The optimization of experimental design prior to deployment, not only for cost effective solution but also for computationally efficient image reconstruction has taken up for this study. We implemented the iterative method also known as... more
The optimization of experimental design prior to deployment, not only for cost effective solution but also for computationally efficient image reconstruction has taken up for this study. We implemented the iterative method also known as effective independence (EFI) method for optimization of source/detector pair configuration. The notion behind for adaptive selection of minimally correlated measurements was to evaluate the information content passed by each measurement for estimation of unknown parameter. The EFI method actually ranks measurements according to their contribution to the linear independence of unknown parameter basis. Typically, to improve the solvability of ill conditioned system, regularization parameter is added, which may affect the source/detector selection configuration. We show that the source/detector pairs selected by EFI method were least prone to vary with sub optimal regularization value. Moreover, through series of simulation studies we also confirmed that sparse source/detector pair measurements selected by EFI method offered similar results in comparison with the dense measurement configuration for unknown parameters qualitatively as well as quantitatively. Additionally, EFI method also allow us to incorporate the prior knowledge, extracted in multimodality imaging cases, to design source/detector configuration sensitive to specific region of interest. The source/detector ranking method was further analyzed to derive the automatic cut off number for iterative scheme.
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ABSTRACT This paper introduces complementary metal-oxide semiconductor (CMOS) active pixel sensor (APS)-based X-ray imaging detectors with high spatial resolution for medical imaging application. In this study, our proposed X-ray CMOS... more
ABSTRACT This paper introduces complementary metal-oxide semiconductor (CMOS) active pixel sensor (APS)-based X-ray imaging detectors with high spatial resolution for medical imaging application. In this study, our proposed X-ray CMOS imaging sensor has been fabricated by using a 0.35 µm 1 Poly 4 Metal CMOS process. The pixel size is 100 µm×100 µm and the pixel array format is 24×96 pixels, which provide a field-of-view (FOV) of 9.6 mm×2.4 mm. The 14.3-bit extend counting analog-to digital converter (ADC) with built-in binning mode was used to reduce the area and simultaneously improve the image resolution. Both thallium-doped CsI (CsI:Tl) and Gd2O2S:Tb scintillator screens were used as converters for incident X-rays to visible light photons. The optical property and X-ray imaging characterization such as X-ray to light response as a function of incident X-ray exposure dose, spatial resolution and X-ray images of objects were measured under different X-ray energy conditions. The measured results suggest that our developed CMOS-based X-ray imaging detector has the potential for fluoroscopic imaging and cone-beam computed tomography (CBCT) imaging applications.
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Abstract We introduce polycrystalline cadmium telluride (CdTe) with high atomic number and density, low effective energy and wide band gap for application in large area diagnostic X-ray digital imaging. In this work, polycrystalline CdTe... more
Abstract We introduce polycrystalline cadmium telluride (CdTe) with high atomic number and density, low effective energy and wide band gap for application in large area diagnostic X-ray digital imaging. In this work, polycrystalline CdTe films were fabricated on ITO/glass substrate by both physical vapor deposition (PVD) with slow deposition rate and pressure of 10−6 Torr and the closed space sublimation (CSS) method with high deposition rate and low vacuum pressure(10−2 Torr). The various polycrystalline CdTe films were grown at different deposition rates and substrate temperatures. Physical properties such as microstructures and the crystal structure of the polycrystalline samples were investigated by SEM and XRD patterns respectively. The PVD method resulted in microstructures with columnar shape and more uniform surface, while the CSS method produced microstructures with many larger grains and less uniform surface. The films were polycrystalline structures with a preferential (111) direction. The electrical and optical properties such as the dark current as a function of applied bias voltage and X-ray sensitivity of the fabricated films were measured and investigated under X-ray exposure.
