This PDF file contains the front matter associated with SPIE Proceedings Volume 12738, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

With the recent establishment of the Dutch Defence Space Security Center (DSSC), the MoD is tasked with the development of Space Situational Awareness for which a variety of systems are required. A breakdown of the need for SSA from a MoD perspective will be provided as well as how the DSSC strives to develop this capability. Further a brief insight towards future requirements will be given as well as how new technologies can help a relatively small MoD with developing relevant assets that directly support operations. Cooperation is sought with institutes and industry in order to develop the relevant knowledge, technologies and capabilities. Finally an overview of the Netherlands SSA ecosystem will be given. In particular the Netherlands Organisation for Applied Scientific Research (TNO) will present the optomechanical instruments and sensors for both ground and space SSA applications which is currently developing and testing

Directed Infrared Countermeasure (DIRCM) systems are crucial for effective defence against modern infrared-guided threats. These systems provide significant advantages over traditional countermeasures, including rapid, precise, deep-magazine, and automatic response capabilities. These capabilities have the potential to thwart even the most advanced threats. However, realising this potential requires overcoming the problem of "home on jam," caused by a dazzled scene indicating the location of the laser from a simple profile. To address this issue, we propose a novel approach that considers dazzling as a dynamic property, aiming not to obscure the target completely but instead deceive the seeker through false targets. This paper assesses the impact of various approaches to confuse an infrared imager with the laser beam's varying spatial and temporal properties. We quantify the effect using scale-invariant template matching AI, comparing the similarity and the impact of laser and image properties on the effectiveness of in-band dazzling. Specifically, we use a Quantum Cascade Laser (QCL) with a peak wavelength of 4.6 microns to illuminate a thermal infrared imager within the 3 to 5 microns (MWIR) operating band. We project silhouette targets on the imager, representing aerial targets of interest, in the location of the imaged laser spot. Our findings highlight the importance of considering dynamic dazzle properties to overcome the home-on-jam problem. Our proposed approach shows promising results by utilising multiple targets and varying the spatial and temporal properties of the laser beam. We use several template-matching metrics to demonstrate the efficacy of our strategy and provide insights into how laser and image properties impact its effectiveness.

Laser dazzling is both a threat and offers a survival capability in military scenarios. Dazzling may blind or mislead optically directed or guided weapons as well as temporarily dazzle operators in critical situations. Laser dazzlers can also serve as warning devices in checkpoint and riot control and other situations. While laser damage of sensors may be an alternative, this is generally more difficult due to the demand on high energy short pulse lasers. The development of small (handheld or weapon mounted) compact laser dazzlers at various wavelength continue to develop and are being a threat to sensors in all wavelength bands, from the visible to thermal IR. This paper will discuss some tactical considerations for the use of laser dazzlers in all optical bands from the visible to thermal IR.

Laser dazzling is a threat both to military and civilian operations. It also enables protection capabilities against hostile fire from different kind of weapons. Laser dazzlers can also serve as warning devices in checkpoint and riot control and others. Williamson and McLin has presented a model for eye laser dazzling partly based on the earlier framework for laser safety calculations. We have used this model to investigate dazzling performance for humans under different atmospheric condition such as scattering, extinction and turbulence. We also shortly discuss the influence of optics in front of the eye such as windshields or magnifying optics. The results will be discussed in relation to potential scenarios.

Composites are subject to a wide variety of physicochemical processes when exposed to laser radiation. Pyrolysis, flow of reaction volatiles and char formation have a considerable influence on the heating process. In this contribution, some of these processes and their impact on the thermal and optical properties of glass-fiber reinforced polymers (GFRP) will be discussed with focus on charring and its impact. Modelling of the thermal and mechanical behavior with all processes occurring will be difficult to realize. With prioritization and concentration on the main processes of pyrolysis, the spatio-temporal thermal evolution was calculated by numerical FEM calculations. Based on the Arrhenius equation, the thermo-dynamical conversion rate was calculated. This transfer from virgin composite to charred material also affects the optical behavior. Absorption and scattering were considered by the photon diffusion equation in the unmodified material, whereas in charred material the laser radiation was assumed to be absorbed already within a small penetration depth.

