Laser Physics Research Papers - Academia.edu (original) (raw)

Two twelve-channel arrays based on surface-etched slot gratings, one with nonuniformly spaced slots and another with uniformly spaced slots are presented for laser operation in the O-band. A wavelength tuning range greater than 40 nm,... more

Two twelve-channel arrays based on surface-etched slot gratings, one with nonuniformly spaced slots and another with uniformly spaced slots are presented for laser operation in the O-band. A wavelength tuning range greater than 40 nm, with a side-mode suppression ratio (SMSR) > 40 dB over much of this range and output power greater than 20 mW, was obtained for the array with non-uniform slots over a temperature range of 15°C-60°C. The introduction of multiple slot periods, chosen such that there is minimal overlap among the side reflection peaks, is employed to suppress modes lasing one free spectral range (FSR) from the intended wavelength. The tuning range of the array with uniformly spaced slots, on the other hand, was found to be discontinuous due to mode-hopping to modes one FSR away from the intended lasing mode which are not adequately suppressed. Spectral linewidth was found to vary across devices with the lowest measured linewidths in the range of 2 MHz to 4 MHz.

In a nonequlibrium plasma of a gas-discharge HgBr lamp, the terminal electronic state of the HgBr(B–X) radiative transition with a peak wavelength of 502 nm remains populated for a relatively long time and is repeatedly excited to the... more

In a nonequlibrium plasma of a gas-discharge HgBr lamp, the terminal electronic state of the HgBr(B–X) radiative transition with a peak wavelength of 502 nm remains populated for a relatively long time and is repeatedly excited to the upper state in collisions with plasma electrons. This transfer of the HgBr molecules from the ground state X to the excited state B is the main mechanism of formation of the light-emitting molecules especially when the lamp is excited by double current pulses. According to our simulations, due to the electron-induced transitions between HgBr(X) and HgBr(B), the output characteristics of the DBD lamp operating in a double-pulse regime are better than those of the lamp operating in a single-pulse regime. In the considered case, the peak power is calculated to increase by a factor of about 2 and the lamp efficiency increases by about 50%.

To look forward to new trends in modern gas lasers and their applations, the results of current theoretical and experimental studies on search of new active media for high-power short-wavelength gasdynamic and chemical lasers are... more

Growing need for Anitmonide based , room temperature, 2-5 μm, semiconductor laser, ultra low loss optical communication motivate me to do this work. The work describe in this proposal is aimed to use past investigated result of... more

Growing need for Anitmonide based , room temperature, 2-5 μm, semiconductor laser, ultra low loss optical communication motivate me to do this work. The work describe in this proposal is aimed to use past investigated result of photoluminescence from GalnSb/AllnSb type first multiple quantum wells grown on GaAs in new way. This investigation successfully found that luminescence lie in between 3-4 μm. In my demonstration I used eight different samples GalnSb/AlGalnSb/AllnSb multiple quantum well laser (In cylindrical VCSEL structure) attached in single 3D photonic crystal emitting mid infrared laser light to transmit binary data from one computer to another computer through chalcogenide optical fibers by using DWDM system.

Collection of particles from a laser-driven accelerator into a conventional beamline requires careful manipulation of the beam to handle the wide energy spread, large angular divergence and short pulse lengths characteristic of... more

Collection of particles from a laser-driven accelerator into a conventional beamline requires careful manipulation of the beam to handle the wide energy spread, large angular divergence and short pulse lengths characteristic of laser-driven acceleration. Accurate simulation of the first few millimetres is crucial in order to optimise the collecting elements such as solenoids or quadrupole magnets. Experiments and simulations both show significant emittance growth in this collection region. We have developed a multi-particle beam dynamics model using impact-t that includes the characteristic exponentially-decaying laser-driven energy spectrum and accurately models the emittance growth due to the large energy spread. In this paper we present theoretical relationships between energy spread and emittance growth, and compare these with the simulated emittance growth. Results show excellent correspondence between theory and simulation. The effect is negligible for lowenergy proton accelerators, but is important for electron accelerators and for proposed high-energy laser-driven proton accelerators.

