Dr Bangshan Sun

DPhil, Dynamic Optics and Photonics Group

Department of Engineering Science

University of Oxford

Email: bangshan.sun at eng.ox.ac.uk

Research Interests:

My current research is the interdisciplinary combination of optics, material science, physics and electronics, specifically concentrated on the precisely adaptive laser micro-fabrication of micro/nano structures in various materials, such as diamond, silicon glass, polymers et al. Both experimental and theoretical studies are included. High quality direct laser material processing enables important advances in photonics, electronics and material science. My previous research involves multiple polymer dielectric thin films and metal film coating for low-loss hollow fibers and terahertz waveguides. I completed my PhD study within two years.

 

High Conductivity, 3D Graphite Micro/nano Wires inside Diamond

Homogeneous, uniform graphitic wires with arbitrary 3D shapes were created by adaptive femtosecond laser fabrication inside diamond. Highly conductive ultra-thin wires with a width of 400 nm were enabled. The resistivity of fabricated features was found to be as low as 0.022 Ω cm, significantly reduced by more than two orders compared to previous reports. Fabrications along the entire three axes and any 3D shapes are possible. 

 Wires

Microscope images of spiral and helical graphite wires inside diamond.

Promising applications could be enabled based on laser induced micro/nano graphitic structures in diamond. Images below show a fabricated micro-capacitor that can be used to create high local electrical field between two plates. The size of capacitor is 300 × 10 µm, with a distance of 1 µm between two plates.

Wires2

Microscope image of graphite micro-capacitor inside diamond.

Another wide application is the graphitic electrode arrays for radiation detector devices. Image below shows the fabricated 3D electrode array. Each electrode has a length of 500 µm, separated with a distance of 120 µm.

Wire Array

Microscope image of 3D graphite electrode array inside diamond.

Aberrations in Laser Focusing

Phase aberrations affect the lens focal distribution in optical systems. This has been shown for lower order Zernike modes and refractive index mismatch aberrations in widefield and line temporal focusing. The particular aberrations cause reduction of the axial and lateral resolution, reduction in peak intensity, or position shift of the focus. These investigations show the sensitivity of certain focusing methods to specific aberrations, and can inform on the necessity and benefit of aberration correction.

Effect of aberrations (Zernike modes 5-11) on wide-field spatio-temporal focusing (SSTF, top row), and conventional focusing (bottom row).

B. Sun et al., JOSA A 31, 765-772 (2014)


Multi-layer Photonic Bandgap Fibers (Waveguides) for Infrared, Terahertz Applications

Low loss hollow bandgap fibers were designed and fabricated by inner-coating of a metal and multiple dielectric layers. Silver was chosen as the metal layer. In the infrared region, SiO2 and AgI were chosen as the dielectric materials. In the THz region, certain polymer materials and the polymers doped with particular particles are used as the low and high index dielectric. An obvious bandgap effect was demonstrated experimentally.

Fiber

Picture and structure of hollow fiber.

 

Education Background

DPhil               Department of Engineering Science, University of Oxford (2013 - 2015)

BEng, MEng   School of Information Science and Engineering, Fudan University (2006 - 2013)           

