Another possible application of the TPPV effect is photovoltaic power
converters and optically powered sensors for ber-optic networks.
Illustration by www.takayukisato.com
of the two e ec t s will result in higher
e ciency at shorter wavelengths.
Indeed, resear chers have observed
good agreement b etween analytical
and experimental r esults. At lower
pump intensities, q u antum e ciency
approaches the theoretical limit of 50
percent. e value of the e ciency the e ciency
at maximum power g eneration
bias is about 40 percent, and
is nearly independent o f
coupled optical intensit y
from 5 to 150 MW/cm2 .
Physically, this rather
constant behavior occurs because the recombinatio n current current
dominates the di usion cu rrent at low
biases and grows at approximately the
same rate as the photogenerated current.
reported that TPA and TPA-generated FCA can limit the output
power of a high-power III-V-based
semiconductor optical amplifier.
Adding the TPPV e ect to these
devices may allow us to harvest
the optical loss to electrical power
and simultaneously to mitigate
the TPA and the associated
FCA optical loss through carrier
sweep-out, as is the case in
silicon. ese advances will lead the
way toward green integrated photonics that may have a profound e ect on the
telecom industry, the economy—and the
health of the planet.
Energy harvesting through the two-photon
photovoltaic effect can be utilized to supply
the electrical power to electronics circuitry
in optically interconnected VLSI chips.
e TPPV o ers a viable solution
for achieving energy-e cient silicon
photonics devices. e e ect reduces
the optical loss by TPA and FCA, and
serendipitously converts the optical
energy lost to TPA to useful electrical
power. e harvested power can thus
be recycled to supply electrical power
to electronics on the same platform. It
is even possible to create a self-powered
Beyond optical interconnects,
another possible application of the
TPPV e ect is photovoltaic power converters (PPCs) and optically powered
sensors for fiber-optic networks. PPCs
are used for remote power delivery and
are optimized for a wavelength range
from 1,300 to 1,550 nm. PPCs that can
provide a few m W to 100 m W power are
e TPPV e ect is ideal for delivering power to the sensors used for
monitoring and managing fiber-optic
networks. Such sensors typically
measure the optical power at a given
point along the fiber link. A silicon
p-n junction waveguide operating as a
two-photon photodetector has already
been proposed as an in-line power monitor. Here, a small fraction of the signal
is absorbed by TPA while most of the
light is passed through. In this scenario,
electrical power must be delivered to the
monitoring point to provide the power
needed by the photodetector and to
drive the supporting electronic circuitry.
With the TPPV e ect, one may be
able to construct a self-powered remote
sensor that measures the optical power
passing through the waveguide while at
the same time providing power for the
e nonlinear photovoltaic e ect is
not limited to silicon; it is also applicable to compound semiconductors.
Indeed, reported values of at 1. 3 m
in InP and GaAs are 70 and 42. 5 cm/
GW, respectively, versus 3. 3 cm/GW in
silicon, which is in turn more than six
times higher than the aforementioned
value of at 1. 55 m in silicon. e
FCA loss of III-V materials is typically
the same as in silicon.
Hence, the TPPV e ect is expected
to have higher e ciency in compound
semiconductors. is is important
because researchers have recently
Bahram Jalali ( email@example.com) and Kevin Tsia
are with the University of California, Los Angeles
(UCLA), U.S.A. Sasan Fathpour was previously
affiliated with UCLA, but is now with CREOL, the
College of Optics and Photonics at the
Member University of Central Florida, Fla., U.S.A.
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