Strip-loaded optical waveguide

Abstract

The strip-loaded optical waveguide comprises a slab layer, a strip layer, and a cladding layer. The slab layer has a first optical index of refraction and a first width measured laterally perpendicular to a direction of light propagation through the strip-loaded optical waveguide. The strip layer is disposed above the slab layer. The strip layer has a second optical index of refraction and a second width measured laterally. The second width is less than the first width of the slab layer. The second optical index of refraction is less than the first optical index of refraction of the slab layer. A cladding region is disposed above the slab layer and above the strip layer. The cladding region has a third optical index of refraction less than the second optical index of refraction of the strip layer.

Description

[Background technology]

[0001] Optical data communication systems operate by modulating laser light to encode a digital data pattern. The modulated laser light is transmitted from a sending node to a receiving node through an optical data network. Upon reaching the receiving node, the modulated laser light is demodulated to obtain the original digital data pattern. Thus, the implementation and operation of optical data communication systems depends on having reliable and efficient optical waveguides to guide the propagating optical signals. It is against this background that the embodiments disclosed herein arise. Summary of the Invention

[0002] In an example embodiment, a strip-loaded optical waveguide is disclosed. The strip-loaded optical waveguide comprises a slab layer having a first optical index of refraction and a first width measured laterally perpendicular to a direction of light propagation through the strip-loaded optical waveguide. The strip-loaded optical waveguide further comprises a strip layer disposed above the slab layer. The strip layer has a second optical index of refraction and a second width measured laterally. The second width is less than the first width of the slab layer. The second optical index of refraction is less than the first optical index of refraction of the slab layer. The strip-loaded optical waveguide further comprises a cladding layer disposed above the slab layer and above the strip layer. The cladding region has a third optical index of refraction less than the second optical index of refraction of the strip layer.

[0003] In an example embodiment, a method for fabricating an optical waveguide is disclosed. The method comprises disposing a strip layer over a slab layer. The slab layer has a width measured in a lateral direction perpendicular to a direction of light propagation through the optical waveguide. The slab layer has a width measured in the lateral direction. The width of the strip layer is less than the width of the slab layer. The strip layer has an optical index of refraction less than the optical index of the slab layer. The width of the strip layer is set to maximize a size of a zeroth order optical mode in the slab layer below the strip layer without exciting higher order optical modes relative to the zeroth order optical mode. The method further comprises disposing a cladding layer over both the slab layer and the strip layer. The cladding layer has an optical index of refraction less than the optical index of the strip layer.

[0004] In an example embodiment, a multi-strip loaded light guide is disclosed. The multi-strip loaded light guide comprises a slab layer having a first optical index of refraction and a first width measured laterally perpendicular to a direction of light propagation through the multi-strip loaded light guide. The multi-strip loaded light guide further comprises a plurality of strips disposed in a strip layer above the slab layer. Each of the plurality of strips has a strip width measured laterally. Adjacent ones of the plurality of strips are spaced apart from one another by an inter-strip distance measured laterally. Each of the plurality of strips has a second optical index of refraction that is less than the first optical index of refraction of the slab layer. A total distance spanning the plurality of strips in the laterally direction is less than the first width of the slab layer. The multi-strip loaded light guide further comprises a cladding region disposed above the slab layer, above the plurality of strips, and between adjacent ones of the plurality of strips. The cladding region has a third optical index of refraction that is less than the second optical index of refraction of the plurality of strips.

[0005] In an example embodiment, a method for fabricating an optical waveguide is disclosed. The method comprises disposing a plurality of strips on a slab layer. Each of the plurality of strips has a strip width measured in a transverse direction perpendicular to a direction of light propagation through the optical waveguide. Adjacent ones of the plurality of strips are spaced apart from one another by an inter-strip distance measured in the transverse direction. Each of the plurality of strips has a second optical index of refraction that is less than the first optical index of refraction of the slab layer. A total distance across the plurality of strips in the transverse direction is less than a width of the slab layer measured in the transverse direction. The total distance across the plurality of strips in the transverse direction is set to maximize a size of a zeroth order optical mode in the slab layer below the plurality of strips without exciting higher order optical modes relative to the zeroth order optical mode. The method further comprises disposing a cladding layer on the slab layer, on the plurality of strips, and between adjacent ones of the plurality of strips. The cladding layer has an optical index of refraction that is less than the optical index of refraction of the plurality of strips. [Brief description of the drawings]

[0006] [Figure 1A] 1A-1D are vertical cross-sectional views of strip-loaded optical waveguides fabricated in a CMOS platform in accordance with some embodiments.

[0007] [Figure 1B] 1A-1D are vertical cross-sectional views of a multi-strip loaded optical waveguide fabricated in a CMOS platform according to some embodiments.

[0008] [Figure 2A] 1A-1D are vertical cross-sectional views of strip-loaded optical waveguides fabricated in a CMOS platform in accordance with some embodiments.

[0009] [Figure 2B] 4A-4C illustrate simulated quasi-TE optical modes of light propagating through a strip-loaded optical waveguide, in accordance with some embodiments.

[0010] [Figure 2C] 2B illustrates a close-up view of a vertical cross section of the strip-loaded optical waveguide of FIG. 2A, according to some embodiments.

[0011] [Figure 2D] 2C is a close-up view showing simulated quasi-TE optical modes of light propagating through the strip-loaded optical waveguide of FIG. 2B, according to some embodiments.

[0012] [Figure 3A] 2A-2C are vertical cross-sectional views of a single mode strip optical waveguide fabricated in a CMOS platform in accordance with some embodiments.

[0013] [Figure 3B] 3B illustrates simulated quasi-TE optical modes of light propagating through the single mode strip optical waveguide of FIG. 3A in accordance with some embodiments.

[0014] [Figure 4A] 1A-1D are vertical cross-sectional views of strip-loaded optical waveguides fabricated in a CMOS platform in accordance with some embodiments.

[0015] [Figure 4B] 4B illustrates a simulated quasi-TE0 optical mode of light propagating through the strip-loaded optical waveguide of FIG. 4A in accordance with some embodiments.

[0016] [Figure 4C] 4B illustrates a simulated quasi-TE1 optical mode of light propagating through the strip-loaded optical waveguide of FIG. 4A in accordance with some embodiments.

[0017] [Figure 4D] 4B illustrates a simulated quasi-TE2 optical mode of light propagating through the strip-loaded optical waveguide of FIG. 4A in accordance with some embodiments.

[0018] [Figure 5A] 1A-1D are vertical cross-sectional views of a multi-strip loaded optical waveguide fabricated in a CMOS platform according to some embodiments.

[0019] [Figure 5B] 1 illustrates simulated quasi-TE (TE0) optical modes of light propagating through a multi-strip loaded optical waveguide, in accordance with some embodiments.

[0020] [Figure 6A] 1A-1D are vertical cross-sectional views of a multi-strip loaded optical waveguide fabricated in a CMOS platform according to some embodiments.

[0021] [Figure 6B] 1 illustrates simulated quasi-TE0 optical modes of light propagating through a multi-strip loaded optical waveguide in accordance with some embodiments.

[0022] [Figure 6C] 1 illustrates a simulated quasi-TE1 optical mode of light propagating through a multi-strip loaded optical waveguide in accordance with some embodiments.

[0023] [Figure 6D] 4A-4C illustrate simulated quasi-TE2 optical modes of light propagating through a multi-strip loaded optical waveguide, in accordance with some embodiments.

[0024] [Figure 7A] 1B is a vertical cross-sectional view of the strip-loaded optical waveguide of FIG. 1A with PIN junction diodes implemented across the strip-loaded optical waveguide in the x-direction according to some embodiments.

[0025] [Figure 7B]1C is a vertical cross-sectional view of the multi-strip-loaded optical waveguide of FIG. 1B with PIN junction diodes implemented across the multi-strip-loaded optical waveguide in the x-direction according to some embodiments.

[0026] [Figure 8A] 1B is a top view of the strip-loaded optical waveguide of FIG. 1A with interleaved PIN / PN junction diodes implemented within the strip-loaded optical waveguide in accordance with some embodiments.

[0027] [Figure 8B] 8B illustrates a vertical cross-sectional view of the strip-loaded optical waveguide of FIG. 8A along line AA, according to some embodiments.

[0028] [Figure 8C] 8B is another vertical cross-sectional view of the strip-loaded optical waveguide of FIG. 8A taken along line BB, according to some embodiments.

[0029] [Figure 9A] FIG. 1C illustrates a top view of the multi-strip-loaded optical waveguide of FIG. 1B with interleaved PIN / PN junction diodes implemented within the multi-strip-loaded optical waveguide in accordance with some embodiments.

[0030] [Figure 9B] 9B is a vertical cross-sectional view of the multi-strip loaded optical waveguide of FIG. 9A taken along line AA, according to some embodiments.

[0031] [Figure 9C] 9B is another vertical cross-sectional view of the multi-strip loaded optical waveguide of FIG. 9A taken along line of sight BB, according to some embodiments.

[0032] [Figure 10] 1 is a flow chart illustrating a method for fabricating a strip-loaded optical waveguide, according to some embodiments.

[0033] [Figure 11] 1 is a flow chart illustrating a method for fabricating a multi-strip loaded optical waveguide in accordance with some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] In the following description, numerous specific details are set forth in order to provide an understanding of the embodiments disclosed herein. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without some or all of these specific details. In addition, detailed descriptions of well-known process operations are omitted in order to avoid unnecessarily obscuring the disclosed embodiments.

