中国物理B ›› 2010, Vol. 19 ›› Issue (3): 34209-034209.doi: 10.1088/1674-1056/19/3/034209

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Filamentation-assisted fourth-order nonlinear process in KTP crystal

张喜鹏, 蒋红兵, 陈利, 蒋莹莹, 杨宏, 龚旗煌   

  1. State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, China
  • 收稿日期:2009-04-13 修回日期:2009-09-14 出版日期:2010-03-15 发布日期:2010-03-15
  • 基金资助:
    Project supported by the National Basic Research Program, China (Grant No.~2006CB806007), and the National Natural Science Foundation of China (Grant Nos.~10574006, 10634020 and 10821062).

Filamentation-assisted fourth-order nonlinear process in KTP crystal

Zhang Xi-Peng(张喜鹏), Jiang Hong-Bing(蒋红兵)†, Chen Li(陈利), Jiang Ying-Ying(蒋莹莹), Yang Hong(杨宏), and Gong Qi-Huang(龚旗煌)‡   

  1. State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, China
  • Received:2009-04-13 Revised:2009-09-14 Online:2010-03-15 Published:2010-03-15
  • Supported by:
    Project supported by the National Basic Research Program, China (Grant No.~2006CB806007), and the National Natural Science Foundation of China (Grant Nos.~10574006, 10634020 and 10821062).

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摘要： We present an experimental investigation of a filamentation-assisted fourth-order nonlinear optical process in KTP crystals pumped by intense 1.53~eV (807~nm) femtosecond laser pulses. Femtosecond light pulses at 2.58~eV (480~nm) are generated by the fourth-order nonlinear polarization (P4(ω 2 ) = χ 4(ω 2 ,ω ,ω ,ω ,- ω 1 )E3(ω )E* (ω 1 ), where E(ω ) corresponds to the pump frequency and E(ω 1 ) to the supercontinuum generated through filamentation). If the system is seeded by a laser beam at ω 1 or ω 2 and there are spatial and temporal overlaps with the pump beam, E(ω 1 ) and E(ω 2 ) are simultaneously amplified. When the intensity of the seed laser beam exceeds a certain intensity threshold, the contribution of P4(ω ) = χ 4(ω ,ω 1 ,ω 2 ,-ω, - ω )E(ω 1 )E(ω 2 )(E* (ω))2 becomes non-negligible, and the amplification weakens. The conversion efficiency from the pump to the signal at 2.58~eV (480~nm) attains to 0.1%.

Abstract: We present an experimental investigation of a filamentation-assisted fourth-order nonlinear optical process in KTP crystals pumped by intense 1.53 eV (807 nm) femtosecond laser pulses. Femtosecond light pulses at 2.58 eV (480 nm) are generated by the fourth-order nonlinear polarization $(P^{(4)}(\omega_2))=\chi^{(4)}(\omega_2, \omega, \omega, \omega, -\omega_1)E^3(\omega)E^*(\omega_1)$, where $E(\omega)$ corresponds to the pump frequency and $E(\omega_1)$ to the supercontinuum generated through filamentation). If the system is seeded by a laser beam at $\omega_1$ or $\omega_2$ and there are spatial and temporal overlaps with the pump beam, $E(\omega_1)$ and $E(\omega_2)$ are simultaneously amplified. When the intensity of the seed laser beam exceeds a certain intensity threshold, the contribution of $P^{(4)}(\omega)=\chi^{(4)}(\omega, \omega_1,\omega_2, -\omega, -\omega)E(\omega_1)E(\omega_2)(E^*(\omega))^2$ becomes non-negligible, and the amplification weakens. The conversion efficiency from the pump to the signal at 2.58 eV (480 nm) attains to 0.1%.

Key words: parametric amplification, filamentation, fourth-order nonlinear polarization, KTP crystal

中图分类号:  (Nonlinear optical crystals)

  • 42.70.Mp
42.65.Ky (Frequency conversion; harmonic generation, including higher-order harmonic generation) 42.55.Rz (Doped-insulator lasers and other solid state lasers) 42.60.Jf (Beam characteristics: profile, intensity, and power; spatial pattern formation)