Μm Waveband Research Articles

Graphene-Induced Nonlinear Four-Wave-Mixing and Its Application to Multiwavelength Q-Switched Rare-Earth-Doped Fiber Lasers

We experimentally confirm that graphene within fiber laser cavities can generate four-wave-mixing (FWM) by observing the laser spectral broadening and the transition from the single-longitudinal-mode oscillation to multiple-longitudinal-mode one. Then, by simultaneously exploiting the graphene-induced nonlinear FWM and its super-broadband saturable absorption, we further achieve for the first time to the best of our knowledge, multiwavelength Q-switched Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> - or Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fiber lasers at 1 μm and 1.5 μm wavebands, respectively. Simultaneous 23-wavelength Q-switching oscillation with a wavelength spacing of 0.2 nm is stably generated at 1.5 μm waveband. The multiwavelength Q-switched pulses have the minimum pulse duration of 2.5 μs, the maximum pulse energy of 72.5 nJ and a wide range of pulse-repetition-rate (PRR) from 2.8 to 63.0 kHz. At 1 μm waveband, we also obtain five-wavelength simultaneous lasing in Q-switching regime with the pulse duration of ~ 3 μs, pulse energy of 10.3 nJ and PRR between 39.8 and 56.2 kHz.

Synthesis and Infrared Emisstivity Properties of CdS/ZnS/Al Composite Material with Microemulsions

CdS/ZnS core-shell structure was synthesized with reverse microemulsions in the system of cetyl trimethyl ammonium bromide (CTAB)/ C5H12O/ C6H14/H2O and precipitator mixed thioacetamide (TAA )and ethylenediamine (EDA), which was coated on the surface of Al particles. The characteristics of the composite particles were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM )and Fourier transform infrared (FTIR). Emissivity of composite material in 8~14 µm waveband was 0.2574. The results showed composite material had lower infrared emissivity when PH value was between10 and 11, mol ratio of Zn/Cd was 0.3, and the reaction temperature was 70°C.

A robust convection cover material for selective radiative cooling applications

The enhanced cooling of exposed surfaces by radiative heat loss to the cold sky was investigated using a variety of commonly available materials. Zinc sulphide was identified as a durable substance suitable for the construction of convection covers for radiative cooling radiators. With respect to polyethylene, the most commonly used convection cover to date, the new material is mechanically stronger, impervious to damage by solar ultraviolet and in practical thicknesses is more transparent in the 8–14 μm waveband. Use of this window material with a previously proposed selective radiator material, a form of anodised aluminium that reflects radiation at wavelengths shorter than 8 μm allows for the economical production of an effective selective radiator system. Measurements were made on simple radiator plates and convection covers.

Infrared emissivity of Sr doped lanthanum manganites in coating form

The Sr doped lanthanum manganite coatings were prepared using La 0.8Sr 0.2MnO 3 particles and epoxy modified polyurethane as pigment and resin matrix, respectively. The structure, morphology, surface roughness and infrared normal emissivity ( ɛ N ) in the 3–5 and 8–14 μm wavebands of the samples were systematically investigated. With the increase of La 0.8Sr 0.2MnO 3 pigment, the ɛ N of the coatings decreases and the ɛ N values in the 8–14 μm waveband are higher than those in the 3–5 μm waveband. The surface roughness has no significant effect on the infrared emissivity of LSMO coatings. For 50% LSMO coating, the sample shows variable-emissivity property in the 8–14 μm waveband and the emissivity property remains unchanged before and after ultraviolet irradiation.

The preparation and properties of Y 2O 3/AlN anti-reflection films on chemical vapor deposition diamond

Yttrium oxide (Y 2O 3) films have successfully been applied as anti-reflection (AR) and anti-oxidation films for diamond. For significant adhesion improvement between Y 2O 3 coating and diamond, aluminum nitride (AlN) as an interlayer is introduced. Y 2O 3 and AlN films were prepared by RF magnetron sputtering of Y 2O 3 ceramic target in Ar atmosphere and pure Al metal target in Ar + N 2 atmosphere, respectively. The Y 2O 3 and AlN films were studied by X-ray diffraction, X-ray photoelectron spectroscopy, Atomic force microscopy and Spectroscopic ellipsometry. Adherent Y 2O 3/AlN films on high optical quality chemical vapor deposition diamond with optimum thicknesses for infrared transmission enhancement in 8–10 μm were obtained by a Fourier transform infrared spectrometer. More than 28% increase in maximum transmission was observed for Y 2O 3/AlN//Diamond//AlN/Y 2O 3. Comparing between the designed and experimental AR effects for Y 2O 3/AlN film in 8–10 μm wavebands, experimental average AR effects are smaller for the absorption and scattering loss. AR effects for the Y 2O 3/AlN films on CVD diamond are proved to be excellent.

