Search

In this paper, a characterization process of benzocyclobutene (BCB 4024-40) polymer and its realization into optical devices are described. By using the prism coupling technique, the polymer film thickness for various coating speed and the refractive index have been measured. Based on these results, the optical waveguides and couplers have been fabricated using the wet-chemical etch processing technique to take advantage of the photosensitive nature of the polymer. By adopting the multimode interference technique (MMI), the fabricated 2 × 2 optical cross couplers have been testified to demonstrate a maximum crosstalk of −17.81 dB and maximum loss of 3.37 dB.

We present a systematic study of two-ring-one-bus (2R1B) and two-ring Mach-Zehnder interferometer (2RMZI). By exciting the cavity modes in certain ways, it is possible to shape the transmission spectrum that may be suitable for specific applications, such as relaxation of critical coupling for the case of 2R1B or finesse enhancement for the case of 2RMZI. The deteriorating effects of resonator self-coupling known as coupling-induced resonance frequency shift is quantized. The two-ring structures are demonstrated on a silicon-on-insulator platform where good agreement is obtained between the experiment and the theory.

We present a pole-zero analysis, based on the transfer matrix method, for ring resonator (RR)-based filters of Type I and Type II, consisting of mutually coupled and side-coupled RRs. The pole-zero plot determines the filter spectral characteristics and is determined primarily by the coupling coefficient between the resonators. The pole-zero dynamics (or root locus) shows how the poles and zeros move in the complex frequency plane as we vary the coupling coefficient. We show that the pole-zero dynamics for the two types of filter are complementary and, furthermore, that the pole-zero plots are related to the conditions of critical coupling and oscillation in the presence of loss or gain. We also show a pole-zero analysis for the apodization of these filters based on an actively tunable Mach-Zehnder-type coupler, where it is shown that apodization corresponds to designing pole-zero pairs with wide separations, whereas the required bandwidth determines the specific values of the coupling coefficient.

A 1310 and 1550 nm coarse wavelength multi/demultiplexer based on benzocyclobutene (BCB 4024-40) polymer is demonstrated for the first time. The device is designed based on a combination of general interference and paired interference mechanisms of multimode interference (MMI). It is fabricated on BK7 glass substrate with a thin layer of SiO2 as cover. A cost effective chemical etching technique is used in the fabrication process to take advantage of the photosensitive nature of the polymer. The device length was significantly reduced by adopting the restricted multimode interference scheme, lower beat length ratio and cascaded MMI couplers. The measured crosstalk at 1310 nm was 14.4 dB and at 1550 nm was 20.6 dB. The measured insertion loss is around 3.2–3.5 dB for both ports.

We propose a two-ring resonator configuration that can provide optical switching with both high extinction ratio (ER) and low switching threshold. The achievable input threshold is n2IIN ~ 10−5 or smaller, which is one order lower than that of the conventional one-ring configuration, while maintaining an ER of at least 10dB over a 10-GHz (0.1 nm) optical bandwidth. This performance is enabled by using an asymmetric Fano resonance as opposed to the usual symmetric resonance. The low switching threshold and the high ER are related to the sharpness and the asymmetricity of the Fano resonance, respectively.

We propose for the first time, a newly configured device based on nested-ring Mach-Zehnder interferometer structure (NRMZI). The device is capable of generating a box-shaped spectral response approaching an ideal filter due to the double-Fano resonances that arise from multiple interference within the nested-ring as well as that within the MZI. It may be considered as the integrated-optic analog of a reflection or diffraction grating, and as with grating, can be used efficiently as a filter, sensor, or switch at the appropriate operating wavelengths.

A novel 1 A— 2 multimode interference (MMI) optical wavelength filter for 1310 and 1550 nm operation based on photodefinable BenzoCyclobutene (BCB 4024-40) polymer is demonstrated. The device is fabricated on BK7 glass substrate with thin layer of SiO2 as cover. A cost effective chemical etching technique is used in the fabrication process to take advantage of the photosensitive nature of the polymer. The filter length is significantly reduced by adopting the restricted MMI scheme, lower beat length ratio, and cascaded MMI couplers. At 1550 nm filtering operation, the measured crosstalk is -20.6 dB and at 1310 nm filtering is -14.4 dB. The measured insertion loss is around 3.2-3.5 dB for both ports.

