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We report the first combination of MIR ICLEDs combined with a substrate-integrated hollow waveguide for gas detection. This combination is a pioneering step toward a new generation of miniaturized and low-cost MIR optical sensing devices.

Space-to-ground high-speed transmission is of utmost importance for the development of a worldwide broadband network. Mid-infrared wavelengths offer numerous advantages for building such a system, spanning from low atmospheric attenuation to eye-safe operation and resistance to inclement weather conditions. We demonstrate a full interband cascade system for high-speed transmission around a wavelength of 4.18 µm. The low-power consumption of both the laser and the detector in combination with a large modulation bandwidth and sufficient output power makes this technology ideal for a free-space optical communication application. Our proof-of-concept experiment employs a radio-frequency optimized Fabry–Perot interband cascade laser and an interband cascade infrared photodetector based on a type-II InAs/GaSb superlattice. The bandwidth of the system is evaluated to be around 1.5 GHz. It allows us to achieve data rates of 12 Gbit/s with an on–off keying scheme and 14 Gbit/s with a 4-level pulse amplitude modulation scheme. The quality of the transmission is enhanced by conventional pre- and post-processing in order to be compatible with standard error-code correction.

Fabry-Pérot interband cascade laser with varied thickness of the separate confinement layers and reduced cladding layer thickness are presented. An epi-side-down mounted device showed a cw-output power of 505mW emitting at λ≈3.3 μm at 10°C.

In this work, monolithic mode-locked GaSb-based lasers at 1.7 µm emission wavelength with heterodyne measurement of the frequency comb are presented. Mode-locking operation was confirmed by measuring the optical beatnote at the round-trip frequency of 9.56 GHz and analysing the frequency comb. Mode-locking operation occurred from 0.1 to 3.3 V reverse bias voltages at the absorber section and driving currents from 160 to 400 mA at the laser section with a minimum beatnote width of 6.6 kHz. The frequency comb spans over 13 nm with a mode spacing of 0.10 nm, measured by heterodyne-detection with a distributed feedback laser.

In this letter, we present evanescently coupled semiconductor laser arrays designed with a distributed Bragg reflector section for spectrally narrow emission and a combined waveguide section for high optical output powers. These devices were designed and fabricated in the AlGaAs material system with an InGaAsP quantum well providing emission in the 760–770 nm wavelength range. Measurements of the light-current characteristics reveal high optical output powers of 600 mW at 20 °C and 700 mW at 5 °C limited by thermal rollover without any signs of a catastrophic optical mirror damage or rapid power degradation. Spectrally narrow emission of 0.2 nm at −3 dB and a high wavelength stability with a small current tuning coefficient of 0.7 pm/mA were found. Far-field investigations reveal pre-dominant coupling of lowest order in-phase supermode emission without any sections for adjusting the phase of the electrical field vector for adjacent elements. Postprint

We have demonstrated that both ring quantum cascade (QCLs) and interband cascade lasers (ICLs) are excellent platforms for vertical light emission. Of these two lasers ICLs typically show lower power consumption and lasing threshold, qualifying them especially for miniaturized and battery-powered applications. With our work on ring ICLs we are aiming to build a compact portable sensing device, employing interferometric cavity-assisted photothermal spectroscopy. Here, we present our current work on interband cascade devices, as well as an overview of previous studies on ring QCLs. These devices rely on the light outcoupling via a second-order distributed-feedback grating from a ring cavity.

Interband cascade infrared photodetectors (ICIPs) combine interband optical transitions with fast intraband transport to achieve high-frequency and broad-wavelength operation at room temperature. Here we study the bias-dependent electronic impulse response of ICIPs with a mid-infrared synchronously pumped optical parametric oscillator (OPO). Since the OPO produces ultrashort 104-fs pulses, it is possible to probe the impulse response of the ICIP. From this impulse response, we identify two characteristic decay times, indicating the contribution of electron as well as hole carriers. A reverse bias voltage applied to the ICIP reduces both time scales and leads to an increased electrical cut-off frequency. The OPO emits up to 500 mW average power, of which up to 10 mW is directed to the ICIP in order to test its saturation characteristics under short-pulse illumination. The peak of the impulse response profile as well as the average photocurrent experience a gradual saturation behavior, and we determine the corresponding saturation powers by measuring the photo-response as a function of average power directed to the ICIP. We demonstrate that an increasing reverse bias increases the saturation power as well as the responsivity of the ICIP.

