Browsing by Author "Pan, CL"

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A liquid crystal phase shifter with a tuning range of over 360 degrees around 1 THz
(2005)
Chen, CY
;
Hsieh, CF
;
Pan, RP
;
Pan, CL
;
光電工程學系
Tunable phase shift over 271 radians (360 degrees) at THz frequencies is achieved with a sandwiched liquid crystal (LC) cell operated over a broad range using magnetically controlled birefriengence.
A liquid-crystal-based terahertz tunable Lyot filter
(2005)
Pan, RP
;
Chen, CY
;
Hsieh, CF
;
Pan, CL
;
電子物理學系
A tunable Lyot filter operating in the terahertz frequency range is demonstrated by using fixed and variable nematic liquid crystals.
A new category of semiconductor nonlinear mirrors for ultrafast pulse generation and switching
(2001)
Pan, CL
;
Liu, TA
;
Shieh, JM
;
Huang, KF
;
光電工程學系
A new type of saturable Bragg reflector with record-low saturation fluence and broad tuning range
(1998)
Shieh, JM
;
Huang, TC
;
Huang, KF
;
Wang, CL
;
Pan, CL
The saturation fluence for a strained triple-quantum-well saturable Bragg reflector was as low as 12 mu J/cm(2) Self-starting femtosecond pulses tunable from 768 to 804nm was realized.
A novel structure for three-dimensional silicon magnetic transducers to improve the sensitivity symmetry
(1996-09-01)
Lin, HY
;
Lei, TF
;
Jeng, JJ
;
Pan, CL
;
Chang, CY
A three-dimensional silicon magnetic transducer with symmetric sensitivities in the x-, y- and z-directions and small cross sensitivity has been demonstrated. Devices are based on a design of a vertical Hall structure using the surrounding trench and symmetric design to suppress the cross sensitivity. The fabrication process is simple and can be used as a part of a standard integrated circuit process. The results show that almost equal sensitivities in all three components of magnetic field can be obtained by coating Ni/Co thin films on the backside of the substrates. The cross sensitivity is only 1.3% of the sensitivity.
A novel structure for three-dimensional silicon magnetic transducers to improve the sensitivity symmetry
(1996-09-01)
Lin, HY
;
Lei, TF
;
Jeng, JJ
;
Pan, CL
;
Chang, CY
A three-dimensional silicon magnetic transducer with symmetric sensitivities in the x-, y- and z-directions and small cross sensitivity has been demonstrated. Devices are based on a design of a vertical Hall structure using the surrounding trench and symmetric design to suppress the cross sensitivity. The fabrication process is simple and can be used as a part of a standard integrated circuit process. The results show that almost equal sensitivities in all three components of magnetic field can be obtained by coating Ni/Co thin films on the backside of the substrates. The cross sensitivity is only 1.3% of the sensitivity.
A novel tunable diode laser with liquid crystal intracavity tuning element
(2004)
Pan, RP
;
Lan, YP
;
Chen, CY
;
Pan, CL
;
電子物理學系
We propose a novel and simple approach for tuning of the laser wavelength. A homogeneously aligned nematic liquid crystal (NLC) cell with 4'-n-pentyl-4-cyanobiphenyl (5CB) is inserted in an external-cavity semiconductor laser as the fine-tuning element of wavelength. Varying the voltage biasing the NLC cell, its extraordinary index of refraction would change due to field-induced reorientation of the LC director. This is equivalent to tune the laser cavity length. As a result, the laser wavelength can be continuously tuned. With a NLC cell 35.5 mum in thickness, the output frequency of the present laser can be tuned over 4 GHz for a 30-cm-long laser cavity without hopping. The driving rms voltage was less than 2 volts.
A novel tunable dual-wavelength external-cavity laser diode array and its applications
(1996-10-01)
Pan, CL
;
Wang, CL
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
We review the principles and characteristics of a novel tunable external-cavity laser diode source. It can operate as either a continuous wave (CW) single-wavelength, a CW dual-wavelength, a single-wavelength mode-locked, or a tunable dual-wavelength mode-locked laser. The gain medium is a commercial laser diode array, The telescopic external cavity consists of a grazing-incidence grating, a lens and a stripe-mirror. The external cavity provides functions of wavelength selection, dispersion compensation and spatial mode control. The characteristics of the laser under CW or mode-locked operation are described. The dual-wavelength laser output exhibits beat note beyond 7 THz. The tunable multi-terahertz beat frequency is characterized by a non-collinear intensity autocorrelation technique. A dual-wavelength interferometer that uses a tunable dual-wavelength laser as the light source is demonstrated. Finally, theoretical analysis is presented, which demonstrates that the dual-wavelength output of the laser is stable if the modes at the two wavelengths correspond to different array lateral modes.
