Red Laser Beam Research Articles

Direct and parametric synchronization of a graphene self-oscillator

We explore the dynamics of a graphene nanomechanical oscillator coupled to a reference oscillator. Circular graphene drums are forced into self-oscillation, at a frequency fosc, by means of photothermal feedback induced by illuminating the drum with a continuous-wave red laser beam. Synchronization to a reference signal, at a frequency fsync, is achieved by shining a power-modulated blue laser onto the structure. We investigate two regimes of synchronization as a function of both detuning and signal strength for direct (fsync≈fosc) and parametric locking (fsync≈2fosc). We detect a regime of phase resonance, where the phase of the oscillator behaves as an underdamped second-order system, with the natural frequency of the phase resonance showing a clear power-law dependence on the locking signal strength. The phase resonance is qualitatively reproduced using a forced van der Pol-Duffing-Mathieu equation.

Multimodal laser-based angioscopy for structural, chemical and biological imaging of atherosclerosis.

The complex nature of atherosclerosis demands high-resolution approaches to identify subtle thrombogenic lesions and define the risk of plaque rupture. Here, we report the proof-of-concept use of a multimodal scanning fiber endoscope (SFE) consisting of a single optical fiber scanned by a piezoelectric drive that illuminates tissue with red, blue, and green laser beams, and digitally reconstructs images at 30 Hz with high resolution and large fields-of-view. By combining laser-induced reflectance and fluorescence emission of intrinsic fluorescent constituents in arterial tissues, the SFE allowed us to co-generate endoscopic videos with a label-free biochemical map to derive a morphological and spectral classifier capable of discriminating early, intermediate, advanced, and complicated atherosclerotic plaques. We demonstrate the capability of scanning fiber angioscopy for the molecular imaging of vulnerable atherosclerosis by targeting proteolytic activity with a fluorescent probe activated by matrix metalloproteinases. We also show that the SFE generates high-quality spectral images in vivo in an animal model with medium-sized arteries. Multimodal laser-based angioscopy could become a platform for the diagnosis, prognosis, and image-guided therapy of atherosclerosis.

Wavelength tunable CW red laser generated based on an intracavity-SFG composite cavity

We report a wavelength-tunable watt-level continuous wave (CW) red laser that uses a composite cavity based on an intracavity sum-frequency generation (SFG). The composite cavity is composed of a LD side-pumped Nd: GdVO4 p-polarized 1062.9 nm resonant cavity and a resonant optical parametric oscillator (SRO) of s-polarized signal light using a periodically poled crystal MgO: PPLN. Based on the temperature tuning from 30 °C to 200 °C, the CW red laser beams are obtained in a tunable waveband from 634.4 nm to 649.1 nm, corresponding to a tunable output waveband from 3278.0 nm to 2940.2 nm of the mid-infrared idler lights. The maximum CW output power of the red laser at 634.4 nm and the idler light at 3278.0 nm reach 3.03 W and 4.13 W under 30 °C, respectively.

Parameters Influencing Soot Oxidation Rates in an Optical Diesel Engine

Soot emissions from diesel engines are the net result of two competing processes: soot formation and soot oxidation. Previous studies have shown poor correlation between soot formation rates and the soot emissions. This article presents a systematic study of a number of parameters affecting soot oxidation rate and how it correlates with the soot emissions. An optical heavy-duty engine is used in conjunction with a laser extinction setup in order to collect time resolved data of the soot concentration in the cylinder during the expansion stroke. Laser extinction is measured using a red (685 nm) laser beam, which is sent vertically through the cylinder and modulated to produce 10 pulses per crank angle degree. Information is obtained about the amount of soot formed and the soot oxidation rate. The parameters studied are the motored density at top dead center (TDC), motored temperature at TDC, injection pressure, engine speed, swirl level and injector orifice diameter. A central composite design is employed to assess the importance of the parameters as well as identifying potential interaction effects. A single exponential decay function is fit to the extinction data to describe the oxidation process and the half-life of the decay is used as a measure of the oxidation rate. The half-lives are compared with engine out emissions and the importance of each parameter is studied using regression analysis. The results suggest that the injection pressure has the strongest effect on the late-cycle soot oxidation rate, while the temperature at TDC has the weakest effect of the parameters studied. (Less)

Single-Slit Diffraction: Transitioning from Geometric Optics to the Fraunhofer Regime

Suppose a red laser beam (of wavelength λ equal to 0.660 μm) is expanded using an optical telescope into a collimated, approximately plane wave that is 5.68 mm in diameter. Pass that beam through a tall rectangular slit whose width a is gradually reduced from 3.30 to 0.100 mm. Look at its image on a screen located at a distance L from the slit equal to 0.656 m. As the slit is narrowed, you predict that the width of the pattern will: smoothly increase,smoothly decrease,increase and then decrease, ordecrease and then increase.

