizable chromophores, capable of undergoing a crosslinking reaction to form a thermoset plastic or polymer. For example, the OEO material according to an embodiment of the present disclosure may include one or more polarizable chromophores, one or more crosslinking agents, and one or more polymers.

[0064] Embodiments of the present disclosure may also be incorporated in a photonic integrated circuit including in part of other active and / or passive photonic, electronic, and / or electro-optic components.

[0065] As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of or “one or more of’ or “one or both of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

[0066] The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the embodiments and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

WHAT IS CLAIMED IS:

1. A hybrid electro-optic modulator, comprising: a waveguide including a wide-bandgap material; a first organic electro-optic (OEO) material disposed on a first sidewall of the waveguide; a second OEO material disposed on a second sidewall of the waveguide; a first electrode disposed at a first side of the waveguide; a second electrode disposed at a second side of the waveguide; a first spacer disposed between the OEO material and the first electrode; and a second spacer disposed between the second OEO material and the second electrode.

2. The modulator of claim 1, wherein each of the first and second spacers includes a material having a dielectric constant not less than about 3.9, or a material having a refractive index not greater than about 2.5, or both.

3. The modulator of claim 1, wherein the waveguide comprises silicon nitride.

4. The modulator of claim 1, wherein the waveguide comprises gallium nitride.

5. The modulator of claim 1, wherein a width of each of the first and second spacers is not greater than about 15% of a spacing between the first and second electrodes.

6. The modulator of claim 5, wherein a width of each of the first and second OEO materials is in a range from about 20% to about 60% of the spacing between the first and second electrodes.

7. The modulator of claim 1, wherein the OEO material comprises polarizable chromophores, capable of undergoing a crosslinking reaction to form a thermoset plastic or polymer.

8. The modulator of claim 1, wherein modulation efficiency of the modulator has a value not greater than about 10 V-mm.

9. A photonic integrated circuit comprising the modulator of claim 1, along with other passive and active components.

10. A hybrid electro-optic modulator, comprising: a first wdde-bandgap w aveguide; a second wide-bandgap w aveguide; an organic electro-optic (OEO) material disposed between the first and second waveguides; a first electrode disposed at a first side of the OEO material; a second electrode disposed at a second side of the OEO material; a first spacer disposed between the OEO material and the first electrode; and a second spacer disposed between the OEO material and the second electrode.

11. The modulator of claim 10, w herein each of the first and second spacers includes a material having a dielectric constant not less than about 3.9, or a material having a refractive index not greater than about 2.

5. or both.

12. The modulator of claim 10, w herein each of the first and second waveguides comprises silicon nitride.

13. The modulator of claim 10, wherein each of the first and second waveguides comprises gallium nitride.

14. The modulator of claim 10. wherein a width of each of the first and second spacers is in a range from about 25% to about 35% of a spacing between the first and second electrodes.

15. The modulator of claim 14. wherein a width of each of the first and second w aveguides is in a range from about 10% to about 20% of the spacing between the first and second electrodes.

16. A hybrid electro-optic modulator, comprising:a substrate including a silicon carrier wafer and a buried oxide layer; a silicon nitride waveguide; an oxide layer disposed over the waveguide to enclose the waveguide with the buried oxide layer; an OEO material spaced apart from the waveguide by an oxide spacer, the oxide spacer corresponding to a portion of the oxide layer between the OEO material and the waveguide; and first and second electrodes disposed at a first side and a second side of the OEO material, respectively, and vertically spaced apart from the waveguide by the oxide layer.

17. The modulator of claim 16. further comprising a first additional oxide spacer between the first electrode and the OEO material and a second additional oxide spacer between the second electrode and the OEO material.

18. A hybrid plasmonic electro-optic modulator, comprising: a substrate including gallium nitride (GaN); a waveguide core including an organic electro-optic (OEO) material; and first and second electrodes disposed at first and second sides of the waveguide core.

19. The modulator of claim 18, wherein the first and second electrodes are disposed on first and second sidewalls of the waveguide core, respectively, and each of the first and second electrodes includes gold (Au).

20. A hybrid electro-optic modulator, comprising: a waveguide core including an organic electro-optic (OEO) material; first and second electrodes disposed at first and second sides of the waveguide core; a first waveguide rail including GaN and being disposed on a first sidewall of the waveguide core; a second waveguide rail including GaN and being disposed on a second sidewall of the waveguide core;a first transmission line including doped GaN and connecting the first electrode and the first waveguide rail; and a second transmission line including doped GaN and connecting the second electrode and the second waveguide rail.

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