Abstract
An infrared spectrometer chip including a suspended micro-platform, the suspended micro-platform being configured as a thermal detector with integrated photonic and phononic structure. The chip in embodiments includes temperature controlled elements including a photonic source, filter, sensor and detector. Thermoelectric devices are disposed on the micro-platform.
Claims
1. An infrared spectrophotometer apparatus comprised of at least one each of a photonic source (PS) element, a photonic crystal waveguide sensor (PCWS) or photonic crystal filter (PCWF) element and a photonic crystal waveguide detector (PCWD) element disposed on a chip, and with the chip further comprised of one or more of an integrated photonic and phononic coupler (IP&P) wherein each coupler IP&P is disposed proximally with a micro-platform; a photonic signal originating from a photonic source PS element is guided through one or more of a sensor PCWS element and/or a filter PCWF element and continues further into a detector PCWD element and the detector PCWD element is comprised of a thermoelectric sensor and a thermally-dissipative termination.
2. The apparatus of claim 1 wherein an element is disposed on or within a coupler IP&P or micro-platform.
3. The apparatus of claim 1 wherein one or more micro-platforms are comprised of heating and/or cooling devices.
4. The apparatus of claim 1 wherein the photonic signal is guided through a conventional photonic waveguide PW or a photonic crystal waveguide PCW and wherein the waveguide comprised of a slab, holey or slotted core structure.
5. The apparatus of claim 1 comprised of a photonic crystal waveguide sensor PCWS element operated with a slow wave waveguide mode providing a sensitivity to an analyte disposed on or near the PCWS element.
6. The apparatus of claim 1 with a photonic crystal waveguide sensor PCWS adapted to monitor and/or identifying an analyte such as a gas, vapor, particulate, liquid, solid or biomolecular mass.
7. The apparatus of claim 1 comprised of a photonic crystal waveguide filter PCWF element having its transmission controlled by a thermoelectric device or physical dimensioning.
8. The apparatus of claim 1 wherein a tetherbeam is comprised of phononic scattering or phononic resonant structure adaptations, such as, without limitation, holes, cavities, atomic-level superlattices, atomic-level vacancies and engineered surfaces providing a reduced thermal conductivity.
9. The apparatus of claim 1 wherein a detector PCWD element is comprised of a thermally-dissipative termination structure such as, without limitation, a Bragg-absorbing photonic crystal waveguide PCW, coupled resonant RLC loops, photonic crystal resonators, and a field of nanotubes.
10. The apparatus of claim 1 wherein a detector PCWD element is comprised of one or more of a Seebeck thermocouple, bolometer, or thermistor having a sensitivity to temperature changes.
11. The apparatus of claim 1 where a PCWD element is comprised of a semiconductor bandgap diode providing a direct photon to electron conversion.
12. The apparatus of claim 1 wherein the photonic source PS element is comprised of one or more of a semiconductor laser, LED, OLED, fiber optic, heated membrane or filtered blackbody plasmonic emitter.
13. The apparatus of claim 1 wherein one or more elements are formed from the device layer of a silicon-on-insulator SOI wafer.
14. The apparatus of claim 1 wherein one or more active layer or layers are comprised, without limitation, of silicon, germanium, gallium arsenide, indium arsenide, gallium nitride and alloys thereof.
15. The apparatus of claim 1 wherein cladding external to the primary of the signal waveguide comprised of, without limitation, one or more of air, silicon dioxide, silicon nitride, aluminum oxide, PDMS, and PMMA.
16. The apparatus of claim 1 wherein the temperature of a micro-platform is controlled by an electrical heater providing a means of surface outgassing.
17. The apparatus of claim 1 wherein the temperature of an element is controlled to modulate photonic signal transmisson thereby providing a means for synchronous detection and/or switching.
18. The apparatus of claim 1 with an element structured to provide a means of amplitude modulating, selective wavelength filtering or controlling the delay of a photonic signal including such structures as a Mach-Zehnder interferometer.
19. The apparatus of claim 1 wherein a photonic source PS element is comprised of an off-chip photonic emitter and having a photonic beam transmitted through, backscattered from or reflected from an analyte such as a gas, vapor, particulate, biomolecular mass or surface.
