Environmental optoelectronic gas sensors operating in the mid-IR spectral range (3-5 µm)
Zotova N., Karandashov S., Matveev B., Remennyi M., Stus' N., Talalakin G., Aleksandrov S., Gavrilov G., Sotnikova G.
A.F. Ioffe Physico-Technical Institute, 194021 St Petersburg, Russia
Optoelectronic sensors are composed from optically coupled light emitting diode (LED)-photodetector (PD) pairs which measure gas absorption at specific wavelengths in the mid-IR. LEDs and detectors for these sensors are fabricated by original methods which are covered by Russian invention certificates and published in scientific papers. Table 1 presents parameters of several typical sensors in which optical connection is made by spherical mirror having radius of curvature of 2 cm and diameter of 2 cm. The space between LED and detector is a gas cuvette
Table 1
| N |
 max and LED structure |
Ppulse, mW |
p and photodetector structure |
D*, cm Hz1/2/W |
Limit of detection at a single LED pulse |
| 1. |
3.3 µm, (n)InGaAs/ (p)InGaAs/ (p)InAs |
5-10 |
3.3 µm, (p)InAsSbP/ (n)InAs |
2·109 |
0.017 % v/v CH4, at t=1 µs |
| 2. |
4.3 µm, (p)InAsSb/ (n)InAsSb/ (n)InAsSbP |
2 |
3.9 µm, PbSe |
5·108 |
0.75 % v/v CO2, at t=30 µs |
| 3. |
4.7 µm, (p)InAsSb/ (n)InAsSb/ (n)InAsSbP |
1 |
3.9 µm, PbSe |
5·108 |
3 % v/v CO, at t=30 µs |
| 4. |
5.3 µm, (p)InAsSb/ (n)InAsSb/ (n)InAsSbP |
0.05 |
5.3 µm, (p)InAsSb/ (n)InAsSb/ (n)InAsSbP |
3·108 |
(Nox) |
The above sensors can be used for personal (N 1,2), diagnostic of car exhaust (N 1,2,3), in chemical (N 1-5) and food (N 1,2) industry, for inroom carbon dioxide (N 2) etc.
Totally diode sensors (N 1) are superior to lead selenide based ones in terms of time response and at high temperatures (t=80-180°C) and thus can be used for hydrocarbon monitoring in metallurgical industry and energy and heat production.
Sensors construction is covered by Russian patent (Useful Model N 5455). Patent is pending (Russian Patent application from 27.04.99) on LED construction. In both cases the owners of the patents are the authors of the inventions.
All sensors presented in the Table 1 have been successfully tested in several EEC research centers. Carbon dioxide sensor (N 2) was also tested by Russian Certificate Center and released for personal gas analyzer GIAM-302 for the measurement in the 0.2-2 %v/v range at t= -40 +40°C. At present the analyzer is produced in small quantities for Russian customers.
The developed sensors have long lifetime (>30000 hrs [1]), fast response and have higher than analogs limit of detection due to narrow LED spectral width [2] and high photodiode detectivity [1].
References
- B.Matveev et al "Room temperature InAs photodiode-InGaAs LED pairs for methane detection in the mid-IR" Sensors & Actuators Vol. 51(1998), Nos. 1-3, pp. 233-2371.
- 2. B.Matveev et al "InAsSbP/InAs LEDs for the 3.3-5.5 µm spectral range" IEE Proceedings, Optoelectronics Vol 145 (5), pp. 254-256 (1998)
|
