International Journal of

---

Our recent advances in solid-state optoelectronic materials and devices will be reviewed. In the area of glass optics, fabrication of novel microstructured and multi-core fibers and their use in realizing single mode lasers will be summarized. In organic and plastic optics, photorefractive polymers for 3D display applications and nonlinear optical polymers for high speed modulators in RF photonic and remote antenna applications will be discussed. Our progress in medical optics including adaptive eyewear and imaging will also be described.

---

In this paper we present an in-depth review on the trends and the directions taken by the researchers worldwide in Optical Code Division Multiple Access (OCDMA) systems. We highlight those trends and features that are believed to be essential to the successful introduction of various OCDMA techniques in communication systems and data networks in near future. In particular we begin by giving a comprehensive review on the constructions of optical orthogonal codes (OOC). In our system study we first focus and discuss on various OCDMA techniques such as 1-D, 2-D and spectrally-encoded ultrashort light pulse CDMA, and discuss their pros and cons. A comprehensive discussion takes place on all important aspects of each OCDMA technique. In particular, we elaborate on enabling technologies that are needed prior to full scale consideration of OCDMA in communication systems. We extend our discussion to various data networks, including fiber-based and wireless to indicate the directions and the applications that OCDMA systems are considered for. It is believed that OCDMA once fully developed and matured will be an inseparable part of advanced optical communication systems and networks due to its various desirable features and functionalities, in not so distant future.

---

In this paper, we have reported the fabrication of two-dimensional photonic crystals, using a direct writing method in azo polymers. Periodic structures have been fabricated using the interference patterns of two coherent laser beams. The frequency response of the initial one-dimensional structure shows an attenuation of 19.3dB at 1554nm. The twodimensional structure shows 8.3dB and 11.3dB of attenuation at 1554nm in two perpendicular main axes of the structure. The diffraction pattern shows the characteristic rectangular pattern.

---

In this paper the Phase-Matching bandwidth, effective nonlinear coefficient and the walk-off angle within the effective bandwidth of the LiGa(SexS1-x)2 biaxial nonlinear crystals are calculated using the Genetic algorithm (GA). This calculation is held for all tree principle XY, YZ and XZ planes individually. The results are shown the accuracy of the applied algorithm is quite qualified.

---

Micro-channels are made over the Ag+/Na+ ion-exchanged soda-lime glass surface by interaction of an intense Ar+ laser beam and the silver ions inside the glass matrix. The Ar+ laser beam reduces the Ag+ ions inside the matrix. The Ag+ atoms aggregate into silver nano-clusters around the interaction area, inside the glass matrix. Aggregation of the silver atoms and the thermal effects of the interaction, changes the geometrical profile of the glass surface. This phenomenon has been used to produce micro-sized channels over the glass surface. During the interaction the glass has moved under the focused laser beam in two dimensions by resolution of 300 nm via a computer controlled xyz sub-micro-positioner to produce the channel walls. Using this technique, micro-channels of 0.3 μm deep and arbitrary width have been made. The height of the produced wall has been determined by interferometry techniques.

---

In this paper, we present a comparative numerical analysis to determine the refractive index of photonic crystal fibers (PCFs) by using FDFD method and used the results to evaluate the confinement losses of PCFs by considering the effects of air-hole rings in the cladding. It is shown that by increasing the wavelength, the imaginary part of refraction index rises, resulting in increase of confinement losses nearly by order of 10. In lower wavelengths over the range of 0.2 to 1 μm, these losses were shown to be negligible. The obtained results show that as the number of air-hole ring in the cladding increases, the confinement losses over wavelengths would reduce. To show the effect of air-hole rings on confinement losses in PCFs, the FDFD method yielded accurate results that agree well with results of FEM method and source–model technique reported by others.

---

Electronic absorption, florescence excitation and AFM studies of selected homogeneous solutions and thin films of mesotetrakis (parahydroxyphenyl) porphyrin (THPP) (1), mesotetrakis (2, 3- dihydroxyphenyl) porphyrin 2, 3-OHPP) (2), mesotetrakis (3, 4-dihydroxyphenyl) porphyrin (3, 4-OHPP) (3) as well as Zn(II) derivative of 2, 3-OHPP (4) under UV lamp and green laser irradiation (532 nm) are acquired and analyzed.Our results indicate that in irradiation experiments, the products of the resulting porphyrins strongly depend on the careful choice of the light source. UV lamp irradiation produced J-type aggregated diacid porphyrins from free base porphyrins by simple photochemical technique. The stabilization of the aggregates structure may be achieved through hydrogen bonding between the protonated core and the peripheral hydroxyl groups, mediated by the chloride anions. The results of laser irradiation experiments shown the formation of J-aggregated porphyrin upon green laser (532 nm) irradiation.Green laser irradiation has been caused the hydrogen bonding interactions between neighboring porphyrin molecules through hydroxyl moieties to produce J-aggregated supramolecular porphyrins. The AFM topographic images and Dynamic Light Scattering (DLS) of THPP(1) under green laser irradiation have been indicated nano-structured porphyrin wires about 5 nm high approximately.

