Biomedical Engineering Reference
In-Depth Information
Active region
Distributed Bragg
reflectors (DBR)
PPLN
A/R-coating
Lens
GaAs substrate
Output coupler
980 nm HR
490 nm TR
FIGURE 2.52
This figure shows the schematic of blue laser generation. An external cavity approach is used
in which the PPLN is put inside the cavity. We have developed green laser using this approach
as well. A peak power of 6 W from a single VCSEL has been obtained with this approach.
(Courtesy of Princeton Optronics [PO] and Dr. Chuni Ghosh. With permission.)
VCSEL
Lens
OC
PPLN
FIGURE 2.53
This figure shows the experimental setup for frequency doubling of VCSEL devices. PPLN
material is used for frequency doubling. PO is working on frequency doubling of high-power
arrays. A peak power of 6 W from a single device has been obtained. (Courtesy of Princeton
Optronics [PO] and Dr. Chuni Ghosh. With permission.)
collimation architecture using microlenses. Using external lenses as shown
in Figure 2.56, one can achieve very narrow divergence with VCSEL arrays.
A divergence of 0.5 mrad has been achieved using an expander lens and a
focusing lens.
As discussed previously, VCSELs provide excellent illumination sources
for high-luminosity lighting requirements, such as high-speed videogra-
phy. PO developed an area illuminator module at 808 nm that can be used
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