GaSb-based Diode Lasers Research Articles

Room temperature operated 3.1μm type-I GaSb-based diode lasers with 80mW continuous-wave output power

High-power diode lasers with heavily strained In(Al)GaAsSb type-I quantum-well active regions emitting at 3.1μm at room temperature are reported. The devices produce continuous-wave output powers above 200mW at 250K and 80mW at 285K.

High power 2.4μm heavily strained type-I quantum well GaSb-based diode lasers with more than 1W of continuous wave output power and a maximum power-conversion efficiency of 17.5%

The authors demonstrate a double quantum well GaSb-based diode laser operating at 2.4μm with a room-temperature cw output power of 1050mW and a maximum power-conversion efficiency of 17.5%. Laser differential gain with respect to current increases by a factor of 2 and laser threshold current is nearly halved when the compressive strain in the quantum wells is increased from 1.2% to 1.6%. This improvement is due to substantially improved hole confinement in the heavily compressively strained active region.

2.3 [micro sign]m type-I quantum well GaInAsSb/AlGaAsSb/GaSb laser diodes with quasi-CW output power of 1.4 W

Improvement of the output parameters of 2.3 mum GaSb-based laser diodes was observed with increase of the quantum-well compressive strain. A continuous-wave (CW) power of 1.15 W and quasi-CW power of 1.4 W were obtained at room temperature from 2 mm-long single emitters with a 100 mum-aperture.

Widely Tunable GaSb-Based External Cavity Diode Laser Emitting Around 2.3$mu$m

We report on a widely tunable external cavity GaSb-based diode laser (ECL) in Littrow-configuration. The low (44deg full-width at half-maximum) fast axis beam divergence of the quantum-well diode laser employed allowed an efficient coupling to the external cavity, which resulted in a wide tuning range of 177 nm around the central emission wavelength of 2.30 mum. The maximum output power of the fiber coupled ECL system varied only moderately between 16.5 mW at 2.23 mum and 9 mW at the long-wavelength limit at 2.39 mum

Measuring the 13C/12C isotope ratio in atmospheric CO2 by means of laser absorption spectrometry: a new perspective based on a 2.05-μm diode laser

The potential use of high sensitivity laser absorption spectroscopy for measuring the 13C/12C isotope ratio in atmospheric CO2 has been demonstrated, using a GaSb-based diode laser at 2.05 μm. In this spectral region, the overlapping between relatively strong 12CO2 and 13CO2 absorption features gives rise to several line pairs which are well suitable for a spectroscopic determination of the isotope ratio. Preliminary results have demonstrated that a short-term precision better than 1‰ can be easily obtained, for a CO2 concentration of 1000 ppm. We extensively discuss the influence of a possible non-linearity in the detectors' response on the δ-value and suggest an instrumental development that would allow to eliminate this effect.

High-power 1.9-μm diode laser arrays with reduced far-field angle

High-power 1.91-mum (AlGaIn)(AsSb) quantum-well diode laser single emitters and linear arrays with improved waveguide design were fabricated and characterized. The use of a rather narrow waveguide core results in a remarkable low fast axis beam divergence of 44deg full-width at half-maximum. For single emitters, a continuous-wave (CW) output power of nearly 2 W has been observed. We have achieved 16.9 W in CW mode at a heat sink temperature of 20degC. The efficiencies of more than 25% are among the highest values reported so far for GaSb-based diode lasers, and allow the use of passively cooled and, thus, less expensive heat sink technologies

Looking into the volcano with a Mid-IR DFB diode laser and Cavity Enhanced Absorption Spectroscopy

We report on the first application of extended-wavelength DFB diode lasers to Cavity-Enhanced Absorption Spectroscopy in-situ trace measurements on geothermal gases. The emission from the most active fumarole at the Solfatara volcano near Naples (Italy) was probed for the presence of CO and CH(4). After passing through a gas dryer and cooler, the volcanic gas flow (98% CO(2)) was analysed in real time for the concentration of these species, whose relatively strong absorption lines could be monitored simultaneously by a single Distributed Feed-Back (DFB) GaSb-based diode laser emitting around 2.33 mum (4300 cm(-1)) at room temperature. The concentrations were found to be about 3 ppm and 75 ppm, respectively, while actual detection limits for these molecules are around 1 ppb. We discuss the possibility of detecting other species of interest for volcanic emission monitoring.

Room-temperature operation of 3.26μm GaSb-based type-I lasers with quinternary AlGaInAsSb barriers

Quinternary AlGaInAsSb is introduced as a new barrier material for GaSb-based type-I laser diodes. For wavelengths beyond 3μm, this material improves the valence-band offset between GaInAsSb quantum wells and barriers as compared to standard GaInAsSb∕AlGaAsSb structures. The laser structures, which comprise three compressively strained GaInAsSb quantum wells and AlGaInAsSb barriers and waveguides, show good structural and optical quality. 3.26μm emission has been achieved with ridge waveguide lasers working in pulsed operation up to 50°C. With this emission wavelength, a strong absorption line of CH4 is accessible for gas absorption measurements.

