Search

In the past decade, the research on optical frequency comb and its applications has achieved rapid development, bringing revolutionary progress to the metrology field. Frequency stabilization and absolute frequency measurement of the CW laser through optical frequency combs is very important for establishing new length standards. A tunable near-infrared CW laser is phase locked to a commercial optical frequency comb referring to a Rubidium atomic clock for frequency stabilization. A home-made comb is phase locked to a hydrogen maser for measuring the absolute frequency of the frequency stabilized CW laser obtained. The procedure of frequency stabilization and absolute frequency measurement based on optical frequency combs is demonstrated and the uncertainty and stability of the frequency stabilized CW laser are estimated.

We investigated cw intra-cavity third-harmonic generation (THG), where both the second- and third-harmonic NLO processes are type-I. The concept and results from a prototype with output of 28mW at 307nm are presented here.

We present preliminary results showing the potential of VECSEL technology for the generation of high power coherent supercontinuum. Among these results, we demonstrate a stable output power of 16 W with a pulse duration of 71 fs and a repetition rate of 1.7 GHz from a VECSEL oscillator and Ytterbium fiber amplifier. This system was used to generate a coherent supercontinuum averaging 3 W of power using a highly nonlinear photonic crystal fiber. In addition, we discuss the possible methods for the detection and stabilization of the carrier offset frequency. The beatnote between a VECSEL seeded supercontinuum and an external CW laser reveals a relatively stable signal, well above the detection noise. A discussion about system design considerations for noise reduction and increased offset frequency stability is also included.

The thermo-optic properties of CdSe/ZnS quantum dots (QDs) are investigated in this paper. Two CdSe/ZnS QDs-doped samples are fabricated and the closed aperture Z-scan data were obtained by a single-beam Z-scan setup with a continuous laser as the exciting source. With the measured curves the coefficient of nonlinear refractive index n2 (caused by thermal effect) and the thermo-optic coefficient were achieved. CdSe/ZnS QDs-doped materials show larger thermooptic coefficients than the glass materials by 2 orders of magnitude.

We report on the nonlinear effects of light propagation through a fluorescent nanocolloid, where self-collimated beams are formed. The medium is constituted by a bidisperse suspension of fluorescent and nonfluorescent nanospheres of similar diameters (60nm and 62nm, respectively) in distilled water. A CW laser beam (532 nm wavelength) was focused into the nano-suspension. The threshold power and focusing conditions to create a self-collimated beam are analyzed as a function of the incident power, and a hysteresis effect is observed for the size of the output beam when the power is increasing and decreasing. We also discuss other effects associated to the presence of the fluorescent nanospheres.

Type-II light sources on InP substrate are an innovative concept for wavelengths ranging from 2 μm to the mid-IR. The concept is using the type-II band alignment between GaInAs and GaAsSb to exceed the limitation of type-I devices. Since the first demonstration of InP type-II heterostructure lasers above 2.3 μm in 2012, we have extended the emission wavelength to 2.7 μm. Furthermore, a drastic reduction in threshold current density down to 104 A/cm2 per QW at infinite length was achieved (at 2.5 μm), which represents an improvement by more than a factor of two. Additionally CW operation up to 30°C and up to 80°C pulsed is presented. Furthermore, LEDs for 3.5μm peak emission wavelength and up to 86 μW output power are shown.

We present and discuss a set of experiments based on the application of the nonlinear properties of colloidal nanosuspensions to induce waveguides with a high‐power CW laser beam (wavelength 532nm) and its use for controlling an additional probe beam. The probe is a CW laser of a different wavelength (632nm), whose power is well below the critical value to induce nonlinear effects in the colloidal medium. We also discuss a technique for the characterization of the induced waveguides.

Damage mechanisms in thin films are reviewed from femtosecond pulse to CW laser illumination. Special emphasis is given to the role of native and laser induced defects, recent successes and the need for better diagnostic tools.

