Polarization modulation interrogation of grating-coupled waveguide sensors
An optical interrogation system and a GCW sensor are described herein that are used to determine whether a biological substance (e.g., cell, molecule, protein, drug) is located in a sensing region of the GCW sensor. The optical interrogation system includes a light source, a polarization modulator and a detection system. The light source outputs a polarized light beam and the polarization modulator modulates the polarized light beam and outputs a polarization-modulated light beam. The GCW sensor receives and converts the polarization-modulated light beam into an amplitude modulated light beam that is directed towards the detection system. The detection system receives the amplitude modulated light beam and demodulates the received amplitude modulated light beam by responding to signals at a modulation frequency of the polarization-modulated light beam and ignoring noise affecting the signals outside the modulation frequency to detect a resonant condition (e.g., resonant angle, resonant wavelength). The detected resonant condition that has a one-to-one relationship with the refractive index of the superstrate containing the biological substance is analyzed to determine whether or not the biological substance is located in the sensing region of the GCW sensor.
1. Field of the Invention
The present invention relates in general to a grating-coupled waveguide (GCW) sensor and, in particular, to an optical interrogation system and method for using polarization-modulated light beams to interrogate a GCW sensor in order to determine whether or not a biological substance is located within a sensing region of the GCW sensor.
2. Description of Related Art
Grating-coupled waveguide (GCW) sensors are fast becoming the technology of choice to enable accurate label-free detection of a biological substance (e.g., cell, drug, chemical compound). This technology typically involves the use of a waveguide evanescent field to sense changes in the refractive index of a GCW sensor caused by the presence of a biological substance in a sensing region of the GCW sensor. To generate the evanescent field, an optical interrogation system is used which has a light source that couples a light beam into a waveguide of the GCW sensor. The optical interrogation system also includes a detector that receives a light beam coupled out from the waveguide that is analyzed to determine the effective refractive index of the waveguide. In determining the effective refractive index of the GCW sensor it should be understood that the light beam received by the detector had interacted with the waveguide under a resonant condition, where the wavevectors of a diffraction grating, incoming light beam, and guided mode all sum to zero. And, that this resonant condition occurs only for a specific wavelength and angle of the incoming light where changes in this angle or wavelength corresponds to changes in the effective refractive index of the waveguide caused by the presence of the biological substance in the sensing region of the GCW sensor. Thus, the optical interrogation system is used to sense a change in the effective index of the GCW sensor which enables one to determine whether or not a biological substance is located within the sensing region of the GCW sensor.
For this technology to be viable, one must have an optical interrogation system and in particular a detector capable of accurately monitoring the resonant angle, wavelength, or both. In particular, the optical interrogation system must emit a light beam that interacts with the GCW sensor, and must in turn receive the light beam coupled-out off the GCW sensor and process that light beam to detect in real time any changes in it's resonant angle and/or wavelength. While there are many approaches for accomplishing these tasks, each has unique implementation challenges, since the light beam output from the GCW sensor is relatively weak and there are multiple sources of noise that degrade this light beam especially in high-throughput screening applications.
GCW sensors are particularly attractive for use in high-throughput screening applications, where the absence of fluorescent tags and the possibility of reduced false-negatives would provide a large cost advantage. For this reason, the microplate has been targeted as the platform for such sensors, where 96 or 384 individual wells provide the high-throughput access demanded by the industry. In this application, the waveguide and diffraction grating of the GCW sensor are located in the bottom of each well; e.g., the diffraction grating may be stamped into the well bottom, and the waveguide subsequently grown on top of the diffraction grating. The wells themselves are typically composed of an optically transparent, low-birefringence, low-cost plastic that is typically several millimeters thick. To probe the GCW sensor in the well bottom while leaving the tops of the wells open for fluid handling, etc., the optical light beam is emitted into the bottom of the microplate and passes through the well plastic before striking the GCW sensor. One source of noise for this type of optical interrogation system is produced by the Fresnel reflection emanating from the bottom surface of each well. Due to the large number of wells, one ideally tries to design the GCW sensor to operate with incoming light beams near normal incidence. As a result, this spurious Fresnel reflection which acts as noise is often inextricably mixed with the light beam output from the GCW sensor that contains the desired information about the resonant angle and/or wavelength. In addition to the Fresnel reflection caused by the bottom surface of the microplate, the top surface of the waveguide inserts yet another Fresnel reflection into the output light beam that mingled with the light beam that propagated as a waveguide mode and exited the GCW sensor through the diffraction grating.
