Researchers at the Naval Research
Laboratory (NRL), Sarnoff Corporation, and Sensors Unlimited
have demonstrated the first room-temperature operation of an
interband III-V laser diode emitting at a wavelength beyond three
microns. The research team reports that this new development
brings the GaSb-based technology closer to achieving truly practical
and portable Mid-IR laser systems that are needed for many military
and commercial applications. This work was sponsored by the Office
of Naval Research (ONR).
The research team was led by
Dr. Jerry Meyer of NRL's Optical Physics Branch in the Optical
Sciences Division, Dr. Ramon Martinelli of the Sarnoff Corporation,
and Dr. Alan Sugg of Sensors Unlimited, Inc.
Dr. Meyer reports, "A truly
practical Mid-IR laser will need to operate continuously (cw)
at room temperature if it is to find widespread commercial acceptance.
To date at room temperature, our lasers only emit short pulses
which are useful for many research applications. This achievement
is an important milestone that the optoelectronics community
has been working towards for over a decade.
Earlier researchers using non-cascaded
III-V semiconductor lasers achieved pulsed operation only up
to -18° C. During the last three years, III-V quantum cascade
lasers using intersubband transitions and lead-salt lasers with
IV-VI compounds achieved pulsed room-temperature operation in
this wavelength range. While no Mid-IR semiconductor has lased
continuously at non-cryogenic temperatures to date, the new W
quantum well laser reached -78° C, which is higher than any
earlier III-V laser beyond 3 microns."
The research team reports that
the structure enabling them to reach room temperature operation
was composed of an NRL-developed antimonide type-II "W"
quantum well active region combined with a Sarnoff developed
broadened-waveguide confinement region. The lasing wavelength
at 27° C was 3.3 microns, the spectral width was 12 nanometers,
and the peak output power was greater than 2 miliwatts.
Trace amounts (parts per billion
to parts per million) of chemicals may be detected with 100 to100,000
times greater sensitivity in the Mid-IR than at shorter wavelengths.
Once the technology is commercially available, inexpensive
room-temperature
laser diodes will find widespread use in such applications as
pollution monitoring, leak detection, medical diagnostics, factory
process control, base-cleanup, and the detection of chemical
weapons sites.
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