Tech Briefs Magazine - June 2022 - 32

Optics
requires complex lenses that can
handle the full optical spectrum and
be reshaped electrically within milliseconds.
Until now, a class of soft materials
known as liquid crystal spatial
light modulators has been the tool
of choice for high-resolution light
shaping but their implementation
has proven to have limits in terms of
performance, bulkiness, and cost.
A dynamically tunable lens capable
of achieving almost any complex
optical function was developed that
manipulates light without any mechanical
movement. In this Smartlens,
a current is passed through a
well-optimized microm eter-scale resistor
and the heating locally changes
the optical properties of the
transparent polymer plate holding
the resistor. In much the same way as a
mirage bends light passing through hot
air to create illusions of distant lakes,
this microscale hot region is able to deThe
location where the Smartlens is placed within the
optical instrument - in this case, a microscope.
(Image: Marc Montagut)
viate light. Within milliseconds, a simple
slab of polymer can be turned into
a lens and back. Small, micrometer-scale
Smart lenses heat up and cool
down quickly and with minimal power
consumption. They can even be fabricated
in arrays and several objects
located at very different distances
can be brought into focus within the
same image by activating the Smartlenses
located in front of each of
them, even if the scene is in color.
By modeling the diffusion of heat
and the propagation of light and using
algorithms inspired by the laws of
natural selection, a properly engineered
resistor can shape light with a
very high level of control and achieve
a wide variety of optical functions. If
the right resistor is imprinted on it, a
piece of polymer could be activated
or deactivated at will to generate a
given " freeform " and correct specific
defects in eyesight or the aberrations
of an optical instrument.
For more information, contact Dr. Silvia
Carrasco, Director, Knowledge & Technol ogy
Transfer at Silvia.Carrasco@icfo.eu; +34
935534090.
Compact Laser Source Detects Pollution
The simple mid-infrared laser source detects pollution in the air or molecules in a person's breath.
L'Ecole Polytechnique Fédérale de Lausanne, Switzerland
A
middle infrared light source can detect
greenhouse and other gases as
well as molecules in a person's breath.
The compact system, which resembles a
tiny suitcase, contains just two parts: a
standard laser and a photonic chip measuring
a few millimeters across.
The mid-infrared spectrum is useful
for scientists because, at this wavelength
range, light can detect particles that play
an important role in the environment
and in human health. Until now, however,
infrared laser systems have proven difficult
to transport because they involve
complex, damage- prone hardware.
The new technology consists of a commercially
available fiber laser combined
with a micrometer waveguide chip to
reliably generate light waves in the midinfrared
spectrum.
A spectrometer was added to demonstrate
the potential of the light source,
successfully detecting the presence and
concentration of acetylene, a colorless and
highly flammable gas.
The system uses a compact and robust
fiber laser that emits light in a specific
wavelength range. The beam is directed
through a waveguide, measuring one micrometer
(0.001 mm) across and half a
32
The system takes up considerably less space than the large ones typically used for such tasks, paving
the way for miniaturized mid-IR technologies.
millimeter long that can alter the frequency
of the light as it passes through.
The system produces light in the mid-infrared
spectrum, retaining 30 percent of
the original signal strength. The researchers
can even tune the wavelength of the
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light by adjusting the waveguide's geometry.
The technology eliminates the process
of precisely aligning all the parts in a
conventional laser system.
For more information, contact Hatice Altug
at hatice.altug@epfl.ch; +41-216-931-170.
Tech Briefs, June 2022
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Tech Briefs Magazine - June 2022

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