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This paper presents a low-cost bidirectional (BiDi) wavelength-division-multiplexed passive optical network (WDM-PON) employing colorless uncooled BiDi transceivers (TRxs) and superluminescent diode (SLD)-based broadband light sources... more
This paper presents a low-cost bidirectional (BiDi) wavelength-division-multiplexed passive optical network (WDM-PON) employing colorless uncooled BiDi transceivers (TRxs) and superluminescent diode (SLD)-based broadband light sources (BLSs). The C band is allocated for upstream and the E+ band for downstream in consideration of BiDi packaging, SLD development, and wavelength alignment of dual-window arrayed waveguide gratings (AWGs). The BiDi TRx integrates an
Research Interests: Engineering, Physics, Materials Science, Optics, Laser, and 12 moreOptical Communication, Optoelectronics, Thin Film, Amplified spontaneous emission, Optical physics, Wavelength, Wavelength Division Multiplexing, Fabry Perot, Electrical And Electronic Engineering, Arrayed Waveguide Grating, Laser Diode, and Form Factor
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A diode-pumped Yb:Y2O3 ceramic thin-rod amplifier which operates in the femtosecond regime is studied here. In a single-stage and direct four-pass amplification scheme, the amplifier delivers maximum output power of 8.1 W at a center... more
A diode-pumped Yb:Y2O3 ceramic thin-rod amplifier which operates in the femtosecond regime is studied here. In a single-stage and direct four-pass amplification scheme, the amplifier delivers maximum output power of 8.1 W at a center wavelength of 1030.5 nm and spectral bandwidth of 4.8 nm. Assume a sech2-shaped pulse, a pulse duration of 239 fs is measured, exhibiting a time-bandwidth product value of 0.324. To the best of our knowledge, our Yb:Y2O3 ceramic thin-rod femtosecond amplifier exhibits the shortest pulse duration with Watt-level output power among all Yb:Y2O3-based femtosecond amplifiers.
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The optimization of experimental design prior to deployment, not only for cost effective solution but also for computationally efficient image reconstruction has taken up for this study. We implemented the iterative method also known as... more
The optimization of experimental design prior to deployment, not only for cost effective solution but also for computationally efficient image reconstruction has taken up for this study. We implemented the iterative method also known as effective independence (EFI) method for optimization of source/detector pair configuration. The notion behind for adaptive selection of minimally correlated measurements was to evaluate the information content passed by each measurement for estimation of unknown parameter. The EFI method actually ranks measurements according to their contribution to the linear independence of unknown parameter basis. Typically, to improve the solvability of ill conditioned system, regularization parameter is added, which may affect the source/detector selection configuration. We show that the source/detector pairs selected by EFI method were least prone to vary with sub optimal regularization value. Moreover, through series of simulation studies we also confirmed that sparse source/detector pair measurements selected by EFI method offered similar results in comparison with the dense measurement configuration for unknown parameters qualitatively as well as quantitatively. Additionally, EFI method also allow us to incorporate the prior knowledge, extracted in multimodality imaging cases, to design source/detector configuration sensitive to specific region of interest. The source/detector ranking method was further analyzed to derive the automatic cut off number for iterative scheme.
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Abstract: We present a low-cost C/S-band WDM-PON employing colorless uncooled bidirectional transceivers and SOA-based broadband light sources. Colorless operations over 32 DWDM channels are demonstrated from -20 to 80 °C in 155-Mb/s... more
Abstract: We present a low-cost C/S-band WDM-PON employing colorless uncooled bidirectional transceivers and SOA-based broadband light sources. Colorless operations over 32 DWDM channels are demonstrated from -20 to 80 °C in 155-Mb/s bidirectional transmissions ...
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ABSTRACT This paper introduces complementary metal-oxide semiconductor (CMOS) active pixel sensor (APS)-based X-ray imaging detectors with high spatial resolution for medical imaging application. In this study, our proposed X-ray CMOS... more
ABSTRACT This paper introduces complementary metal-oxide semiconductor (CMOS) active pixel sensor (APS)-based X-ray imaging detectors with high spatial resolution for medical imaging application. In this study, our proposed X-ray CMOS imaging sensor has been fabricated by using a 0.35 µm 1 Poly 4 Metal CMOS process. The pixel size is 100 µm×100 µm and the pixel array format is 24×96 pixels, which provide a field-of-view (FOV) of 9.6 mm×2.4 mm. The 14.3-bit extend counting analog-to digital converter (ADC) with built-in binning mode was used to reduce the area and simultaneously improve the image resolution. Both thallium-doped CsI (CsI:Tl) and Gd2O2S:Tb scintillator screens were used as converters for incident X-rays to visible light photons. The optical property and X-ray imaging characterization such as X-ray to light response as a function of incident X-ray exposure dose, spatial resolution and X-ray images of objects were measured under different X-ray energy conditions. The measured results suggest that our developed CMOS-based X-ray imaging detector has the potential for fluoroscopic imaging and cone-beam computed tomography (CBCT) imaging applications.
