Carbon single-wall nanotubes (SWNTs) are studied as the thermal-absorption coating on a large area pyroelectric detector. The SWNTs were produced by a laser vaporization method and dispersed onto the detector surface by use of a simple airbrush technique. The detector was based on a 1-cm-diameter, 60-μm-thick lithium tantalate disk having nickel electrodes. We report the spectral responsivity of the detector ranging from 600 to 1800 nm, as well as the spatial and directional uniformity at 850 nm. Using Drude and Lorentzian dielectric functions and an effective medium approximation to obtain the indices of refraction of semiconductor and metallic SWNTs, we compared the expected theoretical relative responsivity for the two types of tube with the measured relative responsivity of the detector. Values of thermal conductivity, specific heat, and damage threshold obtained from the literature are compared with properties of alternatives for thermal coatings such as gold-black and carbon-based paint.

Single-wall carbon nanotube coating on a pyroelectric detector.

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Single-wall Carbon Nanotube Coating on a Pyroelectric Detector

An electrically calibrated optical detector has been developed using a pyroelectric response of the plastic, polyvinylfluoride. An in-depth look at the modulation frequency response was performed to substantiate the equivalence of the optical and electrical inputs, indicate the optimum structure and allow for a clearer understanding of the device limitations. The experimental results of the dynamic range, linearity, uniformity, and detectivity confirm the device’s utility.

Electrically Calibrated Pyroelectric Optical-Radiation Detector

Electrically calibrated pyroelectric optical-radiation detector

Laser power and energy measurements are commonly made in calorimeters operating in a constant temperature environment. Calorimeters of this type are analyzed in terms of the first law of thermodynamics and the boundary value problem describing heat flow in the calorimeter. This theory of the measurement suggests design features of the calorimeter, sources of error to be avoided in design and operation, and tests to demonstrate experimentally the adequacy of the design. The analysis shows how time—temperature data can be used to allow for the temperature gradient on the calorimeter and the heat exchange due to transients in the temperature.

Theory of Isoperibol Calorimetry for Laser Power and Energy Measurements

Principles and detailed procedures are described for measuring laser energy and power in terms of electrical energy based on voltage, resistance, and frequency standards. The construction of a small isoperibol calorimeter used for the measurements is described. The calorimeter will accommodate 0.01 to 20 J and 4 × 10-5 to 1 W cw and is limited to a maximum pulse intensity of 0.1 J/cm2. The standard deviation of comparison measurements using two calorimeters and a beam splitter is 0.08 percent when the smaller energy input is not less than 0.3 J. The estimated limits of systematic error for one calorimeter are ± 1.0 percent of the laser energy measured by the calorimeter.

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W.E. Case

Papers

A Reference Calorimeter for Laser Energy Measurements.