A superluminal quantum-vortex model of the electron and the positron is produced from a superluminal double-helix model of the photon during electron-positron pair production. The two oppositely-charged (with Q = ±e sqrt (2/α) = 16.6e)... more

A superluminal quantum-vortex model of the electron and the positron is produced from a superluminal double-helix model of the photon during electron-positron pair production. The two oppositely-charged (with Q = ±e sqrt (2/α) = 16.6e) open-helix spin-½ half-photons compose the double-helix photon. These half-photons separate and curl up their separated superluminal single-helical trajectories to form an electrically-charged superluminal closed-helix spin-½ quantum-vortex electron model and a corresponding positron model. The helical radius and the Dirac equation's zitterbewegung angular frequency of the quantum vortex electron and positron models equal the helical radius and zitterbewegung angular frequency of the two spin-½ half-photons, each of energy E = mc^2 , that composed the double-helix photon model of energy E = 2mc^2 from which the electron and positron models were produced. The photon and electron models are also compatible when a photon of energy E > 2mc^2 produces a relativistic electron-positron pair. Implications of the quantum vortex electron model for electron stability are discussed.

The analytic propagation of coherent supergaussian (SG)-like beams was calculated after F. Gori [Optics Comm. 107 (1994) 335] by introducing a linear superposition of Laguerre-Gauss functions called “flattened gaussian beam”. Here we... more

The analytic propagation of coherent supergaussian (SG)-like beams was calculated after F. Gori [Optics Comm. 107 (1994) 335] by introducing a linear superposition of Laguerre-Gauss functions called “flattened gaussian beam”. Here we propose a new family of SG-like beams, written as the convolution of a gaussian with a rectangle function; then, the well known convolution theorem allows a straightforward and simple analytical calculation of the beam profile in the focal plane of an arbitrary focusing system. In addition, this method can be successfully applied to more complex cases, as the SG-like beams commonly emitted by hard-edged unstable resonators (beam energy distribution with a hole).

After the discovery of laser therapy it was realized it has useful application of wound healing and reduce pain, but due to the poor understanding of the mechanism and dose response this technique remained to be controversial for... more

After the discovery of laser therapy it was realized it has useful application of wound healing and reduce pain, but due to the poor understanding of the mechanism and dose response this technique remained to be controversial for therapeutic applications. In order to understand the working and effectiveness different experiments were performed to determine the laser beam effect at the cellular and tissue level. This article discusses the mechanism of beam interaction at tissues and cellular level with different light sources and dosimetry principles for clinical application of low level laser therapy. Different application techniques and methods currently in use for clinical treatment has also been reviewed.

We present preliminary experimental results of making homogeneous the raw pulsed beam emitted by a large-aperture (10cm x 5cm) excimer laser. To this end, we use a novel optical system which is able to make homogeneous “bad beams” having... more

We present preliminary experimental results of making homogeneous the raw pulsed beam emitted by a large-aperture (10cm x 5cm) excimer laser. To this end, we use a novel optical system which is able to make homogeneous “bad beams” having strong local intensity spikes, and to modulate almost continuously the spot size of the homogenized beam along one or both axes in a fixed target plane. We have evaluated the results using the standard parameters described in the ISO 13694:2000. We found that the reliability of the results is dependent on a number of factors. In particular, we propose an amendment of the definitions of the edge steepness and plateau uniformity that could improve the reliability of these parameters.

为了选择适合太阳光泵浦的激光材料，本文从四能级速率方程出发，综合考虑了太阳辐射带状光谱特性和激光材料对泵浦光吸收能力，建立了太阳光泵浦固体激光理论模型。利用该模型推导得到了单束光侧面泵浦和椭球腔侧面泵浦方式下的泵浦阈值表达式，并结合Nd3+∶YAG、Nd3+∶glass、Nd3+∶Cr3+∶GSGG... more

为了选择适合太阳光泵浦的激光材料，本文从四能级速率方程出发，综合考虑了太阳辐射带状光谱特性和激光材料对泵浦光吸收能力，建立了太阳光泵浦固体激光理论模型。利用该模型推导得到了单束光侧面泵浦和椭球腔侧面泵浦方式下的泵浦阈值表达式，并结合Nd3+∶YAG、Nd3+∶glass、Nd3+∶Cr3+∶GSGG (Nd3+∶Cr3+∶Gd3Sc2Ga3O12)、Cr3+∶BeAl2O4和Cr3+∶Nd3+∶YAG等激光材料的光谱参数，计算了这些材料的泵浦阈值光强。结果表明:在单束光侧面泵浦和椭球腔侧面泵浦方式下，Nd3+∶YAG的泵浦阈值光强分别为448个太阳常数和224个太阳常数，是比较适合用太阳光泵浦的激光材料。由于椭球腔的特殊结构，采用椭球腔侧面泵浦激光介质，阈值光强比较低。分析了泵浦阈值光强与材料直径的关系。该模型可用于从现有的激光材料中筛选出在太阳光泵浦下最易输出激光的工作物质。

Three-level laser Microchip laser Small signal gain coefficient Two-way loss in the resonator a b s t r a c t Evaluation method of the optimal reflection of the output coupler for a range of the pump power is presented. This optimal value... more

Three-level laser Microchip laser Small signal gain coefficient Two-way loss in the resonator a b s t r a c t Evaluation method of the optimal reflection of the output coupler for a range of the pump power is presented. This optimal value was estimated to maximize the slope efficiency of cw laser generation. The method was validated using generation results of three-level microchip lasers.