Optical design of a compact long-range thermal imaging camera in the 3–5 μm wave band

In this work, the design study of a fixed focus thermal imaging system for 3–5 µm using infrared focal plane array is presented. The system is designed to have possible minimum weight and length in order to achieve the best operational characteristics. The system is designed as an objective relay combination to have 100% cold shield efficiency. In this way, the objective and relay are designed as short as possible. The objective is designed as a Schmidth–Cassegrain type mirror and the relay is a triplet type with one lens far from the others to guarantee the minimum distance to the intermediate image.

Influence of RE/Mn (RE= La, Nd and Gd) Ratios on the Infrared Absorption and Emission Properties of Co-Zn Ferrites

The RE/Mn co-doped Co-Zn ferrites were prepared by the ceramic method. Infrared absorption and emission properties were obtained by investigating those ferrites. The IR spectra in the range from 400 to 1200 cm-1 were observed. Mainly, three bands were investigated. The high-frequency bands and low-frequency bands were assigned to the tetrahedral and octahedral complexes, respectively. The intensity of all the bands is found to increase while a decrease in broadness, which is explained on the cation distribution in the tetrahedral and octahedral sites were modified by RE/Mn addition. The Mn substitutes the Fe3+ and enters into the octahedral sites; while the partial RE3+ ions are apt to diffuse to the grain boundaries and others enter into the spinel lattice .This can be explained on the basis of ionic radii and ratios of the substituted cation. The results indicate that IR emissivity seems to be increasing with RE/Mn ratio within 8-14 μm wavebands. The maximum infrared emissivity is 0.968 when La/Mn ratio of 0.20 within 8-14 μm wavebands.

Design, Preparation and Application of Dual-Color HgCdTe Infrared Sensor

In the paper, the principle, the preparation and the performance of the dual-color infrared HgCdTe detector is introduced. The detector is a combination of different wave band filter and different respond wave band element. The application of the dual-color infrared HgCdTe sensitive element for methane gas detection sensor is developed. A two-element HgCdTe methane detector which responds between 3.13~3.53μm and 3.91~4.09μm wave bands respectively was reported. The performance of each detection channel was presented. The experiment test and analyze are fulfilled. The experiment result indicates that under the refrigeration temperature the dual-color HgCdTe detector not only has a favorable response ability and repetition but also can realize the response and distinguish ability to methane gas through integrate narrow band filter on the front of the detector sensitive element.

Brightness map of the zodiacal emission from the AKARI IRC All-Sky Survey

The first Japanese infrared space mission AKARI successfully scanned the whole sky with its two main instruments, the Infrared Camera (IRC) and the Far-Infrared Surveyor (FIS). The AKARI All-Sky Survey provides us with an invaluable opportunity to examine the zodiacal emission (ZE) over the entire sky in the leading as well as the trailing direction of the Earth’s motion. We describe our efforts to reduce the ZE brightness map from the AKARI’s survey in the 9 μm waveband. Compared with the interplanetary dust cloud model of Kelsall et al. (1998), the map requires an increase of the contribution of the resonance ring component to the ZE brightness by about 20%. We paid special attention to the north and south ecliptic pole brightnesses. The symmetry plane’s inclination and longitude of ascending node need to be modified from those in Kelsall et al. (1998) to reach a best fit to the observed pole brightness difference.

Microphotoluminescence investigation of InAs quantum dot active region in 1.3 μm vertical cavity surface emitting laser structure

Microphotoluminescence (μ-PL) investigation has been performed at room temperature on InAs quantum dot (QD) vertical cavity surface emitting laser (VCSEL) structure in order to characterize the QD epitaxial structure which was designed for 1.3 μm wave band emission. Actual and precise QD emission spectra including distinct ground state (GS) and excited state (ES) transition peaks are obtained by an edge-excitation and edge-emission (EEEE) μ-PL configuration. Conventional photoluminescence methods for QD-VCSELs structure analysis are compared and discussed, which indicate the EEEE μ-PL is a useful tool to determine the optical features of the QD active region in an as-grown VCSEL structure. Some experimental results have been compared with simulation results obtained with the aid of the plane-wave admittance method. After adjustment of epitaxial growth according to EEEE μ-PL measurement results, QD-VCSEL structure wafer with QD GS transition wavelength of 1300 nm and lasing wavelength of 1301 nm was obtained.

