The mid-infrared (MIR) free-space optical (FSO) transmission systems based on quantum cascade laser (QCL) have attracted substantial attention. Nevertheless, a major limitation persists at the receiver side, which remains dominated by mercury cadmium telluride (MCT) detectors due to the lack of competitive alternatives. This prevalent reliance is particularly problematic in the mid-wave infrared (MWIR) band, where MCT detectors are fundamentally constrained by limited modulation bandwidth and cooling requirements. This study explores the potential of MWIR FSO transmission that leverages an MWIR uni-traveling carrier photodiode (UTC-PD) to attain high-speed communication. We present an experimental demonstration of an MWIR FSO link at 4.65 μm, combining a directly-modulated (DM) QCL with an uncooled UTC-PD detector based on InAs/InAsSb type-II superlattices. A transmission data rate of up to 14 Gb/s over a 31-m optical path length (OPL) is successfully achieved, demonstrating superior performance compared to a benchmark commercial MCT. Our findings suggest that the UTC-PD-based MIR FSO receiver offers a promising solution towards the next generation of optical wireless communication networks.

We report the first system-level MWIR FSO demonstration at 4.65 mu m, combining a directly modulated QCL with an uncooled uni-traveling carrier photodiode (UTC-PD), achieving 14 Gb/s transmission over a 31-m optical path length using a Herriott cell. (c) 2025 The Author(s)

In this work, we investigate data transmission in the long wavelength infrared spectrum employing a directly-modulated quantum cascade laser and a quantum cascade detector in ridge architecture, both operating at a wavelength around 9 mu m. We were able to measure bit rates of 200 Mbps for a two-level (OOK) modulation scheme in a back-to-back configuration at room temperature. The findings of this study pave the way for further development of these devices to be employed in integrated photonic circuits for advanced applications in secure and high-speed free-space optical communications.

Chalcogenide glasses have attracted attention for sensing applications due to their high transparency in the infrared range, their ability to be fabricated into thin films by PVD and to be processed into integrated photonic components by photolithography and etching. We will present the development of a chalcogenide-based mid-infrared platform dedicated to mid-infrared spectroscopy using evanescent waves. This study represents an important step towards the development of an optical sensor in the MIR spectral range using chalcogenide materials for the detection of organic molecules in water.

This talk will discuss the recent improvements and future developments of Mirsense's quantum cascade lasers (QCLs) for Directional Infrared Countermeasures (DIRCM). Specifically, the talk will focus on the increase in power and beam quality of QCLs, enabling them to be used for DIRCM applications. The advantages of QCLs compared to other lasers for DIRCM will be discussed, as well as the challenges and potential solutions. The talk will also provide an overview of the current state of the technology and discuss future roadmaps for further improvements. Lastly, the potential of QCLs in other applications where high power and beam quality are required will be discussed.

We demonstrate the development of calibration-free intrapulse spectrometer for in-situ measurements with compact dense pattern multipass absorption cell using Quantum Cascade Laser at 4.47 μm.

With the emergence of Internet Of Things (IOT), the fast increment of users and the space development has opened the research towards free-space optics (FSO) using mid-infrared (MIR) wavelengths. Despite promising results have already been achieved in the $1.5\ \upmu\mathrm{m}$ wavelength range, the mid-infrared domain offers several other advantages in particular a strong resistance to various atmospheric impairments [1]. Specifically, the $8-14\ \upmu\mathrm{m}$ range has a high atmospheric transparency, strong resistance to degraded atmospheric conditions including turbulence [2]. For an eavesdropper, intercepting the beam through the atmosphere is more difficult because of significant thermal radiation in this range of wavelength. As MIR technology becomes more and more mature with recently demonstrated data transfers of several tens of Gbps it also becomes urgent to focus on the security and to innovative alternatives to ensure data privacy [3].

The gas phase detection of ethanol $(\mathrm{C}_{2}\mathrm{H}_{6}\mathrm{O})$ is currently performed either qualitatively by chemical breathalyzers or quantitatively by electrochemical or metal oxide semiconductor sensors. However, the latter suffer from poor selectivity and can be interfered by a number of volatile organic compounds, including those naturally present in exhaled breath [1]. In addition, a regular calibration of these devices is necessary to ensure the accuracy of the measurements made.

