Patent Description:
Optical coupling into and out of waveguides in photonic integrated structures can have reduced efficiencies due to light leaking out of the waveguides at the edge of the structure interacting with oxides encapsulating the waveguide, as well as insulator layers between the waveguide and a substrate. The losses occur mainly due to differences in indices of refraction between the waveguide, the insulator layers and the encapsulating oxides; the losses can be particularly acute when silicon substrates are used.

<CIT>, describes a device that includes a substrate with an opening formed adjacent to an edge, a layer of insulator (e.g. an oxide material, a thermal oxide material, a nitride material, and the like) that forms a bridge across the opening and a waveguide thereupon. Optical epoxy that is indexed matched to the insulator is located in the opening. Any encapsulating insulators and/or oxides and/or nitrides on at least a tapered region of the waveguide at the edge, are replaced with optical epoxy using, for example, etching techniques to remove the encapsulating insulators. The thicknesses of the optical epoxies are selected to contain optical signals leaking from the waveguide in the tapered region. Replacing the substrate and the encapsulating insulator adjacent to the tapered region with index matched epoxy can reduce the losses due to differences in refractive index between the insulator and the substrate, and between the insulator and the encapsulating insulator.

<CIT> discloses an apparatus that comprises an optical-mode-converter. The optical-mode-converter includes an optical waveguide including a segment directly located on a substrate and a cantilevered segment located over said substrate and separated from said substrate by a cavity. External light directly enters the optical waveguide.

<CIT> discloses an optical module that includes an under cladding, a first core, a second core, and an over cladding. The under cladding has a flat shape as a whole. The first core has a quadrangular cross section and is placed on the under cladding. The second core is placed on a terminal end portion of the first core. The over cladding is placed in a region including the terminal end portion of the first core and the second core placed on the terminal end portion of the first core. The under cladding and the first core placed thereon constitute a first optical waveguide. The under cladding, the terminal end portion of the first core placed on the under cladding, the second core placed thereon, and the over cladding placed on and around the second core constitute a mode field size conversion portion. The under cladding, the second core placed on the under cladding, and the over cladding placed on and around the second core constitute a second optical waveguide. The first core is made of silicon. The first and second cores differ in cross-sectional shape. A manufacturing method for the optical module is also disclosed. External light directly enters the optical waveguide.

<CIT> describes a semiconductor photonic device that includes a substrate, facet(s), and optical coupler(s) associated with the facet(s). Each optical coupler can couple an electromagnetic field incident on the respective facet towards a buried waveguide as the electromagnetic field proceeds into the semiconductor photonic device. A fiber is centered on the optical waveguide.

<CIT> is another prior art photonic device disclosing a coupler with an expansion region that is optically coupled with a compression region and is configured to receive the optical beam from the compression region. The expansion region is configured to transmit the optical beam to the optical fiber.

As set forth herein, a fiber-to-SOI photonics waveguide coupler is set forth that uses a thick upper cladding to support evanescently coupling light into a sub waveguide.

An advantage of the waveguide coupler set forth herein is that it eliminates any requirement to undercut the buried oxide layer, as required for example in <CIT>, resulting in simple fabrication of the waveguide coupler.

An aspect of the present specification provides a device according to independent claim <NUM>.

An aspect of the present specification provides a method according to independent claim <NUM>.

For a better understanding of the various examples described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:.

With reference to <FIG> an optical coupler device <NUM> is depicted for transferring light to or from a single mode optical fiber <NUM> to a silicon-on-insulator (SOI) waveguide with low loss, though it is understood that any suitable semiconductor-on-insulator material is within the scope of present specifications. The device <NUM> is understood to be depicted schematically, with the view depicted representing a cross-section of the device <NUM>, for example through a plane that perpendicularly intersects the layers of the device <NUM> and the optical fiber <NUM>, and in particular perpendicularly intersects respective optical waveguides of the device <NUM> and the optical fiber <NUM>.

