674
23 Electricity-to-Light Conversion
Fig. 23.48 Optical power (experimental data and modelling) in the dominant mode of a single-mode GaAs laser diode
(Hitachi HLP 1400) as a function of voltage (in pulsed operation in order to avoid heating effects) around the threshold
voltage V th . Adapted from [1992]
(a)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
I r
(b)
InGaAs/
GaAs
Fig. 23.49 a Typical P–I characteristic of a semiconductor laser. Adapted from [574]. b Output power and total quantum
efficiency of a quantum dot laser (3 stacks of InGaAs/GaAs QDs, L = 2 mm, w = 200 µm, λ = 1100 nm, T = 293 K)
versus injection current
voltage barriers), optical losses, Joule heating, spontaneous emission and carrier leakage. It seems
possible to achieve η w of 80%.
The P–I characteristic is not linear to arbitrary high currents. Generally, the output power will
saturate or even decrease for increasing current. These effects can be due to increasing leakage current, increasing internal loss at high current or temperature effects, e.g. an increase of threshold with
increasing temperature (cf. Sect. 23.4.9) and therefore a reduction of total efficiency. All nonradiative
losses will eventually show up as heat in the laser that must be managed with a heat sink.
A radical effect is catastrophic optical damage (COD) at which the laser facet is irreversible
(partially) destructed. Antioxidation or protective layers can increase the damage threshold to >
20 MW/cm
2 . The record power from a single edge emitter is ∼ 12 W (200 µm stripe width). For a
lateral monomode laser, cw power of about 1.2 W has been reached from a 1480-nm InGaAsP/InP
double quantum-well lasers with 3–5 µm stripes and 3 mm cavity length [1996]. About 500 mW can
be coupled into a single-mode fiber [1997].
23 Electricity-to-Light Conversion
Fig. 23.48 Optical power (experimental data and modelling) in the dominant mode of a single-mode GaAs laser diode
(Hitachi HLP 1400) as a function of voltage (in pulsed operation in order to avoid heating effects) around the threshold
voltage V th . Adapted from [1992]
(a)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
I r
(b)
InGaAs/
GaAs
Fig. 23.49 a Typical P–I characteristic of a semiconductor laser. Adapted from [574]. b Output power and total quantum
efficiency of a quantum dot laser (3 stacks of InGaAs/GaAs QDs, L = 2 mm, w = 200 µm, λ = 1100 nm, T = 293 K)
versus injection current
voltage barriers), optical losses, Joule heating, spontaneous emission and carrier leakage. It seems
possible to achieve η w of 80%.
The P–I characteristic is not linear to arbitrary high currents. Generally, the output power will
saturate or even decrease for increasing current. These effects can be due to increasing leakage current, increasing internal loss at high current or temperature effects, e.g. an increase of threshold with
increasing temperature (cf. Sect. 23.4.9) and therefore a reduction of total efficiency. All nonradiative
losses will eventually show up as heat in the laser that must be managed with a heat sink.
A radical effect is catastrophic optical damage (COD) at which the laser facet is irreversible
(partially) destructed. Antioxidation or protective layers can increase the damage threshold to >
20 MW/cm
2 . The record power from a single edge emitter is ∼ 12 W (200 µm stripe width). For a
lateral monomode laser, cw power of about 1.2 W has been reached from a 1480-nm InGaAsP/InP
double quantum-well lasers with 3–5 µm stripes and 3 mm cavity length [1996]. About 500 mW can
be coupled into a single-mode fiber [1997].