We report an optimized room-temperature etching recipe for Indium Phosphide (InP) based on the inductively coupled plasma (ICP) reactive-ion etch using Cl 2 /CH 4 /H 2 gasses. The process was optimized using design of experiment (DOE) (Taguchi method). The results, in terms of etch rate, surface roughness and etched profile, are compared with the more conventional CH 4 /H 2 without chlorine. The Cl 2 -based recipe does not require substrate heating and thus can be more cost effective and widely applied. The Cl 2 /CH 4 /H 2 process generally gives a reasonable higher etch rate (as high as 848 nm/min) and cleaner surface with no polymer formation, but it requires a high ICP power. The CH 4 /H 2 process produces lower etch rate (with possibly polymer contamination), but smoother surface and better structural verticality at a lower ICP power. Both processes give very good selectivity against the silicon dioxide (SiO 2 ) mask. The selectivity of InP against oxide mask (up to 35:1) for the Cl 2 /CH 4 /H 2 process is one of the highest reported so far. The etched structure possesses good verticality and good surface quality comparable to that obtained under elevated temperature condition (>200 °C).

In this paper, we report the fabrication of rib waveguides and passive waveguide devices such as multimode interference (MMI) splitters using sol–gel organic–inorganic hybrid materials. The multilayered waveguides were developed, using spin-coating and photolithography processes. Optical coupling using lasers of 632.8-, 780- and 1550-nm wavelength was conducted by direct fiber end-face coupling to polished waveguide faces. Coupling between waveguides with different separations was studied using groups of identical waveguides. Waveguide propagation loss was characterized using the cutback method, revealing an average loss of 0.3–0.4 dB/cm at 780 nm. MMI effects were detected with 1×2 and 1×4 MMI splitters.

In metalorganic vapor-phase epitaxy (MOVPE) growth of III–V semiconductor compounds and device structures, arsine (AsH3) and phosphine (PH3) are normally used as group V precursors and hydrogen is used as the carrier gas, which is very toxic and has safety hazard. In this contribution, MOVPE growths of Al-free 808 nm high power diode lasers by using metalorganic (MO) group V sources, TBAs and TBP, and nitrogen as carrier gas has been reported. InGaAsP/InGaP/GaAs single quantum well (SQW) high power laser structure emitting at 808 nm has been adopted to characterize the material quality. Broad area stripe lasers with the stripe width of 150 μm have been fabricated from the wafers grown by the MOVPE using MO group V sources. Lasing of the device with threshold current density of 506 A/cm2 has been successfully achieved.

The inductively coupled argon (Ar) plasma-enhanced quantum-well intermixing has been investigated for the implementation of multiple bandgaps in an InGaAs/InGaAsP quantum-well laser structure. Multiple bandgap control is achieved by controlling the local defect concentrations without manipulating the critical rapid thermal annealing process using a multi-step plasma exposure or a spatial defect modulation. The interdiffusion process is found to obey Fick's law and enhanced by the near-surface point defects after a short plasma exposure time. For a prolonged exposure, the enhancement is reduced attributed to the possible formation of defect clusters. With single-step plasma exposure, the defect concentrations, thus intermixing degree, can be controlled using a variable window opening. This work demonstrates the practical approaches of multiple bandgap creation suitable for the photonic-integrated circuit application.

We present a transfer matrix analysis of a two-dimensional (2-D) filter to study its frequency response functions. The (M/spl times/N) array consists of N independent columns of microring resonators side-coupled to two channel bus waveguides, with equal spacing between columns and each column consisting of M coupled resonators. We show that such a general 2-D lattice network of lossless and symmetric resonators can approximate an ideal bandpass filter characterized by a flat-top box-like amplitude response without out-of-band sidelobes, and a linear phase response. The bandwidth is determined by the coupling factor between resonators. The 2-D periodic structure exhibits nonoverlapping photonic bandgaps arising from the complementary transmission properties of the row and column arrays. The row array behaves as a distributed feedback grating giving rise to narrow bandgaps corresponding to the flat reflection passbands of the filter with out-of-band sidelobes. The column array, on the other hand, acts as a high-order coupled-cavities filter with broad bandgaps that overlap with the sidelobe regions, thereby effectively suppressing the sidelobes. The phase response is linear except near the band edges, where enhanced group delay limits the usable bandwidth of the filter to about 80%. The minimum size of the array required is about 3/spl times/10, but is ultimately limited by waveguide loss.