---

In this work, using perturbation technique we have developed an approximate analytic model for evaluating the band structure of a 2-D octagonal photonic quasicrystal (PQC). Although numerical techniques are being used for evaluating such band structures, developing a numerical model to the best of our knowledge this work is the first instance of reporting helps to understand the physical properties of the structure more easily. Use of perturbation technique can be beneficial in approximating the photonic band structures, in PQCs made with low-dielectric contrast materials, with high accuracy. To the best of our knowledge this work is the first instance of reporting the development of such an analytic model for octagonal PQCs. In addition, we have studied the effect of variations in the dielectric contrast on the photonic band structure.

---

We generalized the squeeze and displacement operators of the one-dimensional harmonic oscillator to the three-dimensional case and based on these operators we construct the corresponding coherent and squeezed states. We have also calculated the Wigner function for the three-dimensional harmonic oscillator and from the analysis of time evolution of this function, the quantum Liouville equation is also presented. Further properties of the quantum states including Mandel’s 􀡽 and quadrature squeezing parameters are discussed as well.

---

We have studied light-induced birefringence (LIB) and surface relief grating (SRG) formation in the series of methylacrylate polymers. The effect of material structure such as length of photochromic side chain, glass transition temperature and molecular structure of azo units on LIB and SRG are studied. The optical formation of self-induced SRG on films of these materials is also presented.

---

In this paper, by including Raman scattering in the coupled-mode equations, the scalar modulation instability in photonic crystal fibers is investigated. The evolution of the pump, Stokes and anti-Stokes waves along the fiber as well as the conversion efficiency for two cases, with and without Raman effect, are studied. The effect of anti-Stokes seed and the pump depletion on the evolution of Stokes wave is also considered. Moreover, the parametric gain when it is affected by Raman gain is dealt with. The results show that it is important to take into account Raman scattering, especially for wide-bandwidth parametric amplifiers which results in an asymmetric spectrum and more amplification of the Stokes wave.

---

We proposed and analyzed implementation of the single-qutrit quantum gates based on stimulated Raman adiabatic passage (STIRAP) between magnetic sublevels in atoms coupled by pulsed laser fields. This technique requires only the control of the relative phase of the driving fields but do not involve any dynamical or geometrical phases, which make it independent of the other interaction details: detuning and pulse shapes, areas and durations. The suggested techniques are immune to spontaneous emission since the qubit and qutrit manipulation proceeds through non-absorbing dark states. In this paper, taking proper timing of the Rabi frequencies allows us to transfer the population of the system to a desired superposition of the ground states with the highest fidelity. We also obtained and implemented single-qutrit unitary gates, for transferring of the population of the system with different initial and final states.

---

Europium doped transparent lead fluorophosphate glass ceramics successfully were prepared with heat treatment of precourse glasses at temperature above glass transition (Tg). X-ray diffraction (XRD) experiment evidenced the formation of PbF2 nanocrystals in glassy matrix. The emission spectra investigation indicate that considerable amount of Eu3+ ions were trapped in crystalline phase, and therefore the efficient frequency-conversion was observed in glass ceramics samples. The investigated glass ceramics systems are potentially applicable as up and down frequency-conversion photonics materials.

---

In this paper, we present calculations for different parameters of quantum dot infrared photodetectors. We considered a structure which includes quantum dots with large conduction-band-offset materials (GaN/AlGaN). Single band effective mass approximation has been applied in order to calculate the electronic structure. Throughout the modeling, we tried to consider the limiting factors which decline high temperature performance of these devices. Temperature dependent behavior of the responsivity and dark current were presented and discussed for different applied electric fields. Specific detectivity used as figure of merit, and its peak was calculated in different temperatures. This paper indicates the state of the art in the use of the novel III-N materials in infrared detectors, with their special properties such as spontaneous and piezoelectric polarizations. It was found that, III- nitride Quantum dots have a good potential to depress the thermal effects in the dark current which yields the specific detectivity up to~ 2107 CmHz 1/ 2/W at room temperature.

