I have several ongoing projects, ranging from THz radio-over-fiber communication and sensing technology,
nano-structured silicon solar cells to attosecond science and technology.
The last of which is a new initiative and I expect to devote considerable time for its execution in the next five years.
Synopses of these ongoing projects are summarized below:
[ 1 ]
Studies of Key Components and Technologies for Radio and Ultra-Wideband
Over Fiber Communication System at V- and Beyond W-bands (Main)
(NSC, Aug. 1, 2009-July 31, 2012)
Terahertz (THz) wave, the relatively less explored
electromagnetic radiation in a frequency interval from 0.1 to 10 THz,
has traditionally only been the domain of astronomers and molecular
spectroscopists. Relatively few applications relevant to the society in
general have been explored, however. The so-called THz gap of the
electromagnetic spectrum is illustrated below:
Relatively few applications relevant to the society in general have been explored, however.
Spurred by discovery of new physical principles and innovative technologies in photonics,
advanced materials and nanotechnology, novel applications of THz waves (also called T-rays) in basic science,
security, medical diagnostics and treatment, nondestructive inspection,
and manufacturing quality-control have recently been
THz sensing, in particular, has attracted lots of attention due to it is molecular unambiguousness.
THz imaging potentially can even allow spotting the onset of cancer and is complementary to widely
used techniques such as optical coherence tomography (OCT).
As a result, companies such as Nikon, Coherent, Picometric and Teraview are pursuing commercialization of THz technology.
Marketing opportunities for security screening in airport,
counterfeit prevention in drugs/pharmaceuticals, defect detection in semiconductor manufacturing,
and other high-value areas appear promising.
Nonetheless, these efforts are hampered for the lack of room-temperature THz emitters or
THz receivers that cost just a few dollars and are the size of a coin.
Information and communications technology should also benefit from advances in THz science and technology.
The synergy of research areas such as wireless communication,
biomedical and environmental sensing, as well fiber-optic
communication with THz science and technology will generate a wealth
of applications in, for example, biometrics — the development of
recognition techniques based on unique human physical or behavioral
traits — using a THz camera, massive sensor networks and selective
is actively pursuing Wimax technology (2-11 GHz), while a Wireless HD (WiHD) Interest
was recently established by companies like NEC, Sony, Samsung and
LG. Its goal is to establish a wireless digital interface to combine
uncompressed high-definition video, multichannel audio data toward
the unlicensed 60 GHz band.
Extending wireless communication to the THz frequency band is one of the holy grails for researchers in THz science and technology.
A roadmap of THz Science and Technology in information and Communication technology was recently put forward by Tonouchi [Nature Photonics, 1(2):97, 2007]：
A roadmp of THz Science and Technology in Information Technology
Recently we have made significant breakthroughs in THz communication and sensing, e.g.,
the demonstration of directly modulated THz audio and burst communication link and integrated THz biosensing chip.
This is possible only through emergence of novel THz functional elements such Photonic THz transmitters and liquid crystal tunable
THz photonic devices developed by the PIs. In this project,
we propose to demonstrate certain milestones of ultra-wide-band (UWB) THz impulse radio communication and sensing
network for future ultra-broadband media, data and biomedical applications using the discoveries mentioned above.
For the near-term (five to 10 years), however, it is more practical
to consider a V-band or W-band ROF or ultrawide band over fiber (UOF)
The broadband data signals are first transmitted in an optical fiber
that has low propagation loss and high data capacity. Then, the
signal is radiated in free space over the last mile to the end user
via a photonic transmitter. The system can thus provide broadband
wireless communication services for the user.
The figure below shows the conceptual setup of the radio-over-fiber communication system and its key components.
By using such system, we can distribute the W-band optical signal through the nearly lossless optical fiber and radiate
it for the end users. Hence, the problem of huge free-space propagation loss of W-band signal can be minimized.