A novel tunable dual-wavelength external-cavity laser diode array and its applications
(1996-10-01)
Pan, CL
;
Wang, CL
;
光電工程研究所
;
Institute of EO Enginerring
We review the principles and characteristics of a novel tunable external-cavity laser diode source. It can operate as either a continuous wave (CW) single-wavelength, a CW dual-wavelength, a single-wavelength mode-locked, or a tunable dual-wavelength mode-locked laser. The gain medium is a commercial laser diode array, The telescopic external cavity consists of a grazing-incidence grating, a lens and a stripe-mirror. The external cavity provides functions of wavelength selection, dispersion compensation and spatial mode control. The characteristics of the laser under CW or mode-locked operation are described. The dual-wavelength laser output exhibits beat note beyond 7 THz. The tunable multi-terahertz beat frequency is characterized by a non-collinear intensity autocorrelation technique. A dual-wavelength interferometer that uses a tunable dual-wavelength laser as the light source is demonstrated. Finally, theoretical analysis is presented, which demonstrates that the dual-wavelength output of the laser is stable if the modes at the two wavelengths correspond to different array lateral modes.
A simple chemical etching technique for reproducible fabrication of robust scanning near-field fiber probes
(1998-02-01)
Chuang, YH
;
Sun, KG
;
Wang, CJ
;
Huang, JY
;
Pan, CL
A two-step chemical etching procedure has been developed for fabricating probes used by scanning near-field optical microscopy. These probes have two tapered regions which can be reproducibly constructed with a wide range of cone angles. The shape of the probe allows it to be used over sample surfaces with deep and narrow regions. Furthermore, our method can be applied to silica glass fibers which are commercially available. To demonstrate, we used these tips to acquire the near-field optical image of a thin layer of polystyrene spheres. Intensity interference patterns were observed. The demonstrated in-plane resolution was estimated to be about 250 nm. This is mainly limited by the diameter of the metal-coated tip. The transmission efficiency of the tip is better than 10(-4). (C) 1998 American Institute of Physics.
An overview of THz research activities in Taiwan
(2005)
Pan, CL
;
光電工程學系
;
Department of Photonics
Reflecting the flourishing THz science and technology in the past decade, a number of groups in Taiwan have initiated research activities in this area. All major research universities as well as the semi-public Industrial Technology Research Institute are represented. Current research topics include THz devices (emitters, detectors, phase shifters) and the applications of THz time-domain spectroscopy to the study the far-infrared optical properties of various materials. Highlights of recent research activities are outlined.
Arsenic-implanted GaAs: An alternative material to low-temperature-grown GaAs for ultrafast optoelectronic applications
(1998)
Pan, CL
;
Lin, GR
;
光電工程學系
;
Department of Photonics
Arsenic-ion-implanted GaAs (or GaAs:As+), with excess-arsenic-related deep level defects, has recently emerged as a potential alternative to low-temperature molecular-beam-epitaxy (LTMBE) grown GaAs for ultrafast optoelectronic applications. In this paper, we review results of our structural, ultrafast optical and optoelectronic investigations of as-implanted and thermally annealed GaAs:As+. Picosecond photoconductive switching responses are reported for devices fabricated on thermally-annealed low-dose and high-dose implanted GaAs:As+. Novel sign reversals in near-bandgap ultrafast optical responses were observed and explained.
Automatically controlled power equalizer for liquid crystal based optical demultiplexer
(2005)
Lan, YP
;
Lai, YF
;
Pan, RP
;
Pan, CL
;
交大名義發表
Power equalization of four channels for a liquid crystal based demultiplexer by automatically controlling the liquid crystal pixels is demonstrated. The variation between different channels reduced from 10 dB to 0.15 dB.
Broad-band (>= 20 GHz) laser-diode-based optoelectronic microwave phase shifter
(1998-10-01)
Lin, GR
;
Hwang, TS
;
Chuang, YH
;
Wang, SC
;
Pan, CL
We demonstrate a new type of broad-band microwave phase shifter with superior performance at frequencies up to 20 GHz. This is implemented by simply adding an offset voltage prior to the loop filter (LF) in a laser-diode-based digital optoelectronic phase-locked loop (OEPLL), Accurate control of the phase of microwave signals with a continuously tunable range exceeding 640 degrees (similar to 3.6 pi) is achieved. The phase fluctuation and long-term drift of ally desired phase shift are as small as +/-0.4 degrees and 0.08 degrees, respectively, at 20 GHz, The relative phase instability can be maintained within 0.09 degrees while operating in a phase-shift-keying (PSK) scheme, We also demonstrate accurate control of relative phase difference between dual phase-locked microwave sources using the phase shifter. Our results indicate potential application of this broad-band optoelectronic phase shifter in a phased-array antenna system.
Broadly tunable self-starting passively mode-locked Ti : sapphire laser with triple-strained quantum-well saturable Bragg reflector
(1998-11-01)
Shieh, JM
;
Huang, TC
;
Huang, KF
;
Wang, CL
;
Pan, CL
We demonstrate broadband mode-locking of femtosecond Ti:sapphire lasers with a new type of saturable Bragg reflector (SBR). Triple-strained quantum wells with separate and sequential bandgaps were used as the absorbing layer. The saturation fluence was as low as 7 mu J/cm(2). Self-starting sub-100 fs pulses tunable from 768 to 804 nm were generated in a standard X-folded cavity without intracavity tight focusing on the SBR or temperature tuning. The threshold fluence for self-starting mode-locking was 1 mu J/cm(2). (C) 1998 Elsevier Science B.V. All rights reserved.
