Infrared radiation sources, sensors and source combinations, and methods of manufacture

1. A narrow band incoherent radiation emitter/detector comprising:

a planar filamental emission/detection element characterized by a predetermined spectral range of emitted/detected radiation and a emission/detection width dl/l less than about 0.1, where l is the wavelength of said radiation.

2. An emitter/detector according to claim 1 wherein said spectral range includes relatively long wavelengths and excludes relatively short wavelengths.

3. An emitter/detector according to claim 1 wherein said spectral range is near an infrared absorption line of a predetermined material.

4. An emitter/detector according to claim 1 wherein said spectral range excludes relatively long wavelengths and relatively short wavelengths and includes a range of intermediate wavelengths therebetween.

5. An emitter/detector according to claim 4 , wherein said emission/detection width is substantially determined by surface features of said emission/detection element, further comprising a detector for photons characterized by a wavelength within said intermediate range.

6. A gas detector comprising:

A) a planar filamental emission/detection element characterized by a predetermined spectral range of emitted/detected radiation and a emission/detection width dl/l less than about 0.1, where l is the wavelength of said radiation, said emission/detection element having an input/output axis, and

B). a first reflector disposed along said input/output axis and opposite to said emission/detection element, whereby an optical path is defined from said emission/detection element to said first reflector to and back to said emission/detection element, wherein said optical path between said emission/detection element and said first reflector passes through a gas test region.

7. A gas detector according to claim 6 , further comprising:

C). a driver for driving said emission/detection element to emit radiation propagating along said optical path toward said first reflector.

8. A gas detector according to claim 6 further comprising:

D). a processor responsive to said emission/detection element for generating an output signal representative of radiation incident thereon.

9. A gas detector according to claim 6 wherein said spectral range includes a wavelength corresponding to an absorption line of a predetermined gas.

10. A gas detector according to claim 6 further comprising:

a second reflector extending from points near said emission/detection element along said input/output axis,

wherein said second reflector is disposed along said optical path, whereby said optical path extends from said emission/detection element to said second reflector to said first reflector to said second reflector to said emission/detection element, and

wherein said optical path between said second reflector and said first reflector passes through said gas test region.

11. A gas detector comprising:

A) a planar filamental emission element characterized by a predetermined spectral range of emitted radiation and an emission width dl/l less than about 0.1, where l is the wavelength of said emission element having an output axis,

B) a first reflector disposed along said output axis, and

C) a planar filamental detection element characterized by a predetermined spectral range of detected radiation and a emission/detection width dl/l less than about 0.1, where l is the wavelength of said detection element having an input axis, whereby an optical path is defined from said emission element to said first reflector and to said detection element, wherein said optical path between said emission element and said first reflector, or between said first reflector and said detection element or both, passes through a gas test region.