Browsing by Author "Chuang, YH"

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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.
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.
Nonoptical tip sample distance control for scanning near-field optical microscopy
(1996-11-25)
Chuang, YH
;
Wang, CJ
;
Huang, JY
;
Pan, CL
;
光電工程研究所
We propose and demonstrate a novel nonoptical technique for regulation of tip-sample distance in a scanning near-field optical microscope (SNOM). The fiber tip for the SNOM is attached to one prong of a quartz tuning fork. The fork is dithered with a gated sinusoidal signal. The vibration of the freely oscillating fiber tip, which manifests as the induced piezoelectric voltage on the fork electrodes, is monitored during the half-period of the gated sinusoid for which the fork is not driven. The time-multiplexing scheme, thus, allows the tuning fork to serve as a dither and a sensor with high Q factor, simultaneously. The gating technique could also potentially allow the SNOM to be used for the investigation of surface relaxation dynamics with high spatial resolution and submillisecond time resolution. (C) 1996 American Institute of Physics.
Nonoptical tip sample distance control for scanning near-field optical microscopy
(1996-11-25)
Chuang, YH
;
Wang, CJ
;
Huang, JY
;
Pan, CL
;
交大名義發表
We propose and demonstrate a novel nonoptical technique for regulation of tip-sample distance in a scanning near-field optical microscope (SNOM). The fiber tip for the SNOM is attached to one prong of a quartz tuning fork. The fork is dithered with a gated sinusoidal signal. The vibration of the freely oscillating fiber tip, which manifests as the induced piezoelectric voltage on the fork electrodes, is monitored during the half-period of the gated sinusoid for which the fork is not driven. The time-multiplexing scheme, thus, allows the tuning fork to serve as a dither and a sensor with high Q factor, simultaneously. The gating technique could also potentially allow the SNOM to be used for the investigation of surface relaxation dynamics with high spatial resolution and submillisecond time resolution. (C) 1996 American Institute of Physics.