20. The apparatus of claim 1 providing a photonic wattmeter monitoring the signal power from a photonic source PS element.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1A depicts plan view of a prior art photonic diffraction grating configured as a coupler into a photonic crystal waveguide providing one type of a photonic source PS when supplied by an emitter external to the chip.
[0046] FIG. 1B depicts a plan view of a prior art photonic diffraction grating configured as a coupler into a photonic slab waveguide providing a photonic source PS when supplied by an emitter external to the chip.
[0047] FIG. 2A depicts a plan view of a prior art photonic crystal waveguide with a holey waveguide core providing a bandwidth filter or photonic interconnect.
[0048] FIG. 2B depicts a plan view of a prior art photonic crystal waveguide with a slab waveguide core providing a bandwidth filter or photonic interconnect.
[0049] FIG. 3 depicts a plan view of a prior art photonic crystal waveguide with a holey core interfaced to a slab waveguides at input and output.
[0050] FIG. 4A depicts a plan view of a prior art photonic crystal waveguide sensor structured with two resonant high-Q sensor cavities within the slab core.
[0051] FIG. 4B depicts plan view of a prior art photonic crystal waveguide sensor structured with a resonant high-Q sensor cavity embedded into the cladding adjacent to the slab core.
[0052] FIG. 4C depicts plan view of a prior art photonic crystal waveguide sensor structured with a Mach-Zehnder interferometer having an internal high-Q resonant sensor cavity.
[0053] FIG. 5 depicts a plan view of a prior art photonic crystal waveguide with a non-reflecting photonic crystal termination.
[0054] FIG. 6 depicts a plan view of a prior art photonic chip structured with a photonic crystal waveguide sensor and with photonic input and output couplers.
[0055] FIG. 7 depicts plan view of a prior art tetherbeam with phononic scattering structures.
[0056] FIG. 8 depicts a plan view of a prior art thermally-isolated micro-platform supported by tetherbeams with phononic scattering structures
[0057] FIG. 9A depicts a plan view of a first photonic crystal waveguide filter PCWF embodiment comprised of integrated IP&P structures in accordance with embodiments of the invention
[0058] FIG. 9B depicts plan view of a second photonic crystal filter PCWF embodiment in accordance with embodiments of the invention.
[0059] FIG. 10A, 10B and 10C depict respective first, second and third plan views of photonic crystal waveguide sensor PCWS embodiments in accordance with embodiments of the invention
[0060] FIG. 11 depicts a plan view of a photonic crystal waveguide detector PCWD comprised of a thermally-isolated and thermally-heated micro-platform further comprising a thermoelectric Peltier array and a photonic crystal waveguide terminated in a zero-reflecting termination structure and where one PCW supporting tetherbeam is comprised of integrated photonic and phononic IP&P structures in accordance with embodiments of the invention.
[0061] FIG. 12A is a schematic depicting a chip comprising a photonic source PS, a photonic crystal waveguide sensor PCWS and a photonic crystal detector PCWD in accordance with embodiments of the invention.
[0062] FIG. 12B is a plan view depicting the chip of FIG. 12A comprising a 1D grating photonic source, a sensor micro-platform with a high-Q resonant cavity embedded in the cladding photonic crystal, and a photonic crystal waveguide detector PCWD with three phononic IP&P structures n accordance with embodiments of the invention.
[0063] FIG. 13A is a schematic depicting a chip comprising a photonic source PS, a photonic crystal waveguide filter PCWF, a photonic crystal waveguide sensor PCWS and a photonic crystal detector PCWD further comprising three integrated IP&P structures in accordance with embodiments of this invention..
[0064] FIG. 13B is a plan view depicting the chip of FIG. 13A comprising a 1D grating photonic source, a temperature-controlled photonic crystal waveguide filter PCWF, a sensor micro-platform PCWS, and a photonic crystal waveguide detector PCWD, further comprising five integrated IP&P structures in accordance with embodiments of the invention.
[0065] FIG. 14A is a schematic depicting a chip comprised of a photonic source PS having a single micro-platform for the sensor PCWS and detector PCWD in accordance with embodiments of the invention.
[0066] FIG.14B is a schematic depicting a chip comprised of a photonic source PS, a photonic crystal waveguide filter PCWF and having a single micro-platform for both the sensor PCWS and detector PCWD in accordance with embodiments of the invention.
