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A strain-balanced, InP-based quantum cascade laser structure designed for light emission at 4.6 μm was grown by metal-organic chemical vapor deposition. A maximum total optical power of 1.6 W was obtained in continuous-wave mode at 300 K for uncoated devices processed in buried heterostructure geometry with stripe dimensions of 5 mm by 9.5 μm. Corresponding maximum wall plug efficiency and threshold current density were measured to be 8.8% and 1.05 kA/cm2, respectively. Fully hermetically packaged laser of identical dimensions produced in excess of 1.5 W under the same conditions. [ABSTRACT FROM AUTHOR]

High-power continuous-wave operation of long wavelength quantum cascade lasers grown by metal organic vapour phase epitaxy is reported. The lasers have been processed as buried heterostructures with thick gold-plated contacts. The devices emit at a wavelength of 9.5 µm with output powers of several hundreds of milliwatts at room temperature. [ABSTRACT FROM AUTHOR]

We present second-harmonic surface emission from distributed feedback GaAs/AlGaAs quantum-cascade lasers with integrated intersubband nonlinearities. The devices show single mode fundamental and second-harmonic emission at wavelengths of 10.7 and 5.35 μm, respectively. Only 5.35 μm light is emitted from the surface, as the fundamental light is not coupling to radiating modes for the grating of our choice. The second-harmonic peak optical power via the surface at 78 K is 150 μW for a fundamental peak power of 1.1 W. [ABSTRACT FROM AUTHOR]

Emission of coherent light at 5.1 µm wavelength from GaAs-based quantum cascade lasers is reported. This was achieved by integrating nonlinear cascades with large second-order susceptibility in the active regions of the laser. [ABSTRACT FROM AUTHOR]

A correction to the article "Room-temperature continuous-wave operation of long wavelength (λ=9.5 μm) MOVPE-grown quantum cascade lasers" that was published in the previous issue is presented.

Quantum cascade lasers (QCLs) are ubiquitous mid-infrared sources owing to their flexible designs and compact footprints. Manufacturing multiwavelength QCL chips with high power levels and good beam quality is highly desirable for many applications. In this study, we demonstrate an λ ∼ 4.9 µm monolithic, wavelength beam-combined (WBC) infrared laser source by integrating on a single chip array of five QCL gain sections with an arrayed waveguide grating (AWG). Optical feedback from the cleaved facets enables lasing, whereas the integrated AWG locks the emission spectrum of each gain section to its corresponding input channel wavelength and spatially combines their signals into a single-output waveguide. Our chip features high peak power from the common aperture exceeding 0.6 W for each input channel, with a side-mode suppression ratio (SMSR) of over 27 dB when operated in pulsed mode. Our active/passive integration approach allows for a seamless transition from the QCL ridges to the AWG without requiring regrowth or evanescent coupling schemes, leading to a robust design. These results pave the way for the development of highly compact mid-IR sources suitable for applications such as hyperspectral imaging.

Photonic integrated circuits and mid-infrared quantum cascade lasers have attracted significant attention over the years because of the numerous applications enabled by these compact semiconductor chips. In this paper, we demonstrate low loss passive waveguides and highly efficient arrayed waveguide gratings that can be used, for example, to beam combine infrared (IR) laser arrays. The waveguide structure used consists of an In 0.53 Ga 0.47 As core and InP cladding layers. This material system was chosen because of its compatibility with future monolithic integration with quantum cascade lasers. Different photonic circuits were fabricated using standard semiconductor processes, and experiments conducted with these chips demonstrated low-loss waveguides with an estimated propagation loss of ∼ 1.2 dB/cm as well as micro-ring resonators with an intrinsic Q-factor of 174,000. Arrayed waveguide gratings operating in the 5.15-5.34 µm range feature low insertion loss and non-uniformity of ∼ 0.9 dB and ∼ 0.6 dB, respectively. The demonstration of the present photonic circuits paves the path toward monolithic fabrication of compact infrared light sources with advanced functionalities beneficial to many chemical sensing and high-power applications.

We report continuous-wave operation of single-mode quantum cascade (QC) lasers emitting near 7.4 µm with threshold power consumption below 1 W at temperatures up to 40 °C. The lasers were fabricated with narrow, plasma-etched waveguides and distributed-feedback sidewall gratings clad with sputtered aluminum nitride. In contrast to conventional buried-heterostructure (BH) devices with epitaxial sidewall cladding and in-plane gratings, the devices described here were fabricated without any epitaxial regrowth processes, yet they exhibit power consumption comparable to the lowest-dissipation BH QC lasers reported to date. These low-dissipation devices are designed primarily as light sources for infrared spectroscopy instruments with limited volume, mass, and power budgets.

We demonstrate a three-section, electrically pulsed quantum cascade laser which consists of a Fabry-Pérot section placed between two sampled grating distributed Bragg reflectors. The device is current-tuned between ten single modes spanning a range of 0.46 μm (63 cm(-1)), from 8.32 to 8.78 μm. The peak optical output power exceeds 280 mW for nine of the modes.

We report quantum cascade laser (QCL) master-oscillator power-amplifiers (MOPAs) at 300 K reaching output power of 1.5 W for tapered devices and 0.9 W for untapered devices. The devices display single-longitudinal-mode emission at λ = 7.26 µm and single-transverse-mode emission at TM(00). The maximum amplification factor is 12 dB for the tapered devices., (© 2011 Optical Society of America)

Optical microcavities can be designed to take advantage of total internal reflection, which results in resonators supporting whispering-gallery modes (WGMs) with a high-quality factor (Q factor). One of the crucial problems of these devices for practical applications such as designing microcavity lasers, however, is that their emission is nondirectional due to their radial symmetry, in addition to their inefficient power output coupling. Here we report the design of elliptical resonators with a wavelength-size notch at the boundary, which support in-plane highly unidirectional laser emission from WGMs. The notch acts as a small scatterer such that the Q factor of the WGMs is still very high. Using midinfrared (λ ∼ 10 μm) injection quantum cascade lasers as a model system, an in-plane beam divergence as small as 6 deg with a peak optical power of ∼5 mW at room temperature has been demonstrated. The beam divergence is insensitive to the pumping current and to the notch geometry, demonstrating the robustness of this resonator design. The latter is scalable to the visible and the near infrared, thus opening the door to very low-threshold, highly unidirectional microcavity diode lasers.

We investigated dual wavelength mid-infrared quantum cascade lasers based on heterogeneous cascades. We found that due to gain competition laser action tends to start in higher order lateral modes. The mid-infrared mode with the lower threshold current reduces population inversion for the second laser with the higher threshold current due to stimulated emission. We developed a rate equation model to quantitatively describe mode interactions due to mutual gain depletion., ((c) 2010 Optical Society of America.)

We present a method to study current paths through quantum cascade lasers (QCLs). The temperature dependence of the current is measured at a fixed voltage. At low temperatures we find activation energies that correspond to the energy difference between the injector ground state and the upper laser level. At higher temperatures additional paths with larger activation energies are found. Application of this method to high performance QCLs based on strained InGaAs/InAlAs quantum wells and barriers with different band-offsets allows us to identify individual parasitic current paths through the devices. The results give insight into the transport properties of quantum cascade lasers thus providing a useful tool for device optimization.