We describe an uncooled IR camera that is based on a Fabry-Perot Interferometer (FPI) IR-to-visible transducer. The
FPI-based IR camera converts a thermal-IR image to a video electronic image. IR radiation, emitted by an object in the
scene, is imaged onto an IR-absorbing material that is located within an FPI. Spatial variations in temperature of the scene
translate into corresponding temperature variations in the IR-absorbing material, forming a temperature image in the FPI.
Within the FPI, the temperature variations produce variations in optical thickness for any beam of collimated visible light
that is reflected from the FPI. The intensity of visible light reflected by the FPI is a function of optical thickness and thus
forms an image, with thickness variations translating into intensity variations. The reflected light traverses visible optics
that image the IR-absorbing material onto a visible-detector array, where the reflected light is converted into an electronic
image. We will describe in detail the various sources of noise that determine the noise-equivalent temperature difference
(NETD) of an FPI-based infrared camera. The dominant sources of noise are (1) shot noise in the visible-detector array
and (2) temperature fluctuations (thermal noise) in the transducer. For a typical CCD array, we project a total NETD
of approximately 40-50 mK for an FPI-based IR camera that is configured so that shot and thermal noise contribute
approximately equally to the noise.
Laser induced formation of CO2 and desorption of O2 are initiated with femtosecond and picosecond laser excitation of a Pt(111) surface prepared with coadsorbed CO and O2 at 90 K. The nonlinear fluence dependent reaction yields were measured for 267, 400, and 800 nm wavelengths, and for pulse durations from 80 fs to 3.6 ps. Two-pulse correlation experiments measuring total O2 desorption yield versus time delay between 80 fs pulses show a 0.9 ps HWHM central peak and a slower 0.1 ns time-scale. At 267 nm the relative yields of O2 and CO2 are found to depend on fluence. Comparison of results at different wavelengths and pulsewidths shows that nonthermalized surface electrons play a role in the laser-induced surface chemistry.
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