zygo interferometry of gratings michael gully-santiago | grad student UT Austin Silicon Diffractive Optics Group 

who michael gully-santiago astronomer, engineer, bicycle rider amanda turbyfill astrophysicist, basketball enthusiast 

Interferometry tells us two things Where did we go wrong? Is it good enough? 

Interferometry tells us two things Where did we go wrong? Is it good enough? Astronomers care about this Engineers care about this 

There are two data products Where did we go wrong? Is it good enough? Astronomers care about this Engineers care about this PSF FULL MAP 

PSF FULL MAP The two data products are related to each other 

PSF FULL MAP The two data products are related to each other Sub aperture FFT € ∫∫ 

Let’s talk about the full map. Since we’re engineers 

You have to de-project the full map. 

de-project 

We didn’t used to de-project 

We didn’t used to probably because astronomers don’t care. de-project 

We didn’t used to probably because astronomers don’t care. but now we’re learning something, because de-projected images look like what engineers see. shadow of grating holder Shadow of grating holder Photoresist thickening at edge Periodic structures resembling Newton’s fringes Comets from photoresist spin Photoresist thickening at edge de-project 

We can do even better with shadow of grating holder Shadow of grating holder Photoresist thickening at edge Periodic structures resembling Newton’s fringes Comets from photoresist spin Photoresist thickening at edge 

high pass* . We can do even better with shadow of grating holder Shadow of grating holder Photoresist thickening at edge Periodic structures resembling Newton’s fringes Comets from photoresist spin Horizontal artifact, probably from using the cart and slit. high pass filtering* is: way faster than fitting Zernike polynomials. k ~ 51 pixels is the median smoothing kernel d = d - median( d, k ) 

But since we are astronomers and engineers, we want the best of both worlds™, so: We are proud to introduce… ZIGZAG: Zygo Interferometry of Gratings with Zernike Analysis by Gully 

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H! L! !" Silicon! Desired line edge position! Realized line edge position! Value measured by Zygo! 

I’m having a hard time getting the PSF to work. This is either hard or I am not smart enough to figure it out. Help! 

In summary: [email protected] | astronomer and engineer You have to de-project the full map. and high pass filter and ZIGZAG™ does it all except PSFs… for now.