Funding: European Union Horizon 2020 research and innovation programme under grant agreement No 636930 (iCspec). The detection and measurement of hydrocarbons is of high interest for a variety of applications, for example within the oil & gas industry from extraction throughout the complete refining process, as well as for environmental monitoring and for portable safety devices. This paper presents a highly sensitive, selective and robust tunable laser analyzer that has the capability to analyze several components in a gas sample stream. More specifically, a multi-gas system for simultaneous detection of C1 to iC5 hydrocarbons, using a room temperature distributed feedback interband cascade laser array, emitting in the 3.3 micrometer band has been realized. It combines all the advantages of the tunable laser spectroscopy method for a fast, sensitive and selective in-line multicomponent tunable laser analyzer. Capable of continuous and milliseconds fast monitoring of C1-iC5 hydrocarbon compositions in a process stream, the analyzer requires no consumables (e.g. purging, carrier gas) and no in-field calibration, enabling a low cost of ownership for the analyzer. The system was built, based on an industrial GasEye series platform and deployed for the first time in field at Preem refinery in Lysekil, Sweden in autumn 2018. Results of the measurement campaign and comparison with gas chromatography instrumentation is presented. Postprint

Combination of FTIR spectroscopy with fiber optics provides a powerful diagnostic tool for diagnosing of human diseases, including osteoarthritis. To detect cartilage degradation, an arthroscopic probe based on polycrystalline fibers was developed and evaluated on equine cartilage specimen. The hook shape allows reaching a significant portion of the articular surface; the flat tip ensures avoidance of tissue destruction. Efficient QCL-coupling and stable transmission of PIR fibers under bending allows the assembling of effective thin arthroscopy probes and customized multispectral systems for medical diagnostic applications. The presented work was performed within the MIRACLE project (Grant Agreement No 780598, Horizon 2020).

We demonstrated widely tunable edge emitting single mode lasers based on the Vernier tuning principle using coupled cavities. We achieve a tuning range of 150nm with SMSR^30dB with central wavelengths at 2100nm and 2300nm.

Quantum cascade and interband cascade lasers are fabricated into surface and substrate emitting coherent light sources and detectors. We report about latest achievements in terms of power, temperature and dynamic performance of on-chip sensing systems.

We present ICLEDs emitting at peak wavelengths of around 3.7 µm. A record efficiency was achieved by growing the epitaxial structures on low doped substrates and positioning the active stages at antinodes of the optical field.

We present interband cascade light-emitting devices with incoherent and broadband light emission peaked at a wavelength of around 3.7 μm. The substrate-side-emitting devices display higher wall plug efficiencies and maximum output powers than any earlier mid-infrared LEDs operating in continuous wave at room temperature. To reduce absorption losses, the epitaxial structures were grown on low doped (low absorbing) GaSb substrates. The nine active stages were positioned in different configurations to investigate the impact of constructive or destructive interference when reflected from the epitaxial-side metallization of the flip-chip mounted devices. A comparison shows improved electrical properties and outcoupling efficiencies when all active stages are centered within a single antinode of the optical field. The optimized voltage efficiency combined with low optical losses lead to a maximum wall plug efficiency of 0.7%. Flip-chip mounted devices with a 640-μm squared mesa reached output powers of up to 5.1 mW at ambient temperatures with driving current (voltage) of 0.6 A (5.1 V). Publisher PDF

Interband cascade lasers (ICLs) [1,2] combine the concept of quantum cascade lasers (QCLs) and conventional photodiodes, because they rely on the voltage-efficient in-series connection of multiple active regions as in QCLs as well as the long upper-level recombination lifetimes of photodiodes. The distinctive low power consumption of ICLs makes them especially attractive for mobile applications in the mid-infrared, such as process control, medical applications and spectroscopy [3].

We have studied the optical and electronic transport properties of n-type AlSb/GaInAsSb double barrier quantum well resonant tunneling diodes (RTDs). The RTDs were grown by molecular beam epitaxy on GaSb substrates. Collector, quantum well, and emitter regions are comprised of the lattice-matched quaternary semiconductor Ga0.64In0.36As0.33Sb0.67. Photoluminescence emission spectra reveal a direct bandgap semiconductor with a bandgap energy of Eg≈0.37 eV, which corresponds to a cut-off wavelength of λ≈3.3 μm. The composition-dependent bandgap energy is found to follow Shim’s model. At room temperature, we observe resonance current densities of jres=0.143 kA cm−2 with peak-to-valley current ratios of up to PVCR=6.2. At cryogenic temperatures T