[0035] Various embodiments disclosed herein relate to optical data communication. Integrated photonic platforms are becoming increasingly attractive for a wide range of applications (such as sensing and optical data communication) that benefit from having multiple optical functions implemented on a single chip. In particular, silicon photonic platforms have become a key technology as they allow both electrical and optical functions to be implemented on a single substrate that can be fabricated using existing mature complementary metal oxide semiconductor (CMOS) fabrication processes. Silicon photonics also allows for integrated optical waveguides with high refractive index contrast, which in turn allows for tight bend radii and compact optical system footprints.

[0036] One drawback of utilizing silicon as an optical waveguide material is multi-photon absorption, which leads to increased optical propagation losses at high optical powers. Two-photon absorption (TPA) in particular exists in the optical data communication wavelength range of telecommunications. At high optical intensities, TPA leads to optical absorption in the optical waveguide material, which in turn creates free carriers (electrons or holes that are free to move and are accordingly charged) in the optical waveguide material, which in turn causes both a change in the refractive index of the optical waveguide material due to free carrier dispersion (FCD) and further optical absorption due to free carrier absorption (FCA) in the optical waveguide material. Since TPA is affected by optical intensity, this effect can be mitigated by increasing the size of the optical waveguide so that the peak optical intensity of the propagating mode of light is lower for a given optical power. However, larger optical waveguides typically support propagating light of higher order modes. Excitation of these higher order modes can lead to undesirable optical losses and optical interference effects in the optical waveguide. Various embodiments are disclosed herein that utilize strip-loaded optical waveguides, in which strips of CMOS compatible material are deposited on a silicon slab, to provide lateral light guiding. The quasi-transverse electrical (TE) optical modes supported by the strip-loaded optical waveguides have significantly larger mode areas than strip optical waveguides supporting the same number of propagating optical modes.

[0037] In silicon photonic platforms, optical waveguides and components suffer from increased optical losses at high optical powers due to TPA and FCA. TPA is a nonlinear absorption phenomenon that increases with the intensity of the optical field. TPA is particularly problematic in single-mode strip or rib optical waveguides, which are frequently used in routing optical signals. Furthermore, TPA can cause power-dependent optical loss increases in components that support multiple optical modes of propagating light, such as directional optical couplers or multimode optical interferometers.

[0038] In some applications, the width of the optical waveguide may be increased to increase the optical mode area and reduce the optical intensity of the optical mode (and thus reduce the TPA). However, as a result of increasing the width of the optical waveguide, the optical waveguide supports additional optical modes that are not utilized to carry an optical signal. Any propagating light that is scattered into these additional optical modes may interfere with an optical signal somewhere downstream in the optical system, causing undesirable artifacts in the optical transmission spectrum.

[0039] Various embodiments of optical waveguides are disclosed herein that are configured with a slab layer of silicon, germanium, or silicon germanium alloy and a top dielectric strip that is used as a lateral light guiding mechanism. The optical waveguide configurations described above are referred to as strip-loaded optical waveguides. Compared to the optical modes in a strip or rib optical waveguide that supports a certain number of optical modes, the optical modes in a strip-loaded optical waveguide that supports the same number of optical modes (as the strip or rib optical waveguide) have a significantly larger optical mode area, which may reduce the effect of TPA at high optical powers.

[0040] 1A is a vertical cross-sectional view of a strip-loaded optical waveguide 100 fabricated in a CMOS platform according to some embodiments. The strip-loaded optical waveguide 100 comprises a slab layer 101 having an optical index of refraction n1 and a vertical thickness t1. In various embodiments, the slab layer 101 is formed of silicon, germanium, or a silicon-germanium alloy, among other materials. In some embodiments, the slab layer 101 is undoped. In other embodiments, the slab layer 101 is doped. The strip-loaded optical waveguide 100 further comprises an optical index of refraction n2, a vertical thickness t2 measured in the y-direction, and a width w measured in the x-direction. SIn some embodiments, the strip layer 103 is formed of a dielectric material compatible with CMOS fabrication processes. In some embodiments, the optical index of refraction n2 of the strip layer 103 is less than the optical index of refraction n1 of the slab layer 101. For example, in some embodiments, the strip layer 103 is formed of silicon nitride (SiN x ). However, in some embodiments, the strip layer 103 is formed of another CMOS compatible dielectric material, such as silicon oxynitride (SiON) or aluminum nitride (AlN), among other materials. The width of the slab layer 101 measured in the x-direction is substantially wider than one or more optical modes of the propagating light guided by the strip layer 103.

[0041] In some embodiments, the strip-loaded optical waveguide 100 comprises an intermediate layer 105 disposed between the slab layer 101 and the strip layer 103. The intermediate layer 105 has an optical index of refraction n3 and a vertical thickness t3 measured in the y-direction. The optical index of refraction n3 of the intermediate layer 105 is less than or equal to the optical index of refraction n1 of the slab layer 101. In various embodiments, the intermediate layer 105 is formed of a CMOS compatible dielectric material. In some embodiments of the strip-loaded optical waveguide 100, the intermediate layer 105 is not present, i.e., t3 is equal to zero.

[0042] The strip-loaded optical waveguide 100 is disposed on top of the lower insulator layer 107 having an optical refractive index n5 smaller than the optical refractive index n1 of the slab layer 101. In some embodiments, the lower insulator layer 107 is formed of silicon oxide. In some embodiments, the lower insulator layer 107 is formed of silicon dioxide (SiO2). However, in some embodiments, the lower insulator layer 107 is formed of another CMOS-compatible insulator material, such as aluminum oxide, among others. Also, the cladding region 109 is formed across the top of the strip-loaded optical waveguide 100. The cladding region 109 has an optical refractive index n4 greater than 1 and smaller than the optical refractive index n2 of the strip layer 103 (i.e., 1 < n4 < n2). In some embodiments, the cladding region 109 is formed of silicon oxide (SiO x ). In some embodiments, the cladding region 109 is formed of silicon dioxide (SiO2).

[0043] The strip layer 103 provides a local increase in the effective optical refractive index in the x direction, which provides an optical waveguide. In the vertical direction (y direction), the optical waveguide and optical confinement are provided by the contrast in optical refractive index between the slab layer 101 and the adjacent insulator layer or dielectric layer (e.g., the adjacent portion of the strip layer 103, the intermediate layer 105 (if present), the lower insulator layer 107, and the cladding region 109). For a given combination of the thickness t1 of the slab layer 101 and the thickness t2 of the strip layer 103, the width w of the strip layer 103 S is defined to support either a single quasi-TE mode or multiple quasi-TE modes for the light propagating through the strip-loaded optical waveguide 100.

[0044] FIG. 1B is a vertical cross-sectional view of a multi-strip-loaded light guide 150 fabricated in a CMOS platform according to some embodiments. The multi-strip-loaded light guide 150 is configured similarly to the strip-loaded light guide 100 of FIG. 1A, except that the strip layer 103 of the strip-loaded light guide 100 is replaced with a multi-strip layer 111. The multi-strip layer 111 comprises a number (N) of strips (Strip 1 through Strip N, where N is greater than 1) that define a propagating light guiding region 110 having an effective optical index that increases in the x-direction. The N strips (Strip 1 through Strip N) are arranged in an array configuration within the multi-strip layer 111. Each of the N strips (Strip 1 through Strip N) has an optical index of refraction n2. In some embodiments, each of the N strips (Strip 1 through Strip N) is formed of a dielectric material compatible with CMOS fabrication processes. For example, in some embodiments, each of the N strips (Strip 1 through Strip N) is made of silicon nitride (SiN x However, in some embodiments, each of the N strips (STRIP 1 through STRIP N) is formed of another CMOS compatible dielectric material, such as silicon oxynitride (SiON) or aluminum nitride (AlN), among other materials.

[0045] The N strips (Strip 1 through Strip N) have respective widths (w1 through w N In some embodiments, the N strips (Strip 1 to Strip N) have different widths (w1 to w N ) are substantially equal in size to one another, i.e., uniform. However, in some embodiments, the different widths (w1 to w2) of the N strips (Strip 1 to Strip N) may be different. N ) are not uniform and are different sizes relative to each other. Each of the N strips (Strip 1 to Strip N) has a vertical thickness t2. The N strips are spaced apart by s1 to s N-1The strips are spaced apart from one another in the x-direction by a distance s1 measured between strips 1 and 2, a distance s2 measured between strips 2 and 3, and so on, where distance s N-1 is measured in the x-direction between strip N-1 and strip N. In some embodiments, different spacings (s1 to s2) between adjacently disposed strips among the N strips (strip 1 to strip N) may be used. N-1 ) are substantially equal in size to one another, i.e., uniform. However, in some embodiments, the N strips (Strip 1 to Strip N) may have different spacings (s1 to s N ) are not uniform but are different sizes relative to each other. For a given combination of thickness t1 of slab layer 101 and thickness t2 of multi-strip layer 111, the different widths (w1 to w2) of the N strips (Strip 1 to Strip N) are N ) and different intervals (s1 to s2) between adjacently arranged strips among the N strips (strip 1 to strip N). N-1 ) are collectively defined to support either a single quasi-TE mode or multiple quasi-TE modes for light propagating through the multi-strip loaded optical waveguide 150.

[0046] FIG. 2A is a vertical cross-sectional view of a strip-loaded optical waveguide 100A fabricated in a CMOS platform, according to some embodiments. The strip-loaded optical waveguide 100A is one implementation of the strip-loaded optical waveguide 100 of FIG. 1A. The slab layer 101 in the strip-loaded optical waveguide 100A is made of silicon (Si). The strip layer 103 in the strip-loaded optical waveguide 100A is made of silicon nitride (SiN x). The bottom insulator layer 107 in the strip-loaded optical waveguide 100A is formed of silicon dioxide (SiO2). The middle layer 105 in the strip-loaded optical waveguide 100A is formed of silicon dioxide (SiO2). In some embodiments, the cladding region 109 in the strip-loaded optical waveguide 100A is formed of silicon dioxide (SiO2). In some embodiments, the cladding region 109 in the strip-loaded optical waveguide 100A is formed of silicon dioxide (SiO2). FIG. 2A includes an optical index of refraction (n) scale illustrating the optical index of refraction of various components in the strip-loaded optical waveguide 100A.

