Technique for dynamically controlling the incoupler of a beam-steering device
1. An optical system comprising:
- a beam-steering (BS) device comprising a planar waveguide region between a tapered incoupler and tapered outcoupler that respectively define opposing incoupler and outcoupler facets of the BS device, wherein each of the waveguide region, the incoupler, and the outcoupler comprises;
a subcladding layer over the substrate;
a core layer over the subcladding layer; and
a top cladding layer, wherein, within the incoupler, at least one of the subcladding layer and the top cladding layer comprises a material having a refractive index that varies with an applied field applied at the incoupler;
a field-applying device configured to apply the applied field at the incoupler;
an output detector configured to generate a feedback signal based on detected outgoing light output from the outcoupler; and
a controller configured to control the field-applying device based on the feedback signal to alter the outgoing light output from the outcoupler.
An optical system has a beam-steering device having a planar waveguide region between a tapered incoupler and a tapered outcoupler that respectively define opposing incoupler and outcoupler facets of the BS device. Each region has a substrate, a subcladding layer over the substrate, a core layer over the subcladding, and a top cladding layer over the core. Within the incoupler, at least one of the subcladding and the top cladding has a material having a refractive index that varies with an applied field (e.g., an electric field) applied at the incoupler. The optical system also has a field-applying device that applies the applied field at the incoupler, an output detector that generates a feedback signal based on detected outgoing light output from the outcoupler, and a controller that controls the field-applying device based on the feedback signal to alter the light output from the outcoupler.
|Thermo-optic liquid crystal waveguides|
Patent #US 7,570,320 B1
Current AssigneeAnalog Devices Inc.
Sponsoring EntityMichael H. Anderson, Scott D. Rommel, Scott R Davis
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Sponsoring EntityAnalog Devices Inc.
|THIN-FILM OPTICAL DEVICES|
Patent #US 3,614,198 A
Current AssigneeBell Telephone Laboratories Inc.
Sponsoring EntityBell Telephone Laboratories Inc.
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Sponsoring EntityBell Telephone Laboratories Inc.
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Sponsoring EntityVescent Photonics Incorporated
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Sponsoring EntityAnalog Devices Inc.
|OPTICAL COUPLER HAVING MULTIPLE THIN-FILM LAYERS WITH SPATIALLY VARYING OPTICAL THICKNESSES|
Patent #US 20190204711A1
Current AssigneeThe Government Of The United States Of America As Represented By The Secretary Of The Navy
Sponsoring EntityThe Government Of The United States Of America As Represented By The Secretary Of The Navy
- 1. An optical system comprising:
a beam-steering (BS) device comprising a planar waveguide region between a tapered incoupler and tapered outcoupler that respectively define opposing incoupler and outcoupler facets of the BS device, wherein each of the waveguide region, the incoupler, and the outcoupler comprises; a substrate; a subcladding layer over the substrate; a core layer over the subcladding layer; and a top cladding layer, wherein, within the incoupler, at least one of the subcladding layer and the top cladding layer comprises a material having a refractive index that varies with an applied field applied at the incoupler; a field-applying device configured to apply the applied field at the incoupler; an output detector configured to generate a feedback signal based on detected outgoing light output from the outcoupler; and a controller configured to control the field-applying device based on the feedback signal to alter the outgoing light output from the outcoupler.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
This application claims the benefit of the filing dates of U.S. provisional application No. 62/613,190, filed on Jan. 3, 2018; U.S. provisional application No. 62/613,185, filed on Jan. 3, 2018; and U.S. provisional application 62/635,952, filed on Feb. 27, 2018, the teachings of all of which are incorporated herein by reference in their entirety.
Under paragraph 1(a) of Executive Order 10096, the conditions under which this invention was made entitle the Government of the United States, as represented by the Secretary of the Navy, to an undivided interest therein on any patent granted thereon by the United States. This and related patents are available for licensing to qualified licensees.
