Tomonari Nakamura

Characteristics of an all gas-phase iodine laser using molecular iodine as atomic iodine donor

The laser action of an all gas-phase iodine laser (AGIL), which uses molecular iodine as a source of iodine atoms, has been demonstrated. The laser is based on the energy transfer reaction between metastable NCl(a?1?) and ground state I(2P3/2) atoms, which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of the chemical species, the laser output powers are measured at three different positions in a flow reactor. The output power is characterized by a function of the optical axis position and is in reasonable agreement with the numerical simulation. A repetitive pulse of laser output at 50?Hz with a duty factor of 40% is observed. The highest output power is 40?mW at 210?mm downstream from the mixing point of I/H/He and NCl3. This is 80% of the output power generated from the conventional system using HI as an iodine donor. The measured results of the time-resolved laser output power suggest that the output power of the I2-AGIL is more sensitive to the electric discharge plasma intensity as compared with that of the HI-AGIL. An AGIL operated using I2 could potentially have the same output power as that of an AGIL operated using HI if a continuous-wave electric discharge generator is used.

Observation of Pumping Reaction in an Amine-Based All Gas-Phase Iodine Laser Medium

Gain measurement of all gas-phase iodine laser (AGIL) based on amine-based reactions is conducted. Three gaseous species, namely, NCl3, H, and HI are mixed in a glass tube, in which injection ports of each species are optimized using a numerical simulation code developed in our laboratory. The laser duct is attached downstream to the mixing tube, and a probe beam of 1315 nm passes at 23 cm downstream from the mixing point of H and HI. Hydrogen atoms are produced by the microwave discharge of the H2/He admixture. When NCl3 is not supplied, absorption by the 2P1/2–2P3/2 transition of iodine atoms is observed. When NCl3 is supplied, the absorption dip occasionally turns to the hump, which means that the energy transition from NCl(a1Δ) to iodine atoms results in population inversion. The observed small signal gain is 0.005%/cm. However, the reproducibility of the observed phenomenon is poor and presumably, some uncontrolled factor affects the gain evolution. To our knowledge, this is the first observation of a positive gain of the amine-based AGIL system.

A study on an all gas-phase iodine laser based on NCl3 reaction system

Numerical simulation and flow-tube experiments are conducted to understand the chemistry of the amine based all gas-phase iodine laser (AGIL). The numerical simulation code developed is a one-dimensional, multiple-leaky-stream-tubes kinetics code combined with all the known rate equations to date. The validity of the code is confirmed to compare the calculated results with experimental results reported elsewhere. We find that the key reactions to achieve positive gain are the deactivation reaction of excited iodine atoms by chlorine atoms and the self annihilation reactions of NCl(1Δ). The order of the injection nozzles is crucial to suppress these reactions. It is shown that positive gain is possible with optimized flow rates and nozzle positions. Flow reactor experiments are conducted based on these calculations, and small signal gain is measured. The results are compared with the calculations.

An experimental study on a cylindrical multi-pass cell

A new type multi-pass cell was demonstrated for absorption spectroscopy. This cell is useful when performing gas measurement. Moreover, the optical characteristic of a cell was verified.

An all gas-phase iodine laser using molecular iodine as atomic iodine donor

The characteristics of an all gas-phase iodine laser (AGIL) that uses molecular iodine as a source of iodine atoms is studied. The laser is based on the energy transfer reaction between metastable NCl(a1Δ) and ground state I(2P3/2) atoms, which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of the chemical species, the laser output powers are measured at three different positions in a flow reactor. The output power is characterized by a function of the optical axis position and is reasonably reproduced by the numerical calculation. A repetitive pulse of laser output at 50 Hz with a duty factor of 40% is observed. The highest output power is 40 mW at 210 mm downstream from the mixing point of I/H/He and NCl3. This is 80% of the output power generated from the conventional system using HI as an iodine donor. The measured results of the time resolved laser output power suggest that the output power of the I2- AGIL is more sensitive to the electric discharge plasma intensity as compared to that of the HI-AGIL. An AGIL operated using I2 could potentially have the same output power as that of an AGIL operated using HI if a continuous-wave electric discharge generator is used.

Output power enhancement of an amine-based all gas-phase iodine laser by addition of methane gas

Output power enhancement of an all gas-phase iodine laser (AGIL) by addition of hydrocarbon gases is studied. It is expected because hydrocarbon gases might scavenge Cl atoms, which are strong quencher of the upper state of the laser medium, I(2P1/2). In AGILs, suppression of the Cl atom concentration is the key to improving the efficiency of laser operation because Cl atoms are inherently generated by the self-annihilation of the energy donor, NCl(a1Δ). We found that the addition of CH4 gave the best results because of its high scavenging rate constant and inertness to I(2P1/2). An enhancement of 10% was observed in the output power when CH4 was added at a flow rate twice that of NCl3. On the other hand, when C2H4 or C2H2 were added at the same flow rate as that of CH4, the output power reduced despite their fast removal rate of Cl atoms. The reason for the reduced output power was that the unsaturated bonds scavenged not only the Cl atoms but also the H atoms, resulting in a low density of H atoms, and this decelerated the production of NCl(a1Δ). The observed laser characteristics could be reasonably explained by numerical model calculations.

An all gas-phase iodine laser based on NCl3 reaction system

Theoretical and experimental studies of the amine-based all gas-phase iodine laser (AGIL) are conducted. The numerical simulation code is a detailed one-dimensional, multiple-leaky-stream-tubes kinetics code combined with all the known rate equations to date. Using this code, we find that the key reactions to achieve positive gain are the deactivation reaction of excited iodine atoms by chlorine atoms and the self annihilation reactions of NCl(1Δ). The order of the injection nozzles is crucial to suppress these reactions. Following the calculations, we fabricate a flow reactor apparatus and demonstrate laser action for the 2P1/2-2P3/2 transition of iodine atom pumped by energy transfer from NCl(1Δ) produced by a set of amine-based, all gas-phase chemical reactions. Continuous-wave laser output of 50 mW with 40% duty factor is obtained from a stable optical resonator consisting of two 99.99% reflective mirrors. The observed laser characteristics are reasonably explained by numerical calculations. To our knowledge, this is the first achievement of amine-based AGIL oscillation.

Theoretical and experimental studies of the all gas-phase iodine laser

All gas-phase iodine laser (AGIL) powered by the decomposition of nitrogen trichloride (NCl3) is studied. This reaction scheme uses commonly available reagents and reaction paths are milder than the previously studied azide-based AGIL. Theoretical studies revealed the necessary operational conditions for achieving positive gain. An apparatus is made based on the results of the theoretical works. Positive gain at iodine I(2P1/2)-I(2P3/2) transition is observed for the first time.

Achievement of positive gain in the amine-based all gas-phase iodine laser system

Numerical simulation and flow-tube experiments are conducted to understand the chemistry of an amine-based all gasphase iodine laser (AGIL). The numerical simulation code developed is a one-dimensional, multiple-leaky-stream-tubes kinetics code combined with all the known rate equations to date. Using this code, we find that the key reactions to achieve positive gain are the deactivation reaction of excited iodine atoms by chlorine atoms and the self annihilation reactions of NCl(1Δ). The order of the injection nozzles is crucial to suppress these reactions. Flow reactor experiments are conducted based on these calculations, and small signal gain is measured. When NCl3 is not supplied, absorption of the I(2P1/2)-I(2P3/2) transition is observed. When NCl3 is supplied, the absorption is decreased and the dip occasionally turns to the hump, corresponding to a small signal gain of 5×10-3 %/cm. To our knowledge, this is the first observation of positive small signal gain of the amine-based AGIL system.