In addition to these direct optical noise sources, the traditional optical interrogation system is susceptible to other electrical and optical noises. For example, the wavelength or angle of the output light beam is often monitored with detectors such as charge-coupled device (CCD) cameras or spectrographs that observe the signal in a DC fashion. All of the DC electrical and optical (stray light) noise can impede the detection of the resonant angle and/or wavelength in the output light beam. Accordingly, there is a need for an optical interrogation system and method that can avoid the aforementioned problematical noise sources when interrogating one or more GCW sensors. This need and other needs are satisfied by the optical interrogation system, GCW sensor and method of the present invention.
BRIEF DESCRIPTION OF THE INVENTIONThe present invention includes an optical interrogation system capable of interrogating a GCW sensor to determine whether a biological substance (e.g., cell, molecule, protein, drug) is located in a sensing region of the GCW sensor. The optical interrogation system includes a light source, a polarization modulator and a detection system. The light source outputs a polarized light beam and the polarization modulator modulates the polarized light beam and outputs a polarization-modulated light beam. The GCW sensor receives and converts the polarization-modulated light beam into an amplitude modulated light beam that is directed towards the detection system. The detection system receives the amplitude modulated light beam and demodulates the received amplitude modulated light beam by responding to signals at a modulation frequency of the polarization-modulated light beam and ignoring noise affecting the signals outside the modulation frequency to detect a resonant condition (e.g., resonant angle, resonant wavelength). The detected resonant condition that has a one-to-one relationship with the refractive index of the superstrate containing the biological substance is analyzed to determine whether or not the biological substance is located in the sensing region of the GCW sensor.
BRIEF DESCRIPTION OF THE DRAWINGSA more complete understanding of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:
Referring to
As shown in
The biological substance 102 which may be located within a bulk fluid is introduced to the superstrate 103 (sensing region) of the GCW sensor 100 and it is the presence of this biological substance 102 that alters the index of refraction at the surface 104 of the GCW sensor 100. Thus, to detect the biological substance 102, the GCW sensor 100 is probed with a light beam 126 emitted from the light source 122 and then a reflected light beam 128 received at the detection system 124 is analyzed to determine if there are any changes (˜1 part per million) in the refractive index caused by the presence of the biological substance 102 in the sensing region 103 of the GCW sensor 100. In one embodiment, the top surface 104 may be coated with biochemical compounds (not shown) that only allow surface attachment of specific complementary biological substances 102 which enables an GCW sensor 100 to be created that is both highly sensitive and highly specific. In this way, the optical interrogation system 120 and GCW sensors 100 may be used to detect a wide variety of biological substances 102 and if the GCW sensors 100 are arranged in arrays they may be used to enable high throughput drug or chemical screening studies (see
The sensitivity of the GCW sensor 100 may be best understood by analyzing the structure of the diffraction grating 108 and the waveguide 110. The light beam 126 shone on the diffraction grating 108 can only be coupled into the waveguide 110 if its wave vector satisfies the following resonant condition as shown in equation no. 1:
k′x=kxκ [1]
where kx′ is the x-component of the incident wave vector, kx is the guided mode wave vector, and κ is the grating vector. The grating vector κ is defined as a vector having a direction perpendicular to the lines of the diffraction grating 108 and a magnitude given by 2π/Λ where Λ is the grating period (pitch). This expression may also be written in terms of wavelength λ and incident angle θ as shown in equation no. 2:
Where θ is the angle of incidence of the light beam 126, ninc is the index of refraction of the incident medium, λ is the wavelength of the light 126, and neff is the effective index of refraction of the waveguide 110. The effective index of the waveguide 110 is a weighted average of the indices of refraction that the optical waveguide mode field or fundamental mode “sees” as it propagates through the waveguide 110. The fundamental mode preferably has a spatial extent that is much wider than the waveguide 110 itself, the extent depending on the refractive index difference between the waveguide 110 and the substrate 112, as well as between the waveguide 110 and the superstrate 103. In particular, the fundamental mode has an evanescent wave/tail that extends into the superstrate 103 (sensing region) which “sees” any surface changes created when the biological substance 102 approaches or comes in contact with the top surface 104 of the GCW sensor 100.