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We present evaluation results of the 940nm 400mW transverse single-mode laser diodes (LDs) with real reflective index self-aligned (RISA) structure based on graded index separate confinement hetero structures (GRIN-SCH) for a... more
We present evaluation results of the 940nm 400mW transverse single-mode laser diodes (LDs) with real reflective index self-aligned (RISA) structure based on graded index separate confinement hetero structures (GRIN-SCH) for a three-dimensional (3D) depth sensor. The AlGaAs/InGaAs laser diodes that are adopted with RISA structure have many advantages over conventional complex refractive index guided lasers, what include low operating current, high temperature operation and stable fundamental transverse-mode operation up to high power levels. Simultaneously, the RISA process is easy to control the waveguide channel width and does not require stable oxide mask for the regrowth of aluminum alloys, so it is possible to manufacture high output power and high reliability laser diodes. At the optical power 400mW under the continuous-wave (CW) operation, Gaussian narrow far-field patterns (FFP) are measured with the full-width at half-maximum vertical divergence angle of 23°. A threshold current (Ith) of 33mA, slope efficiency (SE) of 0.81mW/mA and operating current (Iop) of 503mA are obtained at room temperature. Also, we could achieve catastrophic optical damage (COD) of 657mW and long-term reliability of 60°C with TO-56 package.
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Can artificial intelligence (AI) learn complicated non-linear physics? Here we propose a novel deep learning approach that learns non-linear photon scattering physics and obtains accurate 3D distribution of optical anomalies. In contrast... more
Can artificial intelligence (AI) learn complicated non-linear physics? Here we propose a novel deep learning approach that learns non-linear photon scattering physics and obtains accurate 3D distribution of optical anomalies. In contrast to the traditional black-box deep learning approaches to inverse problems, our deep network learns to invert the Lippmann-Schwinger integral equation which describes the essential physics of photon migration of diffuse near-infrared (NIR) photons in turbid media. As an example for clinical relevance, we applied the method to our prototype diffuse optical tomography (DOT). We show that our deep neural network, trained with only simulation data, can accurately recover the location of anomalies within biomimetic phantoms and live animals without the use of an exogenous contrast agent.
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We have studied experimentally a high power booster of Yb:YAG single-crystal fiber with regenerative amplifier based on dual-slab Yb:KGW crystals. The booster provided the output power of 45 W with the gain of 3. It allowed the laser... more
We have studied experimentally a high power booster of Yb:YAG single-crystal fiber with regenerative amplifier based on dual-slab Yb:KGW crystals. The booster provided the output power of 45 W with the gain of 3. It allowed the laser system to maintain the spectral bandwidth.
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Hybrid Yb:Y2O3 ceramic thin-rod femtosecond amplifier is reported. By 4-pass amplification scheme, output power of 1.4 W with gain of 14 is achieved from 100 mW, 1033 nm, 30 MHz fiber seeder. The extracted gain spectrum shows gain... more
Hybrid Yb:Y2O3 ceramic thin-rod femtosecond amplifier is reported. By 4-pass amplification scheme, output power of 1.4 W with gain of 14 is achieved from 100 mW, 1033 nm, 30 MHz fiber seeder. The extracted gain spectrum shows gain bandwidth of about 5.0 nm centered at 1030.6 nm.
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High-power femtosecond (fs) lasers in the visible wavelength regime have numerous applications in areas including micro-machining, medical eye surgery, communication, spectroscopy, etc. To generate this laser beam, frequency conversion,... more
High-power femtosecond (fs) lasers in the visible wavelength regime have numerous applications in areas including micro-machining, medical eye surgery, communication, spectroscopy, etc. To generate this laser beam, frequency conversion, especially second-harmonic generation (SHG), of near-IR lasers using nonlinear optical crystals is known to be the most standard technique. However, the use of a long-length crystal, which is preferred to achieve high SHG conversion efficiency for long-pulse or cw lasers, cannot be applied to the fs laser with broad linewidth due to the tight phase matching condition and the exacerbated walk-off effect. Thus the conditions of the nonlinear optical crystal should be optimized to achieve efficient SHG generation and hence, the high power visible fs laser pulses. There are many reports for the efficient SHG of the fs lasers but not many reports about influence of the crystal length on the SHG process, such as the pulse width and the linewidth and the co...