The present invention relates to non-mechanical beam-steering devices and optical systems using such devices and, more particularly but not exclusively, to steerable electro-evanescent optical refractors (SEEORs) and optical systems using SEEORs for non-mechanical beam steering (NMBS) and other applications.
This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
Thin-film slab waveguides are utilized for a variety of applications, including refractive non-mechanical beam steering (NMBS). Typically, these systems are coupled using either external prisms or faceted substrates having a tapered subcladding layer, referred to herein as Ulrich couplers. See R. Ulrich, “Optimum excitation of optical surface waves,” Journal of the Optical Society of America 61(11), 1467-1477 (1971), the teachings of which are incorporated herein by reference. In both cases, the fundamental method of operation is similar: a tapered region creates a spatially varying interaction between the waveguide core and the prism/substrate. In prism-type optical couplers, a tapered air gap is created using either spacers or pressure to bend the prism substrate, while Ulrich couplers have a tapered subcladding. At a specific point along the tapered region, a phase-matching condition is reached between a guided mode in the coupler'"'"'s waveguide and the incident light, and coupling into the waveguide is achieved. In such devices, the phase-matching condition is achieved around extremely narrow poles in a calculated resonant term that is dependent on several features of the coupler structure and the interaction of the incident beam with the coupler.
As represented in
As shown in
When deployed in an optical system, light (e.g., laser light) that is incident at the incoupler facet 112 is coupled into the core 124 within the incoupler 102 and traverses along the core 124 through the waveguide region 104 to the outcoupler 106, where the light is emitted from the outcoupler facet 114.
While effective and routinely used, this coupling process has two fundamental limitations. First, the phase-matching conditions created are Inherently narrow-band, and they are extremely sensitive to the external angle of the source as it illuminates the incoupler facet 112 of conventional BS device 100. Second, for mid-wave infrared (MWIR) light (λ=3-5 μm), typical full-width half max (FWHM) bandwidths for waveguides coupled in this manner are ˜10-50 nm, with angular acceptance FWHM on the order of 0.1°, depending on the taper angles of the subcladding 122 within the couplers 102 and 106. Generally, these FWHM values will scale proportional to the wavelength of light, such that couplers designed to work with short-wave infrared light (λ=1.5-3 μm) will have proportionally narrower bandwidths and angular acceptances.
Embodiments of the invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which like reference numerals identify similar or identical elements.
Detailed illustrative embodiments of the present invention are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments of the present invention. The present invention may be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein. Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention.
As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It further will be understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” specify the presence of stated features, steps, or components, but do not preclude the presence or addition of one or more other features, steps, or components.
Broadband Optical Coupler Having Multiple Thin-Film Layers with Spatially Varying Optical Thicknesses
A new optical coupler has been developed that expands the wavelength acceptance bandwidth and angular acceptance FWHM by, in some embodiments, a factor greater than 10. In some embodiments, the new coupler relies upon spatially structuring multiple thin-film layers of the coupler structure to greatly extend the phase-matching conditions for coupling. By spatially structuring multiple thin-film layers, rather than tapering only the subcladding layer as is done in the conventional BS device 100 of
This innovation has a number of improvements over the current state-of-the-art. First, the greatly expanded bandwidth makes the new couplers source-agnostic, that is, able to simultaneously accommodate multiple narrow-line sources, tunable sources, or wideband sources such as supercontinuum lasers. Second, the increased angular acceptance greatly relaxes practical challenges in coupling, making the new couplers more robust with regards to manufacturing and assembly tolerances and in-service handling and vibration. NMBS devices fabricated using these new multiple-structured-layer couplers are able to accommodate wide-bandwidth/multi-line sources in a single refractive beam-steering device. With a conventional steerer, multiple steering devices must be used, or the external coupling angle must be changed to accommodate a change in wavelength of the source, practical limitations that impact the adoption of this technology.
Like the substrate 120 of the conventional BS device 100, the substrate 320 of the new BS device 300 is uniform within the waveguide region 304 and tapered (i.e., faceted) within the incoupler 302 with a taper angle θfacet and a taper length Lfacet that corresponds to the length of the incoupler 302.
