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Self-assembly has the advantage of fabricating structures of complex functionalities, from molecular levels to as big as macroscopic levels. Natural self-assembly involves self-aggregation of one or more materials (organic and/or inorganic) into desired structures while templated self-assembly involves interstitial space filling of diverse nature entities into self-assembled ordered/disordered templates (both from molecular to macro levels). These artificial and engineered new-generation materials offer many advantages over their individual counterparts. This paper reviews and explores the advantages of such naturally self-assembled hybrid molecular level systems and template-assisted macro-/microstructures targeting simple and low-cost device-oriented fabrication techniques, structural flexibility, and a wide range of photonic applications.

Erbium-doped Na3Al2P3O12 (NAP) glasses with compositions 92NAP–(8−x)Al2O3–(x)Er2O3 (where x = 2–8) were prepared and characterized for absorption, visible and NIR emission and decay time properties. Judd–Ofelt analysis has been carried out to predict radiative properties of luminescent levels of Er3+ ions. Comparatively larger photoluminescence lifetimes (7.86 ms) and larger quantum efficiencies (74%) for the laser transition, 4I13/2 → 4I15/2 (at 1.54 μm) are observed. The moisture insensitivity, large Er3+ ion doping capability and relatively high-gain and broad emission at 1.5 μm are the most notable features of these glasses to realize efficient short-length optical amplifiers.

Modified photoluminescence is demonstrated from the dye saturated porous silicon based single and coupled microcavities. When photonic cavity mode is weakly coupled to the emission states of the dye, photoluminescence line narrowing and intensity enhancement have been observed. Our experimental work and transfer matrix simulations and cavity modelling convincingly explain the tunability and optical field confinement within the microcavity. We also show that the photoluminescence enhancement is due to one-dimensional microcavity effect. These optically active hybrid materials from inexpensive fabrication may become an important consideration for many photonic applications.

Trivalent dysprosium (Dy3+)-doped sodium–aluminum–phosphate (NAP) glasses were prepared and characterized by their optical absorption, excitation, emission spectra, and decay time measurements. Judd–Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime and stimulated emission cross section of the 4F9/2 → 6H13/2 and 4F9/2 → 6H15/2 transitions. The luminescence intensity ratio of 4F9/2 → 6H13/2 to 4F9/2 → 6H15/2 transitions of Dy3+ in NAP glasses gives the feasibility of extracting white light. The lifetime and quantum efficiency of 4F9/2 level is found to be higher than other reported glasses. With increase in Dy3+ ion concentration, the decay from 4F9/2 level is found to be faster with decrease in lifetime due to cross relaxation between Dy3+ ions.

Synthesis, crystal structure and optical properties of two-dimensional layered inorganic–organic hybrid NH 3 (CH 2 ) 12 NH 3 PbI 4 are presented. Intercalation strategy has also been used to fabricate single crystal and thin films of the same. As thin film, they are well oriented and stacked along the [l 0 0] direction with strong room-temperature excitonic absorption and emission characteristics. Exciton features were correlated with the relative inorganic network crumpling and conformation of alkylammonium chains. The structural features are compared with those of similar hybrid, (H(CH 2 ) 12 NH 3 ) 2 PbI 4 .

Quasi-one-dimensional lead (II) iodide compound, C14H18N2Pb2I6, with unique crystal structure was synthesized and solved for the crystal structure. These novel inorganic-organic hybrids have high thermal stability of upto 300 °C and show excitonic and charge-transfer features in their optical properties. An attempt has been made to understand the structural and optical mechanisms between inorganic one-dimensional polymeric PbI nano ribbons and the guest organic moiety for future applications in nanoscaled electronic devices.

Zinc oxide (ZnO) is recognised as a potential II–VI photonic semiconductor and wavelength-scale ordered patterning of such material helps favourably in tailoring the photonic properties. Here we present two novel approaches for fabricating ZnO photonic structures, namely, via a synthetic route and via electrochemical deposition. We demonstrate fabrication of well-ordered mesa and microphotonic structures from self-assembly of template-assisted electrochemical deposition. We have explored various aspects of the fabrication techniques for achieving an optimized performance. Several optical, electrical and structural techniques are used to highlight the potential utility of these ZnO photonic structures. Our results suggest that these structures show promise in many novel photonic applications.

Block matching and optical flow algorithms are the two major motion estimation techniques that are widely employed today. The main aim of this paper is to compare the above two algorithms in terms of processing time, Peak Signal to Noise Ratio (PSNR), Structural Similarity (SSIM) and Mean Opinion Score (MOS). An exhaustive search block matching algorithm which has the maximum efficiency compared to any other block matching algorithm as well as the Brox's optical flow estimation algorithm are implemented. The algorithms are optimized by selecting appropriate parameter values that gives the best result. Then the algorithms are compared based on their motion estimated image for the same input image sequence and finally the results obtained are analyzed.

