On-going research projects of Ci-Ling Pan Laboratory

 I have several ongoing projects or proposals under review, ranging from THz radio-over-fiber communication and sensing technology, nano-structured silicon solar cells to attosecond science and technology.  Pursuing such a wide range of topics is possible only because of the buildup of a state-of-art laboratory over the years and my network of outstanding collaborators.  A summary of these ongoing projects are listed below:

1.      THz Communication and Sensing Technology (NSC and pending)

THz communication is one of the holy grails for researchers in THz science and technology. While tremendous progress has been made in THz sensing and imaging, novel concepts and devices are needed for making such services commercially viable. Recently we have made significant advances in both areas, e.g., the demonstration of directly modulated THz audio and burst communication link and THz fiber endoscope. We note that commercialization of 60 GHz Radio-over-fiber technology has caught the attention of global leaders in high-tech industries. In this project, we propose to leverage expertise of leading Taiwanese groups in THz science and technology, optoelectronics and optical fiber communication to demonstrate certain milestones of multi-service THz Radio-over-fiber communication and sensing network for future ultra-broadband media, data and biomedical applications. These include:

1. Demonstration of efficient sub-THz (100- to 500 GHz) photonic THz transmitter and receiver.

2. Demonstration of data encoding on THz signals in the 10s of Mb/s range

3. Design and development of GaN-based room-temperature GaN-based Quantum Cascade Lasers for THz communication and sensing.

4. Conception demonstration of low-cost 60GHz radio-over-fiber communication system.

5. Development of fiber-compatible integrated THz biosensing biochips.

Realizing these tasks should catch eyes and ears of the world and help the local electronic, optoelectronic and wireless communication industries leapfrog over international competitors. This holds the future of a new multi-billion vertically integrated high-tech industry.  The proposal will be submitted to Foresight Taiwan.  It involves another outstanding THz researcher in Taiwan, Prof. Chi-Kuang Sun (NTU) and key PIs of SP-I and SP-II of the Program for the pursuit of Academic Excellence, Phase II (PPAEU-II) project, e.g., Profs. Yin-Chieh Lai, Jason Chen, Chi-Way Chou, Jin-Wei Shi (NCU) and Hao-Chung Kuo.  A subset of the above mentioned project, entitled “towards THz communication technologies (I),” has been funded by the NSC this year.  

2. Photovoltaic technology with self-assembled nanostructures of silicon quantum-dots in mesoporous silica (NSC Nanoscience Program, Aug. 2008- July 2010).

This proposal was submitted in collaboration with Prof. C. T. Lee 李清庭(NCKU), who acts as PI of the whole project.  I am responsible for overseeing the NCTU (Profs. Jung Y. Huang, Ci-Ling Pan, Hao-Chung Kuo, Peichen Yu and Hyeyoung Ahn) and NDL (Dr. Jia-Min Shieh and co-workers) portions of the project and also lead the effort on investigating the underlying physical mechanisms in the novel nanostructured silicon material. Experimentally, various ultrafast and THz spectroscopic techniques will be employed, in additional to the more conventional spectroscopic methods, such as spectroscopic ellipsometry. Previously, enhanced UV-to-NIR photoresponse has been reported by the NCTU and NDL team for a photodiode with dense silicon quantum-dots embedded in MS. Phototransistor-like operation due to enhanced exciton resonant tunneling and injection was observed.  We thus propose a related solar cell structure made of a superlattice of silicon quantum dots with gradually varying sizes inserted between p- and n-type tailored mesoporous materials. To enhance the PV efficiency, various approaches involving cost-effective methods for transmission enhancement of solar energy will be investigated.  For example, a double-layer anti-reflective structure consisting of a dielectric film and a mesoporous layer of low refractive index will render the front surface of the device more effective in capturing photons. Preliminary results confirm the validity of this approach. Further, Indium-Tin Oxide (ITO) nanostructures not only offer broad angular and spectral anti-reflective characteristics, but also improve the electric properties of the cell, reducing the screen ratio of metal contacts. Works are ongoing at NCTU and laboratories of our collaborator, Prof. Shawn Y. Lin of RPI. Moreover, surface plasmonic effects using periodic and random metal nano-particles can be designed to enhance the transmission in the vicinity of bandgap energy. A recent report in Science magazine suggests that silicon nano-pillar structures can significantly alter the thermoelectric properties of bulk material. Hence, we will explore nanostructures with a high thermoelectric coefficient in order to harvest the waste heat from p-n junctions. In addition, a surface plasmonic coupling layer or even an optical antenna structure can be employed to offer free-space-to-device photon-capturing functionality without coupling loss. Finally, a wavelength up-conversion layer can be realized with appropriate nanocrystals embedded in MS to convert solar radiation from near IR to the visible region, promising efficient use of photons over the entire range of AM1 solar spectrum.