[0067] FIG. 15 is a plan view depicting a chip structured as an embodiment depicted in
[0068] FIG. 14A with a grating photonic source PS with a single micro-platform providing both a Mach-Zehnder sensor PCWS and the photonic crystal waveguide detector PCWD.
[0069] FIG. 16 is a schematic depicting a chip comprising four photonic sources, five photonic crystal waveguide sensors PCWS and five photonic crystal waveguide sensors PCWD structures in accordance with embodiments of the invention.
[0070] FIG.17 is a schematic depicting a chip comprising a photonic source PS, dual photonic crystal waveguide filters, a photonic crystal waveguide sensor PCWS and a photonic crystal waveguide detector PCWD in accordance with embodiments of the invention.
[0071] FIG.18 depicts a photonic waveguide sensing apparatus disposed on the backside of a mobile telephone in accordance with embodiments of the invention.
[0072] FIG.19A depicts a plan view of a metamaterial photonic source with linear-type plasmonic emitter comprised of a structured array of antenna cells creating a photonic wave coupled into a photonic crystal waveguide with a slab core in accordance with embodiments of the invention.
[0073] FIG. 19B depicts a plan view of a metamaterial photonic source with circular-type plasmonic emitter comprised of a structured array of antenna cells creating a photonic wave coupled into a photonic crystal waveguide with a slab core in accordance with embodiments of the invention
[0074] FIG. 19C depicts a cross-section view of the photonic sources of FIGS. 19A and 19B.
DETAILED DESCRIPTION
[0075] Definitions: The following terms are explicitly defined for use in this disclosure and the appended claims:
[0076] infrared or IR refers to light of wavelength 700 nm to 1000 micrometers. In this spec infrared is also referred to as photonic or optical.
[0077] analyte refers to a gas, vapor, particulate or biomolecular material exposed to the photonic crystal waveguide sensor for the purpose of identification or monitoring.
[0078] analyzing refers to monitoring, identifying, or otherwise processing the signal provided to the detector as modulated by the analyte.
[0079] support layer refers to one or more layers that, in some embodiments, are disposed above or below the active layer. This layer or layers are generally low loss material and have a lower dielectric constant compared to the active layer. This layer can be formed from the buried oxide layer of a semiconductor-on-insulator wafer.
[0080] supported by means that, for example, one layer is supported by, but not necessarily disposed on, another layer. For example, a micro-platform is supported by tetherbeams which may not be disposed in or on the micro-platform.
[0081] micro-platform refers to a patterned layer having an overall dimension of about 100 nm up to about 1 cm. The micro-platform is generally an isothermal structure thermally isolated from a surrounding support layer.
[0082] tetherbeam refers to the suspended support structures with terminations disposed on the surrounding-support platform and a micro-platform.
[0083] IR source or infrared source means a radiation source typically comprised of one or more of a laser, LED, fiber optic, heated membrane, or metamaterial plasmonic emitter.
[0084] photonic structure refers to a dimensioned structure for sourcing, interfacing, coupling, focusing, guiding, switching, terminating and sensing a photonic wave.
[0085] phononic structure refers to a dimensioned structure for sourcing, interfacing, coupling, scattering, resonating and sensing conductive heat.
[0086] grating coupler means the photonic structure which couples an IR source into a photonic waveguide or a photonic crystal waveguide.
[0087] photonic waveguide or PW in this invention refers to a traditional 2-D or 3-D photonic structure for guiding a photonic wave through a core pathway surrounded by cladding of a lower effective index of refraction.
[0088] photonic crystal waveguide or PCW in this invention refers to a photonic guide comprised of a a core guided photonic pathway surrounded by a 2-D or 3-D periodic photonic crystal cladding structure.
[0089] photonic crystal waveguide sensor or PCWS refers to a sensor element comprised of photonic crystal waveguide structures sensitive to changes in the refractive index of a proximal media. The PCWS may or may not be disposed on a thermally-isolated micro-platform.
[0090] photonic crystal waveguide filter or PCWF refers to a filter element comprised of a photonic crystal waveguide structured to limit or shift the bandwidth of the photonic wave propagating through.