Laser light sources are routinely applied building blocks in optical sensor technologies. While lasers are emitting at a precisely defined wavelength within narrow emission bands, chem/bio-sensing applications frequently demand multi-wavelength illumination for addressing a series of species. Instead of using broadband radiation sources, it is a viable strategy to efficiently combine the beams emitted from different lasers to maintain the spectral brightness and yet cover extended wavelength regimes. In this study, substrate-integrated hollow waveguides (iHWGs) are reported as a versatile and efficient alternative compared to conventional beam combining concepts, especially for applications in the mid-infrared spectral regime leading to a highly efficient multi-port beam combiner—the iBEAM.

Funding: The authors are grateful for financial support received under Austrian Research Promotion Agency (FFG) project No. 1516332 (ATMO-SENSE). We present vertical light emission in continuous-wave mode from an interband cascade laser (ICL) at a record temperature of up to 38 °C. These results pave the way toward a more efficient and compact integration of this technology in mobile spectroscopic applications. Our approach employs ring cavity ICLs that are mounted epi-side down for efficient heat extraction from the devices. The vertical single-mode emission relies on a metallized second-order distributed-feedback grating designed for an emission wavelength of 3.8 μm. A single lateral mode operation is favored by a narrow waveguide width of 4 μm. Optical output powers of more than 6 mW were measured at 20 °C for rings with a diameter of ∼800 μm. At this temperature, the threshold current-density amounted to 0.60 kA/cm2 and the device showed continuous current and temperature tuning rates of 0.06 nm/mA and 0.37 nm/K, respectively. Publisher PDF

Molecule and gas sensing is a key technology that is applied in multiple environmental, industrial and medical fields. In particular optical detection technologies enable contactless, nondestructive, highly sensitive and fast detection of even smallest concentrations of trace gases and molecules. During the past years, an increasing demand for mid-infrared (MIR) light sources suitable for, e.g. molecule or gas sensing applications, has driven the development and optimization of novel MIR lasers and light sources, such as quantum cascade lasers (QCL) or interband cascade lasers (ICL). Despite the progress on MIR light sources, there is still a lack in appropriate MIR detectors. Here, we present and discuss two promising and novel GaSb/InAs-based detector concepts. First, resonant tunneling diode (RTD) photodetectors as an alternative to avalanche photodetectors. In RTDs, amplification of photogenerated minority charge carriers is based on modulation of a majority charge carrier resonant tunneling current. Second, interband cascade photodetectors (ICD), in which a cascading scheme allows for fast carrier extraction and a compensation of the diffusion length limitation.

The mid infrared spectral range (MIR) is of great interest for a variety of industrial, medical and environmental applications since numerous molecules have strong absorption lines therein. Interband cascade lasers (ICLs) have the ability to cover the entire MIR almost independently from the bandgap of the utilized semiconductors. Combined with a DFB technology which is applicable for most kinds of interband transition based semiconductor lasers the spectral range between 2.8 and 5.9 μm could be covered with application grade single mode devices with low power consumption. Recent optimizations regarding the layer design as well as the device processing yielded DFB laser chips with improved performance that will pave the way for a variety of applications that benefit from reasonable output power.

The authors acknowledge the support by the Austrian Science Fund (FWF) projects P26100-N27 (H2N) and NextLite (F4909-N23), and the State of Bavaria. HD acknowledges financial support through an APART fellowship from the Austrian Academy of Sciences. We demonstrate interband cascade lasers fabricated into ring-shaped cavities with vertical light emission through the substrate at a wavelength of λ ≈ 3.7 µm. The out-coupling mechanism is based on a metallized second-order distributed feedback grating. At room-temperature, a pulsed threshold current-density of 0.75 kA/cm2 and a temperature-tuning rate of 0.3 nm/°C is measured. In contrast to the azimuthal polarization of ring quantum cascade lasers, we observe a radial polarization of the projected nearfield of ring interband cascade lasers. These findings underline the fundamental physical difference between light generation in interband and intersubband cascade lasers, offering new perspectives for device integration. Publisher PDF

