LiDAR (Light Detection and Ranging) is thought to be one of the necessary sensors for automatic driving systems and advanced driver assistance systems. Recently, the LiDAR of the automotive vehicle is installed in the grille or near the headlights. These installed positions are very weak for a variety of pollutions. One of the measures to keep the LiDAR window surface clean is the use of anti-fingerprint coating. In this study, the hybrid optical coating for automotive LiDAR window (BK7 glass) which have the multifunction of UV-VIS absorption, NIR transmission, mechanical hardness and easy cleanability was developed. The surface hardness of the whole front coating and performance of anti-fingerprint coating were measured. The several reliability tests were performed. The coated window passed all tests.
For chalcogenide-based infrared glass materials, the need was emphasized along with the spread of thermal imaging cameras in COVID 19 environment. Commercial Ge-As-Se glass system exhibits a dispersion value of 100~180 and a refractive index of 2.5 or more, and is suitable for the glass molding process, so it is used as an aspherical infrared lens for various thermal imaging cameras. However, some compositions are not suitable for glass molding process. In this study, the composition of the long wavelength infrared glass melting was designed based on the Ge-As-Se system with a Ge composition range of 0~35 at%, As composition range of 20~40 at%, and Se composition range of 25~60 at%. As a result of XRD analysis for each Ge-As-Se-based composition, it was confirmed that all amorphous grains were obtained in the developed composition area. For the Ge-As-Se glass-forming composition region, the glass transition temperature ranged from 180 to 425°C. The refractive index was measured using the prism method in the 3 to 12 μm wavelength band. The refractive index (λ=10 μm) of Ge5As40Se55 and Ge5As35Se60 was 2.6913 and 2.6538, respectively. Moldability test was performed using a glass molding press. As a result of observing whether the lens has internal defects and microcracks after molding, it was confirmed that there was no abnormality and that it was suitable for glass molding process.
The sealing method using a laser has been widely used since laser beams supplied locally the necessary energy to allow the formation of a hermetic bonding. The most common sealing techniques using a glass frit and a screen printer have some problems such as pores, non-uniform height, imperfect hermetic sealing. To reach high quality of laser sealing, the difference of coefficient thermal expansion (CTE) between the laser sealing glass and glass substrate should be lower than 1.0×10-6/K. In order to prove the feasibility of novel laser sealing glass as a fiber type sealant, PbO-SiO2-Al2O3-B2O3 based glass system was drawn with fiber types ranging from 180 μm to 1000 μm in diameter. CuO and Na2CO3 were added into PbO-SiO2-Al2O3-B2O3 glass system in order to tuning the CTE. The thermo mechanical and thermal properties were investigated for correlations the CuO and Na2CO3 concentrations with PbO-SiO2-Al2O3-B2O3 glass system. The 1wt% CuO and 1wt% Na2CO3 co-doped PbO-SiO2-Al2O3-B2O3 glass system shows the CTE of 9.53×10-6/K. In this study, the FTO-coated glass substrate with a CTE of 10.23×10-6/K was sealed with fiber type sealant made of the CuO and Na2CO3 co-doped PbO-SiO2-Al2O3-B2O3 glass system. These results indicate that the fiber type sealant is feasible as laser sealing material in the packaging industry.
A diamond-like carbon thin film was deposited on the outer face of the germanium (Ge) window to protect the infrared lenses from a harsh environment in automotive application. Infrared transmittance and residual stress of a tetrahedral amorphous carbon (ta-C) thin film by a filtered cathodic vacuum arc (FCVA) source were investigated to increase the lifetime of a Ge window. They were found to have a trade-off relation about the change of the substrate pulse voltage. By introducing methane gas in FCVA deposition process, a hydrogenated ta-C (ta-C:H) thin film of which both IR transmittance and residual stress was improved could be obtained. A Ge window coated with ta-C:H thin film with 1.43 μm thickness showed anti-reflective effect in long-wave infrared. The hardness of ta-C:H thin film on Ge window was higher than 30 GPa. Adhesion, severe abrasion, temperature, humidity and salt solubility tests were carried out in accordance with MIL-C-48497A.
