Metas­ur­faces en­able mini­atur­ized op­tic­al pulse shaper

 |  SFBCeOPP  |  Nachrichten AG Zentgraf

Material dispersion accumulated in optical setups tends to heavily distort and chirp ultra-short laser pulses which can be especially disadvantageous in nonlinear optical applications or pump-probe experiments. Typically, pulse compressors consisting of a prism or grating pair are used to partially compensate for the dispersion and reshape the laser pulses to become short again. However, these pulse compressors are limited to correcting only second-order dispersion and are unsuitable for space-limited applications. In our recent publication ‘Compact metasurface-based optical pulse-shaping device’ published in Nano Letters, we show that multiple metasurfaces on a single glass substrate can be used, to alter the dispersion of ultra-short laser pulses allowing for integration on on-chip devices. To achieve this, we used two parallel mirrors on both sides of a substrate to allow successive interaction of incident laser pulses with two metasurfaces (see the schematic figure). We verify, that prior applied dispersion can be compensated with our device by properly designing the local phase of the facilitated metasurfaces and even show a more complex pulse shaping operation by generating a double pulse with 200 fs temporal separation. Depending on the design, the device offers high flexibility, as it can operate in reflection or transmission and with more than two metasurfaces.

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Schematic design of the compact-pulse shaping device. The originally chirped laser pulse interacts with two metasurfaces (MS1 & MS2) between two silver mirrors. MS1 introduces angular dispersion and also focuses the light on MS2 which leads to a wavelength separation. At the second metasurface, wavelength-dependent phase information is applied and in addition, the beam is reflected back to MS1 before it leaves the device through the input aperture. Depending on the applied phase information on MS2, the pulse dispersion can be altered.