Financial support by the German Federal Ministry of Education and Research in terms of the APOSEMA project (contract no: 13N13083) within the funding program Photonics Research Germany is gratefully acknowledged. In this work, single-mode distributed feedback interband cascade lasers with tapered ridges are presented. The lasers consists of a 500 μm long and 5.7 μm wide ridge wave guide section followed by a 1400 μm long tapered section with an output facet width of 35 μm. The device is operational in continuous wave mode and well above room temperature. At 25°C, the threshold current and threshold current density were 81 mA and 324 A/cm², respectively. We demonstrate a tuning range of over 14 nm with side mode suppression ratios larger than 25 dB. The device showed temperature and injection power tuning coefficients of 0,35 nm/K and 4.09 nm/W, respectively. Output powers of 18 mW single mode and 35 mW multimode were achieved. Postprint

We present passive mode locking of a GaSb-based monolithic diode laser emitting at 2.2 μm with a fundamental repetition rate around 9.57 GHz. A pulse width of ∼2.4 ps is reconstructed by shifted wave intermode beat Fourier transform spectroscopy-measurements, yielding a time-bandwidth product of 1.8. Mode-locking is observed for a range of reverse bias voltages from 1.3 to 3.3 V and driving currents from 110 to 300 mA. The continuous wave output power is ∼17.5 mW with the absorber segment left floating and ∼4.5 mW at a reverse bias of 3.1 V in the mode-locked regime. The full-width-half-maximum of the radio frequency signal is measured for all operation conditions, with a minimum of 8.4 kHz.

A compact isotope ratio laser spectrometry (IRLS) instrument was developed for simultaneous measurements of the D/H, 18O/16O and 17O/16O isotope ratios in water by laser absorption spectroscopy at 2.73 μm. Special attention is paid to the spectral data processing and implementation of a Kalman adaptive filtering to improve the measurement precision. Reduction of up to 3-fold in standard deviation in isotope ratio determination was obtained by the use of a Fourier filtering to remove undulation structure from spectrum baseline. Application of Kalman filtering enables isotope ratio measurement at 1 s time intervals with a precision (

To the best of our knowledge, we present for the first time spectroscopic methane measurements using a laser diode at 3.3 μm operated in continuous mode at room temperature. The DFB-type laser emits a maximum optical output power of 1.5 mW with a spectral linewidth below 10 MHz. This novel kind of semiconductor laser allows precise photoacoustic measurements of characteristic methane absorption structures in the ν3 band. In addition, the setup enables a detection limit below 1 ppm.

Financial support by the European Union in terms of the WideLase project (grant agreement no: 318798) within the Seventh Framework Programme is gratefully acknowledged. Monolithic two-section interband cascade lasers offering a wide wavelength tunability in the wavelength range around 3.7 μm are presented. Stable single mode emission in several wavelength channels was realized using the concept of binary superimposed gratings and two-segment Vernier-tuning. The wavelength selective elements in the two segments were based on specially designed lateral metal grating structures defined by electron beam lithography. A dual-step dry etch process provided electrical separation between the segments. Individual current control of the segments allowed wavelength channel selection as well as continuous wavelength tuning within channels. A discontinuous tuning range extending over 158 nm in up to six discrete wavelength channels was achieved. Mode hop free wavelength tuning up to 14 nm was observed within one channel. The devices can be operated in continuous wave mode up to 30 °C with output powers of 3.5 mW around room temperature. Postprint

We are grateful for receiving financial support within the BMBF Project “LASELO” (FKZ: 13N13773). Interband cascade lasers (ICLs) with dual wavelength emission have been realized by utilizing two spatially separated active regions in the same device. The two wavelengths (3.1 and 3.7 µm) were chosen in order to demonstrate that the usual spectral gain bandwidth of an ICL can be overcome. At 20°C, threshold current densities as low as 215 A/cm² (short wavelength) and 158 A/cm² (long wavelength) could be achieved in pulsed mode. It was possible for an epi-up mounted device to maintain dual-wavelength continuous-wave emission up to 0°C. Despite the longer wavelength emission being suppressed at higher temperatures, the shorter wavelength maintained an output power of more than 10 mW at 15°C. Postprint

GaInNAs-based high-power laser diodes with emission in the 1220-1240 nm wavelength range are presented. Broad-area (BA) devices show very low internal losses of only 0.5 cm-1, allowing high continuous-wave room-temperature output powers of almost 9 W and emission at a wavelength of 1220 nm. Based on the needs for applications like, e.g., pumping of Raman amplifiers, wavelength-stabilized tapered laser diodes are shown with maximum output powers of 1 W together with a high beam quality. Beam propagation factors M 2 down to 1.4, high brightness of up to 23 MW/cm2middotsr, and nearly spatial single-mode emission have been obtained.