The proposed Radio-Over-Fiber Communication system and its key components
This project is an integrated project joining the efforts of teams
from NTHU, NCU, and NCTU. We will develop the key components and
related technology, including the optical sources, active
components, and high-speed circuits for the applications
radio-over-fiber (ROF) and ultra-wideband (UWB)-over-fiber (UOF)
communication systems at V- and beyond W-bands. We will also
integrate the developed components by use of flip-chip bonding
technology and test the transmission characteristics, which include
eye-patterns, bit-error-rate, and error-vector-magnitude, of such
integrated module. Regarding the optical sources for ROF
communication system, a clean and continuous-wave (CW) optical MMW
sources with over 100GHz operating frequency will be demonstrated.
On the other hand, the shaped optical pulse trains with special
coding scheme, whose envelop cover all the available W-bands
(75-110GHz), with high repetition rate (>10GHz) will also be
developed for the applications of UOF system. In order to convert
the high-power optical signals from UOF or ROF central stations, we
will also demonstrate novel high-power photodiodes with over
(120GHz) bandwidth and high saturation current performance (20mA).
Furthermore, in order to further amplify the radiated CW or peak
power and reduce their phase noise, we will also demonstrate some
novel nonlinear circuits, such as GaN based piezoelectric oscillator
at W-band, injection-locked oscillator array, and novel
printed-circuit antenna array with high directivity (~20dB) at V-
and W-bands. Nitride-based quantum cascade structures can
potentially be developed as room-temperature THz laser devices.
Overall, this project will cover key active/passive devices,
circuits, optical sources, and the test beds for ROF and UOF
communication system at V- and beyond the W-bands.
[ 2 ]
Photovoltaic technology with self-assembled nanostructures of silicon quantum-dots in mesoporous
silica (NSC Nanoscience Program, Aug. 1, 2008- July 31, 2011).
The project team consists of Prof. C. T. Lee (NCKU), who acts as PI
of the whole project, and members from NCTU and NDL. I am
responsible for overseeing the NCTU (Profs. Jung Y. Huang, Ci-Ling
Pan, Hao-Chung Kuo, Peichen Yu and Hyeyoung Ah) and NDL (Dr. Jia-Min
Shieh) 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.
Initial work is promising (Adv. Mat., 2009). Moreover,
surface plasmonic effects using periodic and random metal nano-particles
can be designed to enhance the transmission in the vicinity of
bandgap energy. Finally, it has been suggested 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.
ResearchRoadmap for highly efficient nano-silcon solarcells
[ 3 ]
Towards Tabletop Sub-Single-Cycle Attosecond Laser Sources (NSC, August 1. 2009-July 31, 2012)
Attosecond (1 as = 10-18
sec) science is generally recognized as one of the frontier areas in
science today. There are many potential applications. For example,
Few cycle attosecond pulses have been used to create and then probe
interference of vibrational wave functions in a molecule; control a
simple chemical reaction  and to enable real-time observation of
electron tunneling in atoms. The shortest pulse that have been
generated to date is about 80 attosecond.
In this work, we propose a new scheme of sub-femtoseocond (attosecond)
pulse generation by starting from a single nanosecond laser and
phase lock the cascaded harmonics generated by second-order
nonlinear optical processes. It is shown that sub-cycle attosecond
pulses with carrier envelope phase (CEP) control can be generated in
this manner. After full characterization such a light source will be
used to study the generation of higher-order harmonics (HHG) with
extreme ultraviolet (XUV) emission by half-cycle attosecond optical
pulse and the generation of even shorter attosecond pulses. Such
broad ultrashort pulses, spanning a spectrum from the near infrared
to the XUV would be invaluable for dynamic studies of the condensed
matter, including biomolecules. The availability of this source
should stimulate both theoretical and experimental studies of
light-matter interaction on the attosecond time scale. Our vision
of attosecond science and technology is shown in the figure below.
A vision of attosecond science and technology
We have successfully completely the first phase of the construction
of the Tsing Hua Attosecond Source. As a first demonstration,
saw-tooth and square waveforms were synthesized. Initial results
were presented at FiO2010.
