A surface plasmon resonance (SPR) sensor hybridized with self-assembled metallic nanoparticles is proposed and experimentally demonstrated. The measured sensitivity of the proposed SPR sensor is 110.77 deg/RIU, while that of a conventional SPR sensor is 84.75 deg/RIU. The enhanced sensitivity is attributed to the strong localized surface plasmons and the increased surface interaction area by the nanoparticles. Angle variation measurement, which is an easy detection method using bulk optics, is possible with this structure because a supplementary metallic thin film layer on the nanoparticles leads to utilization of the sensitive variation of the strong localized field by the change of the refractive index. Furthermore, the proposed structure can be fabricated with a very simple three-step nonlithographic process.
In this paper, an effective quality-factor is analyzed for asymmetric Mach-Zehnder interferometer (AMZI) with ring resonator sensor. The device is designed with AMZI to interference with the optical input of the ring resonator based on silica semiconductor process. The design of device satisfy a critical resonance at out of phase condition through asymmetric power split ratio. According to operation principle of Mach-Zehnder interferometer, the critical resonance occurs when the power passing through asymmetric arm is in a range of ring resonator power variation. Our simulation shows that the Q-factor of the device is enhanced from 1161.9 to 5342.5 if a RR is coupled to an arm of AMZI.
In this paper, we propose a surface plasmon resonance (SPR) sensor with metallic nano-particles, which is based on the
Kretschmann configuration for reflective-type measurement with enhanced sensitivity. The proposed structure is
analyzed and compared with a conventional Kretschmann configuration by using 3D finite-difference time-domain
method. The proposed structure is composed of semi-spherical nano-particles and a thin cladding layer. The evanescent
field on the metallic structure is enhanced by the factor of 2.7, where the diameter of nano-particles, fill factor, and
thickness of cladding film layer TF are 30 nm, 50 %, and 40 nm, respectively. On the other hand, the enhancement of the evanescent field in the conventional SPR sensor is 1.7 for the same TF. Because of the enhanced evanescent field, the
sensitivity of our proposed sensor is maximized to 137.1 degree/RIU while that of a conventional SPR sensor is 99.6
degree/RIU.
A novel polarization rotator with asymmetric optical waveguide based on plasmonics is proposed and analyzed for the
first time. The polarization rotator using skewing effects at the slotted optical waveguide (SOW) with metal film was
designed by 3D-FDTD method. A metal film on the waveguide acts to rapidly rotate the optical polarization, because the plasmonic characteristics of a metal film can induce the slow group velocity through the metal-clad optical waveguide. Here, the optical waveguide with a buffer layer is proposed to reduce the propagation loss. The polarization rotator length of 6 μm is among the shortest reported in the waveguide-type polarization rotators. The polarization conversion efficiency of 98.93 % is observed near 1550 nm along with a propagation loss of -0.43 dB. The proposed structure is smaller than previous polarization rotator with asymmetric optical waveguide and is more effective to control polarizations using by plasmonic effects.
In this paper, we have designed and optimized the metallic nano-structures on a conventional surface plasmon resonance (SPR) sensor which induce the localized surface plasmon resonance for an improved sensitivity. Designed SPR sensor was simulated with 3D Finite-difference time-domain method. The sensitivity is maximized to 130.9 degree/RIU when the thickness of film layer TF is 30 nm while that of a conventional SPR sensor is less than 99.6 degree/RIU, and the reflectivity is minimized when TF is 25 nm. The most appropriated diameter of particles is about 35 nm for high sensitivity.
We introduce an ultra-sensitive integrated photonic sensor structure using silicon on insulator based triangular resonator, in which a surface plasmon resonance (SPR) gold film is applied on a total internal reflection mirror. We have analyzed and optimized the triangular resonator sensor structure with an extremely small SPR mirror sensing area. Due to the large phase shift in the SPR mirror, a significantly enhanced sensitivity of 800 nm/RIU (refractive index unit) and the maximum peak shift of half free spectral range have been obtained at the SPR angle of 22.65° with Au thickness of 35 nm for the change of the refractive index Δn = 1x10-3.
