Abstract
Light emitting diodes (LEDs) and laser diodes are the focus of this chapter. For LEDs materials choices, the concepts of internal and external quantum efficiency as well as device design are treated. Special devices such as white LEDs, quantum dot and organic LEDs are introduced. For laser diodes the concepts of gain, loss and threshold, various heterostructures for modern device design and laser emission properties such as mode spectrum, far field, dynamics and tunability are discussed. Finally special devices such as the hot hole laser, the cascade laser and semiconductor optical amplifiers are mentioned.
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsNotes
- 1.
A solid angle \(\varOmega \) is the ratio of the spherical surface area A and the square of the sphere’s radius r, i.e. \(\varOmega =A/r^2\).
- 2.
The \(V(\lambda )\) curve has been experimentally determined by letting several observers adjust (decrease) the perceived brightness of a monochromatic light source at 555 nm to that of light sources of the same absolute radiation power at other wavelengths with so-called heterochromatic flicker photometry. The ‘relative sensitivity curve for the CIE Standard Observer’ was determined in 1924. The ‘standard observer’ is neither a real observer nor an average human observer. The curve has shortcomings, e.g., due to the used spectral band width (20–30 nm) of the light sources and the comparison of spectral power instead of the photon flux.
- 3.
While photopic vision is due to cones, the scotopic (dark-adapted) vision is due to rods. Rods are more than one thousand times as sensitive as the cones and can reportedly be triggered by individual photons under optimal conditions. Rods predominate in the peripheral vision and are not color sensitive.
- 4.
Commission Internationale de l’Éclairage. The color space can be described by different coordinate systems, and the three most widely used color systems, Munsell, Ostwald, and CIE, describe the color space with different parameters. The Munsell system uses hue, value, and chroma and the Ostwald system uses dominant wavelength, purity, and luminance. The more precise CIE system uses a parameter Y to measure brightness and parameters x and y to specify the chromaticity that covers the properties hue and saturation on a two-dimensional chromaticity diagram.
- 5.
This definition is motivated by the color vision of the eye. Two light sources will have the same color, even if they have different SPDs, when they evoke the same color impression to the human eye.
- 6.
The coloring of the chart is provided for an understanding of color relationships. CRT monitors and printed materials cannot reproduce the full gamut of the color spectrum as perceived in human vision. The color areas that are shown only depict rough categories and are not precise statements of color.
- 7.
RGB is an additive color system. However, printing devices use a subtractive color system. This means that the ink absorbs a particular color, and the visible impression stems from what is reflected (not absorbed). When inks are combined, they absorb a combination of colors, and hence the reflected colors are reduced, or subtracted. The subtractive primaries are cyan, magenta and yellow (CMY) and are related to RGB via \((C,M,Y)=(1-R,1-G,1-B)\).
- 8.
Standard RGB color space as defined mainly by Hewlett-Packard and Microsoft, almost identical to PAL/SECAM European television phosphors.
- 9.
National television standard colors, US norm.
- 10.
This transition is dipole allowed for Ce and partially forbidden for Eu.
- 11.
Penetration of white LEDs into the general lighting market could translate (globally) into cost savings of $\({~}10^{11}\) or a reduction of power generation capacity of 120 GW.
- 12.
Note that the light extraction efficiency is also important for solar cells, cf. Sect. 22.4.3.
- 13.
The term ‘laser’ is an acronym for ‘light amplification by stimulated emission of radiation’. The amplification relies on stimulated emission, theoretically predicted by Einstein in 1917. The laser concept was first explored in the microwave wavelength region (1954, MASER using ammonia, Ch.H. Townes, Nobel prize 1964). The first optical laser (1958, US patent No. 2,929,922 awarded 1960, A.L. Schawlow, Ch.H. Townes) was the ruby laser developed in 1960 by Th. Maiman. A device is a laser when it emits stimulated light. This light must neither be monochromatic nor be emitted in a narrow, directed beam.
- 14.
Or etched facets in possibly any direction.
- 15.
Such external cavities can be used for manipulation of the laser properties such as wavelength tuning.
- 16.
16 million 405 nm laser diodes were shipped in 2006–2008. 85 % of those are built into SONY’s PS3, the rest into HD-DVD and other Blu-ray™disc (BD) players.
- 17.
Or due to optical pumping. If electrical contacts are not available, the laser action can be invoked by supplying a high-intensity light beam, possibly in a stripe-like shape. For optically pumped semiconductor lasers see Sect. 23.4.15.
- 18.
One electron and one hole band are considered; the heavy and light hole bands are taken into account via the mass according to (6.69).
- 19.
A smaller band gap coincides for many cases with a larger index of refraction.
- 20.
Since \(T_0\) has the dimension of a temperature difference, it can be expressed in \(^{\circ }\)C or K. For the sake of unambiguity it should be given in K.
- 21.
In order to make better use of the high bandwidth of the optical fiber several information channels with closely lying wavelengths are transmitted.
- 22.
Note the anomalous positive coefficient \(\mathrm {d}E_{\mathrm {g}}/ \mathrm {d}T\) as discussed in Sect. 6.7.
- 23.
This term can be multiplied by the injection efficiency \(\eta _{\mathrm {inj}}\) to account for leakage currents.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2016 Springer International Publishing Switzerland
About this chapter
Cite this chapter
Grundmann, M. (2016). Electricity-to-Light Conversion. In: The Physics of Semiconductors. Graduate Texts in Physics. Springer, Cham. https://doi.org/10.1007/978-3-319-23880-7_23
Download citation
DOI: https://doi.org/10.1007/978-3-319-23880-7_23
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-23879-1
Online ISBN: 978-3-319-23880-7
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)