We propose a design for silicon-on-chip integrated eight-channel wavelength division multiplexing (WDM) demultiplexer, which consists of parallel-arrayed one-dimensional (1-D) photonic crystal nanobeam cavities (PCNCs) with high-Q over 105 and large free spectral range of ∼200 nm. To the best of our knowledge, this is for the first time that a 1-D PCNC-based demultiplexer is presented. The performance of the device is investigated theoretically by using three-dimensional finite-difference time-domain method. To enable eight-channel parallel arrayed 1-D PCNCs to be coupled to on-chip optical networks for higher integration and multiplex application, an 1 × 8 taper-type equal optical power splitter is used to connect all channels simultaneously. The total device footprint is as small as 12 μm × 15 μm (width × length), which is decreased by five times compared to that per channel in the recent two-dimensional (2-D) PC-based demultiplexer. Moreover, the average channel spacing smaller than 115 GHz is achieved, which is more than two times smaller than that of 2-D PC nanocavity devices, demonstrating that the arrayed nanocavities have the potential for developing ultracompact 100-GHz spaced filters in a dense WDM system. Thus, we believe that the results demonstrated in this work is promising for the future on-chip photonics integrated circuits and optical communication systems.
Recently, due to its superior characteristics and simple manufacture, such as small size, low loss, high sensitivity and convenience to couple, the optical fiber sensor has become one of the most promising sensors. In order to achieve the most effective realization of light propagation by changing the structure of sensors, FOM(S •Q/λres) ,which is determined by two significant variables Q-factor and sensitivity, as a trade-off parameter should be optimized to a high value. In typical sensors, a high Q can be achieved by confining the optical field in the high refractive index dielectric region to make an interaction between analytes and evanescent field of the resonant mode. However, the ignored sensitivity is relatively low with a high Q achieved, which means that the resonant wavelength shift changes non-obviously when the refractive index increases. Meanwhile, the sensitivity also leads to a less desirable FOM. Therefore, a gradient structure, which can enhance the performance of sensors by achieving high Q and high sensitivity, has been developed by Kim et al. later. Here, by introducing parabolic-tapered structure, the light field localized overlaps strongly and sufficiently with analytes. And based on a one-dimensional photonic-crystal nanofiber air-mode cavity, a creative optical fiber sensor is proposed by combining good stability and transmission characteristics of fiber and strengths of tapered structure, realizing excellent FOM ~4.7 x 105 with high Q-factors (Q~106) and high sensitivities (<700 nm/RIU).
Recently, Fano-resonance photonic crystals (PhC) have been employed within a wide variety of nanophotonic structures for different applications, including imaging, filtering, switching, sensing, and so on. In this paper, we propose a convenient and compact fiber-optic sensor based on optical fiber-tips integrated with Fano-resonance pillar-array PhC. The quality factor 1.04×104 and refractive index sensitivity of 226 nm per refractive index unit (RIU) have been demonstrated. In addition, the proposed Fiber-PhC integrated senor structure can be used for nanoparticle detection by checking the reflection spectrum shift with a narrow line-width. Using this method, we demonstrate that the detection of polystyrene nanoparticles with dimensions down to 50 nm in radius can be achieved. Thus, we believe that the design and results presented here are promising and enable the implementation of simple but functional fiber-optic sensors and devices.
A novel ultra-compact one dimensional (1D) photonic crystal (PC) nanobeam integrated sensor (1D PC NIS) is presented in this work, which is formed by series-connected 1D PC nanobeam bandstop filter (1D PC NBF) and 1D PC nanobeam cavity sensor (1D PC NCS). 1D PC NBF is based on an array of the same rectangular grating, with the photonics bandgap (PBG) range for 1538nm~1763nm. 1D PC NCS consists of a 1D PC nanobeam cavity, with the circle air-hole radius parabolically decreasing. By connecting these two parts above, the resonance within the stop band of 1D PC NBF will be filtered out, only the goal resonance used for refractive index sensing is left. Resonance wavelength position of the goal resonance remains the same basically. A high Q-factor of above 1.43×103 and a high sensitivity of 127.07nm/RIU can be obtained simultaneously, which agrees well with the 122.07nm/RIU obtained above without filter. Moreover, benefiting from the ultra-compact size (0.7μm×11μm), 1D PC NIS proposed in the paper is promising to be used for sensors array and multiplexed sensing.
The broadband and low-power optical bright soliton propagation in a line-defect photonic crystal waveguide (PCW) is obtained. The line-defect PCW is composed by polystyrene background material and Si-rods. By adjusting the PCW structure parameters, optical bright soliton in the optimized PCW structures with a bandwidth of 2.35 nm/3.61 nm and a peak power as low as 8.1 μW/35.7 μW is achieved. For a dense wavelength division multiplexing system with 0.2 nm of channel spacing in optical fiber communications, 8 and 16 channels can be supported within the 2.35-nm and 3.61-nm bandwidths. The peak power range is within the power range of the optical fiber communication criterion.
A new method to optimize transmission of photonic crystal filter composed of coupled cavities is proposed. This method can improve transmission without changing 3 dB bandwidth and it is achieved by shifting the defect rods in two cavities centripetally to shorten the distance between energy distribution centers within two cavities. Finally, an ultra compact four-channel demultiplexer is demonstrated by using this optimization method, and this device satisfies the coarse wavelength division multiplexing standard of ITU-T G.694.2 with transmission 99% for each channel.
A microdisplacement sensor formed by a fixed and mobile hole-array based slot photonic crystal (slot-PhC) components is demonstrated. The sensing technique is based on a nanoscale cavity with a high-Q factor in photonic crystals (PhCs). The high-Q nanocavity (H0-cavity) is formed by only laterally shifting two adjacent holes outwards slightly in the opposite direction. The properties of the microdisplacement sensor are analyzed theoretically and simulated using the finite-difference time-domain method. The simulation results indicate that with a proper operating frequency, a quasilinear measurement of microdisplacement is achieved with a sensitivity of 1.0a−1 (a is the lattice constant) in the sensing range between 0.00a and 0.20a. Although other researchers such as Xu et al.1 who demonstrated a micro displacement sensor possessing an equivalent sensitivity, the Q factor is only 40. In this paper, combined with harmonic analysis, we show numerically that an intrinsic Q value of up to 6×103 is achieved. In addition, it is worth mentioning that when the parameters of the H0-cavity are determined, the resonant frequency of the H0-cavity remains approximately constant as the mobile PhC segment shifts along the common axis. It will be easier and more accurate for measurements in practical applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.