A simple method for increasing the thermal efficiency of shape bimorph electrothermal micro-actuators is proposed, based on a reduction of gas conduction cooling beneath the hot arms by a deep, localized undercut. A single-sided, single-mask SCREAM-type process for fabricating differentially cooled actuators in a bonded silicon-on-insulator material is demonstrated. The process uses deep reactive ion etching and undercut to form suspended parts and isotropic reactive ion etching and lift-off of sacrificial shields to form localized mesas. The advantage of the method is confirmed using folded electrothermal actuators, and an approximate halving of the drive power is demonstrated by variations in the substrate profile in the vicinity of a series of actuators with the same mechanical design.
A tunable laser containing a recently developed travelling wave semiconductor optical amplifier (SOA) of the red spectral region as an active element and an acousto-optic tunable filter in an external fibre ring cavity is studied. Continuous wavelength tuning was achieved within a spectra band up to 20 nm wide with a rate up to 104 nm s−1 at a spectral linewidth below 0.04 nm and a cw output power up to 2 mW. The use of one more similar SOA as an output power amplifier made it possible to increase the output power to 15 mW.
The power and spectral characteristics of near-IR superluminescent diodes (SLDs) based on asymmetric double-quantum-well GaAs/InGaAs heterostructures are studied experimentally. It is shown that, varying the active layer composition and the spatial-single-mode active channel length of these SLDs, it is possible to widely change the achievable output optical power and the spectral width of the symmetric bell-shaped spectrum. The studied SLDs have a lower coherence function pedestal, a weaker dependence of the spectral width on the injection current, and a higher polarisation degree than the widely spread SLDs based on single-quantum-well heterostructures with the same spectral widths.
In this paper, we adopt the Nernst-Planck equation and the full Navier-Stokes equation in the modeling of electro-osmotic flow in microfluidic chips. A voltage control model is proposed, which achieves electrokinetic focusing in a pre-focused cross injection system and which allows the volume of the sample to be controlled. In addition to the traditional cross system, we also present a design for a novel pre-focused 1 × 3 (i.e. one sample inlet port and three outlet ports) injection system, which is capable of continuous sample switching and injection for bio-analytical applications. Using the proposed injection system, the sample may be electrokinetically pre-focused and then guided into the required outlet port by suitable manipulations of the applied voltage. The unique microfluidic chip presented within this paper has an exciting potential for use in high-throughput chemical analysis, fast sample mixing and many other applications in the field of micro-total-analysis systems.
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