Generation of Coherent XUV Radiation in N2 molecule and its Mixture with Ne Gas using Sub-terawatt Laser System

Abstract

High harmonic generation (HHG) in pure nitrogen (N2) and its mixture with neon (Ne) gas was produced. The external laser field producing 6mJ optical pulse energy with 50fs pulse duration at 10Hz repetition rate was focused into a gas jet producing high harmonics. The N2 and Ne gas have different ionization potentials. The strong harmonic signal in pure N2 was produced, and a weak harmonic signal in a mixture of N2-Ne was generated compared to that in pure N2. The increase of Ne contribution in the N2-Ne mixture resulted in a decrease in harmonic signal. Harmonic signal increase and decrease were observed for different N2:Ne ratios. The harmonic generation mechanism was discussed in that the ionization of Ne is difficult compared to N2, and the neutral Ne atom leads to neutral atomic dispersion (phase mismatch), so the harmonic yield decreases.

Keywords

• Extreme ultraviolet radiation
• High harmonic generation
• Three-step model
• Femtosecond laser
• Gas mixtures
• Absorption

N2 Molekülünden ve Bunun Ne Gazı ile Karışımından Sub-terawatt Lazer Sistemi kullanılarak Uyumlu XUV Radyasyonu Üretilmesi

Abstract

Saf nitrojen (N2) gazından ve bunun neon (Ne) gazı ile karışımından yüksek harmonik mertebeler (HHG) üretildi. 10Hz tekrarlama hızında 50fs optik darbe süresi ile 6mJ optik darbe enerjisi üreten lazer alanı, yüksek harmoniklerin üretildiği bir gaz jetine odaklandı. N2 ve Ne gazı farklı iyonlaşma potansiyellerine sahip olduğu için saf N2 gazında güçlü harmonik sinyali ve saf N2'ye kıyasla N2-Ne karışımında zayıf harmonik sinyali elde edildi. N2-Ne karışımında Ne katkısının artması harmonik sinyalin zayıflamasına neden oldu. Farklı N2:Ne oranı için harmonik sinyal artışı ve düşüşü gözlendi. Harmonik üretimi mekanizması, Ne iyonlaşmasının N2'ye kıyasla zor olduğu tartışıldı, ve nötr Ne atomunun, nötr atomik dispersiyona yol açtığı (faz uyumsuzluğu) ve böylece harmonik sinyalin azalmasına neden olduğu açıklanmıştır.

Keywords

• Aşırı ultraviole radyasyonu
• Yüksek mertebeli harmoni üretimi
• Üç-adım modeli
• Femtosaniye lazer
• Gaz karışımı
• Soğurma

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