The previous expression shown in equation no. 2 may be rewritten in the more convenient form shown in equation no. 3:
which is the equation of a line where sin θ being the y axis, λ being the x-axis, Λneff the x-intercept, and −1/Λ the slope. To obtain equation no. 3, ninc has been set to 1 so that it could be removed from equation no. 2. This approximation is used since air (n˜1.0003) is the most common incident medium. This relation is pictured in the graph shown in
The resonant condition (e.g., resonant wavelength or resonant angle) of such a GCW sensor 100 may be interrogated to determine refractive index changes by observing the reflected light 128 from the GCW sensor 100 (see
To maintain simplicity and efficiency of operation, the GCW sensors 100 employed in biosensing applications can be designed such that only the zeroth diffracted orders of the incident light 126 propagate in free space, while what would be the ±1 orders couple to the fundamental mode of the waveguide 110. The higher diffraction orders are avoided by designing a sub-wavelength diffraction grating 108 which has a grating pitch A smaller than the desired operating wavelength λ of the incident light 126. In this case, the coupling efficiency of the waveguide 110 is large since multiple orders do not remove power from the GCW sensor 100. Moreover, since only the zeroth reflected and transmitted beams exist in free space, the GCW sensor 100 can thereby produce nearly total reflection or transmission of the desired (anomalous) wavelength λ of the incident light 126.
As mentioned above, GCW sensors 100 are used in biosensing applications because they enable one to determine the location of the resonance angle/wavelength 502 which directly corresponds to the refractive index of the superstrate 103 and thereby allows the monitoring of biological substance 102 binding on the GCW sensor 100. This is all possible because the evanescent tail of the propagating fundamental mode in the waveguide 110 senses index changes in the superstrate 103 caused by the presence of the biological substance 102. The index change in the supersrate 103 changes the resonance condition of the GCW 100 according equation no. 1 and then the resonance 502 shifts to a new wavelength or angle location. The location of the shifted resonance indicates the current index of the superstrate 103 which indicates whether or not the biological substance 102 is in the superstrate 103 of the GCW 100. It has been shown that the resonance 502 can shift hundreds of nanometers for a unit change in the refractive index of the superstrate 103 (see
Referring to
Referring to
As shown, the optical interrogation system 120a includes a light source 122a that outputs a polarized light beam 125a that is received by a polarization modulator 127a (e.g., photoelastic modulator 127a). The polarization modulator 127a modulates the polarized light beam 125a by causing a time-varying polarization alternation between TE and TM modes (see the wobbling vectors in
The use of the acousto-optic modulator 702a is attractive since it utilizes no moving parts, however other angular scanning techniques can be used in the present invention. For example, a simple rotating plate of glass could be used that deflects the polarization-modulated light beam 126a through refraction at the glass/air interface. The deflection angle depends upon the rotation angle of the glass plate such that the rotating plate causes a smoothly varying angle. The results of several experiments using the optical interrogation system 120a and the exemplary GCW sensor 100 are provided below with respect to
Referring to
It should be appreciated that the actual sensitivity of the optical interrogation system 120a to biological events depends upon the GCW sensor 100, instrument, angular stability, etc. Thus, to obtain some estimate of the performance of the experimental optical interrogation system 120a, index fluids were placed on the top surface 104 of the GCW sensor 100 to illicit a change in the resonant angle and thereby determine the refractive index unit sensitivity.