A growing problem for the Police and Security Forces has been to prevent potentially hostile individuals to pass a checkpoint, without using lethatl violence. Therefore the question has been if there is a laser or any other strong light source that could be used as a warning and dazzling device, without lethal or long term effects. To investigate the possibilities a field trial has been performed at a motor-racing track. A green CW laser with an irradiance on the eye of maximum 0.5 MPE, as defined by ICNIRP [1] and the ANZI standard [2], was used as a dazzle source. Ten drivers have been driving with dipped headlights through a course of three lines with orange cones. In every line there has been only one gate wide enough to pass without hitting the cones. The time through the course, the choice of gates and the number of cones hit have been measured. For every second trial drive through the track, the driver was exposed to the laser dazzler. The background illuminances ranged from a thousand lux in daylight to about ten millilux in darkness. The protective effect of the sun-visor of the car was investigated. The drives visual system was carefully examined before and after experimental driving and a few weeks after the experimental driving to verify that no pathological effects, that could potentially be induced by the laser exposure, pre-existed or occurred after the laser exposure. An analysis of variance for a within subjects design has been used for evaluation. It was found that green laser light can have an obvious warning effect in daylight. Dazzling does reduce the drivers ability to make judgments and manouver the car in twilight and darkness. A sun-visor can reduce the glare and give the driver an improved control, but that perception can be unjustified. No damage to the visual system was observed.

In-vivo skin photo-bleaching (intensity decrease during irradiation) has been investigated at 405 nm cw laser excitation. Digital RGB photo-camera was used for studies of the bleaching features by analysis of fluorescent images at separated R, G and B spectral bands. Diagnostic potential based on correlations between skin pigmentation and bleaching rates is discussed.

The aim of this work is to use non-destructive optical measurement techniques for defect detection. This paper presents the application of electronic shearography speckle pattern interferometry (ESSPI) to detect visible and invisible on the surface defects of a pine wood specimen The different artificial defects were created under the pine wood surface to simulate "defected" samples. The ESSPI set-up based on a He-Ne CW laser has been developed and used for studying the possible locations, sizes and shapes of wood defects. The results were real time and well agreed with the actual defects. Therefore the present method is feasible.

We demonstrate high-efficient CW thin disk 15%Tm:KYW laser pumped by a 20W CW laser diode bar at 803nm. Three 15%Tm:KYW b-cut disks of 200, 250 and 300mm thickness are tested, with the maximal laser output being of 4.9W at ~1.9mm. Slope and optical-to-optical conversion efficiencies are reported as well.

The data represent life time test of a CW diode running in pulsed regime. It is shown that the reliability of CW laser diode run with 10 times higher peak currents is enough for many applications, where high peak power, high repetition rate diodes are a better choice than DPSS lasers.

The market offers a relatively wide range of laser power meters for high power applications, but when it comes to verifying measurements, a lot of know-how is required. Even the comparison of national standards between different countries in some cases has given evidence for discrepancies. For high power measurements, a major drawback has been that the primary standards of all the national calibration institutes are cryogenic radiometers, which are built for low power applications, while industrial applications often require lasers in the 0.1 - 12 kW range, thus creating the need for transfer standards from low to high power range. Primes GmbH currently is setting up a calibration laboratory for high power cw laser power meters in cooperation with the German institute for standards, the PTB, which will allow to trace high power laser measurements back to national standards and extend the measurement range substantially. Certified calibration services will be open to all users and manufacturers of laser power meters for high power applications.

The communication of humans with their surrouding is achieved through their senses and the related organs. Visual communication using the eyes is made possible because the various sources of light, natural i.e. the sun or the lightning, or artificial such as Lasers, emit electromagnetic radiation which is either reflected or scattered by surfaces. This radiation received by eyes is processed in the brain where the images of the environment are developed. The luminous processing can be either macro- or microscopic. The macroscopic processing is the result of light coming from the sun or from wide range lamps, while the microscopic results from light coming from wide range lamps, mercury lamps, lasers or electron beam. The microscopic processing is the subject we are dealing with in this presentation.

The interactive effects of aided cutting gases on CO2 TEMOO CW laser cutting of silicon steel sheet are studied. The qualitative analysis of the formation and elimination of the sinter is discussed.

In this report, polycrystalline Yb:Y 2O3 ceramic laser has been demonstrated for the first time. With a pump power of 11 W at 937 nm, 0.75 W cw laser output at 1078 nm was obtained. The laser had a threshold of 4.7 W and a slope efficiency of 12.6% when an output coupler of R = 98% was used.

Highly efficient Nd:YAG ceramic laser at 1064 nm was demonstrated. Using 1 W LD end-pumping scheme, with 883 mW pumping, 499 mW 1064 nm CW laser output has been obtained corresponding to an optical to optical efficiency of 56.5%. High power CW Nd :YAG ceramic rod laser was also demonstrated. The maximum output power of 62.5 W with was obtained at 1064 nm. The optical to optical conversion efficiency is 21.6%.