Lasers and Non Linear Optics The Whole Book
By
B.B. Laud

The main objective of this book is to investigate the effect of laser surface sealing processing of thermal barrier coatings produced by plasma spraying technique. The thermal barrier coatings produced by this technique suffer from many... more

The main objective of this book is to investigate the effect of laser
surface sealing processing of thermal barrier coatings produced by plasma
spraying technique. The thermal barrier coatings produced by this
technique suffer from many defects like porosity, voids, and high surface
roughness. With these defects the performance of thermal barrier coating
layers is degraded, therefore laser surface sealing processing must be
introduced to enhance their properties and increase their resistance to the
external effects. The previously published literatures are very little about
the laser surface sealing processing of thermal barrier coatings using solid
lasers. Detailed study has been carried out on the feasibility of using high
power density laser beam in order to optimize the properties of plasma –
sprayed thermal barrier coatings by decreasing the porosity and
improving the surface finish, mechanical, thermal insulation properties,
oxidation, hot corrosion and thermal shock resistance.

Although the postulate of " photon-having-zero-rest-mass " became over the years a sort of " dogma " , routinely repeated in thousands of physics textbooks and scientific articles, great physicists like two " fathers " of Quantum... more

Although the postulate of " photon-having-zero-rest-mass " became over the years a sort of " dogma " , routinely repeated in thousands of physics textbooks and scientific articles, great physicists like two " fathers " of Quantum Mechanics: Erwin Schrödinger and Louis De Broglie, never believed that photons were really " massless " at rest, and many other remarkable physicists challenged this conviction as well. In recent years (2001-2005), the experiments through which Lene Westengarten Hau succeeded in slowing down, stopping, and making restart a laser light pulse by making it pass through optical molasses and ultra-cold sodium vapors of BEC (Bose-Einstein Condensates) can be interpreted as final and persuading evidence that photons –being both particles and e.m. waves-do possess a rest mas and they can be damped in " classical " and quantum ways as damped harmonic oscillators (classical) and superposing waves (QM). Therefore the speed of light is neither an universal constant (c), nor it is " invariant under Lorentz' transformations " , thereby destroying the 2 main pillars of Einstein's SR (Special Relativity). " There must be no barriers to freedom of inquiry. There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. " (J. Robert Oppenheimer)

Alpha spectroscopy is related to the α-decay of nuclei which is described by the Gamow theory and the tunnel effect. These effects are also important for fusion reactions for example in the nucleosynthesis of the chemical elements. One... more

Alpha spectroscopy is related to the α-decay of nuclei which is described by the Gamow theory and the tunnel effect. These effects are also important for fusion reactions for example in the nucleosynthesis of the chemical elements.
One can explore the fine structure of specific α decays. Energy loss of α-particles in matter is used to determine the thickness of foils and thin layers which is an important application of particle spectroscopy.

Helium-Neon or HeNe laser is a type of gas laser, which have many industrial and scientific uses and are often used in laboratory demonstrations of optics. In this experiment, we worked in the basic cavity alignment of a He-Ne laser using... more

Helium-Neon or HeNe laser is a type of gas laser, which have many industrial and scientific uses and are often used in laboratory demonstrations of optics. In this experiment, we worked in the basic cavity alignment of a He-Ne laser using another commercial He-Ne laser. Finally, we went through power and beam profile measurement, longitudinal modes and speed of light measurement of our newly constructed He-Ne laser. The laser operates at 632.8 nm and the maximum output power is 2.6 mW.