[0047] In the example 100A of the strip-loaded optical waveguide, the thickness t1 of the slab layer 101 is about 160 nanometers (nm), the thickness t2 of the strip layer 103 is about 300 nm, the thickness t3 of the intermediate layer 105 is about 25 nm, and the width w S is about 1.45 micrometers (μm). The strip-loaded light guide 100A is an example of a single mode strip-loaded light guide. In some embodiments, for the strip-loaded light guide 100A, the thickness t1 of the slab layer 101 is in the range of about 50 nanometers (nm) to about 4000 nm. In some embodiments, for the strip-loaded light guide 100A, the thickness t2 of the strip layer 103 is in the range of about 20 nm to about 2000 nm. In some embodiments, for the strip-loaded light guide 100A, the thickness t3 of the intermediate layer 105 is in the range of 0 nm to about 250 nm. In some embodiments, for the strip-loaded light guide 100A, the width w S is in the range of about 500 nm to about 3000 nm. As used herein, the term "about" generally includes up to plus or minus 10% of the stated value.

[0048] FIG. 2B illustrates a simulated quasi-TE optical mode 201 of light propagating through the strip-loaded optical waveguide 100A, according to some embodiments. In some embodiments, the TE0 mode 201 of light propagating through the strip-loaded optical waveguide 100A illustrated in FIG. 2B is the only optical mode supported by the strip-loaded optical waveguide 100A at a propagating optical wavelength of 1290 nm. In some embodiments, the propagating optical wavelength for single mode operation of the strip-loaded optical waveguide 100A is in the range of about 1 micrometer to about 17 micrometers. In some embodiments, the propagating optical wavelength for single mode operation of the strip-loaded optical waveguide 100A is set to cover both silicon and germanium transparent windows.

[0049] Figure 2C is a close-up view of a vertical cross section of the strip-loaded optical waveguide 100A of Figure 2A, according to some embodiments, and Figure 2D is a close-up view of simulated quasi-TE optical modes of light propagating through the strip-loaded optical waveguide 100A of Figure 2B, according to some embodiments.

[0050] FIG. 3A is a vertical cross-sectional view of a single mode strip light guide 300 fabricated in a CMOS platform according to some embodiments. The single mode strip light guide 300 comprises a light guide structure 301 formed as a strip of silicon (Si) surrounded by a cladding region 303 formed of silicon dioxide (SiO2). FIG. 3A includes an optical index of refraction (n) scale illustrating the optical index of refraction of various components in the single mode light guide 300. In comparison to the strip-loaded light guide 100A of FIG. 1A, the single mode strip light guide 300 does not comprise an adjacent strip layer 103. It should therefore be understood that the single mode strip light guide 300 is not a strip-loaded light guide as described with respect to FIGS. 1A-2D. In contrast to the slab layer 101 of the strip-loaded light guide 100A of FIG. 1A, the light guide structure 301 has a narrower width w measured in the x-direction. xIn the example single mode strip light guide 300, the light guide structure 301 has a width w x is approximately 250 nm, and the single quasi-TE mode cutoff width w of the propagating light having a wavelength of 1290 nm x Like the slab layer 101 of the strip-loaded optical waveguide 100A of FIG. 1A, the optical waveguide structure 301 has a vertical thickness t y has.

[0051] 3B illustrates a simulated quasi-TE optical mode 305 of light propagating through the single mode strip optical waveguide 300 of FIG. 3A, according to some embodiments. As mentioned above, the width w of the optical waveguide structure 301 measured in the x-direction x is close to the maximum allowable width for supporting only a single TE mode 305 of the propagating light. The single quasi-TE mode cutoff width is the width of the optical waveguide structure 301 at which the optical waveguide structure 301 supports multiple quasi-TE modes. A comparison of Figures 2D and 3B shows the increased area of ​​the TE mode 201 provided by the strip-loaded optical waveguide 100A of Figure 1A compared to the area of ​​the TE mode 305 provided by the single mode strip optical waveguide 300 of Figure 3A. A comparison of Figures 2D and 3B shows that the TE0 mode 201 of the strip-loaded optical waveguide 100A can be significantly wider than the TE0 mode 305 of the single mode strip optical waveguide 300 implemented in the same silicon layer.

[0052] 4A is a vertical cross-sectional view of a strip-loaded optical waveguide 100B fabricated in a CMOS platform, according to some embodiments. The strip-loaded optical waveguide 100B is one implementation of the strip-loaded optical waveguide 100 of FIG. 1A. The slab layer 101 in the strip-loaded optical waveguide 100B is made of silicon (Si). The strip layer 103 in the strip-loaded optical waveguide 100B is made of silicon nitride (SiN x). The bottom insulator layer 107 in the strip-loaded optical waveguide 100B is formed of silicon dioxide (SiO2). The middle layer 105 in the strip-loaded optical waveguide 100B is formed of silicon dioxide (SiO2). The cladding region 109 in the strip-loaded optical waveguide 100B is formed of silicon dioxide (SiO2). FIG. 4A includes an optical index of refraction (n) scale illustrating the optical index of refraction of various components in the strip-loaded optical waveguide 100B.

[0053] In the example 100B of the strip-loaded optical waveguide, the thickness t1 of the slab layer 101 is about 160 nm, the thickness t2 of the strip layer 103 is about 300 nm, the thickness t3 of the intermediate layer 105 is about 25 nm, and the width w S The width w of the strip layer 103 of the strip-loaded optical waveguide 100B is about 5 μm. S is an example of a multimode strip-loaded light guide in which the slab layer 101 is defined to be sufficiently large to support multiple modes of propagating light together with the slab layer 101. In some embodiments, for the multimode strip-loaded light guide 100B, the thickness t1 of the slab layer 101 is in a range from about 50 nm to about 4000 nm. In some embodiments, for the multimode strip-loaded light guide 100B, the thickness t2 of the strip layer 103 is in a range from about 20 nm to about 2000 nm. In some embodiments, for the multimode strip-loaded light guide 100B, the thickness t3 of the intermediate layer 105 is in a range from 0 nm to about 250 nm. In some embodiments, for the multimode strip-loaded light guide 100B, the width w S In some embodiments, the width w of the strip layer 103 is in the range of about 0.5 micrometers to about 100 micrometers. s is set wide enough to include the range for a large free space region or MMI (multimode interferometer), which is effectively an advanced multimode optical waveguide.

[0054] FIG. 4B illustrates a simulated quasi-TE0 optical mode 400 of light propagating through the strip-loaded light guide 100B of FIG. 4A according to some embodiments. FIG. 4C illustrates a simulated quasi-TE1 optical mode 401 of light propagating through the strip-loaded light guide 100B of FIG. 4A according to some embodiments. FIG. 4D illustrates a simulated quasi-TE2 optical mode 402 of light propagating through the strip-loaded light guide 100B of FIG. 4A according to some embodiments. In the examples of FIG. 4B, FIG. 4C, and FIG. 4D, the light propagating through the strip-loaded light guide 100B has a wavelength of 1290 nm. In some embodiments, the propagating light wavelength for multimode operation of the strip-loaded light guide 100B is in the range of about 1 micrometer to about 17 micrometers. In some embodiments, the propagating light wavelength for multimode operation of the strip-loaded optical waveguide 100B is set to cover both silicon and germanium transparent windows.

[0055] FIG. 5A is a vertical cross-sectional view of a multi-strip-loaded optical waveguide 150A fabricated in a CMOS platform according to some embodiments. The multi-strip-loaded optical waveguide 150A is one implementation of the multi-strip-loaded optical waveguide 150 of FIG. 1B, where N is equal to 7, and the strip layer 111 of the multi-strip-loaded optical waveguide 150A comprises seven strips (strip 1 to strip 7). The slab layer 101 in the multi-strip-loaded optical waveguide 150A is formed of silicon (Si). Each of the seven strips (strip 1 to strip 7) in the multi-strip-loaded optical waveguide 150A is formed of silicon nitride (SiN x). The lower insulator layer 107 in the multi-strip-loaded optical waveguide 150A is formed of silicon dioxide (SiO2). The middle layer 105 in the multi-strip-loaded optical waveguide 150A is formed of silicon dioxide (SiO2). The cladding region 109 in the multi-strip-loaded optical waveguide 150A is formed of silicon dioxide (SiO2). FIG. 5A includes an optical index of refraction (n) scale illustrating the optical index of refraction of various components in the multi-strip-loaded optical waveguide 150A.

[0056] In the example 150A of the multi-strip-loaded optical waveguide, the thickness t1 of the slab layer 101 is about 160 nm, the thickness t2 of each of the seven strips (strip 1 to strip 7) is about 300 nm, and the thickness t3 of the intermediate layer 105 is about 25 nm. Each of the widths w1 to w7 of the seven strips (strip 1 to strip 7, respectively) is about 200 nm. Each of the inter-strip spacings s1 to s6 between adjacently arranged strips among the seven strips (strip 1 to strip 7) is about 200 nm. The multi-strip-loaded optical waveguide 150A is an example of a single-mode multi-strip-loaded optical waveguide.

[0057] 5B illustrates a simulated quasi-TE (TE0) optical mode 501 of light propagating through the multi-strip-loaded optical waveguide 150A according to some embodiments. In some embodiments, the TE0 mode 501 of light propagating through the multi-strip-loaded optical waveguide 150A illustrated in FIG. 5B is one optical mode supported by the multi-strip-loaded optical waveguide 150A at a propagating optical wavelength of 1290 nm.