Highly efficient Nd:YAG ceramic laser at 1064 nm was demonstrated. Using 1 W LD end-pumping scheme, with 883 mW pumping, 499 mW 1064 nm CW laser output has been obtained corresponding to an optical to optical efficiency of 56.5%. High power CW Nd:YAG ceramic rod laser was also demonstrated for the first time. The maximum output power of 3 1 W with 1 8.8% slope efficiency was obtained at 1064 nm. The potential of Nd:YAG ceramic laser was also discussed.

Typical scheme of cw laser diode driver proposed by Toshiba has been studied. A response of the driver to a strong impulse interference has been determined.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have developed an efficient room-temperature 20at%Yb:YAG thin chip (6 X 6 X 0.5 mm) laser operating at 1.053 micrometers pumped by Ti:Sapphire laser operating at 940 nm. 356 mW of CW output power was obtained for an absorbed pump power of 784 mW. The slope efficiency was 69%, and extrapolated threshold power is 273 mW.

We attach micro-cylindrical lenses with D/f' equals 4/3 to 300 W Q-CW LD array, pre-compressing the divergent angle in fast-axis plane from 40 degree(s) to 9.6 degree(s). Then we use lens duct as optical coupler in LD array end-pumped Nd:YAG laser. The transfer efficiency is 90%, and well convergent effect is also obtained near the output face of lens duct. At last, we get 37.9% light-light conversion efficiency of 1.06 micrometers light at 1% duty factor, and the output beam is good.

New laser-based technique for anatomical-functional study of the medial prefrontal cortex (MPFC) of the brain of experimental animals (rats) is presented. The technique is based on making accurate well-controlled lesions to small MPFC and subsequent observing behavioral alterations in the lesioned animals relative to control ones. Laser produces smaller and more accurate lesions in comparison to those obtained by traditional methods, such as: mechanical action, chemical means, and electrical currents. For producing the brain lesions, a 10 W CO2 CW laser is employed for reasons of its sufficiently high power, which is combined with relatively low cost-per-Watt ratio. In our experience, such power rating is sufficient for making MPFC lesions. The laser radiation is applied in a form of pulse series via hollow circular metallic waveguide made of stainless steel. The waveguide is of inner diameter 1.3 mm and 95 mm long. The anesthetized animals are placed in stereotaxic instrument. Via perforations made in the skull bone, the MPFC is exposed to the laser radiation. Several weeks later (after animal recuperation), standard behavioral tests are performed. They reveal behavioral changes, which point to a damage of some small regions of the MPFC. These results correlate with the histological data, which reveal the existence of small and accurate MPFC lesions. The present technique has good prospects for use in anatomical- functional studies of brain by areas. In addition, this technique appears to have considerable promise as a treatment method for some pathologies, e.g. the Parkinson's disease.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The processes governing the operation of both the pulsed COIL with a forced homogeneous generation of atomic iodine and the premixed I 2 -dissociated continuous-wave laser are identical. It makes it possible to use a pulsed laser with a low chlorine flowrate to simulate the high power CW operation and to predict its performance. The examples of such predictions made for famous CW laser systems 'RADICL' and 'RotoCOIL1' are presented and discussed. Experimental results on application of AOM for generation of a train of microsecond pulses are also presented.

NASA's Goddard Space Flight Center is developing technology for satellite-based, high peak power, LIDAR transmitters requiring 3-5 years of reliable operation. Semi-conductor laser diodes provide high efficiency pumping of solid state lasers with the promise of long-lived, reliable operation. 100-watt quasi- CW laser diode bars have been baselined for the next generation laser altimeters. Multi-billion shot lifetimes are required. The authors have monitored the performance of several diodes for billions of shots and investigated operational modes for improving diode lifetime.

A CW Tm:YAG laser with a tuning range from 1.86 to 2.08 micrometers was used to create thermal lesions on chicken breast, calf liver, and porcine cornea. All tissue types were exposed to a constant irradiance (450 mW, 0.92 mm spot diameter, 0.5 and 1.0 second exposures) at five different wavelengths about the 2 micrometers water absorption peak. We estimated tissue absorption coefficients from the thermal history recorded by a 8 - 12 micrometers thermal camera. Our data confirmed that the absorption of all tissue types tested followed the water absorption curve. The effect of these differences in absorption upon the coagulation lesion size was evaluated by histologic measurements.