The Tsing Hua Attosecond Source (Phase one)
[ 4 ]
There are two on-going projects:
In collaboration with CW Laser Corportation, we
propose to improve the performance of traditional small form-factor
diode-pumped and frequency-doubled solid-state green laser. The key
task is the stabilization of the operation wavelength of the diode
pump laser. Various approaches for wavelength locking will be
explored. The operation temperature range of this laser is expected
to extend from 0 to 50°C. Such lasers will be much more suitable for
industrial applications such as instrumentation in outdoor
environments and the laser display.
In collaboration with Prime Optical Fiber Corporation (POFC) and the
CW Laser Corporation, we have been conducting research and
development of advanced short-pulse fiber-based lasers. By
frequency-doubling technique, we will also demonstrate high power
green output. Such lasers would have immediate applications in
scientific research, laser-based manufacturing, laser display and
biomediciene. The tasks for the first year consist of the design,
construction and optimization of mode-locked Yb-doped fiber lasers
with average power > 5 Watts and pulse width <1ps. We also expect to
generate green output exceeding 3 Watts by frequency doubling using
efficient nonlinear crystals.
潘犀靈教授實驗室(Ci-Ling Pan Laboratory)
[ 1 ]
超寬頻訊號載於光纖通訊之基礎與應用研究（國科會NSC, Aug. 1, 2009-July 31, 2012）
兆赫輻射(Terahertz Radiation, 1 THz = 1012 Hz)
（取自 M.Tonouchi, Nature Photonics, 1(2):97, 2007）：
NTT利用UTC-PDs>已證實120-GHz-band millimetre-wave wireless links的可行性，
預期2015年可提升至100G bit s-1。在這同時，混成式的無線電－光纖通訊越來越受到矚目。
開始探討在W-band及更高頻段（> 100 GHz）的超寬頻突波無線－光纖通訊的若干重要議題：
- 建立1550 nm-based UWB-IR 超寬頻脈碼無線－光纖通訊測試平台。
- 展示1550 nm-based之10 Gb/s UWB-IR 無線－光纖通訊連結及加碼與解碼技術。
[ 2 ]
高效率矽奈米結構太陽能電池：含自組裝矽量子點之奈米孔洞氧化矽複合材料之光伏特技（國科會NSC, Aug. 1, 2009-July 31, 2012）
[ 3 ]
新型寬頻次飛秒光源產生與光同調性研究：桌上型亞週期阿秒雷射光源之研究（國科會NSC, Aug. 1, 2009-July 31, 2012）
並加以相位鎖定及控制，則其合成之光脈衝將短至次飛秒級，且其脈衝包絡相位（carrier envelope phase）可控制。
經由高階諧波產生（Higher Harmonic Generation），預期應可在短期內產生短至XUV（~ 50nm）波長的同調光。
最近，此新型阿秒（attosecond, 1 as = 10-18秒）雷射系統的雛形已由潘教授的團隊在清華大學架設完成。
[ 4 ]
(a) 應用於雷射精密加工之高尖峰功率光纖雷射之研發（虹竣科技、卓越光纖、國科會NSC, Sept. 1, 2010 - Aug. 31, 2013）
最近固態照明與太陽能電池產業對高速晶片切劃（lase wafer scribing）的需求殷切，而雷射加工機的關鍵組件：
與虹竣科技、卓越光纖POFC 合作，我們提議研發先進的短脈衝、高功率Yb 光纖雷射，再經由非線性頻率轉換技術將之轉換至紫外光，以應用於雷射加工之用。
光纖雷射規格分年達到平均功率 <10W, 尖峰功率 >10KW, 雷射脈寬 < 10 ps（第一年）；平均功率 >20W, 尖峰功率 >100 KW,
雷射脈寬 < 2 ps（第二年）；平均功率 >50W, 尖峰功率 >250 KW, 雷射脈寬 < 1 ps（第三年）；
(b) Light Peak 技術用新穎光纖之研究（卓越光纖、科學工業園區研發精進產學合作計畫，Oct. 1, 2010 – Sept. 30, 2011）