[0058] 6A is a vertical cross-sectional view of a multi-strip-loaded optical waveguide 150B fabricated in a CMOS platform according to some embodiments. The multi-strip-loaded optical waveguide 150B is one implementation of the multi-strip-loaded optical waveguide 150 of FIG. 1B, where N is equal to 17, and the strip layer 111 of the multi-strip-loaded optical waveguide 150B comprises 17 strips (strip 1 to strip 17). The slab layer 101 in the multi-strip-loaded optical waveguide 150B is formed of silicon (Si). Each of the 17 strips (strip 1 to strip 17) in the multi-strip-loaded optical waveguide 150B is formed of silicon nitride (SiN x ). The lower insulator layer 107 in the multi-strip-loaded optical waveguide 150B is formed of silicon dioxide (SiO2). The middle layer 105 in the multi-strip-loaded optical waveguide 150B is formed of silicon dioxide (SiO2). The cladding region 109 in the multi-strip-loaded optical waveguide 150B is formed of silicon dioxide (SiO2). FIG. 6A includes an optical index of refraction (n) scale illustrating the optical index of refraction of various components in the multi-strip-loaded optical waveguide 150B.

[0059] In the example 150B of the multi-strip-loaded optical waveguide, the thickness t1 of the slab layer 101 is about 160 nm, the thickness t2 of each of the 17 strips (strip 1 to strip 17) is about 300 nm, and the thickness t3 of the intermediate layer 105 is about 25 nm. Each of the widths w1 to w7 of the 17 strips (strip 1 to strip 17, respectively) is about 200 nm. The inter-strip spacings s1 to s2 between adjacently arranged strips among the 17 strips (strip 1 to strip 17) are about 200 nm. 16 Each of these is about 200 nm. The multi-strip-loaded optical waveguide 150B is an example of a multimode multi-strip-loaded optical waveguide.

[0060] FIG 6B illustrates a simulated quasi-TE0 optical mode 600 of light propagating through the multi-strip-loaded light guide 150B according to some embodiments. FIG 6C illustrates a simulated quasi-TE1 optical mode 601 of light propagating through the multi-strip-loaded light guide 150B according to some embodiments. FIG 6D illustrates a simulated quasi-TE2 optical mode 602 of light propagating through the multi-strip-loaded light guide 150B according to some embodiments. In the examples of FIG 6B, FIG 6C, and FIG 6D, the light propagating through the multi-strip-loaded light guide 150B has a wavelength of 1290 nm.

[0061] 7A is a vertical cross-sectional view of the strip-loaded optical waveguide 100 of FIG. 1A with PIN junction diodes implemented across the strip-loaded optical waveguide 100 in the x-direction, according to some embodiments. A p-type doped region 701 is formed at the level of the slab layer 101 on a first side of the strip layer 103 in the x-direction. An n-type doped region 703 is formed at the level of the slab layer 101 on a second side of the strip layer 103 in the x-direction. A first conductive metal contact 705 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the p-type doped region 701. A second conductive metal contact 707 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the n-type doped region 703. In this manner, the first metal contact 705 and the second metal contact 707 are formed on opposite sides of the propagating light guiding region within the strip-loaded optical waveguide 100 .

[0062] The portion of the slab layer 101 extending between the p-type doped region 701 and the n-type doped region 703 functions as an intrinsic region such that the p-type doped region 701, the n-type doped region 703, and the portion of the slab layer 101 extending between the p-type doped region 701 and the n-type doped region 703 collectively form a PIN junction diode within the strip-loaded optical waveguide 100. In some embodiments, the width of the p-type doped region 701 and the width of the n-type doped region 703 are defined such that the p-type doped region 701 and the n-type doped region 703 contact each other below the strip layer 103 such that the p-type doped region 701 and the n-type doped region 703 collectively form a PN junction diode within the strip-loaded optical waveguide 100.

[0063] In some embodiments, a potential difference is applied between the first metal contact 705 and the second metal contact 707, where the potential difference is applied across a portion of the slab layer 101 extending between the p-type doped region 701 and the n-type doped region 703. In some embodiments, the potential difference applied across the portion of the slab layer 101 extending between the p-type doped region 701 and the n-type doped region 703 is controlled to locally decrease the free carrier concentration in the propagating light guiding portion of the slab layer 101. In some embodiments, the potential difference applied across the portion of the slab layer 101 extending between the p-type doped region 701 and the n-type doped region 703 is controlled to locally increase the free carrier concentration in the propagating light guiding portion of the slab layer 101. In some embodiments, the potential difference applied across the portion of the slab layer 101 extending between the p-doped region 701 and the n-doped region 703 is controlled to apply a specifically controlled electric field across the propagating light guiding portion of the slab layer 101.

[0064] 7B is a vertical cross-sectional view of the multi-strip loaded optical waveguide 150 of FIG. 1B with PIN junction diodes implemented across the multi-strip loaded optical waveguide 150 in the x-direction, according to some embodiments. A p-type doped region 721 is formed at the level of the slab layer 101 on a first side of the multi-strip layer 111 in the x-direction. An n-type doped region 723 is formed at the level of the slab layer 101 on a second side of the multi-strip layer 111 in the x-direction. A first conductive metal contact 725 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the p-type doped region 721. A second conductive metal contact 727 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the n-type doped region 723. Thus, the first metal contact 725 and the second metal contact 727 are formed on opposite sides of the propagating light guiding region 110 within the multi-strip loaded optical waveguide 150 .

[0065] The portion of the slab layer 101 extending between the p-type doped region 721 and the n-type doped region 723 functions as an intrinsic region such that the p-type doped region 721, the n-type doped region 723, and the portion of the slab layer 101 extending between the p-type doped region 721 and the n-type doped region 723 collectively form a PIN junction diode within the multi-strip loaded optical waveguide 150. In some embodiments, the width of the p-type doped region 721 and the width of the n-type doped region 723 are defined such that the p-type doped region 721 and the n-type doped region 723 contact each other below the multi-strip layer 111 such that the p-type doped region 721 and the n-type doped region 723 collectively form a PN junction diode within the multi-strip loaded optical waveguide 150.

[0066] In some embodiments, a potential difference is applied between the first metal contact 725 and the second metal contact 727, where the potential difference is applied across a portion of the slab layer 101 extending between the p-type doped region 721 and the n-type doped region 723. In some embodiments, the potential difference applied across the portion of the slab layer 101 extending between the p-type doped region 721 and the n-type doped region 723 is controlled to locally decrease the free carrier concentration in the propagating light guiding region 110 of the slab layer 101. In some embodiments, the potential difference applied across the portion of the slab layer 101 extending between the p-type doped region 721 and the n-type doped region 723 is controlled to locally increase the free carrier concentration in the propagating light guiding region 110 of the slab layer 101. In some embodiments, the potential difference applied across the portion of the slab layer 101 extending between the p-doped region 721 and the n-doped region 723 is controlled to apply a specifically controlled electric field across the propagating light guiding region 110 of the slab layer 101.

[0067] Figure 8A is a top view of the strip-loaded light guide 100 of Figure 1A with interleaved PIN / PN junction diodes implemented within the strip-loaded light guide 100 according to some embodiments. Figure 8B is a vertical cross-sectional view of the strip-loaded light guide 100 of Figure 8A along line of sight AA according to some embodiments. Figure 8C is another vertical cross-sectional view of the strip-loaded light guide 100 of Figure 8A along line of sight BB according to some embodiments.

[0068] A highly doped p-type region 801 is formed at the level of the slab layer 101 on a first side of the strip layer 103 in the x-direction. A highly doped n-type region 803 is formed at the level of the slab layer 101 on a second side of the strip layer 103 in the x-direction. A first conductive metal contact 809 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the highly doped p-type region 801. A second conductive metal contact 811 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the highly doped n-type region 803. The highly doped p-type region 801 and the highly doped n-type region 803 are thus formed to provide an ohmic metal contact. The first metal contact 809 and the second metal contact 811 are formed on opposite sides of the propagating light guiding region 110 in the strip-loaded optical waveguide 100.

[0069] A series of p-type doped regions 805 are formed at the level of the slab layer 101, extending from the highly p-type doped region 801 below the strip layer 103 to the propagating light guiding region. A series of n-type doped regions 807 are formed at the level of the slab layer 101, extending from the highly n-type doped region 803 below the strip layer 103 to the propagating light guiding region. The p-type doped regions 805 and the n-type doped regions 807 are alternately arranged along the length of the strip-loaded optical waveguide 100 in the z-direction. In this way, the series of p-type doped regions 805 and the series of n-type doped regions 807 are interleaved along the length of the strip-loaded optical waveguide 100 in the z-direction. The portions of the slab layer 101 located between adjacent ones of the p-type doped region 805 and the n-type doped region 807 function as intrinsic regions such that the p-type doped region 805, the n-type doped region 807, and the portions of the slab layer 101 located between the p-type doped region 805 and the n-type doped region 807 collectively form various PIN junction diodes within the strip-loaded optical waveguide 100.

[0070] In some embodiments, the length d1 of the p-doped region 805 measured in the z-direction and the length d2 of the n-doped region 807 measured in the z-direction are defined separately relative to one another and may vary depending on the implementation. In some embodiments, the length d1 of the p-doped region 805 measured in the z-direction is substantially uniform within the series of p-doped regions 805 formed along the length of the strip-loaded optical waveguide 100 in the z-direction. In some embodiments, different regions of the p-doped region 805 have different lengths d1 measured in the z-direction within the series of p-doped regions 805 formed along the length of the strip-loaded optical waveguide 100 in the z-direction. In some embodiments, the length d1 of the p-doped region 805 is in the range of 0 micrometers to about 20 micrometers.

