Prof. Mario C. Marconi

Department of Electrical and Computer Engineering, Colorado State University

 

Time resolved holographic imaging

 MOVIE OF OSCILLATING NANO PILLARS 200 nm WIDTH AT 1.16 MHz BY SINGLE SHOT TIME RESOLVED HOLOGRAPHIC IMAGING

 

Experimental set up

Text Box:    Figure 1: Scheme of the experimental set up.  The EUV laser beam is splitted by a zone plate and generates an illumination beam (zero order) and a reference spherical beam (1st order).  The interference between these two beams is recorded in a CCD.  A beam stopper (beam block) prevents the zero order from saturating the detector.

 

 

 

 

 

 

 

 

 

 

 

A Fourier Transform Holography (FTH) configuration was implemented using as illumination source a table top EUV capillary discharge laser. The holograms are recorded in a charged-coupled device (CCD) camera and numerically reconstructed.  With this experimental configuration it was possible to achieve time resolved holograms (or flash holograms) with a temporal resolution determined by the laser pulse width, in this case 1 nanosecond.   Figure 1 is a schematic of the experimental set up for holographic recording. The EUV laser radiation was directed onto the Fresnel zone plate which was used as a beam splitter, generating the illumination and the reference beams.  The object (a nanopillar array) was located in close proximity of the zone plate focal plane.  The un-diffracted zero order beam illuminated the object (nanopillar array) producing a diffracted object beam. The object beam was superposed in CCD detector plane with the spherical wave generated by the first order focal point of the zone plate.

 

Time-resolved imaging of oscillating pillars

Text Box:    Figure 2: Sequence of holograms displaying oscillating pillars.  The images with the pillars in different locations can be composed in a “movie” of the oscillating pillars that is available by request

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time-resolved holograms of oscillating nanopillars were recorded using single-shot exposure.  Each pillar has a length of 15 µm and a width of 200 nm. The sample was attached to a ceramic piezoelectric that was excited with a sinusoidal wave 10 V peak to peak at a frequency of 1.16 MHz.  Several single shot holograms were recorded of the oscillating pillars using the experimental set up shown in Figure 1. Figure 2 is a sequence of different single shot holograms obtained in different positions of the pillars. With this sequence of images it was possible to compose a “movie” of the oscillating pillars by sequentially displaying the different images as frames in a film.  The movement of the pillars is clearly visible in the movie.  To see the movie click HERE.