4.2 Principles of Light-Emitting Diodes (LEDs)
165
1520
1560
1600
0
4
6
1
0
8
4
1
Wavelength (nm)
Peak wavelength (1546 nm)
Spectral widths
broaden with
increasing wavelength
FWHM
Fig. 4.13 Typical spectral patterns for edge-emitting and surface-emitting LEDs at 1310 nm. The
patterns broaden with increasing wavelength and are wider for surface emitters
Table 4.2 Typical characteristics of surface-emitting and edge-emitting LEDs
LED type
Material
Wavelength
(nm)
Operating
current (mA)
Fiber-coupled
power (μW)
Nominal
FWHM (nm)
SLED
GaAlAs
850
110
40
35
ELED
InGaAsP
1310
100
15
80
SLED
InGaAsP
1310
110
30
150
Drill Problem 4.3 An important parameter of GaAs is the value of its refractive
index as a function of wavelength. For the range λ = 0.89 to 4.1 μm the
refractive index is given by
n
2
= 7.10 +
3.78λ
2
λ 2 − 0.2767
where λ is given in micrometers. Compare the refractive indices of GaAs at
810 nm and 900 nm [Answer: n = 3.69 at 810 nm and 3.58 at 900 nm.]
165
1520
1560
1600
0
4
6
1
0
8
4
1
Wavelength (nm)
Peak wavelength (1546 nm)
Spectral widths
broaden with
increasing wavelength
FWHM
Fig. 4.13 Typical spectral patterns for edge-emitting and surface-emitting LEDs at 1310 nm. The
patterns broaden with increasing wavelength and are wider for surface emitters
Table 4.2 Typical characteristics of surface-emitting and edge-emitting LEDs
LED type
Material
Wavelength
(nm)
Operating
current (mA)
Fiber-coupled
power (μW)
Nominal
FWHM (nm)
SLED
GaAlAs
850
110
40
35
ELED
InGaAsP
1310
100
15
80
SLED
InGaAsP
1310
110
30
150
Drill Problem 4.3 An important parameter of GaAs is the value of its refractive
index as a function of wavelength. For the range λ = 0.89 to 4.1 μm the
refractive index is given by
n
2
= 7.10 +
3.78λ
2
λ 2 − 0.2767
where λ is given in micrometers. Compare the refractive indices of GaAs at
810 nm and 900 nm [Answer: n = 3.69 at 810 nm and 3.58 at 900 nm.]