Overcoming the Bottleneck of State of the Art Fabrication and Manufacturing Processes
ME-EM Graduate Seminar Speaker Series
Imran Afzal, PhD
Gwangju Institute If Science and Technology
Abstract: All state of the art fabrication and manufacturing processes imparts characteristic errors. Which mainly categorized in random and periodic or ghost errors. Some of the errors are of cumulative nature, ghost errors, which are more complex to measure. These errors were not generally effecting significantly on the performance of optical devices because very high quality optics were not required. However, now we are moving to new era of precision optics, where even the well‐established fabrication processes such as optical and electron beam lithography/fabrication characteristic errors becomes significantly important. Usually these errors revealed while performing measurements using the fabricated optical devices. If we can’t measure the errors, we can’t correct the fabrication process which imparting the errors. For example, state of the art Echelle grating fabricated at UTX and holograms (CGH) at NIST are installed for space imaging and X‐ray aspheric mirror testing, respectively. Whose errors/defects are not discernible even using state of the art NIST IR interferometer. However, these devices show ghost images when applied for space imaging applications or testing other devices. There is no good instrument commercially available which can measure the fabrication errors and trace them to the fabrication processes. Only few optical methods are available, which were mainly developed for diffraction grating, particularly for space imaging applications. All of the previous instruments are suffered from low speed, stitching algorithms errors and low dynamic range. Interferometry based methods are only good for measuring very low spatial frequency errors.
We at NIST built an instrument, namely High Dynamic Range (HDR) imager Which could measure the photolithography, e‐beam, laser maskless writing and mechanical writing ghost and random errors, which are traceable to the fabrication and manufacturing processes. I will present this method in detail. Furthermore, I propose that how making some improvements such as using mode‐locked laser source, time‐stretching and single pixel camera this wide FOV method can be improved to gain high spatial as well as temporal resolution. Which could be applied for measuring defects/errors in stationary diffractive optics e.g. diffraction gratings, optical couplers as well as motional structures e.g. MEMs.
Bio: Imran did his Ph. D. in 2015 from Gwangju Institute of Science and Technology, Republic of Korea. He had BS and MS in Computer Science in 2003 and Physics in 2007, respectively. Later, worked as research scientist for one year at Advanced Photonics Research Institute, Republic of Korea. He started his second postdoc as Associate in September 2016 at National Institute of Standards and Technology (NIST), Gaithersburg MD. There, he worked at Nano‐Structured Optics and Optical Surface Metrology group, Physical Measurement Laboratory. Primarily focusing on fundamental measurement challenges in innovative manufacturing of nano‐ and sub‐nano structures on optical surfaces for ultra‐precise optics such as diffractive optics, free‐form complex surfaces for very high quality space imaging applications, since March 2018 he is working at Gwangju Institute of Science and Technology, Republic of Korea. Here he is leading projects on light sheet microscope system development including optical 3D scanning of mouse brain sample using synchronized electronic tunable lens and Galvo‐mirorr. In total, he has almost 12 years of hands on work experience in the fields of optics and nonlinear optics and instrumentation, fabrication processes and measurement of their errors. Sub topics include free space optics, Ti:Sa laser, optical frequency combs, solitons, supersymmetric optics, conical diffraction, diffractive optics, microscopy as well as integrated optical system development including electronic control.
Invited by: Jeffrey Allen
Thursday, March 7 at 4:00 pm
Electrical Energy Resources Center (EERC), 103
1400 Townsend Drive, Houghton, MI 49931