Abstract
Moth-eye structures are patterned onto gallium selenide surfaces with sub-micrometer precision. In this way, Fresnel reflection losses are suppressed to below one percent within an ultrabroad optical bandwidth from 15 to 65 THz. We tune the geometry by rigorous coupled-wave analysis. Subsequently, ablation with a Ga+ ion beam serves to write optimized structures in areas covering 30 by 30 μm. The benefits are demonstrated via optical rectification of femtosecond laser pulses under tight focusing, resulting in emission of phase-stable transients in the mid-infrared. We analyze the performance of antireflection coating directly in the time domain by ultrabroadband electro-optic sampling.
Highlights
Emission of phase-stable mid-infrared transients results from optical rectification [1] or ultrafast transport processes [2] driven by few-femtosecond laser pulses
The control of time-resolved fields in this spectral range has become a cornerstone of the emerging area of time-domain quantum electrodynamics
In order to examine their quantum character and to harness it for metrology or spectroscopy, it is of paramount importance to preserve the purity of the nonclassical state while propagating it across the surface of a nonlinear element
Summary
Emission of phase-stable mid-infrared transients results from optical rectification [1] or ultrafast transport processes [2] driven by few-femtosecond laser pulses. The crystals employed for generating and detecting these states are non-resonant in the relevant spectral regions and reflections at their surfaces constitute the largest threat to quantum applications For typical specimens, these Fresnel losses can eliminate almost half the field amplitude between emitter and detector, constituting a major challenge for achieving a full quantum tomography in the time domain [25]. These Fresnel losses can eliminate almost half the field amplitude between emitter and detector, constituting a major challenge for achieving a full quantum tomography in the time domain [25] Another challenge created by the interface between material and air/vacuum are the echoes spawned by multiple reflections inside the crystal. It compares our experimental data with the numerical simulations and with results from recent literature
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