The design of a compact mode filter (with a total length of 90 μm) using laterally tapered ridge waveguide is proposed. The mode filter comprises a down-taper waveguide and a single-mode waveguide for higher order modes discrimination, followed by a mode-size expander that restores the original fundamental mode size. The insertion loss for the fundamental mode could be as small as 0.02 dB. The operation is found to be insensitive to many of the device’s dimensions. The mode filter can be integrated with any ridge waveguide device, irrespective of the waveguides cross-section, material system and operating wavelength.

A material that has both negative permittivity and permeability is termed as left-handed material. The properties of Left Handed Material (LHM), such as negative refraction, have been simulated numerically by beam propagation method. The results are consistent with other works reported in the literature. It is shown that the Poynting vector and the phase velocity of the electromagnetic wave are indeed anti-parallel, confirming that the left-handed material does not violate the causality condition. It is conventional to simulate the phase restoring mechanism in a left-handed medium by showing (negative) refraction at an interface between an LHM and a conventional material. In this paper, we show for the first time, a simulation using BPM for the case of multiple-slit interference using Gaussian beam. The interference for two to three sources with different separations is used to show that the LHM can restore the phase and reverse the diffraction and interference effects.

We present a comparison of directional couplers and multi-mode interferometers based on the unique properties of high-index contrast ridge waveguides. The two devices are intimately related as the MMI is structurally derived from the DC. For the first time, the continuous evolution from the two-mode coupling characteristic of DC to the multi-mode mixing and interference characteristic of MMI is shown. We show that practical directional couplers with reasonable gap size can also be quite compact and have the same coupling length for both TE and TM polarizations. Consequently, the DC can be just as polarization insensitive as the MMI. These features, however, require careful design control involving a large set of design parameters. On top of that, we also show a novel design of polarization splitter based on both DC and MMI. By comparison, the MMI design is more robust and involves fewer design variables.

This paper presents a coherent approach to the design of compact vertical coupler (VC) mode-size converters with variable polarization dependence. As a polarization-independent (PI) coupler, the VC is shown to transfer light with more than 90% efficiency for both transverse-electric (TE) and transverse-magnetic (TM) modes over a transfer length of only 150 /spl mu/m. As a polarization-mode splitter (PMS), the VC is shown to preferentially couple TE or TM modes with a contrast ratio of up to 20 dB. This versatility makes the VC a compact and useful input-stage device that not only maximizes input/output coupling efficiency to small active devices but also provides a degree of polarization control before the actual device. The design principle is based on resonant coupling between the top tapered active waveguide and the underlying uniform large and passive waveguide. For the PI coupler, the taper is designed so that resonant transfer occurs near the critical width where the upper waveguide is nonbirefringent. For the PMS, the resonant transfer for TE and TM are designed to occur at widely separated points far from the critical width. Resonant coupling is sensitive to exact dimensions and the refractive index of the waveguides. The taper design is the key in ensuring that the VC performance is robust as well as compact.

We present a rigorous comparison of the unique characteristics of directional couplers and multimode interferometers based on the unique properties of high-index contrast ridge waveguides. The two devices are intimately related as the multimode interference (MMI) is derived from the directional couplers (DCs). We show for the first time the continuous evolution from the two-mode coupling characteristic of DC to the multimode mixing and interference characteristic of MMI, as the DC is structurally transformed into the MMI. We also show that DC can be designed to have the MMI features of compactness and polarization-insensitivity, two traits that reflect their shared lineage. The performance of MMI and DC are compared in terms of coupling length, polarization dependence, crosstalk, excess loss, and fabrication tolerances. We show that the DC, as long as it is designed to have nearly the same coupling length for transverse electric and transverse magnetic, can potentially have better performance than the MMI in terms of crosstalk and polarization sensitivity. Such a DC, however, requires careful control of many design parameters, while the MMI design is more robust and involves fewer design variables. Finally, the effect of higher-order modes and mode filtering are also considered.

