Pawel Szczepanski

InP-Based Photonic Multiwavelength Transmitter With DBR Laser Array

We demonstrate an InP-based photonic multiwavelength transmitter realized by integrating an array of distributed Bragg reflector lasers with modulators in Mach-Zehnder configuration. An arrayed waveguide grating is used to multiplex the generated signals into a common optical output. The device is designed according to a generic integration concept, using standardized building blocks, and is fabricated in a multiproject wafer run. The device delivers up to 4 dBm of optical power into the fiber with a modulation data rate of 12.5 Gbps per transmission channel. The obtained performance makes it very promising for application in the next generation optical access networks as a key source in the central office part of the telecommunication systems.

Nonlinear operation of a planar circular-grating DBR laser

An approximate method for the analysis of the nonlinear operation of a planar circular-grating distributed Bragg reflector laser is presented. The analysis is based upon vector-wave self-consistent coupled-mode equations modified to take into account gain saturation effects. With the help of an energy theorem and threshold field approximation, an approximate formula relating small-signal gain to the output power and laser parameters is derived. The laser characteristics obtained reveal behavior of the optimal coupling strength of the Bragg reflector, which provides maximal power efficiency as a function of the laser parameters. It is also shown that the gain saturation effect provides mode selectivity in the laser structure.

Approximate Analysis of Nonlinear Operation of Square Lattice Photonic Crystal Laser

In this paper, an approximate method for the analysis of 2-D square lattice photonic crystal laser operation above the threshold is presented. Our approach is based on coupled wave equations, including gain saturation effect, and energy theorem. An expression for the small signal gain coefficient as a function of the output power, losses, coupling strength depending on the shape of the primitive cell of photonic crystal as well as index contrast, and active medium dimension is derived. Laser characteristics obtained reveal optimal coupling strength, for given structure parameters, for which maximal power efficiency of the laser structure is obtained.

Non-orthogonality of the longitudinal eigenmodes of a distributed feedback laser

Abstract We discuss the orthogonality of the longitudinal modes of the distributed feedback (DFB) laser. The excess noise factors, or so-called excess spontaneous emission factors, for the several longitudinal DFB modes are calculated. They are found to be near unity for the strong coupling region and substantially larger than unity for the weak coupling region.

Modeling of amplification and light generation in one-dimensional photonic crystal using a multiwavelength transfer matrix approach

We present an analysis of amplification and lasing in one-dimensional isotropic nonlinear photonic crystal (1D PC), which is based on a generalized (multiwavelength) transfer matrix method. This approach was used for modeling a Raman signal amplification in 1D PC and in an homogenous structure, showing advantages of a stratified medium. Moreover, the threshold operation of a 1D PC Raman laser is studied, assuming both strong as well as depleted pump. The normalized threshold gain characteristics for various end reflections and photonic crystal laser length were calculated.

Influence of end reflectivity on the excess-noise factor in distributed feedback lasers

The influence of end reflectivity on the excess noise factor in distributed feedback lasers is analyzed. It is shown that the end reflectivity affects the excess-noise factor markedly in the weak and moderate coupling region. In particular, in this coupling region the noise level in the laser structure strongly depends on the end reflectivity phase. Moreover, in the weak and moderate coupling region, the excess-noise factor decreases with an increasing end reflectivity amplitude; in the strong coupling region the opposite behavior is observed. >

Effect of mode nonorthogonality in distributed-feedback lasers

An analysis of the quantum noise in distributed-feedback lasers based on the Fokker-Planck equation has been developed to take into account the nonorthogonal nature of the laser modes. We have obtained numerical results of the steady-state solution of the single-mode operation that reveal the difference between the standard approach orthogonal laser modes and the realistic model (mode nonorthogonality included) for a distributed-feedback laser with nonvanishing end reflectivity and the complex coupling coefficient.

Spatial and frequency domain effects of defects in 1D photonic crystal

The aim of this paper is to present the analysis of influence of defects in 1D photonic crystal (PC) on the density of states and simultaneously spontaneous emission, in both spatial and frequency domains. In our investigations we use an analytic model of 1D PC with defects. Our analysis reveals how presence of a defect causes a defect mode to appear. We show that a defect in 1D PC has local character, being negligible in regions of PC situated far from the defected elementary cell. We also analyze the effect of multiple defects, which lead to photonic band gap splitting.

Influence of mode nonorthogonality on the correlation function of the amplitude and of the intensity fluctuation of a distributed-feedback laser

The influence of mode nonorthogonality on the correlation function of the intensity fluctuation and of the amplitude that determines laser linewidth as well as the coherence of light is investigated. The semiclassical approach based on a time-dependent solution of the Fokker–Planck equation is used. Numerical results obtained for a distributed-feedback laser with nonvanishing end reflectivity and a complex coupling coefficient reveal the difference between the standard approach (for orthogonal modes) and the more realistic model (mode nonorthogonality included).

Tunable slow light in graphene-based hyperbolic metamaterial waveguide operating in SCLU telecom bands

The tunability of slow light in graphene-based hyperbolic metamaterial waveguide operating in SCLU telecom bands is investigated. For the first time it has been shown that proper design of a GHMM structure forming waveguide layer and the geometry of the waveguide itself allows stopped light to be obtained in an almost freely selected range of wavelengths within SCLU bands. In particular, the possibility of controlling light propagation in GHMM waveguides by external biasing has been presented. The change of external electric field enables the stop light of the selected wavelength as well as the control of a number of modes, which can be stopped, cut off or supported. Proposed GHMM waveguides could offer great opportunities in the field of integrated photonics that are compatible with CMOS technology, especially since such structures can be utilized as photonic memory cells, tunable optical buffers, delays, optical modulators etc.