Light Sensing and Ranging (LiDAR) is a widely used technique for reconstructing three-dimensional (3D) scenes in a variety of applications, including augmented reality and virtual reality, automotive, industrial machine vision, earth mapping, planetary science, etc. Recent progresses in 3D stacking technologies provided an important step forward in SPAD or SiPM array development, allowing to reach smaller pitch, higher pixel count and more complex processing electronics. However, these also have certain disadvantages that should be considered in specific applications that as limited dynamic range, afterpulsing, crosstalk, and noise. For example, SiPM exhibit dark counts, which are spurious signals generated in the absence of incident photons. Dark counts contribute to the noise floor of SiPMs and can limit their sensitivity, especially in low-light conditions. Efforts are made to reduce dark counts, but they still exist to some extent. Therefore, we have quantitatively analyzed the limits of SiPM compared to APD in a noisy environment in this paper. For example, when the target size is constant, and the beam size is larger than the object, the SNR (Signal-to-Noise Ratio) of the pulsed signal due to ambient light can be analyzed mathematically.
Non-contact printing methods have recently attracted attention in the field of optoelectronics manufacturing including solar cells, light-emitting diodes, photodetectors, and transparent electrodes. Non-contact printing is a powerful and cost-effective technique for high-precision processing through the direct printing of optoelectronic devices. Multimode optical waveguides which are generally fabricated by lithography or reactive ion etching reported exhibiting minimum losses of 0.02 dB/cm and 0.2 dB/cm, respectively. Although these techniques are well established in the fabrication process, it is complicated and possible only with large-scale equipment. Non-contact printing technique can be used to solve these problems. In this paper, we design and demonstrate the printing of optical waveguides with a flexible substrate. The waveguide width was advanced through the nozzle design within 500 μm and applied to the high voltage and nozzle structure so that the capillary force does not damage the pattern.
Photonic integrated circuits (PICs) have been a very active research area ever since the inception of integrated optics for the application of the wavelength division multiplexing networks. One of the main size limitations to regular integrated optics based circuits is the weak optical confinement. This makes it very difficult to change the direction of optical waveguides in a very short distance with low loss. Photonic band gap based approaches offer promise of compact waveguide size that can be bent over very rapidly. However, wavelength dependence and the fabrication difficulty remain to be the challenges. On the other hand, advances in nanofabrication and full-wave electromagnetic simulation techniques have permitted the design and realization of a wide variety of plasmonic waveguide structures as excellent candidates for future nanoscale electronic-photonic integrated circuits. In this paper, we reported the nano-gap resonator with the straight waveguide without the ring shape resonator, which is replaced with a straight waveguide, metalic layer, and nano-gap. We investigated the resonant properties of the structure using the FDTD method. The results reveal that the proposed structure has the band stop and lasing characteristic.
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, surface plasmon resonance triangular ring resonator (SPR-TRR) Vernier structure based on InP is simulated for index variation from 1.33 to 1.35. Sensing area of SPR-TRR is achieved to make an ultra-compact SPR mirror by deposition of Au film layer which is designed to deposit on vertex of TRR. The possibility of mass production is shown by a deposition of SPR mirror on the triangular ring resonator (TRR). Also, the sensitivity enhancement of an envelope signal for Vernier effect is confirmed by FDTD simulation compared to SPR-TRR. As simulation results, the sensitivity is enhanced 20 nm / RIU to 480 nm / RIU. Thus, SPR-TRR Vernier structure is used for a biosensor to enhance the sensitivity of biosensor.
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.
We investigate the modulation properties of a three-guide coupled rectangular ring laser having bidirectional lasing
characteristics. Two different rectangular lasers having active section lengths of 250 and 350 μm and total cavity lengths
of 580 and 780 μm are fabricated. The rectangular laser cavity consists of four low loss total internal reflection mirrors
and an output coupler made out of three passive coupled waveguides. For both the clockwise and counterclockwise
circulating directions, the lasing threshold currents of around 38 mA are obtained at room temperature under continuous
wave operation. A 3-dB modulation bandwidth over 3 GHz is observed in both circulating directions for two different
lasers.