In this paper, we have theoretically analyzed and designed a 1D PhC microcavity sensor with SPR based on the total
internal reflection mirror using analytic calculation and FDTD methods. The proposed structure has many advantages.
One of that is a high sensitivity using SPR characteristics. Another is a high Q-factor of the characteristics in the PhC
microcavity structure. The incident light has double resonance characteristics, because the filtered light by PhC structure
is met the thin metal film for SPR effect. We have also observed the change of resonance characteristics according to the
variation of effective index on the metal film.
In this paper, we have demonstrated a metallic nano-structured SPR sensor for an improvement of biosensing
sensitivity using a metallic nano-structure. Permittivity of metal is calculated with Drude model for analysis. The
sensitivity of SPR sensor with metallic nano-structure is 65 degree/RIU, and that of conventional SPR configuration is
54.8 degree/RIU. We have fabricated the random metallic nano-structures on the metallic thin film using the RIE etching
process. Moreover, we have analyzed the structure using the finite-difference time-domain method for the exact
characteristic.
An integrated surface plasmon resonance (SPR) array sensor using wideband sources and a different incident angle
with a single fluidic channel in order to increase the sensitivity is proposed and analyzed. The SPR reflectance was
analyzed using the finite-difference time-domain gaussian source method. The maximum difference is shown at the
incident angle of 24.6°. The sensitivity of the resonance shift used to change the refractive index of 1x10-3 is 51000
nm/RIU at the wavelength interrogation. The extremely small integrated SPR array sensor is a very attractive
component because of its promise of a high level of sensitivity, its easy measurement process, and its ease of integration
into a sensor system.
Recently, the bending efficiency of vertical slot waveguide with different structure has been analyzed. However, the
interface roughness of the waveguide which have high E-field intensity induces to high scattering loss. In addition, a
vertical slot fabrication involves in a very narrow region etching which can cause large roughness in the vertical
interfaces. In order to reduce the propagation loss and facilitate the fabrication process, horizontal slot waveguides have
been proposed and fabricated, recently. In this paper, we have designed and analyzed total internal reflection (TIR)
mirror for using a resonator based on horizontal slot waveguide. Our proposed structure is consisted horizontal slot
waveguide of rib type to enlarge contact region with TIR mirror. To analyze Goos-Hänchen shift, we have theoretically
calculated length of evanescent field at TIR mirror using 3D-FDTD method. The presented TIR mirror loss analysis can
be applied to enhance the efficiency of horizontal slot waveguide resonator which can potentially be used in many
silicon based optoelectronic devices.
We have proposed and analyzed high sensitivity and high Q-factor triangular ring resonator (TRR) with a total internal
reflection (TIR) mirror in silicon-on-insulator (SOI) -based slot waveguide. Different from the conventional integrated
optical devices such as waveguide, bend, splitter, and filter, in which the light is guided in high-index medium by the
total internal reflection, the slot waveguide confines the E-field in the low-index region by way of strong discontinuities
at the interface between the low-index core and the high-index claddings. Because the waveguide using these
characteristic has a lower effective index than high-index waveguide, the TRR have been achieved high sensitivity, in
which the long evanescent fields on a TIR mirror. Optical quality factor of up to 9.461x102 is calculated in such filters,
and the sensitivity of the resonance shift for changing the refractive index of 1x10-4 at the incidence angle of 34.11° has been identified as high as 1.02x105 nm/RIU.
In this paper, we propose a plasmonics-based optical polarization rotator. The proposed structure consists of a slotted
waveguide and a metal film. The proposed device is designed using skewing phenomena of propagation waves at the
slotted waveguide with metal film by 3D-FDTD method. We have analyzed various structures such as a slotted
waveguide, a metal-clad optical waveguide, and a metal-clad optical waveguide with buffer layers. A metal film on the
waveguide acts to rapidly rotate the optical polarization, because it has characteristics of slow group velocity according
to the metal-clad optical waveguide. Therefore, an ultra-small sized polarization rotator can be realized by the
plasmonics-based asymmetric cross sections of waveguides. The length of designed polarization rotator is just 5 μm for
80% polarization rotation ratio.