The device <NUM> comprises five optical semiconducting or dielectric layers: a substrate <NUM>, a first layer <NUM> of oxide material, an optical waveguide <NUM>, a second layer <NUM> of oxide material, and an index matching material <NUM>. The layers are next described.

An initial layer comprises a substrate <NUM> comprising a waveguide material having a waveguide refractive index RIWG. In some examples, the substrate <NUM> may comprise and/or be made of silicon (Si), and may colloquially be referred to as an SOI handle.

A first layer <NUM> of oxide material is "above" and/or on the substrate <NUM>. The first layer <NUM> has a first refractive index RI<NUM> lower than the waveguide refractive index RIWG. The first layer <NUM> of oxide material may comprise a layer of silicon oxide (SiO2) dielectric (e.g. buried insulator oxide). Hence, the first layer <NUM> of oxide material may comprise an oxide of the material of the substrate <NUM>. It is further understood that references to one layer (and the like) being "above" another layer, as used herein, use the substrate <NUM> as a bottom-most reference layer; for example, a layer described herein may be above another layer presuming the substrate <NUM> is a lowest and/or bottom-most layer.

An optical waveguide <NUM> is generally on the first layer <NUM> of the oxide material, the optical waveguide <NUM> comprising the waveguide material having the waveguide refractive index RIWG. Put another way, the optical waveguide <NUM> may comprise the same waveguide material as the substrate <NUM>, and hence may comprise a silicon waveguide layer. Furthermore, the optical waveguide <NUM> may be referred to as being "above" or "on" the "buried insulator oxide" of the first layer <NUM>. The optical waveguide is understood to be of a cross-sectional shape that is suitable for guiding light into and out of the device <NUM>, for example to, or from, one or more optical components (not depicted) within the device <NUM>, such as modulators or demodulators, and the like. A shape of the optical waveguide <NUM> is described in more detail below with respect to <FIG> and <FIG>. However, it is understood that the optical waveguide <NUM> is generally narrower in width than the first layer <NUM> of the optical material (e.g. in a direction into or out of the page of <FIG>).

A second layer <NUM> of the oxide material (e.g. the same optical material as the first layer <NUM>) is generally on the optical waveguide <NUM> and the first layer <NUM> of the oxide material, the second layer <NUM> of the oxide material having a second refractive index RI<NUM> higher than the first refractive index RI<NUM> and less than the waveguide refractive index RIWG. Furthermore, the second layer <NUM> may be thicker than the first layer <NUM>, and hence may be referred to as a "thick dielectric" slab waveguide layer (e.g. which may comprise a form or doped or undoped SiO<NUM>).

The first layer <NUM> of the oxide material may be referred to as an undercladding layer, as the first layer <NUM> of the oxide material is "under" the optical waveguide <NUM> (e.g. with reference to the substrate <NUM> as a base and/or lowest layer of the device <NUM>). Similarly, the second layer <NUM> of the oxide material may be referred to as an overcladding layer, as the second layer <NUM> of the oxide material is "over" and/or around the optical waveguide <NUM>. Hence, together, the layers <NUM>, <NUM> generally act as cladding layers for the optical waveguide <NUM>, similar to cladding of an optical fiber. However, as will be explained below, light may enter or exit the device <NUM> via the first layer <NUM> of the oxide material.

According to the claimed invention, the first layer <NUM> of the oxide material, the optical waveguide <NUM>, and the second layer <NUM> of the oxide material form an end face <NUM> for light coupling with the optical fiber <NUM>. Furthermore, it is understood that the optical waveguide <NUM> extends inwards from the end face <NUM> (e.g. towards the optical components at an interior of the device <NUM>) and that the optical waveguide <NUM> is increasing in effective refractive index from the end face <NUM>. Put another way, the effective refractive index is understood to be a minimum and/or smallest value adjacent the end face <NUM> (e.g. similar to the refractive index RI<NUM> of the second layer <NUM>), and increases from the end face <NUM> towards the interior of the device <NUM> and may have a maximum value of the waveguide refractive index RIWG. Such an increase in effective refractive index may be achieved via a tapered and/or modulated tapered structure described in more detail below with respect to <FIG> and <FIG>.