We demonstrated the ion-sensitive field-effect transistors (IS-FETs) based on nanowires (NWs) with different diameters and doping concentrations to obtain the high sensitivity and various applications. The growth of the catalyst-free InAs NWs was carried out using a horizontal reactor MOCVD system (AIXTRON Inc.). A p-type Si (111) wafer (ρ = 1 -10 Ω-cm) was prepared for the NW growth. Here, NWs with diameters of around 50 ~ 150 nm were grown and the doping concentration also was changed around x±1016~18 /cm2. IS-FETs with the grown InAs NWs were fabricated using the photolithography and the lift-off process. The gas sensing characteristics have been investigated through studying the gate response of the NW conductance in different ambient conditions.
We analyzed and demonstrated the double layered metallic nano-structures using polystyrene lift-off process on the
conventional surface plasmon resonance (SPR) sensor to enhance the sensitivity of an SPR surface. The double layered
plasmonic structures are optimized using the three-dimensional finite-difference time-domain method for the width,
thickness, and period of the polystyrene beads. The thickness of the metal film and the metallic nano-hole is 20 and 20
nm in the 305 nm wide nano-hole size, respectively. The double layered metallic nano-structures are fabricated with
monolayer polystyrene beads of chloromethyl latex 4% w/v 0.4 μm. The sensitivities of the conventional SPR sensor
and the double layered plasmonic sensor are obtained to 42.2 and 60 degree/RIU, respectively. The SPR devices are also
applied to the lead ion sensor. The resonance shifts of SPR sensors with and without a poly(vinyl chloride) membrane
are 1328 RU and 788 RU from 10-5 M to 10-2 M concentration, respectively.
Dye-Sensitized solar cell (DSSC) is expected to be one of the next-generation photovoltaics because of its environment-friendly and low-cost properties. However, commercialization of DSSC is difficult because of the electrolyte leakage. We propose a new thermal curable base on silicon resin. The resin aimed at sealing of DSSC and gives a promising resolution for sealing of practical DSSC. Furthermore, the optimized resin was fabricated into solar cells, which exhibited best durability by retaining 97% of the initial photoelectric conversion efficiency after 1,000 hours tracking test at 80℃.
We proposed and demonstrated the metallic nano-ring structure using polystyrene lift-off process to enhance the
sensitivity of an SPR surface. The double layered SPR structures are optimized using the finite-difference time-domain
method for the width, thickness, and period of the polystyrene beads. The optimum thickness of the metal film and the
metallic nano-ring is 30 and 20 nm in the 214 nm wide nano-hole size, respectively. The metallic nano-ring structures
are fabricated with monolayer polystyrene beads of 400 nm wide. The various metallic nano-ring structures have been
obtained by transferring method. The sensitivities of the conventional SPR sensor and the metallic nano-ring structures
are obtained to 42.2 and 52.1 degree/RIU, respectively.
In this works, we have demonstrated a VOA integrated with mPDs, based on silica-on-silicon PLC and flip-chip bonding technologies. The suspended ridge structure was applied to reduce the power consumption. It achieves the attenuation of 30dB in open loop operation with the power consumption of below 30W. We have applied two-step flipchip bonding method using passive alignment to perform high density multi-chip integration on a VOA with eutectic AuSn solder bumps. The average bonding strength of the two-step flip-chip bonding method was about 90gf.
In this study, we proposed and fabricated optical sensor module integrated onto optical-electrical printed circuit board (PCB) for gas detection based on polymer waveguide with tin oxide thin film. Their potential application as gas sensors are confirmed through computational simulation using the two dimensional finite-difference time-domain method (2DFDTD). Optical-electrical PCB was integrated into vertical cavity surface emitting laser (VCSEL), photodiode and polymeric sensing device was fabricated by the nano-imprint lithography technique. SnO2 thin film of 100nm thickness was placed on the surface of core layer exposed by removing the specific area of the upper cladding layer of 300 μm length and 50 μm width. The performance of the device was measured experimentally. Initial study on the sensor performance for carbon monoxide gas detection indicated good sensitivity.
