Preparation of chicken embryo allantoic fluids for animal health requires opening the eggshell by cutting, drilling or punching methods. Laser cutting and drilling is used as an alternative to known processes. Both CO.sub.2 and Nd:YAG lasers are employed. A focused CO.sub.2laserbeam at a power of 200 watts in conjunction with an X-Y motion table produced 25 mm diameter "clean-cuts" in eggshells with a cutting time of 0.5 seconds per egg. The material removal mechanism was vaporization. When an axicon/lens combination is used with a CO.sub.2laser, the cutting time was further reduced to 0.2 seconds per egg and the mechanism of material removal is changed from vaporization to decomposition of the eggshell into fine powders. Small holes, typical diameters of 0.5 mm to 1 mm are generated in the eggshell using the pulsed Nd:YAG laser.
Experiment A schematic of the experiment is shown in Fig. 7.2.1 (also see Fig. 7.4.1 for details). The set-up is similar to that discussed in Chapter 6. All experiments are performed at room temperature in a water-filled, closed, 25 μm deep microfluidic chamber. An anti-reflection (AR) coating is applied to the bottom glass-water interface of the chamber. Each polystyrene microsphere is optically trapped by an expanded 660 nm beam from a CW laserfocused through a high numerical aperture (NA=1.2) water-immersion objective. The vertical position of the focus, and consequently the height of the trapped bead, is adjusted using a piezo. In addition to the trap beam, which enters the chamber from above, two lasers, both p-polarized, are incident from below at greater than critical angle (θ c =61 ◦ ): a low power ( < 1mW), 637 nm beam acts as the probe for
The high precision of energy calibration acquired by BEMS is based on Compton backscattering principle. The working scheme of this system can be depict briefly as follows : firstly, a laser source provides a laserbeam, and an optics system focuses the laserbeam and guides it to make head-on collisions with the electron (or positron) beam in the vacuum pipe, where the Compton backscattering process happens; after that, the backscattering high energy photon will be detected by a High Purity Germa- nium (HPGe) detector. More engineering details can be found in Ref. . In fact, many advanced techniques and precise instruments are employed to achieve such a highly accurate measurement of beam energy. The whole system can be sub-divided into four parts according to their technique and engineering characters: 1) laser source and optics system, which supplies low energy laser and focused photons; 2) laser to va- cuum insertion system, where a laserbeam collides with electron or positron beam; 3) HPGe detector to measure backscattering high energy photons; 4) data acquisition and running control system for information processing and analyzing. The layout schemat- ic of the system is shown in Figure 2.
transformed into heat. As the local temperature is increased, different changes occur, and thermal effects appear on the skin. These effects are depe- nded not only on the temperature but also on the exposure time (Song, 2017). In fact, the absor- ption of laser lights in the tissue is the usual desi- rable effect and it is the beneficial aim for laser therapy. The absorbed energy depends on the wavelength of laserbeam. In human body, there are several of light absorbers which are called chromophores (Azadgoli, 2016, Gandikota et al., 2017). Each one of them can absorb specific wav- elength as in Table 1. Furthermore, CO2 laser and Er: YAG laser have higher water absorption com- pared to other lasers. Because of that, most of the absorbed energy vanishes during the treatment due to the vaporization process. That is the reason why the treatments by those lasers have less heat transfer to surrounding area and deeper cells. That means, the therapy by laser does not have side effects and without long-standing implication on the skin as in figures 1B and 5B.
