Yargo Bonetti

External cavity quantum cascade laser tunable from 7.6 to 11.4 μm

We present the development of a broad gain quantum cascade active region. By appropriate cascade design and using a symmetric active region arrangement, we engineer a flat gain and increase the total modal gain in the desired spectral range. Grating-coupled external cavity quantum cascade lasers using this symmetric active region are tunable from 7.6 to 11.4 μm with a peak optical output power of 1 W and an average output power of 15 mW at room-temperature. With a tuning of over 432 cm−1, this single source covers an emission range of over 39% around the center frequency.

Room-temperature, continuous-wave, single-mode quantum-cascade lasers at λ≃5.4μm

We demonstrate room-temperature, single-mode, continuous-wave operation of a λ≃5.4μm quantum-cascade laser up to the temperature of 30°C. Processing is done using standard lithography in a ridge waveguide mounted junction-up. The active region is based on a bound-to-continuum transition. The high performances were achieved with a low active region doping and a thick electroplated gold deposition, resulting in a characteristic temperature of T0=155K in continuous-wave with a threshold current density of jth=2.05kA∕cm2 at 300K.

Intersubband linewidths in quantum cascade laser designs

We present a model to a priori calculate the temperature and field dependent intersubband linewidth of the optical transition in quantum cascade laser designs. Besides intra- and intersubband lifetime broadening, it comprises interface roughness scattering based on the approach of Tsujino et al. [Appl. Phys. Lett. 86, 062113 (2005)]. We verified our model with experimental data of quantum cascade lasers having different linewidths. Excellent agreement with the experiment was found for the two-phonon resonance design. Linewidths are slightly overestimated in the bound-to-continuum design. Differential gain and threshold current density are in excellent agreement for the two-phonon resonance design. Although the slope efficiency is somewhat underestimated at low temperatures, there is still reasonable agreement with the experiment.

Distributed-Feedback Quantum-Cascade Lasers at 9

Single-mode lasers operating at lambda ap 9 mum in continuous wave up to 423 K (150degC) were achieved by the combination of strong distributed-feedback coupling, a narrow gain active region design, low intersubband, and free-carrier losses as well as a good thermal management. Tuning of 10 cm-1 or 0.9% of the center frequency was achieved by heating the device. The threshold current density varies from 1.1 kA/cm2 at 303 K to 2.4 kA/cm2 at 423 K. Other devices with low electrical power consumption of 1.6 and 3.8 W for an optical output power of 16 and 100 mW have been demonstrated at 263 K.

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We report spectral linewidth measurements of a 9.1‐µm distributed-feedback quantum cascade laser (QCL). The free-running QCL beam was mixed with a waveguide isotopic C18O2 laser onto a high-speed HgCdTe photomixer, and beat notes were recorded from a radio-frequency spectral analyzer. Beating was performed at two operating conditions, first near the QCL laser threshold (beating with the C18O2R10 line) and then at a high injection current (beating with the C18O2R8 line). Overall, beat note widths of 1.3–6.5 MHz were observed, which proves that a free-running QCL can have a short-term spectral width near 1 MHz.

m Operating in Continuous Wave Up to 423 K

The authors demonstrate an optically pumped ZnO distributed feedback laser operating at 383nm. For a large temperature range between 10 and 270K, the device lased in a single longitudinal mode. Mode selection was accomplished via a third order diffraction grating, which was dry etched into a 120nm thick Si3N4 layer deposited on the ZnO active region. They observed a spectral linewidth of 0.4nm, a pump threshold intensity of 0.12MW∕cm2, and a peak output power of 14mW. From wavelength versus temperature measurements, they deduced a temperature tuning coefficient of the ZnO refractive index of 9×10−5K−1.

Free-running 9.1-mu m distributed-feedback quantum cascade laser linewidth measurement by heterodyning with a (CO2)-O-18 laser

The quantum cascade laser is an unipolar semiconductor laser source emitting in the mid-infrared range between 3.5 and 25 μm. During the past ten years after their invention, this technology has reached the level of maturity required for commercialization, and QC lasers have thus become very attractive for a large number of applications, including gas sensing, pollution detection, atmospheric chemistry, detection of compounds, non-invasive medical diagnostics, free-space optical data transmission or even LIDAR. Most common requirements are single-mode operation on thermoelectric cooler, high power and/or continuous-wave. Nowadays several high-power single-mode QC lasers are available at Alpes Lasers in the range from 4.3 to 16.5 μm, with a side-mode suppression ratio larger than 30 dB. We present here a specific high-average power Fabry-Perot quantum cascade laser and a distributed-feedback quantum cascade laser operating near 8 μm.

Demonstration of an ultraviolet ZnO-based optically pumped third order distributed feedback laser

We report a realization of single-frequency quantum-cascade lasers in continuous-wave mode on thermo-electrical cooler at frequencies ~ 1830 cm-1 (~ 5.46 μm) and ~ 1900 cm-1 (~ 5.26 μm). The active region of the lasers is based on the broad gain bound-to-continuum concept. We report a 1.5 mm-long, 18 μm-wide quantum-cascade laser exhibiting single-mode emission over the entire investigated temperature and current ranges with a side-mode suppression ratio > 25 dB. Output powers up to 54 mW at -30°C and 1.2 mW at +27°C are demonstrated. A tuning range of 12.8 cm-1 (0.7%) can be obtained between 1823.1 cm-1 and 1835.9 cm-1. A different device, 1.5 mm-long, 12 μm-wide, is reported in the range 1892.8 cm-1 to 1905.5 cm-1, exhibiting output power of 59 mW at -30°C and 0.8 mW at +20°C. The objective of this development is to obtain a room-temperature continuous-wave quantum-cascade laser at 1900cm-1, important for NO (nitric oxide) measurements. We demonstrate also Fabry-Pérot continuous-wave operation of quantum-cascade lasers grown by metal organic vapour phase epitaxy up to -5°C without the need of buried heterostructure processing.

High-power and single-frequency quantum cascade lasers for gas sensing

We demonstrate multi-color DFB QCLs with separated electrical pumping for independent single-mode emission of several wavelengths from the same ridge. This will be implemented in our mid-infrared spectroscopy sensors for gases (CO2) and liquids (cocaine).

Room-temperature continuous-wave single-mode quantum cascade lasers

We report on the design and characterization of novel star-like multipass cells for high-precision trace gas analysis. Their optical path depends solely on the incident angle and they can be machined as a single piece.