[0071] In some embodiments, the length d2 of the n-doped region 807 measured in the z-direction is substantially uniform within the series of n-doped regions 807 formed along the length of the strip-loaded optical waveguide 100 in the z-direction. In some embodiments, different regions of the n-doped region 807 have different lengths d2 measured in the z-direction within the series of n-doped regions 807 formed along the length of the strip-loaded optical waveguide 100 in the z-direction. In some embodiments, the length d2 of the n-doped region 807 is in the range from 0 micrometers to about 20 micrometers.

[0072] The p-type doped region 805 is separated from the highly n-type doped region 803 by a distance d3 measured in the x-direction. The n-type doped region 807 is separated from the highly p-type doped region 801 by a distance d4 measured in the x-direction. A given region of the n-type doped region 807 is separated from a first adjacent region of the p-type doped region 805 by a distance d5 measured in the z-direction and from a second adjacent region of the p-type doped region 805 by a distance d6 measured in the z-direction. The distances d3, d4, d5, and d6 define the size of the intrinsic region that exists between the p-type doped region 801 / 805 and the n-type doped region 803 / 807.

[0073] In various embodiments, the distance d3 at a given location in the strip-loaded optical waveguide 100 is greater than zero such that a PIN junction diode is formed at the given location by the p-type doped region 805, the highly n-type doped region 803, and the intervening portions of the slab layer 101. In various embodiments, the distance d3 at a given location in the strip-loaded optical waveguide 100 is zero such that a PN junction diode is formed at the given location by the p-type doped region 805 and the highly n-type doped region 803. In some embodiments, the distance d3 at a given location in the strip-loaded optical waveguide 100 is in the range of 0 nm to about 500 nm.

[0074] In various embodiments, the distance d4 at a given location in the strip-loaded optical waveguide 100 is greater than zero such that a PIN junction diode is formed at the given location by the n-type doped region 807, the highly p-type doped region 801, and the intervening portions of the slab layer 101. In various embodiments, the distance d4 at a given location in the strip-loaded optical waveguide 100 is zero such that a PN junction diode is formed at the given location by the n-type doped region 807 and the highly p-type doped region 801. In some embodiments, the distance d4 at a given location in the strip-loaded optical waveguide 100 is in the range of 0 nm to about 500 nm.

[0075] In various embodiments, the distance d5 at a given location in the strip-loaded optical waveguide 100 is greater than zero such that a PIN junction diode is formed at the given location by adjacent p-type doped regions 805 and n-type doped regions 807 and intervening portions of the slab layer 101. In various embodiments, the distance d5 at a given location in the strip-loaded optical waveguide 100 is zero such that a PN junction diode is formed at the given location by adjacent p-type doped regions 805 and n-type doped regions 807. In some embodiments, the distance d5 at a given location in the strip-loaded optical waveguide 100 is in the range of 0 nm to about 500 nm.

[0076] In various embodiments, the distance d6 at a given location in the strip-loaded optical waveguide 100 is greater than zero such that a PIN junction diode is formed at the given location by adjacent p-type doped regions 805 and n-type doped regions 807 and intervening portions of the slab layer 101. In various embodiments, the distance d6 at a given location in the strip-loaded optical waveguide 100 is zero such that a PN junction diode is formed at the given location by adjacent p-type doped regions 805 and n-type doped regions 807. In some embodiments, the distance d6 at a given location in the strip-loaded optical waveguide 100 is in the range of 0 nm to about 500 nm.

[0077] Figure 9A is a top view of the multi-strip-loaded light guide 150 of Figure 1B with interleaved PIN / PN junction diodes implemented within the multi-strip-loaded light guide 150 according to some embodiments. Figure 9B is a vertical cross-sectional view of the multi-strip-loaded light guide 150 of Figure 9A along line of sight AA according to some embodiments. Figure 9C is another vertical cross-sectional view of the multi-strip-loaded light guide 150 of Figure 9A along line of sight BB according to some embodiments.

[0078] A p-type highly doped region 901 is formed at the level of the slab layer 101 on a first side of the multi-strip layer 111 in the x-direction. A n-type highly doped region 903 is formed at the level of the slab layer 101 on a second side of the multi-strip layer 111 in the x-direction. A first conductive metal contact 909 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the p-type highly doped region 901. A second conductive metal contact 911 is formed extending vertically in the y-direction through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the n-type highly doped region 903. In this way, the p-type highly doped region 901 and the n-type highly doped region 903 are formed to provide an ohmic metal contact. The first metal contact 909 and the second metal contact 911 are formed on opposite sides of the propagating light guiding region 110 in the multi-strip loaded optical waveguide 150.

[0079] A series of p-type doped regions 905 are formed at the level of the slab layer 101 so as to extend from the highly p-type doped region 901 below the strip layer 103 to the propagating light guiding region. A series of n-type doped regions 907 are formed at the level of the slab layer 101 so as to extend from the highly n-type doped region 903 below the strip layer 103 to the propagating light guiding region. The p-type doped regions 905 and the n-type doped regions 907 are alternately arranged along the length of the multi-strip loaded optical waveguide 150 in the z-direction. In this way, the series of p-type doped regions 905 and the series of n-type doped regions 907 are interleaved along the length of the multi-strip loaded optical waveguide 150 in the z-direction. The portions of the slab layer 101 located between adjacent ones of the p-type doped region 905 and the n-type doped region 907 function as intrinsic regions such that the p-type doped region 905, the n-type doped region 907, and the portions of the slab layer 101 located between the p-type doped region 905 and the n-type doped region 907 collectively form various PIN junction diodes within the multi-strip loaded optical waveguide 150.

[0080] In some embodiments, the length d1 of the p-doped region 905 measured in the z-direction and the length d2 of the n-doped region 907 measured in the z-direction are defined separately relative to one another and may vary depending on the implementation. In some embodiments, the length d1 of the p-doped region 905 measured in the z-direction is substantially uniform within the series of p-doped regions 905 formed along the length of the multi-strip loaded optical waveguide 150 in the z-direction. In some embodiments, different regions of the p-doped region 905 have different lengths d1 measured in the z-direction within the series of p-doped regions 905 formed along the length of the multi-strip loaded optical waveguide 150 in the z-direction. In some embodiments, the length d1 of the p-doped region 905 is in the range of 0 micrometers to about 20 micrometers.

[0081] In some embodiments, the length d2 of the n-doped region 907 measured in the z-direction is substantially uniform within the series of n-doped regions 907 formed along the length of the multi-strip loaded optical waveguide 150 in the z-direction. In some embodiments, different regions of the n-doped region 907 have different lengths d2 measured in the z-direction within the series of n-doped regions 907 formed along the length of the multi-strip loaded optical waveguide 150 in the z-direction. In some embodiments, the length d2 of the n-doped region 907 is in the range from 0 micrometers to about 20 micrometers.

[0082] The p-doped region 905 is separated from the highly n-doped region 903 by a distance d3 measured in the x-direction. The n-doped region 907 is separated from the highly p-doped region 901 by a distance d4 measured in the x-direction. A given region of the n-doped region 907 is separated from a first adjacent region of the p-doped region 905 by a distance d5 measured in the z-direction and from a second adjacent region of the p-doped region 905 by a distance d6 measured in the z-direction. The distances d3, d4, d5, and d6 define the size of the intrinsic region that exists between the p-doped region 901 / 905 and the n-doped region 903 / 907.

[0083] In various embodiments, the distance d3 at a given location in the multi-strip loaded optical waveguide 150 is greater than zero such that a PIN junction diode is formed at the given location by the p-type doped region 905, the highly n-type doped region 903, and the intervening portions of the slab layer 101. In various embodiments, the distance d3 at a given location in the multi-strip loaded optical waveguide 150 is zero such that a PN junction diode is formed at the given location by the p-type doped region 905 and the highly n-type doped region 903. In some embodiments, the distance d3 at a given location in the multi-strip loaded optical waveguide 150 is in the range of 0 nm to about 500 nm.

[0084] In various embodiments, the distance d4 at a given location in the multi-strip loaded optical waveguide 150 is greater than zero such that a PIN junction diode is formed at the given location by the n-type doped region 907, the highly p-type doped region 901, and the intervening portions of the slab layer 101. In various embodiments, the distance d4 at a given location in the multi-strip loaded optical waveguide 150 is zero such that a PN junction diode is formed at the given location by the n-type doped region 907 and the highly p-type doped region 901. In some embodiments, the distance d4 at a given location in the multi-strip loaded optical waveguide 150 is in the range of 0 nm to about 500 nm.

[0085] In various embodiments, the distance d5 at a given location in the multi-strip loaded optical waveguide 150 is greater than zero such that a PIN junction diode is formed at the given location by adjacent p-type doped regions 905 and n-type doped regions 907 and intervening portions of the slab layer 101. In various embodiments, the distance d5 at a given location in the multi-strip loaded optical waveguide 150 is zero such that a PN junction diode is formed at the given location by adjacent p-type doped regions 905 and n-type doped regions 907. In some embodiments, the distance d5 at a given location in the multi-strip loaded optical waveguide 150 is in the range of 0 nm to about 500 nm.

[0086] In various embodiments, the distance d6 at a given location in the multi-strip loaded optical waveguide 150 is greater than zero such that a PIN junction diode is formed at the given location by adjacent p-type doped regions 905 and n-type doped regions 907 and intervening portions of the slab layer 101. In various embodiments, the distance d6 at a given location in the multi-strip loaded optical waveguide 150 is zero such that a PN junction diode is formed at the given location by adjacent p-type doped regions 905 and n-type doped regions 907. In some embodiments, the distance d6 at a given location in the multi-strip loaded optical waveguide 150 is in the range of 0 nm to about 500 nm.