We report a frequency domain DOT system with high-speed data acquisition to improve the diagnostic accuracy of DBT. We test the basic performance of the DOT system with optical phantom and can obtain DBT/DOT images using blood vessel... more
We report a frequency domain DOT system with high-speed data acquisition to improve the diagnostic accuracy of DBT. We test the basic performance of the DOT system with optical phantom and can obtain DBT/DOT images using blood vessel mimic phantom.
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This paper describes a study on a novel X-ray detector with photoinduced discharge (PID) readout devices. Especially, we demonstrated optical scanning X-ray imaging devices based on intrinsic hydrogenated amorphous silicon (i-a-Si:H) PID... more
This paper describes a study on a novel X-ray detector with photoinduced discharge (PID) readout devices. Especially, we demonstrated optical scanning X-ray imaging devices based on intrinsic hydrogenated amorphous silicon (i-a-Si:H) PID readout layer, on which a pixelated metal layer, molybdenum, is formed as a charge accumulation layer of <inline-formula> <tex-math notation="LaTeX">$200~\\mu \\text{m}$ </tex-math></inline-formula> pitch for clearly defining the pixel in the lateral and longitudinal directions. We decided to use i-a-Si:H as a readout layer instead of amorphous selenium(a-Se) layer because the material of a-Se does not withstand standard wet fabrication processes like lift-off wet process. An X-ray absorption layer of <inline-formula> <tex-math notation="LaTeX">$500~\\mu \\text{m}$ </tex-math></inline-formula> thick a-Se is formed by a thermal evaporation process. To optically switch on the i-a-Si:H PID readout layer, we use a narrow line-beam with a beam width of <inline-formula> <tex-math notation="LaTeX">$50~\\mu \\text{m}$ </tex-math></inline-formula> consisting of a blue LED array, optical films, and GRIN lens array. The pixelated PID readout X-ray detector is <inline-formula> <tex-math notation="LaTeX">$512\\times512$ </tex-math></inline-formula> image resolutions with a <inline-formula> <tex-math notation="LaTeX">$200~\\mu \\text{m}$ </tex-math></inline-formula> pitch, and the overall active dimension is 10.24 cm <inline-formula> <tex-math notation="LaTeX">$\\times10.24$ </tex-math></inline-formula> cm. The sensitivity of the pixelated PID readout X-ray detector is 302 pC/cm<inline-formula> <tex-math notation="LaTeX">$^{2}\\cdot $ </tex-math></inline-formula>mR at Normal X-ray Tube conditions (IEC66220-1). According to MTF measurement results, the value of MTF0.1(10%) is measured at near 2.5 1/mm in the column direction scanning while the value is measured at 1.9-2.5 1/mm in the row direction scanning.
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Diffuse optical tomography (DOT) non-invasively measures the functional characteristics of breast lesions using near infrared light to probe tissue optical properties. This study aimed to evaluate a new digital breast tomosynthesis... more
Diffuse optical tomography (DOT) non-invasively measures the functional characteristics of breast lesions using near infrared light to probe tissue optical properties. This study aimed to evaluate a new digital breast tomosynthesis (DBT)/DOT fusion imaging technique and obtain preliminary data for breast cancer detection. Twenty-eight women were prospectively enrolled and underwent both DBT and DOT examinations. DBT/DOT fusion imaging was created after acquisition of both examinations. Two breast radiologists analyzed DBT and DOT images independently, and then finally evaluated the fusion images. The diagnostic performance of each reading session was compared and interobserver agreement was assessed. The technical success rate was 96.4%, with one failure due to an error during DOT data storage. Among the 27 women finally included in the analysis, 13 had breast cancer. The areas under the receiver operating characteristic curve (AUCs) for DBT were 0.783 and 0.854 for readers 1 and 2,...