We propose and demonstrate a two-ring coupled Mach-Zehnder interferometer (2RMZI) device that exhibits a sharp resonance with background suppression to give both high finesse and modulation depth. The combination of MZI and the two-ring structure leads to more complete destructive interference that effectively removes the unwanted background envelope effect found in the transmission spectrum of a simple two-ring-two-bus (2R2B) system. The projected finesse enhancement of 2RMZI relative to one-ring coupled MZI and 2R2B is discussed based on best-fit parameter values that match the fabricated devices.

For the first time, a nested-ring Mach-Zehnder interferometer (MZI) on silicon-on-insulator is realized using a complementary metal-oxide-semiconductor-based process. In this letter, we verify that the device operates in two modes: the inner-loop resonance dominant mode due to strong build-up inside the inner-ring, and the double-Fano resonances mode due to strong light interaction with the outer loop. The results show that the inner-loop resonance is highly sensitive to the MZI arm imbalance compared to the double-Fano resonance mode. Based on these considerations, we obtain a good fit between theory and experiment.

An InGaAsP/InP Electroabsorption Modulator (EAM) with single-sided large optical cavity (LOC) was studied and fabricated by low-pressure Metal Organic Chemical Vapor Deposition (MOCVD). Results show that the optical profile of EAM is greatly improved by the LOC structure, which is expected to increase the coupling efficiency and the optical saturation power.

We demonstrate theoretically that a simple two-coupled-ring structure yields very narrow resonances in the transmission spectra, provided the loss is very small. The linewidth is smallest when the path lengths of the two rings have a ratio of two. Relative to the single ring, the linewidth is reduced beyond the size scaling by the intensity buildup factor in the second ring. In the lossless case, the linewidth can be two orders of magnitude narrower. The enhancement can still be seen for experimentally demonstrated silicon-on-insulator microrings.

Photoluminescence (PL) spectroscopy is used to study the interface disorder and interface exciton transfer in single quantum wells of various well widths grown by MBE with different growth interruption times. Growth-interruption-induced microroughness on the interface terraces gives rise to peak splitting in the PL spectra with energy spacings that correspond to less than 1 ML width difference. We were able to use the well width dependence of the number of split peaks and the ratios of integrated PL intensity as an optical probe to determine the terrace areas and deduce the probability distribution of the interface roughness. Furthermore, a detailed study of the change in relative intensities of the various peaks in PL spectra taken at varying temperature reveals intra-well transfer of excitions among the localization regions and inter-well transfer. The intra-well transfer corresponds, in terms of energy, to either relaxation (by emission of an LO phonon) or thermal population (via phonon absorption).

Intrawell and interwell transfers of excitons are observed by a temperature-dependent continuous-wave photoluminescence study of growth-interrupted single quantum wells. The intrawell transfer among the interface localization areas suggests a thermodynamic equilibrium between energy relaxation via LO-phonon emission and thermal population via phonon absorption. Thermal population is dominant in wider wells while relaxation is clearly observable in a four-monolayer narrow well at low temperatures. Interwell transfer of excitons also occurs between two narrow wells. (C) 1998 Academic Press.

A novel 1×2 multimode interference photonics switch structure based on thermal controlling effect is proposed. A ridge waveguide of photosensitive polymer, benzocyclobutene (BCB 4024-40) on silica clad is used as a design structure. A temperature changes as a result of electrode heating are analysed by employing a two-dimensional finite difference thermal model considering both conduction and convection mechanisms. The switching characteristics due to changes in effective index are analysed by the two-dimensional finite difference beam propagation method with transparent boundary condition. The proposed structure works well with low crosstalk level of -28 dB and low switching power relatively to the structural upper cladding thickness.

The fabrication and characterization process of BenzoCyclobutene (BCB 4024-40) polymer waveguides are described. The polymer film thickness for various coating speed and refractive index are measured by the method of prism coupling. A cost effective chemical etching technique is used in the waveguide fabrication process to take advantage of the photosensitive nature of the polymer. The waveguide loss is measured using the conventional cut back method which results on an average loss of 3.5 dB/cm.