Another important aspect of the present invention, is that the lock-in amplifier 712a provides an extra observable beyond the simple amplitude resonance pictured above in
To understand what information the phase signal might present, one can examine the amplitude signal more closely.
This simple understanding serves to accurately predict what was observed during the experiments with the experimental optical interrogation system 120a.
Referring to
Referring to
Referring to
Referring to
Although
Referring to
Beginning at step 1602, the light source 122 and polarization modulator 127 are used to direct a polarization-modulated light beam 126 to the GCW sensor 100. At step 1604, the detection system 124 receives an amplitude modulated light beam 128 from the GCW sensor 100. Then at step 1606, the detection system 124 demodulates and analyzes the received amplitude modulated light beam 128 to detect a resonant wavelength or resonant angle which corresponds to a superstrate 103 refractive index that indicates whether a biological substance 102 is located on the surface 104 of the GCW sensor 100.
Following are some advantages and uses of the optical interrogation system 120 and GCW sensors 100 of the present invention:
-
- The use of polarization modulation in accordance with the present invention enables one to use large-area photodiodes that provides a cost advantage and robustness to the instrument design not currently available with traditional optical interrogation systems. Moreover, the use of large area detectors greatly relaxes the performance (flatness, etc.) required from the sensor wellplate. Basically, the reflected beam simply has to hit the photodiode somewhere in its area to be correctly detected and decoded. The only constraint in this situation is that the beams from separate wells do not “cross” each other in the farfield. In other words, each beam should retain its relationship relative to its neighbors, although neighbor proximity may vary from well to well. This is a much less stringent condition than would be required for coupling back into optical fiber, for example, or imaging the reflections onto CCDs used by traditional optical interrogation systems.
- The use of polarization modulation in accordance with the present invention can be applied to nearly every instrument designed to interrogate grating-coupled biosensors. The invention involves the overlay of polarization modulation and coherent (phase-sensitive) detection onto the structures of the traditional optical interrogation systems. This is true regardless of whether angle, wavelength or some other parameter is being scanned, either on the input or output of the GCW sensor 100.
- The present invention removes a large number of noise sources by taking advantage of optical beam polarization.
- The present invention drastically reduces the required power for detection of biological substances. As a result, the milliwatts of power typically required of the output beam for sensitive detection by a CCD element is reduced several orders of magnitude under this invention. This is very important for the high-throughput screening market, since 96, 384, or even 1536 wells may be interrogated in parallel with the same optical (laser) source.
- In addition to the signal-to-noise improvements associated with the present invention, there are several other equally important benefits of the technology. First, because the polarization modulation technique obtains high signal-to-noise data from ordinary photodiodes, the cost and complexity of the instrumentation can be greatly reduced compared to the expensive CCD or spectrograph solutions used by traditional optical interrogation systems. Moreover, the scale-up of the optical interrogation system 120 to accommodate 96 or 384 wells in a plate becomes much easier since one only needs to use more inexpensive detectors and lock-in amplifiers.
- In addition to the cost and complexity advantage of the present invention, the use of lock-in amplifiers provides phase information about the resonance previously unavailable. The presence of both amplitude and phase information from the phase-sensitive detection provides an extra observable. As discussed above, this phase information actually contains a convenient and unique signal that indicates the resonance location.
- The polarization modulation concept of the present invention can be implemented within most interrogation schemes (e.g., angular or wavelength-based approaches). It simply requires that the polarization be modulated in order to distinguish the waveguide output from noise, somewhat independent of the other variables of the system. In one embodiment of this invention, one could modulate the input beam polarization much faster than the angular scanning rate, such that the angular position is essentially constant during the demodulation process for each angular step.
- As described above, the preferred modulation method is photoelastic, where a quartz plate is vibrated to produce time-variable birefringence due to the photoelastic effect. This technology is preferred both for the purity of polarization modulation as well as high available modulation frequency, 100 kHz.
