THORLABS SLS303, Руководство пользователя

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Stabilized Benchtop IR Light Source Chapter 3: Product Overview
Rev B, August 4, 2021
Page 3
Chapter 3 Product Overview
3.1. Planck's Law and Blackbody Radiation
A black body is an object that absorbs all incident electromagnetic radiation (e.g. light), no light passes through or
is reflected. However, despite the name, a black body will also emit electromagnetic radiation. The radiation of a
black body in thermal equilibrium is described by Planck’s Law:
𝐼𝐼 ( 𝜆𝜆 , 𝑇𝑇 ) =
2 𝜋𝜋ℎ𝑐𝑐
2
𝜆𝜆
5
1
𝑒𝑒
ℎ𝑐𝑐
𝜆𝜆𝜆𝜆𝜆𝜆
�
− 1
Where I is the radiated power per unit area of emitting surface per unit wavelength at temperature T ; K is the
Boltzmann constant,
h
is the Planck constant,
c
is the speed of light.
By measuring the spectrum of the blackbody radiation, we can calculate the temperature of this black body.
Figure3.1 shows the radiated power per unit area I as a function of wavelength at various temperature.
Figure 3.1 Blackbody radiation at different temperatures
In real life, broadband light sources may vary widely from the ideal black body in terms of the frequency and intensity
of the light emitted. By comparing the light source to an ideal black body at a given temperature, one can
characterize the light source by the temperature of the black body radiator which has the same chromaticity, which
is known as the color temperature of the light source.
3.2. Silicon Nitride Globar
The Globar is a rod of silicon nitride with >99% purity. It comprises a high-resistance hot zone and low-resistance
cold end(s). A passage of current causes the high-resistance hot zone to heat, reaching a temperature of about
1200 Kelvin.
Figure 3.2: A Silicon Nitride Globar
At this temperature, the Globar generates light radiation mostly in the IR region. Figure 3.3 shows a typical output
spectrum of the SLS303 measured from 1000 to 5600 nm, compared to an ideal back body radiation at 1200 K.
The actual output of the SLS303 may extend to over 15 µm.
Hot zone