Nonlinear pulse propagation in a fibre link with periodic dispersion management (DM) is investigated, taking into consideration the effect of fibre loss. The mechanism that the quasi-stable soliton can exist in a dispersion-managed fibre is revealed. It is found that in the lossless case more energy is required for forming a quasi-stable soliton than the regular soliton in a uniform fibre system. However, when fibre loss is included, and for sufficiently large amplifier spacing, the required soliton energy in the dispersion-managed system is found to approach the same value as in a uniform fibre system, and thus the potential advantage of increased soliton energy in a DM fibre link is diminished with fibre loss. The shape of such a quasi-stable soliton is a nearly hyperbolic secant with loss but more Gaussian-like without loss.

A systematic design of compact polarization-mode splitters with mode-size converters using tapered resonant vertical couplers (VCs) has been demonstrated with contrast ratios as much as 95 : 1. The tapered transfer region is designed to include only the resonant width for the desired polarization. Such filters could be used as the input stage of polarization sensitive optical devices. The VC architecture also improves fiber coupling to the optical devices and serves as a means for vertical optical integration.

Growth interruption-induced microroughness is studied by photoluminescence (PL) of single quantum wells with different well widths and interruption times. Analysis of the peak splitting in the PL spectra shows that the adjacent peak splittings correspond to well width differences smaller than one monolayer. The number of split peaks increases with increasing well width, saturating when the well width exceeds 11 monolayers. This trend correlates well with the decrease in the lateral dimension of the exciton, which corresponds roughly to the minimum optically sampled area of the interface. For a given quantum well, a plot of the normalized integrated intensities of the split PL peaks versus the well width fluctuation is well described by a Gaussian distribution with an average fluctuation smaller than one monolayer. These results are consistent with the microroughness model.

The results for the Gordon-Haus jitter and the maximum transmission distance in a partial soliton communication system are presented. Using partial soliton technique, the amplifier spacing can be greatly extended, but the system performace is limited by the Gordon-Haus effect due to the larger amplifier gain.

For soliton-based WDM systems with lumped amplifiers, the variance of the timing jitter resulting from soliton collisions is derived. The BER expression of the systems is given by considering soliton collisions and the Gordon-Haus effect. The dependence of the BER on the channel spacing is discussed, and the optimal channel spacing is determined.

A simple approximation is developed for solving the “whispering gallery modes” of a microdisk laser structure using conformal transformation and the WKB approximation. Using this method the spontaneous emission coupling factor of microdisk lasers is estimated. The result predicts a β value of the order of 10-1.

Microdisk structures have been used to achieve low‐threshold lasing. For these microcavity lasers, the spontaneous emission coupling factor β is an important parameter since it determines the threshold current of the laser. Theoretical calculation of β based on the exact solution of the modes in a microdisk is complicated. A simple, approximate method for solving the waveguide modes and the density of states is developed here, using conformal transformation and the Wentzel–Kramers–Brillouin approximation and taking into account the effect of the disk thickness. We find that the β value for a microdisk laser is smaller than that of an ideal laser that has a cylindrical waveguide structure with a strong index guiding. A considerably high value of β can still be achieved, however, in a microdisk laser.

First-step nucleation growth has an important impact on the two-step growth of high-quality mid-infrared emissive InAs/InGaAs/InP quantum dots (QDs). It has been found that an optimized growth rate for first-step nucleation is critical for forming QDs with narrow size distribution, high dot density and high crystal quality. High growth temperature has an advantage in removing defects in the QDs formed, but the dot density will be reduced. Contrasting behavior in forming InAs QDs using metal-organic vapor phase epitaxy (MOVPE) by varying the input flux ratio of group-V versus group-III source (V/III ratio) in the first-step nucleation growth has been observed and investigated. High-density, 2.5 × 10(10) cm(-2), InAs QDs emitting at2.15 µm have been formed with narrow size distribution, ∼1 nm standard deviation, by reducing the V/III ratio to zero in first-step nucleation growth.