- Although the preferred embodiments of the present invention described above utilized a reflected light beam to enable the detection of the biological substance, it should be readily appreciated that a transmitted beam and even a beam exiting the side of the sensor could also be used to detect the biological substance. Of course, minor changes to the set-up of the system would be required to detect the transmitted beam or the beam exiting the side of the sensor.
Although several embodiments of the present invention has been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
Claims
1. A grating-coupled waveguide sensor comprising:
- a substrate;
- a diffraction grating; and
- a waveguide film, wherein a waveguide formed by said diffraction grating and said waveguide film receives a polarization-modulated light beam and outputs an amplitude modulated light beam that is analyzed by an optical interrogation system which demodulates the amplitude modulated light beam by responding to signals at a modulation frequency of the polarization-modulated light beam and ignoring noise affecting the signals outside the modulation frequency to determine whether a biological substance is located in a sensing region above said waveguide film.
2. The grating-coupled waveguide sensor of claim 1, wherein said biological substance is a cell, molecule, protein, drug, chemical compound, nucleic acid, peptide or carbohydrate.
3. The grating-coupled waveguide sensor of claim 1, wherein said optical interrogation system utilizes an angular scanning approach to scan the polarization-modulated light beam to enable the detection of a resonant angle which indicates whether the biological substance is located in the sensing region above said waveguide film.
4. The grating-coupled waveguide sensor of claim 1, wherein said optical interrogation system utilizes an angular scanning approach to scan the amplitude modulated light beam to enable the detection of a resonant angle which indicates whether the biological substance is located in the sensing region above said waveguide film.
5. The grating-coupled waveguide sensor of claim 1, wherein said optical interrogation system utilizes a wavelength scanning approach to scan the polarization-modulated light beam to enable the detection of a resonant wavelength which indicates whether the biological substance is located in the sensing region above said waveguide film.
6. The grating-coupled waveguide sensor of claim 1, wherein said optical interrogation system utilizes a wavelength scanning approach to scan the amplitude modulated light beam to enable the detection of a resonant wavelength which indicates whether the biological substance is located in the sensing region above said waveguide film.
7. An optical interrogation system for interrogating a grating-coupled waveguide sensor, said optical interrogation system comprising:
- a light source capable of outputting a polarized light beam;
- a polarization modulator capable of modulating the polarized light beam and outputting a polarization-modulated light beam;
- said grating-coupled waveguide sensor capable of receiving the polarization-modulated light beam and converting the polarization-modulated light beam into an amplitude modulated light beam;
- a detection system capable of receiving the amplitude modulated light beam and further capable of demodulating the received amplitude modulated light beam by responding to signals at a modulation frequency of the polarization-modulated light beam and ignoring noise affecting the signals outside the modulation frequency to detect a resonant condition which corresponds to a predetermined refractive index that indicates whether a biological substance is located in a sensing region of said grating-based waveguide sensor.
8. The optical interrogation system of claim 7, wherein said biological substance is a cell, molecule, protein, drug, chemical compound, nucleic acid, peptide or carbohydrate.
9. The optical interrogation system of claim 7, wherein said polarization modulator is a photoelastic modulator.
10. The optical interrogation system of claim 7, wherein said polarization modulator is a photorefractive modulator.
11. The optical interrogation system of claim 7, wherein said polarization modulator is a liquid crystal modulator.
12. The optical interrogation system of claim 7, wherein said grating-coupled waveguide sensor is located within a microplate.
13. The optical interrogation system of claim 7, wherein said detection system includes a photodiode capable of receiving the amplitude modulated light beam and converting the amplitude modulated light beam into an electrical signal that is demodulated by a lock-in amplifier.
14. The optical interrogation system of claim 13, wherein phase information within said demodulated electrical signal is used to identify the resonant condition which indicates whether the biological substance is located in the sensing region of said grating-coupled waveguide sensor.