Typical Dye-sensitized solar cells (DSSC) are composed of mesoporous TiO2 nanocrystals electrode on transparent fluorine-doped tin oxide (FTO) substrate, sensitizers on the TiO2 nanocrystals, platinum (Pt) on the FTO substrate as a counter-electrode, and iodine/iodide electrolytes between the two transparent conducting oxide (TCO) substrate. But two transparent conductive oxide(TCO) substrates are estimated to be about 60[%] of the total cost of the DSSCs. Currently novel TCO-less structures have been investigated in order to reduce the cost. We suggested a TCO-less DSSCs which has titanium layer electrodes. Titanium layer electrodes are formed by electron-beam evaporation method. And we proposed the formation of hole for injecting the electrolyte of DSSC by using lithographic method. The sizes of holes are 4um and the intervals of holes are 2um. Finally, we prepared the 0.45 cm2 DSSC device and analytical instruments such as electrochemical impedance spectroscopy, scanning electron microscope were used to evaluate the TCO-less DSSCs.
In this works, the piezoelectric devices of ZnO nano-rods were fabricated for piezoelectric sensor. The ZnO nano-rods were grown by hydrothermal synthesis through two-dimensional nano-patterns using a laser interference lithography. ZnO nano-rods were preferred orientation with c-axis and wurtzite structure. It was found that the electricity of nano-rod piezoelectric device was 8x10-7 Wh under the load of 0.8kgf. The piezoelectric behaviors are attributed to the direct compression of ZnO nano-rods by an external force. Therefore, the piezoelectric devices of ZnO nano-rods fabricated by hydrothermal methods were applicable to the pressure sensors.
We introduce an ultra-sensitive integrated photonic sensor structure using silicon on insulator based triangular resonator, in which a surface plasmon resonance (SPR) gold film is applied on a total internal reflection mirror. We have analyzed and optimized the triangular resonator sensor structure with an extremely small SPR mirror sensing area. Due to the large phase shift in the SPR mirror, a significantly enhanced sensitivity of 800 nm/RIU (refractive index unit) and the maximum peak shift of half free spectral range have been obtained at the SPR angle of 22.65° with Au thickness of 35 nm for the change of the refractive index Δn = 1x10-3.
Two different shaped ZnO nanorods were grown on ZnO buffered Al2O3 substrate by laser interference lithography and hydrothermal method. The light waveguide within ZnO nano rod and photonic crystal effects in arrayed ZnO nanorods was calculated by 3D-finite dimension time domain(3D-FDTD) programs. The ZnO photonic crystal effect and number of modes of ZnO nanorod was governed by arrangement and shape of ZnO nanorod, respectively.
Organic Light Emitting Device (OLED) has a characteristic to change the electric energy into the light when the electric field is applied to the organic material. OLED is currently employed as a light source for the lighting tools because research has extensively progressed in the improvement of luminance, efficiency, and life time. OLED is widely used in the plate display device because of a simple manufacture process and high emitting efficiency. But most of OLED lighting projects were used the vacuum evaporator (thermal evaporator) with low molecular. Although printing method has lower efficiency and life time of OLED than vacuum evaporator method, projects of printing OLED actively
are progressed because was possible to combine with flexible substrate and printing technology. Printing technology is ink-jet, screen printing and slot coating. This printing method allows for low cost and mass production techniques and large substrates. In this research, we have proposed inkjet printing for organic light-emitting devices has the dominant method of thick film deposition because of its low cost and simple processing. In this research, the fabrication of the passive matrix OLED is achieved by inkjet printing, using a polymer phosphorescent ink. We are measured optical and electrical characteristics of OLED.
In this paper, we have demonstrated a metallic nano-structured SPR sensor for an improvement of biosensing
sensitivity using a metallic nano-structure. Permittivity of metal is calculated with Drude model for analysis. The
sensitivity of SPR sensor with metallic nano-structure is 65 degree/RIU, and that of conventional SPR configuration is
54.8 degree/RIU. We have fabricated the random metallic nano-structures on the metallic thin film using the RIE etching
process. Moreover, we have analyzed the structure using the finite-difference time-domain method for the exact
characteristic.
We investigate the modulation properties of a three-guide coupled rectangular ring laser having bidirectional lasing
characteristics. Two different rectangular lasers having active section lengths of 250 and 350 μm and total cavity lengths
of 580 and 780 μm are fabricated. The rectangular laser cavity consists of four low loss total internal reflection mirrors
and an output coupler made out of three passive coupled waveguides. For both the clockwise and counterclockwise
circulating directions, the lasing threshold currents of around 38 mA are obtained at room temperature under continuous
wave operation. A 3-dB modulation bandwidth over 3 GHz is observed in both circulating directions for two different
lasers.
