Multi-layer structure and method for manufacturing the same

A multi-layer structure and a method for manufacturing the multi-layer structure are provided. The multi-layer structure includes: a waveguide including one or more light coupling regions having a refractive index gradient; at least one organic material based active optical element disposed above the waveguide; wherein the one or more light coupling regions is configured to change characteristics of light propagating in the waveguide; wherein at least one of the one or more light coupling regions is configured to enhance light coupling between the waveguide and the active optical element.

TECHNICAL FIELD

Embodiments relate generally to a multi-layer structure and a method for manufacturing the multi-layer structure.

BACKGROUND

Generally, multi-layer structures are used for many various applications, e.g. implemented as sensors for physical and/or chemical and/or biological applications, etc. A conventional multi-layer structure usually includes various different components such as light sources, photo detectors, waveguides, etc.

Conventionally, inorganic materials are used for manufacturing the conventional multi-layer structures and also for manufacturing the light sources, the photo detectors and the waveguides. However, the conventional inorganic multi-layer structures may still have some limits on their performances.

SUMMARY

In an embodiment, there is provided a multi-layer structure, including a waveguide including one or more light coupling regions having a refractive index gradient; at least one organic material based active optical element disposed above the waveguide; wherein the one or more light coupling regions is configured to change characteristics of light propagating in the waveguide; wherein at least one of the one or more light coupling regions is configured to enhance light coupling between the waveguide and the active optical element.

In another embodiment, there is provided a method for manufacturing a multi-layer structure, the method including forming a waveguide including one or more light coupling regions having a refractive index gradient; forming at least one organic material based active optical element above the waveguide; wherein the one or more light coupling regions is configured to change characteristics of light propagating in the waveguide; wherein at least one of the one or more light coupling regions is configured to enhance light coupling between the waveguide and the active optical element.

DETAILED DESCRIPTION

Exemplary embodiments of a multi-layer structure, a method of manufacturing the multi-layer structure, a waveguide and a method of manufacturing the waveguide are described in detail below with reference to the accompanying figures. It will be appreciated that the exemplary embodiments described below can be modified in various aspects without changing the essence of the invention.

FIG. 1(a) shows a schematic diagram of a multi-layer structure100according to an embodiment. The multi-layer structure100may include a waveguide102, at least one light source104and at least one photo detector106. For illustration purposes, only one light source104and one photo detector106are shown inFIG. 1(a). In general, an arbitrary number of light sources104and photo detectors106may be provided monolithically integrated. By way of example, a plurality of light sources104and only one photo detector106may be provided. Alternatively, only one light source104and a plurality of photo detectors106may be provided. As another alternative embodiment, a plurality of light sources104and a plurality of photo detectors106may be provided monolithically integrated with one another. The waveguide102of the multi-layer structure100may be a planar waveguide. The waveguide102of the multi-layer structure100may include a light coupling arrangement107. The light source104and the photo detector106may be disposed above the waveguide102. The waveguide102, the light source104and the photo detector106may include organic material. The organic materials for the waveguide102may include but are not limited to Polyethylene, Polypropylene, PVC, Polystyrene, Nylon, Polyester, Acrylics, Polyurethane, Polycarbonate, epoxy-based polymers and fluorene derivative polymers. The organic materials for the light source104may include but are not limited to phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV). The organic materials for the photo detector106may include but are not limited to poly(3-hexythiophene):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C60(P3HT:PCBM), C60, ZnPC, and Pentacene. The waveguide102, the light coupling arrangement107, the light source104and the photo detector106may be monolithically integrated.

The light coupling arrangement107of the waveguide102may be substantially non-wavelength sensitive. The light coupling arrangement107may be substantially non-wavelength selective (in other words has an attenuation of the incoming optical signal that is negligible over a wide wavelength range, e.g. over the mentioned wavelength range(s)) in a wavelength range from 300 nm to 1700 nm.

To achieve non-wavelength selective light coupling, one of the methods is to generate refractive index (RI) gradient in the waveguide materials. On the basis of Snell's law (n1sin θ1=n2sin θ2, where n1and n2are the refractive index for a first layer and a second layer respectively, θ1is the incident angle and θ2is refraction angle), the refraction angle of a light ray increases, and thus bending the light ray, when the light ray passes from a layer with higher RI to another layer with lower RI. Therefore, the reflection angle for the light emitted from the light source104is changed gradually and continuously when the light passes through a region having a RI gradient. As a result, the light emitted from the light source104can be non-wavelength selectively coupled to the waveguide102. Another approach to achieve non-wavelength selective light coupling is to modify the incident angle of the light ray emitted from the light source104to the light coupling arrangement107, and/or of the light propagated in the light coupling arrangement107to the photo detector108in order to make the light ray satisfying total internal reflection, i.e. the incident angle θ1>critical angle θc. For example, this can be achieved through modifying the surface curvature of the interface between different materials having different refractive indexes, such as core and cladding materials, in the light coupling arrangement107.

The light coupling arrangement107may include one or more first light coupling module108and one or more second light coupling module110. For illustration purposes, only one first light coupling module108and one second light coupling module110are shown inFIG. 1(a). The first light coupling module108may include a region109having a refractive index gradient and the second light coupling module110may include a region111having a refractive index gradient.

