Browsing by Author "Pan, RP"

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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 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.
Alignment of liquid crystals by ion etched grooved glass surfaces
(2005-12-01)
Lin, YF
;
Tsou, MC
;
Pan, RP
;
電子物理學系
;
Department of Electrophysics
The alignment properies of the nematic liquid crystal (LC) 4'-n-pentyl-4-cyanobiphenyl (5CB) on glass substrates with parallel grooves are studied. The U-shaped grooves with a variety of depths and periods were prepared by the reactive ion etch method. Surface morphology of the grooved glass was, examined by an Atomic Force Microscope. An LC cell consisting of a pair of parallel grooved substrates with 5CB sandwiched in between was assembled. The alignment quality for the LC was studied by measuring its surface azimuthal anchoring strength. The effect of the groove period and depth were studied. Strong anchoring with strengths larger than 10(-5) j/m(2) can be achieved with groove depths of 56 or 121 nm and periods less than 4 mu m.
Analysis of dielectric breakdown patterns in parallel-plate capacitors
(2000-06-01)
Sheu, CR
;
Cheng, CY
;
Wang, PS
;
Lee, CY
;
Pan, RP
The parallel-plate capacitor cells are used as model systems for studying the dielectric breakdown (DB) patterns. Air, a liquid crystal and several kinds of oils are used as the dielectric material sandwiched between the plates. We study the types of patterns formed with different materials, voltages and cell thickness. The fractal dimensions and the conditions for getting each type of DB pattern are obtained for the first time. In addition, the fractal dimensions of patterns simulated by using the active walker model (AWM) are also analyzed and compared with the experimental DB patterns.
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.
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".
Dielectric breakdown patterns and active walker model
(1999-02-01)
Sheu, CR
;
Cheng, CY
;
Pan, RP
;
電子物理學系
;
Department of Electrophysics
Simulations based on the active walker model an used successfully to reconstruct the dielectric breakdown patterns observed in a cell with parallel-plate electrodes. Different types of patterns can be obtained with suitable parameters. These parameters correspond to the electrical and environmental conditions during the breakdown.
Effects of hole material on enhanced terahertz transmission through metallic hole arrays
(2005)
Lo, C
;
Hsieh, CF
;
Pan, RP
;
Pan, CL
;
光電工程學系
Enhanced, multi-peak THz transmission peaks from metallic hole arrays filled with UV-gel are studied. Different SPP-like surface wave modes are identified.
Electrically controlled room temperature terahertz phase shifter with liquid crystal
(2004-02-01)
Tsai, TR
;
Chen, CY
;
Pan, RP
;
Pan, CL
;
Zhang, XC
We present the use of electrically controlled bire-fringence in a nematic liquid crystal cell for phase shifting of electromagnetic waves up to terahertz frequencies. This device. was operated at room temperature and a maximum phase shift of 4.07degrees was demonstrated at 1.07 THz when the interaction length was 38.6 mum. The driving voltage and corresponding field were 176.8 V (rms) and 589.3 V/cm, respectively.
Electronically tunable single and multiple wavelength broad-area semiconductor laser by using a liquid crystal pixel mirror
(2000)
Pan, RP
;
Lu, WL
;
Sheu, CR
;
Pan, CL
;
電子物理學系
Fine-tuning of a diode laser wavelength with a liquid crystal intracavity element
(2004-01-01)
Lan, YP
;
Chen, CY
;
Pan, RP
;
Pan, CL
;
電子物理學系
A novel and simple approach for fine-tuning a laser wavelength is proposed and demonstrated. The key element is a planarly aligned nematic liquid crystal (NLC) cell inserted between the grating and end mirror of an external-cavity semiconductor laser (ECL). Varying the voltage driving the NLC cell, causes its extraordinary index of refraction to change due to field-induced reorientation of the LC director. This is equivalent to tuning the laser cavity length. As a result, the laser wavelength can be continuously tuned. With a 35.5-/mum-thick NLC cell, the output frequency of the present laser can be continuously tuned over 4 GHz. The root mean square driving voltage required is 1.5 V or less. The tuning range is in good agreement with the theoretical predictions. (C) 2004 Society of Photo-Optical Instrumentation Engineers.
Intracavity measurement of liquid crystal layer thickness by wavelength tuning of an external cavity laser diode
(2005-10-03)
Lan, YP
;
Lin, YF
;
Li, YT
;
Pan, RP
;
Lee, CK
The gap of a planar-aligned liquid crystal (LC) cell is measured by a novel method: Monitoring the change in output wavelength of an external-cavity diode laser by varying the voltage driving the LC cell placed in the laser cavity. This method is particularly suitable for measurement of LC cells of small phase retardation. Measurement errors of +/- 0.5 % and +/- 0.6 % for 9.6-mu m and 4.25-mu m cells with phase retardations of 1.63 mu m and 0.20 mu m respectively are demonstrated. (c) 2005 Optical Society of America.