The index matching material <NUM> is generally on the second layer <NUM> of the oxide material, and the index matching material <NUM> encapsulates at least the second layer <NUM> of the oxide material and the end face <NUM>. Furthermore, a respective refractive index RIIM of the index matching material <NUM> is selected to be about index matched to the first refractive index RI<NUM> of the first layer <NUM> of the oxide material. The index matching material <NUM> may comprise any suitable optical epoxy selected to have a refractive index that is about index matched to the first refractive index RI<NUM> of the first layer <NUM> of the oxide material.

The index matching material <NUM> may be colloquially referred to as a super-cladding layer that encapsulates the other layers of the device <NUM> and is generally understood to further encapsulate a fiber end face <NUM> of the optical fiber <NUM>, such that the index matching material <NUM> acts as a transition optical index material between the fiber end face <NUM> of the optical fiber <NUM> and the end face <NUM> of the device <NUM>.

While the index matching material <NUM> is depicted as being between the end faces <NUM>, <NUM>, and uniformly encapsulating the second layer <NUM>, the index matching material <NUM> may not uniformly encapsulate the second layer <NUM>, but rather the index matching material <NUM> may be thickest in a region between and/or adjacent the end faces <NUM>, <NUM>, and taper off in thickness away from the region between and/or adjacent the end faces <NUM>, <NUM>. Indeed, the index matching material <NUM> may have any suitable shape and/or physical profile, as long as the index matching material <NUM> contains light travelling and/or being conveyed between the end faces <NUM>, <NUM> and further assists at containing light within the layers <NUM>, <NUM> and the optical waveguide <NUM> (e.g. without light leaking out of the index matching material <NUM> and/or the layers <NUM>, <NUM> and the optical waveguide <NUM>).

In particular, control and/or selection of the refractive indices of the layers <NUM>, <NUM>, and the optical waveguide <NUM>, along with the thickness of the layers <NUM>, <NUM>, and the optical waveguide <NUM> may assist with coupling of light into, and out of, the device <NUM>.

In general, using silicon as an example, a combination of the substrate <NUM>, the layers <NUM>, <NUM>, and the optical waveguide <NUM> may be manufactured by starting with the substrate <NUM> made of silicon, and growing the first layer <NUM> of the oxide material, such as SiO2, on the substrate <NUM> using any suitable technique (e.g. such as chemical vapor deposition (CVD), and the like). A layer of Si may be grown on the first layer <NUM> using any suitable technique, and the layer of Si may be suitably etched, and the like, to form the optical waveguide <NUM>. The second layer <NUM> of the oxide material, such as SiO2, may be grown on the optical waveguide <NUM> and the first layer <NUM> using any suitable technique (e.g. such as chemical vapor deposition (CVD), and the like); for example, as the optical waveguide <NUM> is narrower then the first layer <NUM>, the second layer <NUM> on either side of the optical waveguide <NUM> (e.g. along an optical axis and/or longitudinal axis of the optical waveguide <NUM>) is exposed and, as such, the second layer <NUM> is grown on both the optical waveguide <NUM> and the first layer <NUM>.

According to the claimed invention, the refractive index RI<NUM> of the second layer <NUM> is higher than the refractive index RI<NUM> of the first layer <NUM>.

This leads to coupling problems when light from the optical fiber <NUM> is coupled into the optical waveguide <NUM>.

For example, in general, the optical fiber <NUM> may comprise a single mode optical fiber, that comprises a cladding layer <NUM> that is cylindrically arranged around a fiber optical waveguide <NUM> through which light <NUM> is conveyed. It is understood that the refractive index RIC of the cladding layer <NUM> is less than the refractive index RIFWG of the fiber optical waveguide <NUM> such that total internal reflection contains the light <NUM> within the fiber optical waveguide <NUM>.

