[show abstract][hide abstract] ABSTRACT: We present a new method for the calculation of the dispersion diagrams of general nonuniform waveguides. The method is based on the spatial Fourier transform (SFT) of the electromagnetic field distribution along the guiding direction. We demonstrate the validity and robustness of the SFT technique using several test cases. As an application, we apply the method to analyze the dispersion of biperiodic photonic crystal waveguides and show that the guiding bandwidths of these waveguides can be significantly enhanced by a proper choice of the two distinctive spatial periods of the biperiodic waveguides.
IEEE Journal of Quantum Electronics 09/2004; · 1.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: For the first time, we experimentally demonstrate ultra-low-loss guiding in bi-periodic photonic crystal waveguides over a large bandwidth of more than 60nm. In such bi-periodic waveguides, we achieve a propagation loss very similar to that of a dielectric ridge waveguide, which indicates that the dominant loss mechanism in these bi-periodic waveguides is due to fabrication imperfections.
Applied Physics B 08/2004; 79(4):409-414. · 1.78 Impact Factor
[show abstract][hide abstract] ABSTRACT: This study proposes a switching device that may also be used as a variable optical attenuator that combines two ideas: light guiding along the thermally induced waveguide and the adiabatic mode transition in the slowly widening optical taper. Measurement results for a 1×2 switching device are also presented.
Lasers and Electro-Optics Society, 2003. LEOS 2003. The 16th Annual Meeting of the IEEE; 11/2003
[show abstract][hide abstract] ABSTRACT: We developed a matrix theory that applies to any cylindrically symmetric fiber surrounded with Bragg cladding, which includes both the Bragg fibers and the recently proposed dielectric coaxial fibers. In this formalism, an arbitrary number of inner dielectric layers are treated exactly and the outside cladding structure is approximated in the asymptotic limit. An estimate of the radiation loss of such fibers is given. We compare the asymptotic results with those obtained from the finite difference time domain calculations and find excellent agreement between the two approaches
Journal of Lightwave Technology 04/2002; 20(3):428-440. · 2.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: Summary form only given. Photonic crystals have inspired a lot of
interest recently due to their potential for controlling the propagation
of light. Photonic crystals with line defects can be used for guiding
light. A conventional method for making a two-dimensional (2D)
dielectric-core photonic crystal (or PBG) waveguide is to remove one row
of air columns. This usually results in a multimode waveguide. We
present a more systematic way of making single-mode dielectric-core 2D
PBG waveguides. It was recently shown that the main guiding mechanisms
in dielectric-core PBG waveguides are total internal reflection and
distributed Bragg reflection (DBR). The confinement of the guided mode
in the center slab of the waveguide suggests that the properties of such
modes can be modified by modifying the guiding structure in the vicinity
of the center slab
Lasers and Electro-Optics, 2001. CLEO '01. Technical Digest. Summaries of papers presented at the Conference on; 02/2001
[show abstract][hide abstract] ABSTRACT: An asymptotic analysis is developed to calculate the modal dispersion, field distribution, and propagation loss of Bragg fibers. The design considerations of Bragg fibers are also discussed.
Optical Fiber Communication Conference and Exhibit, 2001. OFC 2001; 02/2001
[show abstract][hide abstract] ABSTRACT: Using a formalism similar to the quantum scattering theory, we analyze the problem of coupling between optical waveguides and high Q resonators. We give the optical transmission and reflection coefficients as functions of the waveguide-resonator coupling, cavity loss (gain), and cavity resonant frequency. Based on these results, the recently proposed concept of "critical coupling" is discussed. Using a matrix formalism based on the scattering analysis, we find the dispersion relation of indirectly coupled resonator optical waveguides. The coupling between waveguides and multiple cavities is investigated and the reflection and transmission coefficients are derived.
Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics 12/2000; 62(5 Pt B):7389-404.
[show abstract][hide abstract] ABSTRACT: We show that by placing a slab of semiconductor material between two photonic bandgap (PBG) mirrors, waveguide modes at frequencies out of the PBG can be obtained. These modes are similar to the modes of a conventional dielectric slab waveguide. Using these modes, we can obtain very good coupling between a PBG waveguide and a dielectric slab waveguide with similar slab properties. We discuss the properties of these slab modes and outline the guideline for the optimization of the PBG waveguides based on these properties
Journal of Lightwave Technology 12/2000; 18(11):1554-1564. · 2.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: The authors present a systematic method for designing
dielectric-core photonic crystal optical waveguides that support only
one mode in the photonic bandgap (PBG). It is shown that by changing the
sizes of the air columns (without perturbing the positions of the
centres of the air column) in the two rows that are adjacent to the
middle slab, the higher order mode(s) can be pushed out of the photonic
bandgap, resulting in singlemode wave propagation in the bandgap
[show abstract][hide abstract] ABSTRACT: Summary form only given. We recently proposed a new type of waveguide, the coupled-resonator optical waveguide (CROW), where an array of high Q resonators are coupled together. Under the tight-binding approximation, we found that the dispersion relation of a CROW can described by a coupling coefficient K and that its group velocity is greatly reduced. However, the concept of CROW is not necessarily limited by the tight-binding approximation. Here we propose a novel CROW structure by coupling a series of resonators with a waveguide.