Long-wavelength GaInAsSb/AlGaAsSb DFB lasers emitting near 2.6 μm

We have successfully fabricated and characterized room temperature continuous wave (cw) GaInAsSb/AlGaAsSb distributed feedback lasers emitting in the wavelength region between 2.499 and 2.573 μm. To the best of our knowledge, this is the longest emission wavelength realized with a GaSb-based DFB laser diode. The laser structure used for DFB processing was grown by solid source molecular beam epitaxy. A DFB concept requiring no subsequent overgrowth step was used by defining first-order Cr-Bragg gratings laterally patterned to a ridge waveguide. Threshold currents smaller than 60 mA and room temperature cw output powers up to 6.5 mW were obtained. The laser diodes show single mode emission with side mode suppression ratios (SMSR) of up to 32 dB.

MID-INFRARED GaSb-BASED LASERS WITH TYPE-I HETEROINTERFACES

The design of room-temperature, InGaAsSb/AlGaAsSb diode lasers has evolved from the first double-heterojunction lasers described in 1980 that operated in the pulsed-current mode to present-day continuous–wave (CW), high-power, quantum–well diode lasers. We discuss in detail recent results from type-I-heterostructure, GaSb-based CW room-temperature diode lasers. The devices operate within the wavelength range of 1.8 to 2.7 μm, providing output powers up to several Watts. We analyze the factors limiting device performance.

Sb-Based Mid-Infrared Diode Lasers

AbstractIn this paper we review recent progress achieved in our development of type-I GaInAsSb/AlGaAsSb quantum-well (QW) lasers with emission wavelength in the 1.74–2.34 μm range. Triple-QW (3-QW) and single-QW (SQW) diode lasers having broadened waveguide design emitting around 2.26 μm have been studied in particular. Comparing the two designs we have find that the threshold current density at infinite cavity length as well as the transparency current density scale with the number of QWs. Maximum cw operating temperature exceeding 50°C and 90°C has been obtained for ridge waveguide lasers emitting above and below 2 μm, respectively. Ridge waveguide diode lasers emitting at 1.94 μm exhibited internal quantum efficiencies in excess of 77%, internal losses of 6 cm−1, and threshold current density at infinite cavity length as low as 121 A/cm2 reflecting the superior quality of our diode lasers, all values recorded at 280 K. A high characteristic temperature TOof 179 K for the threshold current along with a value of T1 = 433 K for the characteristic temperature of the external efficiency have been attained for the 240–280 K temperature interval. Room temperature cw output powers exceeding 1.7 W have been demonstrated for broad area single element devices with highreflection/ antireflection coated mirror facets, mounted epi-side down. The latter result is a proof for the high power capabilities of these GaSb-based mid-ir diode lasers.

In situ combustion measurements of CO, CO 2, H 2O and temperature using diode laser absorption sensors

A diode-laser sensor system based on absorption spectroscopy techniques has been developed to measure CO, CO 2 , and H 2 O concentrations and gas temperature non-intrusively in the combustion and exhaust regions above a C 2 H 4 -air burner operating at atmospheric pressure. In situ measurements of CO concentration in the combustion region (1.5 cm above the burner) and in the exhaust (79 cm above the burner) were determined from absorption lineshapes of the R(30) and R(15) transitions (2ν band) near 2.3 μ m, respectively, using new research-grade GaSb-based diode lasers. A minimum detectivity of less than 10 ppm was demonstrated in the exhaust region. In situ measurements of H 2 O concentration and gas temperature were determined from absorption lineshapes near 1.343 μ m (ν 1 +ν 3 band), 1.392 μ m (2ν 1 , ν 1 +ν 3 bands), and 1.799 μ m (2ν 2 +ν 3 ←ν 2 band) using distributed feedback (DFB) diode lasers. In situ measurements of CO 2 were recorded using a DFB laser near 1.997 μ m (R [50]) transition, ν 1 +2ν 2 +ν 3 band). Gas temperature and H 2 O and CO 2 concentrations were monitored simultaneously along a single path in the combustion region (1.5 cm above the burner surface) using a wavelength-multiplexing arrangement. The CO, CO 2 , and H 2 O concentration measurements in the combustion region agreed with calculated equilibrium populations to within the experimental uncertainty (10% for CO 2 and H 2 O, 5% for CO), and the measured temperatures were in agreement with radiation-corrected type-S thermocouple values to within 4%. These results demonstrate the utility of diode laser sensors for fast in situ measurements of multiple important combustion parameters for emissions-monitoring and closed-loop control applications.