In one embodiment, as shown inFIG. 1(a), the waveguide102may include one or more regions109,111having the refractive index gradient. In another embodiment, the waveguide may include at least two regions109,111having the refractive index gradient. The regions109,111may be substantially non-wavelength selective (in other words has an attenuation of the incoming optical signal that is negligible over a wide wavelength range, e.g. over the mentioned wavelength range(s)) in a wavelength range from 300 nm to 1700 nm. The regions109,111may be configured to couple light between the waveguide102and at least one optical element, e.g. the light source104or the photo detector106. The regions109,111may be configured to change characteristics of light propagating in the waveguide102. The changes in the characteristics of light propagating in the waveguide may include but are not limited to changes in light propagation direction, convergence of light, focusing of light, diffraction of light, divergence of light and diffusion of light. Each region109,111having the refractive index gradient may be disposed below the respective optical element, e.g. the light source104or the photo detector106. The waveguide may include but is not limited to organic material. The organic materials for the waveguide102may include but are not limited to Polyethylene, Polypropylene, PVC, Polystyrene, Nylon, Polyester, Acrylics, Polyurethane, Polycarbonate, epoxy-based polymers and fluorene derivative polymers. The regions109,111may include but are not limited to polymer, electro-opto organic materials and thermal-opto organic materials.

FIG. 9shows a flowchart900of a process of manufacturing the waveguide102. At902, one or more regions having a refractive index gradient may be formed. At904, a refractive index gradient of the one or more regions of the waveguide may be tuned.

The refractive index gradient of the regions109,111of the waveguide102may be tuned by emitting laser light to the waveguide102, e.g. by laser direct writing of the waveguide102. The refractive index (RI) of the waveguide materials may decrease after the waveguide materials are exposed to laser. A decrease of the refractive index of the waveguide materials may be proportional to the exposed energy dosage. A refractive index gradient can thus be generated by changing the exposed energy dosage from one direction to another direction along the regions109,111of the waveguide102, for example, from left to right or from bottom to top.

FIG. 10shows an example design of the refractive index gradient1000of the waveguide102. The refractive index1002of the region109of the first light coupling module108may decrease from top to bottom. The refractive index1004of the region111of the second light coupling module110may decrease from left to right. Other designs of the refractive index gradient can also be used in other embodiments.

Further, the refractive index gradient of the regions109,111may be tuned by distributing different amounts of e.g. metal ions or nanoparticles along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by changing a degree of e.g. polymer cross-linking along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by changing molecular bonding of e.g. polymer along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by generating an electric field across e.g. electro-opto materials along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by generating a temperature gradient across e.g. thermal-opto materials along the regions109,111.

Referring back toFIG. 1(a), the light source104and the photo detector106may be disposed above a first surface112of the waveguide102. The light source104and the photo detector106may be located at a distance from each other. In one embodiment, as shown inFIG. 1(a), the light source104may be disposed adjacent to the photo detector106. The light source104may be disposed above the first light coupling module108and the photo detector106may be disposed above the second light coupling module110. Further, the light source104and the photo detector106may also be arranged orthogonally to the waveguide102.

In another embodiment, as shown inFIG. 1(b), the light source104may be disposed adjacent to a further light source104. The photo detector106may be disposed adjacent to the further light source104. Each first light coupling module108may be disposed below the respective light source104. The second light coupling module110may be disposed below the photo detector106.

In another embodiment, as shown inFIG. 1(c), the light source104may be disposed adjacent the photo detector106. The photo detector106may be disposed adjacent to a further photo detector106. The first light coupling module108may be disposed below the light source104. Each second light coupling module110may be disposed below the respective photo detector106.

The waveguide102of the multi-layer structure100may have a core layer114having a first surface116facing the light source104and the photo detector106, and a second surface118facing away from the light source104and the photo detector106. The waveguide102may have a first cladding layer120disposed on the second surface118of the core layer114. The waveguide102may further include a second cladding layer122disposed on the first surface116of the core layer114. In other words, the waveguide102may have a multilayer structure. The core layer114, the first cladding layer120and the second cladding layer122may have a same size.

The core layer114, the first cladding layer120and the second cladding layer122may include but are not limited to polymer materials such as e.g. Polyethylene, Polypropylene, PVC, Polystyrene, Nylon, Polyester, Acrylics, Polyurethane, Polycarbonate, epoxy-based polymers and fluorene derivative polymers. The core layer114may have a larger refractive index than the first cladding layer120. The core layer114may have a larger refractive index than the second cladding layer122.

The first light coupling module108, including the region109having the refractive index gradient, of the light coupling arrangement107may be configured to couple the light source104to the waveguide102. The first light coupling module108, including the region109having the refractive index gradient, may be configured to direct light emitted from the light source104to the waveguide102. The first light coupling module108, including the region109having the refractive index gradient, may also be configured to change an incident angle of the light emitted from the light source104to be larger than a critical angle for effecting total internal reflection in the core layer114of the waveguide102.

In one embodiment, the first light coupling module108may include one or more of a grating coupler, a mirror and a lens. In another embodiment, the first light coupling module108may be a planar optical structure. The planar optical structure may include one or more structures such as lens made by metamaterials, photonic crystals and nanophotonics. In yet another embodiment, the first light coupling module108may be a three dimensional optical structure. The three dimensional optical structure may include one or more of a 45° mirror, a micro cavity, a volume grating, holographic optics and nanophotonics. The first light coupling module108may include one or more polymer materials, electro-opto organic materials, thermal-opto organic materials, metal oxides and metals.

The second light coupling module110, including the region111having the refractive index gradient, of the light coupling arrangement107may be configured to couple the photo detector106to the waveguide102. The second light coupling module110, including the region111having the refractive index gradient, may be configured to direct light from the core layer112of the waveguide102to the photo detector106.