The studies of confined micro-explosion during the last decade revealed the major features of this complicated phenomenon where the processes of electro-magnetic field/dielectric interaction, plasma formation and high-pressure hydrodynamics are intertwined. The concise description of these processes is as the following. The tight focusing of the laserbeam deep inside a transparent crystal allows achieving the absorbed energy density in excess the strength of any material in a sub-micron volume surrounded by the pristine solid. After energy transfer from hot electrons to ions the expanding strong shock wave accompanied by the rarefaction wave starts propagating outside of this volume. After the shock decelerating and stopping the void, surrounded by shell of compressed and pressure modified material converted to the novel phases, is formed. All transformed material remains confined inside the bulk of undamaged material ready for the further studies. These studies employed the short intense laserbeam with the Gaussian spatial and temporal intensity profile [1–4]. The short intense laserbeam with the Gaussian spatial and temporal intensity profile tightly focussed inside a transparent crystal generates the energy density of several MJ/cm 3 . The pressure produced is in excess of a few TPa which is higher than the strength of any existing material (diamond has the highest Young modulus of 1 TPa = 1 MJ/cm 3 ). The laser pulse, 150 fs, 100-200 nJ, 800 nm, tightly focussed inside sapphire with microscope lens (N A = 1.4) creates the solid density plasma at the temperature of a few tens electron Volts ( ∼ 5 × 10 5 K) with the record-high heating rate of 10 18 K/s [1,2]. It was found that the novel (previously unobserved) high-pressure phases of Aluminium and Silicon were formed [3,4] following the ultrashort laser-induced confined microexplosion. Pressure/temperature conditions created in the micro-explosion are similar to those
The characterization of beam modulation by acousto-optic mode locker is reported. HeNe laser was employed as a source. Acousto-optic mode locker (AOML) was used to convert the continuous beam to become pulsed. Radio frequency signal provided an acoustic source to the AOML. The signal was amplified using a power amplifier. A pulse generator was utilized to regulate the frequency of the signal. The frequency and the power of the amplifier were varied to characterize the modulated beam. The HeNe laserbeam was modulated into a periodic signal. The pulse width of the modulated signal was found to increase linearly with the RF pulse width. The modulated signal intensity was also found to vary linearly with RF drive power.
ear representation of the uncertainty region of the deflection. Previous work  showed that when the size of the asteroid is in the range of 100 m, the applied strategy in  cannot deliver the necessary torque to control the rotation in order to yield higher thrust and, as a consequence, also the desired deflection. For this reason, we considered two different deflection strategies based on the laser pointing. In the first case the laserbeam is pointed such that the resulting thrust on the asteroid will be directed as much as possible in a suitable direction. In the second case we consider a fixed laser pointing to simplify deflecting operations. Moreover, in the first case the targeting locations on the surface of the asteroid are decided in real time using the combination of information provided by a precise model of asteroid shape and the laser-matter interaction, since the laser thrust tends to align with the local normal. The second strategy is less operationally demanding in this respect because no need for pointing mechanisms or continuous adjustment of the spacecraft attitude is required. For this reason we wanted also to assess if it is possible for a fixed focusing laser to carry on a deflection mission. In fact the area of the impinging spot tend to change as the surface of the asteroid moves back and forth with the rotation. This means that hundreds of thousands of actuations would be required during the mission. Eventually the paper will demonstrate the ability of our system to deflect the selected target by one Earth radius or more for different asteroid-spacecraft configurations with actual radar-shape models scaled down to the considered mean size.
near their ionization threshold with R2PI thus avoiding dissociative ionization. For such compounds, fragment free mass spectra can be obtained. Moreover, under these conditions, molecular oxygen, molecular nitrogen, carbon dioxide, alkanes, alkenes, and aliphatic aldehydes are almost not ionized and thus background noise is significantly reduced (Zimmermann et al., 1997). This allows very low detection limits (DL) for aromatic compounds. A series of semi-volatile polycyclic aromatic hydrocarbons (HC) was studied in gas phase in order to determine the SPLAM molecular DL. Typically, when about 100 mass spectra are averaged, a few hundreds of molecules are needed inside the ionization volume to give an appreciable mass signal. For single shot mass spectra, a few thousand molecules are needed (Gaie-Levrel, 2009). These numbers can be used to estimate the capabilities of SPLAM in the case of aerosol particles. For gaseous 2-methylnaphthalene, for example, the TOF-MS is able to detect 1.6 × 10 5 molecules in its ionization volume yielding a weight DL of 0.85 attogram (excimer laser power density ≈ 2 × 10 6 W cm −2 ) by taking into account that a signal is detectable when the signal to noise ratio is higher than 3. Supposing a homogeneous d = 200 nm particle composed of a M = 150 g mol −1 compound and a 1 g cm −3 density, a particle weight of 4 fg can be calculated (∼2 × 10 7 molecules). In principle, our TOF-MS has thus the ability to detect 2-methylnaphthalene with a 0.02 % weight fraction inside this particle. However, since the DL is estimated from gas phase R2PI, the estimation for the particle case holds only for complete particle vaporization and for an optimal spatial and time overlap between the ionization volume and the gas plume of the vaporized particle. Furthermore, a higher power density is needed for the LDI process. Hence, R2PI is difficult to achieve in these conditions and the estimation given above is most probably a lower limit for detection limit.