In this paper, we propose an integrated photonic sensor structure using triangular ring resonator (TRR), in which
surface plasmon resonance (SPR) is combined for the enhancement of sensitivity. In our previous experimental work on
TRR without SPR, we have shown that the Q-factor and the sensitivity of the resonance shift were approximately 7×102and 8.4 nm/RIU, respectively, near 1550 nm. By employing a thin-metal layer for SPR at the total-internal-refection
mirror in TRR, we have obtained significantly enhanced sensitivity of the resonance shift up to 55 nm/RIU maintaining
similar Q-factor.
In this paper, we propose an all optical logic gate based on a photonic crystals multimode interference (PC-MMI).
The all optical logic gate with multifunctional performance has been designed theoretically in two-dimensional photonic
crystals (PhCs) structure using multimode interference (MMI) principle. The PhCs consist of periodical air holes in
silicon-on-insulator structure. The MMI using line defect waveguide is a 3×3 structure on the PhCs. By switching the
optical signal to different input waveguide ports, the device can operate as NAND, NOT, NOR, and OR gates
simultaneously or individually. In our optimum design, the width of MMI section is 4.8 μm and the length is 64 μm.
The spacing between two line-defect waveguides is 1.2 μm. The total length of the device is 70 μm with an input length
of 3.2 μm. It is 1/10 smaller size than conventional MMI optical logic device with nearby 1 mm. Therefore,
switching speed is also enhanced by the reduced device size. Our proposed structure would be very useful for
construction of optical circuit, optical computer, and future Si-based optical integrated circuits.
KEYWORDS: Intermodulation, Modulation, Semiconductor lasers, Transmitters, Radio optics, Radio over Fiber, Signal detection, Nonlinear optics, Phase shifts, Telecommunications
In typical radio-over-fiber (RoF) systems, sub-carrier multiplexing is achieved by using directly modulated laser diode
(LD). However, the conventional LD for optical communication system has non-linear characteristics such as, 3rd order
intermodulation distortion (IMD3), which degrade overall analog RoF system performance. In addition, when the
multi-channel input signals are modulated directly, 5th order intermodulation distortion (IMD5) signals act as a noise on
overall systems. In this paper, we experimentally demonstrate an opto-electrical predistortion optical transmitter to
enhance IMD3 & IMD5 for radio-over-fiber systems. To reduce the 3rd and 5th order intermodulation (IM3 & IM5),
master laser diode (MLD) and slave laser diode (SLD) with similar performance are used, and the matching circuits of
two LDs are designed with equal properties. The amplitude and phase balances as well as bias current of two LDs are
carefully considered for the enhancements. The experimental results show that reductions of about 30 dB in the IM3
and about 12 dB in the IM5 are achieved at 2.2 GHz.
KEYWORDS: Semiconductor lasers, Signal detection, Attenuators, Modulation, Phase shifts, Intermodulation, Signal generators, Radio over Fiber, Distortion, Transmitters
We propose and demonstrate a pre-distortion method for reducing the third-order intermodulation distortion (IMD3) of
the distributed-feedback laser diode. The pre-distortion scheme consists of two loops and uses two laser diodes (LD), a
photodetector (PD), RF attenuators, RF combiners/dividers, and an RF amplifier. In our scheme, the error signal is
generated by the slave LD through controlling the phase and attenuation adjustment in the inner loop and then drives the
master LD to reduce nonlinear property in the outer loop. The experimental results show that the significant reduction
of about 30 dB in the third-order intermodulation distortion (IMD3) is achieved at 2.4 GHz in the implemented system.
For the broad frequency range from 1.97 GHz to 2.48 GHz (510 MHz), IMD3 is enhanced by more than 10 dB.
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