Similarly, like the subcladding layer 122 of the conventional BS device 100, the subcladding layer 322 of the new BS device 300 is uniform within the waveguide region 304 and tapered within the incoupler 302 with a taper angle θsubclad, a taper length Lsubclad, and a thickness tsubclad at the input tip 308.
Significantly, however, unlike the core layer 124 of the conventional BS device 100, which is uniform within both the waveguide region 104 and the incoupler 102, in the new BS device 300 of
Note that the dimensions in
Although not shown in
In the embodiment shown in
Furthermore, one or more of the taper angles θfacet, θsubclad, and θcore, the taper lengths Lfacet, Lsubclad, and Lcore, and the tip thicknesses tfacet, tsubclad, and tcore, can be different in different instances of the new BS device 300 to achieve different coupling behavior and waveguide properties.
In operation, collimated or near-collimated light is coupled into the new BS device 300 through the substrate facet 312. Optimum parameters for the input coupling may be determined by modelling the structure. These parameters may include position along the incoupler facet 312, beam diameter, radius of curvature of the beamfront, and coupling angle. Light is coupled into the core 324 through the subcladding 322, and the higher refractive index of the core 324 relative to the subcladding 322 results in waveguiding in the core 324. The spatially varying thickness of the core 324 results in a spatially varying effective index for the fundamental mode of the incoupler 302, thus permitting phase matching to occur for a larger range of wavelengths to satisfy the phase-matching condition for a fixed input coupling angle in comparison with an Ulrich coupler without a tapered core, such as the Ulrich coupler 102 of
In example implementations of the new BS device 300 of
The subcladding and core layers 322 and 324 are then deposited by high-vacuum thermal evaporation on top of the silicon substrate 320 to create the device structure of
After subcladding deposition, the device is removed from the chamber, and a different shadow mask is used to grow a tapered core 324 of a suitable material, for example, As2Se3. The taper angle θcore is on the order of 50-500 μrad, and the substrate-mask separation is about 1.5 cm. The incoupler 302 is defined by the overlap between the tapered regions of the core 324 and the subcladding 322, constraining the lateral placements of the shadow masks relative to the tip 308 of the faceted substrate 320. In practice, the overlap region is designed to be approximately the size of the laser beam spot. The taper angles of each layer are not necessarily identical and can be independently adjusted to impact the coupling behavior, but, in practice, the taper angle θcore, of the core 324 will be less than the taper angle θsubclad of the subcladding 322 due to the larger refractive index of the core. Further, the taper angles are not necessarily symmetrical at the incoupler and outcoupler of the new BS device 300 and may be adjusted to impact such parameters as dispersion of the outcoupled beam, mode confinement in the core 324, and exit angle.
In one example implementation of the new BS device 300, the taper angle θsubclad of the subcladding 322 is about 500 μrad, and the taper angle θcore of the core 324 is about 160 μrad, with subcladding and core thicknesses tsubclad and tcore, of about 2 μm and about 1 μm, respectively, at the tip 308 of the new BS device 300. Within a spot size of about 1.4 mm, simulations of incoupling in this example new BS device 300 show a constant effective index and constant coupling angle over an about 1 μm bandwidth, with the optimum coupling spot (the spot at which phase matching occurs for a particular wavelength) shifting monotonically with wavelength from the tip 308 to the edge of the spot. Therefore, within the entirety of the spot, wavelengths with a bandwidth of about 1 μm should be coupled.