109 Multimodal Endovascular Endoscopy in Carotid Atherosclerotic Disease

Disruption of vulnerable atherosclerotic plaque is the precipitating factor that culminates in thrombosis and ischemia. Current technologies do not have sufficient power to identify subtle thrombogenic lesions (ie, ulcers) in the arterial endoluminal surfaces nor reliably predict markers for future symptomatology. We developed an ultra-thin scanning fiber endoscope (SFE) to directly visualize the endoluminal surface of carotid arteries and identify structural, chemical, and biological markers of vulnerable and complicated atherosclerotic plaques. 1.2 mm and 2.1 mm endoscopes containing single optical fiber scanned by a piezoelectric drive mechanism were developed to illuminate tissue surfaces with red, blue, and green laser beams (RBG). Laser-induced backscattering (reflectance) and tissue fluorescence collected by a ring of optical fibers were then digitalized to reconstruct color videos with large fields of view. Then, SFE was studied ex vivo in human carotid arteries and in vivo in a rabbit model of atherosclerosis. After imaging, specimens were processed for histology; lesions were independently reviewed by 2 pathologists and matched to endoscopic images with analysis of variance. High-definition structural and chemical images of 20 carotid arteries harvested during hospital autopsies revealed 42 lesions. Based on anatomical features and tissue fluorescence, we developed a classifier that enabled identification of: healthy endovascular regions (smooth surfaces with strong homogeneous fluorescence); early plaques (dot or streak-like elevated lesions with low fluorescence); advance plaques (irregular elevated lesions with minimal to absent fluorescence); and complicated plaques (ulcers: punch-out dark-gray lesions with raised irregular bead-like borders and speckled fluorescence pattern; hematoma: absent reflection, black regions, and fluorescence). The image quality and validity of the classifier were reproduced in vivo in an atherogenic rabbit model. Multimodal SFE generates high-definition structural and label-free chemical images, and detects with high sensitivity and specificity small intravascular thrombi and subtle surface thrombogenic lesions in nonstenosing complicated plaques, even in cases not detected by conventional diagnostic modalities. Therefore, it holds the potential for becoming a new imaging platform in cerebrovascular and cardiovascular disease.

Comparative analysis of microwave low‐noise amplifiers under laser illumination

ABSTRACTThis article deals with the analysis of the effects of 650 nm laser light exposure of AlGaAs/GaAs HEMTs employed in X‐band low‐noise amplifiers (LNAs). The devices have scaled gate widths of 100, 200, and 300 μm and a gate length of 0.25 μm. They were characterized under dark and illuminated conditions through scattering and noise parameter measurements in the 2–18 GHz frequency range. Starting from the experimental data, LNAs have then been designed and tailored to each device type in dark mode operation over the 7.5–8.5 GHz frequency range. Subsequently, the performance of the LNAs under light exposure has been evaluated by employing the illuminated device data. Therefore, a comparative analysis of the observed variations is here reported to assess the influence of the red laser beam on the amplifier's response with a special concern for the noise behavior due to the inherent interest in optical control of microwave circuitry for high‐data‐rate, low‐noise telecommunication systems. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2437–2443, 2016

Potential of an aircraft landing laser system

The paper presents calculation results obtained for the laser landing system (LLS) efficiency on the base of determining minimum required scattered radiation fluxes from fixed extended landmarks (FELs) which are LLS indicators in the case of visual FEL detection in real operational conditions. It is shown that the minimum required powers for a reliable detection of course glide beams in night conditions from distances L ≈ 1.0–1.6 km at meteorological visibility Sm = 800 m are Pmin = 0.5 W for λ = 0.52 and 0.64 µm for deviations from the glide path to the angle φ = 0°–5°. In twilight conditions, green and red laser beams are visible from distances L = 1–1.2 km. The performed calculations corroborated the possibility of creating a new generation laser-based LLS capable of ensuring aircraft landing in conditions of International Civil Aviation Organization (ICAO) category 1.

