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坪内 雅明; 熊田 高之
no journal, ,
近年開発が進められているテラヘルツパルス光源の産業応用に向けてパルスを自在に整形する技術を開発する必要がある。本研究ではその基盤技術の一つとして、テラヘルツ周波数領域で動作する小型のエタロン素子を開発した。エタロンを構成する高反射板として、シリコン単結晶薄板、及び酸化インジウムスズ薄膜付きガラスの対を用いた。テラヘルツ光をキャビティに入射後、シリコンに紫外光を照射することで光スイッチを動作させ、非常に高い変換効率でTHz光のパルス列化を実現した。
isotopologues utilizing field-free alignment and angular dependent ionization赤木 浩; 笠嶋 辰也*; 熊田 高之; 板倉 隆二; 横山 淳; 長谷川 宗良*; 大島 康裕*
no journal, ,
フェムト秒パルスレーザーによる分子回転制御を利用して、N分子の同位体選択的イオン化を実現した。真空チャンバー内で直線偏光・短パルスレーザーを
Nと
Nの混合ガスに対して照射し、回転コヒーレンス状態を生成する。その後、一方の同位体分子の軸が揃う時刻に、再度、直線偏光・短パルスレーザー光を照射することで、選択的にイオン化した。各同位体のイオン生成量を2つのパルス間の遅延時間を走査しながら測定した結果、その比が0.85-1.22と変化した。
横山 啓一; 松岡 雷士*
no journal, ,
We consider irradiating a train of terahertz-wave pulses to diatomic molecules as a new isotope-separation scheme. The repetition period of the pulses is synchronized with the rotational period of the molecules. The pulse train induces cascade rotational transitions only in the selected isotope molecules due to the difference on the rotational period among the isotopes. Because the cascade rotational transitions start from any initial rotational states, this scheme is applicable to the molecules in a thermal ensemble even at high temperature. We proposed two options based on this scheme; one is that based on the continuous time quantum walk (CTQW) and the other should be called as alternation 
-pulse excitation scheme. The CTQW scheme is simple and speedy, but remains some population unexcited. The alternation -pulse scheme sweeps almost all the population, but requires larger number of pulses.
吉田 芙美子; 横山 啓一
no journal, ,
Molecules are aligned by rotational coherence created with short laser pulses. Then, aligned molecules lose their coherence through the collision. The de-coherence rate is often measured by the decay of the coherent signal, such as four-wave mixing and orientation-dependent ionization. However, all these measurements give information only on the coherent state, i.e., off-diagonal elements of the density matrix. To understand the decoherence process completely, information both on the coherent and incoherent states is required, i.e., whole density matrix including diagonal elements. Therefore, it is worthwhile to develop a technique for measuring both the off-diagonal and diagonal elements simultaneously. As a candidate of such a technique, we explore the potential of the time-resolved vibrational coherent anti-Stokes Raman scattering (CARS) spectroscopy of aligned molecules.