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Silicon photonics, particularly its compatibility with existing silicon microelectronic technology, has been increasingly studied in recent years. China sees the potential impact on the sustainability of its economic development and is increasing the investment in this new research area. But, the lack of research and manufacture accumulation in silicon microelectronic technology will weigh down the pace of silicon photonics research in China in the years to come. [ABSTRACT FROM AUTHOR]

Different configurations of a T-junction power splitter are investigated using complex-envelope alternating-direction-implicit finite-difference time-domain method. The use of reflectors on both sides of the waveguide significantly improved the performance of the T-junction waveguide after optimising the gradient of the reflectors. Cavity resonators have been added to the structure, and the transmission power on both sides of the T-junction structure is maximised. Furthermore, a photonic crystal (PhC)-based T-junction has been investigated. The results show that the use of the PhC has a major impact on the performance of T-junction. [ABSTRACT FROM AUTHOR]

A multiresolution time-domain (MRTD) technique is proposed and applied to the analysis of arbitrarily shaped photonic devices. The suggested method implements the multiresolution analysis in the context of method-of-moments for the solution of Maxwell's equations. To improve the capabilities of the proposed method, the uniaxial perfectly matched layers absorber for the MRTD is rigorously incorporated and better performance is reported over the conventional finite-difference time-domain. Various numerical examples demonstrate the stability and numerical precision of the suggested MRTD method for both linear and nonlinear applications. Moreover, the application of the suggested MRTD scheme for the design of a photonic crystal-based optical wavelength filter and for the analysis of a frequency converter is presented. [ABSTRACT FROM AUTHOR]

The paper reports an investigation of the dispersion properties of a planar photonic crystal (PhC) through short pulse propagation, demonstrating the ability of the PhC to compress sub-picosecond pulses by factors of up to 40%. The first direct measurement of pulse compression using the large group velocity dispersion available from planar PhC coupled cavity wave guides is reported. A main problem that remains to be solved is the high loss in the wave guide. This is attributed to two main factors, the design and fabrication of the PhC wave guide.

A flower-type photonic quantum ring (PQR) laser for enhanced output power of about five times that expected from circular PQR lasers of the same size has been designed and fabricated. The multi-petal flower design, combining concave and convex whispering cave modes, increases the overall quantum wire length of the emitting PQR within the same device area. [ABSTRACT FROM AUTHOR]

Silicon photonics has expanded considerably in the last decade and a number of companies have also released products onto the market place. Some of the recent results from the field are reviewed before the main areas requiring further research before they can be achieved are discussed. An overview is given of the major Si photonics research presently being pursued in the UK. Finally, a number of potential new applications are also presented. [ABSTRACT FROM AUTHOR]

Polarisation-insensitive wavelength conversion by four-wave mixing (FWM) has been demonstrated in a 20 m short nonlinear photonics crystal fibre. Theoretical analysis confirms that the combination of a 45° pump launch and a minimum pump-probe detuning is required to reduce the polarisation sensitivity of FWM to ∼1 dB. [ABSTRACT FROM AUTHOR]

A simple structure of octagonal photonic crystal fibre (O-PCF) for ultra-flattened chromatic dispersion and extremely low confinement losses is presented. It has been demonstrated that a four-ring O-PCF can operate a single mode in a 390 nm wavelength range with ultra-flattened chromatic dispersion and a very low confinement loss less than 0.001 dB/km. [ABSTRACT FROM AUTHOR]

A reconfigurable photonic microwave bandpass filter with negative coefficients based on polarisation modulation is proposed. Experimental results show that a filter response can be reshaped by changing the polarisation state and power of optical sources corresponding to sign and amplitude of filter coefficients, respectively. [ABSTRACT FROM AUTHOR]

An all-optical correlator based on a single logic XOR gate is proposed. The device consists of an active Mach-Zehnder interferometer with an external feedback loop. The address/word detection functionality is demonstrated at 10 Gbit/s with 2-bit optical labels. [ABSTRACT FROM AUTHOR]

Flat super-continuum generation spanning over the whole telecommunication band using a passively modelocked fibre laser source at 1550 nm together with a dispersion-flattened nonlinear photonic crystal fibre is demonstrated. Since the pulses propagate in the normal dispersion regime of the fibre only, linear frequency chirp is induced by self-phase modulation which leads to a flat super-continuum. By launching the compressed 170 fs modelocked pulses with an average power of 10 mW into the fibre, super-continuum over 185 nm with less than 5 dB fluctuation is obtained from the all-fibre configuration. [ABSTRACT FROM AUTHOR]