[0087] In some embodiments, the strip-loaded optical waveguide 100, 100A, 100B comprises a slab layer 101, a strip layer 103, and a cladding region 109. The slab layer 101 has an optical index of refraction (n1) and a first width measured in a lateral direction (x-direction) perpendicular to the direction of light propagation (z-direction) through the strip-loaded optical waveguide 100, 100A, 100B. The strip layer 103 is disposed above the slab layer 101. The strip layer 103 has an optical index of refraction (n2) and a second width measured in the lateral direction (x-direction) (w s ) and the second width (w s) is smaller than the first width of the slab layer 101. The optical index of refraction (n2) of the strip layer 103 is smaller than the optical index of refraction (n1) of the slab layer 101. The cladding region 109 is disposed above the slab layer 101 and above the strip layer 103. The cladding region 109 has an optical index of refraction (n4) smaller than the optical index of refraction (n2) of the strip layer 103. In some embodiments, the strip-loaded optical waveguide 100, 100A, 100B comprises an insulator layer 107, where the slab layer 101 is disposed on the insulator layer 107. The insulator layer 107 has an optical index of refraction (n5) smaller than the optical index of refraction (n1) of the slab layer 101. In some embodiments, the strip-loaded optical waveguide 100, 100A, 100B comprises an intermediate layer 105 disposed above the slab layer 101 and below the strip layer 103. The intermediate layer 105 has an optical refractive index (n3) that is equal to or less than the optical refractive index (n1) of the slab layer 101.

[0088] The strip layer 103 provides a local increase in the effective optical index in the lateral direction (x-direction). In some embodiments, the second width (w s ) is defined to support a single optical propagation mode through the strip-loaded optical waveguides 100, 100A, 100B. In some embodiments, the second width (w s ) is defined to support multiple optical propagation modes through the strip-loaded optical waveguides 100, 100A, 100B. In some embodiments, the second width (w s ) is in the range of about 0.5 micrometers to about 100 micrometers. In some embodiments, the vertical thickness (t1) of the slab layer 101 is in the range of about 50 nanometers to about 4000 nanometers, and the vertical thickness (t2) of the strip layer 103 is in the range of about 20 nanometers to about 2000 nanometers.

[0089] In some embodiments, the slab layer 101 is formed of one or more of silicon, germanium, and silicon germanium alloy, and the strip layer 103 is formed of one or more of silicon nitride, silicon oxynitride, and aluminum nitride. In some embodiments, the cladding region 109 is formed of silicon oxide. In some embodiments, the insulator layer 107 is formed of silicon dioxide or aluminum oxide. In some embodiments, the intermediate layer 105 is formed of a dielectric material.

[0090] In some embodiments, the strip-loaded optical waveguide 100, 100A, 100B comprises a p-type doped region 701 formed in a first portion of the slab layer 101 on a first side of the strip layer 103 in the lateral direction (x-direction). In these embodiments, the strip-loaded optical waveguide 100, 100A, 100B further comprises a first metal contact structure 705 formed through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the p-type doped region 701. In these embodiments, the strip-loaded optical waveguide 100, 100A, 100B further comprises an n-type doped region 703 formed in a second portion of the slab layer 101 on a second side of the strip layer 103 opposite the first side of the strip layer 103 in the lateral direction (x-direction). In these embodiments, the strip-loaded optical waveguide 100, 100A, 100B further comprises a second metal contact structure 707 formed through the cladding region 109 and the intermediate layer 105 (if present) to make electrical contact with the n-type doped region 703. In some embodiments, the first metal contact structure 705 and the second metal contact structure 707 are electrically connected to apply a potential difference across the portion of the slab layer 101 that extends between the p-type doped region 701 and the n-type doped region 703.

[0091] In some embodiments, the p-type doped region 701 is a first p-type doped region 801 configured to extend along the length of the strip-loaded optical waveguide 100, 100A, 100B measured in the direction of light propagation (z-direction) through the strip-loaded optical waveguide 100, 100A, 100B, and the n-type doped region 703 is a first n-type doped region 803 configured to extend along the length of the strip-loaded optical waveguide 100, 100A, 100B measured in the direction of light propagation (z-direction) through the strip-loaded optical waveguide 100, 100A, 100B. The strip-loaded optical waveguide 100, 100A, 100B further comprises a series of p-type doped regions 805 formed in the slab layer 101. Each p-type doped region 805 in the series of p-type doped regions 805 extends laterally (x-direction) below the strip layer 103 from the first p-type doped region 801 to the first n-type doped region 803. Adjacent p-type doped regions 805 in the series of p-type doped regions 805 are spaced apart from each other in the direction of light propagation (z-direction) through the strip-loaded optical waveguide 100, 100A, 100B. In these embodiments, the strip-loaded optical waveguide 100, 100A, 100B further comprises a series of n-type doped regions 807 formed in the slab layer 101. Each n-type doped region 807 in the series of n-type doped regions 807 extends laterally (x-direction) below the strip layer 103 from the first n-type doped region 803 to the first p-type doped region 801. Each n-type doped region 807 in the series of n-type doped regions 807 is disposed between a respective pair of adjacently disposed p-type doped regions 805 in the series of p-type doped regions 805 .

[0092] In some embodiments, each of the series of n-type doped regions 807 is spaced apart from both the first p-type doped region 801 and the series of p-type doped regions 805 to form one or more PIN junction diodes. In some embodiments, each of the series of p-type doped regions 805 is spaced apart from both the first n-type doped region 803 and the series of n-type doped regions 807 to form one or more PIN junction diodes. In some embodiments, each of the series of n-type doped regions 807 contacts the first p-type doped region 801 and one or more of the series of p-type doped regions 805 to form one or more PN junction diodes. In some embodiments, each of the series of p-type doped regions 805 contacts the first n-type doped region 803 and one or more of the series of n-type doped regions 807 to form one or more PN junction diodes.

[0093] 10 is a flow chart illustrating a method for fabricating a strip-loaded optical waveguide 100, 100A, 100B according to some embodiments. The method comprises step 1001 of disposing a strip layer 103 on a slab layer 101. The strip layer 103 has a width (w s The slab layer 101 has a width (w s The strip layer 103 has a width measured in the lateral direction (x direction) such that the width (w) of the strip layer 103 is smaller than the width of the slab layer 101. The strip layer 103 has an optical index of refraction (n2) smaller than the optical index of refraction (n1) of the slab layer 101. s ) is set to maximize the size of the zeroth order optical mode in the slab layer 101 below the strip layer 103 without substantially exciting higher order optical modes relative to the zeroth order optical mode. The method further comprises the step 1003 of disposing a cladding layer 109 over both the slab layer 101 and the strip layer 103. The cladding layer 109 has an optical index of refraction (n4) that is less than the optical index of refraction (n2) of the strip layer 103.

[0094] In some embodiments, the multi-strip-loaded optical waveguide 150, 150A, 150B comprises a slab layer 101, a plurality of strips in a multi-strip layer 111, and a cladding region 109. The slab layer 101 has an optical index of refraction (n1) and a first width measured in a lateral direction (x-direction) perpendicular to the direction of light propagation (z-direction) through the multi-strip-loaded optical waveguide 150, 150A, 150B. The plurality of strips are disposed in the multi-strip layer 111 above the slab layer 101. Each of the plurality of strips has a strip width measured in the lateral direction (x-direction). Adjacently disposed strips of the plurality of strips are spaced apart from each other by an inter-strip distance measured in the lateral direction (x-direction). Each of the plurality of strips has an optical index of refraction (n2) that is less than the optical index of refraction (n1) of the slab layer 101. A total distance spanning the plurality of strips in the lateral direction (x-direction) is less than a width of the slab layer 101. The cladding region 109 is disposed above the slab layer 101, above the plurality of strips, and between adjacent ones of the plurality of strips. The cladding region 109 has an optical index of refraction (n4) less than the optical index of refraction (n2) of the plurality of strips. In some embodiments, the multi-strip loaded optical waveguide 150, 150A, 150B comprises an insulator layer 107, where the slab layer 101 is disposed on the insulator layer 107. The insulator layer 107 has an optical index of refraction (n5) less than the optical index of refraction (n1) of the slab layer 101. In some embodiments, the multi-strip loaded optical waveguide 150, 150A, 150B comprises an intermediate layer 105 disposed above the slab layer 101 and below the plurality of strips. The intermediate layer 105 has an optical index of refraction (n3) less than or equal to the optical index of refraction (n1) of the slab layer 101.

[0095] In some embodiments, the strips provide a localized increase in the effective optical index in the lateral direction (x-direction). In some embodiments, the total distance spanned by the strips in the lateral direction (x-direction) is defined to support a single optical propagation mode through the multi-strip loaded optical waveguide 150, 150A, 150B. In some embodiments, the total distance spanned by the strips in the lateral direction (x-direction) is defined to support multiple optical propagation modes through the multi-strip loaded optical waveguide 150, 150A, 150B.

[0096] In some embodiments, the total distance across the plurality of strips in the lateral direction (x-direction) is in the range of about 0.5 micrometers to about 100 micrometers. In some embodiments, the strip width (w2) is in the range of about 100 nanometers to about 1000 nanometers. In some embodiments, the strip width (w2) is substantially the same for each of the plurality of strips. In some embodiments, the strip width (w2) is different for at least two of the plurality of strips. In some embodiments, the inter-strip distance (i.e., the spacing between adjacently disposed strips measured in the lateral (x) direction) is in the range of about 100 nanometers to about 1000 nanometers. In some embodiments, the inter-strip distance is substantially the same between each adjacent strip pair in the plurality of strips. In some embodiments, the inter-strip distance is different between at least two different adjacent strip pairs in the plurality of strips. In some embodiments, the vertical thickness (t1) of the slab layer 101 is in the range of about 50 nanometers to about 4000 nanometers, and the vertical thickness (t2) of each of the plurality of strips is in the range of about 20 nanometers to about 2000 nanometers.

