Biomedical Engineering Reference
In-Depth Information
from 100 μm aperture devices in TO can packages and up to 1 W from a sin-
gle device in a larger package. The devices have narrow linewidths of tens
of kilohertz and SMSR of >30 dB. The devices have high efficiency of >40%.
2.12.7 High-Speed VCSEL Devices
High-speed VCSEL devices are in development. Current devices work to 5 GHz
speed. Figure 2.50 shows the performance of a 4 μm aperture device perform-
ing at >5 GHz speed. A power level of >5 mW is achieved at these speeds.
2.12.8 High-Brightness Arrays of Single-Mode Devices
VCSELs are also a new technology for pumping of solid state lasers, including
fiber lasers. Because of their circular beam and excellent optical characteris-
tics, it is possible to make high-brightness pumps using an array of closely
spaced single-mode VCSEL devices. The arrays are temperature stable and
operate at high temperatures without chillers. They are lower cost as they
do not require expensive operations like cleaving of the wafers. These fiber
coupled arrays can be combined for higher output power using fiber combin-
ers and coupled with double core fiber to develop small, high-performance
fiber lasers working at elevated temperatures without chillers.
For high-brightness devices and arrays, PO makes self-lasing VCSELs or
extended or external cavity VCSELs and couples such arrays into fibers using
microlenses as shown in Figure 2.51.
2.12.9 Blue, Green, and UV VCSELs
PO developed very high quality blue lasers from VCSELs by frequency dou-
bling the VCSEL radiation with a nonlinear material. The blue laser output at
0
-5
-10
-15
-20
-25
0.E+ 00
4.E+ 09
2.E+ 09
6.E+ 09
8.E+ 09
Frequency (HZ)
FIGURE 2.50
A 4 u aperture single-mode device shows high-speed performance through >5 GHz. The device
power is >5 mW.
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