15. The optical interrogation system of claim 13, wherein amplitude information within said demodulated electrical signal is used to identify the resonant condition which indicates whether the biological substance is located in the sensing region of said grating-coupled waveguide sensor.
16. The optical interrogation system of claim 7, further comprising:
- an acousto-optic modulator capable of receiving the polarization-modulated light beam from said polarization modulator and further capable of scanning the angle of the polarization-modulated light beam;
- a lens capable of receiving the polarization-modulated light beam from said acousto-optic modulator and further capable of directing the polarization-modulated light beam into said grating-coupled waveguide sensor; and
- said detection system including: a detector capable of receiving the amplitude modulated light beam from said grating-coupled waveguide sensor and further capable of converting the amplitude modulated light beam into an electrical signal; and a lock-in amplifier capable of receiving the electrical signal from said detector and further capable of demodulating the electrical signal to detect the resonant condition which indicates whether the biological substance is located in the sensing region of said grating-based waveguide sensor; and
- a function generator capable of synchronizing said polarization modulator and said lock-in amplifier.
17. The optical interrogation system of claim 7, further comprising:
- a lens capable of receiving the polarization-modulated light beam from said polarization modulator and further capable of directing the polarization-modulated light beam into said grating-coupled waveguide sensor; and
- said detection system including: a scanning pinhole plate capable of receiving the amplitude modulated light beam from said grating-coupled waveguide sensor and further capable of scanning the angle of amplitude modulated light beam; a detector capable of receiving the amplitude modulated light beam from said scanning pinhole plate and further capable of converting the amplitude modulated light beam into an electrical signal; and a lock-in amplifier capable of receiving the electrical signal from said detector and further capable of demodulating the electrical signal to detect the resonant condition which indicates whether the biological substance is located in the sensing region of said grating-based waveguide sensor; and
- a function generator capable of synchronizing said polarization modulator and said lock-in amplifier.
18. The optical interrogation system of claim 7, further comprising:
- a tunable filter capable of receiving the broadband polarization-modulated light beam from said polarization modulator and further capable of scanning the wavelength of the polarization-modulated light beam;
- a beam splitter capable of receiving the polarization-modulated light beam from said tunable filter and further capable of directing the polarization-modulated light beam into said grating-coupled waveguide sensor; and
- said detection system including: a detector capable of receiving the amplitude modulated light beam from said grating-coupled waveguide sensor and further capable of converting the amplitude modulated light beam into an electrical signal; and a lock-in amplifier capable of receiving the electrical signal from said detector and further capable of demodulating the electrical signal to detect the resonant condition which indicates whether the biological substance is located in the sensing region of said grating-based waveguide sensor; and
- a function generator capable of synchronizing said polarization modulator and said lock-in amplifier.
19. The optical interrogation system of claim 7, further comprising:
- a beam splitter capable of receiving the polarization-modulated light beam from said polarization modulator and further capable of directing the polarization-modulated light beam into said grating-coupled waveguide sensor; and
- said detection system including: a scanning filter capable of receiving the amplitude modulated light beam from said grating-coupled waveguide sensor and further capable of scanning the wavelength of the amplitude modulated light beam; a detector capable of receiving the amplitude modulated light beam from said scanning filter and further capable of converting the amplitude modulated light beam into an electrical signal; and a lock-in amplifier capable of receiving the electrical signal from said detector and further capable of demodulating the electrical signal to detect the resonant condition which indicates whether the biological substance is located in the sensing region of said grating-based waveguide sensor; and
- a function generator capable of synchronizing said polarization modulator and said lock-in amplifier.
20. A method for interrogating one or more grating-coupled waveguide sensors, said method comprising the steps of:
- directing a polarization-modulated light beam into each grating-coupled waveguide sensor;
- receiving an amplitude modulated light beam from each grating-coupled waveguide sensor; and
- analyzing each received amplitude modulated light beam to detect a resonant condition which corresponds to a superstrate refractive index that indicates whether a biological substance is located in a sensing region of the respective grating-coupled waveguide sensor.