SU‐F‐T‐434: Development of a Fan‐Beam Optical Scanner Using CMOS Array for Small Field Dosimetry

Purpose:To design and construct a second generation optical computed tomography (OCT) system using a fan‐beam with a CMOS array detector for the 3D dosimetry with polymer gel and radiochromic solid dosimeters. The system was specifically designed for the small field dosimetry.Methods:The optical scanner used a fan‐beam laser, which was produced from a collimated red laser beam (λ=620 nm) with a 15‐degree laser‐line generating lens. The fan‐beam was sent through an index‐matching bath which holds the sample stage and a sample. The emerging laser light was detected with a 2.54 cm‐long CMOS array detector (512 elements). The sample stage rotated through the full 360 degree projection angles at 0.9‐degree increments. Each projection was normalized to the unirradiated sample at the projection angle to correct for imperfections in the dosimeter. A larger sample could be scanned by using a motorized mirror and linearly translating the CMOS detector. The height of the sample stage was varied for a full 3D scanning. The image acquisition and motor motion was controlled by a computer. The 3D image reconstruction was accomplished by a fan‐beam reconstruction algorithm. All the software was developed inhouse with MATLAB.Results:The scanner was used on both PRESAGE and PAGAT gel dosimeters. Irreconcilable refraction errors were seen with PAGAT because the fan beam laser line refracted away from the detector when the field was highly varying in 3D. With PRESAGE, this type of error was not seen.Conclusion:We could acquire tomographic images of dose distributions by the new OCT system with both polymer gel and radiochromic solid dosimeters. Preliminary results showed that the system was more suited for radiochromic solid dosimeters since the radiochromic dosimeters exhibited minimal refraction and scattering errors. We are currently working on improving the image quality by thorough characterization of the OCT system.

Effects of violet-, green-, and red-laser illumination on gas-sensing properties of SnO thin film

We examined the gas-sensing properties of a 10-nm-thick SnO thin film under the illumination of violet, green, and red laser beams at room temperature. A comparison of the gas-sensing outputs of the device after operation in the dark at elevated temperatures (100, 150, and 200°C) and when illuminated by a laser beam at room temperature indicated that this metal-oxide film had good gas-sensing performance and excellent stability under the illumination of the violet beam. When exposed to several target gases, including NO2, SO2, H2S, and NH3, the SnO thin film was most sensitive to H2S with a minimum concentration of 5ppm. During the H2S test, a two-step response of the sensor was recorded, which provided information for understanding the effects of chemisorbed and photo-induced oxygen species on the gas-sensing properties of the illuminated sensor. A possible light-induced gas-sensing mechanism of the SnO thin film was proposed and investigated in detail.

Color Ghost Imaging with Pseudo-White-Thermal Light**Supported by the National Natural Science Foundation of China under Grant Nos 11047004, 11204062 and 11174038, the National High-Technology Research and Development Program of China under Grant No 2013AA122902, and the Youth Foundation of Hebei Educational Committee under Grant No QN2014086.

A pseudo-white-thermal light source is prepared by projecting three (red, green, and blue) laser beams onto a rotating ground glass disk. Based on the RGB color model, we investigate the color Hanbury-Brown-Twiss (HBT) effect and color ghost imaging with thermal light. The color HBT effect indicates that photons of the same color will bunch. This fact ensures the chromatic discrimination power of ghost imaging with thermal light. We retrieve the RGB ingredients of the object through intensity correlation measurements. A method of white balance to properly form the ghost images is proposed.

Fabrication of meso- and nano-scale structures on surfaces of chalcogenide semiconductors by surface hydrodynamic interference patterning

We observe the change of surface relief on amorphous Ge-As-Se thin films after irradiation with an electron beam. The beam softens the glass and induces various topological surface changes in the irradiated area. The film relief change depends on the film thickness, deposited charge, and film composition. Various structures are formed: Gausian-like cones, extremely sharp Taylor cones, deep craters, and craters with large spires grown on the side. Our investigation shows that these effects can be at least partially a result of electro-hydrodynamic material flow, but the observed phenomena are likely more complex. When we irradiated structural patterns formed by the electron beam with a red laser beam, we could not only fully relax the produced patterns, but also form very complex and intricate superstructures. These organized meso- and nano-scale structures are formed by a combination of photo-induced structural relaxation, light interference on structures fabricated by the e-beam, and photo-induced material flow.

Experiment evaluation of speckle suppression efficiency of 2D quasi-spiral M-sequence-based diffractive optical element.