A comb-like profiled fibre (CPF), an alternate concatenation of a dispersive fibre and nonlinear fibre, is capable of emulating an arbitrary dispersion profile over distance for high quality optical pulse compression. It is demonstrated experimentally that CPF is efficient for the reshaping of an optical beat signal into a high quality 160 GHz 730 fs soliton pulse train with remarkably low noise, while stimulated Brillouin scattering was well suppressed. [ABSTRACT FROM AUTHOR]

The BER performance of a 2D λ-t OCDMA system is compared experimentally with optimum sampling (global clock) and non-optimum sampling (recovered clock from an OCDMA receiver). The power and BER penalties of the receiver are quantified, and the impact of interferers on its performance is determined. [ABSTRACT FROM AUTHOR]

A photonic crystal fibre (P(F) with polarisation mode dispersion (PMD) of 0.03 ps/rkm was obtained by unidirectional twist. The work was also successful in reducing the PMD of the PCF to 10% of its initial value by periodic bidirectional twisting without loss increasing and structural deformation. [ABSTRACT FROM AUTHOR]

A tunable and stability-enhanced all-optical wavelength converter of 9.95328 Gbit/s 2.5 Ps RZ-OOK signal is successfully demonstrated with power penalty < 0.5 dB over the maximal pump-probe wave-length spacing, ∼23 nm. It is implemented based on the cross- polarisation modulation (XPolM) effect in a 64 m-long nonlinear photonics crystal fibre (PCF). The utilisation of such a short length of highly nonlinear PCF operating in the normal dispersion region not only reduces the wavelength converter's sensitivity to environmental disturbances and walk-off effect, but also eliminates modulation instability effects in the XPolM process. [ABSTRACT FROM AUTHOR]

A new photonic method has been used to generate the sawtooth waveform in a serrodyne optical frequency translator. Experimental results demonstrate an overall sideband suppression of greater than 24.5 dB. The technique has wideband capability for realising higher optical frequency shifts and sideband suppression than electronic approaches. [ABSTRACT FROM AUTHOR]

A new coherence-free photonic notch filter structure is presented. It is based on a Sagnac fibre loop interferometer containing an optical intensity modulator. A notch filter response is obtained by modulating the clockwise and counter-clockwise propagating optical waves inside the Sagnac loop at different times. Results demonstrate a robust notch filter operation with a narrow-linewidth laser source, and elimination of phase-induced intensity noise limitations. [ABSTRACT FROM AUTHOR]

A long-period waveguide grating in a polymer channel waveguide, which consisted of a benzocyclobutene core and an epoxy cladding, has been fabricated. By changing the stress in the waveguide through etching of the cladding width, a polarisation-insensitive resonance wavelength thermo-tunable from 1520 to 1610 nm with a temperature range of only 8°C was achieved. [ABSTRACT FROM AUTHOR]

Open rings are utilised to realise TE-polarised 2D (E-field parallel to rings) photonic bandgap (PBG) structures. Open rings are placed in a regular lattice along the axis normal (longitudinal axis) to the plane of rings to construct quasi-rods, which are then set in a regular 2D lattice to obtain the PBG structure. Density of the elements along the longitudinal axis can be used to adjust the width of the bandgap. Typical guiding and resonance behaviours that are common features of 1D and 2D PBG defects can be easily realised in the context of this novel PBG. Simulations show confinement of the field within the defect regions. [ABSTRACT FROM AUTHOR]

The negative thermo-optic coefficient of water has been used to fabricate an athermal Bragg grating device. Glucose was used to modify the refractive index of water, allowing this response to be tuned to the desired operating temperature range. Over a 10°C temperature range the Bragg response was found to vary by 3.7 pm, an improvement of nearly two orders of magnitude over the unetched Bragg grating. The low cost of fabrication compared to traditional athermal Bragg devices makes them ideal for incorporation within integrated photonic networks. [ABSTRACT FROM AUTHOR]

A simple confocal microscope design based on a single hollow-core fibre approach has been developed and experimentally analysed. Key optical components are the use of a hollow-core photonic bandgap fibre and a holed-mirror beam-splitter, both of which provide significant reduction of Fresnel back-reflections at the fibre tips and total background level resulting in increased resolving confocal laser power. [ABSTRACT FROM AUTHOR]

A new microwave photonic notch filter structure is presented. It is based on a remodulation concept, in which the second modulation is frequency selective. Results are presented for the new structure, which show a sharp narrow notch with a notch 6 dB bandwidth of 63 kHz and a notch depth of 44 dB, a wide passband, and coherence-free operation with no phase induced intensity noise. [ABSTRACT FROM AUTHOR]