The laser radar cross section (LRCS) is a parameter for describing the reflective properties of targets, illuminated by laser light. As the role of lasers in remote sensing continues to grow in the automotive, or military fields, a proper measurement methodology for the laser radar cross section of various objects, especially in a laboratory environment, is crucial. In this contribution we performed preliminary investigations in a laboratory environment on the laser cross section of different optical components such as mirrors. The research focus hereby is put on the influence of various measurement parameters of the setup with respect to the measured LRCS. Such parameters are for example different angles of incidence, beam size and beam quality.

Spatial division multiplexing is a means of transmitting information on independent spatial modes and is being investigated as a means of increasing capacity in optical communications in both optical fibres and free space. Multiplane light converters (MPLC) are a means of deconstructing a wavefront into constituent modes that focus at specific spatial locations, and the reverse - that specific inputs result in controlled modal output. We have used a pair of MPLCs with 21 Hermite Gaussian modes to represent a free space optical connection with multiple single-input multiple-output (SIMO) operation. The effects of atmospheric turbulence have been implemented using a micromirror array and represent atmospheres that vary from weak (C_n²=10^-16 m^-2/3) to strong (C_n²=10^-13 m^-2/3) turbulence. This allows the resulting crosstalk between modes in the receiver to be characterised and modal transmission choice selected to minimise the crosstalk effects. Spatial division multiplexing is shown to improve the resilience against the degrading effects of turbulence, increases detection efficiency and offers an alternative method of compensating for turbulence effects using post detection digital signal processing rather than physical wavefront manipulation using adaptive optics.

The multi-sensor, high accuracy, 4 axes gyro-stabilised turret system (LEOSS-T) designed by LEONARDO SPA - Electronics Division for airborne surveillance applications has been transformed in a 3kW Power Laser Effector substituting one of the sensor with the Optical Head of a 3 kW single mode IPG Fiber Laser. Inside the LEONARDO LASER Facility, we demonstrated that the LEOSS Laser Effector system is able to: detect and track a micro drone; determine and maintain the aim point for the time necessary to obtain the desired effect on the target. Drone Dazzling and shooting-down have been tested. Demonstration setup and results are presented.

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 investigated the temperature dependence of a multi-watt thulium-doped fiber laser. For high-power laser operation, thulium-doped fiber lasers are often pumped in the cladding by diode lasers operating at 793 nm to take advantage of the cross-relaxation effect. However, these diode lasers have to be temperature stabilized since the 3H4 absorption band in thulium-doped fibers is narrow and, therefore, not suitable for passively cooled setups. In contrast in-band pumping into 3F4 is an alternative, benefiting from a broad absorption band. The investigated thulium-doped fiber laser is core-pumped by an in-house built erbium:ytterbium-codoped fiber laser. In order to keep the surrounding temperature defined, the thulium-doped fiber was integrated into a metal plate with grooves and embedded in a thermal interface material. In addition, the metal plate was mounted on Peltier elements to control its temperature. During the experiment, the temperature of the metal plate was changed between -20°C and 80°C while the output power, slope efficiency and electrooptical efficiency of the thulium-doped fiber laser were measured. The performance of the laser versus temperature is reported and show minor dependence over a broad temperature range.

We report on laser resonators with a segmented and a homogeneously doped Ho³⁺:YAG crystal delivering over 60 W of output power with near-diffraction-limited beam quality. The resonators with both crystals exhibit high slope efficiencies around 67% and maximum pulse energies of 1.14 mJ and 1.04 mJ are measured for the homogeneously doped and segmented crystal, respectively, at a repetition rate of 50 kHz. Q-switched pulses with a pulse peak power of 108 kW are generated with the homogeneous crystal at a repetition rate of 25 kHz. In a slight redesign of the cavity, 1:24 mJ, 33 ns pulses with a pulse peak power of 38kW are measured.