3.    Advancing toward subfemtosecond and attosecond science and technology (Thematic Project, Academia Sinica, Jan. 2009-Dec. 2011)

        I am one of the sub-project PIs and plan to devote more efforts to this challenging project in the coming years.  The overall PI is Prof. Andy Kung of the Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica.  A complementary proposal will be submitted to the Science Directorate of NSC at the end of 2008. Currently the main experiments have been carried out at IAMS. Attosecond pulse generation is one of the most exciting topics in laser science currently, as it provides a means to study dynamics on the attosecond time scale. Our approach is based on the creation of multiple Raman sidebands through stimulated Raman scattering in molecular hydrogen. Initial results are encouraging. It is unique in that the center wavelength of the sub-femtosecond pulse train is in the visible to ultraviolet region, more amendable to dynamic studies than the other competing approach, i.e., higher-harmonic generation. Recently, we report phase locking of 7 Raman sidebands and producing a train of pulses that are 0.83 cycles long and have an electric field pulse width of 0.44 fs [Phys. Rev. Lett. 100, 163906 (2008)]., thus assuming the world-leading role in this field. Our next target is achieving phase control between different macro pulses. This would open the door to various applications such as the arbitrary optical waveform generator, which would be a unique tool for quantum state control and manipulation of light-matter interactions.

潘犀靈教授實驗室 (CL Pan Laboratory)

我們鑽研先進雷射及其相關的光電科技，以從事應用（如寬帶光通訊broad band optical communication、材料製程laser processing of materials精密量測precision measurement、生醫感測與造影biomedical sensing and imaging等）導向的基礎研究。最近十年與未來的數年內，我們的研究重點是超快與兆赫光子科技（Ultrafast and THz Photonics）領域，執行教育部與國科會學術卓越計畫，擔當本校「五年五百億計畫」之「跨領域光電科技研究中心」的研究重點之一，「兆赫與同調光子學」課題。本課題的主旨在經由控制光、電與物質之交互作用，以發展光電科技的新技術基礎，歡迎對光電科技懷抱熱忱的同好加入本實驗室。未來三年我們的主要的研究主題包括

(i)  兆赫光子科技

我們研發結合液晶、光子晶體及meta-material結構之可操控THz光電元件、配合【寬能隙光子科技】研究群，研發量子階梯結構THz光源及接受器研發與飛秒頻率光梳femtosecond frequency comb（2005諾貝爾物理獎課題）結合之THz標準頻率及量測技術、研發新穎之THz感測與影像顯示與顯微技術、配合【寬能隙光子科技】與【新穎光纖光子科技】研究群研發THz通訊及結合光纖通訊之THz Radio-over-fiber超寬頻通訊技術。

(ii)    新型寬頻次飛秒光源產生與光同調性研究，

與孔慶昌（IAMS and NCTU）、李兆奎教授（NSYSU，合作，利用在氫分子中產生多個拉曼次能带(Raman sideband)，目前已可產生短於飛秒（數百埃秒，attosecond or as , 1 as = 10^-18sec的超快脈衝，未來我們研究課題包括激發機制、量子態調控與動力學、產生更多次能帶、增加脈衝間距、產生單一埃秒脈衝與真空環境的脈衝調變等課題。目標除了增加次能帶以壓縮脈衝寬度外，可利用f-2f技巧對脈衝CEP offset進行量測甚或控制、與此新穎光源在造影與表面科學的研究。為此，我們也將發展使用範圍由紅外至紫外的液態晶體空間光調制器。

(iii)   新奇奈米結構矽基鐵電材料之開發與光電元件：

矽奈米結構物已證實有量子侷限或介面態調控直接能隙、及光學極化等特性，可視為新型半導體材料。與謝嘉民博士（NDL and NCTU）、黃中垚教授等合作，我們首度發展出三維分佈矽(鍺)氧奈米結構化薄膜，經由控制材料介面態，展現出新奇類鐵電、寬光吸收能帶、載子共振隧遷、及非線性光學等光電特性。因此可發展低能量損耗量子點電荷或鐵電電場感應之電晶體記憶體，及寬頻帶、增益響應光偵測器。如透過量子點對光激發載子儲存功能，在脈衝電激發操作下，可發展矽基場效電致光輻射器。另外，矽(鍺)量子點奈米結構物-能更有效率的利用吸收光子及傳遞光激載子，可發展高性能太陽能電池。這些矽基奈米元件，將對光積體線路(甚或多功能面板)發展，極有助益。