High harmonic generation

About: High harmonic generation is a research topic. Over the lifetime, 11694 publications have been published within this topic receiving 222650 citations. The topic is also known as: HHG.

Second harmonic generation in free-standing lithium niobate photonic crystal L3 cavity

Abstract: We report on second harmonic generation in a photonic crystal L3 cavity drilled in a thin self-suspended lithium niobate membrane. The cavity, resonant for the pump beam in the telecom wavelength range, exhibits a quality factor of around 500. Second harmonic generation has been measured with a low power continuous laser. A conversion efficiency of 6.4×10−9 has been estimated with an input coupled power of 53 μW.

Wannier-bloch approach to localization in high-harmonics generation in solids

Abstract: High harmonic generation can produce attosecond-long pulses of light, which are a useful probe of physical processes that require extremely high time resolution. A new mathematical analysis shows how electron delocalization contributes to this emission in a solid.

Influence of the main pulse and prepulse intensity on high-order harmonic generation in silver plasma ablation

Abstract: We present experimental studies of high-order harmonic generation in silver plasma ablation performed with the Ti:sapphire laser beams of the Advanced Laser Light Source ($800\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ wavelength, $360\phantom{\rule{0.3em}{0ex}}\mathrm{mJ}$ total energy). We have independently varied the intensity of the prepulse (which creates the plasma ablation) and the intensity of the main pulse (which generates the harmonics), and studied their influence on the harmonic spectrum. We show here that the presence of doubly ionized atoms in the ablation, created either by a strong prepulse intensity or with the irradiation of the main pulse, is ineffective for the generation of harmonics.

Quantum interference during high-order harmonic generation from aligned molecules

Abstract: High-order harmonic generation (HHG) from atoms and molecules offers potential application as a coherent ultrashort radiation source in the extreme ultraviolet and soft X-ray regions1,2,3. In the three-step model4,5,6 of HHG, an electron tunnels out from the atom and may recombine with the parent ion (emitting a high-energy photon) after undergoing laser-driven motion in the continuum. Aligned molecules7,8,9,10,11 can be used to study quantum phenomena in HHG associated with molecular symmetries; in particular, simultaneous observations of both ion yields and harmonic signals under the same conditions serve to disentangle the contributions from the ionization and recombination processes. Here we report evidence for quantum interference of electron de Broglie waves12,13,14 in the recombination process of HHG from aligned CO2 molecules. The interference takes place within a single molecule and within one optical cycle. Characteristic modulation patterns of the harmonic signals measured as a function of the pump–probe delay are explained with simple formulae determined by the valence orbital of the molecules. We propose that simultaneous observations of both ion yields and harmonic signals can serve as a new route to probe the instantaneous structure of molecular systems.

Accuracy Comparison of Absolute Optical Frequency Measurement between Harmonic-Generation Synthesis and a Frequency-Division Femtosecond Comb

Abstract: Using an iodine-stabilized He-Ne laser as a transfer oscillator, we compare absolute measurements of the optical frequency from a traditional frequency synthesis chain based on harmonic generation and from the frequency division technique of an ultrawide bandwidth femtosecond frequency comb. The agreement between these two measurements, both linked to the Cs standard, is 220+/-770 Hz, yielding a measurement accuracy of 1.6x10(-12). We report 473 612 353 604.8+/-1.2 kHz as a preliminary updated value of the absolute frequency of the " f" component for the He-Ne laser international standard at 633 nm.