The quasi-spiral 2D diffractive optical element (DOE) based on M-sequence of length N=15 is designed and manufactured. The speckle suppression efficiency by the DOE rotation is measured. The speckle suppression coefficients of 10.5, 6, and 4 are obtained for green, violet, and red laser beams, respectively. The results of numerical simulation and experimental data show that the quasi-spiral binary DOE structure can be as effective in speckle reduction as a periodic 2D DOE structure. The numerical simulation and experimental results show that the speckle suppression efficiency of the 2D DOE structure decreases approximately twice at the boundaries of the visible range. It is shown that a replacement of this structure with the bilateral 1D DOE allows obtaining the maximum speckle suppression efficiency in the entire visible range of light.

Up/down conversion switching by adjusting the pulse width of red laser beams in LaF₃:Tm³⁺ nanocrystals.

We demonstrate a versatile approach to fine-tuning the ratio of blue to near-infrared emission intensity from Tm3+ ions in LaF3 nanocrystals by adjusting the pulse widths and excitation wavelengths of red laser beams. The mechanism of color-tunable Tm3+ emission by pulse widths is explored, and a mechanism based on promoting the population of some luminescence levels and cutting off the population of others by suitably adjusting pulse duration is proposed. The underlying reason of excitation wavelength-modulated emission is ascribed to tuning absorption probability ratio of ground state absorption to excited state absorption by tuning the matching degree between the energies of excitation wavelength and ground (excited) state absorption of Tm3+. The ability of our LaF3:Tm3+ nanocrystals to emit variable emissions on demand in response to pulse width and excitation wavelength provides keen insights into controlling the population processes of luminescent levels and offers a versatile approach for tuning the spectral output.

Simple blood test for diagnosis of gastrointestinal and pancreas cancer using surface-enhanced Raman scattering.

32 Background: Surface-Enhanced Raman Scattering (SERS) has been widely applicated in industrial microanalysis, and researched to apply for various fields, for example biological research. We tried to detect the SERS spectra from blood samples obtained from patients with cancers or benign diseases by using a low intensity laser beam, and compared the SERS spectra pattern among the samples from the patient group. Methods: Blood samples were obtained from patients with gastric cancer (n=30), colorectal cancer (n=20), pancreas cancer (n=5) and benign diseases (n=20). All blood samples were centrifuged at 1600g for 7 minutes, and serum samples were extracted. The serum samples were placed on the phosphor bronze chip with silver nanoscale hexagonal columns (NHCs), and SERS spectra was detected by using low intensity helium-neon red laser beam with 633 nm as wavelength. Results: SERS spectra were detected in all samples within 4 minutes from irradiation. Limiting dilution of detecting SERS was 1/1000 of serum. SERS spectra patterns were different between cancer and benign disease patients, and maximum peak level of the SERS in the samples from cancer patients were significantly higher than those from benign disease patients. There was a difference on the wavelength of Raman shifting at the peak intensity and the pattern of the SERS spectra between the samples from the patients with cancers and benign diseases. And furthermore, there was a difference on the SERS spectra pattern among the samples from the patients with gastric, colon and pancreas cancer. Additionally, it was suggested that the elements combined with the silver NHCs were histone-and-DNA complex. Conclusions: Our data suggest that our simple blood test using SERS is useful for diagnosis of gastrointestinal and pancreas cancer. We have been trying molecular analysis of the element combined with the silver NHCs by next-generation sequencer. Clinical trial information: UMIN000009818.

TCT measurements with slim edge strip detectors

Transient current technique (TCT) measurements with focused laser light on miniature silicon strip detectors (n+-type strips on p-type bulk) with one inactive edge thinned to about 100µm using the Scribe-Cleave-Passivate (SCP) method are presented. Pulses of focused IR (λ=1064nm) laser light were directed to the surface of the detector and charge collection properties near the slim edge were investigated. Measurements before and after irradiation with reactor neutrons up to 1MeV equivalent fluence of 1.5×1015neq/cm2 showed that SCP thinning of detector edge does not influence its charge collection properties.TCT measurements were done also with focused red laser beam (λ=640nm) directed to the SCP processed side of the detector. The absorption length of red light in silicon is about 3µm so with this measurement information about the electric field at the edge can be obtained. Observations of laser induced signals indicate that the electric field distribution along the depth of the detector at the detector edge is different than in the detector bulk: electric field is higher near the strip side and lower at the back side. This is a consequence of negative surface charge caused by passivation of the cleaved edge with Al2O3. The difference between bulk and edge electric field distributions gets smaller after irradiation.