In a major step toward developing portable scanners that can rapidly measure molecules in pharmaceuticals or classify tissue in patients' skin, researchers have created an imaging system that uses lasers small and efficient enough to fit... more

In a major step toward developing portable scanners that can rapidly measure molecules in pharmaceuticals or classify tissue in patients' skin, researchers have created an imaging system that uses lasers small and efficient enough to fit on a microchip. [34]
A new study, "Wavelength-encoded laser particles for massively multiplexed cell tagging," by scientists in the Wellman Center for Photomedicine has been published in Nature Photonics. [33]
"This is just a wonderful example of the unexpected ways projects can develop when a team of diverse scientists from around the world come together to try and understand new and interesting phenomena," said team member Jim Cleaves, also of ELSI. [32]

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of... more

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond. Among their many applications, lasers are used in optical disk drives, laser printers, and barcode scanners; DNA sequencing instruments, fiber-optic and free-space optical communication; laser surgery and skin treatments; cutting and welding materials; military and law enforcement devices for marking targets and measuring range and speed; and laser lighting displays in entertainment.

Presented a new type of tunable microlaser emitting two beams. [44] The theory of usual photonics must be revisited for non-Euclidean photonics and I think this new line of work is very exciting, as there is still much to uncover." [43]... more

Presented a new type of tunable microlaser emitting two beams. [44] The theory of usual photonics must be revisited for non-Euclidean photonics and I think this new line of work is very exciting, as there is still much to uncover." [43] As lasers with peaks power ranging from 1 to 10 PW are now in operation and several facilities reaching 100 PW are being planned, there is no doubt that high-intensity physics will progress tremendously in the near future. [42] The electron density in the plasma grating has been proven to be an order of magnitude higher than that in a filament. [41] University of Central Florida researchers have developed a new type of laser beam that doesn't follow long-held principles about how light refracts and travels. [40] Combining a first laser pulse to heat up and "drill" through a plasma, and another to accelerate electrons to incredibly high energies in just tens of centimeters, scientists have nearly doubled the previous record for laser-driven particle acceleration. [39]

This paper reviews the device physics and technology of optoelectronic devices based on semiconductors of the GaN family, operating in the spectral regions from deep UV to Terahertz. Such devices include LEDs, lasers, detectors,... more

This paper reviews the device physics and technology of optoelectronic devices based on semiconductors of the GaN family, operating in the spectral regions from deep UV to Terahertz. Such devices include LEDs, lasers, detectors, electroabsorption modulators and devices based on intersubband transitions in AlGaN quantum wells (QWs). After a brief history of the development of the field, we describe how the unique crystal structure, chemical bonding, and resulting spontaneous and piezoelectric polarizations in heterostructures affect the design, fabrication and performance of devices based on these materials. The heteroepitaxial growth and the formation and role of extended defects are addressed. The role of the chemical bonding in the formation of metallic contacts to this class of materials is also addressed. A detailed discussion is then presented on potential origins of the high performance of blue LEDs and poorer performance of green LEDs (green gap), as well as of the efficiency reduction of both blue and green LEDs at high injection current (efficiency droop). The relatively poor performance of deep-UV LEDs based on AlGaN alloys and methods to address the materials issues responsible are similarly addressed. Other devices whose state-of-the-art performance and materials-related issues are reviewed include violet-blue lasers, 'visible blind' and 'solar blind' detectors based on photoconductive and photovoltaic designs, and electroabsorption modulators based on bulk GaN or GaN/AlGaN QWs. Finally, we describe the basic physics of intersubband transitions in AlGaN QWs, and their applications to near-infrared and terahertz devices.

Scientists at the U.S. Naval Research Laboratory (NRL) discovered a new method to passivate defects in next generation optical materials to improve optical quality and enable the miniaturization of light emitting diodes and other optical... more

Scientists at the U.S. Naval Research Laboratory (NRL) discovered a new method to passivate defects in next generation optical materials to improve optical quality and enable the miniaturization of light emitting diodes and other optical elements. [44]
Printed electronics use standard printing techniques to manufacture electronic devices on different substrates like glass, plastic films, and paper. [43]
A tiny laser comprising an array of nanoscale semiconductor cylinders (see image) has been made by an all-A*STAR team. [42]

The decomposition of ethane (C 2 H 6) and the subsequent conversion to other hydrocarbons are investigated using a Q-switched (Q-SW) Nd:YAG laser induced plasma inside a controlled chamber. The metal targets, including iron, copper,... more

The decomposition of ethane (C 2 H 6) and the subsequent conversion to other hydrocarbons are investigated using a Q-switched (Q-SW) Nd:YAG laser induced plasma inside a controlled chamber. The metal targets, including iron, copper, nickel, and palladium, are employed to assist the plasma formation and ethane decomposition. Fourier transform infrared spectroscopy and gas chromatography are used for identifying and analyzing the products to determine dissociation rates as well. Several C 1 and C 2 components, namely, methane (CH 4), ethylene (C 2 H 4), and acetylene (C 2 H 2), as well as heavier C 3 , C 4 , and C 5 components, such as propane, butane, and pentane, are obtained after ethane decomposition. The yield, selectivity, and conversion ratios of hydrocarbons mainly depend on the metal species as the active catalysts during laser exposure. The most abundant component is found to be ethylene having a selectivity of ∼39% using a palladium target. This technique offers high reproducibility to generate selective and desired hydrocarbon compounds in the controlled chamber.