Broadly tunable self-starting passively mode-locked Ti : sapphire laser with triple-strained quantum-well saturable Bragg reflector
(1998-11-01)
Shieh, JM
;
Huang, TC
;
Huang, KF
;
Wang, CL
;
Pan, CL
We demonstrate broadband mode-locking of femtosecond Ti:sapphire lasers with a new type of saturable Bragg reflector (SBR). Triple-strained quantum wells with separate and sequential bandgaps were used as the absorbing layer. The saturation fluence was as low as 7 mu J/cm(2). Self-starting sub-100 fs pulses tunable from 768 to 804 nm were generated in a standard X-folded cavity without intracavity tight focusing on the SBR or temperature tuning. The threshold fluence for self-starting mode-locking was 1 mu J/cm(2). (C) 1998 Elsevier Science B.V. All rights reserved.
Characterization and reduction of phase noise in passively mode-locked Ti : sapphire lasers with intracavity saturable absorbers
(1998-06-01)
Shieh, JM
;
Liu, SC
;
Pan, CL
;
光電工程學系
;
Department of Photonics
We characterize the phase noises (or timing jitter) of argon-ion-laser-pumped femtosecond Ti:sapphire lasers with intracavity dye saturable absorbers or saturable Bragg reflectors (SBR's). The significance of the finite lifetime of the absorbers is identified for what is the first time to our knowledge. We show that timing fluctuations of the mode-locked lasers can be suppressed significantly by optimization of intracavity gain bandwidth and group-velocity dispersion. A new active stabilization technique, based on the optoelectronic phase locked loop, is also demonstrated. The rms timing jitter (100-500 Hz) of the femtosecond passively mode-locked Ti:sapphire/dye and Ti:sapphire/SBR lasers operating at an average power of 200 mW is reduced to similar to 650 and 290 fs (500 Hz), respectively. (C) 1998 Optical Society of America.
Characterization of optically excited terahertz radiation from arsenic-ion-implanted GaAs
(2001-01-01)
Lin, GR
;
Pan, CL
;
光電工程學系
;
Department of Photonics
This work characterizes the optically excited terahertz (THz) radiation from arsenic-ion-implanted GaAs (GaAs:As+). We observed phase reversal in the emitted THz radiation field after the semi-insulating GaAs substrate was implanted. The peak amplitude of the emitted THz field increased from 25 mV/cm to 100 mV/cm after thermal annealing. This trend confirms the recovery in crystallinity of the as-implanted GaAs :As+ after annealing. By introducing a magnetic field, we observe a blue shift of the center frequency in the THz power spectrum from 0.57 THz for the as-implanted CaAs : As+ to 1 THz for furnace-annealed samples. Analysis of the blue-shifted spectra and unsymmetrical pulse shapes allows us to infer the increasing importance of the contribution of another unknown mechanism to the THz radiation from the GaAs:As+ samples after annealing. This is also explained satisfactorily by the crystallinity of the as-implanted and furnace-annealed GaAs : As+. Further, the effective carrier mobilities of as-implanted, rapid-thermal-annealed, and furnace-annealed GaAs : As+ are determined for the first time as 0.6, 2, and 15 cm(2)/Vs respectively according to the THz data.
Control of enhanced THz transmission through metallic hole arrays using nematic liquid crystal
(2005-05-30)
Pan, CL
;
Hsieh, CF
;
Pan, RP
;
Tanaka, M
;
Miyamaru, F
We demonstrate frequency tuning of enhanced THz radiation transmitted through a two- dimensional metallic hole array ( 2D- MHA) by controlling the index of refraction of the medium filling the holes and adjacent to the 2D- MHA on one side. The medium is a nematic liquid crystal ( NLC) and its index of refraction is varied using magnetically controlled birefringence of the NLC. With the NLC, the peak transmission frequency of the 2D- MHA shift to the red by 0.112 THz and can be tuned from 0.193 to 0.188 THz. The peak transmittance is as high as 70% or an enhancement of 2.42 times, considering the porosity of the 2D- MHA. As a tunable THz filter, this device exhibits a continuous tuning range of 4.7 GHz, a low insertion loss of 2.35 to 1.55 dB and a quality factor of similar to 4- 5. (C) 2005 Optical Society of America.
Control of THz transmission through two-dimensional metallic photonic crystals
(2005)
Pan, CL
;
Hsieh, CF
;
Pan, RP
;
Tanaka, M
;
Miyamaru, F
We demonstrate frequency tuning of resonantly enhanced THz radiation transmitted through a two-dimensional metallic photonic crystal on a liquid crystalline "substrate".