Adaptive spatial control of fiber modes and their excitation for high-harmonic generation

Abstract

We present the control of high-harmonic generation (HHG) in hollow fibers using adaptive pulse shaping techniques. The shaping capabilities of our spatial light modulator (SLM) are demonstrated by the excitation of specific fiber modes inside a hollow fiber with a helium-neon laser. Afterwards spatially shaped ultrashort pulses are used to generate phase-matched high-harmonic radiation in a fiber. We show that by controlling the mode structure, we can manipulate the spatial and spectral properties of the generated harmonics.

Coherent control of high-harmonic generation using waveform-synthesized chirped laser fields

“…One is to shape the 800 nm femtosecond pulses generated from a Ti:sapphire laser in the frequency domain, which is divided into dozens of small components and the phases of individual components are adjusted [7][8][9][10][11]. This phase shaping can be combined with an adaptive learning loop [12] such that an optimal combination of the phase components can be found for a predetermined goal, such as to maximize the yield of a particular harmonic order or to maximize the contrast ratio between a target harmonic order and the neighboring orders.…”

“…Selective enhancement of a single harmonic has gained substantial interest in the past decade [7][8][9][10][11]19,20]. Almost all the works have been done using the phase shaping technique and gas-filled fibers [7][8][9][10][11].…”

“…Almost all the works have been done using the phase shaping technique and gas-filled fibers [7][8][9][10][11]. It has been experimentally confirmed by at least two groups that using the phase shaping technique, single harmonic enhancement cannot be achieved using gas jets [6,9].…”

“…This implies that some spatial fiber modes must be exploited which greatly complicates the understanding of this process. Additionally, both the selectivity and the contrast are limited: The spectral region within which a single harmonic can be selectively enhanced is narrow and the contrast ratio between the target harmonic and its nearest neighbors is usually limited to two or three times [7,10]. These limitations are the consequences of the narrow bandwidth of an 800 nm field.…”

Coherent control for the spherical symmetric box potential in short and intensive XUV laser fields

“…More recently, as a further step towards XUV coherent control, Pfeifer et al have realized control of the branching ratio of the dissociative photoionization of sulfur hexafluoride by adaptive shaping of the HHG generating infrared field [11]. ii) Other groups use wavefront or fiber mode shaping methods to enhance harmonic yield, for a given harmonic, in the HHG process [12][13][14][15]. This does not involve temporal shaping of the pulse to first order, however, it proved to be powerful for enhancing the harmonic yield.…”