In one embodiment, the second light coupling module110may include one or more of a grating coupler, a mirror and a lens. In another embodiment, the second light coupling module110may be a planar optical structure. The planar optical structure may include one or more structures such as lens made by metamaterials, photonic crystals and nanophotonics. In yet another embodiment, the second light coupling module110may be a three dimensional optical structure. The three dimensional optical structure may include one or more of a 45° mirror, a micro cavity, a volume grating, holographic optics and nanophotonics. The second light coupling module110may include one or more polymer materials, electro-opto organic materials, thermal-opto organic materials, metal oxides and metals.

In one embodiment, the first coupling module108and the second coupling module110may have the same structures. In another embodiment, the first coupling module108and the second coupling module110may have different structures.

The multi-layer structure100may further include a stacked layer124disposed on the first surface112of the waveguide102. The stacked layer124may cover the first surface112of the waveguide102. The stacked layer124may include one or more of a barrier layer, an adhesion layer and a spacer. The multi-layer structure100may also include a substrate126disposed on a second surface128of the waveguide102facing away from the light source104and the photo detector106. The stacked layer124may be formed to prevent damage to the waveguide102when forming the light source104and the photo detector106.

FIG. 1(d) shows a schematic diagram of another embodiment of the multi-layer structure100ofFIG. 1(a). In this embodiment, the stacked layer124may be disposed between the light source104and the first light coupling module108. The stacked layer124may be formed to prevent damage to the waveguide102when forming the light source104. A further stacked layer130may be disposed on the first surface112of the waveguide102. The further stacked layer130may be disposed between the photo detector106and the second light coupling module110. The further stacked layer130may include one or more of a barrier layer, an adhesion layer and a spacer. The further stacked layer130may be formed to prevent damage to the waveguide102when forming the photo detector106. As shown inFIG. 1(b), the stacked layer124and the further stacked layer130are located at a distance from one another (e.g. at two opposite ends of the waveguide102).

FIG. 1(e) shows a schematic diagram of another embodiment of the multi-layer structure100ofFIG. 1(a).FIG. 1(f) shows a schematic diagram of another embodiment of the multi-layer structure100ofFIG. 1(d). In this embodiment the core layer114may have a smaller size than the first cladding layer120and the second cladding layer122. The core layer114may have a shorter length and/or width as compared to the first cladding layer120and the second cladding layer122. Further, the core layer114may have a same thickness as the first cladding layer120and the second cladding layer122in one embodiment. In another embodiment, the core layer114may have a different thickness as compared to the first cladding layer120and the second cladding layer122. The second cladding layer122may cover the core layer114. In other words, the core layer114may be enclosed by the first cladding layer120(from the bottom side) and the second cladding layer122(from the lateral sides and the top side).

In another embodiment, as shown inFIGS. 1(g) and1(h), the core layer114may be enclosed by the first cladding layer120(from the bottom side and the lateral sides) and the second cladding layer122(from the top side).

The multi-layer structure100as described above may be an organic material based monolithically integrated optical board. The multi-layer structure100may be implemented for one or more of sensing, communication and data processing applications. The multi-layer structure100may be implemented for one or more of amplitude modulation detection, resonant frequency shift, frequency modulation detection, phase shifting modulation detection and polarization modulation detection. In one embodiment, the multi-layer structure100implemented for the various applications may have the same structures, materials, etc.

In some embodiments of the multi-layer structure100, the stacked layer124and/or the further stacked layer130may not be included. In some embodiments of the multi-layer structure100, the substrate126may not be included. In some embodiments of the multi-layer structure100, the second cladding layer122may not be included. The second cladding layer122may not be included if the medium (e.g. ambient air) surrounding the core layer114has a lower refractive index than the core layer114.

FIG. 2shows a schematic diagram of the light source104of the multi-layer structure100according to an embodiment. The light source104may be an organic light emitting diode or an organic laser. The light source104may include a transparent conductive electrode202disposed above the first surface112of the waveguide102, in particular e.g. disposed on the upper surface of the stacked layer124or the upper surface of the second cladding layer122or the upper surface of the core layer114, depending on the respective structure that is provided. The transparent conductive electrode202may have a thickness of about 120 nm. The transparent conductive electrode202may also have a thickness ranging from about 50 nm to about 1 μm. A layer of transparent conductive polymer204may be disposed on the transparent conductive electrode202. The layer of transparent conductive polymer204may have a thickness of about 80 nm. A light emissive layer206may be disposed on the layer of transparent conductive polymer204. The light emissive layer206may have a thickness of about 80 nm. The light emissive layer206may also have a thickness ranging from about 3 nm to about 300 nm. A layer of hole blocking or electron injection material208may be disposed on the light emissive layer206. The layer of hole blocking or electron injection material208may have a thickness of about 1.5 nm. A layer of cathode interface material210may be disposed on the layer of hole blocking or electron injection material layer208. The layer of cathode interface material210may have a thickness of about 5 nm. An electrical conductive electrode212may be disposed on the layer of cathode interface material210. The electrical conductive electrode212may have a thickness of about 300 nm.

The transparent conductive electrode202of the light source104may include but is not limited to transparent conductive oxide. The transparent conductive electrode202may also include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent for the light emitted from the light source104. The light emissive layer206of the light source104may include one or more organic materials. The one or more organic materials of the light emissive layer206may include but are not limited to organic dye molecules and polymers. The light emissive layer206may include but is not limited to phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV). The electrical conductive electrode212of the light source104may include but is not limited to cathode metal.

