On the fly tunable control of high harmonic generation using a structured pump beam

  Lilya Lobachinsky  ,  Liran Hareli  ,  Yaniv Eliezer  ,  Linor Rapaport  ,  Alon Bahabad  
Department of Physical Electronics, Tel-Aviv University

Control over the macroscopic properties of high-harmonic-generation can be achieved using a modulation of some parameters of the process over extended length scales along the interaction region. It is shown experimentally that a structured pump beam can exert such a control mechanism. In particular, we use a beam constructed of the interference of a Gaussian beam  and a perturbing Bessel beam having tunable parameters. This structured beam is characterized with a periodic intensity modulation which is able to quasi-phase-match the up conversion of a tunable spectral band of the high harmonic emission. High harmonics' enhancement of up to 25 times is achieved for harmonic orders between 25 to 39.