Atomic Defects and Dramatic Changes in Optical Ferroelectrics

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Atomic Defects and Dramatic Changes in Optical
Ferroelectrics Gopalan, Penn State, DMR-0349632
A small amount of missing Li in
ferroelectric LiTaO3 changes the field needed
to switch domains by 210 times (!) as seen in the
hysteresis loops shown on the left. The
Li/(LiTa) is 0.5, 0.498, and 0.485 for
stoichiometric (SLT), near- stoichiometric
(NSLT), and congruent (CLT) compositions.
(Tian, Gopalan, APL, 85, 4445, 2004)
SLT composition is also attractive because of
10-100 times higher optical damage threshold
compared to NSLT and CLT respectively. Using
periodic domain patterning (see right), one
can create compact high power Red, Green, Blue
laser sources by frequency conversion of infrared
diode lasers. This will impact projector and
display technologies. Multiple companies are
pursuing this approach and presently consulting
with the PI.
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Live on an Optical Fiber !! Gopalan, Dierolf,
Penn State, DMR-0349632
The Science and Technology of Light Workshop
conducted by V. Gopalan and V. Dierolf (right),
October 30, 2004, Penn State, 11 and 12th grade
students from Philadelphia High Schools. The
students assembled an optical voice link and
sang gospel and RB to each other (above) on an
optical fiber! They also took apart a laser
pointer to see the tiny laser, listened to
lamps and remote controls, and AM/FM modulated
their voice to transmit by light!