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Conventional approaches in diffuse optical tomography (DOT) image reconstruction often address the ill-posed inverse problem via regularization with a constant penalty parameter, which uniformly smooths out the solution. In this study, we... more
Conventional approaches in diffuse optical tomography (DOT) image reconstruction often address the ill-posed inverse problem via regularization with a constant penalty parameter, which uniformly smooths out the solution. In this study, we present a data-specific mask-guided scheme that incorporates a prior mask constraint into the image reconstruction framework. The prior mask was created from the DOT data itself by exploiting the multi-measurement vector formulation. We accordingly propose two methods to integrate the prior mask into the reconstruction process. First, as a soft prior by exploiting a spatially varying regularization. Second, as a hard prior by imposing a region-of-interest-limited reconstruction. Furthermore, the latter method iterates between discrete and continuous steps to update the mask and optical parameters, respectively. The proposed methods showed enhanced optical contrast accuracy, improved spatial resolution, and reduced noise level in DOT reconstructed images compared with the conventional approaches such as the modified Levenberg-Marquardt approach and the l1-regularization based sparse recovery approach.
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We present a hybrid chirped pulse amplification femtosecond laser amplification system with which to realize a Yb:KGW regenerative amplifier (RGA) and a Yb:YAG thin-rod amplifier. The combination of RGA based on dual Yb:KGW crystals and a... more
We present a hybrid chirped pulse amplification femtosecond laser amplification system with which to realize a Yb:KGW regenerative amplifier (RGA) and a Yb:YAG thin-rod amplifier. The combination of RGA based on dual Yb:KGW crystals and a thin-rod Yb:YAG amplifier with a high gain brings about output power up to 46 W before and 29.2 W after pulse compression down to 277 fs at a repetition rate of 200 kHz. The gain-narrowing effect was complemented by a combination of different types of gain-medium amplification. The results show that the output power of a Yb:KGW-based amplifier can be amplified simply by using a Yb:YAG thin-rod amplifier while suppressing the broadening of the pulse duration by gain narrowing.
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A three-stage laser amplification system based on thin Yb : YAG rods with diode laser pumping is developed and fabricated. In this system, the average power of a continuous train of femtosecond pulses from a Yb : KGW master oscillator... more
A three-stage laser amplification system based on thin Yb : YAG rods with diode laser pumping is developed and fabricated. In this system, the average power of a continuous train of femtosecond pulses from a Yb : KGW master oscillator with a pulse repetition rate of 80 MHz and initial pulse duration of 128 fs was raised by a factor of 100 to above 100 W. Preliminarily chirped laser pulses provided compensation of dispersion in optical elements of the system and obtaining 580-fs output pulses. The longer duration of output pulses relates to spectrum narrowing in the amplifiers.
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A number of femtosecond laser systems have been created based on the amplification of chirped and supershort pulses and implemented in broadband ytterbium-doped laser gain media (Yb:KGW and Yb:YAG) with direct laser diode pumping. The use... more
A number of femtosecond laser systems have been created based on the amplification of chirped and supershort pulses and implemented in broadband ytterbium-doped laser gain media (Yb:KGW and Yb:YAG) with direct laser diode pumping. The use of various active element geometries in the form of thin plates and thin rods makes it possible to obtain pulses with an average radiation power of 10–100 W. The quality of the laser beam is close to that of a diffraction-limited beam. All of these parameters allow the use of laser systems developed for various technological and biomedical applications requiring high-precision laser exposure.
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A Micro holes in a diamond are presented by using a homemade femtosecond (fs) Yb:KGW laser. An fs laser source was used emitting pulse duration of 230 fs at 1030 nm wavelength, whereas the spot size amounted to 8.9 μm. Parameters like... more
A Micro holes in a diamond are presented by using a homemade femtosecond (fs) Yb:KGW laser. An fs laser source was used emitting pulse duration of 230 fs at 1030 nm wavelength, whereas the spot size amounted to 8.9 μm. Parameters like pulse energy, and pulse number were varied over a wide range in order to evaluate their influence both on the micro hole geometry like hole diameter, circularity, taper angle, and on the drilling quality. Hourglass-shaped micro holes whose diameters decrease and increase again after a certain depth have important applications. The results demonstrate the feasibility of extending the drilling of an hourglass-shaped hole in a diamond sample, which has similar diameters at the hole entrance (92 μm) and exit (95 μm), but a much smaller diameter (28 μm) at a certain waist section inside the hole.