As depicted, the light <NUM> is being conveyed out of the fiber optical waveguide <NUM> and exits the optical fiber <NUM> at the fiber end face <NUM>. In general, in prior art optical couplers, the fiber end face <NUM> and/or the optical waveguide <NUM> would be centered on the optical waveguide <NUM> of the device <NUM> and no index matching material <NUM> would be present. However, due to the refractive index RI<NUM> of the second layer <NUM> of oxide material being higher the refractive index RI<NUM> of the first layer <NUM> of oxide material, when the fiber end face <NUM> and/or the optical waveguide <NUM> is centered on the optical waveguide <NUM> of the device <NUM>, the light <NUM> generally leaks into the substrate <NUM> and may be lost, a situation which is exacerbated by the optical waveguide <NUM> being further generally manufactured with an increasing effective refractive index (e.g. a tapered structure). While <FIG> shows the light <NUM> exiting the optical fiber <NUM> and entering the end face <NUM>, it is understood that the light <NUM> may exit the end face <NUM>, and enter the optical fiber <NUM>; however, a similar problem exists in this situation when the index matching material <NUM> is absent.

The problem may be at least partially addressed by using the second layer <NUM> of the oxide material (e.g. the thick dielectric slab waveguide layer) to couple the light <NUM> to and from the optical fiber <NUM>. In particular, as the refractive index RI<NUM> of the second layer <NUM> is greater than both the refractive index RI<NUM> of the first layer <NUM> of the oxide material, and the refractive index RIIM of the index matching material <NUM>, the second layer <NUM> of the oxide material effectively acts, at least at the end face <NUM>, as an optical waveguide to couple the light <NUM> into, and out of, the coupler device <NUM>. Put another way, at the end face <NUM>, the effective refractive index of the optical waveguide <NUM> is at a minimum and/or at about the refractive index RI<NUM> of the second layer <NUM> of the oxide material. Hence, at the end face <NUM>, the light <NUM> interacts with the second layer <NUM> of the oxide material acting as an optical waveguide at a higher refractive index RI<NUM>, higher than the refractive index RI<NUM> of the first layer <NUM> of the oxide material and the index matching material <NUM>, which effectively act as cladding relative to the second layer <NUM> of the oxide material. Put another way, at the end face <NUM>, the combination of the second layer <NUM> of the oxide material surrounded by the first layer <NUM> of the oxide material and the index matching material <NUM> form a similar optical structure as the optical fiber <NUM>.

Put yet another way, the thick dielectric slab "waveguide" second layer <NUM> couples light to and from the optical fiber <NUM>, and the refractive index of the second layer <NUM> is greater than both the "sub-insulating" dielectric layer <NUM> and the super-cladding index matching material <NUM>. Furthermore, the optical waveguide <NUM> is is shaped to adjust the effective "optical mode" refractive index and provide a transition mechanism to couple light into or out of the thick dielectric slab "waveguide" second layer <NUM>, to or from the thick dielectric slab "waveguide" second layer <NUM>.

For example, as depicted, the light <NUM> is depicted at different positions <NUM>, <NUM>, <NUM>, <NUM> as it travels through the second layer <NUM>. Each subsequent position <NUM>, <NUM>, <NUM>, <NUM> is further from the end face <NUM>, and towards the interior of the device <NUM> (e.g. towards the internal optical components). Furthermore, at subsequent position <NUM>, <NUM>, <NUM>, <NUM>, the effective refractive index of the optical waveguide <NUM> is understood to increase.