We report a passively mode-locked, diode-pumped waveguide laser operating in the 1.5µm spectral region using a quantum dot SESAM as the saturable absorber element. A repetition rate of up to 6.8GHz and an average power as high as 30mW is obtained during mode-locked operation. Minimum pulse duration of 2.5ps is produced at a wavelength of 1556nm. The repetition rate of the source was tuned by more than 1 MHz by changing the pump power, demonstrating a possible route towards integrated pulse repetition rate stabilisation.

Recently, we have demonstrated the first passively mode-locked Yb:glass channel waveguide laser operating with a repetition rate of 4.9 GHz. In this work we report the pulse repetition frequency as high as 15.2 GHz from a diode-pumped Yb:glass waveguide laser which produces a pulse duration of 811 fs with an output power of 27 mW at around 1047 nm.

Solid-state lasers operating in the eye-safe region near 2 micron are of considerable interest owing to various application areas such as remote sensing, spectroscopy and LID AR. Thulium-based gain media have several attractive features including a broad emission bandwidth, a broad absorption band near 800 nm that can be diode pumped and the possibility of obtaining a quantum efficiency of up to 200% due to the process of cross-relaxation. Guided-wave devices can offer additional advantages of compactness and integration, as well as lower thresholds and high slope efficiencies if low propagation losses can be obtained. Such devices, when combined with integrated saturable absorber elements, can also be passively modelocked to generate femtosecond pulses with multi-GHz repetition rates [1].

Summary form only given. RbTiOPO4 (RTP) belongs to the KTiOPO4 (KTP) family of crystals and has similarly useful nonlinear optical properties. In addition, RTP allows higher doping of rare-earth elements, such as Yb3+, when compared to KTP, a 2 times larger damage threshold than KTP, a very large electro-optic coefficient, a low dielectric constant and high chemical stability, which makes these materials very interesting for active photonics applications. In particular, Yb3+-doped RTP exhibits a broad fluorescence spectrum that has been exploited to demonstrate ultrafast operation, with pulses as short as 155 fs being generated [1]. Recently, planar waveguiding has been demonstrated in an (Yb3+, Nb5+):RTP film grown by liquid phase epitaxy [2], opening the possibility of planar integrated devices based on this highly functional material.Channel waveguides based on this thin-film technology would be of considerable interest for realising, for example, compact ultrafast lasers with GHz repetition rates [3] with applications in optical frequency metrology, optical sampling and biological imaging, or self-frequency-doubled lasers for visible laser sources. In this work we discuss the reactive ion etching (RIE) of RTP and the process optimisation to fabricate single-mode channel waveguides for lasing application around 1 micron. A 200-nm layer of chromium (Cr) was deposited on a number of RTP substrates grown by the top-seeded solution growth method (TSSG), after which it was photolithographically patterned to give a Cr mask with waveguide features of widths 1 μm to 10 μm. The masked substrates were etched in an OPT Plasmalab 80 plus RIE system (Oxford Instruments) with an RF frequency of 13.56 MHz. SF6 and Ar were used to etch the substrates in order to study the interplay between chemical and physical etching processes, respectively. The gas flow rates, gas pressures and RF power were systematically varied to get a good balance between etch rate and RMS surface roughness. The dependence of the etch rate and surface roughness on each parameter is shown in figure 1. Based on these graphs the optimum conditions were chosen to be: RF power of 250 W, gas pressure of 40 mTorr and gas flow rate of 10 sccm for both SF6 and Ar (giving a total gas flow rate of 20 sccm). A 6-μm-thick (Yb,Nb): RTP thin-film was grown on an undoped RTP substrate by liquid phase epitaxy and then etched for 135 minutes with the optimised conditions. It was then end polished to give a 6-mm-long waveguide. An SEM image of the end face of a 9.8-μm-wide channel is shown in the inset of figure 1. The sidewall angle was measured to be 63° and the etch depth was 1.4 μm. Waveguiding experiments were carried out by end-fire coupling a 981nm fiber-coupled single-mode laser diode into the channels. The output was found to be single-mode, with 1/e2 mode diameters measured to be 16.4 μm and 8 μm in the x and y directions respectively and is in good agreement with the simulated values of 15.2 μm and 6.8 μm.

We present the fabrication of single-mode rib waveguides in (Yb,Nb):RbTiOPO4 ((Yb,Nb):RTP) by reactive ion etching (RIE) with a combination of SF6 and Ar gases. The influence of the gas pressure, RF power and gas ratio on the etch rate and surface quality was studied to optimize the etching of RTP. Optimized parameters were used to fabricate rib waveguides in a (Yb,Nb):RTP film, grown by liquid phase epitaxy, with an etch rate of 10 nm/min. Channel waveguide propagation was demonstrated for the first time in an RIE etched (Yb,Nb):RTP rib structure.