The authors acknowledge support the European Cooperation in Science and Technology (COST) Action BM1205. This research was supported under Australian Research Council’s Discovery Projects funding scheme (DP 120 103703) and the State of Bavaria. Y.L.L. acknowledges support under the Queensland Government’s Smart Futures Fellowships programme. P.D. acknowledges support from the EPSRC (UK). S. H. gratefully acknowledges support by the Royal Society and the Wolfson Foundation. In this work, we demonstrate a simple square-wave electrical modulation scheme for imaging with laser feedback interferometry (LFI). Distinct advantages of this scheme include (a) the straightforward creation of the modulating signal, even for high-current lasers, and (b) its natural suitability for lock-in detection. We compare this simple scheme against two established imaging modalities for LFI: mechanical modulation using an optical chopper and the swept-frequency feedback interferometry approach. The proposed scheme lends itself to high frequency modulation which paves the way for high frame-rate LFI imaging with no motion artefacts using off-the-shelf equipment. Publisher PDF

The authors acknowledge the financial support from the European Commission in the frame of the FP7 project “WideLase” (Grant No. 318798). Single mode emission of InAs-based interband cascade lasers using lateral metal gratings that provide distributed feedback is presented. A double ridge configuration was developed, where the grating is placed above the active region while a second, slightly wider ridge ensures current confinement in the active region. Side mode suppression ratios above 30 dB have been obtained, and single mode emission was observed at wavelengths around 6 μm in continuous-wave operation up to a temperature of -10 °C. Current- and temperature-tuning rates of 0.011 nm/mA and 0.50 nm/ °C, respectively, have been found, and a total tuning range of 6.5 nm has been covered by one device. As a reference, ridge waveguide devices without a grating made from the same material were able to emit in pulsed mode up to 49 °C and in continuous-wave operation at temperatures up to 0 °C around 6 μm. Publisher PDF

20 years after their first reference interband cascade lasers (ICLs) have become a mature and competitive semiconductor laser source in the mid-infrared region. The carrier rebalancing concept that was introduced in 2011 drastically improved the performance. As a consequence the wavelength window that is accessible for ICLs operating at ambient temperatures could be extended. For GaSb based ICLs continuous wave (cw) emission at room temperature could be achieved up to a wavelength of 5.6 μm. As the need for thicker claddings at longer wavelengths makes the growth of the superlattice claddings increasingly difficult and limits the heat dissipation, a plasmon waveguide structure with highly doped InAslayers grown on InAs-substrates is typically used for ICLs emitting up to ~7 μm in pulsed mode at room temperature. With regard to the short wavelength limit of ICLs, we present cw emission of a GaSb based ICL emitting at 2.8 μm and with regard to the long wavelength limit we present room temperature pulsed operation of an InAs based plasmonic waveguide ICL up to 7.1 μm. Furthermore, we show single mode emitting ICLs with distributed feedback gratings emitting between 2.8 and 5.2 μm.

Financial support by the European Commission within the WideLase Seventh Framework Programme Project (Grant Agreement No.: 318798) is gratefully acknowledged. In this work, single-mode distributed feedback (DFB) interband cascade laser (ICL) devices with record short wavelength emission below 2.8 μm are presented. Pulsed measurements based on broad area laser devices with a cavity of 2 mm length and 150 μm width showed threshold current densities of 383 A/cm2 at T = 20 °C and a characteristic temperature T0 of 67 K. Fabricated DFB devices were operated in continuous wave mode at room temperature, with threshold currents of 57 mA and demonstrated side mode suppression ratios of larger than 25 dB. The devices showed current tuning ranges of 7 nm and total (including drive current and temperature) tuning ranges of 12 nm, with respective tuning rates of 21 nm/W, 0.13 nm/mA and 0.29 nm/K. Using the full spectral gain bandwidth of the underlying ICL material, single-mode DFB emission was observed within a wavelength range of 150 nm utilizing different DFB grating periods. Publisher PDF