impact on difference in product selectivity probably accrediting to formation of different calcium oxide species. The calcium oxide can occur in amorphous form or fine particles dispersed well enough in the catalysts owning to no detection of X- ray diffraction. The thermal stability of calcium oxide species in Cu/ZrO 2 _CaO650 was up to 600 o C according to thermal degradation results in Fig. 1(C), while the less
Figure 2 Linear polarized PL emission with SAW oﬀ/SAW on. Polarized PL with spatial resolution excited by a tightly focusedlaserbeam close to the nanowire edge facing the acoustic transducer (position G, cf. diagrams on the left side). (a) In the absence of a SAW, the emission is restricted to the region close to the excitation spot and is polarized perpendicular to the nanowire axis. (b) Application of acoustic power of 12 dBm induces the transport of electrons and holes to a remote position R, where they recombine emitting light polarized mainly parallel to the nanowire axis. Spatial PL intensities along the nanowire axis integrated from 796.6 nm to 823.3 nm for the emission polarized perpendicular (blue circles) and parallel (red triangles) to the nanowire axis in the absence (c) (open symbols) and presence (d) (ﬁlled symbols) of a SAW.
The graphs shows (years 2005–2007) where the lasers are produced units, where the laser systems are produced revenues and last one is laser cutting systems distribution. Those years has laser biggest potential in Europe and North America. The global market of laser processing is expected to grow to $17.36 billion by 2020 from its 2013 market size of $11.24 billion, at an estimated CAGR of 6.18 % between 2014 and 2020. Fig. 2Laser cutting systems distribution.The report entails the market analysis and forecasts related to the laser processing market. This report deals with the driving factors, restraints, and opportunities for the global laser processing market, which are helpful in identifying industry trends and key success factors in this industry. Moreover, it also profi les the major companies that are active inthe fi eld of laser processing along with their product off erings, strategy, fi nancial details, developments, and competitive landscape. Some of the key players are Coherent, Inc. (U.S.), Epilog Laser (U.S.), Rofi n-Sinar technologies (U.S.), Newport Corporation (U.S.), Laserstar technologies corporation (U.S.), and IPG Photonics Corporation (U.S.). The analysis of the global laser processing market is done with a special focus on the high growth applications in each vertical and the fast growing application market segment, along with, highlighting the winning imperatives and burning issues pertaining to this market (CUTLASERCUT, 2015). Diff erent laser technologies such as CO2laser,
RESULTS: In 14/35 patients, there was a recurrence between 1 and 43 months (mean 18.7 months), the annual recurrence rate being approximately 8%. In three of these patients, malignant transformation occurred at a later stage. In two other patients, a malig- nancy occurred without a prior recurrence. In alto- gether 5 of 35 patients, malignant transformation occurred in a mean period of 54 months, the annual malignant transformation rate being approximately 3%. CONCLUSIONS: The results in the present study are worse than those reported in the literature, perhaps owing to the use of different diagnostic criteria for OL, differences in the employed laser technique and assess- ment of possible recurrences by an independent clinician. Oral Diseases (2013) 19, 212--216
SenTec continues to support Dr Seidman ’ s research with monitors, disposables and technical support. She is on their clinical advisory board for which she receives no monetary compensation. Dr Peggy Seidman reports non- ﬁ nancial support from SenTec, during the conduct of the study; non- ﬁ nancial support from SenTec outside the sub- mitted work. The authors report no other con ﬂ icts of interest in this work.