We report the first study of argon (Ar)-plasma-enhanced intermixing of InAs/InGaAs/InP self-assembled quantum dots (QDs) in an inductively coupled plasma reactive ion etch system. The Ar-plasma exposure creates point defects, which propagate into the QD structure and enhance the intermixing between the QDs and their barrier layers, hence tuning the energy bandgap of the QDs. By optimizing the plasma exposure time and the annealing temperature, we observe (i) a blueshift of 160 nm and an increase in the photoluminescence (PL) intensity of the QD samples immediately after Ar-plasma exposure for 90 s, and (ii) a further increase in the blueshift of 330 nm, accompanied by 2.5-times increase in the PL intensity and 37 nm narrowing in the PL linewidth after subsequent rapid thermal annealing at 720 °C. The ability to generate a large blueshift without degrading the material quality shows that Ar-plasma exposure is an efficient post-growth technique for tuning the energy bandgap of QD structures.

We propose a new device configuration that incorporates a nested ring with a Mach-Zehnder interferometer. The nested ring is analogous to a dual-bus coupled ring resonator, with the ends of the two buses connected to form a semi-closed loop. With proper design of the length of the U-shaped loop, as well as the coupling coefficient between the ring and the waveguide, the device is capable of generating a box-shaped spectral response. This is shown to be mainly due to the double-Fano resonances that arise from constructive interference between the nested ring and the outer loop. The device is simple in that it requires only one ring, and unique in that it harnesses a pair of Fano resonances to generate a reasonably box-like filter response. The analysis is based on the transfer matrix formalism, and compared and verified with the FDTD simulations.

Ring resonators are waveguide realizations of Fabry-Perot resonators which can be readily integrated in array geometries to implement many useful functions. Its nonlinear phase response can be readily incorporated into a Mach-Zehnder interferometer to produce specific intensity output function. We present two generalized array configurations of ring-coupled MZI and discuss their characteristics in terms of the amplitude and phase response of the ring arrays as well as the transmission output of the MZIs. The two types of array have distinct transfer functions and effective phase shifts, and can be tailored to phase-engineer a wide-range of MZI transmission functions.

We present a unique comparison of ridge-type directional couplers (DC) and multi-mode interferometers (MMI) in terms of their transformational relationship. The two devices are intimately related as the MMI is derived from the DC. We show for the first time the continuous evolution from the two-mode coupling characteristic of DC to the multi-mode mixing and interference characteristic of MMI, as the DC is structurally transformed into the MMI. We also show that DC can be designed to have the MMI features of compactness and polarization-insensitivity, two traits that reflect their shared lineage. However, the design of DC requires careful control of a large set of design parameters, while the MMI design is more robust and involves fewer design variables.

We present the first systematic design approach for compact polarization-independent mode-size transformers based on tapered resonant vertical couplers with transfer efficiencies greater than 90%. Resonant coupling occurs at a critical taper width having equal TE and TM effective index. Being polarization-independent broadens the usefulness of vertical coupler as a building block for minimizing insertion loss in photonic integrated circuits.

We present a coupling matrix formalism to investigate the effects of periodic and quasi-periodic orders on the photonic bandgap (PBG) structures of coupled-resonator optical waveguides (CROWs) based on microring resonators. For the periodic order case, size-tuned defects are introduced at periodic locations among the regular rings, which are size-untuned, to form a periodic ordered CROW system. The periodic coupled defects result in multiple localization states that lead to the formation of mini-defect bands and mini-PBGs within the PBG of a defect-free CROW. The position and number of such mini-defect bands depend on the size tuning of the defects. For the quasi-periodic order case, the arrangement of the defects and the regular rings in the ring cascade is an intermediate between periodic order and randomness, thus forming a quasi-periodic ordered CROW system. The effects of quasi-periodicity on the PBG structures are illustrated using the Fibonacci sequences, which result in a single high-Q localized state to appear that gradually transits to a mini-band within a wide photonic stop band as the number of lattice cells increases.