After fabrication, the example new BS device 300 was removed from the chamber and characterized using a broadband, multi quantum cascade laser (QCL) source that is continuously tunable between 3.6 μm and 4.7 μm, while guided power was measured using an integrating sphere and MWIR detector positioned to catch the outcoupled beam. An example conventional BS device 100 of
The new and conventional BS devices 300 and 100 with and without tapered cores, respectively, were fabricated using techniques described in Frantz, et. al, “Chalcogenide Glass Waveguides for Refractive Non-Mechanical Beam Steerer,” U.S. patent application Ser. No. 15/946,011 (“the '"'"'011 application”), filed Apr. 5, 2018, the teachings of which are incorporated herein by reference. The waveguide core was brushed to serve as a liquid crystal alignment surface, and a liquid crystal cell was fabricated on top of the waveguide using a liquid crystal with low MWIR absorption. The top of the liquid crystal cell was formed by a piece of quartz coated with indium tin oxide (ITO). The ITO was patterned with a prismatic electrode pattern to create the steering elements. The BS devices with tapered and non-tapered cores exhibited the same coupling behaviors as the corresponding bare incouplers (i.e., thin-film couplers without the LC layers, cover glass layers, and electrodes) while simultaneously undergoing active steering.
Embodiments of the new optical coupler 302 may provide one or more of the following advantages:
- The new couplers may have a significantly increased bandwidth compared to conventional Ulrich couplers, making them suitable for a wide range of laser sources that do not have narrow linewidths, such as supercontinuum and multi-line sources.
- The new couplers may have a significantly increased angular acceptance range compared to conventional Ulrich couplers, allowing them to support a more-robust method for coupling that is insensitive to in-service vibration and manufacturing error in system assembly.
- The new couplers may allow for simultaneous coupling, at either identical or different angles, of multiple narrow-line or broadband laser sources.
Although the subcladding layer 322 and the core layer 324 are tapered in both the incoupler and the outcoupler of the new BS device 300 of
The idea of having the tapered core 324 in the new optical coupler 302 of
In the embodiments of the new BS device described above, broadband coupling is achieved via spatial control of the effective index within the incoupler by tapering the core. In alternative embodiments, spatial control of the effective index can be achieved by techniques other than tapering the core. For example, other layers may be tapered, such as the top cladding, the substrate, or other incoupling layers that exist only within the incoupler (e.g., an incoupling layer between the subcladding and the core), either in addition to or instead of the core. In general, the tapering of any given layer may be linear or non-linear, independent of the tapering of any other layers, to spatially control the effective index of the incoupler.
Additional methods of providing a spatially controlled effective index may be used, including but not limited to spatially varying the composition and refractive index of the core and/or the subcladding (e.g., As2(SxSey) deposited via gradient techniques or through selective diffusion, where x and y vary across the incoupler), sub-wavelength effective medium structures, thermal gradients, and electro-optic effects (e.g., liquid crystal with fine-spaced tuning electrodes that have different voltages applied to them).
In general, the new couplers have two or more thin-film layers (e.g., subcladding, core, and/or top cladding) with spatially varying optical thicknesses, where optical thickness refers to the product of the thickness of a layer and the layer'"'"'s refractive index. In the new BS device 300 of
As described previously, the new couplers have full-width, half-maximum (FWHM) bandwidths and FWHM coupling angle tolerances that exceed those of conventional Ulrich couplers. In some embodiments of the new couplers, the FWHM bandwidths are greater than 60 nm and the FWHM coupling angle tolerances are greater than 0.4 degrees. In some embodiments of the new couplers, the FWHM bandwidths are greater than 150 nm and the FWHM coupling angle tolerances are greater than 1 degree. In some embodiments of the new couplers, the FWHM bandwidths are greater than 300 nm and the FWHM coupling angle tolerances are greater than 2 degrees. In some embodiments of the new couplers, the FWHM bandwidths are about 600 nm and the FWHM coupling angle tolerances are about 4 degrees.
