Our laboratory focuses on the design, fabrication, and characterization of advanced optical materials and devices, with an emphasis on tailoring light–matter interactions at the nanoscale.
We investigate a wide range of topics including,
- Optical Coatings of Metamaterials
- Dielectric Anisotropic Thin Films
- Novel Polarization Devices (e.g., Polarization Converters and Perfect Wave Plates)
- Surface Plasmon Resonance
- Two-Dimensional and Three-Dimensional Nanosculptured Thin Films
These studies aim to enable novel optical functionalities for applications in imaging, sensing, and integrated photonic systems.
ACADEMIC & TECHNICAL ACCOMPLISHMENT ：
- Perfect antireflection: design, fabrication and measurement
A simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure was made known to the public in 2007. Similar to the surface structure on the eye of a month, the nanotip array was demonstrated to suppress the reflection of light over a broadband and wide-angle ranges. The ultra-low reflectance exists at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region and over a wide range of angles of incidence and for both s- and p-polarized light.
Selected paper: Yi-fan Huang, Surojit chattopadhyay, Yi-Jun Jen, Cheng-Yu Peng, Tze-An Liu, Yu-Kuei Hsu, Ci-Ling Pan, Hung-Chun Lo, Chih-Hsun Hsu, Yuan-Huei Chang, Chih-Shan Lee, Kuei-Hsien Chen, and Li-Chyong Chen, “Improved broadband and quasiomnidirectional anti-reflection properties with biomimetic silicon nanostructures,” Nature Nanotechnology, 2, 770 (2007).
- Perfect waveplate: design, fabrication and measurement
In 2009, an achromatic waveplate (named perfect waveplate) was manifested existing within the eyes of stomatopod crustaceans of species Odontodactylus scyllaru. Being inspired by the bio-perfect waveplate, a glancing deposition technique was adopted to fabricate a multilayer structure with two different birefringent thin films to ultimately reach an achromatic waveplate. The design method of a perfect waveplate that functioned over a designate wavelength range was also proposed.
Selected paper: Yi-Jun Jen, Akhlesh Lakhtakia, Ching-Wei Yu, Chia-Feng Lin, Meng-Jie Lin, Shih-Hao Wang & Jyun-Rong Lai, “Bio-inspired Achromatic Waveplates for Visible Light,” Nature Communications, 363, 1-5 (2011)
- Deposited metamaterial thin film
Metamaterials are materials that have been artificially engineered to have unusual electromagnetic properties. They have generated a lot of interests in the last few years, largely because of their potential to generate exotic applications such as invisibility cloaks and “superlenses”. In order to mass produce the metamaterial, a glancing angle depositon was applied to grow slanted silver nanorod array and chevronic shape silver nanorod array. Both of which exhibited having negative index of refraction within the visible range. Based on the loss-improvement of Al-SiO2-Al sandwich thin film, the destructive interference of two wave reflected from a negative-index film was illustrated by wave tracing analysis.
Selected paper: Yi-Jun Jen, Akhlesh Lakhtakia, Meng-Jie Lin, Wei-Hao Wang, Huang-Ming Wu and Hung-Sheng Liao , “Metal/dielectric/metal sandwich film for broadband reflection reduction,” Scientific Reports, 3, 1672 (2013)
- Three-dimensional sculptured metal-dielectric thin film
The sculptured thin films have progressed to an amazing three-dimensional structure from a mere two-dimensional one after overcoming the mobility of deposited metal atom. We first introduced the substrate cooling technique to grow various metal nanostructures. Next, the Ag and Au nanohelix arrays showed strong circular dichroism and exhibited strong SERS signals. Then,we sculptured thin film as a metal-dielectric composite. Finally, an Al-SiO2 octagon nanohelix array was fabricated by glancing angle deposition and presented high optical absorption in the visible regime. Besides light absorbers, the above method we proposed would be extended to produce various metal–dielectric octagon nanohelix arrays with desired complex refractive indices to eventually develop novel optical devices in the future.
Selected paper: Yi-Jun Jen, Chien-Chi Chen, and Ci-Yao Jheng, ”Aluminum-jointed silicon dioxide octagon nanohelix array with desired complex refractive index,” Optics Letters, 39, 12 (2014)
Yi-Jun Jen, Yu-Jie Huang, Wei-Chih Liu, Yueh Weng Lin,“Densely packed aluminum-silver nanohelices as an ultra-thin perfect light absorber,” Scientific Reports, 7 : 39791 (2017)
- Tailoring admittance and index separately for a metamaterial layer comprising metal and dielectric films.
The idea of designing an equivalent admittance for a stratiform metamaterial becomes reality on normalized admittance diagram. Also, the equivalent extinction coefficient exists specifically on the admittance diagram with quality. Metal is known as the strongest light absorber but its high extinction coefficient rejects most of incident light. Therefore, a metamaterial with an equivalent admittance close or equal to that of cover medium is made possible to allow the refractive index to be complex with large extinction coefficient as metal. As a result, fabricating an ultra-thin light absorber by tailoring E and N proves to be a successful attempt.
Selected paper: Yi-Jun Jen, Wei-Chih Liu, Tso-Kuei Chen, Yi-Ciang Jhang, “Design and deposition of a metal-like and admittance-matching metamaterial as an ultra-thin perfect absorber,” Scientific Reports, 7: 3076, (2017)
- Hyperbolic metamaterial inspired polarization beam splitter
A linear polarization beam splitter (PBS) functions to separate two linear polarized light from an unpolarized light, and the PBS is required to be broadband in most applications. The common PBS requires many dielectric films to be arranged between a pair of prism to effect in the visible regime. In order to make a concise PBS structure, ultra-thin metal films with thicknesses less than 12nm are introduced in the design of a PBS. Thus, three-layered and five-layered metal dielectric multilayered PBS s are sketched in a normalized admittance diagram. The equivalent admittance of both P pol. and S pol. are customized separately to reach high transmission and high reflection respectively.
Selected paper: Yi-Jun Jen, Yi-Ciang Jhang, Wei-Chien Wang, and Kai-Lun Wu “Metamaterial-inspired compact optical coating for broadband polarization beam splitting,” Optics Express 26(2), pp.811-823. (2018).