Optoelectronic devices operating in the mid-wave (3-5 Μm) and long-wave (8-12 Μm) infrared (IR) regions of the electromagnetic spectrum are of a great interest for academic and industrial applications. Due to the lack of atmospheric absorption, devices operating within these spectral bands are particularly useful for spectroscopy, imaging, and dynamic scene projection. Advanced IR imaging systems have created an intense need for laboratory-based infrared scene projector (IRSP) systems which can be used for accurate simulation of real-world phenomena occurring in the IR. These IRSP systems allow for reliable, reproducible, safe, and cost-effective calibration of IR detector arrays. The current state-of-the-art technology utilized for the emitter source of IRSP systems is thermal pixel arrays (TPAs) which are based on thin film resistor technology. Thermal pixel array technology has fundamental limitations related to response time and maximum simulated apparent temperature, making them unsuitable for emulation of very hot (> 700 K) and rapidly evolving scenes. Additionally, there exists a need for dual wavelength emitter arrays for IRSP systems dedicated to calibration of dual wavelength detector arrays. This need is currently met by combining the spectral output from two separate IRSP systems. This configuration requires precise alignment of the output from both systems and results in the maximum radiance being limited to approximately half that of the capability of a given emitter array due to the optics used to combine the outputs. The high switching speed inherent to IR light-emitting diodes (LEDs) and the potential for high power output makes them an appealing candidate to replace the thermal pixel arrays used for IRSP systems. To this end, research has been carried out to develop and improve the device performance of IR LEDs based on InAs/GaSb type-II superlattices (T2SLs). A common method employed to achieve high brightness from LEDs is to incorporate multiple active regions, coupled by tunnel junctions. Tunnel junctions must provide adequate barriers to prevent carrier leakage, while at the same time remain low in tunneling resistance to prevent unwanted heating. The performance of two tunnel junction designs are compared in otherwise identical four stage InAs/GaSb superlattice LED (SLED) devices for application in IRSP systems. This research culminated in the development of a 48 Μm pitch, 512$times512 individually addressable mid-wave IR LED array based on a sixteen stage, InAs/GaSb T2SL device design. This array was hybridized to a read-in integrated circuit and exhibited a pixel yield greater than 95 %. Projections based on single element emitter results predict this array will be able to achieve a peak apparent temperature of 1350 K within the entire 3-5 Μm band. These results demonstrate the feasibility of emitter arrays intended for IRSP systems based on InAs/GaSb SLED devices. Additionally, a dual wavelength 48 Μm pitch, 8x8 emitter array based on InAs/GaSb T2SL LEDs was developed and demonstrated. This design incorporates two separate, 16 stage InAs/GaSb SL active regions with varying InAs layer thicknesses built into a single vertical heterostructure. The device architecture is a three terminal device allowing for independent control of the intensity of each emission region. Each emitter region creates a contiguous pixel, capable of being planarized and mated to drive electronics.

It is difficult to capture the early signs of a forest fire at night using current visible-spectrum sensor technology. Infrared (IR) light sensors, on the other hand, can detect heat plumes expelled at the initial stages of a forest fire around the clock. Long-wave IR (LWIR) is commonly referred to as the “thermal infrared” region where thermal emissions are captured without the need of, or reflections from, external radiation sources. Mid‑wave IR (MWIR) bands lie between the “thermal infrared” and “reflected infrared” (i.e. short-wave IR) regions. Both LWIR and MWIR spectral regions are able to detect thermal radiation; however, they differ significantly in regards to their detection sensitivity of forest-fire heat plumes. Fires fueled by organic material (i.e. wood, leaves, etc.) primarily emit hot carbon dioxide (CO2) gas at combustion. Consequently, because CO2 is also present in the atmosphere, re-emission restricts the spectral transmittance and hence spectral radiance over a wide range of frequencies in the MWIR region. Moreover, as the distance between the detector and fire’s heat plume becomes greater, the additional CO2 introduced into the detection path leads to further attenuation of photon emittance. Since these absorption frequencies also lie within the response bandwidth of the MWIR sensor material, captured heat plume radiation manifests itself as a group of “flooded” or saturated pixels that exhibit very little dynamic behavior. Meanwhile, since the LWIR spectral region is not significantly affected by atmospheric gas absorption, its sensor is able to capture the forest fire’s heat plume thermal signature at far range without such complications. By exploiting the underlying spectral differences between LWIR and MWIR regions, this study aims to achieve early forest fire heat plume detection via direct identification of its dynamic characteristics whist concurrent attenuation of detected non-fire-related radiation. A land‑based, co‑located, cooled-LWIR/cooled-MWIR (CLWIR/CMWIR) detector camera is used to capture and normalize synchronized video from which sequential spatial-domain difference frames are generated. Processed frames allow for effective extraction of the heat plume’s “flickering” features, which are characteristic to the early stages of a forest fire. A multilayer perceptron (MLP) neural network classifier is trained with feature points generated from known target samples (i.e. supervised learning). Resulting detection performance is assessed via detection time, error metrics, computation time, and parameter variation. Results indicate that heat plumes expelled at the early stages of a forest fire can be identified with high sensitivity, low false alarm, and at a farther range than commercial detectors.

Advanced technologies for mixed gas detection are discussed. A calorific measurement technique for hydrogen-natural gas mixtures using ultrasonic transducers is examined. Measuring the speed of sound in the gas medium enables an accurate composition testing of mixed gas. At the beginning, different ultrasonic transducers are tested and a suitable one for gas testing is chosen. A jig is designed to conduct the testing with nitrogen/oxygen mixtures in a proof of principle experiment. Another jig is designed and manufactured to test a transit time ultrasonic method for flow rate calculation in order to obtain a full energy flow measurement. A mixed gas leak detection technique based on laser spectroscopy is also studied. A Mid-Wave Infrared (MWIR) laser is implemented to be used as a source in a direct absorption measurement for methane detection. The implemented MWIR laser uses nonlinear optics to generate a MWIR output. A novel intracavity structure using periodically poled lithium niobate as the nonlinear crystal is implemented, and the highest blackbox efficiency for continuous wave difference frequency generation in the MWIR region is reported, to the best of our knowledge. Currently the output power is around 8.1 mW at 3.5 μm with a 1.058% W-1 blackbox efficiency. Watt level MWIR generation is expected using an optimized setup. At last, a second laser source that operates in the long-wave infrared (LWIR) region was also studied. The discussed laser setup for LWIR generation is similar to the MWIR one with different pump and signal wavelengths and an orientation patterned gallium phosphide (OP-GaP) as the nonlinear crystal. Due to the absorption loss of GaP at the pump wavelength, only mW power level is expected out of the intracavity structure. Some alternative approaches for LWIR generation are discussed. / Thesis / Master of Applied Science (MASc)

Every year wildfires threaten or destroy ecological habitats, man-made infrastructure and people’s lives. Additionally millions of dollars are spent each year trying to prevent and control these fires. Ideally if a wildfire can be detected before it rages out of control it can be extinguished and avoid large scale devastation. Traditional manned fire lookout towers are neither cost effective nor particularly efficient at detecting wildfire. It is proposed that temporal filtering can be used to isolate the signals created at the beginnings of potential wildfires. Temporal filtering can remove any background image and any periodic signals created by the camera movement. Once typical signals are analyzed, digital filters can be designed to pass fire signals while blocking the unwanted signals. The temporal filter passes only fire signals and signals generated by moving objects. These objects can be distinguished from each other by analyzing the objects mid and long wave energy profile. This algorithm is tested on 17 data sources and its results analyzed.

No description available.