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We investigate experimentally and theoretically the band structure of the (In0.53Ga0.47As)1−z (In0.52Al0.48As)z digital alloy grown by using molecular beam epitaxy as a function of z, where z is defined by the thickness fraction of the... more
We investigate experimentally and theoretically the band structure of the (In0.53Ga0.47As)1−z (In0.52Al0.48As)z digital alloy grown by using molecular beam epitaxy as a function of z, where z is defined by the thickness fraction of the InGaAs and the InAlAs layers lattice-matched to InP. To calculate the band structures of the InGaAs/InAlAs digital alloy, we used the 4 × 4 k·p method; then, we compared these band structures with the photoluminescence experimental results. These experimental and theoretical results show that the InGaAs/InAlAs digital alloy not only can contribute to the method of band-gap engineering by using various types of thickness combinations but also can cover the wavelength gap of 1.2 μm (1.1 μm (GaAs) < λ < 1.3 μm (InP)), that only the quantum dot can cover. We also propose a quantum-well structure that is able to cover the wavelength gap.
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We present a methodology for the optimization of sampling schemes in diffuse optical tomography (DOT). The proposed method exploits singular value decomposition (SVD) of the sensitivity matrix, or weight matrix, in DOT. Two mathematical... more
We present a methodology for the optimization of sampling schemes in diffuse optical tomography (DOT). The proposed method exploits singular value decomposition (SVD) of the sensitivity matrix, or weight matrix, in DOT. Two mathematical metrics are introduced to assess and determine the optimum source–detector measurement configuration in terms of data correlation and image space resolution. The key idea of the work is to weight each data measurement, or rows in the sensitivity matrix, and similarly to weight each unknown image basis, or columns in the sensitivity matrix, according to their contribution to the rank of the sensitivity matrix, respectively. The proposed metrics offer a perspective on the data sampling and provide an efficient way of optimizing the sampling schemes in DOT. We evaluated various acquisition geometries often used in DOT by use of the proposed metrics. By iteratively selecting an optimal sparse set of data measurements, we showed that one can design a DOT ...
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ABSTRACT We report optical properties of full digital-alloy InGaAlAs mutli-quantum wells (MQWs). All layer of InGaAlAs consist of short period superlattices of sub nanometer thick InAlAs and InGaAs. We found that the activation energies... more
ABSTRACT We report optical properties of full digital-alloy InGaAlAs mutli-quantum wells (MQWs). All layer of InGaAlAs consist of short period superlattices of sub nanometer thick InAlAs and InGaAs. We found that the activation energies of the MQWs are closely related to pits of electron reflections in digital-alloy InGaAlAs. Finally, we report 200 mW CW operation of 1.3 μm full digital-alloy InGaAlAs laser diodes. nGaAlAs/InP has received considerable attention as an important alternative system to conventional InGaAsP/InP for the application of 1.3 - 1.55 μm uncooled laser diode and surface-emitting laser diode,(1) because the former has a higher characteristic temperature (T0) due to a larger conduction band offset,(2) and a larger refractive index difference.(3) Molecular beam epitaxy (MBE) is promising growth technology considering the benefits of the ultra-vacuum environment such as low incorporation of oxygen impurity during the growth of aluminum-containing material and availability of ultra-high-purity aluminum source. Additionally, the conventional problem with the growth of phosphides by MBE has been almost solved by many approaches.(4) However, in order to obtain multiple-alloy In1-x-yGayAlxAs, rigorous attentions should be paid on the growth interruption and change of source cell temperature, or additional source cells must be equipped to conventional MBE system. Digital-alloys, or short-period superlattices (SPSs) consisting of binary or ternary layers with a period of a few monolayers (MLs), has emerged not only as a solution for the growth of ternary or quaternary materials of various composition without additional source cells and laborious change of cell temperature during
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In the biosensing platform, label-free detection technique provides advantages such as the short analysis time and the cost-effectiveness. In this study, we showed the feasibility of the LSPR substrate with gold nanoparticle array for... more
In the biosensing platform, label-free detection technique provides advantages such as the short analysis time and the cost-effectiveness. In this study, we showed the feasibility of the LSPR substrate with gold nanoparticle array for detecting low density lipoprotein (LDL) and high density lipoprotein (HDL) without labeling. The LSPR substrate was fabricated through the lift-off process with the anodized alumina mask, and its LSPR phenomenon was observed by measuring the optical transmission of substrate. The antibodies were immobilized on the gold nanoparticle array via the chemical binding, in which the 11-MUA was used as the linker to bind the antibodies. The binding of antibodies was confirmed by observing the shift of LSPR peak of the substrate. Finally, with the LSPR substrates with the antibodies immobilized, the detection of LDL and HDL was investigated. As a result, LDL and HDL could be detected in the clinically available concentration range, respectively.