[0091] photonic crystal waveguide detector or PCWD refers to a photonic detector element comprised of a photonic crystal waveguide with thermally-dispersive structures providing a thermal means of detecting and monitoring an input photonic signal. The PCWD element is comprised of supporting tetherbeams having thermal-conductivity reducing structures.
[0092] active layer refers to the dielectric layer comprising the core guide within a filter PCWF, sensor PCWS or detector PCWD. In this invention, the active layer is generally the device layer of an SOI wafer.
[0093] photonic zero-reflection termination refers to the thermally-dispersive termination for the photonic crystal waveguide PCW contained within a PCWD element.
[0094] integrated photonic and phononic structure or IP&P refers to a coupling structure comprised of a tetherbeam for a micro-platform comprised of both photonic and phononic structures. It is further comprised of at least one photonic PW or PCW guide and phononic thermal conductivity-reducing structures. In emodiments the IP&P may also provide a galvanic connection to sensor or heating elements on a micro-platform.
[0095] active layer refers to the primary layer comprising the PCW. This layer may be comprised of a plurality of layered thin films.
[0096] SOI refers to a wafer comprised of a semiconductor topside device layer, an intermediate oxide film, and an underlying handle substrate. In the case of silicon SOI the three layers are silicon device, silicon dioxide and silicon handle layers.
[0097] thermoelectric device or TED refers to a device converting a temperature differential or absolute temperature into an electrical voltage. The TED may be of a passive-type such as a bolometer, semiconductor bandgap diode, thermistor, Peltier cooler or resistive heater, or, alternatively, it may be of an active-type such as a Seebeck thermocouple sensor.
[0098] bolometer refers to a passive thermoelectric sensor, comprising material such as vanadium oxide, with a resistance to AC current flow that is proportional to incremental changes in temperature
[0099] spectrophotometer refers to an instrument providing a measurement of optical power within one or more wavelength components of an optical beam.
[0100] The photonic source PS in this invention is generally comprised of a Bragg-type grating providing a photonic signal into a tapered slab waveguide. The tapered waveguide is required to downsize the cross-section of the beam to match the smaller entrance structure of a PCW which further guides the photonic signal through to a detector disposed within the spectrophotometer. Off-chip infrared emitters include one or more of a laser, especially a quantum cascade laser (QCL), LED, OLED, fiber optic, heated membrane or plasmonic emitter. These sources including plasmonic sources having metamaterial blackbody emitters with resonant plasmonic filter structures are well known to those skilled in the art.
[0101] In some embodiments the photonic source PS element is comprised of an off-chip photonic emitter having a photonic beam transmitted through, backscattered from or reflected from an analyte such as a gas, vapor, particulate, biomolecular mass or surface. In these embodiments radiation originating off-chip is focused onto an on-chip grating.
[0102] FIG. 9A depicts a photonic crystal waveguide filter PCWF element disposed on a micro-platform 920. In this structure a PCW 910 with appropriate structuring is disposed between the entrance port 990 and exit port 950 of a micro-platform 920. The PCW I in this illustrative embodiment is comprised of a slab-type core guide. The micro-platform 920 is comprised of a central core of the PCW, a heating element within heater 931 and a thermistor 970. A cavity 921 bounded by a surrounding support platform at perimeter 925 extends underneath the micro-platform 920. A plurality of tetherbeams such as tetherbeam 930 and the underlying cavity 921 provide thermal-isolation to the microplatform. Tetherbeams at the entrance port 990 and exit port 950 are comprised of integrated photonic and phononic IP&P structures 960 and 940. These IP&P structures are adapted to provide a tetherbeam comprised of a guide PCW with structures further providing a reduced-thermal conductivity for the micro-platform 920.
[0103] In the illustrative embodiment of FIG. A and FIG. 9B, the micro-platform 920 is heated with a resistive heater 931 connected to an external voltage source through separate electrically-conducting tetherbeams 930 and 931. These tetherbeams have an internal structure providing a reduced thermal conductivity. Micro-platform temperature is monitored with a thermistor 970 connected via electrically-conducting tetherbeams to bonding pads illustrated by pad 980.