A parent glass within the CaO-MgO-Al2O3-SiO2 system and resulting glass ceramics (GCs) have been appraised for solid oxide fuel cells (SOFCs) sealing applications. The sintering behavior was investigated by differential thermal analysis and hot stage microscopy. The glass composition exhibited single-stage shrinkage behavior with high sintering ability, and a suitable viscosity of 10(7.1) dPa s at the SOFCs operating temperature 900 degrees C. X ray diffraction in conjunction with the Rietveld-RIR technique were employed to quantify the crystalline and amorphous phases in the GCs sintered at 900 degrees C for 1 h and 850 degrees C for 300 h. The coefficients of thermal expansion (CTE) measured were 9.7 x 10(-6) K-1 (200-500 degrees C) and similar to 10.1 x 10(-6) K-1 (200-700 degrees C) for glass and GCs, respectively, in good agreement with those typical for SOFC components. Weibull analysis was applied on the three-point bend data of GCs in order to obtain the mechanical strength distribution, characteristic strength and Weibull modulus. Well matching CTE, flexural strength values, good sintering behavior and adhesion to the other components in air atmosphere allow proposing this glass composition as promising candidate for further experimentation as sealant for SOFCs. (C) 2012 Elsevier B.V. All rights reserved.

In this paper, we present a diode-pumped, solid-state waveguide laser operating near 1550 nm that is passively mode-locked using a quantum-dot SESAM. A fundamental repetition rate of up to 6.8 GHz with an output power of 30 mW was achieved during mode-locked operation. Pulse durations as short as 2.5 ps were measured at a repetition rate of 4.8 GHz. Fine control of the of the repetition rate was demonstrated by varying the pump power and a tuning range of up to 1 MHz was demonstrated.

Here we fabricated and studied highly-layered Inorganic-Organic Multiple Quantum Well structures and later placed them into metallic low quality factor microcavities. Room-temperature strong exciton-photon coupling is achieved in such single and coupled microcavities. Upon angle tuning, the broad photonic mode of the microcavities is clearly split into two modes at the exciton resonant absorption of hybrid perovskite. The large Rabi splitting upto -213 meV is obtained in good agreement with the theoretical models.

Here we fabricated highly-layered perovskite Inorganic-Organic Hybrid Quantum Well (IO-HQW) structure and conveniently placed them into dielectric/metallic heterostructures. Upon angle tuning, the broad photonic mode of the microcavity is clearly split into two modes at the strong exciton resonance OI-HQW absorption. The large Rabi splitting (∼130meV) obtained is in good agreement with the theoretical models and paves way to new optoelectronic device applications.

Room-temperature strong-coupling has been observed with large Rabi splitting of upto 202meV when layered inorganic-organic multiple quantum wells (IO-MQWs), are embedded in low-Q microcavities. Incorporating exciton-switching hybrid further allows active control of the strong-coupling parameters.

We report here the novel optical properties of naturally self-assembled hybrid organic-inorganic multiple quantum wells (OI-MQWs). These hybrids consist of a stack of alternative organic and inorganic nanolayers of widths ~ 6 and 10Aring respectively. They exhibit strong room temperature narrow exciton absorption and photoluminescence features due to quantum and dielectric confinements. The exciton peak position in these OI-MQWs could be tuned in the visible region by structural rearrangement. We have also demonstrated the capability of these heterostructures as strong candidate for exciton-photon strong coupling when sandwiched in metallic cavities.

A new class of Erbium doped glasses with compositions xNa2O - (60-x)PbCl2 - 40P2O5 (x=0, 10, 20 and 30) were fabricated and characterized for optical properties. Absorption spectra were analyzed for important Judd-Ofelt parameters from the integrated intensities of various Er3+ glass absorption bands. Photoluminescence (PL) and its decay behavior studies were carried out for the transition 4I13/2 -> 4I15/2. A systematic correlation between the Judd-Ofelt parameter {omega}2 and the covalent nature of the glass matrix was observed, due to increased role of bridging oxygens in the glass network. The PL broadness and life times of 4I13/2_> 4I15/2 transition were typically in the range of 40-60nm and 2.13-2.5ms respectively. These glasses broadly showed high transparency, high refractive index, shorter life times and, most importantly, these glasses were found to be capable of being doped with larger concentrations of Er3+ (up to 4 wt%). Increase of Er3+ concentration resulted in the increase in PL line-widths with no significant effect of concentration quenching, indicating that these glasses are suitable for optical fibre/waveguide amplifiers., submitted to Optical materials