Position-addressable digital laser scanning point fluorescence microscopy with a Blu-ray disk pickup head

A compact and position-addressable blue ray scanning microscope (BSM) based on a commercially available Blu-ray disk pickup head (PUH) is developed for cell imaging with high resolution and low cost. The BSM comprises two objective lenses with numerical apertures (NAs) of 0.85 and 0.6 for focusing blue and red laser beams, respectively, on the sample slide. The blue and red laser beams are co-located adjacent to each other and move synchronously. A specially designed sample slide is used with a sample area and an address-patterned area for sample holding and address recognition, respectively. The blue laser beam is focused on the sample area and is used for fluorescent excitation and image capturing, whereas the red laser beam is focused on the address-patterned area and is used for address recognition and dynamic focusing. The address-patterned area is divided into 310 sectors. The cell image of each sector of the sampling area has a corresponding address pattern. Fluorescence images of monkey-derived kidney epithelial cells and fibroblast cells in which the F-actin is stained with fluorophore phalloidin CF 405 are measured by the BSM, with results comparable to those measured by a Leica TCS CP2 confocal microscope. The cell image of an area of interest can be easily tracked based on the coded address, and a large-area sample image can be accurately reconstructed from the sector images.

Use of surface-enhanced Raman scattering for detection of cancer-related serum-constituents in gastrointestinal cancer patients

Laser-mediated surface-enhanced Raman scattering (SERS) has industrial and biological applications. We have developed a rapid and simple method for generating silver nanoscale hexagonal columns (NHCs) on the surface of a phosphor bronze chip for measurement of SERS spectra. This was used to detect SERS spectra from blood samples obtained from patients with gastric cancer, colorectal cancer, or benign diseases (n=12 each) using a low intensity helium-neon red laser beam with a 632.8-nm wavelength; the intensity of the SERS spectra was compared among the patient groups. The peak heights of SERS spectra from patients with benign diseases were significantly lower than those from patients with gastric or colorectal cancer, whereas those from patients with gastric cancer and colorectal cancer did not differ significantly. Thus, SERS using NHC chips holds promise for the easier and faster detection of cancer-related serum-constituents as biomarkers. From the Clinical EditorIn this study, laser-mediated surface-enhanced Raman scattering (SERS) was utilized as a sensitive detection method of cancer-related serum-constituents in gastric and colorectal cancer, via the use of silver nanoscale hexagonal columns on the surface of a phosphor bronze chip for measurement of SERS spectra, paving the way to the development of a rapid and high throughput tool for cancer screening and therapy monitoring.

Application of a He3Ne infrared laser source for detection of geometrical dimensions of cracks and scratches on finished surfaces of metals

In this study, the authors addressed a new method of measurement for microscratches and cracks on finished metallic surfaces. The technology proposed here can be used in aviation, automobile, machine-tools, bearings, electrical and thermal devices (detection of electrical and thermal contact resistance), and many other industrial fields where finished surfaces have to be inspected for quality before use. The technology is based on the application of He3Ne laser optics. This measurement method allows for the inspection of geometrical parameters such as depth and width of scratches and cracks and consists of a low-energy He3Ne red laser beam (wavelength 633nm) with a cross-section of 0.48mm, beam expander with special designed slit, multi-axis stage with sample holder and CCD (charge-coupled device) visual detection system. Using experimental data, a mathematical algorithm was created in order to calculate the depths and widths of the scratches and cracks where the method of center of gravity (centroid) of the imaged area was used. The results showed a good correlation between the experimental and calculated values of the dimensions of the scratches. Future work will deal with the determination of the geometrical dimensions of microcracks.

Bessel standing wave technique for optical induction of complex refractive lattice structures in photorefractive materials

A novel counter-propagating Bessel beam technique is suggested and realized for optical formation of complex two-dimensional (2D) refractive lattice structures in photorefractive materials. The 2D complex lattices optically induced by the suggested method are a combination of annular and planar gratings with refractive index modulation in the radial direction in the transverse plane and the in axial direction along the optical beam propagation. The recording of the lattices is performed by 532 nm and 633 nm laser beams. The counter-propagating beam geometry builds up the Bessel standing wave with periodic annular structure in each anti-node. The refractive lattices are recorded in Z- and Y-cut 2 mm thick photorefractive lithium niobate crystals singly doped by Fe and doubly doped by Fe and Cu. The readout of recorded lattices is performed by Gaussian red and green probe laser beams. The direct observation of recorded lattices by optical phase microscope is also performed. The formed photonic structures have a period of 10 ± 1 m in the radial direction and a half-wavelength standing wave period of 266 nm or 316.5 nm in the axial direction. The diffraction efficiency of the photonic lattices reaches up to 25%.