Quantum dots enable infrared lasing at room temperature in silicon
photonics

Date:
September 29, 2021
Source:
ICFO-The Institute of Photonic Sciences
Summary:
Researchers report on having achieved a solution-processed infrared
laser at room temperature compatible with CMOS technology and
tunable to emit in the telecommunications window.



FULL STORY ========================================================================== Lasers, devices that emit light in one direction, with photons traveling
at one specific frequency and all with the same phase (coherent), govern
the way we communicate today. Although lasers are known to most people
as little torches emitting high purity color beams, the workhorse of
lasers is actually in the infrared part of spectrum, where our eyes cannot
see. The reason for this is that optical fibers are highly transparent to
the infrared (1.3-1.6 um), allowing efficient optical transmission with
very high data rates. Moreover, infrared lasers have minimum overlap with ambient light and are considered eye- safe, allowing their use in LIDAR
(light detection and ranging) applications for 3D imaging, automotive
and free-space communications. To date, infrared lasers are mainly made
with Erbium-doped fibers or III-V epitaxial semiconductors, imposing
certain limitations in their manufacturing and their easy integration
with electronics.


==========================================================================
An important feature to take into account while working with lasers
is the optical gain. The optical gain describes how well the light
can be amplified in the system. If one could find a new optical gain
material platform that can be produced with low cost in high volumes
and can be integrated on a variety of substrates and form factors, this
would definitely unleash a whole new realm of applications. Imagine such material that can be conformally coated along optical fibers or directly deposited atop CMOS silicon. Even better, imagine it to possess facile
bandgap tunability so that the emission wavelength of the laser can be
readily tuned across the infrared. Such solution could lead to inter-
or intra-chip optical communications offering lower power consumption,
low cost and higher data rates or enable multi-spectral 3D imaging capabilities.

Colloidal quantum dot (CQD) technology is based on a solution processed optoelectronic material platform that has demonstrated already its
potential for infrared optoelectronics with high performance CMOS
compatible photodetectors and light emitting diodes (LEDs). The
realization of an infrared CQD laser though had remained elusive.

Now, in a recent paper published in Nature Photonics, ICFO researchers
Guy Whitworth, Mariona Dalmases, and Nima Taghipour, led by ICREA
Prof. at ICFO Gerasimos Konstantatos have reported the achievement of
a colloidal quantum- dot-based infrared laser source operating at room temperature, compatible with CMOS technology and tunable to emit in the telecommunications window, an important milestone needed for classical
or quantum communications.

Previous to this finding, the team had already been working on an
experiment where they were able to demonstrate stimulated emission and
optical gain of quantum dots on thin films, but what they were lacking
was actually inserting this setup into a cavity to achieve lasing.

Infrared QD Lasing at room temperature To find the ideal cavity for the experiment, the team of researchers took a distributed feedback cavity
(DFB), spincoating atop a thin layer of PbS CQDs as the optical gain
medium. By concomitantly tuning the size of the dots and the geometrical characteristics of the DFB to optimize the cavity resonance with the
gain spectrum of the quantum dots they managed to demonstrate lasing
emission across the eye-safe optical communication infrared spectrum
and at room temperature, thus, possibly finding the last piece of the
jigsaw puzzle for silicon photonics.

In addition, the researchers went a little further and engineered the
surface of the dots in order to suppress electronic trap states in
order to favor stimulated emission. They made use of a robust doping
of the quantum dots to demonstrate lasing emission at lower pumping intensities, an achievement that opens a new path towards more practical implementations.

As Prof. Gerasimos Konstantatos comments, "the results of this study are considered a major breakthrough in the field of CQD optoelectronics. This discovery may facilitate fully integrated silicon photonics, paving
the way towards low-cost solution processed and CMOS integrated lasing
sources for on- chip comm or LIDAR applications. Before, further advances
are needed to optimize the material in order to demonstrate lasing under continuous wave or nanosecond excitation, which makes our next milestone." ========================================================================== Story Source: Materials provided by
ICFO-The_Institute_of_Photonic_Sciences. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. G. L. Whitworth, M. Dalmases, N. Taghipour,
G. Konstantatos. Solution-
processed PbS quantum dot infrared laser with room-temperature
tunable emission in the optical telecommunications window. Nature
Photonics, 2021; 15 (10): 738 DOI: 10.1038/s41566-021-00878-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210929112828.htm

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