A design study of a triple field of view 8–12 μm waveband airborne FLIR

In this work, a design study of a three field-of-view (FOV) optical system for 8–12 μm imaging using a 288×4 focal plane array detector is presented. The detector pixel size is 25 μm×28 μm. The f/# of the detector is 1.76. In order to switch the FOVs, three different optical configurations are superimposed and all three configurations are optimized. The narrow and medium FOV switching is based on movement of the second negative lens of the afocal system, whereas the wide FOV is selected by inserting a mirror between the 4th and 5th lenses of the afocal system. By inserting a switching mirror, the objective part of the first configuration is blocked out; nevertheless the afocal of the wide FOV is activated. The imager part of the layout is common for all FOVs. Diffractive and aspheric surfaces are utilized to control chromatic and all other kinds of aberrations, reducing the total lens number. The final optical designs, together with their modulation transfer function (MTF) plots, are illustrated, exhibiting excellent performance in all three FOVs. More specifically, the paper emphasizes how the displacement of compensating lenses effect the MTF of the system and how automatic movements of the lenses are used to eliminate the defocusing problem under changing environmental conditions.

Effect of RE/Ni (RE=Sm, Gd, Eu) addition on the infrared emission properties of Co–Zn ferrites with high emissivity

Abstract The RE/Ni doped Co–Zn ferrites were prepared by the ceramic method. X-ray diffraction, infrared absorption, scanning electrical microscopy and emission properties were used to investigate those ferrites. The IR spectra in the range from 400 to 1200 cm−1 were observed. Mainly, two bands were investigated. The band at around 587 cm−1 and the band at around 400 cm−1 were assigned to the tetrahedral and octahedral complexes, respectively. The peak intensity decreases with the increase of RE/Ni ratio. X-ray diffraction analysis confirms the formation of spinel-like structure. Lattice constants decrease slight distortions proportionally to RE/Ni ratio. The X-ray density of doped ferrites was found to be increasing. The grain sizes were estimated from the SEM micrographs. The addition of RE/Ni results in a decrease in grain size. The infrared emissivity for 8–14 μm wave bands seems to be increasing with increasing RE/Ni ratio. The highest infrared emissivity is 0.938 when Gd/Ni ratio is 0.20.

The effect of B site doping on infrared emissivity of lanthanum manganites La 0.8Sr 0.2Mn 1− xB xO 3 (B = Ti or Cu)

The lanthanum manganites La 0.8Sr 0.2Mn 1− x B x O 3 (B = Ti or Cu, 0 ≤ x ≤ 0.4) were prepared by standard solid-state reaction method. The structure, infrared absorption, electron spin resonance (ESR) and infrared normal emissivity ( ɛ N) in the 8–14 μm waveband of the samples were systematically investigated. The samples are perovskite with distorted rhombohedral structure. Compared to x = 0 sample with ɛ N value 0.693, infrared absorption occurred in the 8–14 μm waveband leads to high emissivity value of the B site doping samples ( ɛ Ti = 0.912 and ɛ Cu = 0.894), and the ɛ N decreases slightly with increasing doping level due to decreasing transition probability indicated by ESR results. The ɛ N changes slightly in the temperature range 293–373 K, from 0.9 to 0.882 for Ti doping and from 0.886 to 0.879 for Cu doping, owing to the weakening of the double-exchange interaction between Mn 3+ and Mn 4+.

Simulation and control of narcissus phenomenon using nonsequential ray tracing II Line-scan camera in 7-11 μm waveband

A nonsequential ray tracing technique is used to calculate the narcissus signature in infrared (IR) imaging cameras having cooled detectors operating in the 7-11 microm waveband. Imaging cameras based on a one-dimensional linear detector array with a scan mirror are simulated. Circularly symmetric diffractive phase surfaces commonly used in modern IR cameras are modeled including multiple diffraction orders in the narcissus retroreflection path to correctly estimate the stray light return signal. An optical design example based on a step-zoom dual field of view optical system is discussed along with the performance curves to elaborate the modeling technique. Optical methods to minimize the narcissus return signal are explained, and modeling results presented. The nonsequential ray tracing technique is found to be an effective method to accurately calculate the narcissus return signal in complex IR cameras having diffractive surfaces.

Polarization-maintaining photonic crystal fibers with near-zero flattened dispersion in 1.06 μm waveband for medical applications

In this paper we present the design of a modified hexagonal photonic crystal fiber (PCF) having high birefringence and a near-zero flattened dispersion. Using the finite-difference method (FDM), it is shown that the proposed multiple Gedoped core hexagonal PCF exhibits a high birefringence of order 10−3 and a nearly zero flattened dispersion in the optical coherence tomography (OCT) waveband. In addition, the proposed PCF has a confinement loss of less than 10−8 dB/m at 1.06 μm. PCFs with such properties are considered suitable for both endoscopic OCT and other experimental setups employing 1.06 μm lasers.