Technique for Actively Controlling the Incouple of an Optical Coupler
A new coupling technique relies on active tuning of the effective index within the incoupler of a beam-steering device using the variable index of liquid crystal and a feedback loop to maximize guided power. Because the effective index within the incoupler is based on the refractive indices of all layers (e.g., the core, the subcladding, and the liquid crystal top cladding), the phase-matching condition for coupling, which depends strongly on effective index, can be tuned by applying an electric field to adjust the refractive index of the LC layer taking advantage of the birefringence of the liquid crystal. This change in the refractive index of the LC layer changes the effective index of the incoupler as a whole. Typically, the refractive index of liquid crystal can be varied from about 1.5 to about 1.7, though these values are dependent upon the exact composition of the liquid crystal mixture. At a fixed wavelength in a typical incoupler structure that is part of an MWIR SEEOR, this variation translates into a change in the effective index (Δneff) of about 0.01. While small in absolute magnitude, this change in effective index can have a very large impact on the coupling behavior due to the sensitivity of coupling to the resonant phase-matching condition.
The change in effective index can be used for a variety of effects when coupling light into the incoupler of a BS device. The change can compensate for vibration or manufacturing errors, by dynamically tuning the effective index to compensate for variations in coupling angle. The change can also accommodate wavelength instability of a source laser by changing the effective index to reestablish the phase-matching condition at a different wavelength. The concept of active effective index tuning addresses a number of issues with conventional SEEOR technology (e.g., its sensitivity to coupling angle and narrow-line sources) as well as enabling new capabilities that will be important for different applications.
Using the techniques described in the '"'"'011 application, the BS device 700 may be fabricated on a faceted silicon substrate 720 with a subclad layer of As2S3 and a core of As2Se3 (collectively labeled 722 in
The top of the cell (i.e., glass layer 728) is composed of quartz with a patterned indium-tin oxide (ITO) layer forming the incoupler electrode 734. There is an ITO contact pad above the incoupler 702. This contact pad serves to tune the effective index in the incoupler 702. The Si substrate 720 serves as the bottom contact for the liquid crystal cell. In this example, the incoupler electrode 734 over the incoupler 702 is a solid rectangular bar, but the electrode is not required to be this shape. The quartz 728 and ITO electrode 734 cover the entire incoupler 702, from the tip of the incoupler facet to beyond the faceted portion of the substrate 720.
As shown in
To demonstrate wavelength agility, an example of the BS device 700 was mounted on a rotational stage with the incoupler facet mounted at the center of rotation. Light from a tunable, fiber-coupled quantum cascade laser (QCL) was used to illuminate the incoupler facet with a spot size of about 1 mm. The guided power through the BS device 700 was measured using an integrating sphere with an MWIR photodetector mounted about 5 cm from the outcoupler facet. The BS device 700 was aligned such that efficient coupling was achieved at 4.5 μm, and a wavelength sweep was performed. The voltage on the incoupler electrode 734 was then increased, and another wavelength sweep was performed, and so on.
The electric-field-dependent incoupling characteristics of the BS device 700 of
In operation, incoming light 902 from a light source (not shown) is coupled into the BS device 700 at the incoupler 702 and corresponding outgoing light 904 is emitted from the BS device 700 at the outcoupler 706. The photodetector 906 converts the received outgoing light 904 into an electrical detector signal 908 that is monitored by the controller 910. The controller 910 transmits a driver-control signal 912 to instruct the LC driver 914 to generate a voltage-control signal 916 that drives the voltage supply 740 to apply a corresponding voltage to the incoupler electrode 734 to apply a corresponding electric field across the incoupler 702 that affects the incoupling characteristics of the BS device 700.
In one implementation, the optical system HA is operated to encode data into the outgoing light 904. In particular, for incoming light 902 of a suitable wavelength and a suitable angle of incidence, by selectively varying the electric field applied across the incoupler 702, the controller 910 is able to modulate the intensity of the outgoing light 904, where, for example, a logic 1 is represented by outgoing light 904 above a specified intensity and a logic 0 is represented by outgoing light 904 below that specified intensity. In this implementation, the optical system HA can function as a transmitter in an optical communication system transmitting the modulated outgoing light 904 encoding data to a remote receiver.