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 investigated the properties of a triangular microresonator using the total internal reflection (TIR) mirrors with a
long evanescent field around the critical angle. For the sensitivity analysis, we have calculated the mirror offset due to
the Goos-Hänchen effect and the resonance shift of the triangular resonator with the refractive index change of the outer
region in the TIR mirror. The mirror offset is increased up to 0.8 μm for the transverse electric (TE) polarization and
2.0 μm for the transverse magnetic (TM) polarization to the incident angle of 18°. Then, the resonance shift of 417 pm
for the TM polarized light and 34 pm for the TE polarized light were observed, respectively, by changing the refractive
index of 4×10-5. The measured extinction ratio of triangular ring resonator was about 6 dB near 1550 nm, in where the
incidence angle of the TIR mirror inside the resonator was 18°.
We proposed the photonic crystal coupled surface plasmon resonance sensors using gold nano-structure to enhance the
sensitivity of an SPR sensor. The proposed configuration with the photonic crystal structure is Au(Photonic
crystal)/Au/Ag/Cr/Glass. The 20 nm silver film and the 20 nm gold film are layered on the glass substrate. Then, the
dot-like gold photonic crystal structures with a period pitch are patterned on the Au/Ag/Cr/Glass structure. The
reflectance and the optical-mode propagations as a function of incident angle are calculated using the three-dimensional
finite-difference time-domain method. Under this resonance condition, the incident light is highly absorbed and loses a
fair amount of its energy, which results in a dip in the intensity profile of the reflected light. The optimum resonance
angle of 44.5 degrees is obtained in the 75-nm-radius Au photonics crystal structure with a period of 300 nm.
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.
We have proposed a novel biosensor scheme based on a dual photonic crystal microcavity with a stadium-shaped ring resonator (PCM-SSRR) and characterized the resonance conditions for the first time. The Q of the dual PCM-SSRR was significantly enhanced when a single PCM or a dual PCM was in the same resonance condition with the SSRR. We demonstrated a mutual interference between the dual PCM. In this study, the Q of the dual PCM-SSRR was increased three times over that of the directional coupler structure used with the single PCM. Assuming a detectable spectral resolution of 10 pm, a refractive index resolution of 3.03×10-5 can be achieved on the dual PCM-SSRR.
We have proposed a novel all-optical logic gates based on active plasmonics that may control the electron-photon
coupling through an external effect. The phenomenon of surface plasmon resonance (SPR) is basically appeared on
attenuated total reflection mirror block. The waveguide-type Kretchmann-Raether configuration with high sensitivity to
the metal surface was used for all-optical OR and NAND gates. Here, the double thin metal layers can enhance the
confinement of plasmon waves and can be utilized as an output. When the external light source is injected into the thin
ZnO film deposited on the facet of a GaAs waveguide, the total refractive index of the thin ZnO layer is changed by the
nonlinear refractive index. The proposed waveguide-type configuration was analyzed and optimized using finite-difference
time-domain method for all-optical OR and NAND gates. When the external light is injected on the metal
layer, the intensity of SPW is decreased by 10.76 dB. However, the reflected light into the waveguide is increased by
2.23 dB.
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.
Titanium dioxide (TiO2) thin films were prepared by ion-assisted electron-beam deposition on glass at room
temperature and were annealed by rapid thermal annealing in O2 and N2 gas flow. TiO2 thin films annealed in N2 gas
flow are (110) rutile phase and (101) anatase phase, but in O2 gas flow are (110) rutile phase. The optical band gaps of
the TiO2 thin films are increased to 3.281 eV with annealing treatment of 300 ~ 500 °C in O2 gas flow and to 3.271 eV in
N2 gas flow. However, the band gap begins to decrease to 3.277 eV at the annealing temperature of 600 °C in O2 gas
flow and to 3.257 eV in N2 gas flow, respectively.