[0104] FIG. 9B depicts another embodiment of a photonic crystal waveguide filter PCWF, similar to that of FIG. 9A, except that the resistive heater element is disposed orthogonally with respect to the PCW. In this embodiment the electrical resistivity of the active layer comprising the micro-platform 920 provides an electrical resistor between the galvanic connection provides through tetherbeams 930 and 936. The heater is powered from an external voltage source connected through a bonding pad 980 and another on tetherbeam 936.
[0105] The filter PCWF of FIG. 9A in this embodiment is fabricated from a starting silicon SOI wafer. The photonic crystal waveguide PCW, tetherbeams, and micro-platform 920 are formed of an active layer of a starting wafer. In this embodiment the silicon device layer of the starting SOI is typically of high resistivity. The thermoelectric galvanic circuit paths within tetherbeams and in the micro-platform are created by impurity doping using a spin-on dopant such as B, P, or As with lift-off lithography patterning. Doping of the tetherbeams is performed typically using a spin-on dopant with lift-off patterning followed by a contact etch and a sputtered aluminum contact 960 and further appropriate patterning.
[0106] Next, the silicon device is fully or partially covered with a stress relief layer of silicon nitride from a CVD deposition process using a silane and ammonia precursor. This stress relief layer also provides an upper cladding film covering the integrated IP&P coupling structures 940 and 960. The resulting film topside of the silicon buried oxide layer is selectively patterned using a DRIE plasma and deep submicron lithography. Finally the micro-platform is released from the silicon handle wafer using an HF-vapor etch. The processing technology for fabricating the photonic devices of this invention is well known to those skilled in the art of semiconductor device fabrication and MEMS.
[0107] In other embodiments cladding films external to the plane of the photonic core are comprised, without limitation, of one or more of silicon dioxide, silicon nitride, aluminum oxide, PDMS, and PMMA. In some embodiments, the active layer is comprised,without limitation, of silicon, germanium, gallium arsenide, indium arsenide, gallium nitride and alloys thereof.
[0108] In embodiments the PCWF element is operated as a thermally-controlled gating switch or bandwidth tuning filter. The guide PCW within a filter PWCF in embodiments may be structured to provide slow-wave operation to provide a phase delay for the photonic signal. In some embodiments a PCWF element is disposed directly onto the dielectric layer of a SOI wafer without a micro-platform or temperature control. In embodiments one or more active layer or layers are comprised, without limitation, of silicon, germanium, gallium arsenide, indium arsenide, gallium nitride vanadium oxide, zinc oxide and alloys thereof including materials where the refractive index is sensitive to temperature.
[0109] FIGS. 10A, 10B and 10C depict representative embodiments of photonic crystal waveguide sensor PCWS elements comprised of guide PCW 910. A photonic signal enters the PCW 910 at port 990, proceeds successively through a first integrated IP&P structure 960, on to the PCW sensing area having a high-Q sensor structure within the PCW, continues into a second integrated IP&P structure 940 or 1040 and exits at port 950. The integrated IP&P structures 960 and 940/1040 are disposed on tetherbeams. The micro-platform and all tetherbeams including 930 and 931 are disposed over cavity 921.
[0110] In this embodiment the guide PCW formed within the micro-platform is operated in a slow-wave mode to provide a maximum sensitivity with exposure to an analyte of interest. The periodic holes in the cladding structure of a PCW create a negative index dispersion at an infrared wavelength of interest which significantly reduces the group velocity for a wave propagating through a core guide path. In the illustrated PCWS embodiments the group velocity of the propagating wave through the core is significantly delayed with respect to free space propagation. In embodiments of this invention the guided wave core may be a slab, holey or slot-type. The amplitude of the signal exiting the sensor PCWS is modulated by an analyte exposed to a high-Q resonator disposed within the PCW 910 and micro-platform 920. In these embodiments tetherbeams 930 and 931 provide a galvanic connection to a resistive heater disposed on the micro-platform 920.
[0111] The sensor PCWS of FIG. 10A depicts embodiment 1000A and is comprised of a single illustrative high-Q resonator 1061 imbedded in the cladding area of guide PCW 910. The resonator is electromagnetically coupled to the evanescent tail of the slow-wave propagating through the guide PCW slab core. Quality factors of 10,000 and higher are achieved with these resonant structures. The resonator provides a high sensitivity to nearby minute changes in refractive index when exposed to an analyte of interest.