Buried heterostructure quantum cascade lasers (BH-QCLs) operating at high temperature in mid-infrared (MIR) to THz spectral range are desired for chemical sensing and free-space optical communication (FOC). In this work, Fe doped semi-insulating InP (SI-InP) regrowth is demonstrated in a hydride vapor phase epitaxy (HVPE) reactor for advanced MIR and THz BH-QCLs grown by MBE and MOCVD. SI-InP regrowth is implemented in THz QCL pillar arrays and narrow width and reverse-taper MIR BH-QCLs for efficient heat dissipation. By exploiting SI-InP regrowth, the parasitic capacitance in MIR distributed feedback BH-QCL can be suppressed, which is exploited for high speed FOC application.

A roadmap for future wireless communications is expected to exploit all transmission-suitable spectrum bands, from the microwave to the optical frequencies, to support orders of magnitude faster data transfer with much lower latency than the deployed solutions nowadays. The currently under-exploited mid-infrared (mid-IR) spectrum is an essential building block for such an envisioned all-spectra wireless communication paradigm. Free-space optical (FSO) communications in the mid-IR region have recently attracted great interest due to their intrinsic merits of low propagation loss and high tolerance of atmospheric perturbations. Future development of viable mid-IR FSO transceivers requires a semiconductor source to fulfill the high bandwidth, low energy consumption, and small footprint requirements. In this context, quantum cascade laser (QCL) appears as a promisingtechnological choice. In this work, we present an experimental demonstration of a mid-IR FSO link enabled by a 4.65-μm directly modulated (DM) QCL operating at room temperature. We achieve a transmission data rate of up to 6 Gbps over a 0.5-m link distance. This achievement is enabled by system-level characterization and optimization of transmitter and receiver power level and frequency response and assisted with advanced modulation and digital signal processing (DSP) techniques. This work pushes the QCL-based FSO technology one step closer to practical terrestrial applications, such as the fixed wireless access and the wireless mobile backhaul. Such a QCL-based solution offers a promising way towards the futuristic all-spectra wireless communication paradigm by potentially supporting the whole spectrum from the MIR to the terahertz (THz).

In this paper, we describe a technique to perform intracavity gas sensing by detecting changes in the QCL voltage. The influence of mode-hops is compensated by a data acquisition and processing based on a dual wavelength scanning. This allows to perform gas detection over the full cavity spectral range (1277 cm(-1) - 1348 cm(-1)) without the use of a mode-hop free setup. First results of measurement of the CH4 absorption spectrum are presented.

We experimentally display temporal chaotic waveforms in the mid-infrared domain with two different types of semiconductor lasers. The generated high-dimensional non-linear dynamics are of prime interest for private communications and physical random number generation.

We present the design, fabrication and the characterisation of compact and widely tuneable MIR source. This device is based on an INP micro-lenses array and on a DFB QCL array. Both of those arrays are designed together to induce a beam combination.This work presents one complete device for wavelength between 8.5 and 9.5 µm with a typical size of 5*2 mm² designed for one specific solid spectroscopic application.

Interband cascade lasers are semiconductor lasers emitting in the mid-infrared domain but relying on interband transitions, contrary to their intersubband counterparts, quantum cascade lasers. Our experimental study of the relative intensity noise in a multi-mode interband cascade laser at 4.1 μm shows that the room-temperature structure exhibits a relaxation frequency in the GHz range. We demonstrate that, far above the threshold current, the relaxation frequency increases with the bias current, and our simulations are in good agreement with our experimental efforts. Fitting of the relative intensity noise resonances gives access to several intrinsic parameters of the interband cascade laser under study such as differential gain, compression gain, and K-factor. This study is a clear step for understanding dynamics interplays in interband cascade laser structures, which means understanding the non-linear and modulation bandwidth limitations of such lasers.