FIG. 3shows a schematic diagram of the photo detector106of the multi-layer structure100according to an embodiment. The photo detector106may be an organic photovoltaic cell. The photo detector106may include a transparent conductive electrode302disposed above the first surface112of the waveguide102, in particular e.g. disposed on the upper surface of the stacked layer124or upper surface of the further stacked layer130, the upper surface of the second cladding layer122or the upper surface of the core layer114, depending on the respective structure that is provided. The transparent conductive electrode302may have a thickness of about 120 nm. A layer of transparent conductive polymer304may be disposed on the transparent conductive electrode302. The layer of transparent conductive polymer304may have a thickness of about 40 nm. A photovoltaic layer306may be disposed on the layer of transparent conductive polymer304. The photovoltaic layer306may have a thickness of about 80 nm. The photovoltaic layer306may also have a thickness ranging from about 3 nm to about 300 nm. A layer of cathode interface material308may be disposed on the photovoltaic layer306. The layer of cathode interface material308may have a thickness of about 5 nm. An electrical conductive electrode310may be disposed on the layer of cathode interface material308. The electrical conductive electrode310may have a thickness of about 300 nm.

The transparent conductive electrode302of the photo detector106may include but is not limited to transparent conductive oxide. The transparent conductive electrode302may also include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent for the light propagated in the waveguide102. The photovoltaic layer306of the photo detector106may include one or more organic materials. The one or more organic materials of the photovoltaic layer306may include but are not limited to organic dye molecules and polymers. The photovoltaic layer306may also include but is not limited to poly(3-hexythiophene):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C60(P3HT:PCBM), C60, ZnPC, and Pentacene. Further, the photovoltaic layer306may be a multilayer structure including e.g. ZnPC/C60, Pentacene/ZnPC/Pentacene/C60, forming multiple heterojunction cells. The electrical conductive electrode310of the photo detector106may include but is not limited to cathode metal.

FIG. 4shows a flowchart400of a process of manufacturing the multi-layer structure100according to an embodiment. At402, a waveguide may be formed on a substrate. At404, a light coupling arrangement may be formed in/on the waveguide. At406, a light source may be formed above the waveguide. At408, a photo detector may be formed above the waveguide. In another embodiment, the photo detector may be formed above the waveguide at406and the light source may be formed above the waveguide at408.

FIG. 5shows a process of manufacturing the multi-layer structure100ofFIG. 1(e) according to an embodiment. The multi-layer structure100may be manufactured in a batch manner or in a roll-to-roll continuous manner.

FIG. 5(a) shows a substrate126. The substrate126may include but is not limited to silicon, glass, stainless steel foil, and plastics. The substrate126may be a multilayer substrate.

FIG. 5(b) shows a first cladding layer120of a waveguide102formed on the substrate126. The first cladding layer120may be formed by coating or printing the first cladding layer120, soft baking the first cladding layer120, exposing the first cladding layer120to ultraviolet light, and curing the first cladding layer120. The first cladding layer120may have a thickness of about 5 μm. The first cladding layer120may include but is not limited to epoxy-based polymer.

FIG. 5(c) shows a core layer114formed on the first cladding layer120. The core layer114may be formed by coating or printing the core layer114, soft baking the core layer114, exposing the core layer114to ultraviolet light, and curing the core layer114. The core layer114may have a thickness of about 5 μm. The core layer114may include but is not limited to epoxy-based polymer.

FIG. 5(d) shows that the core layer114is etched, e.g. using a lithographic process and a corresponding patterning process. The core layer114may have a smaller size than the first cladding layer120. The core layer114may have a shorter length and/or width than the first cladding layer120. For example, the first cladding layer120may have a width ranging from about 4 mm to about 10 mm and a length ranging from about 10 mm to about 30 mm, while the core layer114may have a width of about 5 μm and a length ranging from about 5 mm to about 20 mm. Further, the core layer114may have a same thickness as the first cladding layer120in one embodiment. For example, the core layer114may have a thickness of about 5 μm and the first cladding layer may have a thickness of about 5 μm. In another embodiment, the core layer114may have a different thickness as compared to the first cladding layer120.

FIG. 5(e) shows a second cladding layer122formed on the core layer114. The second cladding layer122may be formed by coating or printing the second cladding layer122, soft baking the second cladding layer122, exposing the second cladding layer122to ultraviolet light, and curing the second cladding layer122. The second cladding layer122may have a depth of about 5 μm for covering the core layer114. The second cladding layer122may include but is not limited to epoxy-based polymer. The core layer114may have a smaller size than the second cladding layer122. The core layer114may have a shorter length and/or width than the second cladding layer122. For example, the second cladding layer114may have a width ranging from about 4 mm to 10 mm and a length ranging from about 10 mm to about 30 mm, while the core layer114may have a width of about 5 μm and a length ranging from about 5 mm to about 20 mm. Further, the core layer114may have a same thickness as the depth of the second cladding layer122in one embodiment. For example, the core layer114may have a thickness of about 5 μm and the second cladding layer may have a depth of about 5 μm. In another embodiment, the core layer114may have a different thickness as compared to the depth of the second cladding layer122. The second cladding layer122may cover the core layer114. In other words, the core layer114may be enclosed by the first cladding layer120(from the bottom side) and the second cladding layer122(from the lateral sides and the top side).

The core layer114, the first cladding layer120and the second cladding layer122form the waveguide102. The core layer114, the first cladding layer120and the second cladding layer122of the waveguide102may also include but are not limited to polymer materials such as e.g. Polyethylene, Polypropylene, PVC, Polystyrene, Nylon, Polyester, Acrylics, Polyurethane, Polycarbonate, epoxy-based polymer and fluorene derivative polymer.