Wide varieties of naturally self-assembled two-dimensional inorganic-organic (IO) hybrid semiconductors, (4-ClC6H4NH3)2PbI4, (C6H9C2H4NH3)2PbI4, (CnH2n+1NH3)2PbI4 (where n = 12, 16, 18), (CnH2n-1NH3)2PbI4 (where n = 3, 4, 5), (C6H5C2H4NH3)2PbI4, NH3(CH2)12NH3PbI4, and (C4H3SC2H4NH3)2PbI4, were fabricated by intercalating structurally diverse organic guest moieties into lead iodide perovskite structure. The crystal packing of all these fabricated IO-hybrids comprises of well-ordered organic and inorganic layers, stacked-up alternately along c-axis. Almost all these hybrids are thermally stable upto 200 °C and show strong room-temperature exciton absorption and photoluminescence features. These strongly confined optical excitons are highly influenced by structural deformation of PbI matrix due to the conformation of organic moiety. A systematic correlation of optical exciton behavior of IO-hybrids with the organic/inorganic layer thicknesses, intercalating organic moieties, and various structural disorders were discussed. This systematic study clearly suggests that the PbI layer crumpling is directly responsible for the tunability of optical exciton energy.

Photoluminescence and transmission is systematically explored in thin films of long–alkyl-chain-based inorganic-organic (IO) hybrids (CnH2n+1NH3)2PbI4 (n = 12, 16, 18) (CnPI) and NH3C12H22NH3PbI4 (DDPI). Such IO-hybrids, which form natural multiple quantum well structures stacked up along c-axis, possess strong room-temperature exciton transitions. These hybrids exhibit reversible phase transition of two different crystal phase transitions at easily accessible device temperatures. Flipping the structural phase is clearly reflected in switching of the excitons with corresponding photoluminescence and transmission changes showing clear thermal hysteresis. The phase-dependent switching of excitons is predominantly due to reversible crumpling of the inorganic PbI sheet networks. Systematic temperature dependent studies establish a correlation between the structure and optical exciton features. Such thermo-optic exciton switching suggests possible new photonic devices.

Optoelectronic-compatible heterostructures are fabricated from layered inorganic-organic multiple quantum wells (IO-MQW) of Cyclohexenyl ethyl ammonium lead iodide, (C(6)H(9)C(2)H(4)NH(3))(2)PbI(4) (CHPI). These hybrids possess strongly-resonant optical features, are thermally stable and compatible with hybrid photonics assembly. Room-temperature strong-coupling is observed when these hybrids are straightforwardly embedded in metal-air (M-A) and metal-metal (M-M) low-Q microcavities, due to the large oscillator strength of these IO-MQWs. The strength of the Rabi splitting is 130 meV for M-A and 160 meV for M-M cavities. These values are significantly higher than for J-aggregates in all-metal microcavities of similar length. These experimental results are in good agreement with transfer matrix simulations based on resonant excitons. Incorporating exciton-switching hybrids allows active control of the strong-coupling parameters by temperature, suggesting new device applications.

Hybrid organic-inorganic perovskite semiconductors provide significant opportunities as multifunctional materials for many electronic and optoelectronic applications. These include organic-inorganic light emitting diodes, organicinorganic field-effect transistors, and nonlinear optical switches based on strong exciton-photon coupling in microcavity photonic architectures. 1‐4 The basic structure of these lead II halide-based two-dimensional 2D pervoskites takes the general form R-NH32PbI4 where R is organic consisting of layers of corner-sharing lead iodide octahedra with bilayers of organic cations stacked between the inorganic layers. 5‐7 These form ‘natural’ multiple quantum well structures, where wells of the 2D inorganic semiconducting layer are clad by barriers of the wider bandgap organic layers. Typical layer thicknesses of well and barrier are 6 and 10 A, respectively. The low dimensionality of carriers confined within the inorganic layers by quantum confinement combined with the large dielectric mismatch giving dielectric confinement between the layers, enables formation of stable excitons with large binding energy even at room temperatures. 8,9 These hybrids are thermally stable up

The structural and optical spectra of two related lead iodide (PbI) based self-assembled hybrid organic‐inorganic semiconductors are compared. During the synthesis, depending on the bridging of organic moiety intercalated between the PbI two-dimensional planes, different crystal structures are produced. These entirely different networks show different structural and optical features, including excitonic bandgaps. In particular, the modified organic environment of the excitons is sensitive to the local disorder both in single crystal and thin film forms. Such information is vital for incorporating these semiconductors into photonic device architectures. (Some figures in this article are in colour only in the electronic version)

Thin films of self-organized quantum wells of inorganic-organic hybrid perovskites of (C6H9C2H4NH3)2PbI4 are formed from a simple intercalation strategy to yield well-ordered uniform films over centimeter-size scales. These films compare favorably with traditional solution-chemistry-synthesized thin films. The hybrid films show strong room-temperature exciton-related absorption and photoluminescence, which shift with fabrication protocol. We demonstrate the potential of this method for electronic and photonic device applications.