Publications                                                          

1.     Bangshan Sun, Patrick S. Salter, and Martin J. Booth, “Pulse front adaptive optics: a new method for control of ultrashort laser pulses,” Opt. Express, vol. 23, no. 15, p. 19348, 2015.
2.     Bangshan Sun, Patrick S. Salter, and Martin J. Booth, “Pulse front adaptive optics in two-photon microscopy,” Opt. Lett., vol. 40, no. 21, p. 4999-5002, 2015.
3.     Bangshan Sun, Patrick S. Salter, and Martin J. Booth, “Effects of sample dispersion on ultrafast laser focusing,” J. Opt. Soc. Am. B, vol. 32, no. 7, p. 1272-1280, 2015.
4.     Bangshan Sun, Patrick S. Salter, and Martin J. Booth, “High conductivity micro-wires in diamond following arbitrary paths,” Appl. Phys. Lett., vol. 105, p. 231105, 2014.
5.     Bangshan Sun, Patrick S. Salter, and Martin J. Booth, “Effects of aberrations in spatiotemporal focusing of ultrashort laser pulses,” J. Opt. Soc. Am. A, vol. 31, no. 4, p. 765, 2014.
6.     Xiao-Li Tang, Yi Jiang, Bangshan Sun, Jian Chen, Xiao-Song Zhu, and Yi-Wei Shi, “Elliptical hollow fiber with inner silver coating for linearly polarized terahertz transmission”, IEEE Photonics Technol. Lett., vol. 25 p. 331-334, 2013.
7.     Xuan Zeng, Bing-Hong Liu, Yu-Jing He, Bangshan Sun, Katsumasa Iwai, and Yi-Wei Shi, “Low-loss AgI/Ag hollow fibers for laser light delivery in the near-infrared region”, Opt. Laser Technol., vol. 49, p. 209-212, 2013.
8.     Bangshan Sun, Xiao-Li Tang, Xuan Zeng, and Yi-Wei Shi, “Characterization of cylindrical THz metallic hollow waveguide with multiple dielectric layers”, Appl. Opt., vol. 51, no. 30, p. 7276-7285, 2012,.
9.     Bangshan Sun, Xiao-Li Tang, Yi-Wei Shi, Katsumasa Iwai, and Mitsunobu Miyagi, “Optimal design for hollow fiber inner-coated by dielectric layers with surface roughness”, Opt. Lett., vol. 36, no. 17, p. 3461-3463, 2011.
10.  Bangshan Sun, Xuan Zeng, Katsumasa Iwai, Mitsunobu Miyagi, Nan Chi, Yi-Wei Shi, “Experimental investigation on liquid-phase fabrication techniques for multilayer infrared hollow fiber”, Opt. Fiber Technol., vol. 17, p. 281–285, 2011.
11.  Xiao-Li Tang, Bangshan Sun, and Yi-Wei Shi, “Design and optimization of low-loss high-birefringence hollow fiber at terahertz frequency”, Opt. Express, vol. 19, no. 25, p. 24967-24979, 2011. 


Conference Presentations

1.     LAMP 2015, “Three dimensional laser micro-fabrication in diamond”, Kitakyushu, Fukuoka, Japan (May, 2015). Won conference prize: “Outstanding Student Paper Award (Oral)”
2.     Photon14 (Optics and Photonics 2014), “Wave and pulse front distortions in laser fabrication”, Imperial College London, London, UK (Sept., 2014)
3.     LPM 2014, “Wave front distortions in focusing of ultrashort pulses for laser machining”, Vilnius, Lithuania (June, 2014)
4.     OTST 2013, “Cylindrical THz metallic hollow waveguide with multiple dielectric layers”, Kyoto, Japan (Apr., 2013)
5.     SPIE Photonics West, “Optimal design for hollow fiber inner-coated by dielectric layers with surface roughness”, San Francisco, United States (Jan., 2012)

 

Awards                                                                 

2015                “Outstanding Student Paper Award (Oral)” on LAMP 2015 conference

2015                “Charles Green Award” from Jesus College, University of Oxford

2013-2015       Leverhulme Trust D.Phil studentship (full coverage, very rare for overseas student in Oxford)

2013                SPIE Optics and Photonics Education Scholarship (one of eight winners in China)

2012                China Graduate National Scholarship (China’s most prestigious scholarship, rank 1st/80)

2012                Kwang-Hua Scholarship (the most prestigious scholarship of Fudan University)

2011                SNDA Scholarship (the top one winner in my school, 1st /1000+)

2010-2013       First Prize Scholarship of Fudan University, winner in each year (1st/25)

2010                Outstanding graduate of Fudan University (Honored degree)

 

Personal Hobbies                                                         

Chinese traditional painting

Chinese traditional calligraphy

Fishing

Travelling