Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1996-11-25
1998-11-03
Le, Que
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
250214LS, 2504842, H01J 4014
Patent
active
058312595
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a high impedance electrooptical transducer. It more particularly applies to optical output sensors.
The sensors are components ensuring the input interface of various systems. They convert a quantity to be measured (e.g. chemical, mechanical or electromagnetic quantity) into a quantity directly usable by the data processing unit of such systems, i.e. an electrical or optical quantity.
Optical output sensors have the following recognized advantages:
However, the development of electrical output sensors remains more advanced.
However, consideration has been given to associating with an electrical output sensor an electrooptical transducer in order to obtain an optical output. For example, optical pressure sensors have been implemented by associating with a piezoelectric block or shim (mechanical sensor with electrical output) a light emitting diode, which then supplies an optical output.
The miniaturization of optical output sensors gives rise to sensitivity problems associated with the limitation of the available energy.
Thus, optical output microsensors generally only have the energy supplied by the signal to be measured (so-called autogenerating sensors) or a light energy supplied by a probe waveguide (so-called optosupplied sensors). The aforementioned pressure optical sensors are autogenerating.
Moreover, numerous optical output sensors are based on photoluminescence measurements (cf. document (1) which, like the other documents referred to hereinafter, is listed at the end of the description), the exciting light being transmitted to such a sensor by the same waveguide as that collecting the photoluminescence light. These optical output sensors are optically supplied.
However, the energy supplied by the signal to be measured is generally proportional with the sensor size. For example, the electrical energy supplied by a piezoelectric shim is proportional to the surface of the latter.
An electrooptical transducer to be associated with an electrical output microsensor (or itself used as an electrical sensor) must consequently consume very little electrical energy, which means that it must have a very high input impedance.
At present, the integrated electrooptical transducers having the highest input impedances are modulators based on the electrooptical effect. These transducers: manufacture, voltage of 10 V,
Electrooptical transducers known as luministors have been proposed and are based on photoluminescence variations of conductive polymers, which are due to the doping-dedoping (oxidation-reduction) induced by an electrical potential (cf. document (3)).
These transducers do not have to satisfy conditions a1) to a3) defined above. However: (above 5 pF) in order to obtain an adequate signal, Hertz.
SUMMARY OF THE INVENTION
The present invention relates to an electrooptical transducer not suffering from the disadvantages b1) and b2).
More specifically, the present invention relates to an electrooptical transducer incorporating an electrosensitive element exposed to the emission of a photoluminescence radiation when illuminated by an excitation radiation, said transducer being characterized in that the electrosensitive element comprises photoluminescent conjugate oligomers, which are exposed to a variation of their photoluminescence efficiency in the presence of an electrical field.
The electrooptical transducer according to the invention is based on the photoluminescence variations of a certain class of molecules (photoluminescent conjugate oligomers), when said molecules are exposed to an electrical field.
The transducer according to the invention has a much higher sensitivity than that of luministors (in which the molecules are not directly sensitive to the electrical field, but are instead sensitive to the presence of electrical charges).
It has an input capacitance of about 100 femtofarads and is able to allow frequencies above 1 GHz.
Thus, this transducer permits the production of optical output, optically supplied electrical sensors. It
REFERENCES:
CPEM '88 Digest, 7 Jun. 1988, Tsukuba, Ibaraki, Japan, pp. 89-90, Mahmoud A. El-Sherif, "On-Fiber Sensor and Modulator".
Commissariat a l''Energie Atomique
Le Que
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