Biomedical subjects

Shayan Mookherjea

Publications and source records attributed to Shayan Mookherjea.

10 recordsLinked to original sources

PubMed2007

Effect of disorder on slow light velocity in optical slow-wave structures.

Slow-wave optical structures such as coupled photonic crystal cavities, coupled microresonators, and similar coupled-resonator optical waveguides are being proposed for slowing light because of the nature of their dispersion relationship. Since the group velocity becomes small, slow light and enhanced light-matter interaction may be observed at the edges of the waveguiding band. We derive a model of the effects of disorder on slow light in such structures, obtaining a relationship between the root-mean-square variation in the coupling coefficients and how slow the light is at the band edge.

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PubMed2005

Mode cycling in microring optical resonators.

Electromagnetic resonators are important not only as realizable models of fundamental concepts in classical and quantum physics, based on the existence and properties of eigenmodes, but also in the practical design of lasers, amplifiers, sensors, filters, and delay lines. Coupled-eigenmode systems may be realized via the multiple eigenmodes of a single resonator or by the coupling of a mode across multiple resonators. Mode cycling is demonstrated as a distinct concept of sequential population transfer in coupled multiple-eigenvalue resonators. Based on this principle, a coupled polymeric microring resonator interferometer is fabricated and characterized; the device achieves greater than 30 dB extinction and (loaded) Q approximately 5.5 x 10(3).

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PubMed2005

Dispersion characteristics of coupled-resonator optical waveguides.

A tight-binding optical waveguide formed by proximity coupling of nearest-neighbor resonators, e.g., a coupled-resonator optical waveguide (CROW), has distinct wave and pulse propagation characteristics compared with a conventional waveguide, and several applications in photonic devices have been proposed recently. But analysis of the dispersion, and in particular the group-velocity dispersion, in such a waveguide requires particular attention: the waveguide displays two distinct regimes of operation, depending on the position of the wave packet in the dispersion relationship.

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PubMed2005

Analysis of longitudinal-field reflection in dielectric gratings.

Because of a common approximation used in the derivation of the wave equation, conventional analyses of Bragg reflection from dielectric gratings do not account for the distinctive behavior of the longitudinal field component of the electric field. We address this issue, which has particular significance in subwavelength scale periodic dielectric structures. We discuss new reflection phenomena within the theoretical framework of coupled-wave analysis, supplemented with numerical calculations.

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PubMed2005

Nonparaxial dark solitons in optical Kerr media.

We show that the nonlinear equation that describes nonparaxial Kerr propagation, together with the already reported bright-soliton solutions, admits of (1 + 1)D dark-soliton solutions. Unlike their paraxial counterparts, dark solitons can be excited only if their asymptotic normalized intensity u2infinity is below 3/7; their width becomes constant when u2infinity approaches this value.

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PubMed2004

Nonparaxial spatial solitons and propagation-invariant pattern solutions in optical Kerr media.

We investigate nonlinear propagation in the presence of the optical Kerr effect by relying on a rigorous generalization of the standard parabolic equation that includes nonparaxial and vectorial terms. We show that, in the (1 + 1)-D case, both soliton and propagation-invariant pattern solutions exist (while the standard hyperbolic-secant function is not a solution).

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PubMed2003

Transverse Bragg resonance laser amplifier.

We propose and analyze a new type of optical amplifier that is formed by addition of gain in the periodic cladding of a transverse Bragg resonance waveguide [Opt. Lett. 27, 936 (2002)]. Using the coupled-wave formalism, we calculate the mode profiles, the exponential gain constant, and, for comparison, the gain enhancement compared with those of conventional semiconductor optical amplifiers. In contrast with coupled-mode theory, in one-dimensional structures (e.g., the distributed-feedback laser) the exponential gain constant in the longitudinal direction is involved in both longitudinal and transverse confinement, and its solution has to be achieved self-consistently, together with the quantized guiding channel width.

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PubMed2002

Kerr-stabilized super-resonant modes in coupled-resonator optical waveguides.

We investigate the effects of the optical Kerr nonlinearity in a coupled-resonator optical waveguide (CROW). Under certain conditions, there exists a stationary spatial distribution of the field whose envelope does not change with time-a super-resonant mode. The analysis does not indicate the existence of traveling hyperbolic-secant solitons of the Schrödinger type.

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PubMed2002

Pulse propagation in a coupled resonator optical waveguide to all orders of dispersion.

In studying the propagation of optical pulses beyond the linear dispersion approximation, the conventional term-by-term Taylor series expansion of the waveguide dispersion relationship fails when applied to the recently introduced family of coupled resonator optical waveguides (CROWs). We have found the surprising result that retaining the complete form of the dispersion relationship in the tight-binding approximation does in fact lead to a closed form analytical solution, clearly highlighting the role of the various phenomenological factors. Such an analysis is usually not possible in the majority of waveguiding structures and is especially useful in the design of photonic crystal CROWs and deep superstructure Bragg gratings.

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PubMed2002

Second-harmonic generation with pulses in a coupled-resonator optical waveguide.

We describe the generation and propagation of pulses in a coupled-resonator optical waveguide driven by a nonlinear polarization using a method closely related to the coupled-mode theory. The specific example we consider is that of second-harmonic generation. This formalism explicitly accounts for temporal dependencies in the waveguide field distributions and in their representations in terms of slowly modulated Bloch wave functions, in contrast with the equations obtained previously for cw second-harmonic generation.

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