In this article, we investigated the possibility of achieving all- angle, polarization insensitive and broad band self- collimation simultaneously in a same structure, which is one of the most recently introduced urgent requirements in the field of optical integration. In order to fulfill these three attractive properties in 2D square array photonic crystals, different strategies are used and a comprehensive analysis using Plane Wave Expansion and Finite Difference Time Domain methods are done. Here, the main attempt was to save the structure’s simple geometry and not to complicate the basic structure. So in order to get all- angle self- collimation, we had to use relatively high index material (n=6) for hole type structure which shows less dependency on polarization. The optimized structure has a frequency range of 2.6%, supporting all-angle self- collimation for both polarizations achieved to the expense of small deviation of 30 in collimation direction from ideal case, although it will not cause any significant problem for small sized devices in the field of optical integration.  پرونده مقاله

In this paper, we used photonic crystal resonant cavity structure for designing a 2-channel optical wavelength demultiplexer. It has been shown that by using photonic crystal resonant cavity, wavelength separation is possible. In order to select 2 channels with different central wavelengths we employed 2 resonant cavities with different structural parameters. The platform used for designing the proposed demultiplexer is a hexagonal lattice of dielectric rods immersed in air. The demultiplexer has 2 channels with central wavelengths equal to l1=1549.4 nm and l2=1551.2 nm. The transmission efficiency of the demultiplexer is more than 92%. The quality factors for first and second channels are 1936 and 3021 respectively. پرونده مقاله

In this paper, a photonic crystal structure for comparing two bits has been
proposed. This structure includes four resonant rings and some nonlinear rods. The
nonlinear rods used inside the resonant rings were made of a doped glass whose linear
and nonlinear refractive indices are 1.4 and 10-14 m2/W, respectively. Using Kerr effect,
optical waves are guided toward the correct output ports. In this study, plane wave
expansion and finite difference time domain methods were used for calculation of
photonic bandgap and simulation of optical wave propagation, respectively. The size of
the proposed structure is 1585 μm2 which is more compact than the previous works.
Furthermore, the obtained maximum delay time is about 2 ps that is proper to highspeed
processing. The normalized output power margins for logic 0 and 1 are calculated
as 25% and 71%, respectively. According to the obtained results, this structure can be
used for optical integrated circuits. پرونده مقاله

Abstract: In this paper, we aim to design and propose a novel structure for all-optical
half subtractor based on the photonic crystal. The structure includes two optical switches,
one power splitter, and one power combiner. The optical switches are made of the
resonant rings which use the nonlinear rods for dropping operation. The footprint of the
designed structure is about 602 μm2 that is more compact than one in most works.
Furthermore, despite some works, the input signals are the same in the phase angle and
the optical power. Also, each input signal is applied to one port while this issue has not
been considered in some works. Plane wave expansion and finite difference time domain
methods are used to calculate the band diagram and simulation of the optical wave
propagation throughout the structure, respectively. The maximum obtained rise time of
all states of the proposed device is just about 1.4 ps. Besides, the presented structure is
capable of working at the third communication window so it can be matched with optical
fiber transmission systems. پرونده مقاله

Abstract Using a photonic crystal array, an all-optical
half-subtractor has been designed that consists of four
resonant rings and some waveguides which connect two
input ports to output ports. The silicon rods with a period
of 0.631 μm are arranged in the form of a square.
Concerning the four working states of the device,
different radii of nonlinear rods inside the resonators
have been chosen. This issue makes the different
switching thresholds for the rings and results in the
correct dropping operation for optical waves. Unlike the
previous works, each bit is defined to one port, and the
input ports have equal power. The maximum rise time
and the contrast ratio of the presented circuit are 3.5 ps
and 8.45 dB, respectively. The fast response and small
size are the main advantages of the presented subtractor.
The obtained results demonstrates that the designed
device has an acceptable performance which is proper for
optical applications. پرونده مقاله

Abstract
New design in photonic crystal structures has provided a great opportunity to employ optical decoders with high contrast ratio and low response time. Based on the last published articles, photonic crystal-based decoders result in a contrast ratio higher than 20 dB and a response time of 200 fs which is proper to use in optical circuits. Changing the path of a signal may occur with the help of a resonator in the form of a cavity or ring. Dropping a signal at a wavelength makes a possible to direct it toward the desired path. We present an introduction to the decoding operation and its advantages in different applications, followed by an explanation of the excellent features of photonic crystals including forbidden bandgap and the optical Kerr effect. Furthermore, we discuss the key role of the resonance phenomenon in photonic crystal structures. Then, we investigate the valuable designs in approaching the decoding. It has been tried to present an algorithm to design photonic crystal-based decoders which is so needed for research.  پرونده مقاله