[0112] The sensor PCWS of FIG. 10B depicts embodiment 1000B comprised of a single high-Q resonator 1062 disposed in the PCW core and electromagnetically coupled to the slow-wave propagating through the core. In this illustrative embodiment 1000B the core guide is of holey type. In this embodiment the optical signal propagates through from entrance port 990 and through a PCW 910 to exit port 950. The photonic transmission through the sensor PCWS is very sensitive to an analyte on or near the high-Q cavity 1062.
[0113] The PCWS of FIG. 10C depicts another embodiment of a sensor PCWS element wherein the guide PWC 910 is comprised of a holey core and interfaces with a standard slab waveguide PC at the entrance 990 and exit 950 ports. A central area 1063 within the holey PCW core is comprised of increasing and decreasing hole diameters providing an increased sensitivity upon exposure to an analyte of interest. The discontinuity introduced by structure 1063 in the optical path is sensitive to small changes in refractive index presented by an analyte disposed in or near the sensitive core area 1063.
[0114] An incremental shift in the distance of holes in the cladding area of the integrated IP&P couplers 960 and 1040 provides a desirable photonic impedance match between the central PCW and the conventional slab waveguide 910. The impedance matching structure of IP&P tetherbeams 960 and 1040 depicted by the in FIG. 10C can be used in this and other embodiments of this invention wherein a non-reflecting coupling of signals between waveguides of different structure and type is desired.
[0115] Processing of the sensor PCWS element depicted in the embodiments of FIG. 10A, 10B and 10C is similar to that of the illustrative examples in FIG. 9. In embodiments the sensor PCWS element is adapted further, generally with the addition of unique mechanical structures, to control exposure and transport of an analyte of interest to the sensor element.
[0116] In some embodiments a PCWF element is disposed directly onto the dielectric layer of a SOI wafer without a micro-platform or temperature control
[0117] FIG. 11 depicts a photonic crystal waveguide detector PCWD element comprised of a photonic crystal waveguide PCW terminating into a dissipative photonic crystal structure. In this sensor a photonic signal enters the PCWD through guide 1010 at entrance port 1090 and propagates through integrated IP&P 960 into the micro-platform 920. The integrated IP&P structure provides a coupling from off-platform to on-platform sections of the PCW 1010. The PCW 1010 is terminated on-platform into a resonant-Bragg absorbing structure 1163 disposed within the PCW 1010. The underlying cavity 921 is bounded by the surrounding support structure 925. In other embodiments, the dissipative termination structure may be comprised of one or more of coupled resonant RLC loops, low-Q photonic crystal resonators, and a field of nanotubes. The dissipative structure 1163 converts the optical power delivered by the PCW 1010 into heat which increases the temperature of the isothermal micro-platform structure 920. The incremental increase of temperature of the micro-platform 920 is proportional to the optical power delivered to the termination 1163.
[0118] The detector PCWD of FIG. 11 is further comprised of several sensing and control devices. The incremental temperature increase of the micro-platform 920 due to absorbed photonic signal is sensed with a series connection of Seebeck thermoelectric devices 1160. The micro-platform is heated with a resistive device 1162 powered from an external voltage source and is monitored with thermistor device 1163. The micro-platform is cooled with series connection of Peltier thermoelectric devices 1161 powered from an external voltage source. The detector PCWD of FIG. 11 is fabricated using processes similar to those used for the filter PCWF and sensor PCWS.
[0119] FIG. 12A and 12B depict a spectrophotometer chip having three elements comprised of a source PS 100A, a sensor PWCS 1000A and a detector PCWD 1100. The source 100A is a 1-D Bragg grating with a tapered slab waveguide feeding a photonic signal into a PCWS 1000A followed by a PCWD 1000. The sensor PCWS and the detector PCWD are disposed on separate micro-platforms. This embodiment is comprised of three integrated IP&P couplings onto and off micro-platforms. In applications this embodiment provides a spectrophotometer sensitive to an analyte exposed to the sensor PCWS 1000A. The Bragg grating 100A is an example of a photonic source PS element which in this embodiment is further comprised of an external laser, LED, OLED, incandescent or metamaterial filtered blackbody emitter.
