Broad area type-I GaSb based diode lasers have recently exceeded 100 mW continuous wave room temperature powers
in 3.1-3.2 μm spectral region. Certain applications such as single frequency sources for spectroscopy and efficient
coupling to single mode fiber require single lateral mode laser operation. We characterize and compare two types of
lasers with similar structures and various ridge widths emitting at 3.1 and 3.2 μm. We obtain 35 and 25 mW of
continuous wave single lateral mode power from 8 and 13 μm wide ridge lasers emitting at 3.1 and 3.2 μm respectively.
This constitutes a threefold improvement compared to the previous result. Both devices had ridges etched to the depth
leaving approximately 300 nm of the top p-cladding in the areas outside the ridges. For 3.2 μm emitting lasers the
dielectric thickness was 220 nm while it was 510 nm for 3.1 μm emitting lasers. Gain spectra were measured by Hakki-
Paoli technique for various ridge widths. From gain spectra we extract differential gain and internal loss. We find that the
internal loss in thin dielectric, 3.2 μm emitting laser is about 14 cm-1 while it is 7 cm-1 in thick dielectric, 3.1 μm emitting
laser for the ridge widths of 13 and 8 μm exhibiting single lateral mode operation respectively. Internal losses measured
on broad area, 100 μm wide lasers processed from the same materials are similar and around 6-7 cm-1. We discuss
reasons for the internal loss increase with the aid of simulation of optical mode field and loss in our waveguide
structures.
The air quality of any manned spacecraft needs to be continuously monitored in order to safeguard the health of the
crew. Air quality monitoring grows in importance as mission duration increases. Due to the small size, low power draw,
and performance reliability, semiconductor laser-based instruments are viable candidates for this purpose. Achieving a
minimum instrument size requires lasers with emission wavelength coinciding with the absorption of the fundamental
absorption lines of the target gases, which are mostly in the 3.0-5.0 μm wavelength range. In this paper we report on our
progress developing high wall plug efficiency type-I quantum-well GaSb-based diode lasers operating at room
temperatures in the spectral region near 3.0-3.5 μm and quantum cascade (QC) lasers in the 4.0-5.0 μm range. These
lasers will enable the development of miniature, low-power laser spectrometers for environmental monitoring of the
spacecraft.
Recent progress and state of GaSb based type-I lasers emitting in spectral range from 2 to 3.5 μm is reviewed. For lasers
emitting near 2 μm an optimization of waveguide core width and asymmetry allowed reduction of far field divergence
angle down to 40-50 degrees which is important for improving coupling efficiency to optical fiber. As emission
wavelength increases laser characteristics degrade due to insufficient hole confinement, increased Auger recombination
and deteriorated transport through the waveguide layer. While Auger recombination is thought to be an ultimate limiting
factor to the performance of these narrow bandgap interband lasers we demonstrate that continuous improvements in
laser characteristics are still possible by increasing hole confinement and optimizing transport properties of the
waveguide layer. We achieved 190, 170 and 50 mW of maximum CW power at 3.1, 3.2 and 3.32 μm wavelengths
respectively. These are the highest CW powers reported to date in this spectral range and constitute 2.5-fold
improvement compared to previously reported devices.
The paper describes the heterostructures and device output parameters of Type-I quantum-well (QW) laser diodes with
InGaAsSb active regions designed for room-temperature operation near 2.3 μm and 3.1 μm. For both designs decrease of
the threshold current density and increase of the room-temperature output power have been achieved with increase of the
QW depth for holes. For the 2.3 μm laser diodes, confinement of holes in the QW embedded into the AlGaAsSb
waveguide was improved with increase of the hole energy level with compressive strain. Arrays of 1-mm-long 100-μmwide
laser diode emitters with a fill-factor of 30 % have been fabricated. A quasi-CW (30 μs, 300 Hz) output power of
16.7 W from a 4-mm-wide array has been obtained with conductive cooling. For the laser diodes designed for roomtemperature
operation above 3 μm, the hole confinement was improved by lowering the valence band energy in the
waveguide. Two approached were implemented: one with increase of the Al composition, and another with utilization of
quinternary InAlGaAsSb waveguide with increased As composition compared to the conventional AlGaAsSb
waveguide. With the quinternary waveguide approach, a room-temperature CW output power in excess of 130 mW and
a threshold current as low as 0.6 A have been obtained at λ = 3 μm from 2-mm-long 100-μm-wide emitters.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.