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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Circularly Polarized Quasimonochromatic High Harmonic Generation
Xiaosong Zhu1, Jie Long1, Hailang Wei1
1Huazhong University of Science and Technology, School of Physics and Wuhan National Laboratory for Optoelectronics, Wuhan 430074, China.
Physical Review Letters
|May 22, 2026
Summary
Generating circularly polarized quasimonochromatic extreme ultraviolet (EUV) pulses is now possible using high-harmonic generation (HHG) with bichromatic fields. This breakthrough enables advanced spectroscopic and imaging techniques.
Area of Science:
- Quantum optics
- Attosecond science
- Nonlinear optics
Background:
- High-harmonic generation (HHG) produces coherent extreme ultraviolet (EUV) pulses.
- Generating circularly polarized quasimonochromatic (QM) EUV pulses via HHG is challenging.
- Circularly polarized EUV is crucial for ultrafast circular dichroism spectroscopies.
Purpose of the Study:
- To experimentally demonstrate the generation of circularly polarized QM-EUV radiation.
- To investigate a novel selective harmonic order enhancement mechanism in HHG.
- To enable advanced spectroscopic and imaging applications requiring circularly polarized EUV.
Main Methods:
- Driving nonaligned CO2 molecules with bichromatic counter-rotating circularly polarized fields.
- Utilizing high-harmonic generation (HHG) for EUV pulse generation.
- Characterizing the polarization of the generated EUV pulses using an EUV polarizer.
Main Results:
- Observed an unreported selective enhancement of a single harmonic order in HHG.
- The enhanced harmonic was over 50 times stronger than adjacent harmonics.
- Achieved higher generation efficiency compared to monochromatic linearly polarized driving lasers, with ellipticity up to 0.92.
Conclusions:
- Successfully generated circularly polarized QM-EUV radiation using bichromatic fields.
- The enhancement mechanism is attributed to resonance between excited and photon-dressed autoionizing states.
- This method offers a promising route for producing high-quality circularly polarized EUV for advanced applications.
