Multilayer polymer photonic crystals, with a bandgap in the near-infrared (~1.3um), can be easily fabricated using two-photon lithography [1]. To achieve shorter period structures, we explore thermal decomposition to eliminate unpolymerized material and reduce the oxygen content of exposed polymer structures using heat [2]. This method has been shown to shrink polymer structures by a factor of 4 [2,3]. The current challenge is about conserving symmetry and geometry. Those two factors play a significant role in the resulting optical properties. The material strongly adheres to the substrate and requires a deformable/elastic anchoring to enable isotropic (shape-conserving) shrinking of the main photonic crystal structure. After shrinkage, the relative rod diameter appears larger, and we are investigating isotropic oxygen plasma etching to remove some material [2]. Finally, we use Fourier-Image spectroscopy to characterize the bandgaps of fabricated structures (before & after thermal post-processing), comparing results with various simulation tools (Plane-Wave Expansion and finite-difference time-domain). We plan to extend this technique to 3D photonic crystal defect cavities [4,5], in order to facilitate the creation of future quantum devices using quantum emitters in the visible wavelength region.


Shrinking of direct laser written polymeric structures by thermal annealing to move the bandgap into the visible range

Poster session 1 & networking on Gathertown

poster

**BQIT is a three day annual workshop** aimed at enabling leading UK and international academics and industrial partners to come together; to explore and discuss future ambitions and challenges in the field of **Quantum Information Technologies.** Since our conception in 2014 we have had 230 speakers and panellists who have presented their work and opinions on a range of topics, from quantum theory to innovation in industry.


### Welcome Message
The BQIT:21 team welcomes you to the eighth Bristol Quantum Information Technologies workshop! 

Last year was the first time in our workshop's history that we had gone fully virtual. The global circumstances that continue to impact us all professionally and personally have forced BQIT once again to be delivered as an all-virtual workshop for 2021. The access this creates to colleagues across the world who would otherwise be unable to join us, as well as being able to make the workshop free for all attendees due to the lower costs involved in delivering an online workshop, are just a couple of the extraordinary benefits of meeting online. This also means that we can welcome three times as many attendees to BQIT than previous years.   

We take this opportunity to thank each of our speakers and poster presenters for contributing their technical content, this year's sponsors, whose support this year enabled BQIT:21 to be free to all attendees, and to all of our attendees for joining us online this year. We recognise the extra energy required to stay connected and motivated during these difficult times, and are hugely encouraged to see so many of you willing to continue to connect with us on an online platform. 

It is our hope that you have a productive and enjoyable time while you engage and interact with BQIT:21, and to everyone that has helped take BQIT:21 online, thank you! 

**The BQIT board and organisation team **


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### This year's workshop agenda is available here: [Virtual BQIT:21](https://drive.google.com/file/d/1QwsSM0ztnxC_lgUKf3TbO3GvnI44AQkY/view?usp=sharing)
For further information, please contact us at: **bqit-admin@bristol.ac.uk**

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Yu-shao Chen

1

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Shrinking of direct laser written polymeric structures by thermal annealing to move the bandgap into the visible range

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