21. The method of claim 20, wherein said biological substance is a cell, molecule, protein, drug, chemical compound, nucleic acid, peptide or carbohydrate.
22. The method of claim 20, wherein said analyzing step further includes:
- converting each received amplitude modulated light beam into an electrical signal; and
- demodulating each electrical signal to identify the resonant condition which indicates whether the biological substance is located in the sensing region of the respective grating-coupled waveguide sensor.
23. The method of claim 22, wherein phase information within said demodulated electrical signal is used to identify the resonant condition which indicates whether the biological substance is located in the sensing region of the respective grating-coupled waveguide sensor.
24. The method of claim 22, wherein amplitude information within said demodulated electrical signal is used to identify the resonant condition which indicates whether the biological substance is located in the sensing region of the respective grating-coupled waveguide sensor.
25. The method of claim 20, wherein said analyzing step utilizes an angular scanning approach to scan the polarization-modulated light beam to enable the detection of a resonant angle which indicates whether the biological substance is located in the sensing region of the respective grating-coupled waveguide sensor.
26. The method of claim 20, wherein said analyzing step utilizes an angular scanning approach to scan the amplitude modulated light beam to enable the detection of a resonant angle which indicates whether the biological substance is located in the sensing region of the respective grating-coupled waveguide sensor.
27. The method of claim 20, wherein said analyzing step utilizes a wavelength scanning approach to scan the polarization-modulated light beam to enable the detection of a resonant wavelength which indicates whether the biological substance is located in the sensing region of the respective grating-coupled waveguide sensor.
28. The method of claim 20, wherein said analyzing step utilizes a wavelength scanning approach to scan the amplitude modulated light beam to enable the detection of a resonant wavelength which indicates whether the biological substance is located in the sensing region of the respective grating-coupled waveguide sensor
29. The method of claim 20, wherein said grating-coupled waveguide sensor is located within a microplate.
30. A microplate comprising:
- a frame including a plurality of wells formed therein, each well incorporating a grating-based waveguide that includes: a substrate; a diffraction grating; a waveguide film; wherein said substrate receives a polarization-modulated light beam that is converted into an amplitude modulated light beam after the polarization-modulated light beam interacts with said diffraction grating, said waveguide film and a sensing region of said waveguide film; and wherein said substrate outputs the amplitude modulated light beam that is received by an optical interrogation system that demodulates the amplitude modulated light beam by responding to signals at a modulation frequency of the polarization-modulated light beam and ignoring noise affecting the signals outside the modulation frequency to determine whether a biological substance is located in the sensing region of said waveguide film.
31. The microplate of claim 30, wherein said biological substance is a cell, molecule, protein, drug, chemical compound, nucleic acid, peptide or carbohydrate.
32. The microplate of claim 30, wherein said optical interrogation system utilizes an angular scanning approach to scan the polarization-modulated light beam to enable the detection of a resonant angle which indicates whether the biological substance is located in the sensing region of said waveguide film.
33. The microplate of claim 30, wherein said optical interrogation system utilizes an angular scanning approach to scan the amplitude modulated light beam to enable the detection of a resonant angle which indicates whether the biological substance is located in the sensing region of said waveguide film.
34. The microplate of claim 30, wherein said optical interrogation system utilizes a wavelength scanning approach to scan the polarization-modulated light beam to enable the detection of a resonant wavelength which indicates whether the biological substance is located in the sensing region of said waveguide film.
35. The microplate of claim 30, wherein said optical interrogation system utilizes a wavelength scanning approach to scan the amplitude modulated light beam to enable the detection of a resonant wavelength which indicates whether the biological substance is located in the sensing region of said waveguide film.
36. The microplate of claim 30, wherein said optical interrogation system utilizes a diffractive optic to generate the multiple polarization-modulated light beams that are directed towards the wells.
Type: Application
Filed: Jul 25, 2003
Publication Date: Jan 27, 2005
Inventor: Eric Mozdy (Elmira, NY)
Application Number: 10/627,438