We proposed the grating coupled surface plasmon resonance (GC-SPR) sensors using ZnO and metallic nanograting
structures to enhance the sensitivity of an SPR sensor. The GC-SPR sensors were analyzed using the finitedifference
time-domain method. The optimum resonance angles of 49 and 55.5 degrees are obtained in the 150 nm wide
grating structure with a period of 300 nm for the ZnO thickness of 30 and 50 nm, respectively. Here, an enhanced
evanescent field is obtained due to the surface plasmon on the edge of the bandgap when the ZnO and metallic grating
structures are used to excite the surface plasmon.
In this paper, we propose a novel sensor structure based on the rectangular ring resonator with the photonic crystal
microcavity (PCM), and optimize the structure using finite-difference time-domain (FDTD) method. This sensor
consists of the rectangular resonator with total internal reflection mirror and the PCM, which can be placed at the nearby
optical waveguide of the rectangular ring resonator. The PCM is composed of a defect cavity with different holes on
the center of it. The Q-factor of the PCM can be significantly enhanced when the PCM has the resonance wavelength.
The PCM can be evanescently coupled to a side waveguide arm of the rectangular ring resonator. The sensitivity of the
ring resonator in the presence of gas or biomolecules composition was calculated using the FDTD method. When the
injected gas or biomolecules pass through the PCM, the variation of effective index due to their concentration affects the
resonance condition of the rectangular ring resonator. We have investigated how the shift of the resonance peak in the
resonance wavelengths depends on the gas or biomolecules concentration. We also have optimized the sensor structure
for the waveguide width and length, the hole radius, and the number of hole on the PCM. The optimum lattice
constants, hole radius, and cavity length are 370, 100, and 580 nm, respectively. The rectangular ring resonator sensor
with microcavity significantly enhances the quality factor and the sensitivity compared to the directional coupler sensor
with PCM. The change of normalized output power in rectangular ring resonator with PCM is approximately twice
larger than the change in directional coupler with PCM.
The Goos-Hanchen (GH) shift is observed from phase transition of the reflected light. However, the reported
Artmann's equation is difficult to apply to drastic phase change of the critical and resonance angles because this equation
is solved by differential of the phase shift. Therefore, the GH shift can be obtained from the structure optimized by the
finite-difference time-domain method. In the surface plasmon resonance (SPR) phenomenon, positive and negative
lateral shifts may result from the variation of incidence angle. The GH shift is very important to exactly detect the output
power of the micro-size SPR sensor. The accurate positive and negative lateral shifts of -0.49 and +1.46 μm are obtained
on the SPR with the incidence angles of 44.4° and 47°, respectively.
We propose a novel micro surface plasmon resonance (SPR) sensor system based on polymer materials. The
proposed SPR system consists of the incident medium with polymer waveguide and the gold thin film for sensing area.
Using a polymer optical waveguide instead of a prism in SPR sensing system offers miniaturization, low cost, and
potable sensing capability. The whole device performance was analyzed using the finite-difference time domain method.
The optimum gold thickness in the attenuated total reflection mirror of polymer waveguide is around 50 nm and the
resonance angle to generate surface plasmon wave is 66 degrees.
The lasing characteristics of three-guide coupled ring lasers using the self-aligned total internal reflection
(TIR) mirrors were investigated numerically and experimentally. The rectangular laser cavity consists of four low loss
TIR mirrors and an output coupler made out of passive three coupled waveguides. Two different lasers having active
section lengths of 250 and 350 μm and total cavity lengths of 580 and 780 μm are fabricated. For both devices lasing
thresholds of 38 mA is obtained at room temperature and under CW operation. Lasing is predominantly single mode
with the side mode suppression ratio better than 20 dB.
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