[show abstract][hide abstract] ABSTRACT: We propose a new type of optical waveguide that consists of a sequence of coupled high-Q resonators. Unlike other types of optical waveguide, waveguiding in the coupled-resonator optical waveguide (CROW) is achieved through weak coupling between otherwise localized high-Q optical cavities. Employing a formalism similar to the tight-binding method in solid-state physics, we obtain the relations for the dispersion and the group velocity of the photonic band of the CROW's and find that they are solely characterized by coupling factor k(1) . We also demonstrate the possibility of highly efficient nonlinear optical frequency conversion and perfect transmission through bends in CROW's.
[show abstract][hide abstract] ABSTRACT: A laser cavity formed from a single defect in a two-dimensional photonic crystal is demonstrated. The optical microcavity consists of a half wavelength-thick waveguide for vertical confinement and a two-dimensional photonic crystal mirror for lateral localization. A defect in the photonic crystal is introduced to trap photons inside a volume of 2.5 cubic half-wavelengths, approximately 0.03 cubic micrometers. The laser is fabricated in the indium gallium arsenic phosphide material system, and optical gain is provided by strained quantum wells designed for a peak emission wavelength of 1.55 micrometers at room temperature. Pulsed lasing action has been observed at a wavelength of 1.5 micrometers from optically pumped devices with a substrate temperature of 143 kelvin.
[show abstract][hide abstract] ABSTRACT: A two-dimensional photonic crystal defined hexagonal disk laser
which relies on Bragg reflection rather than the total internal
reflection as in traditional microdisk lasers is described. The devices
are fabricated using a selective etch to form free standing membranes
suspended in air. Room temperature lasing at 1650 nm for a 150 nm thick,
~15 μm wide cavity fabricated in InP/InGaAsP is demonstrated with
pulsed optical pumping
[show abstract][hide abstract] ABSTRACT: An active, photonic band gap-based microcavity emitter in the near infrared is demonstrated. We present direct measurement of the spontaneous emission power and spectrum from a microcavity formed using a two-dimensional photonic band gap structure in a half wavelength thick slab waveguide. The appearance of cavity resonance peaks in the spectrum correspond to the photonic band gap energy. For detuned band gaps, no resonances are observed. For devices with correctly tuned band gaps, a two-time enhancement of the extraction efficiency was demonstrated compared to detuned band gaps and unpatterned material.
[show abstract][hide abstract] ABSTRACT: We developed a general numerical method to calculate the spontaneous emission lifetime in an arbitrary microcavity, using a finite-difference time-domain algorithm. For structures with rotational symmetry we also developed a more efficient but less general algorithm. To simulate an open radiation problem, we use absorbing boundaries to truncate the computational domain. The accuracy of this method is limited only by numerical error and finite reflection at the absorbing boundaries. We compare our result with cases that can be solved analytically and find excellent agreement. Finally, we apply the method to calculate the spontaneous emission lifetime in a slab waveguide and in a dielectric microdisk, respectively.
Journal of the Optical Society of America B 02/1999; · 2.21 Impact Factor
[show abstract][hide abstract] ABSTRACT: We form a microcavity laser using two-dimensional photonic crystals embedded in a half wavelength thick waveguide. Modes localized to a single defect in the photonic crystal can be theoretically shown to have mode volumes as small 2(λ/2n)<sup>3</sup> and near unity spontaneous emission coupling factors. The flexibility in design of the photonic crystal enables one to tailor the device for vertical emission or for coupling into an in-plane waveguide. These type of devices may be useful for high density, low threshold optical sources in compact optical systems. The added versatility in being able to etch the laser cavity may also help develop low threshold laser sources in material systems in which high index contrast epitaxial mirrors do not exist. The defect laser cavities were formed in the InGaAsP material system in order to reduce the non-radiative surface recombination rate. The active region consists of four quantum wells (QW) designed for 1.55 μm peak emission at room temperature
Lasers and Electro-Optics Society 1999 12th Annual Meeting. LEOS '99. IEEE; 02/1999
[show abstract][hide abstract] ABSTRACT: We form a new type of optical microcavity using 2D photonic
crystals embedded in a half wavelength thick waveguide. Modes localized
to a single defect in the photonic crystal can be theoretically shown to
have small mode volumes. The flexibility in design of the photonic
crystal enables one to tailor the device for vertical emission or for
coupling into an in-plane waveguide. The added versatility in being able
to etch the laser cavity may also help develop low threshold laser
sources in material systems in which high index contrast epitaxial
mirrors do not exist
Nanostructures and Quantum Dots/WDM Components/VCSELs and Microcavaties/RF Photonics for CATV and HFC Systems, 1999 Digest of the LEOS Summer Topical Meetings; 02/1999
[show abstract][hide abstract] ABSTRACT: Structures with periodically modulated refractive index are
frequently discussed under the classification of photonic crystals.
Recently, much attention has been paid to these types of structures for
a large variety of applications such as the inhibition or enhancement of
spontaneous emission, ultra-low threshold lasers, compact optical
circuits, light-emitting diodes with increased efficiency and novel
optical waveguides. Using structures that exhibit a photonic bandgap
(PBG), it has been shown that high-Q, small modal volume microcavities
can be created. Advances in semiconductor fabrication technology have
made it possible to make semiconductor PBG microcavities for optical
LEOS '99. IEEE Lasers and Electro-Optics Society 1999 12th Annual Meeting; 02/1999