FIG. 5(f) shows forming one or more regions109,111having a refractive index gradient on portions of the waveguide102. A refractive index gradient of the waveguide102may be tuned to form a light coupling arrangement107in the waveguide102, as shown inFIG. 5(g). The light coupling arrangement107may be substantially non-wavelength selective (in other words has an attenuation of the incoming optical signal that is negligible over a wide wavelength range, e.g. over the mentioned wavelength range(s)) in a wavelength range from 300 nm to 1700 nm.

As described above, to achieve non-wavelength selective light coupling, one of the methods is to generate refractive index (RI) gradient in the waveguide materials. On the basis of Snell's law (n1sin θ1=n2sin θ2, where n1and n2are the refractive index for a first layer and a second layer respectively, θ1is the incident angle and θ2is refraction angle), the refraction angle of a light ray increases, and thus bending the light ray, when the light ray passes from a layer with higher RI to another layer with lower RI. Therefore, the reflection angle for the light emitted from the light source104is changed gradually and continuously when the light passes through a region having a RI gradient. As a result, the light emitted from the light source104can be non-wavelength selectively coupled to the waveguide102. Another approach to achieve non-wavelength selective light coupling is to modify the incident angle of the light ray emitted from the light source104to the light coupling arrangement107, and/or of the light propagated in the light coupling arrangement107to the photo detector108in order to make the light ray satisfying total internal reflection, i.e. the incident angle θ1>critical angle θc. For example, this can be achieved through modifying the surface curvature of the interface between different materials having different refractive indexes, such as core and cladding materials, in the light coupling arrangement107.

The refractive index gradient of the regions109,111of the waveguide102may be tuned by emitting laser light to the waveguide102, e.g. by laser direct writing of the waveguide102. The refractive index (RI) of the waveguide materials may decrease after the waveguide materials are exposed to laser. A decrease of the refractive index of the waveguide materials may be proportional to the exposed energy dosage. A refractive index gradient can thus be generated by changing the exposed energy dosage from one direction to another direction along the regions109,111of the waveguide102, for example, from left to right or from bottom to top.

Further, the refractive index gradient of the regions109,111may be tuned by distributing different amounts of e.g. metal ions or nanoparticles along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by changing a degree of e.g. polymer cross-linking along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by changing molecular bonding of e.g. polymer along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by generating an electric field across e.g. electro-opto materials along the regions109,111. The refractive index gradient of the regions109,111may also be tuned by generating a temperature gradient across e.g. thermal-opto materials along the regions109,111.

As shown inFIG. 5(g), the light coupling arrangement107may include one or more first light coupling module108and one or more second light coupling module110. For illustration purposes, only one first light coupling module108and one second light coupling module110are shown inFIG. 1(a). The first light coupling module108may include a region109having a refractive index gradient and the second light coupling module110may include a region111having a refractive index gradient.

In one embodiment, the waveguide102may include one or more regions109,111having the refractive index gradient. In another embodiment, the waveguide may include at least two regions109,111having the refractive index gradient. The regions109,111may be substantially non-wavelength selective (in other words has an attenuation of the incoming optical signal that is negligible over a wide wavelength range, e.g. over the mentioned wavelength range(s)) in a wavelength range from 300 nm to 1700 nm. The regions109,111may be configured to couple light between the waveguide102and at least one optical element, e.g. the light source104or the photo detector106. The regions109,111may be configured to change characteristics of light propagating in the waveguide102. The changes in the characteristics of light propagating in the waveguide may include but are not limited to changes in light propagation direction, convergence of light, focusing of light, diffraction of light, divergence of light and diffusion of light. Each region109,111having the refractive index gradient may be disposed below the respective optical element, e.g. the light source104or the photo detector106. The waveguide may include but is not limited to organic material. The organic materials for the waveguide102may include but are not limited to Polyethylene, Polypropylene, PVC, Polystyrene, Nylon, Polyester, Acrylics, Polyurethane, Polycarbonate, epoxy-based polymers and fluorene derivative polymers. The regions109,111may include but are not limited to polymer, electro-opto organic materials and thermal-opto organic materials.

The first light coupling module108and the second light coupling module110may be located at a distance from each other (e.g. may be formed at two opposite ends of the waveguide102) so that the light emitted by the light source104may be received by the first light coupling module108(including the region109having the refractive index gradient) and input into an input side of the waveguide102(which is optically coupled with the first light coupling module108), which in turn transmits the input light to an output side of the waveguide102, which is optically coupled with the second light coupling module110(including the region111having the refractive index gradient). The second light coupling module110, including the region109having the refractive index gradient, may receive the light from the waveguide102and transmit it to the photo detector106, which will be described in more detail below.

FIG. 5(h) shows a stacked layer124deposited on a first surface112of the waveguide102. The stacked layer124may cover the first surface112of the waveguide102. The stacked layer124may include one or more of a barrier layer, an adhesion layer and a spacer. The stacked layer124may be formed to prevent damage to the waveguide102when forming the light source104and the photo detector106. The stacked layer124may have a thickness ranging from about 10 nm to about 1 mm. The stacked layer124may include but is not limited to silicon dioxide, silicon nitride, silicon oxynitride, silicon carbide, quartz, transparent metal oxide, transparent polymer such as polyethylene terephthalate (PET), Su-8, polydimethylsioxane (PDMS) on a condition that these materials are transparent to the light emitted from the light source104.

