Pawel Adamiec

High-Brightness Quantum Well Tapered Lasers

High-power quantum well lasers with high brightness in the spectral range between 650 nm and 1080 nm will be presented. Improved layer structures with a narrow vertical far-field divergence down to angles of 15deg (full-width at half-maximum) were developed. For these layer structures, optimized tapered lasers were processed to achieve laterally a nearly diffraction-limited beam quality with beam propagation factors smaller than 2. Depending on the emission wavelength, the tapered devices reach an output power up to 12 W and a brightness of 1 GWmiddotcm-2middotsr-1.

5-W DBR Tapered Lasers Emitting at 1060 nm With a Narrow Spectral Linewidth and a Nearly Diffraction-Limited Beam Quality

Distributed Bragg reflector tapered lasers emitting at a wavelength of about 1060 nm were realized. The expitaxial layer structure leads to a vertical far-field angle of 15deg (full-width at half-maximum). The devices with a total length of 4 mm consist of 2-mm-long ridge waveguide and tapered sections. The input currents to both sections can be independently controlled. The laser reached 5-W output power with a narrow spectral linewidth below 40 pm (95% power) and a nearly diffraction-limited beam quality.

Nearly Diffraction-Limited Tapered Lasers at 675 nm With 1-W Output Power and Conversion Efficiencies Above 30%

High brightness, highly efficient tapered lasers emitting around 675 nm have been developed. The devices have a 500- μm-long straight section and a 1500-μm -long tapered section with a flare angle of 3°. At a temperature of 25°C and a current of 1.5 A, the lasers emit an output power of nearly 1.2 W. The maximum conversion efficiency of 31% is reached at an output power of 1 W. The emitted beam is nearly diffraction-limited with a beam propagation ratio (second moments) of 2.2.

Tapered lasers emitting at 650 nm with 1 W output power with nearly diffraction-limited beam quality

High-brightness tapered lasers emitting around 650 nm were developed. Devices 2 mm long with a200-microm-long straight section, 1800-microm-long tapered section, and 4 degrees taper angle reached 1 W output power in CW operation with a nearly diffraction-limited beam quality.

Twin-Contact 645-nm Tapered Laser With 500-mW Output Power

High brightness tapered lasers emitting around 650 nm were developed. We realized 2-mm-long devices with 750-mum straight section, 1250-mum tapered section, and 4deg taper angle. The input currents into both sections were independently controlled. The laser reached 500-mW output power in continuous-wave operation in a nearly diffraction-limited beam quality. A modulation efficiency of 7.5 W/A was achieved.

Atmospheric CO

We propose an integrated path differential absorption (IPDA) lidar system based on a hybrid master oscillator power amplifier (MOPA) and single photon counting detection for column-averaged measurements of atmospheric CO2. The random modulated continuous wave (RM-CW) approach has been selected as the best suited to the average output power obtained from hybrid and monolithically integrated MOPAs. A compact RM-CW IPDA lidar instrument has been designed and fabricated. High-sensitivity and low-noise single photon counting has been used for the receiver. Colocated 2-km horizontal trial path experiments with a pulsed system and in situ measurements were performed for comparison. The RM-CW IPDA lidar instrument shows a relative accuracy of the order of about ±10% or ±40 parts per million CO2 concentration in absolute terms. The measurements qualitatively demonstrate the feasibility of CO2 IPDA measurements with an RM-CW system.

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We propose an integrated path differential absorption lidar system based on all-semiconductor laser sources and single photon counting detection for column-averaged measurements of atmospheric CO2. The Random Modulated Continuous Wave (RM-CW) approach has been selected as the best suited to semiconductor lasers. In a RM-CW lidar, a pseudo random sequence is sent to the atmosphere and the received signal reflected from the target is correlated with the original sequence in order to retrieve the path length. The transmitter design is based on two monolithic Master Oscillator Power Amplifiers (MOPAs), providing the on-line and off-line wavelengths close to the selected absorption line around 1.57 µm. Each MOPA consists of a frequency stabilized distributed feedback master oscillator, a bent modulator section, and a tapered amplifier. This design allows the emitters to deliver high power and high quality laser beams with good spectral properties. An output power above 400 mW with a SMSR higher than 45 dB and modulation capability have been demonstrated. On the side of the receiver, our theoretical and experimental results indicate that the major noise contribution comes from the ambient light and detector noise. For this reason narrow band optical filters are required in the envisioned space-borne applications. In this contribution, we present the latest progresses regarding the design, modeling and characterization of the transmitter, the receiver, the frequency stabilization unit and the complete system.

Sensing with a Random Modulation Continuous Wave Integrated Path Differential Absorption Lidar

The accurate determination of the atmospheric distribution of carbon dioxide (CO2) on planetary scale is a key requirement for setting up modeling tools able to make reliable predictions of Earth climate dynamics which are essential for the understanding of such important issues as climate change and global warming. Nowadays, the concentrations of CO2 are mainly measured in-situ at a number of surface stations that are unevenly distributed over the planet. Air-borne and space-borne missions have the potential to provide a denser and better distributed set of observations to complement those provided by the surface network.

Atmospheric CO2 remote sensing system based on high brightness semiconductor lasers and single photon counting detection

Semiconductor light sources like light emitting diodes (LEDs) or laser diodes (LDs) are the most important light sources for space applications. LEDs are used in the control panels or lightning systems in the spacecrafts and as growth lightning systems in a deep space.

RANDOM-MODULATION CW LIDAR SYSTEM FOR SPACE-BORNE CARBON DIOXIDE REMOTE SENSING BASED ON A HIGH-BRIGHTNESS SEMICONDUCTOR LASER

The results of the total ionizing dose (TID) and single event effect (SEE) tests on the contactless angular position sensor based on Hall effect are presented. The TID testing reveals that the devices are resistant to the gamma radiation exhibiting only a slight increase in the supply current, not more than 1 % of the initial values. In general, both the serial peripheral interface (SPI) output errors and analog output errors have recovered to their initial values after annealing at high temperatures. Only the biased sample with magnet showed a significant increase of the analog output error at higher radiation levels and did not return to its initial value, it remained about a 56 % higher. Nevertheless, the error is still within the limits for space application of the sensor. SEE tests were performed up to linear energy transfer (LET) levels of 67.7 MeV·cm2/mg and the sensors experienced neither single event latch-up (SEL) nor single event transient (SET). The upper limit of cross section for single event functional interrupt (SEFI) was found by Weibull fit as being 3.53 · 10-6 cm2 and the LET threshold was 15.1 MeV·cm2/mg. The SEFI rates were calculated by means of the CRÈME96 for geostationary orbit (GEO) and the orbit of the International Space Station (ISS). Calculations were performed for minimum solar and peak 5 minutes environment, and in the case of the ISS orbit also trapped particles and magnetic weather conditions were included.