At the first position <NUM>, immediately adjacent the end face <NUM>, the light <NUM> has about the same intensity as when entering the end face <NUM>; the light. However, at the next position <NUM>, further towards the interior of the device <NUM>, a portion <NUM> of the light has leaked into the optical waveguide <NUM>. At yet a next position <NUM>, yet further towards the interior of the device <NUM>, a larger portion <NUM> of the light has leaked into the optical waveguide <NUM>. Similarly, at yet a next position <NUM>, yet further towards the interior of the device <NUM>, a subsequently larger portion <NUM> of the light has leaked into the optical waveguide <NUM> until, at yet a further position, all of the light <NUM> has leaked into the optical waveguide <NUM> as light <NUM>. At the position where the light <NUM> is depicted, it is understood that the effective refractive index of the optical waveguide <NUM> has increased to the refractive index RIWG of the waveguide material. Furthermore, it is understood that the length of the optical waveguide <NUM> over which the refractive index increases from the minimum at the end face <NUM> to (e.g., at least approaching) the refractive index RIWG of the waveguide material is selected to promote the leaking of a maximum portion of the light <NUM> into the optical waveguide <NUM> (though some loss may occur). Indeed, the length of the optical waveguide <NUM> is understood to be selected such that the light <NUM> is detectible and/or processible by the optical components of the device <NUM>.

It is further understood that the depicted process is reversible. For example, the light <NUM> travelling towards the end face <NUM> will generally leak into the second layer <NUM> and exit the end face <NUM> at the second layer <NUM> and into the optical waveguide <NUM> of the optical fiber <NUM>. Hence, light can be coupled to and from the optical fiber <NUM>, and to and from the optical waveguide <NUM> via the second layer <NUM>. Hence, it is further understood that the length of the optical waveguide <NUM> is understood to be selected such that light <NUM> travelling towards the end face <NUM>, that generally leaks into the second layer <NUM> and exits the end face <NUM> at the second layer <NUM> and into the optical waveguide <NUM> of the optical fiber <NUM>, is i detectible and/or processible by the optical components that receive such light via the optical fiber <NUM>. Hence it is understood that the length of the optical waveguide <NUM> is any suitable length, which may be determined heuristically.

In some examples, the "insulating" index matching material <NUM> is in a range of between about <NUM> to about <NUM> thick, the optical waveguide <NUM> is in a range of between about <NUM> to about <NUM> thick, and the second layer <NUM> of the oxide material is in a range of between about <NUM> and about10 µm thick. Furthermore, the widths of the optical waveguide <NUM> and the second layer <NUM> may be any suitable values, which may be determined heuristically to promote leakage therebetween as described above. However, it is understood that while certain dimensions are described herein for the various components of the device <NUM>, such dimensions are not meant to be exhaustive, and functionality of the device <NUM> as described herein may be achieved with other dimensions.

Furthermore, in some examples, the waveguide material and/or the optical waveguide <NUM> may comprise silicon, and the oxide material of the layers <NUM>, <NUM> may comprise silicon oxide. As such, the refractive index RIWG of the waveguide material of the optical waveguide <NUM> may be about <NUM> (e.g. the refractive index of silicon), the refractive index RI<NUM> of the oxide material of the second layer <NUM> may be in a range of about <NUM> to about <NUM> (e.g. the refractive index of a doped silicon oxide), and the refractive index RI<NUM> of the oxide material of the first layer <NUM> and the refractive index RIIM may each be about in a range of about <NUM> to about <NUM> (e.g. the refractive index of silicon oxide). However, it is further understood that the refractive index RI<NUM> of the oxide material of the first layer <NUM> and the refractive index RIIM also satisfies a condition of being less than the refractive index RI<NUM> of the oxide material of the second layer <NUM>.

Control of the effective index of the optical waveguide <NUM> is next described with respect to <FIG> and <FIG>.

For example, <FIG> and <FIG> each show a "downward" view of examples of the optical waveguide <NUM> and the second layer <NUM>, for example in a direction of the substrate <NUM> perpendicular to an optical axis and/or longitudinal axis of the optical waveguide <NUM>. As depicted, the second layer <NUM> surrounds, and/or is located on opposite sides of the optical waveguide <NUM>.

In particular, <FIG> depicts a tapered structure of the optical waveguide <NUM>, while <FIG> depicts a modulated tapered structure of the optical waveguide <NUM>. The optical waveguide <NUM> may be manufactured according to either of the depicted structures, both of which cause the effective refractive index of the optical waveguide <NUM> to increase from the end face <NUM> towards the interior of the device <NUM>.