FIG. 5(i) shows a light source104and a photo detector106formed above the waveguide102. For illustration purposes, only one light source104and one photo detector106are shown. More than one light source104and more than one photo detector106can be formed above the waveguide102. The light source104, the photo detector106and the waveguide102may include but are not limited to organic material. The waveguide102, the light coupling arrangement107, the light source104and the photo detector106may be monolithically integrated. The light source104and the photo detector106may be disposed above the first surface112of the waveguide102. The light source104may be disposed above the first light coupling module108(including the region109having the refractive index gradient) and the photo detector106may be disposed above the second light coupling module110(including the region111having the refractive index gradient). The light source104and the photo detector106may also be arranged orthogonally to the waveguide102.

The light source104and the photo detector106may be manufactured using any of several different processes. Details of three such processes are described below.

FIG. 6shows a first process of manufacturing the light source104and the photo detector106according to an embodiment. In a first process, the light source104may be formed before the photo detector106.

FIG. 6(a) shows a structure600of the substrate126, the waveguide102and the stacked layer124.FIG. 6(b) shows a transparent conductive electrode202of the light source104deposited above the first surface112of the waveguide102(e.g. on the stacked layer124). The transparent conductive electrode202of the light source104may have a thickness of about 120 nm. The transparent conductive electrode202may have a thickness ranging from about 50 nm to about 1 μm. The transparent conductive electrode202of the light source104may include but is not limited to transparent conductive oxide. The transparent conductive electrode202may also include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent for the light emitted from the light source104.

FIG. 6(c) shows a first layer602formed on the transparent conductive electrode202of the light source104. The first layer602may be formed by one or more of coating, printing, inkjet printing and/or physical deposition. The first layer602may also be cured. The first layer602may have a stack of materials. The stack of materials of the first layer602may include one or more of light emissive material206, transparent conductive polymer204, hole blocking or electron injection material208, and/or cathode interface material210. The layer of transparent conductive polymer204may have a thickness of about 80 nm. The layer of transparent conductive polymer204may include but is not limited to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). The light emissive layer206may have a thickness of about 80 nm. The light emissive layer206may also have a thickness ranging from about 3 nm to about 300 nm. The light emissive material206may include one or more organic materials. The one or more organic materials of the light emissive material206may include but are not limited to organic dye molecules and polymers. The light emissive layer206may include but is not limited to phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV). The layer of hole blocking or electron injection material208may have a thickness of about 1.5 nm. The layer of hole blocking or electron injection material208may include but is not limited to lithium fluoride. The layer of cathode interface material210may have a thickness of about 5 nm. The layer of cathode interface material210may include but is not limited to calcium.

FIG. 6(d) shows an electrical conductive electrode212deposited on the first layer602. The electrical conductive electrode212may have a thickness of about 300 nm. The electrical conductive electrode212may include but is not limited to cathode metal. The electrical conductive electrode212may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide. The transparent conductive electrode202, the first layer602and the electrical conductive electrode212may form the light source104.

During the processes described above and shown inFIGS. 6(a) to6(d), a surface portion603of the stack layer124, in which the photo detector106should be formed, may be masked so that the deposition of any material provided for the formation of the light source102may be prevented therein.

FIG. 6(e) shows a transparent conductive electrode302of the photo detector106deposited above the first surface112of the waveguide102(e.g. on the stacked layer124). The transparent conductive electrode302of the photo detector106may have a thickness of about 120 nm. The transparent conductive electrode302may include but is not limited to transparent conductive oxide. The transparent conductive electrode302may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent to the light propagated in the waveguide102.

FIG. 6(f) shows a second layer604formed on the transparent conductive electrode302of the photo detector106. The second layer604of the photo detector106may be formed by one or more of coating, printing, inkjet printing and/or physical deposition. The second layer604may also be cured. The second layer604may have a stack of materials. The stack of materials of the second layer604may include one or more of photovoltaic material306, transparent conductive polymer304and/or cathode interface material308. The layer of transparent conductive polymer304may have a thickness of about 40 nm. The layer of transparent conductive polymer304may include but is not limited to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). The photovoltaic layer306may have a thickness of about 80 nm. The photovoltaic layer306may also have a thickness ranging from about 3 nm to about 300 nm. The photovoltaic material306may include one or more organic materials. The one or more organic materials of the photovoltaic material306may include but are not limited to organic dye molecules and polymers. The photovoltaic layer306may include but is not limited to poly(3-hexythiophene):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C60(P3HT:PCBM), C60, ZnPC, and Pentacene. Further, the photovoltaic layer306may be a multilayer structure including but not limiting to e.g. ZnPC/C60, Pentacene/ZnPC/Pentacene/C60, forming multiple heterojunction cells. The layer of cathode interface material308may have a thickness of about 5 nm. The layer of cathode interface material308may but is not limited to calcium.

FIG. 6(g) shows an electrical conductive electrode310deposited on the second layer604of the photo detector106. The electrical conductive electrode310may have a thickness of about 300 nm. The electrical conductive electrode310of the photo detector106may include but is not limited to cathode metal. The electrical conductive electrode310may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide. The transparent conductive electrode302, the second layer604and the electrical conductive electrode310may form the photo detector106.

During the processes described above and shown inFIGS. 6(e) to6(g), a surface portion605of the stack layer124, in which the light source102has been formed, and an upper surface606of the light source104may be masked so that the deposition of any material provided for the formation of the photo detector106may be prevented therein.

FIG. 7shows a second process of manufacturing the light source104and the photo detector106according to an embodiment. In the second process, a transparent conductive electrode202of the light source104and a transparent conductive electrode302of the photo detector106may be deposited above the first surface108of the waveguide102simultaneously.

