Fig. 1 Light-Current-Voltage characteristics of a 3-mm-long single
ICL emitter with HR/AR coatings in the CW regime at
20oC; inset: the emission spectra at
2Ith.
Figure 1 shows the light-current-voltage (L-I-V) characteristics of a
3-mm-long ICL single emitter with HR/AR coatings. At 20℃, the threshold
current density is 220 A/cm2 and the slope efficiency
near the threshold is 800 mW/A. The maximum WPE reaches 12.3%. These
values are close to the previous report on ICLs with the highest CW
output power [10]. The CW output power of the single ICL emitter was
measured up to 320 mW at the injection current density of 1.35
kA/cm2, where the WPE is 10.5%. There has been no
obvious thermal rollover in the L-I characteristics. As shown in the
inset of Fig. 1, the emission spectrum recorded at 2Jthinjection current density is centered at 3.39 μm, which is consistent
with our design.
The three-emitter arrays were mounted epilayer-down on diamond submounts
for efficient heat extraction from the laser chips, which were bonded on
copper heat sinks. Figure 2 shows the CW L-I-V characteristics of an ICL
array sample. Measurements were taken at the heat sink temperature of
10℃. The threshold current density and the slope efficiency near the
threshold are 170 A/cm2 and 880 mW/A, comparable to
the values measured from a single emitter at 10℃. The output power was
measured up to 1.01 W at an injection current of 1.7 A (1.15
kA/cm2). Again, there is no thermal rollover in the
L-I characteristics, indicating a potentially higher maximum output
power. The maximum WPE and the WPE at the maximum injection current are
14.4% and 12.9%, respectively.