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ABSTRACT We developed a novel direct X-ray detector using photoinduced discharge (PID) readout for digital radiography. The pixel resolution is 512 × 512 with 200 μm pixel and the overall active dimensions of the X-ray imaging panel is... more
ABSTRACT We developed a novel direct X-ray detector using photoinduced discharge (PID) readout for digital radiography. The pixel resolution is 512 × 512 with 200 μm pixel and the overall active dimensions of the X-ray imaging panel is 10.24 cm × 10.24 cm. The detector consists of an X-ray absorption layer of amorphous selenium, a charge accumulation layer of metal, and a PID readout layer of amorphous silicon. In particular, the charge accumulation is pixelated because image charges generated by X-ray should be stored pixel by pixel. Here the image charges, or holes, are recombined with electrons generated by the PID method. We used a 405 nm laser diode and cylindrical lens to make a line beam source with a width of 50 μm for PID readout, which generates charges for each pixel lines during the scan. We obtained spatial frequencies of about 1.0 lp/mm for the X-direction (lateral direction) and 0.9 lp/mm for the Y-direction (scanning direction) at 50% modulation transfer function.
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A high-temperature characteristics of 1.52 μm InGaAs ridge waveguide laser diode (LD) with InGaAs/InAlAs short period superlattices (SPSs) barriers is reported. The SPSs are grown by digital-alloy molecular beam epitaxy (MBE). There have... more
A high-temperature characteristics of 1.52 μm InGaAs ridge waveguide laser diode (LD) with InGaAs/InAlAs short period superlattices (SPSs) barriers is reported. The SPSs are grown by digital-alloy molecular beam epitaxy (MBE). There have been similar studies at the 0.98 μm LD using GaAs/AlGaAs SPSs barrier (T0=300 K) and 1.3 μm InGaAsP LD using (InGaAsP)4/(InP)5 SPSs barrier (T0=90 K). On the
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ABSTRACT Three types of thin layer were inserted between 1st and 2nd separate confinement heterostructure (SCH) layer of 1.55 micrometers InGaAaP/InGaAs multi-quantum well (MQW) laser diodes. The three types were Type A (p-InGaAsP,... more
ABSTRACT Three types of thin layer were inserted between 1st and 2nd separate confinement heterostructure (SCH) layer of 1.55 micrometers InGaAaP/InGaAs multi-quantum well (MQW) laser diodes. The three types were Type A (p-InGaAsP, 1x1017/cm3), Type B (p-InGaAsP, 2x1018/cm3), and Type C (p-InP, 2x1018/cm3), respectively. It was shown that the light-current (L-I) characteristics for those three types were similar, while the characteristic temperature (T0) was higher for type B than others.
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Localized surface plasmon resonance (LSPR) is a promising method for detecting antigen-antibody binding in label-free biosensors. In this study, the fabrication of a LSPR substrate with a gold nanodot array through the lift-off process of... more
Localized surface plasmon resonance (LSPR) is a promising method for detecting antigen-antibody binding in label-free biosensors. In this study, the fabrication of a LSPR substrate with a gold nanodot array through the lift-off process of an alumina mask is reported. The substrate showed an extinction peak in its extinction spectrum, and the peak position was dependent on the height of the gold nanodot array, and the change of extinction peak with the height could be predicted by the numerical simulation. In addition, the peak position was observed to be red-shifted with the increasing RIU value of the medium surrounding the gold nanodot array. In particular, the peak position in the 10 nm thick gold nanodot array was approximately 710 nm in air, and the sensitivity, defined as the ratio of the shift of peak position to the RIU of the medium, was 323.6 nm/RIU. The fabrication procedure could be applied to fabricate the LSPR substrates with a large area.