A novel photonic analogue-to-digital conversion scheme using an electroabsorption modulator and supercontinuum light is proposed. A 2-bit photonic analogue-to-digital conversion is experimentally demonstrated based on the proposed scheme combined with an arrayed waveguide grating. [ABSTRACT FROM AUTHOR]

A low-biased Mach-Zehnder modulator, optical amplification, and a high-power photodetector are employed to achieve all-photonic link gain as high as 44 dB over a transmission length of 40 km. The link has a 3 dB bandwidth of 6.25 GHz and a 20 dB noise figure. [ABSTRACT FROM AUTHOR]

Focused ion beam etching has been used to introduce one-dimensional photonic lattices, of periods 9.11, 9.24, 9.44 µm, between the cleavedfacets of three 4.44 THz Fabry-Perot quantum cascade lasers. Singlemode lasing has been achieved at precisely defined wavelengths of 67.59, 68.48, 70.00 µm, respectively. [ABSTRACT FROM AUTHOR]

A technique for photonic digital-to-analogue converter is presented based on weighting and summing high-speed, modelocked laser pulses. The fundamental concept builds on the basic electronic digital-to-analogue converter implementation. A one gigasample-per-second converter with two bits of resolution demonstrates the principle of operation. [ABSTRACT FROM AUTHOR]

The splice loss at 1.55 μm between a 34 μm core diameter singlemode photonic bandgap fibre and a G-652 fibre has been dramatically reduced from 2.5 to 0.8 dB by using a micro-optics composed of graded-index and coreless pure silica fibres. [ABSTRACT FROM AUTHOR]

A high-speed uni-travelling-carrier photodiode module that operates at ultra-low temperatures is developed. The fabricated module has a very stable optical connection in the temerature range from 300 to 15 K. [ABSTRACT FROM AUTHOR]

Group delay and chromatic dispersion of a Fabry-Pérot resonator embedded in a photonic crystal waveguide have been directly measured at 1.55 µm wavelength using the phase-shift technique. The photonic crystal waveguide resonator was fabricated in an InGaAsP/InP heterostructure and was designed to show a channel spacing of 100 GHz. Group velocity dispersion up to 250 ps/nm was observed. [ABSTRACT FROM AUTHOR]

Kilowatt peak power pulses with pulse durations of approximately 1.5 ps within 5% of transform limit using an all-fibre stretch pulse amplification system are demonstrated. Efficient high-quality stretch pulse amplification is achieved using a matched chirped fibre Bragg grating and low nonlinearity photonic-bandgap hollow-core fibre. The nearly ideal recompression highlights the robustness of ultra-short picosecond pulses to group delay ripple in chirped fibre gratings. [ABSTRACT FROM AUTHOR]

An experimental demonstration is given of the use of a transversal RF photonic filter to accomplish intermodal dispersion equalisation in a 10 Gbit/s optical fibre link using a Fabry-Perot laser. The structure operates in an equivalent fashion to an electronic equaliser but in the photonic domain. A record distance of 24.2 km using the equalising filter is obtained. [ABSTRACT FROM AUTHOR]

A novel scheme of optical label recognition using additional pre-spread coding is proposed. This method can realise both high recognition power and data transmission efficiency. The recognition power of this method is shown by simulation and its optical implementation is presented. [ABSTRACT FROM AUTHOR]

A VCSEL structure with output coupling to an internal waveguide using integrated diffraction gratings has been demonstrated. The design and fabrication of the monolithically integrated structure, including epitaxial regrowth, is discussed and initial device characteristics are presented. While horizontal waveguides can be used to route optical signals between monolithically integrated components, a small amount of transmission is retained in the top DBR to enable on-wafer testing. This monolithic structure has the potential to enable VCSEL- based photonic integrated circuits on GaAs. [ABSTRACT FROM AUTHOR]

It is shown how standard physical optics formulations can easily be adapted to perform near-field computations by introducing locally expanded phase approximations used in conjunction with surface partitioning. This approach leads to a more robust radiation procedure while preserving the simplicity of standard physical optics expressions. [ABSTRACT FROM AUTHOR]

An 80 × 80 port free space crossconnect that uses individual collimators and beam steering micromirrors is presented. The switch uses a design with beams converging on the micromirrors, which leads to a small footprint of 50 × 40 × 20 mm³, and an optimal use of the tilt angle range of the micromirrors. The switch exhibits a mean insertion loss of 2.5 dB, and a crosstalk rejection better than 60 dB. [ABSTRACT FROM AUTHOR]

The article reports on developments in the semiconductor and integrated optoelectronics industry. He discusses the Semiconductor and Integrated Optoelectronics conference in Cardiff and the theme of integration. He comments on the development of the Digital Supermode Distributed Bragg Reflector and on the need for green photonics.