With reference to <FIG>, the waveguide material of the optical waveguide <NUM> is tapered and increasing in width from the end face <NUM> inwards. In particular, as depicted, at the end face <NUM>, the waveguide material of the optical waveguide <NUM> is at a point and/or tip of the tapering, and towards the interior of the device <NUM> increases in width. As such, and as the second layer <NUM> surrounds, and/or is located on opposite sides of the optical waveguide <NUM> at the end face <NUM>, the effective refractive index of the optical waveguide <NUM> is formed by a combination of the refractive index RI<NUM> of the oxide material of the second layer <NUM> and the refractive index RIWG of the waveguide material of the optical waveguide <NUM>. As the width of the waveguide material of the optical waveguide <NUM> at the end face <NUM> is at a point, and/or very narrow as compared to the respective width of the oxide material of the second layer <NUM>, at the end face <NUM>, the effective refractive index of the optical waveguide <NUM> may be about equal to the refractive index RI<NUM> of the oxide material of the second layer <NUM>. However, as the width of the waveguide material of the optical waveguide <NUM> increases, the contribution to the effective index by the refractive index RIWG of the waveguide material increases and the effective refractive index of the optical waveguide <NUM> also increases to be greater than both the refractive indices RI<NUM>, RI<NUM> of the oxide material of the layers <NUM>, <NUM>. Indeed, the effective index of the optical waveguide <NUM> may approach, and/or be about equal to, the refractive index RIWG of the waveguide material, for example, as light exits (or enters) the optical waveguide <NUM> at the interior of the device <NUM> (e.g. to or from the interior optical components).

With reference to <FIG>, the waveguide material of the optical waveguide <NUM> may alternatively have a modulated taper structure, which may have similar optical properties as the tapered structure of <FIG>.

In particular, the modulated taper structure comprises: separated portions of the waveguide material extending inwards from the end face <NUM> for a given length <NUM>; and thereafter a taper structure extending inwards from the end face <NUM>. Put another way, the modulated taper structure is similar to the tapered structure of <FIG>, but there are separated portions of the waveguide material between a tip and/or point of a tapered structure and the end face <NUM>, the modulated taper structure comprising separated dots and/or separated lines of the waveguide material that are aligned along a longitudinal axis of the tapered structure. Such a modulated tapered structure may have similar optical properties as the tapered structure of <FIG>, but the effective refractive index along the given length <NUM> may increase less than the effective refractive index along a similar length of the tapered structure of <FIG>.

While two example structured for the optical waveguide <NUM> are depicted, it is understood that any suitable structure for the optical waveguide <NUM> that provides an increasing effective refractive index from the end face <NUM> is within the scope of the present specification.

It is further understood that, regardless of the structure of the optical waveguide <NUM>, the fiber end face <NUM> and the optical waveguide <NUM> of the optical fiber <NUM> is about aligned with the second layer <NUM> of the oxide material, about centered on the second layer <NUM> of the oxide material, and adjacent to and/or "above" the optical waveguide <NUM> of the device <NUM>. Indeed, the optical waveguide <NUM> of the optical fiber <NUM> is aligned with the second layer <NUM> of the oxide material, and about centered on line that is through a center of the optical waveguide <NUM> and perpendicular to a longitudinal axis of the optical waveguide <NUM>.

According to the claimed invention, and with reference to <FIG>, which schematically shows a perspective view of the device <NUM> and the optical fiber <NUM> being assembled, the device <NUM> comprises an alignment structure <NUM>, extending outward from the end face <NUM> (e.g. away from the interior of the device <NUM> and/or towards an exterior edge <NUM> of the device <NUM>), the alignment structure <NUM> configured to about center the fiber end face <NUM> of the optical fiber <NUM> with the second layer <NUM> of the oxide material at the end face <NUM>, such that light from the optical fiber <NUM> enters the second layer <NUM> of the oxide material at the end face <NUM>, or respective light from the second layer <NUM> of the oxide material enters the optical fiber <NUM> at the fiber end face <NUM>.