Furthermore, the optical system HA can be used to actively compensate for errors (e.g., due to mechanical misalignment) and/or temporal variations (e.g., due to source drift or vibration) in the wavelength and/or the angle of incidence of the incoming light 902. In particular, if the current wavelength of the incoming light 902 is not sufficiently matched for the current angle of incidence of the incoming light 902, then the magnitude of the applied electric field can be adjusted to improve that matching. Such improved matching can be achieved by modifying the magnitude of the electric field applied across the incoupler 702 to increase the magnitude of the detected outgoing light 904 at the photodetector 906. By monitoring the detector signal 908, the controller 910 can perform an appropriate search algorithm to find the voltage level that tunes the optical system HA as needed.
The optical system HA can also be used to achieve source multiplexing. The fast response of the liquid crystal input tuning allows for time-division multiplexing of multiple sources through a common BS device 700, operating either at a common input angle or different input angles. For example, two or more lasers operated at different wavelengths could simultaneously shine their light beams on the incoupler facet of the BS device 700, either at the same input angle or different input angles, depending on the lasers and the design of the BS device 700. The controller 910 can control the electric field applied by the incoupler electrode 734 to selectively tune the coupling behavior of the incoupler 702 to allow only one of the wavelengths to couple into the BS device 700. Conventional time-division optical multiplexing requires either turning on and off the light sources or providing additional optical elements (e.g., modulators, beam blanks, shutters, etc.) to selectively block light from all but the desired source. In the optical system HA, the multiplexing function is performed by the BS device 700 itself.
As described above, the optical system HA can address two major issues with conventional SEEORs: (i) they operate at a fixed wavelength and (ii) they are extremely sensitive to errors in coupling.
Although the BS device 700 has been described as having a single, monolithic incoupler electrode 734 above the incoupler 702, in other embodiments, the incoupler electrode 734 can be subdivided into smaller individual electrodes for greater spatial control of the tuning effect. The voltage to each of these electrodes may be controlled independently.
Although, in system HA, the controller 910 controls the electric field applied across the incoupler 702, in alternative embodiments, the controller 910 can control the source of the incoming light 902 to vary the wavelength and/or the angle of incidence of the incoming light 902 instead of or in addition to controlling the electric field.
In certain embodiments, an optical system comprises a beam-steering (BS) device comprising a planar waveguide region between a tapered incoupler and tapered outcoupler that respectively define opposing incoupler and outcoupler facets of the BS device, wherein each of the waveguide region, the incoupler, and the outcoupler comprises a substrate, a subcladding layer over the substrate, a core layer over the subcladding layer, and a top cladding layer, wherein, within the incoupler, at least one of the subcladding layer and the top cladding layer comprises a material having a refractive index that varies with an applied field applied at the incoupler. The optical system further comprises a field-applying device configured to apply the applied field at the incoupler, an output detector configured to generate a feedback signal based on detected outgoing light output from the outcoupler, and a controller configured to control the field-applying device based on the feedback signal to alter the outgoing light output from the outcoupler.
In certain embodiments of the foregoing, the applied field is an electric field.
In certain embodiments of the foregoing, the incoupler further comprises a top cladding layer comprising a material having a refractive index that varies with an applied field.
In certain embodiments of the foregoing, the top cladding layer comprises a liquid crystal material.
In certain embodiments of the foregoing, the BS device comprises an electrode over the top cladding layer of the incoupler.
In certain embodiments of the foregoing, the controller is configured to encode data into incoming light incident at the incoupler facet of the BS device by modifying the applied field at the incoupler in order to vary the magnitude of the outgoing light output from the outcoupler.
In certain embodiments of the foregoing, the controller is configured to modify the applied field to correct for mismatch between at least one of (i) wavelength of incoming light incident on the incoupler facet and (ii) an angle of incidence of the incoming light at the incoupler facet.
In certain embodiments, provided is method for controlling the optical system, wherein the method comprises coupling incoming light into the BS device at the incoupler, applying the applied field to the incoupler by the field-applying device, generating the feedback signal by the output detector, and controlling the field-applying device by the controller to change the applied field to alter the outgoing light output from the outcoupler.