FIG. 7(a) shows a structure700of the substrate126, the waveguide102and the stacked layer124.FIG. 7(b) shows a transparent conductive electrode202of the light source104and a transparent conductive electrode302of the photo detector106deposited above the first surface108of the waveguide102(e.g. on the stacked layer124) simultaneously. The transparent conductive electrode202of the light source104may have a thickness of about 120 nm. The transparent conductive electrode202may have a thickness ranging from about 50 nm to about 1 μm. The transparent conductive electrode202of the light source104may include but is not limited to transparent conductive oxide. The transparent conductive electrode202may also include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent for the light emitted from the light source104. The transparent conductive electrode302of the photo detector106may have a thickness of about 120 nm. The transparent conductive electrode302may include but is not limited to transparent conductive oxide. The transparent conductive electrode302may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent to the light propagated in the waveguide102.

FIG. 7(c) shows a first layer702formed on the transparent conductive electrode202of the light source104. The first layer702may be formed by one or more of coating, printing, inkjet printing and/or physical deposition. The first layer702may also be cured. The first layer702may have a stack of materials. The stack of materials of the first layer702may include one or more of light emissive material206, transparent conductive polymer204, hole blocking or electron injection material208, and/or cathode interface material210. The layer of transparent conductive polymer204may have a thickness of about 80 nm. The layer of transparent conductive polymer204may include but is not limited to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). The light emissive layer206may have a thickness of about 80 nm. The light emissive layer206may also have a thickness ranging from about 3 nm to about 300 nm. The light emissive material206may include one or more organic materials. The one or more organic materials of the light emissive material206may include but are not limited to organic dye molecules and polymers. The light emissive layer206may include but is not limited to phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV). The layer of hole blocking or electron injection material208may have a thickness of about 1.5 nm. The layer of hole blocking or electron injection material208may include but is not limited to lithium fluoride. The layer of cathode interface material210may have a thickness of about 5 nm. The layer of cathode interface material210may include but is not limited to calcium. An upper surface703of the transparent conductive electrode302of the photo detector106may remain exposed, in other words, the upper surface703of the transparent conductive electrode302may be masked during the formation of the first layer702of the light source104.

FIG. 7(d) shows an electrical conductive electrode212deposited on the first layer702of the light source104. The electrical conductive electrode212may have a thickness of about 300 nm. The electrical conductive electrode212of the light source104may include but is not limited to cathode metal. The electrical conductive electrode212may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide. The transparent conductive electrode202, the first layer702and the electrical conductive electrode212may form the light source104. The upper surface703of the transparent conductive electrode302of the photo detector106may remain exposed, in other words, the upper surface703of the transparent conductive electrode302may be masked during the formation of the electrical conductive electrode212of the light source104. Thus, with the end of this process, the light source104is completed.

FIG. 7(e) shows a second layer704formed on the transparent conductive electrode302of the photo detector106. The second layer704of the photo detector106may be formed by one or more of coating, printing, inkjet printing and/or physical deposition. The second layer704may also be cured. The second layer704may have a stack of materials. The stack of materials of the second layer704may include one or more of photovoltaic material306, transparent conductive polymer304and/or cathode interface material308. The layer of transparent conductive polymer304may have a thickness of about 40 nm. The layer of transparent conductive polymer304may include but is not limited to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). The photovoltaic layer306may have a thickness of about 80 nm. The photovoltaic layer306may also have a thickness ranging from about 3 nm to about 300 nm. The photovoltaic material306may include one or more organic materials. The one or more organic materials of the photovoltaic material306may include but are not limited to organic dye molecules and polymers. The photovoltaic layer306may include but is not limited to poly(3-hexythiophene):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C60(P3HT:PCBM), C60, ZnPC, and Pentacene. Further, the photovoltaic layer306may be a multilayer structure including but not limiting to e.g. ZnPC/C60, Pentacene/ZnPC/Pentacene/C60, forming multiple heterojunction cells. The layer of cathode interface material308may have a thickness of about 5 nm. The layer of cathode interface material308may but is not limited to calcium. An upper surface705of the light source104just completed may remain exposed, in other words, the upper surface705of the light source104may be masked during the formation of the second layer704of the photo detector106.

FIG. 7(f) shows an electrical conductive electrode310deposited on the second layer704of the photo detector106. The electrical conductive electrode310may have a thickness of about 300 nm. The electrical conductive electrode310of the photo detector106may include but is not limited to cathode metal. The electrical conductive electrode310may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide. The transparent conductive electrode302, the second layer704and the electrical conductive electrode310may form the photo detector106. The upper surface705of the light source104may remain exposed, in other words, the upper surface705of the light source104may be masked during the formation of the electrical conductive electrode310of the photo detector106.

FIG. 8shows a third process of manufacturing the light source104and the photo detector106according to an embodiment. In the third process, the light source104and the photo detector106may be formed simultaneously.

FIG. 8(a) shows a structure800of the substrate126, the waveguide102and the stacked layer124.FIG. 8(b) shows a transparent conductive electrode202of the light source104and a transparent conductive electrode302of the photo detector106deposited above the first surface108of the waveguide102(e.g. on the stacked layer124) simultaneously. The transparent conductive electrode202of the light source104may have a thickness of about 120 nm. The transparent conductive electrode202may have a thickness ranging from about 50 nm to about 1 μm. The transparent conductive electrode202of the light source104may include but is not limited to transparent conductive oxide. The transparent conductive electrode202may also include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent for the light emitted from the light source104. The transparent conductive electrode302of the photo detector106may have a thickness of about 120 nm. The transparent conductive electrode302may include but is not limited to transparent conductive oxide. The transparent conductive electrode302may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide on a condition that these materials are transparent to the light propagated in the waveguide102.

