We report the realization and performance of a distributed feedback channel waveguide laser in erbium-doped aluminum oxide on a standard thermally oxidized silicon substrate. The diode-pumped continuous-wave laser demonstrated a threshold of 2.2 mW absorbed pump power and a maximum output power of more than 3 mW with a slope efficiency of 41.3% versus absorbed pump power. Single-longitudinal-mode and single-polarization operation was achieved with an emission linewidth of 1.70+/-0.58 kHz (corresponding to a Q factor of 1.14 x 10(11)), which was centered at a wavelength of 1545.2 nm.

We examine the use of two integrated-optical modulators operated in parallel to attain low-distortion analog optical transmission. This static feedforward approach achieves significantly improved linearity at the expense of small increases in the required optical power and moderate increases in the required drive voltage. A novel variation that uses the unique characteristics of an integrated-optical modulator to correct the dominant quadratic distortion of a directly modulated laser is proposed.

Abstract:We show that nano-mechanical interaction using atomic force microscopy (AFM) can be used to map out mode-patterns of an optical micro-resonator with high spatial accuracy. Furthermore we demonstrate how the Q-factor and center wavelength of such resonances can be sensitively modified by both horizontal and vertical displacement of an AFM tip consisting of either Si 3 N 4 or Si material. With a silicon tip we are able to tune the resonance wavelength by 2.3 nm, and to set Q between values of 615 and zero, by expedient positioning of the AFM tip. We find full on/off switching for less than 100 nm vertical, and for 500 nm lateral displacement at the strongest resonance antinode locations.

We report the fabrication and the characterization of the refractometric and thermo-optical properties of a quasi-one-dimensional waveguide photonic crystal-a strong, 76-m-long Bragg grating. The transmission spectra (around 660 nm) of the structure have been measured as a function of both the cladding refractive index and the temperature. The transmission stopband was found to shift by 0.8-nm wavelength for either a cladding refractive index change of 0.05 or a temperature change of 120 K. The steep stopband edges provide a sensitive detection method for this band shift, by monitoring the transmitted output power.

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Focused ion beam (FIB) milling is receiving increasing attention for nanostructuring in silicon (Si). These structures can for example be used for photonic crystal structures in a silicon-on-insulator (SOI) configuration or for moulds which can have various applications in combination with imprint technologies. However, FIB fabrication of submicrometre holes having perfectly vertical sidewalls is still challenging due to the redeposition effect in Si. In this study we show how the scan routine of the ion beam can be used as a sidewall optimization parameter. The experiments have been performed in Si and SOI. Furthermore, we show that sidewall angles as small as 1.5 • are possible in Si membranes using a spiral scan method. We investigate the effect of the dose, loop number and dwell time on the sidewall angle, interhole milling and total milling depth by studying the milling of single and multiple holes into a crystal. We show that the sidewall angles can be as small as 5 • in (bulk) Si and SOI when applying a larger dose. Finally, we found that a relatively large dwell time of 1 ms and a small loop number is favourable for obtaining vertical sidewalls. By comparing the results with those obtained by others, we conclude that the number of loops at a fixed dose per hole is the parameter that determines the sidewall angle and not the dwell time by itself.

Optical coherence tomography (OCT) has enabled clinical applications that revolutionized in vivo medical diagnostics. Nevertheless, its current limitations owing to cost, size, complexity, and the need for accurate alignment must be overcome by radically novel approaches. Exploiting integrated optics, we assemble the central components of a spectral-domain OCT system on a silicon chip. The spectrometer comprises an arrayed-waveguide grating with 136-nm free spectral range and 0.21-nm wavelength resolution. The beam splitter is realized by a non-uniform adiabatic coupler with its 3-dB splitting ratio being nearly constant over 150 nm. With this device whose overall volume is 0.36 cm(3) we demonstrate high-quality in vivo imaging in human skin with 1.4-mm penetration depth, 7.5-µm axial resolution, and a signal-to-noise ratio of 74 dB. Considering the reasonable performance of this early OCT on-a-chip system and the anticipated improvements in this technology, a completely different range of devices and new fields of applications may become feasible.

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