[0120] FIG. 13A and 13B depict a a spectrophotometer chip having four elements. A source PS 100A originates a photonic signal which propagates through filter PCWF 900A and a sensor PWCS 1000A with termination into detector PCWD 1100. This embodiment three micro-platforms are linked through five couplings IP&P. In applications this embodiment provides a spectrophotometer sensitive to an analyte exposed to the sensor PCWS 1000A. The chip is processed using cleanroom tools and processes well known to those skilled in the art.
[0121] FIG. 14A depicts a spectrophotometer chip with a source PS 100A and a single micro-platform 1450. A source PS is connected via a guide into a structure which integrates a sensor PCWS element and a detector PCWD element into a single micro-platform 1450.
[0122] FIG. 14B depicts a spectrophotometer chip with a source PS 100A and two micro-platforms. A source PS 100A element provides a signal through a guide to filter 900A element and on to integrated sensor and detector elements. A first micro-platform comprises a filter PCWF 900A. A second micro-platform comprises the integrated sensor PCWS and detector PCWD (1450).
[0123] FIG. 15 is a plan view 1500 depicting the spectrophotometer of FIG. 14A. Source PS 100A provides signal through a slab waveguide coupled into the photonic crystal waveguide PCW of a sensor PCWS 1560 element. After the photonic signal is conditioned in the sensor PCWS element it propagates through a PCW guide onto a detector PCWD disposed on micro-platform 920. The sensor PCWS 1560 element is of Mach-Zehnder type and is disposed within an IP&P coupler disposed on a tetherbeam of micro-platform 920. The detector PCWD is comprised of a resonant-Bragg termination 1561 disposed on the micro-platform 920. The micro-platform is thermally isolated from a surrounding support platform 925 by the several tetherbeams comprising the sensor PCWS element and other tetherbeams comprising various thermoelectric devices. Two in-line high-Q resonant cavities disposed within one of two core guides within the M-Z interferometer provide a differential sensitivity to an adjacent analyte of interest.
[0124] The Mach-Zehnder interferometer of FIG. 15 is disposed immediately adjacent to the surrounding support structure 920 which is heat sinking and therefore is maintained at a constant temperature compared with the micro-platform. The dissipative termination 1561 disposed on the thermal micro-platform 920 is effectively thermally-isolated from the surrounding support platform 925 by phononic structuring of the micro-platform 920 and tetherbeams. Structural examples of such phononic structuring is disclosed in prior art such as U.S. Pat. No. 9,236,552. The integrated structures of FIG. 15 effectively thermally isolate the M-H sensor from the dissipative termination 1561 as required for proper spectrophotometer operation.
[0125] In FIG. 15 additional devices 1631 and 1532 comprising tetherbeams and on-platform resistors provide a heater 1531 and a thermistor 1532. An array of Seebeck thermoelectric devices 1160 senses the incremental temperature differential between the PCW termination 1561 structure and the surrounding support platform 925. The unpatterned area 1562 of the micro-platform 920 provides a desirable increased thermal coupling between the termination structure 1561 and the Seebeck thermoelectric array 1160.
[0126] The schematic of FIG. 16 depicts an integration of multiple photonic functions on chip 1600 providing a further complex spectrophotometer function. In this embodiment three photonic sources PS 100A and PS 100B provide a signal through photonic guides to a a plurality of sensor PCWS 1000A elements and a filter PCWF 900A element. Each sensor PCWS element provides a signal modulated by an analyte to a detector PCWD 1100 element. The source PS 100A with optical fan-out=1 provides for a non-differential sensing of an analyte. The source PS 100B structured with an optical fan-out=2 provides for a differential sensing of an analyte.
[0127] The schematic of FIG. 17 depicts another spectrophotometer chip embodiment comprised of two filter PCWF 900A elements which in some embodiments provides a thermal on/off switch of the photonic beam originating from the source PS 100B. This chip in embodiments provides for implementing a form of synchronous detection using the filter PCWF elements as switches. In other embodiments the two filter PCWF elements 900A provide a thermal means of tuning the center bandwidth wavelength of the two filter PCWF elements separately. The signal gated or tuned by the two filters PCWF next propagates through a sensor PCWS 1750 element and on into a detector PCWD 100 element. This chip in embodiments provides for implementing multi-wavelength spectral analysis of an analyte exposed in the PCWS 1750. In this embodiment the detector PCWD 1100 is designed with adequate bandwidth to dissipate signals from the PCWS 1750 over an adequate wavelength range.
