Research Journal of Applied Sciences, Engineering and Technology 7(8): 1598-1602, 2014
ISSN: 2040-7459; e-ISSN: 2040-7467
© Maxwell Scientific Organization, 2014
Submitted: May 21, 2013
Accepted: June 12, 2013
Published: February 27, 2014
Investigating a Hypothetical Semiconductor Laser Bar with a Damaged Single Emitter
Using a Laser Diode Simulation/Emulation Tool
1, 2
C.K. Amuzuvi and 1J.C. Attachie
Department of Electrical and Electronic Engineering, University of Mines and Technology,
Tarkwa, Ghana
2
Photonic and Radio Frequency Engineering Group (PRFEG), Electrical Systems and Optics Research
Division, Faculty of Engineering, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
1
Abstract: This study demonstrates the use of Barlase, a semiconductor laser diode emulation tool, to emulate the
by-emitter degradation of high power semiconductor laser diodes. Barlase is software that uses a LabView control
interface. In this study, a hypothetical laser diode bar (multiple emitters) was used to investigate a damaged single
emitter randomly located in the bar and its behavior analyzed within the bar. It should however, be noted that, this
scenario is valid for devices at the start of the aging process only. When all other relevant effects that affect the
performance of laser diodes bars are allowed to interact over time, high levels of defects can also play important role
in the degradation process. The results of this simulation scenario show the successful implementation of Barlase in
the by-emitter analysis of laser diodes.
Keywords: Band gap energy, by-emitter, defect, degradation, emitter, nonradiative recombination, quantum well,
slope efficiency, temperature, threshold current
INTRODUCTION
MATERIALS AND METHODS
Due to several applications emerging in the use of
high-power laser bars (Steel, 2008), there is a greater
demand on their improved reliability and durability.
Apart from their traditional applications such as
pumping solid-state lasers, material processing (Schulz
and Poprawe, 2000), printing, medicine and
entertainment; they have found other uses in the light
detection and ranging and free space optical
communications (Chazan et al., 1998).
Barlase presents an attempt to understand further,
the by-emitter degradation analysis technique
developed over recent years (Xia et al., 2002; Tomm
et al., 2002; Bull et al., 2005; Lim et al., 2007, 2009,
2005; Bream et al., 2006). The tool is an addition to the
by-emitter analysis technique where the effects of
certain factors that affect the degradation of laser
emitters/bars can be investigated.
In this study, Barlase (Amuzuvi and Attachie,
2013) is used to perform a by-emitter analysis of a laser
bar when an emitter within the bar is damaged. The
objective of this study is to investigate and analyze
various scenarios of defects in the operation of a laser
bar, especially if there is a localized defect like a
defective emitter within the bar.
Bars are made up of multiple emitters and therefore
there was a need to find an innovative way to include
the interactions between individual emitters within the
bar. This gave rise to the Barlase concept (Fig. 1),
where a bar is considered as a monolithic block of
multiple emitters connected in parallel with each other
with a common voltage connected across them, Fig. 2
(Amuzuvi, 2013).
Each emitter is biased with a common voltage, but
the emitter currents and powers change depending on
the details of the individual emitters and their
environment.
RESULTS AND DISCUSSION
In Amuzuvi and Attachie (2013), Barlase was used
to investigate a practical scenario, where a laser bar has
a random low-level of defects distributed across the bar.
In this study, another practical scenario is being
investigated where one random emitter has a high level
of defects. The bar being considered is the same as in
Amuzuvi and Attachie (2013), an (8) emitter bar
(Fig. 2). Emitter #3 was randomly selected to represent
a “damaged” emitter. The level of defects introduced in
Corresponding Author: C.K. Amuzuvi, Department of Electrical and Electronic Engineering, University of Mines and
Technology, Tarkwa, Ghana
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Res. J. Appl. Sci. Eng. Technol., 7(8): 1598-1602, 2014
New Ibar
Newton’s Method
Calculates new ∆V
No
Yes
Ibar / Field
converged?
Em1 Em2 Em3 Em4 Em5 Em6 Em7 Em8
Exit
One roundtrip propagation
Fig. 1: Flow chart showing the communication between emitters in Barlase
Ibar
I1
I2
I3
I4
I5
I6
I7
I8
Ibar
Fig. 2: The representation of an eight emitter laser bar
Table 1: Values of QW trap densities assigned to each emitter in the
bar
Emitter number
Trap density (cm-3)
1
2.00×1015
2
2.00×1015
3
2.00×1016
4
2.00×1015
5
2.00×1015
6
2.00×1015
7
2.00×1015
8
2.00×1015
emitter #3 was chosen to be 2×1016 cm-3 - an order of
magnitude higher than that found in the other 7
emitters. Again, multi-emitter simulations were carried
out in constant current mode for bar currents of 2, 4, 6,
8 and 10 A. Table 1 indicates the levels of QW trap
densities assigned to each emitter in the bar.