Different implementations of the BS devices described herein, such as the conventional BS device 100 of
Although the optical couplers described herein have a liquid crystal top cladding layer, in alternative embodiments, the top cladding layer may be made of a different suitable material including air.
Depending on the wavelength region of interest and other requirements of the coupler, other material sets may be used, including but not limited to oxides (e.g., SiOx), oxynitrides (e.g., SiOxNy), nitrides (e.g., SiNx), fluorides (e.g., MgF2), Group-IV semiconductors (e.g., Ge), III-V compounds (e.g., GaAs), II-VI compounds (e.g., CdS), and other chalcogenide compounds (e.g., GeAsSeTe glasses).
In addition to or instead of shadow mask tapering, alternative tapering methods may be used, such as mechanical polishing, grayscale lithography, or a mask that is translated during deposition.
In addition to tapering the core and/or the subcladding, multiple other layers may be tapered, including the top cladding, substrate, or other incoupling layers that exist only within the coupling region, such as an incoupling layer between the subcladding and core. The taper profiles on these layers may be linear or nonlinear and may differ for different instances of the couplers to control the effective index within the incoupling region.
Additional methods of providing a spatially controlled effective index may be used, including but not limited to spatially varying the composition and refractive index of the core (e.g., As2(SxSey) deposited via gradient techniques or through selective diffusion, where x and y vary across the coupling region), sub-wavelength effective medium structures, thermal gradients, and electro-optic effects.
Although techniques have been described for controlling optical couplers by applying fields to either the incouple or the outcouple, those skilled in the art will understand that optical couplers can also be controlled by applying fields to both the incouple and the outcouple.
Although techniques have been described for controlling the characteristics of optical couplers by modifying the magnitudes of applied electric fields to take advantage of the voltage-dependent optical birefringence of liquid crystal, in other embodiments, other methods to dynamically adjust the waveguide effective index may be used, including but not limited to thermo-optic effects, solid-state electro-optic effects such as ferroelectric birefringence, amorphous-to-crystalline phase change, and semiconductor field effect induced index changes, or other methods including acousto-optic or magnetic field-driven effects.
Although the optical couplers described herein have a top cladding layer that has optical properties that are dependent on an applied (e.g., electrical) field, in alternative embodiments, in addition to or instead of the top cladding layer, optical couplers may have one or more other layers, such as a subcladding layer or a core layer, that have such optical properties.
As used herein, a teaching that a device shown in a figure has a second layer that is “over” a first layer implies that the second layer is above the first layer when the device is oriented as shown in that figure. The term “over” applies when the second layer physically abuts the first layer as well as when there are one or more intervening layers between the first and second layers. If the second layer physically abuts the first layer, then the second layer may be said to be “directly above” the first layer.
Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word “about” or “approximately” preceded the value or range.
It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain embodiments of this invention may be made by those skilled in the art without departing from embodiments of the invention encompassed by the following claims.
In this specification including any claims, the term “each” may be used to refer to one or more specified characteristics of a plurality of previously recited elements or steps. When used with the open-ended term “comprising,” the recitation of the term “each” does not exclude additional, unrecited elements or steps. Thus, it will be understood that an apparatus may have additional, unrecited elements and a method may have additional, unrecited steps, where the additional, unrecited elements or steps do not have the one or more specified characteristics.
The use of figure numbers and/or figure reference labels in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the interpretation of the claims. Such use is not to be construed as necessarily limiting the scope of those claims to the embodiments shown in the corresponding figures.
It should be understood that the steps of the exemplary methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments of the invention.
Although the elements in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.
All documents mentioned herein are hereby incorporated by reference in their entirety or alternatively to provide the disclosure for which they were specifically relied upon.
Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”
Unless otherwise specified herein, the use of the ordinal adjectives “first,” “second,” “third,” etc., to refer to an object of a plurality of like objects merely indicates that different instances of such like objects are being referred to, and is not intended to imply that the like objects so referred-to have to be in a corresponding order or sequence, either temporally, spatially, in ranking, or in any other manner.