Skip to main content
Engineering LibreTexts

7.4: Relationship Between Devices

  • Page ID
    18982
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    7.4.1.png
    Figure \(\PageIndex{1}\): Devices which convert between electricity and light can be classified based on whether they involve absorption, spontaneous emission, or stimulated emission. Thick borders indicate categories of devices while thin borders indicate example types of devices.
    7.4.2.png
    Figure \(\PageIndex{2}\): Devices which convert between electricity and light can be classified based on the type of active material. Thick borders indicate categories of devices while thin borders indicate example types of devices.

    Scientists have come up with a wide variety of devices that convert between electricity and light, and they have come up with a wide variety of applications for these devices. Covering all such devices and all their applications is beyond the scope of this text. However, this chapter has shown some of the variety of devices. One way to classify devices which convert between electricity and light is to group them into categories based on whether they primarily involve absorption, spontaneous emission, or stimulated emission. Figure \(\PageIndex{1}\) illustrates how to classify many of the devices discussed in this chapter in this way. Ovals indicate absorption, rounded rectangles indicate spontaneous emission, and rectangles indicate stimulated emission. In the figure, thick borders indicate categories of devices while thin borders indicate example types of devices. Dotted lines indicate devices with gaseous active materials, dashed lines indicate semiconducting active materials, mixed dotted and dashed lines indicate solid state active materials, widely spaced dotted lines indicate conductive active materials, and solid lines indicate mixed or other active materials.

    This diagram is far from complete because many other categories of devices exist, and these categories may be broken into further subcategories. Furthermore, only a handful of example devices are shown relating to some of the specific devices discussed above. This diagram includes absorption based devices discussed in Chapter 6. It also includes antennas discussed in Chapter 4. Light is a form of electromagnetic radiation with frequencies in the visible range. Light can be absorbed by a solar cell and spontaneously emitted by an LED, for example. Similarly, electromagnetic waves at longer wavelengths can be absorbed or spontaneously emitted by antennas which are devices with conductive active materials.

    A dierent way of classifying devices which convert between electricity and light is to classify them based on the type of active material. All of these devices involve the interaction of light and atoms. The atoms involved may be part of a gas, may be dopants inside an insulating solid, may be part of a bulk semiconductor material, or may be part of a conductive solid. This way of classifying devices is illustrated in the Fig. \(\PageIndex{2}\). Dotted lines indicate devices with gaseous active materials, dashed lines indicate semiconducting active materials, mixed dotted and dashed lines indicate solid state active materials, widely spaced dotted lines indicate conductive active materials, and solid lines indicate mixed or other active materials. As in the previous figure, ovals indicate absorption, rounded rectangles indicate spontaneous emission, and rectangles indicate stimulated emission. Antennas are shown twice in the conductor based devices category because receiving antennas involve absorption while transmitting antennas involve spontaneous emission. Also as in the previous gure, thick borders indicate categories of devices while thin borders indicate example types of devices. Again, this figure does not show a complete list of all possible devices or device categories, but it does illustrate relationships between some devices discussed in this chapter.

    Devices are usually designed to involve only one of these processes of absorption, spontaneous emission, or stimulated emission. However, it is possible for multiple of these processes to occur in a single device depending on how it is operated. For example, a semiconductor laser converts electricity to light by stimulated emission when current above the lasing threshold is supplied. If a weaker current is supplied, the device will act as an LED which converts electricity to light by spontaneous emission. If light shines on the device and the voltage across the device is measured, the same device acts as a photodetector which converts light to electricity by absorption. Similarly, photomultiplier tubes, gas discharge lamps, and gas lasers all involve tubes of gas with electrodes to supply or measure electricity. Like many energy conversion devices, these devices may convert electricity to light when operated in one direction and convert light to electricity when operated in reverse.


    This page titled 7.4: Relationship Between Devices is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Andrea M. Mitofsky via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.