Mid-infrared free-space optical communication has a large potential for high speed communication due to its immunity to electromagnetic interference. However, data security against eavesdroppers is among the obstacles for private free-space communication. Here, we show that two uni-directionally coupled quantum cascade lasers operating in the chaotic regime and the synchronization between them allow for the extraction of the information that has been camouflaged in the chaotic emission. This building block represents a key tool to implement a high degree of privacy directly on the physical layer. We realize a proof-of-concept communication at a wavelength of 5.7 μm with a message encryption at a bit rate of 0.5 Mbit/s. Our demonstration of private free-space communication between a transmitter and receiver opens strategies for physical encryption and decryption of a digital message.

We report on the first experimental chaos synchronization in mid-infrared quantum cascade lasers and subsequently perform private free-space transmission at a bit-rate of 0.5 Mbits/s. The quality of the privacy is assessed with eye diagrams, both at the legitimate receiver side and illegitimate receiver side.

We experimentally realize a free-space transmission over one meter with room-temperature quantum cascade lasers and interband cascade lasers. With direct electrical modulation and raw analysis, the data-rate of the real-time transmission outperforms similar reported schemes.

Spectroscopic techniques based on Distributed FeedBack (DFB) Quantum Cascade Lasers (QCL) provide good results for gas detection in the mid-infrared region in terms of sensibility and selectivity. The main limitation is the QCL relatively low tuning range (~10 cm−1) that prevents from monitoring complex species with broad absorption spectra in the infrared region or performing multi-gas sensing. To obtain a wider tuning range, the first solution presented in this paper consists of the use of a DFB QCL array. Tuning ranges from 1335 to 1387 cm−1 and from 2190 to 2220 cm−1 have been demonstrated. A more common technique that will be presented in a second part is to implement a Fabry–Perot QCL chip in an external-cavity (EC) system so that the laser could be tuned on its whole gain curve. The use of an EC system also allows to perform Intra-Cavity Laser Absorption Spectroscopy, where the gas sample is placed within the laser resonator. Moreover, a technique only using the QCL compliance voltage technique can be used to retrieve the spectrum of the gas inside the cavity, thus no detector outside the cavity is needed. Finally, a specific scheme using an EC coherent QCL array can be developed. All these widely-tunable Quantum Cascade-based sources can be used to demonstrate the development of optical gas sensors.

The mid-infrared (MIR) molecular fingerprint region has gained great interest in the last past years thanks to development of laser source like Quantum Cascade Lasers (QCL). There are a lot of efficient technique to achieve solid and liquid spectroscopy detection. However, to probe several or complex molecules in this optical region, it could be necessary to use broadly tunable MIR source. A QCL array coupled to a specific lens array able to shape and combine beams into a single spot, could be a suitable source. This work is focused on the design and fabrication of integrated lenses (Photonic Crystal Lens & Quasi Photonic Crystal Lens) made with Germanium on Silicon Germanium platform. A Photonic Crystal Lens (PCL) is composed of a 2D holes lattice inside of a slab waveguide led with Si0.6Ge0.4. The holes lattice is hexagonal with a constant parameter. The radius of those holes continuously varying, in the direction perpendicular to the light propagation, to induce a variation in optical path length. Then, the design of this gradient is the key to perform the desired lens function. A Quasi Photonic Crystal Lens (QPCL) is based on the same principle as the PCL, but instead of having a 2D lattice there is a linear (1D) lattice. So a QPCL is composed of 1 row of a fixed number of macroscopic holes in diamond pattern inside of a slab waveguide. Like the PCL, there is a hole size gradient to shape the optical path of the light. This works shows simulation results and the first design of integrated lens working at the wavelengths of ≈ 9µm with a focal of ≈ 200µm and with a side size (in the array direction) of 200µm.

Quantum cascade lasers are the most powerful and efficient mid-IR semiconductor technology. Their niche market has a strong annual growth and provides decisive advantages over other mid infrared laser technologies. As a semiconductor laser, QCLs are small and the direct conversion from electricity to light ensures a high conversion efficiency. mirSense has been developing quantum cascade laser-based solutions for 5 years now and ranks among the very few companies mastering this technology. The main value brought by this technology in this market is to deliver coherent and bright sources in the band II and band III of transmission of the atmosphere. We focus in particular on the application of this technology to defense applications like DIRCM. Our strong innovation propensity has lead us to build a strong IP and innovative solutions.