On Monday, 27th of November at 2:00 pm, there will be a GoLP VIP Seminar by Hamed Merdji (Laboratoire d’Optique Appliquée Ecole Polytechnique, Palaiseau, France). The event will take place at Anfiteatro Abreu Faro – Complexo I at IST.

Title: From classical to the quantum nature of high harmonic generation

Part 1 – Classical HHG : I will first present classical high-harmonic generation in semiconductor as a light up-conversion process occurring in a strong laser field, leading to coherent attosecond bursts of extreme broadband radiation. I will show how a strong laser polarization dependence that can be used to gate isolated attosecond pulses. I will show how nano-structuration of semiconductors can be used to generate structured light such as beam carrying orbital angular momentum or to produce a dramatic enhancement of the HHG emission. Our all semiconductor HHG nano-emitters can work sustainability over days and can be used as ultrafast petahertz optoelectronic devices.

Part 2 – Quantum HHG : We propose that attosecond electronic or photonic processes such as high-harmonic generation can potentially generate non-classical states of light well before the decoherence of the system occurs. This could address fundamental limitations in quantum technology such as scalability, decoherence or the generation of massively entangled states. We recently reported experimental evidence of the non-classical nature of the harmonic emission in several semiconductors excited by a femtosecond mid-infrared laser (Theidel et al, submitted to Nature, in review). By investigating single- and double beam intensity cross-correlation, we observe two-mode squeezing in the generated harmonic radiation, which depends on the laser intensity that governs the transition from Super-Poissonian to Poissonian photon statistics. The measured violation of the Cauchy-Schwarz inequality realizes a direct test of multipartite entanglement in high-harmonic generation.