Liquid-crystal-based terahertz tunable Lyot filter
(2006-03-06)
Chen, CY
;
Pan, CL
;
Hsieh, CF
;
Lin, YF
;
Pan, RP
A two-element tunable Lyot filter operating in the terahertz (THz) frequency range is demonstrated. The central bandpass frequency of the filter can be continuously tuned from 0.388 to 0.564 THz (a fractional tuning range of 40%) using magnetically controlled birefringence in nematic liquid crystals. The transmission bandwidth is 0.1 THz and the insertion loss of the present device is 8 dB due to the scattering of LC molecules in the thick LC cells. This filter can be operated at room temperature. (c) 2006 American Institute of Physics.
Liquid-crystal-based tunable filter for WDM (lambda=1550 nm)
(2004)
Pan, CL
;
Huang, MJ
;
Pan, RP
;
電子物理學系
;
李立台揚網路研究中心
We report a new configuration of tunable optical filter for DWDM applications. In this design, first-order diffracted signal light by a grating is directed to a lens and focused on to a transmission-type liquid crystal spatial light modulator (LC-SLM). Wavelength channels are selected by opening the appropriate pixels of the LC-SLM for transmission. Filtering into 15 channels of the 1550 nm band is demonstrated in the initial experiment. The channels are designed according to the International Telecommunication Union (ITU) grid with channel spacing of 100 GHz. Channel crosstalk is less than -30dB. The average I dB, 3 dB, and 30 dB passbands of the filter are 0.07 nm, 0.13 nm, and 0.91 nm, respectively. The extinction ratio can be as high as 24.7 dB.
Liquid-crystal-based tunable optical filtering devices for DWDM
(2001)
Pan, RP
;
Tung, XX
;
Chen, JY
;
Huang, MJ
;
Pan, CL
We report a new configuration of tunable optical filter for DWDM applications. In this design, first-order diffracted signal light by a grating is directed to a lens and focused on to a transmission-type liquid crystal spatial light modulator (LC-SLM). Wavelength channels are selected by opening the appropriate pixels of the LC-SLM for transmission. The device is demonstrated by using a broad-band AR-coated laser diode (lamda = 800 nm) as the signal light. For conceptual demonstration, we use optical fibers with a core diameter of 50 microns instead of the LC-SLM. A total of 37 channels, spanning 33.6 nm were successfully selected with channel spacing of 0.94 nm and bandwidth of 0.4 nm. With 100 micron-wide pixels separated by 5 microns in the LC-SLM and a 1800 lines/mm grating, we show selection of five channels with channel spacing of 0.78 nm. The bandwidth is 0.43 nm. The channel isolation is better than 20 dB. At a wavelength of 1.5 micron, channel spacing as small as 12.4 GHz can be realized. This device is also expected to be useful for other DWDM applications, e.g., switching and routing.
Magnetically tunable room-temperature 2 pi liquid crystal terahertz phase shifter
(2004-06-14)
Chen, CY
;
Hsieh, CF
;
Lin, YF
;
Pan, RP
;
Pan, CL
Tunable phase shift up to 360degrees at 1 THz is achieved with a liquid crystal (LC) device. The key to this design is (1) the use of a nematic LC, E7, which exhibits a birefringence of similar to0.17 (0.2-1.2 THz); (2) a LC cell (3-mm in thickness) with sandwiched structure to increase the interaction length while minimizing interface Fresnel losses; and (3) the use of magnetic field to align the thick LC cell and achieve continuous tuning of phase from 0 to 360degrees. This device can be operated over a broad range near room temperature. (C) 2004 Optical Society of America.
Mode-hop-free fine tuning of an external-cavity diode laser with an intracavity liquid crystal cell
(2004-03-01)
Lan, YP
;
Pan, RP
;
Pan, CL
;
電子物理學系
;
光電工程學系
A planar nematic liquid crystal (NLC) cell is incorporated into a Littman-type external cavity as the wavelength-turfing device for a semiconductor laser diode. By varying the driving voltage of the NLC cell and laser diode bias current simultaneously, we demonstrate single-mode oscillation and mode-hop-free tuning over 19.2 GHz at 775 nm. The result is in good agreement with the theoretical predictions. (C) 2004 Optical Society of America.
Multimode optical demultiplexer for DWDM with liquid crystal enabled functionalities
(2004-10-01)
Huang, MJ
;
Pan, RP
;
Sheu, CR
;
Lan, YP
;
Lai, YF
We have developed a liquid-crystal-based multimode optical demultiplexer (DEMUX) with additional functionalities such as switching and power equalization. Demultiplexing 16-channel 100-GHz-spaced signals into a 62.5-mum multimode-fiber array is demonstrated. The central wavelength of each channel is designed according to the International Telecommunication Union grid. Adjacent channel crosstalk is less than -30 dB. The average 1- and 3-dB passbands of the DEMUX are 12.5 and 22.5 GHz, respectively. A maximum extinction ratio of 16.2 dB is achieved. Different channels can be switched with rise and fall times of similar to10 and similar to70 ms, respectively. The outputs of the channels are equalized to -65 dBm. The variation between different channels reduced from similar to10 dB to less than 0.5 dB.