D. Hofstetter

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 Hz(2)/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.

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.

Continuous wave operation of quantum cascade lasers

We present buried heterostructure quantum cascade lasers with a four quantum well (QW) active region based on a double phonon resonance and with an improved waveguiding scheme and better heat dissipation for high temperature CW operation. The laser structure is grown by molecular beam epitaxy (MBE) using ternary InGaAs and InAlAs alloys lattice matched to an n-doped InP substrate.

Physical origin of frequency noise and linewidth in mid-IR DFB quantum cascade lasers

Frequency noise and linewidth properties of different mid-infrared DFB-QCLs using buried-heterostructures and ridge waveguides are compared. The physical origin of frequency noise and the impact of the different lasers parameters are discussed.

Frequency noise of free-running room temperature quantum cascade lasers

Narrow-linewidth lasers exhibiting a high spectral purity have important applications in various fields, such as high-resolution spectroscopy, coherent optical communications or time and frequency metrology, to name a few. With a proper feedback loop for linewidth reduction, such lasers can be used as ultra-stable reference for low phase noise microwave generation in frequency metrology. Since mid-infrared quantum cascade lasers (QCLs) are expected to have a narrow intrinsic linewidth (due to a linewidth-enhancement factor αH close to 0), we have recently investigated the frequency noise properties of commercial free-running singlemode QCLs emitting in the 4.6-µm wavelength range and operated in CW mode near room temperature.

Mid-infrared quantum cascade detectors for applications in spectroscopy and pyrometry

An overview of quantum cascade detector technology for the near- and mid-infrared wavelength range will be given. Thanks to photovoltaic instead of photoconductive operation, quantum cascade detectors offer great opportunities in terms of detection speed, room temperature operation, and detectivity. Besides some crucial issues dealing with fabrication and general characteristics, some possibilities for performance improvement will also be briefly presented. In a theory section, some basic considerations adopted from photoconductive detectors confirm the necessity of various trade-offs for the optimization of such devices. Nevertheless, we will show several possible measures to push the key performance figures of these detectors closer to their physical and technological limits.

Continuous wave operation of buried heterostructure quantum cascade lasers

We present buried heterostructure QC lasers with optimized design, an improved waveguiding scheme and better heat dissipation for high temperature CW operation. The lasers lower waveguide cladding and waveguide core consisted of ternary InAlAs and InGaAs layers grown lattice matched to an n-doped InP substrate by molecular beam epitaxy (MBE). The active region is a repetition of 35 stages, each stage comprising a four quantum well active zone designed for emission at 9.1 /spl mu/m.

Properties and origin of frequency noise in Mid-IR distributed feedback Quantum Cascade Lasers

This paper reports and compares the temperature dependence of the frequency noise measured in two different types of DFB-QCLs at 4.55 gm that use either a buried-heterostructure (BH) or a ridge structure.

Temperature dependence of the frequency noise and linewidth of a mid-IR DFB quantum cascade laser

We present the frequency noise and linewidth of a quantum cascade laser measured for the first time with the same device from cryogenic to room-temperature. A strong increase of the linewidth occurs at low temperature.

Quantum cascade laser: A promising candidate toward an ultra-stable laser in the mid-IR

The frequency noise properties of free-running single-mode mid-IR Quantum Cascade Lasers (QCLs) operated near room-temperature in CW mode and emitting at 4.6 µm are presented. The frequency noise level measured in this paper is globally a factor of 100 lower than recently reported for a similar QCL but operated at cryogenic temperature. The results are very promising for the future realization of a QCL-based ultra-stable laser in the mid-IR.