Kouki Shimizu

New emission of CuCl2 in chemically produced O2(1Δ) flow

Abstract Visible and near-infrared emission spectra were observed by injecting copper chloride vapor into a flow of chemically produced O 2 ( 1 Δ). The spectra were found to be identical with those observed previously with heated copper in the O 2 ( 1 Δ) flow including chlorine. The spectra have been assigned to those of CuCl 2 . The results suggest that the excitation of CuCl 2 is due to energy transfer from singlet oxygen.

A Continuously Tunable Organic Solid-State Laser Based on a Flexible Distributed-Feedback Resonator

We describe a continuously tunable organic solid-state laser based on a flexible distributed-feedback (DFB) resonator. The tunable laser is made up of three organic layers. The active layer is a thin film of PVK (poly(9-vinylcarbazole)) doped with Bis-MSB (p-bis(o-methylstyryl)-benzene), the grating layer is a thin film of PVA (poly(vinylalcohol)), and the base substrate is a plate of PDMS (poly(dimethylsiloxane)). The active layer is pumped by the third harmonics of a Nd:YAG laser. The wavelength of laser oscillation is continuously tunable; an electrically controlled mechanical stage simply adjusts the period of the grating. The maximum range of tuning is approximately 4 nm.

Efficient room-temperature CO laser with high specific output.

Efficient room-temperature operation of a fast-axial-flow rf-discharge-excited CO laser is described. A steady-state laser output of 268 W has been obtained with a CO/N(2)/He/Xe/O(2) mixture from a 19-mm-diameter, 300-mm-long discharge. The corresponding electrical conversion efficiency and the specific laser output are as high as 13.5% and 3.15 W/cm(3), respectively. The role of Xe in the mixtures is discussed. The specific laser output achieved is comparable with those of the high-power industrial CO(2) lasers in which a similar excitation scheme is applied.

Observation of High Laser Gain at 703 nm in a New Chemical System

Visible stimulated emission has been observed in a chemically produced O4* complex system. A maximum positive gain of 2.8% has been measured at 703 nm. Experimental results imply high possibility that a visible chemical laser might be realized by the present system.

Room-Temperature Operation of Fast-Axial-Flow Radio-Frequency-Discharge-Excited CO Laser

Room-temperature operation of a fast-axial-flow radio-frequency-discharge-excited CO laser is described. With a Xe-free N2-rich mixture ( CO/N2/He/O2=11.5/26.4/62.1/0.23), steady-state laser output of 163 W has been obtained from a 1.9-cm-diameter, 30-cm-long discharge at an entrance gas temperature of 289 K. The corresponding electrical conversion efficiency is 8.2%. The temperature dependence of output has also been measured in the range of 289–313 K, which gives a change of 0.94 W/K or 0.011 W/K per cm3 of discharge volume.

Applying the self-mixing effect of a microchip laser to optical CT

The self-mixing effect of a microchip laser is applicable to optical CT (Computed Tomography) because of high sensitivity to weak light of the effect. Two acousto-optic modulators were used to frequency-shift the output beam from a microchip laser by several megahertz. The beam was attenuated by passing it through a scattering object and then re-injected into the microchip lasers cavity. The self-mixing effect modulated the output intensity of the laser at a frequency of several megahertz, and the intensity of modulation was measured by a spectrum analyzer. With a ring-type optical path, which is considered to be adequate for optical CT because the light only passes through the object once, it was possible to detect a beam attenuated by more than -90 dB by neutral density filters (ND filters), and to detect a beam attenuated by INTRALIPID-10 percent solution with a concentration of 28 percent, which has the same scattering-absorption characteristic as biological tissue. By Adjusting the frequency-shift towards the relaxation-oscillation frequency of the microchip laser increased the thickness of INTRALIPID-10 percent through which transmission was possible by a factor of two. Imaging through a scattering object by using this method was demonstrated.

1-KW, ROOM-TEMPERATURE, FAST-AXIAL-FLOW CO LASER EXCITED BY A RADIO-FREQUENCY DISCHARGE

A fast-axial-flow rf-discharge-excited CO laser has been scaled up to produce an output power of more than 1 kW at room temperature (280-290 K). The discharge section is composed of eight discharge tubes, to which rf power is capacitively coupled. An output power of 1220 W is obtained with an Xe-added mixture, with corresponding electrical conversion eff iciency and specific output of 7.9% and 1.8 W/cm(3), respectively. Scaling characteristics of the scheme are discussed. The temperature dependence of the output, the output stability, and the beam properties are also reported.

Laser ablation of silicon wafer with a water microdrop

We have developed a new laser ablation process using a water-microdrop with a diameter of 70 μm. The shapes of the debris were investigated at various delay times. A Q-switched Nd:yttrium-aluminium-garnet laser of 25 ns pulse width and 532 nm wavelength was used. The spattering of debris was remarkably reduced by using the water microdrop. The debris pattern was dependent on the shape of the microdrop on the wafer, which in turn was dependent on the surface condition of the wafer and the delay time. The use of a smaller microdrop would result in laser dicing with a small ridge at the rim of the ablation point and no debris. The flexural stress of 720 MPa was obtained near the blade dicing.

Application of a telescopic resonator to high-power chemical oxygen-iodine lasers

The application of an intraresonator telescope to high-power chemical oxygen-iodine lasers to decrease the output beam divergence is analyzed and demonstrated. A theoretical formula based on the ABCD matrix theory is developed to analyze the characteristics of the telescopic resonator. Calculations are carried out using Galilean type telescopes with magnification factors in the range of two to four, and our high-power chemical oxygen-iodine laser as an analysis model. By locating the telescope at a proper position on the optical axis, the overall telescopic resonator can be conveniently tailored to the hardware of this model laser in a way that the beam divergence and the resonator stability can be improved simultaneously. Experiments are carried out for one of the conditions used in the calculations. Measured divergence angles are in excellent agreement with the theoretical values. >

High-performance fast-axial-flow radio-frequency discharge-excited CO laser

The parametric study has been performed to improve the output performance and the beam properties of a fast axial flow, radio frequency (rf) discharge excited CO laser, where an emphasis is placed on the optimization of an electrode configuration. The laser has a single discharge section which consists of a quartz tube and a pair of cylindrical outer metallic electrodes. The measurements have shown that the discharge uniformity is considerably influenced by the curvature radius of the outer metallic electrodes and the air gap spacing between the tube outer wall and the metallic electrode inner surface at the downstream edge of the electrodes. In the experiments, the most uniform discharge over the tube cross-section has been obtained for a metallic electrode curvature radius of 16 mm and an air gap spacing 0.5 mm. As a result, a maximum specific output obtained has reached 1200 W/m at an entrance gas temperature of 140 K, a corresponding rf to optical conversion efficiency being 21.2%. Furthermore, we have also succeeded in efficient room temperature operation with Xe-free mixtures.