[0097] In some embodiments, the slab layer 101 is formed of one or more of silicon, germanium, and a silicon germanium alloy, and each of the plurality of strips is formed of one or more of silicon nitride, silicon oxynitride, and aluminum nitride. In some embodiments, the cladding region 109 is formed of silicon oxide. In some embodiments, the insulator layer 107 is formed of silicon dioxide or aluminum oxide. In some embodiments, the intermediate layer 105 is formed of a dielectric material.

[0098] In some embodiments, the multi-strip loaded optical waveguide 150, 150A, 150B comprises a p-type doped region 721 formed in a first portion of the slab layer 101 on a first side of the strips in the lateral direction (x-direction). A first metal contact structure 725 is formed through the cladding region 109 and the intermediate layer 105 (if present) in electrical contact with the p-type doped region 721. An n-type doped region 723 is formed in a second portion of the slab layer 101 on a second side of the strips opposite the first side of the strips in the lateral direction (x-direction). A second metal contact structure 727 is formed through the cladding region 109 and the intermediate layer 105 (if present) in electrical contact with the n-type doped region 723. In some embodiments, the first metal contact structure 725 and the second metal contact structure 727 are electrically connected to apply a potential difference across the portion of the slab layer 101 extending between the p-type doped region 721 and the n-type doped region 723.

[0099] In some embodiments, the p-type doped region 721 is a first p-type doped region 901 configured to extend along the length of the multi-strip loaded optical waveguide 150, 150A, 150B measured in the direction of light propagation through the multi-strip loaded optical waveguide 150, 150A, 150B (z-direction), and the n-type doped region 723 is a first n-type doped region 903 configured to extend along the length of the multi-strip loaded optical waveguide 150, 150A, 150B measured in the direction of light propagation through the multi-strip loaded optical waveguide 150, 150A, 150B (z-direction), and the multi-strip loaded optical waveguide 150, 150A, 150B comprises a series of p-type doped regions 905 formed within the slab layer 101. Each p-type doped region 905 in the series of p-type doped regions 905 extends laterally (x-direction) below the strips from the first p-type doped region 901 to the first n-type doped region 903. Adjacent p-type doped regions 905 in the series of p-type doped regions 905 are spaced apart from each other in the direction of light propagation (z-direction) through the multi-strip loaded optical waveguide 150, 150A, 150B. The multi-strip loaded optical waveguide 150, 150A, 150B also includes a series of n-type doped regions 907 formed in the slab layer 101. Each n-type doped region 907 in the series of n-type doped regions 907 extends laterally (x-direction) below the strips from the first n-type doped region 903 to the first p-type doped region 901. Each n-type doped region 907 in the series of n-type doped regions 907 is disposed between a respective pair of adjacently disposed p-type doped regions 905 in the series of p-type doped regions 905 .

[0100] In some embodiments, each of the series of n-type doped regions 907 is spaced apart from both the first p-type doped region 901 and the series of p-type doped regions 905 to form one or more PIN junction diodes. In some embodiments, each of the series of p-type doped regions 905 is spaced apart from both the first n-type doped region 903 and the series of n-type doped regions 907 to form one or more PIN junction diodes. In some embodiments, each of the series of n-type doped regions 907 contacts the first p-type doped region 901 and one or more of the series of p-type doped regions 905 to form one or more PN junction diodes. In some embodiments, each of the series of p-type doped regions 905 contacts the first n-type doped region 903 and one or more of the series of n-type doped regions 907 to form one or more PN junction diodes.

[0101] FIG. 11 is a flow chart illustrating a method for fabricating a multi-strip loaded light guide 150, 150A, 150B according to some embodiments. The method comprises a step 1101 of disposing a plurality of strips on a slab layer 101. Each of the plurality of strips has a strip width measured in a lateral direction (x-direction) perpendicular to the direction of light propagation (z-direction) through the multi-strip loaded light guide 150, 150A, 150B. Adjacently disposed strips of the plurality of strips are spaced apart from each other by an inter-strip distance measured in the lateral direction (x-direction). Each of the plurality of strips has an optical index of refraction (n2) that is smaller than the optical index of refraction (n1) of the slab layer 101. A total distance spanning the plurality of strips in the lateral direction (x-direction) is smaller than a width of the slab layer 101 measured in the lateral direction (x-direction). The total distance across the plurality of strips in the lateral direction (x-direction) is set to maximize the size of the zeroth order optical mode in the slab layer 101 beneath the plurality of strips without exciting higher order optical modes relative to the zeroth order optical mode. The method further comprises the step 1101 of disposing a cladding layer 109 over the slab layer 101, over the plurality of strips, and between adjacently disposed ones of the plurality of strips. The cladding layer 109 has an optical index of refraction (n4) less than the optical index of refraction (n2) of the plurality of strips.

[0102] The above description of the embodiments is for illustrative and descriptive purposes and is not intended to be exhaustive or limiting. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment and, where applicable, can be substituted and utilized in selected embodiments unless otherwise shown or described. Thus, one or more features from one or more embodiments disclosed herein can be combined with one or more features from one or more other embodiments disclosed herein to form another embodiment that is not explicitly disclosed herein but is implicitly disclosed herein. This other embodiment may also be modified in many ways. Such variations of the embodiments are not considered departures from the present disclosure, and all such variations and modifications of the embodiments are intended to be included within the scope of the disclosure provided herein.

[0103] Although some method steps may be described in a particular order herein, it should be understood that other housekeeping steps may be performed between method steps, and / or method steps may be coordinated to be performed at slightly different times or simultaneously, or distributed into a system that permits process steps to be performed at various intervals related to the process, so long as the processing of the method steps is performed in a manner such that the method is successfully performed.

[0104] Although the present embodiments have been described in some detail for ease of understanding, it will be apparent that certain changes and modifications may be made within the scope of the appended claims. Accordingly, the embodiments disclosed herein are considered to be illustrative and not restrictive, and therefore should not be limited to only the details set forth herein, but may be modified within the scope and equivalents of the appended claims.

Claims

1. A strip-loaded optical waveguide, a slab layer having a first optical refractive index and a first width measured in a lateral direction perpendicular to the direction of light propagation through the strip-loaded optical waveguide; a strip layer disposed above the slab layer, the strip layer having a second optical index of refraction and a second width measured in the lateral direction, the second width being less than the first width of the slab layer and the second optical index of refraction being less than the first optical index of refraction of the slab layer; a cladding region disposed above the slab layer and above the strip layer, the cladding region having a third optical index of refraction less than the second optical index of refraction of the strip layer; A strip-loaded optical waveguide comprising:

2. 2. The strip-loaded optical waveguide of claim 1, wherein the strip layer provides a local increase in effective optical refractive index in the lateral direction.

3. 2. The strip-loaded optical waveguide of claim 1, wherein the second width of the strip layer is defined to support a single optical propagation mode through the strip-loaded optical waveguide.

4. 2. The strip-loaded optical waveguide of claim 1, wherein the second width of the strip layer is configured to support a plurality of optical propagation modes through the strip-loaded optical waveguide.

5. 2. The strip-loaded optical waveguide of claim 1, wherein the second width of the strip layer is in a range from about 0.5 micrometers to about 100 micrometers.

6. 2. The strip-loaded optical waveguide of claim 1, wherein the slab layer is formed of one or more of silicon, germanium, and a silicon germanium alloy, and the strip layer is formed of one or more of silicon nitride, silicon oxynitride, and aluminum nitride.

7. 2. The strip-loaded optical waveguide of claim 1, wherein the cladding region is formed of silicon oxide.

8. 2. The strip-loaded optical waveguide of claim 1, wherein the vertical thickness of the slab layer is in the range of about 50 nanometers to about 4000 nanometers, and the vertical thickness of the strip layer is in the range of about 20 nanometers to about 2000 nanometers.

9. 2. The strip-loaded optical waveguide according to claim 1, further comprising:

13. A strip-loaded optical waveguide comprising: an insulator layer, the slab layer disposed on the insulator layer, the insulator layer having a fourth optical refractive index less than the first optical refractive index of the slab layer.

10. 10. The strip-loaded optical waveguide of claim 9, wherein the insulator layer is made of silicon dioxide or aluminum oxide.

11. 2. The strip-loaded optical waveguide according to claim 1, further comprising: a strip-loaded optical waveguide comprising an intermediate layer disposed above the slab layer and below the strip layer, the intermediate layer having a fourth optical refractive index less than or equal to the first optical refractive index of the slab layer.

12. 12. The strip-loaded optical waveguide of claim 11, wherein the intermediate layer is formed of a dielectric material.

13. The strip-loaded optical waveguide according to claim 12, further comprising: a p-type doped region formed in a first portion of the slab layer on a first side of the strip layer in the lateral direction; a first metal contact structure formed through the cladding region and the intermediate layer in electrical contact with the p-type doped region; an n-type doped region formed in a second portion of the slab layer on a second side of the strip layer opposite the first side of the strip layer in the lateral direction; a second metal contact structure formed through the cladding region and the intermediate layer in electrical contact with the n-type doped region; A strip-loaded optical waveguide comprising:

14. 14. The strip-loaded optical waveguide of claim 13, wherein the first metal contact structure and the second metal contact structure are electrically connected to apply a potential difference across a portion of the slab layer extending between the p-type doped region and the n-type doped region.