Simulation and control of narcissus phenomenon using nonsequential ray tracing I Staring camera in 3-5 μm waveband

A nonsequential ray tracing technique is used to simulate the narcissus phenomenon in infrared (IR) imaging cameras having cooled detectors. Imaging cameras based on two-dimensional focal plane array detectors are simulated. In a companion article, line-scan imaging cameras based on one-dimensional linear detector arrays are simulated. Diffractive phase surfaces commonly used in modern IR cameras are modeled including multiple diffraction orders in the narcissus retroreflection path to correctly simulate the stray light return signal. Practical optical design examples along with their performance curves are given to elucidate the modeling technique. Optical methods to minimize the narcissus return signal are thoroughly explained, and modeling results are presented. It is shown that the nonsequential ray tracing technique is an effective method to accurately calculate the narcissus return signal in complex IR cameras having diffractive surfaces.

OBJECT RECOGNITION USING MWIR THERMOGRAPHY WITH VARYING EMISSIVITY AND TEMPERATURE LEVELS

An infrared (IR) camera is one of the common tools for taking images for thermography analysis in the medical field. In this paper, object recognition using infrared images captured with a Middle Wave Infrared (MWIR) camera is studied. By using the InSb detector, the MWIR system used in this study operates in the 3−5 μm waveband, and it is suited for high-end research and development applications. To enhance the use of MWIR thermography in real-world applications, it is important to devise reliable image generation and processing techniques for MWIR images. An experimental study has been conducted to identify the capability of MWIR thermography in distinguishing an object (a human hand) from its background with varying emissivity and temperature levels. It was observed that object recognition becomes difficult when the emissivity difference is within 0.01 under the temperature condition of within 1°C for the object and the background.

Structure, Infrared Radiation Properties and Mössbauer Spectroscopic Investigations of Co 0.6Zn 0.4Ni xFe 2- xO 4 Ceramics

Ferrite compound Co 0.6 Zn 0.4 Ni x Fe 2- x O 4 was synthesized by solid state reaction. The structure and performance of Co 0.6 Zn 0.4 Ni x Fe 2- x O 4 compounds were studied by Mossbauer spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared radiant tester. Mossbauer spectroscopy and XPS analysis show the valence states and distribution of cations in Co 0.6 Zn 0.4 Ni x Fe 2- x O 4 . Zn 2+ has invariably shown preference for the tetrahedral sites, and Ni 2+ has the preference for the octahedral sites. The occupancy of Fe 3+ linearly increases on the tetrahedral sites, and sharply decreases on the octahedral sites with increasing x , owing to its gradual replacement by Ni 2+ on the octahedral sites. It indicates that due to the occupation of octahedral sites by the majority of Ni 2+ , Fe 3+ decreasingly migrated from the octahedral sites to the tetrahedral sites and substituted Co 3+ sites, which made the number of Co 3+ in the tetrahedral sites decreasing. According to the measurement results of XRD and the infrared radiant tester analysis, the lattice parameter and infrared radiance have shown a nonlinear variation, exhibiting the infrared average radiance of 0.92 in the 8-14 μm waveband, and the results demonstrate that these Co-Zn-Ni spinel ferrites have potential for application in a wide range of infrared heating and drying materials.

An experimental study on object recognition and enhancement in MWIR thermography

An infrared (IR) camera is one of the common tools for taking images for thermography analysis in the medical field. In this paper, object recognition using infrared images captured with a middle wave infrared (MWIR) camera is studied. By using the InSb detector, the MWIR system used in this study operates in the 3-5 μm waveband, and it is well-suited for highend research and development applications. To enhance the applicability of MWIR thermography to medical-related problems, it is important to devise reliable recognition and enhancement techniques for MWIR images. In this work, an experimental study is conducted to identify the capability of MWIR thermography in distinguishing an object (a human hand) from its background with varying emissivity and temperature levels. It is observed that object recognition becomes difficult when the emissivity difference is within 0.01 under the temperature condition of within 1°C for the object and the background. In addition, a histogram equalisation approach is utilised to enhance blurry images from the MWIR system. The results demonstrate the histogram equalisation method is able to expand the dynamic range expansion of image grey levels so that the output image becomes clear and visible for object recognition.

Quantum-dot external-cavity passively modelocked laser with high peak power and pulse energy

An InAs quantum-dot external-cavity passively modelocked laser with an operation wavelength of 1.27 µm is demonstrated, based on a two-section quantum-dot superluminescent diode with bending ridge waveguide and a 96% output coupler. Stable modelocking with an average power up to 60 mW was obtained at a repetition frequency of 2.4 GHz. This performance corresponds to a 25 pJ pulse energy obtained directly from the oscillator, which represents a 55-fold increase in pulse energy when compared to the current state-of-the-art for semiconductor lasers. At a repetition frequency of 1.14 GHz, picosecond optical pulses with 1.5 W peak power are also demonstrated, representing the highest peak power achieved from an external-cavity laser at the 1.3 µm waveband, without the use of any pulse compression or optical amplification.