After the discovery of laser therapy it was realized it has useful application of wound healing and reduce pain, but due to the poor understanding of the mechanism and dose response this technique remained to be controversial for... more

After the discovery of laser therapy it was realized it has useful application of wound healing and reduce pain, but due to the poor understanding of the mechanism and dose response this technique remained to be controversial for therapeutic applications. In order to understand the working and effectiveness different experiments were performed to determine the laser beam effect at the cellular and tissue level. This article discusses the mechanism of beam interaction at tissues and cellular level with different light sources and dosimetry principles for clinical application of low level laser therapy. Different application techniques and methods currently in use for clinical treatment has also been reviewed.

With the achieved 100 kHz high-energy attosecond pulse-train source, many experiments that need both a high repetition rate and enough energy can now be performed in ELI ALPS. The research was published in Ultrafast Science. [17]... more

With the achieved 100 kHz high-energy attosecond pulse-train source, many experiments that need both a high repetition rate and enough energy can now be performed in ELI ALPS. The research was published in Ultrafast Science. [17] Researchers at Institut national de la recherche scientifique (INRS) have discovered a cost-effective way to tune the spectrum of a laser to the infrared, a band of great interest for many laser applications. [16] A team of scientists led by University of Nevada, Reno's Hiroshi Sawada, an associate professor of the Physics Department, demonstrated that numerical modeling accurately reproduces X-ray images using laser-produced X-rays. [15]

Methane decomposition has been extensively investigated using a Q-switched Nd:YAG laser, focused on the metal catalysts including Ni, Fe, Pd, and Cu within the controlled chamber to verify the effect of catalyst, plasma properties, and... more

Methane decomposition has been extensively investigated using a
Q-switched Nd:YAG laser, focused on the metal catalysts including Ni, Fe, Pd, and Cu within the controlled chamber to verify the effect of catalyst, plasma properties, and yield and selectivity of the products. Fourier transform IR spectroscopy (FTIR) and gas chromatography (GC) are employed to support the characterization of the components. This indicates that methane is strongly decomposed within the metal-assisted laser-induced plasma, leading to the subsequent recombination and the production of heavier hydrocarbons. The dominant species, including propane, ethane, and ethylene, have been identified examining different metallic catalysts. The dissociation rate, conversion ratio, selectivity, and yield of products are strongly dependent on the metal target and plasma characteristics.

Solutions to the crisis of planetary extinction cannot be achieved "at the polls". The challenge goes much deeper than democratic selection of political representatives. Solutions require timely "coherent entrainment" of humanitarian... more

Solutions to the crisis of planetary extinction cannot be achieved "at the polls". The challenge goes much deeper than democratic selection of political representatives. Solutions require timely "coherent entrainment" of humanitarian agency with First Cause Intention (FCI) that can be coherently entrained and embodied during the specific time of The Celebration of Human Dignity. The time has finally come when human responsibility must be consciously harmonized (concerted) with Divine Intention. Of course, this has been the ideal of ages, but with new understanding of the quantum-field reality the impossibility of reading "God's Heart-Mind" can be achieved by maintaining electromagnetic Humanitarian Solidarity with the use of the technological media. Increasingly, the teachings of "perfection" have been understood as impossible for humans, but technological maintenance of coherent entrainment is a practical possibility leading to perfectiopn. Both FCI and responsible human agency can be addressed from quantum dimensions of electromagnetic (EM) tension that is usually rationalized and misunderstood in the human brain as God's "error". However, tension/error are requisite to "learning" and-therefore-to "evolution". It may be stipulated that the current stage of human development requires transcendence of misdirection by "brain" creativity in favor of "heartmind" imaginational creativity, and such transcendence occurs at quantum scales of technological frequency. Today, an unprecedented imaginational seeding methodology exists as the "coherent entrainment" (CE) or "frequency locking" of First Cause Purpose and human purpose which is akin to Jungian "synchronicity" as the "frequency" of "meaningful discovery". CE is the measurable EM signature of First Cause Intention which-if appreciated as heartmind frequencies-can be used to guide human agency with Communication & Information Technology (CIT).