15. 14. The strip-loaded optical waveguide of claim 13, wherein the p-type doped region is a first p-type doped region configured to extend along a length of the strip-loaded optical waveguide measured in a direction of light propagation through the strip-loaded optical waveguide, and the n-type doped region is a first n-type doped region configured to extend along the length of the strip-loaded optical waveguide measured in the direction of light propagation through the strip-loaded optical waveguide; The strip-loaded optical waveguide further comprises: a series of p-type doped regions formed in the slab layer, each p-type doped region of the series of p-type doped regions extending in the lateral direction beneath the strip layer from the first p-type doped region to the first n-type doped region, adjacent p-type doped regions in the series of p-type doped regions being spaced apart from one another in the direction of light propagation through the strip-loaded optical waveguide; a series of n-type doped regions formed in the slab layer, each n-type doped region of the series of n-type doped regions extending in the lateral direction below the strip layer from the first n-type doped region to the first p-type doped region, each n-type doped region of the series of n-type doped regions being disposed between a respective pair of adjacently disposed p-type doped regions of the series of p-type doped regions.

16. 16. The strip-loaded optical waveguide of claim 15, wherein each of the series of n-type doped regions is spaced apart from both the first p-type doped region and the series of p-type doped regions so as to form one or more PIN junction diodes.

17. 16. The strip-loaded optical waveguide of claim 15, wherein each of the series of p-type doped regions is spaced apart from both the first n-type doped region and the series of n-type doped regions so as to form one or more PIN junction diodes.

18. 16. The strip-loaded optical waveguide of claim 15, wherein each of the series of n-type doped regions contacts the first p-type doped region and one or more of the series of p-type doped regions to form one or more PN junction diodes.

19. 16. The strip-loaded optical waveguide of claim 15, wherein each of the series of p-type doped regions contacts the first n-type doped region and one or more of the series of n-type doped regions to form one or more PN junction diodes.

20. 1. A method for manufacturing an optical waveguide, comprising the steps of: disposing a strip layer above a slab layer, the strip layer having a width measured in a lateral direction perpendicular to a direction of light propagation through the optical waveguide, the slab layer having a width measured in the lateral direction, the width of the strip layer being less than the width of the slab layer, the strip layer having an optical index of refraction less than an optical index of refraction of the slab layer, the width of the strip layer being set to maximize a size of the zeroth order optical mode in the slab layer below the strip layer without exciting higher order optical modes relative to a zeroth order optical mode; The method comprising disposing a cladding layer over both the slab layer and the strip layer, the cladding layer having an optical index of refraction less than the optical index of refraction of the strip layer.

21. A multi-strip loaded optical waveguide, a slab layer having a first optical refractive index and a first width measured in a lateral direction perpendicular to the direction of light propagation through the multi-strip loaded optical waveguide; a plurality of strips disposed in a multi-strip layer above the slab layer, each of the plurality of strips having a strip width measured in the lateral direction, adjacently disposed ones of the plurality of strips being spaced apart from one another by an inter-strip distance measured in the lateral direction, each of the plurality of strips having a second optical index of refraction that is less than the first optical index of refraction of the slab layer, and a total distance spanning the plurality of strips in the lateral direction is less than the first width of the slab layer; a cladding region disposed above the slab layer, above the plurality of strips, and between adjacent ones of the plurality of strips, the cladding region having a third optical index of refraction less than the second optical index of refraction of the plurality of strips; A multi-strip loaded optical waveguide comprising:

22. 22. The multi-strip-loaded optical waveguide of claim 21, wherein the plurality of strips provide a localized increase in effective optical refractive index in the lateral direction.

23. 22. The multi-strip-loaded light guide of claim 21 , wherein the total distance spanning the plurality of strips in the lateral direction is defined to support a single optical propagation mode through the multi-strip-loaded light guide.

24. 22. The multi-strip-loaded light guide of claim 21 , wherein the total distance spanning the plurality of strips in the lateral direction is configured to support a plurality of optical propagation modes through the multi-strip-loaded light guide.

25. 22. The multi-strip loaded light guide of claim 21, wherein the total distance spanning the plurality of strips in the lateral direction is in a range from about 0.5 micrometers to about 100 micrometers.

26. 22. The multi-strip loaded optical waveguide of claim 21, wherein the strip width is in the range of about 100 nanometers to about 1000 nanometers.

27. 27. The multi-strip loaded light guide of claim 26, wherein the strip width is substantially the same for each of the plurality of strips.

28. 27. The multi-strip loaded light guide of claim 26, wherein the strip widths are different for at least two of the plurality of strips.

29. 22. The multi-strip loaded optical waveguide of claim 21, wherein the inter-strip distance is in the range of about 100 nanometers to about 1000 nanometers.

30. 30. The multi-strip loaded light guide of claim 29, wherein the inter-strip distance is substantially the same between each adjacent pair of strips in the plurality of strips.

31. 30. The multi-strip-loaded light guide of claim 29, wherein the inter-strip distance is different between at least two different adjacent pairs of strips in the plurality of strips.

32. 22. The multi-strip loaded optical waveguide of claim 21, wherein the slab layer is formed of one or more of silicon, germanium, and a silicon germanium alloy, and each of the plurality of strips is formed of one or more of silicon nitride, silicon oxynitride, and aluminum nitride.

33. 22. The multi-strip loaded optical waveguide of claim 21, wherein the cladding region is formed of silicon oxide.

34. 22. The multi-strip loaded optical waveguide of claim 21, wherein a vertical thickness of the slab layer is in a range of about 50 nanometers to about 4000 nanometers, and a vertical thickness of each of the plurality of strips is in a range of about 20 nanometers to about 2000 nanometers.

35. 22. The multi-strip loaded optical waveguide of claim 21, further comprising:

13. A multi-strip loaded optical waveguide comprising: an insulator layer, the slab layer disposed on the insulator layer, the insulator layer having a fourth optical refractive index less than the first optical refractive index of the slab layer.

36. 36. The multi-strip loaded optical waveguide of claim 35, wherein the insulator layer is formed of silicon dioxide or aluminum oxide.

37. 22. The multi-strip loaded optical waveguide of claim 21, further comprising: a middle layer disposed above the slab layer and below the plurality of strips, the middle layer having a fourth optical index of refraction less than or equal to the first optical index of refraction of the slab layer;

38. 38. The multi-strip loaded optical waveguide of claim 37, wherein the intermediate layer is formed of a dielectric material.

39. 39. The multi-strip loaded optical waveguide of claim 38, further comprising: a p-type doped region formed in a first portion of the slab layer on a first side of the plurality of strips in the lateral direction; a first metal contact structure formed through the cladding region and the intermediate layer in electrical contact with the p-type doped region; an n-type doped region formed in a second portion of the slab layer on a second side of the plurality of strips opposite the first side of the plurality of strips in the lateral direction; a second metal contact structure formed through the cladding region and the intermediate layer in electrical contact with the n-type doped region; A multi-strip loaded optical waveguide comprising:

40. 40. The multi-strip loaded optical waveguide of claim 39, wherein the first metal contact structure and the second metal contact structure are electrically connected to apply a potential difference across a portion of the slab layer extending between the p-type doped region and the n-type doped region.

41. 40. The multi-strip-loaded optical waveguide of claim 39, wherein the p-type doped region is a first p-type doped region configured to extend along a length of the multi-strip-loaded optical waveguide measured in a direction of light propagation through the multi-strip-loaded optical waveguide, and the n-type doped region is a first n-type doped region configured to extend along the length of the multi-strip-loaded optical waveguide measured in the direction of light propagation through the multi-strip-loaded optical waveguide; The multi-strip loaded optical waveguide further comprises: a series of p-type doped regions formed within the slab layer, each p-type doped region of the series of p-type doped regions extending in the lateral direction beneath the plurality of strips from the first p-type doped region toward the first n-type doped region, adjacent p-type doped regions within the series of p-type doped regions being spaced apart from one another in the direction of light propagation through the multi-strip loaded optical waveguide; a series of n-type doped regions formed in the slab layer, each n-type doped region of the series of n-type doped regions extending in the lateral direction beneath the plurality of strips from the first n-type doped region to the first p-type doped region, each n-type doped region of the series of n-type doped regions being disposed between a respective pair of adjacently disposed p-type doped regions of the series of p-type doped regions.

42. 42. The multi-strip loaded optical waveguide of claim 41, wherein each of the series of n-type doped regions is spaced apart from both the first p-type doped region and the series of p-type doped regions so as to form one or more PIN junction diodes.

43. 42. The multi-strip loaded optical waveguide of claim 41, wherein each of the series of p-type doped regions is spaced apart from both the first n-type doped region and the series of n-type doped regions so as to form one or more PIN junction diodes.

44. 42. The multi-strip loaded optical waveguide of claim 41, wherein each of the series of n-type doped regions abuts the first p-type doped region and one or more of the series of p-type doped regions to form one or more PN junction diodes.

45. 42. The multi-strip loaded optical waveguide of claim 41, wherein each of the series of p-type doped regions abuts the first n-type doped region and one or more of the series of n-type doped regions to form one or more PN junction diodes.

46. 1. A method for manufacturing an optical waveguide, comprising the steps of: disposing a plurality of strips on a slab layer, each of the plurality of strips having a strip width measured in a lateral direction perpendicular to a direction of light propagation through the optical waveguide, adjacent ones of the plurality of strips being spaced from one another by an inter-strip distance measured in the lateral direction, each of the plurality of strips having a second optical refractive index less than the first optical refractive index of the slab layer, a total distance spanning the plurality of strips in the lateral direction being less than a width of the slab layer measured in the lateral direction, the total distance spanning the plurality of strips in the lateral direction being set to maximize a size of the zeroth order optical mode in the slab layer below the plurality of strips without exciting higher order optical modes relative to a zeroth order optical mode; disposing a cladding layer over the slab layer, over the plurality of strips, and between adjacently disposed ones of the plurality of strips, the cladding layer having an optical index of refraction less than the optical index of refraction of the plurality of strips.

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