FIG. 8(c) shows a first layer802formed on the transparent conductive electrode202of the light source104. The first layer802of the light source104may be formed by one or more of coating, printing, inkjet printing and/or physical deposition. The first layer802may also be cured. The first layer802may have a stack of materials. The stack of materials of the first layer802may include one or more of light emissive material206, transparent conductive polymer204, hole blocking or electron injection material208, and/or cathode interface material210. The layer of transparent conductive polymer204may have a thickness of about 80 nm. The layer of transparent conductive polymer204may include but is not limited to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). The light emissive layer206may have a thickness of about 80 nm. The light emissive layer206may also have a thickness ranging from about 3 nm to about 300 nm. The light emissive material206may include one or more organic materials. The one or more organic materials of the light emissive material206may include but are not limited to organic dye molecules and polymers. The light emissive layer206may include but is not limited to phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV). The layer of hole blocking or electron injection material208may have a thickness of about 1.5 nm. The layer of hole blocking or electron injection material208may include but is not limited to lithium fluoride. The layer of cathode interface material210may have a thickness of about 5 nm. The layer of cathode interface material210may include but is not limited to calcium. An upper surface803of the transparent conductive electrode302of the photo detector106may remain exposed, in other words, the upper surface803of the transparent conductive electrode302may be masked during the formation of the first layer802of the light source104.

FIG. 8(d) shows a second layer804formed on the transparent conductive electrode302of the photo detector106. The second layer804of the photo detector106may be formed by one or more of coating, printing, inkjet printing and/or physical deposition. The second layer804may also be cured. The second layer804may have a stack of materials. The stack of materials of the second layer804may include one or more of photovoltaic material306, transparent conductive polymer304and/or cathode interface material308. The layer of transparent conductive polymer304may have a thickness of about 40 nm. The layer of transparent conductive polymer304may include but is not limited to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS). The photovoltaic layer306may have a thickness of about 80 nm. The photovoltaic layer306may also have a thickness ranging from about 3 nm to about 300 nm. The photovoltaic material306may include one or more organic materials. The one or more organic materials of the photovoltaic material306may include but are not limited to organic dye molecules and polymers. The photovoltaic layer306may include but is not limited to poly(3-hexythiophene):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C60(P3HT:PCBM), C60, ZnPC, and Pentacene. Further, the photovoltaic layer306may be a multilayer structure including but not limiting to e.g. ZnPC/C60, Pentacene/ZnPC/Pentacene/C60, forming multiple heterojunction cells. The layer of cathode interface material308may have a thickness of about 5 nm. The layer of cathode interface material308may but is not limited to calcium. An upper surface805of the first layer802of the light source104may remain exposed, in other words, the upper surface805of the first layer802may be masked during the formation of the second layer804of the photo detector106.

FIG. 8(e) shows an electrical conductive electrode212deposited on the first layer802of the light source104and an electrical conductive electrode310deposited on the second layer804of the photo detector106simultaneously. The electrical conductive electrode212of the light source104may have a thickness of about 300 nm. The electrical conductive electrode212may, but is not limited to include cathode metal. The electrical conductive electrode212may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide. The transparent conductive electrode202, the first layer802and the electrical conductive electrode212may form the light source104. The electrical conductive electrode310of the photo detector106may have a thickness of about 300 nm. The electrical conductive electrode310may include but is not limited to cathode metal. The electrical conductive electrode310may include but is not limited to conductive metal oxide, conductive polymer and conductive metallic silicide. The transparent conductive electrode302, the second layer804and the electrical conductive electrode310may form the photo detector106.

The processes for manufacturing different embodiments of the multi-layer structure100can be modified by a skilled person from the process as described above. For example, for manufacturing the multi-layer structure100ofFIGS. 1(a) to1(c) where the core layer114, the first cladding layer120and the second cladding layer122may have a same size, the core layer114of the waveguide102may not be etched. The process may continue fromFIG. 5(c) toFIG. 5(e).

Further, for manufacturing the multi-layer structure100ofFIGS. 1(d),1(f) and1(h) where the stacked layer124may be disposed between the light source104and the first light coupling module108and a further stacked layer130may be disposed between the photo detector106and the second light coupling module110, the stacked layer124and the further stacked layer130may be deposited on the first surface112of the waveguide simultaneously inFIG. 5(h) instead.

FIG. 11(a) shows a schematic diagram of the multi-layer structure100implemented as e.g. a biosensor1100. The biosensor1100may include antibody1102on a surface1104of the stacked layer124facing away from the waveguide102.FIG. 11(b) shows a graph1106of intensity plotted against wavelength before the antibody1102interacts with antigen1108. Before the antibody1102on the biosensor1100interacts with the antigen1108, a resonance wavelength of the biosensor1100is at point1110of graph1106.

FIG. 11(c) shows a schematic diagram of the antibody1102on the surface1104interacting with the antigen1108.FIG. 11(d) shows a graph1112of intensity plotted against wavelength after the antibody1102interacts with the antigen1108. After the antibody1102on the biosensor1100interacts with the antigen1108, the resonance wavelength of the biosensor1100is at point1114of graph1112.

Comparing graph1106ofFIG. 11(b) and graph1112ofFIG. 11(d), it can be observed that the resonance wavelength of the biosensor1100increases after the antibody1102interacts with the antigen1108.