Laser safety with regard to the human eye is a well-known topic. Everybody working with laser sources has to follow the long-established occupational safety rules to prevent people from eye damage by accidental irradiation. These rules comprise, for example, the use of laser safety eye-wear and the calculation of the Maximum Permissible Exposure (MPE) and its corresponding hazard distance, the Nominal Ocular Hazard Distance (NOHD). At exposure levels below the MPE, glare effects may occur if the laser wavelengths are in the visible spectral range. The physical effects of laser dazzling on the human eye are described by a quite new concept, which defines the Maximum Dazzle Exposure (MDE) and the corresponding Nominal Ocular Dazzle Distance (NODD). Triggered by the MDE/NODD concept, we investigated whether similar laser safety calculations could be performed for electro-optical imaging systems. In this publication, we will review our approach for laser safety calculations for such systems. We have succeeded to find closed-form equations allowing calculations of exposure limits to prevent electrooptical imaging systems from damage and/or dazzle. Furthermore, we found some interesting effects related to the corresponding hazard distances, which are also discussed.

Laser dazzling can cause visual performance degradation in humans, resulting in reduced accuracy and reaction times. This study presents the results from laser dazzling trials conducted on trained shooters in a shooting simulator at the Royal Military Academy (RMA) in Brussels, Belgium. The main objective was to assess the extent of task performance degradation induced by laser dazzle, while also investigating the impact of different experimental conditions, including target contrasts and the use of laser eye protection goggles. The shooting simulator was equipped with a 532 nm green dazzling laser, providing a safe yet noticeable dazzling effect. Participants, all trained shooters with similar experience, had their shooting scores and delays recorded for each shot. A statistical analysis, employing a linear mixed model, was conducted to assess the impact of laser dazzling on shooting performance. The findings showed that laser dazzling significantly and quantifiably affected shooting performance, even at exposure levels below the obscuration limits. Additionally, shooters wore sensorized headbands to assess electroencephalography (EEG) changes to the presented stimuli. Preliminary results from the statistical analysis of the EEG data are also presented, offering insights into the shooters' cognitive and emotional state during laser dazzling exposure.

Lasers are widely used in daily activities; they are found everywhere from simple laser pointers to remote sensing devices. When a high level of laser radiation is reaching the human eyes or any imaging devices it will disrupt the vision creating what is called a dazzle effect. This effect is used by the military to decrease the combat efficiency of an enemy. Various laser dazzlers were manufactured to target personnel as well as optoelectronic devices such as cameras and missile sensors. The most advanced ones use three different wavelengths to target all the visible range and all the sensors of the imaging device. In this work, the reduction of the laser dazzle effect on focal plane array cameras is performed using two different image processing algorithms. The results show that there is a notable reduction of the dazzle effect and a massive improvement in the field of view in the enhanced images. More details can be recovered and visualized in the areas out of the central spot.

Many metallic and carbon-based nanomaterials exhibit nonlinear optical response under intense laser radiation, what makes them promising for laser protection devices. They strongly attenuate intense laser light, while exhibiting high transmittance at low irradiation levels. This nonlinear optical phenomenon is called optical limiting. In recent years, boron nitride nanomaterials have attracted increasing attention due to their unique properties such as high temperature stability and high thermal conductivity. They are structurally analogous to carbon nanomaterials and can also be generated as zero-dimensional nanoparticles and fullerenes, one-dimensional nanotubes and nanoribbons and two-dimensional nanosheets or platelets. In contrast to carbon-based nanomaterials, which have been extensively studied during recent years, the nonlinear optical properties of boron nitride nanomaterials have hardly been analysed so far. In this work, we present a comparative study on the nonlinear optical response of dispersed boron nitride nanotubes, boron nitride nanoplatelets, boron nitride nanoparticles and multi-walled carbon nanotubes using nanosecond laser pulses at 532 nm. Our measurements revealed that nonlinear scattering dominates the optical limiting performance of all measured boron nitride nanomaterials. Boron nitride nanotubes are a very good candidate for laser protection applications, they show a large optical limiting effect, much stronger than multi-walled carbon nanotubes.