Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Reexamination Certificate
1999-11-05
2001-04-03
Evans, F. L. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
C385S012000, C250S458100
Reexamination Certificate
active
06211954
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an integrated-optical luminescence sensor having an excitation light beam with a first optical axis, a planar waveguide, a sample interacting with the evanescent field thereof, and a detection beam path, with a second optical axis, that comes from the waveguide, or a luminescence detector, which represents a variant in the definition of the invention.
The invention relates especially to an integrated-optical luminescence sensor having an excitation light beam with a first optical axis, a planar waveguide, a sample interacting with the evanescent field thereof, and a detection beam path, with a second optical axis, that comes from the waveguide, and/or a coupling-out grating for coupling out the portion of the luminescence light guided in the waveguide, wherein the luminescence light to be detected by means of a luminescence detector is physically separate from the excitation light.
According to the state of the art, such sensors are employed to operate surface-sensitive optical substance sensors. In affinity sensory analysis, the molecules to be detected are selectively bound to the sensor surface and are detected by interaction with the guided lightwave. In the case of direct affinity sensory analysis, this is effected by measuring changes in refractive index, or another possible method is to detect the luminescence radiation excited by the guided wave.
The use of planar waveguides for the detection of luminescent substances is described in D. Christensen et al. Proc. SPIE 1886 (1993), 2-8. The beam path lies in one plane, so that in order to suppress reflections and scattered light (for example from the edges of the sensor) it is necessary to use dichroic beam splitters and cut-off filters, giving rise to adverse effects on the dynamic range and the detection sensitivity.
Sensors having planar waveguides and one or more grating couplers for coupling in and/or coupling out the guided waves are known, for example, from WO 93/01487, but only for the direct method of detection by means of the change in refractive index.
A disadvantage that may arise in the use of those arrangements for luminescence detection is that the beam is generally guided in an optical plane perpendicular to the waveguide surface (that is to say k-vectors of coupled-in and coupled-out radiation lie in one optical plane) and hence, in order to separate the excitation light and luminescence light and to suppress reflections and scattered light, those arrangements, likewise, require provisions such as dichroic beam splitters, screens, interference filters, notch filters or cut-off filters.
In the arrangement described in U.S. Pat. No. 5,081,012, which uses coupling gratings, the excitation light and luminescence light are coupled collinearly, or the excitation beam path and luminescence beam path lie in one optical plane. For the physical separation of those light components it is necessary to use curved grating lines, with the result that the production of the sensor element is very complex.
A method and an arrangement of that kind are also described in WO 95/33198, which is to be considered as part of this disclosure.
The problem underlying the invention is to render possible low-background-noise, high-sensitivity luminescence detection using an optical sensor platform having a coupling grating in which physical separation of excitation light, including reflections and luminescence light is achieved by the manner in which the excitation light and luminescence light beams are guided or by the utilization of different polarization properties of excitation light and luminescence light.
SUMMARY OF THE INVENTION
The problem is solved in a first embodiment of the present invention by using a luminescence sensor, the luminescence light incident on a suitable detector is physically separate from the excitation light by virtue of the geometric arrangement of the optical axes (k
ein
,
61
) and/or
by the use of polarization-selective optical components in the outgoing detection beam path (
60
)
and/or
by polarization-selective detection of the portion of luminescence radiation coupled out by a coupling-out grating (
7
)
and/or
by polarization-selective detection of the by a grating (
4
) acting as coupling-out grating for the excitation radiation, which grating is also used to couple in the excitation light.
That physical separation of the luminescence light incident on the detector from the excitation light may especially be achieved by an arrangement in which the two optical axes (k
ein
,
61
) are skew relative to one another according to a second embodiment.
In known sensors those axes have always been coplanar in highly symmetrical arrangements, as is customary and expedient in “direct” sensors which evaluate changes in refractive index.
The solution in a second embodiment removes the symmetry of the sensor at the earliest possible stage, and according to the second part of a fourth embodiment tilts the entry plane relative to the coupling-in plane. The angle of tilt is approximately from 1° to 30°, preferably from 2° to 15°, and is oriented to the angle of divergence of the excitation light beam, as well as to that of the detection beam path. The corresponding arrangement relate to advantageous further developments.
A third embodiment describes the variant in which the luminescence radiation emitted into space is captured without being influenced by the waveguide, while a fourth embodiment provides for the capture of the luminescence light coupled into the waveguide using a coupling-out grating. Also possible and expedient is the simultaneous execution of both kinds of detection.
This configuration is especially insensitive to minor misalignments and variations in angle, which is of great importance especially when the sensor is changed and for accommodating manufacturing tolerances in the sensor.
A further advantage of the arrangement according to the invention is that it is possible for the beam guidance system to be compactly constructed in an integrated module in which all light beams necessary for the use of the sensor can be coupled in, coupled out and detected. The miniaturization facilitated is also advantageous in reducing interfering influences caused by the environment, such as, for example, external light and vibration.
A fifth embodiment also relates to the capture of the luminescence light coupled into the waveguide, but the coupling-in grating provided for coupling in the excitation light is used. This arrangement is possible since the luminescence light coupled into and guided in the waveguide surprisingly has no preferred direction of propagation. Again, simultaneous execution of this method of detection together with one or both of the previously described methods of detection is also possible. In addition, that arrangement has the advantage that the same grating can be used both for coupling in the excitation light and for coupling out the luminescence light guided in the waveguide with subsequent detection.
A sixth embodiment relates to a specific arrangement of the skew geometry with the aim of obtaining as little interference as possible to the luminescence light by excitation light in the detector. Another possibility is a form (of arrangement) according to which the excitation light beam and the detection beam path are so configured in cross-section, divergence, orientation and point of meeting with the waveguide that it is not possible for light from the excitation light beam to pass into the detection beam path as a result of a single reflection off any face.
According to a seventh embodiment it is possible, in principle, to take advantage of the different polarization properties of excitation light and luminescence light if completely polarized excitation light, that is to say completely transversely magnetically polarized excitation light (TM), is used for the excitation of a TM mode guided in the waveguide, or completely transversely electrically polarized excitation light (TE) is used for the excitation of a TE mode guided in th
Danielzik Burkhard
Duveneck Gert Ludwig
Neuschafer Dieter
Pawlak Michael
Evans F. L.
Novartis AG
Wenderoth Lind & Ponack, LLP.
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