We investigated the properties of a triangular microresonator using the total internal reflection (TIR) mirrors with a
long evanescent field around the critical angle. For the sensitivity analysis, we have calculated the mirror offset due to
the Goos-Hänchen effect and the resonance shift of the triangular resonator with the refractive index change of the outer
region in the TIR mirror. The mirror offset is increased up to 0.8 μm for the transverse electric (TE) polarization and
2.0 μm for the transverse magnetic (TM) polarization to the incident angle of 18°. Then, the resonance shift of 417 pm
for the TM polarized light and 34 pm for the TE polarized light were observed, respectively, by changing the refractive
index of 4×10-5. The measured extinction ratio of triangular ring resonator was about 6 dB near 1550 nm, in where the
incidence angle of the TIR mirror inside the resonator was 18°.
We proposed the photonic crystal coupled surface plasmon resonance sensors using gold nano-structure to enhance the
sensitivity of an SPR sensor. The proposed configuration with the photonic crystal structure is Au(Photonic
crystal)/Au/Ag/Cr/Glass. The 20 nm silver film and the 20 nm gold film are layered on the glass substrate. Then, the
dot-like gold photonic crystal structures with a period pitch are patterned on the Au/Ag/Cr/Glass structure. The
reflectance and the optical-mode propagations as a function of incident angle are calculated using the three-dimensional
finite-difference time-domain method. Under this resonance condition, the incident light is highly absorbed and loses a
fair amount of its energy, which results in a dip in the intensity profile of the reflected light. The optimum resonance
angle of 44.5 degrees is obtained in the 75-nm-radius Au photonics crystal structure with a period of 300 nm.
We have proposed a novel encapsulation method with simple process in comparison with conventional encapsulation
technique. Here, the encapsulation film of silicon dioxide is steady for external environment because this can be
designed to cover the emitting organic material from air. Silicon dioxide of 220 nm was deposited by plasma enhanced
chemical vapor deposition and etched by reactive ion etching system. Then, Alq3 was used as a material to emitting layer
in the green (organic light emitting device) OLED and TPD in the hole transportation layer was used for the harmonious
transportation of hole. Luminance was measured with 40 hour intervals at the air-exposed condition. After 400, 1,000,
1,600, and 2,000 hours, luminance of green OLED were 7,366, 7,200, 6,210, and 5,100 cd/m2, respectively. Luminance
of green OLED doesn't decrease until 2,000 hours. As a results, proposed encapsulation technique can increase the life
time of green OLED.
We studied the energy states in In0.8Ga0.2As SAQDs (self-assembled quantum dots) which depended on W(001) and
the misorientation angle of the substrate. Starting materials used in this study were SiO2-patterend exact and 5 degree -
off (001) GaAs substrates. In0.8Ga0.2As SAQDs had only ground state emissions for SiO2-patterned exact (001) GaAs
substrate, whereas those had ground and excited state emissions for SiO2-patterned 5 degree-off (001) GaAs substrate.
These results suggest that discrete nature of the density of states in SAQDs was improved by using SiO2-patterned
vicinal (001) GaAs substrate with higher misorientation angle of substrate.
Titanium dioxide (TiO2) thin films were prepared by ion-assisted electron-beam deposition on glass at room
temperature and were annealed by rapid thermal annealing in O2 and N2 gas flow. TiO2 thin films annealed in N2 gas
flow are (110) rutile phase and (101) anatase phase, but in O2 gas flow are (110) rutile phase. The optical band gaps of
the TiO2 thin films are increased to 3.281 eV with annealing treatment of 300 ~ 500 °C in O2 gas flow and to 3.271 eV in
N2 gas flow. However, the band gap begins to decrease to 3.277 eV at the annealing temperature of 600 °C in O2 gas
flow and to 3.257 eV in N2 gas flow, respectively.
We proposed the grating coupled surface plasmon resonance (GC-SPR) sensors using ZnO and metallic nanograting
structures to enhance the sensitivity of an SPR sensor. The GC-SPR sensors were analyzed using the finitedifference
time-domain method. The optimum resonance angles of 49 and 55.5 degrees are obtained in the 150 nm wide
grating structure with a period of 300 nm for the ZnO thickness of 30 and 50 nm, respectively. Here, an enhanced
evanescent field is obtained due to the surface plasmon on the edge of the bandgap when the ZnO and metallic grating
structures are used to excite the surface plasmon.
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