Browsing by Author "Huang, MJ"

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Liquid-crystal-based tunable filter for WDM (lambda=1550 nm)
(2004)
Pan, CL
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Huang, MJ
;
Pan, RP
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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.
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.
Wavelength tunable semiconductor laser with a liquid crystal pixel mirror
(2002)
Pan, RP
;
Tung, HC
;
Sheu, CR
;
Pan, CL
;
Huang, MJ
Tunable semiconductor lasers are compact, versatile sources used extensively in dense-wavelength-division-multiplexing (DWDM) optical communication systems, precision metrology, environmental monitoring, and laser spectroscopy. We have developed a twisted nematic liquid crystal device, the liquid crystal pixel mirror (LCPM), successfully as electronically tunable spectral filters for wavelength selection in external cavity semiconductor lasers. In this talk, we report recent advances in this class of electronically tunable single- and multiple-wavelength semiconductor lasers at 650 and 830 nm. Preliminary results of operating the laser at 1.5 microns will also be shown. The laser output can be locked to the ITU grid at 100 GHz intervals. Output power of the laser is as high as several hundred milliwatts, with a tuning range of several tens of nanometers. The laser can be operated either in the continuous-wave (CW) or mode-locked configuration. The linewidth of the laser in the free-running CW mode is about 30 MHz. Fine-tuning of the cw output wavelength can be achieved by changing the driving voltage to the desired pixels of the LCPM. In the mode-locked configuration, the laser design allows intra-cavity dispersion compensation and pulse compression.
Wavelength tuning and multiple wavelength generation using a reflection-type liquid crystal spatial light modulator
(2001)
Pan, RP
;
Shieu, CR
;
Lu, WL
;
Huang, MJ
;
Pan, CL
A reflection-type spatial light modulator using twisted nematic (TN) liquid crystal (the liquid crystal pixel mirror or LCPM) is employed to realize a new type of digitally tunable, narrow line-width (< 0.1 nm, instrument-limited), multiwavelength semiconductor laser. The laser is based on a novel folded telescopic grating-loaded external cavity with LCPM at the focal plane of the folded telescope. With a 50-pixel LCPM, the single wavelength digitally tunable range of a visible laser diode was from 650.8 to 661.24 nm in 0.21 nm steps by biasing the individual pixels. Further, the wavelength can be switched and reset with a response time of 13.6 ms. By biasing two pixels at the same time, obtain dual-wavelength output with the wavelength tunable from 0.21 to 10.4 nm. Generation of tunable triple wavelengths with equal or arbitrary wavelength separation are also demonstrated. Preliminary results on such a laser operating at 1550 nin is also shown.