It is further understood that only a portion of optical fiber <NUM> is depicted in <FIG>, and the optical fiber <NUM> may extends out of the page of <FIG> for tens, hundreds or thousands of meters, or more. Furthermore, <FIG> only depicts a portion of the device <NUM>, which may include a plurality of optical waveguides <NUM>, etc., with a plurality of corresponding alignment structures <NUM>, to interface with a plurality of optical fibers <NUM>.

In particular, <FIG> further graphically depicts a method to assemble the optical fiber <NUM> and the device <NUM>. According to the claimed invention, an end of the optical fiber <NUM> that includes the fiber end face <NUM>, is lowered and/or placed into the alignment structure <NUM>, and the alignment structure has a shape that, when end the optical fiber <NUM> that includes the fiber end face <NUM> is lowered and/or placed into the alignment structure <NUM>, the alignment described with respect to <FIG> is achieved (the optical waveguide <NUM> of the optical fiber <NUM> is aligned with the second layer <NUM> of the oxide material at the end face <NUM>).

<FIG> further shows that the index matching material <NUM>, for example in the form of an optical epoxy, may be used to attach the optical fiber <NUM> to the device <NUM>, and fill the region between the end faces <NUM>, <NUM>, as well as cover the second layer <NUM>. However, any suitable combination of the index matching material <NUM> and another epoxy, and the like, may be used to attach the optical fiber <NUM> to the device <NUM>.

In particular, as depicted, and the alignment structure <NUM> may comprise a V-shaped groove extending outwards from the end face <NUM>, which may be formed from the material of the substrate <NUM>, which may extend outward from the end face <NUM> to the depicted edge <NUM>, with the layers <NUM>, <NUM> and the optical waveguide <NUM> grown on the substrate <NUM> adjacent the alignment structure <NUM>, though the alignment structure <NUM> may be formed before or after formation of the layers <NUM>, <NUM> and the optical waveguide <NUM>, and/or at any suitable point in the manufacturing of the device <NUM>. In particular, the V- shaped groove of the alignment structure <NUM> may etched into the substrate <NUM>.

An end view of the V- shaped groove of the alignment structure <NUM> is further depicted in <FIG>, after assembly of the device <NUM> and the optical fiber <NUM>, the view of the V- shaped groove of the alignment structure <NUM> being along an optical axis of the optical waveguide <NUM> of the optical fiber <NUM>. Components of the optical fiber <NUM> are depicted as being transparent to show their positions relative to the components of the device <NUM>.

As clearly seen in <FIG>, sides of the optical fiber <NUM> are resting and/or held into place in the V- shaped groove of the alignment structure <NUM> (e.g. by the optical epoxy of the index matching material <NUM>, and/or another epoxy, and the like), such to achieve the alignment between the optical waveguide <NUM> of the optical fiber <NUM> and the second layer <NUM> of the oxide material. As such, it is understood that slopes of sides of the V- shaped groove of the alignment structure <NUM>, and a depth of the V- shaped groove of the alignment structure <NUM> are selected to achieve such alignment.

<FIG> further shows that the optical waveguide <NUM> of the optical fiber <NUM> is aligned with the second layer <NUM> of the oxide material, and about centered on a line <NUM> that is through a center of the optical waveguide <NUM> and perpendicular to a longitudinal axis of the optical waveguide <NUM> (e.g. which is understood to be normal to the page of <FIG>).

<FIG> further shows that the index matching material <NUM> may have any suitable shape on the optical fiber <NUM> and the second layer <NUM>.

Attention is next directed to <FIG> which depicts a method <NUM> for manufacturing a waveguide coupler device, such as the device <NUM> combined with the optical fiber <NUM>.

At a block <NUM>, the device <NUM> is provided, the device <NUM> comprising:.