[0128] The oblique view of FIG. 18 depicts an application comprising the spectrophotometer configured as an apparatus 1820 attached to a mobile phone 1810. The spectrophotometer communicates with and receives DC power from the mobile phone typically through a micro-USB bus 1830.
[0129] FIGS. 19A and 19B depict plan views and FIG. 19C depicts a cross-section view of metamaterial plasmonic photonic sources PS disposed on a micro-platform 1920 providing a photonic signal into a tapered slab waveguide 1940 and further into a guide PCW 1950. The guide PCW 1950 provides an optical signal from the exit port 1960 forward into appropriate filters and sensors disposed within the spectrophotometer chip. Excitation for the photonic source is derived from thermal heating of the micro-platform 1920 through resistive heaters 1970 and 1975. The photonic emission results from localized magnetic and dipole resonances excited by the thermal surface energy coupling to the metallic surface structures. In this emitter a plurality of depicted tetherbeams 1980 provide a galvanic connections to resistive heaters patterned into the micro-platform 1920.
[0130] The photonic sources PS 1900A and 1900B are comprised of a periodic array of metamaterial metallic resonators disposed on the active region of the micro-platform 1920. The blackbody spectrum of radiation from the surface areas of the photonic source is filtered by and in certain cases enhanced by the plasmonic resonances of metamaterial resonators 1901 and 1902. These plasmonic electromagnetic fields are controlled by the size and shape of the metallic surface resonators in addition to the permittivity and temperature of the underlying micro-platform.
[0131] Photonic sources PS 1900A and 1900B with blackbody filtering resonators 1901 and 1902 are fabricated using cleanroom processes similar to those used for other micro-platform structures of the invention. A processing difference is that the patterned metamaterial metallic resonators 1901 and 1902 are created onto the device layer requiring additional processing steps. Open holes 1990 in the device layer are patterned topside through the device layer to facilitate etch removal of the underlying oxide and release of the micro-platform to create an underlying cavity 1930. The open holes 1990 are not required when the micro-platform is released using a patterned backside TMAH, KOH or DRIE etch. The metamaterial resonators are comprised typically of appropriate patterned metal films such as aluminum, gold, tungsten or silver. In some embodiments a different 501 starting wafer is comprised of a BoX dielectric layer such as aluminum oxide.
[0132] The metamaterial resonators within photonic sources 1900A and 1900B are dimensioned respectively as a cross and an semicircle. There are in addition a great variety of resonator shapes that can be appropriately dimensioned for this embodiment.
[0133] FIG. 19C depicts a view cross-section a-a of emitters 1900A and 1900B depicting the a released micro-platform 1920 and a underlying topside-etched cavity 1930. The device layer is patterned to create the micro-platform 1920, the PCW 1950 and a surrounding support area 1925. The output port 1960 is physically connected to selected photonic devices such as a sensor PCWS or the filter PCWF. A buried oxide (BoX) layer 1915 of a starting silicon SOI wafer is sandwiched between the device layer 1925 and a handle wafer 1935. In some embodiments the PCW 1950 is disposed in a tetherbeam attached to the micro-platform 1920. The PCW when disposed withinin a tetherbeam comprises an integrated IP&P structure.
[0134] Spectrophotometer Adapted for Backscattered Infrared
[0135] In some embodiments the photonic source PS for the spectrophotometer is backscattered infrared from an external analyte. In this embodiment an infrared source illuminates an external analyte and a collector lens focusses a backscatter beam into the on-chip photonic grating. The resulting photonic signal is processed through a PCWS sensor which in this case provides a wavelength filter for signal into the PCWD detector. Specific wavelength of the backscatter are analyzed to identify or monitor species in the analyte typically a remote gas or vapor.
[0136] It is to be understood that although the disclosure teaches many examples of embodiments in accordance with the present teachings, many additional variations of the invention can easily be devised by those skilled in the art after reading this disclosure. As a consequence, the scope of the present invention is to be determined by the following claims.