We propose a new technique of AHI which combines the high speed operation advantages of dynamic holographic interferometry and a real- time, high resolution, high stability, Denisyuk's holograms. Based on a new high sensitive phototerfractive reversible crystals group 23 doped (P and Cu) a small power CW laser was used for continuously hologram read and read-out processing. Portable wariant of a small size AHI sensor and practical demonstration of this technique are described.

Electro-optic polymer waveguide modulators may be used in parallel modulation arrays supplied by branching structures providing fanout from a CW laser for a variety of applications, including CATV and data communications. This paper highlights some of the benefits of using EO polymer modulators in arrays for point-to-point digital data communications.

We have presented the experiments about the cineholography constructed with the many element holograms which were made with cw laser and holographic-TV using LD LCD and holography camera. The interference fringes with holography camera were recorded on the CCD of TV-camera. The fringe signals were transferred into electronic ones. And transformed into the LCD, the fringes were constructed on the one. At this time, with the help of LD, the panel of LCD were illuminated and so hologram was reconstructed in the LCD at real time.

Characteristics of 'melting dendrites' resulting in a NaCl volume from combined heating by furnace and CW laser irradiation are studied. The dendrite growth velocity, tip curvature radius, and side branches period are connected by the relations typical for crystallization dendrites. In spite of coincidence of 'liquid' dendrites growth direction and easy glide direction , no relation of their parameters with processes of plastic deformation of ambient crystal is discovered.

We report on the recent development and initial test results of two electro-optic polymer based integrated optic devices for optical interconnection applications. The first is an optical railtap for the distribution of many different optical signals from a single CW laser diode, and the second is a traveling wave Mach-Zehnder integrated optic modulator, which was modulated at frequencies up to 8 GHz. Electro-optic polymer materials supplied by Akzo Research, By, were used in both devices.

In the paper the idea and the practical development of thick film hybrid driver - controller microcircuit for typical CW laser are described. The microcircuit was developed in the Institute of Electronics to meet typical requirements for universal, pulse or analogue CW laser application. Schematic diagrams and results measured of analogue mode frequnoy characteristics and pulse response of the circuit are presented. To sum up some practical conclusions are drawn and a possible field of application of the microcircuit is considered

The effect of low power laser radiation from a He-Ne CW laser on middle ear inflammatory otitis is discussed.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper reports on experimental results of the photosensitized mechanism of HPD in cancer therapy. Human stomach cancer cells and Hela cells were chosen as the object of study. Two kinds of HPD were used being irradiated by either pulsed or CW laser light. The results showed that the main mechanism in photosensitized cancer therapy was singlet oxygen. The energy levels of HPD and HP were calculated and the photodynamic reaction process as well as it's corresponding physical model were discussed.

The processes occuring due to high-pulse-repetition rate laser beam interaction with metals have been studied by now very poorly both theoretically and experimentally. In the same time, first high repetition rate (HRR) pulsed laser applications to materials processing attract some interest to such a study. The investigation of possible improvement, theof the cw-laser-induced processes by using cw and HR R lasers together is also prospective. The melt removal mechanisms studied both theoretically and experimentally are the subject of the present paper. The pulse approximation of hydrodynamical equations is valid to describe the molten metal motion generated by laser puls of 1-100 μs duration. Reasonable agreement between theoretical estimations of velocity and escape time of the melt and experimental data was achieved. High-repetition rate pulsed processing was also investigated. The model of deep penetration by a HRR laser is put forward. It explaines the greater penetration ability of a HRR laser as compared to the cw laser of the same output power.

Employing a tuff rock cave as the vibration isolation system made possible the measurement of the vibration mode of large-sized structure such as a fully equipped automotive bodies and producing 2 m by 1 m hologram for display.

Important developments in gas laser technology have arisen in the past year or so. These developments include improvements in the performance of existing systems and the achievement of laser action in new systems. In the former category we would mention the construc-tion of compact CO2 lasers with power outputs previously achieved only in very large devices and the commercial exploitation of CW ultraviolet laser outputs in noble gas ion lasers. New systems would include CW laser action in metal vapors in a buffer discharge of helium and CW laser action in pure helium itself.© (1969) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.