In particular, the device <NUM> may be manufactured using any suitable combination of deposition techniques, etching techniques and the like.

At a block <NUM>, an alignment structure <NUM> is formed at the device <NUM> extending outward from the end face <NUM>, the alignment structure <NUM> configured to about center a fiber end face <NUM> of an optical fiber <NUM> with the second layer <NUM> of the oxide material at the end face <NUM>, such that light from the optical fiber <NUM> enters the second layer <NUM> of the oxide material at the end face <NUM>, or respective light from the second layer <NUM> of the oxide material enters the optical fiber <NUM> at the fiber end face <NUM>.

The alignment structure <NUM> may comprises a V-shaped groove extending outwards from the end face <NUM>, for example formed via etching in the substrate <NUM>.

At a block <NUM>, the fiber end face <NUM> of the optical fiber <NUM> is aligned and/or centered with the second layer <NUM> of the oxide material at the end face <NUM>.

At a block <NUM>, at least the second layer <NUM> of the oxide material and the end face <NUM> are encapsulated with the index matching material <NUM>, a respective refractive index of the index matching material <NUM> being about index matched to the first refractive index of the first layer <NUM>. In particular, the index matching material <NUM> may fill any gap between the end faces <NUM>, <NUM>, and further encapsulates that portion of the second layer <NUM> where light is travelling therethrough, as described above with respect to <FIG>.

In this specification, elements may be described as "configured to" perform one or more functions or "configured for" such functions. In general, an element that is configured to perform or configured for performing a function is enabled to perform the function, or is suitable for performing the function, or is adapted to perform the function, or is operable to perform the function, or is otherwise capable of performing the function.

It is understood that for the purpose of this specification, language of "at least one of X, Y, and Z" and "one or more of X, Y and Z" can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XY, YZ, XZ, and the like). Similar logic can be applied for two or more items in any occurrence of "at least one. " and "one or more. " language.

The terms "about", "substantially", "essentially", "approximately", and the like, are defined as being "close to", for example as understood by persons of skill in the art.

Claim 1:
A device (<NUM>) comprising:
a substrate (<NUM>) comprising a waveguide material having a waveguide refractive index (RIWG);
a first layer (<NUM>) of oxide material on the substrate (<NUM>) having a first refractive index (RI<NUM>) lower than the waveguide refractive index (RIWG);
an optical waveguide (<NUM>) on the first layer (<NUM>) of the oxide material, the optical waveguide (<NUM>) comprising the waveguide material having the waveguide refractive index (RIWG);
a second layer (<NUM>) of the oxide material on the optical waveguide (<NUM>) and the first layer (<NUM>) of the oxide material, the second layer (<NUM>) of the oxide material having a second refractive index (RI<NUM>) higher than the first refractive index (RI<NUM>) and less than the waveguide refractive index (RIWG),
the first layer (<NUM>) of the oxide material, the optical waveguide (<NUM>) and the second layer (<NUM>) of the oxide material forming an end face (<NUM>) for light coupling, and the optical waveguide (<NUM>) extending inwards from the end face (<NUM>) and increasing in effective refractive index from the end face (<NUM>);
an index matching material (<NUM>) on the second layer (<NUM>) of the oxide material that encapsulates at least the second layer (<NUM>) of the oxide material and the end face (<NUM>), a respective refractive index (RIIM) of the index matching material (<NUM>) being index matched to the first refractive index (RI<NUM>);
an optical fiber (<NUM>); and
an alignment structure (<NUM>) extending outward from the end face (<NUM>), the alignment structure (<NUM>) configured to about center a fiber end face (<NUM>) of the optical fiber (<NUM>) with the second layer (<NUM>) of the oxide material at the end face (<NUM>), such that light from the optical fiber (<NUM>) enters the second layer (<NUM>) of the oxide material at the end face (<NUM>), or respective light from the second layer (<NUM>) of the oxide material enters the optical fiber (<NUM>) at the fiber end face (<NUM>).