Résultat de la recherche
Frequency noise of free-running 4.6 μm distributed feedback quantum cascade lasers near room temperature
The frequency noise properties of commercial distributed feedback quantum cascade lasers emitting in the 4.6 μm range and operated in cw mode near room temperature (277 K) are presented. The measured frequency noise power spectral density reveals a flicker noise dropping down to the very low level of <100 Hz2/Hz at 10 MHz Fourier frequency and is globally a factor of 100 lower than data recently reported for a similar laser operated at cryogenic temperature. This makes our laser a good candidate for the realization of a mid-IR ultranarrow linewidth reference.
16.5 µm quantum cascade detector using miniband transport
The authors report on an InP based photovoltaic quantum cascade detector operating at 16.5 µm and using miniband-based vertical transport. This concept allowed the construction of a longitudinal optical phonon extraction stair with two rungs without touching on a high device resistance. At 10 K, they observed a responsivity of 1.72 mA/W and a Johnson noise limited detectivity of 2.2×109 Jones. Altogether, this design resulted in detection at temperatures of up to 90 K with a lower bandwidth limit of 200 MHz imposed by the measurement setup.
23 GHz operation of a room temperature photovoltaic quantum cascade detector at 5.35 µm
We present a room temperature operated 5.35 µm quantum cascade detector which was tested at high frequencies using an optical heterodyne experiment. Two slightly detuned continuous wave distributed feedback single mode quantum cascade lasers were used to generate a beating signal. The maximum frequency at which the resulting microwave signal could be detected was 23 GHz. The cutoff behavior of our device was modeled with a simple RLC circuit and showed excellent agreement with the experimental data.
Spectroscopic study of the ν1 band of SO2 using a continuous-wave DFB QCL at 9.1 µm
We report results of spectroscopic measurements with a continuous-wave distributed-feedback quantum-cascade laser (DFB QCL). Line intensities and self-broadening coefficients were measured in the ν1 band of SO2 between 1088 and 1090 cm-1. The self-broadening coefficients in this paper confirm the typical decrease of νself with increasing rotational quantum number K’’a. The line intensities determined here are smaller than those in the HITRAN 2000 database. Several lines found in this study were not present in the database.
Quantum Cascade Detectors
This paper gives an overview on the design, fabrication, and characterization of quantum cascade detectors. They are tailorable infrared photodetectors based on intersubband transitions in semiconductor quantum wells that do not require an external bias voltage due to their asymmetric conduction band profile. They thus profit from favorable noise behavior, reduced thermal load, and simpler readout circuits. This was demonstrated at wavelengths from the near infrared at 2 μm to THz radiation at 87 μm using different semiconductor material systems.
A THz quantum cascade detector in a strong perpendicular magnetic field
A 3.6 THz quantum cascade detector is studied under the influence of a strong magnetic field applied perpendicularly to the plane of the layers. Modulation of lifetimes based on elastic intersubband scattering processes is observed, leading to an increase of the responsivity for particular values of the applied magnetic field.
Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies
Lasing properties of room temperature, continuous wave operated distributed feedback (DFB) quantum cascade lasers are reported. A bound-to-continuum active region was used to generate a broad gain spectrum. As a result, first-order DFB lasers employing different periods allowed us to achieve single mode continuous wave emission at several wavelengths ranging from 7.7 to 8.3 µm at a temperature of +30 °C. The frequency span corresponds to 8% of the center frequency.
Short wavelength (4 µm) quantum cascade detector based on strain compensated InGaAs/InAlAs
We report on a quantum cascade detector based on nearly strain compensated InGaAs/InAlAs pseudomorphically grown on InP substrate and detecting light at short wavelengths around 4 µm. The background limited infrared performance (BLIP) condition is met at a temperature of 108 K with a high detectivity of D*BLIP =1.2×1011 Jones.
Microfluidic tuning of distributed feedback quantum cascade lasers
In this Letter, we report the tuning of the emission wavelength of a single mode distributed feedback quantum cascade laser by modifying the mode effective refractive index using fluids. A fabrication procedure to encapsulate the devices in polymers for microfluidic delivery is also presented. The integration of microfluidics with semiconductor laser (optofluidics) is promising for new compact and portable lab-on-a-chip applications.
InP-based quantum cascade detectors in the mid-infrared
We present two InP-based quantum cascade detectors (QCDs) in the mid-infrared wavelength range. Their narrow band detection spectra are centered at 5.3 and 9 µm. A vertical intersubband transition followed by a carefully designed extraction cascade, which is adapted to the LO-phonon energy, leads to 10 K responsivities R of 3.2 and 9.0 mA/W and background limited detectivities D*BLIP of 2×108 and 3×109 Jones, for the 5.3 and the 9 µm devices, respectively. Detection has been observed up to device temperatures of 300 K (RT), albeit reasonable performance is restricted to temperatures below 150 K (5.3 µm) and 70 K (9 µm). Designed for zero bias operation, QCDs do not produce any dark current and therefore do not suffer from dark current noise and capacitance saturation at long integration times, making them ideal devices for large focal plane arrays.
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