Figure 3 shows the P-I characteristic of the bar
together with the P-I and P-V characteristics of each of
the individual emitters. The threshold current and slope
efficiency for the bar are also shown as legend in
Fig. 3a. The threshold current and slope efficiency have
been calculated for each individual emitter from the
emitter P-I curves in Fig. 3b. Figure 3c also shows the
power versus individual emitter voltages. The
variations of apparent threshold/threshold current and
apparent slope/slope efficiency of individual emitters
are plotted as a function of emitter number in Fig. 4.
The P-I curve of the emitter with the high level of
defects is lower than that of the other emitters, as
expected. The threshold current in emitter number 3 is
16% higher, whilst the slope efficiency is only 0.25%
lower compared to the other emitters.
Figure 5 shows the distribution of current, power
and maximum QW temperature for each emitter across
the bar for a total bar current of 2 A. Figure 6 shows the
same quantities for a total bar current of 10 A. From
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Res. J. Appl. Sci. Eng. Technol., 7(8): 1598-1602, 2014
8 Threshold Current = 0.606 A
(a)
Slope Efficiency = 0.904 W/A
Emitter Power, W
Bar Power, W
6
5
4
3
2
(b)
Emitters 1,2,4,5,6,7,8
Emitter 3
1.0
7
0.8
0.6
0.4
0.2
1
0
0
2
4
6
8
0.0
0.0
10
0.2
0.4
Bar Current, A
1.0
Emitter Power, W
0.9
0.8
0.7
0.6
0.5
0.6
0.8
1.0
1.2
1.4
Emitter Current, A
Emitter Number
1
2
3
4
5
6
7
8
(c)
0.4
0.3
0.2
0.1
0.0
1.40
1.44
1.48
1.52
1.56
Voltage, V
Fig. 3: (a) Bar power-current characteristics, (b) power-current characteristics of the individual emitters, (c) power versus
individual emitter voltage
(a)
QW Trap Density, cm-3
2.0x1016
1.5x1016
1.0x1016
5.0x1015
Threshold Current, A
0.0
0.28
(b)
0.24
0.20
Threshold Current
Apparent Threshold Current
0.16
0.12
Slope Efficiency, W/A
0.08
0.906
(c)
0.904
0.902
0.900
Slope Efficiency
Apparent Slope Efficiency
0.898
x9
0.896
1
2
3
4
5
6
7
8
Emitter Number
Fig. 4: (a) QW trap densities assigned to each emitter, (b) variation of apparent threshold/threshold current, (c) apparent
slope/slope efficiency of individual emitters
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Res. J. Appl. Sci. Eng. Technol., 7(8): 1598-1602, 2014
Emitter Current, A
0.2525
(a)
0.2520
0.2515
0.2510
0.2505
Bias Current = 2 A
0.2500
Emitter Power, W
0.2495
0.20
(b)
0.18
0.16
0.14
Maximum QW Temperature, K
0.12
Bias Current = 2 A
0.10
306.4
(c)
306.2
306.0
305.8
305.6
305.4
305.2
Bias Current = 2 A
305.0
1
2
3
4
5
6
7
8
Emitter Number
Fig. 5: (a) Distribution of the emitter currents, (b) emitter powers, (c) maximum emitter QW temperatures across the bar at a total
bar bias current of 2 A
(a)
Emitter Current, A
1.4
1.2
1.0
0.8
Bias Current = 10 A
0.6
(b)
Emitter Power, W
1.1
1.0
0.9
0.8
0.7
Maximum QW Temperature, K
0.6
Bias Current = 10 A
0.5
347.4
(c)
347.2
347.0
346.8
Bias Current = 10 A
346.6
1
2
3
4
5
6
7
8
Emitter Number
Fig. 6: (a) Distribution of the emitter currents, (b) emitter powers, (c) maximum emitter QW temperatures across the bar at a total
bar bias current of 10 A
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Res. J. Appl. Sci. Eng. Technol., 7(8): 1598-1602, 2014
these graphs, the relationship between the current,
power and maximum QW temperature of the emitter
with the high level of defects can be seen to be different
in comparison to the standard emitters. The higher level
of defects in emitter number 3 causes its current to be
0.35% higher, its output power to be 1.0% lower and its
maximum QW temperature to be just over 0.5 K greater
than the other emitters.
Barlase has therefore been used in this scenario to
gain more knowledge and insight into the interaction
between emitters in a laser bar when defective emitters
are present in the bar.
CONCLUSION
The variations in the operating condition and
environments of the individual emitters were seen to
affect the performance of the other emitters and of the
bar as a whole. This scenario investigated using Barlase
demonstrates the effect that a damaged emitter will
have on a laser bar via the distribution of power and
current competition within the bar. From this scenario,
the capabilities of Barlase has clearly been investigated
and demonstrated, indicating the increase in
temperature and the corresponding decrease in power
when a damaged emitter is present in a bar.
ACKNOWLEDGMENT
CKA thanks the University of Mines and
Technology, Tarkwa, Ghana and the GetFund for their
support.
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