---

Photosynthesis is a process under which, the radiative energy is converted into the chemical one. Compared to the man-made devices, the photosynthesis apparatus is much more efficient. This high efficiency comes from its elaborate structure, very fast transition rates and a complex electron and proton transfer chain among the subunits of the apparatus. Its main subunits (Photosystem I (PSI), bf complex and photosystem II (PSII)) are connected through different mobile carriers. Among these, the cytochrome bf complex, connecting PSI and PSII, plays an essential role in the photosynthetic process. During recent years, the function and structure of this complex has been studied using different experimental methods. On the other hand, to explain its dynamic, the complex has been mathematically modeled. In this paper, based on a kinetic model, proposed earlier by one of the authors, an improved model has been introduced and the new experimental data has been analyzed. The model is a comprehensive one that considers the different components of the complex and also its relation with mobile charge carriers (plastocyanin and plastoquinones). Via comparison with experimental data, the rate of redox reactions has been determined by using the mathematical methods of parameter identification. Despite the large number of parameters, nonlinearity and coupling of governing equations, and indeterminacy of the initial values, the results of modeling conforms well to the experimental data. This may help to a better understanding of the bf complex structure and behavior, in particular, and of the photosynthesis apparatus as a whole.

---

In this paper, we study the coherent transport of single photon in a coupled resonator waveguide (CRW) where two threelevel Λ-type atomic ensembles are embedded in two separate cavities. We show that it is possible to control the photon transmission and reflection coefficients by using classical control fields. In particular, we find that the total photon transmission and reflection are achievable. In addition, the two atomic ensembles can act as controllable mirrors of a secondary cavity (super-cavity) which represents localized photon states and makes it possible to store and retrieve single photon in the region sandwiched between the two atomic ensembles.

---

Fabricating an electrically switchable cylindrical Fresnel lens based on holographic polymer-dispersed liquid crystals (H-PDLC) using a Michelson interferometer is reported. Simplicity of the method and possibility of fabricating different focal length lenses in a single set up are among the advantages of the method. It is demonstrated that the Fresnel structured zone plate acts as a cylindrical lens and focuses light in one dimension. Its electro-optical switching properties are also studied and it is found that at an applied electric field of E=6 Vrms/μm across the sample, focusing property of the sample eliminates with a response of about 1 ms in a reversible manner.

---

The Photoexcited carrier lifetime (τ) and peak to valley transmission difference (ΔTp-v) in direct and indirect band gap crystals has been investigated by the use of single beam open and closed aperture z-scan technique using frequency doubled Nd:YAG laser. The peak to valley transmission difference (ΔTp-v) is found to be of the order of 10-2 in case of direct band gap crystals and of the order of 10-3 in case of indirect band gap crystals. The carrier life time (τ) is found to be in nanoseconds range in case of direct band gap crystals and picoseconds range in case of indirect band gap crystals. Lower value of (τ) and (ΔTp-v) in case of indirect band gap crystals can be attributed to the reduction in the value of carrier density (N) and small value of nonlinear phase shift ( Δϕ ),respectively.

---

We report the observations of dual wavelength amplified spontaneous emission from the solutions of a conjugated polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) in Tetrahydrofuran and 1, 2 Dichlorobenzene. We have prepared MEH-PPV using a modified procedure and purified several times in each step, the material offers low molecular weight, low polydispersity index and high thermal stability, which are some of the most important requirements for the fabrication of photo luminescent devices. The variation in the features of amplified spontaneous emission with increasing polymer concentration is presented. For intermediate polymer concentrations, narrow emissions were observed for the 0-0 and 0-1 vibronic peaks which were not reported in solutions to the best of our knowledge. The ASE characteristics sensitively depend on concentration as well as pump power. The gain studies show that MEH-PPV is a potential laser media. By varying the concentration of the solution and pump power we can use either of the two different wavelength bands for lasing applications.

---

We perform a theoretical investigation on the Goos-Häenchen shift (the lateral shift) in one-dimensional photonic crystals (1DPCs) containing left-handed (LH) metamaterials. The effect was studied by use of a Gaussian beam. We show that the giant lateral displacement is due to the localization of the electromagnetic wave which can be both positive and negative depending on the incidence angle of Gaussian beam that can be excited the forward and backward surface states, respectively. Dependence of beam width on the incidence angle of beam and thickness of air layer for both backward and forward surface states are studied in this paper. We also find that the weak lossy in LH layers of 1DPCs may affect these shifts. These giant negative and positive lateral shifts are smaller than that of the lossless structure.