In recent years, the use of laser sources in gas sensing applications has been increasing continuously. Tunable Laser Absorption Spectroscopy (TLAS) has proven to be a versatile tool in a variety of sectors including industry, health and security and modern environmental analysis. Especially the mid-infrared wavelength range is of great interest for high accuracy gas sensing applications, since many technologically and industrially relevant gas species have their strongest absorption features in the spectral region between 3 and 6 μm. These include, e. g., important hydrocarbons like methane or propane, as well as nitric oxide and formaldehyde. Interband cascade lasers (ICL) provide mono mode continuous wave (CW) operation above room temperature in this wavelength range. Application-grade complex coupled distributed feedback (DFB) laser devices based on the ICL concept are presented, using lateral metal gratings as wavelength selective elements. The fabricated devices operate at specific, technologically relevant, emission wavelengths in the spectral region from 3 to 6 μm. CW operation up to 80 °C and mono mode wavelength tuning ranges above 20 nm were achieved with low energy consumption. Application examples in industry and research are presented that demonstrate the high potential of DFB ICLs for the use in TLAS. E. g., formaldehyde gas sensor systems based on DFB ICL devices operating around 3.6 μm can provide realtime in-situ measurements with resolution limits in the low ppb range, even in dense background atmospheres. The low power consumption of ICL based devices makes them especially favorable for battery-powered or portable sensor applications.

Auf der Basis von GaAs/AlGaAs-Heterostrukturen wurden monomodige Quantenkaskadenlaser im Wellenlängenbereich von 9–11 μm entwickelt. Die Rotations-Schwingungs-Grundzustände vieler industriell wichtiger Gase fallen in diesen Spektralbereich im mittleren Infrarot. Daher eignen sich diese Laser in besonderem Maße für den sensitiven Nachweis von beispielsweise CO2 (9,5 μm Wellenlänge), O3 (9,7 μm) und NH3 (10,7 μm). Die Laser werden auf standardisierte c-mounts montiert, die sehr einfach in komplexere Optikmodule eingebaut werden können. Im gepulsten Betrieb liefern die hergestellten Bauteile bei Peltiertemperaturen Ausgangsleistungen von einigen mW und erweisen sich aufgrund ihres kontinuierlichen Durchstimmbarkeitsverhaltens der Emissionswellenlänge insbesondere für spektroskopische Anwendungen als geeignet.

Since the first realization of quantum cascade lasers (QCL) in the GaAs material system in 1998, large progress has been made in the device performance of GaAs-based QCLs. However, the relatively high threshold current density of GaAs-based QCLs compared to InP-based QCLs is still the main obstacle for achieving high-temperature continuous wave operation in the GaAs material system. In this work, we investigate the GaAs/Al 0.45 Ga 0.55 As QCL-design published by Page et al. [Appl. Phys. Lett. 78 (2001) 3529] with 48 active periods embedded in a plasmon enhanced waveguide structure. The optimization of the growth conditions resulted in high-quality quantum cascade structures with operation temperatures up to room temperature. Essential for the fabrication of the high-quality layers was the use of different arsenic fluxes for the waveguide and the active region layers. Furthermore, we varied the doping level in the injector region and we found a strong dependence of this parameter on the threshold current density. The threshold current density is significantly reduced by a factor of 2 due to a decrease of the sheet carrier density by a factor of only 1.6.

Distributed feedback (DFB) laser sources are key components of modern gas analyzers based on tunable laser absorption spectroscopy. While the current induced tuning range of DFB lasers is usually limited to a few nanometers, there are a number of applications which will benefit from lasers with a wider tunability, e.g. multi-gas sensing or spectroscopy of liquids. In this paper, we present monolithic widely tunable laser devices in the 3.6 μm wavelength region based on interband cascade laser material. Using the concept of binary superimposed (BSG) grating structures and two-segment Vernier-tuning, stable single-mode emission is realized at discrete wavelength channels in the 3560 nm to 3620 nm region. A total tuning range around 60 nm in three channels is demonstrated. Within a single channel, the emission wavelength can be tuned mode hop free over up to 5 nm. The wavelength channels can be arbitrarily placed in the range of the material gain, allowing BSG lasers to sweep over several gas absorption lines. The number of channels can be chosen as well. Within a wavelength channel, the lasers show DFB like spectral performance with setup limited sidemode suppressino ratios around 25 dB and milliwatt levels of continuous wave output powers around room temperature. This paper will present an overview of the laser concept, simulations, performance data and applications.

Single mode interband cascade lasers targeting the Mid-IR absorption features of important gases are presented. Application examples for industrial process control and environmental monitoring with sensitivity in the low ppb range are described.

A mid-infrared sensor for sulfur dioxide in emission monitoring applications using a monomode DFB ICL at 4 μm and second harmonic detection has been developed. The detection limit of the sensor is below 3 ppm·m.