In this article, we show a novel ultrafast all-optical plasma- based modulator that can directly modulate the spectrum of intense laser pulses to an extreme broad bandwidth, with a modulation speed of tens of THz and a damage threshold of 10 16 W cm 2 level. Because of the ultrafast modulation speed and ultrahigh damage threshold, the plasma optical modulator opens a way to efﬁciently modulate laser pulses in the high- intensity regime. Such highly modulated intense laser pulses may bring a few new physics and applications associated with intense laser–matter interactions. For example, it may be used to produce strong THz radiation via optical rectiﬁcation as the laser pulses have bandwidth in the THz range 32 . Another possibility is to produce ultrabright X-ray sources via laser interaction with atoms 33 , since the modulated spectrum by our plasma modulator can be well extended to the mid-infrared regime 34 . The deeply modulated laser pulse exhibits ultrabroad bandwidth, which can suppress the growth rate of the stimulated Raman scattering instability, highly important for laser fusions 35,36 .
Abstract. Micro milling of super alloy materials such as nickel based alloys such as Inconel 718 is challenging due to the excellent of its mechanical properties. Therefore, new techniques have been suggested to enhance the machinability of nickel based alloys by pre- heating the workpiece’s surface to reduce its strength and ductility. The prediction of fluctuated temperature distribution generated by pulsed wave laser in laser assisted micro milling (LAMM) is crucial. The selection of processing parameter by minimize the effect on the processing characteristic is decisive to ensure the machining quality is high. Determining the effect of heat generated in underneath surface is important to make sure that the cutting tools are able to cut the material with maximum depth of cut and minimum defects in terms of tool wear and tool life. In this study the simulation was carried by using Ansys APDL. In order to confirm the actual and distribution irradiation of temperature from simulation, an experimental was done to validate the results. The experiment was conducted by using Nd:YAG laser with wavelength 1064 nm.
Figure 12 shows the influence of writing beam power on the grating formation process. In the case of MB2I (Fig. 12.a) for low powers, diffracted beam intensity rises and then saturated but for higher intensities, it increases, reachs to a maximum and then drops to some constant value. We think that the relaxation of diffracted beam intensity can be due to the reorientation of azo group or deformation of SRG . Typically Fig. 12.b shows the influence of writing beam power for the other materials that used in this study (for example MB3I). The results show that by increasing the power of writing beam, the rate of growth is increased (Fig. 12.a-b). Figure 13 shows the typical AFM image of self-induced SRGs, the pitch of grating is around 800 nm
Upon applying a laser to the substrate surface, the laser heat will evaporate the material and generate a shallow groove, which is the laser evaporation region, about 80 mm deep. The adjacent material of this groove bottom is melted but not evaporated. After the passage of the laserbeam, the rapid solidification and subsequent solid-state cooling take place. The columnar grain grows from a separate nucleus in the interface of molten layer and solid region, staying parallel to the temperature gradient direction. At the instant of solidification, the main crack is formed at the columnar grain boundary along the direction of thickness. There are minor cracks generated at the cross section and on the top surface. The depth of the crack is equal to the columnar grain length. The nearest neighbor to the columnar grain region is the intergranular fracture region. This region is subjected to the high temperature but has not reached the melting point. The strength of grain bonding is reduced for the high temperature and anisotropic thermal deformation, so that the cracks will extend along the grain boundary. The final region is transgranular fracture region, which is the largest part of the breaking surface.
The laser chemical machining is a non-conventional substractive processing method. It is based on the laser-activation of a material dissolution of metals in electrolyte ambient via local-induced temperature gradients and allows a gentle and smooth processing of especially temperature-sensitive metals. However, the material removal is characterized by a narrow process window and is restricted by occurring disturbances, which are supposed to be related to the localized electrolyte boiling. In order to control the removal quality and avoid disturbances, the correlation between the laser-induced temperatures and the resulting removal geometry has to be better understood. In this work an analytical modeling of the laser-induced temperatures at the surface of ti- tanium based on a Green-function approach is presented. The main influen- cing factors (laser, electrolyte, material) as well as possible heat transfer into the electrolyte are included and discussed. To verify the calculated tempera- tures, single spot experiments are performed and characterized for titanium in phosphoric acid solution within laser irradiation of 1 s. The correlation between the temperature distribution and the resulting removal geometry is investi- gated based on a spatial superposition. Thereby, the bottom limit temperature is found to range between 63˚C and 70˚C whereas the upper limit is related to the nucleate boiling regime. Based on the performed correlation an indicator is identified to predict the ruling removal regime and thereby to reduce the ex- perimental expenditure.