We propose a two-ring structure that can generate an ultra-narrow resonance which may be used, together with the Mach-Zehnder interferometer (MZI), to engineer bistability switching with low switching threshold and reasonably high extinction ratio (ER) and modulation depth (MD). The two-ring MZI (2RMZI) is also compared with the conventional one-ring MZI (1RMZI). A flexible optimization scheme has been developed and can be used to obtain maximum ER and MD. Complementary relationship between switching threshold, sensitivity to loss and optical bandwidth are discussed for the two types of devices.

This paper reports a sandwiched droplet resonator for low concentration protein detection using microfluidic chip (MFC). The droplet resonator integrated onto a single microfluidic chip consists of a sandwiched droplet and two optical fiber tapers that are directly placed into the droplet. The concentration measurement of protein is based on the shift of the resonant modes in the droplet resonator. The advantages of the resonator are the high quality factor (104 to 108), easy integration and no contamination, which promise the high accuracy (10-5 to 10-9 g/mL) measurement of protein concentration and label-free biosensing on the microfluidic chip.

Micro-cavity structure composed of silicon wire with 240 nm square cross section and two symmetrical sidewall waveguide Bragg gratings is fabricated and studied for the operation under telecommunication wavelengths. Optical filter of quasi-TE mode was realized based on this cavity. In such micro-cavity, optical quality factor (Q) was measured up to 380 with a 4.8 nm free spectral range (FSR) and 12 dB fringe contrast (FC). The measured group index of silicon waveguide with only 240 nm square cross section was between 3.80 and 5.43. It is the first time group delay of silicon wire waveguide with such small core dimension is studied. Larger group delay can be expected after optimizing the design parameters and the fabrication process.

There is a recent trend to reduce waveguide based silicon photonic devices to the sub-micron regime for increased chip density and better cost efficiency. However, designing polarization independent (PI) ring resonator using submicron waveguide is a challenge as it exhibits strong polarization dependency. We demonstrate theoretically the feasibility of realizing both single-mode (SM) and PI operation in ring resonator based on sub-micron silicon-on-insulator (SOI) rib waveguides. A resonance spectra misalignment that represents only 11% of the full-width half-maximum (FWHM) linewidth of 1.64 nm is achieved, with a free spectra range of 13 nm.

We propose that a boxlike filter response can be obtained by utilizing complementary photonic bandgap properties of the column and row configurations in two-dimensional microresonator arrays. The filters are fabricated using deep-UV lithography in silicon-on-insulator technology. The observed sidelobes reduction is approximately 10 dB, and the usable bandwidth can be as high as 500-750 GHz.

We propose a finesse enhancement scheme by a simple two-ring system, in which the resonance finesse is dependent on the relative intensity buildup of the second ring with respect to the first. In lossless case, it is possible to obtain finesse two orders of magnitude higher than that of the single ring system. The two-ring system is fabricated in silicon-on-insulator using deep UV (DUV) lithography and shown to exhibit the finesse of 100 to 300. The associated finesse enhancement of 20 is in a good agreement with the theory.

We propose a scheme based on two-ring resonator system that can realize flat delay and transmission response with delay-bandwidth product (DBP) higher that those achieved in previously proposed schemes. The spectrum flatness and DBP are two key parameters that characterize the maximum number of bits that can be buffered without distortion for certain signal operating bandwidth. Simple time domain simulation shows that our scheme can achieve the same buffering time with 2 to 4 times smaller number of modules, which indicates DBP of 2 to 4 times larger than those of side-coupled ring structure and coupled resonator optical.

In this proceeding, we present for the first time, a nested-ring Mach-Zehnder interferometer (NRMZI) on SOI (Silicon-on- insulator), realized using a CMOS based process. We show that the device operates in two propagating resonance modes: (1) The inner-loop resonant mode due to strong build-up inside the inner-ring and (2) the double Fano-resonance mode due to strong light interaction with the outer loop. The experimental data shows that the inner-loop resonance is highly sensitive to the MZI arm imbalance as compared to the double-Fano resonance mode. With such considerations, a good fit is acquired between theory and experiment.

We show experimentally the existence of defect modes in mutually coupled microring resonator array fabricated in silicon-on-insulator technology. The movements of donor-like and acceptor-like modes are demonstrated for various defect lengths and in a good agreement with earlier theoretical prediction.