This paper presents a novel approach of mixing two laminar flowing streams in microchannels. The mixer consists of a pair of electrodes disposed along a fluidic channel. By energizing the electrodes with a DC-biased (2.5 V) AC voltage (20 Vpp), an electrokinetic flow is induced with a flow profile perpendicular to that of the incoming laminar streams of liquids to be mixed. As a result, the flow lines of the incoming streams and the induced flow are forced to crossover and very efficient stirring and mixing at short mixing length can be achieved. The mixer can be operated from the AC-electroosmotic (ACEO) (sigma=1 mS/m, f=100 kHz) to the AC-electrothermal (ACET) (sigma=500 mS/m, f=500 kHz) flow regimes. The mixing efficiency in the ACEO regime was 92%, with a mixing length of 600 microm (Q=2 microL/min), an estimated mixing time of 69 ms and an induced ACEO flow velocity of approximately 725 microm/s. The mixing efficiency in the ACET regime was 65% for a mixing length of approximately 1200 microm. The mixer is efficient and suitable for mixing reagents in a fluid media from low to high conductivity as required in diverse microfluidic applications.

We show that rubidium vapor can be produced within the core of a photonic band-gap fiber yielding an optical depth in excess of 2,000. Our technique for producing the vapor is based on coating the inner walls of the fiber core with organosilane and using light-induced atomic desorption to release Rb atoms into the core. As an initial demonstration of the potential of this system for supporting ultralow-level nonlinear optical interactions, we perform electromagnetically induced transparency with control-field powers in the nanowatt regime, which represents more than a 1,000-fold reduction from the power required for bulk, focused geometries.

In this letter, based on the beam theory and the thermal analysis of a bimaterial cantilever, we demonstrate that the effective thermal conductance of the cantilever and the temperature at the tip of the cantilever can be determined by measuring the bending of the cantilever in response to two different thermal inputs: power absorbed at the tip and ambient temperature.

We show that a Rubidium vapor can be produced within the core of a photonic band-gap fiber yielding an optical depth in excess of 2000. Our technique for producing the vapor is based on coating the inner walls of the fiber core with an organosilane and using light-induced atomic desorption to release Rb atoms into the core. We develop a model to describe the dynamics of the atomic density, and as an initial demonstration of the potential of this system for supporting ultra-low-level nonlinear optical interactions, we perform electromagnetically-induced transparency with control-field powers in the nanowatt regime, which represents more than a 1000-fold reduction from the power required for bulk, focused geometries. 1Remarkable advances have been made in the past decade in generating and controlling quantum states of light using atomic vapors, including the realization of on-demand singlephoton sources [1], manipulation of photonic states [2], and storage and retrieval of the states with high fidelity [3,4]. Much of the motivation for these efforts has been to realize a practical quantum network [5]. In most cases, the underlying optical process for realizing these schemes has been the phenomenon of electromagnetically-induced transparency (EIT) [6] in which a coherent superposition of atomic states is created by a strong control field such that an optically thick atomic ensemble is rendered transparent to a weak, resonant probe field.The concept of EIT has been applied and expanded to schemes that allow two extremely weak fields, which in principle can consist of single photon pulses, to strongly interact [7,8,9,10].Practical implementation of these proposals in which a single photon can switch another photon will lead to the realization of critical components (e.g., a quantum phase gate) for quantum information applications [11].The two generic requirements to achieve EIT-based, ultralow-level optical interactions are: 1) a large optical depth κ = nLσ, where n is the density of the atomic sample of length L, and σ is the atomic absorption cross-section, and 2) confinement of the light beams to an area A comparable to the atomic scattering cross-section of 3λ 2 /2π [8,9,10,12]. For example, the phase shift due to nonlinear interactions between few photon-pulses in the proposed scheme of André et al. [10] and the inverse of the critical power required to switch a signal field in the four-level scheme of Harris and Yamamoto [8] are each proportional to κ/A. In order to maximize the optical depth, a natural choice for the atomic ensemble is an alkali atom due to its relatively simple energy-level structure and its large σ as compared to, for example, molecules with ro-vibrational transitions [13]. There is a limit on how much κ can be increased by increasing the density n since this will result in undesirable dephasing effects due to atomic collisions. Alternatively, increasing the length L of the atomic sample can further enhance the optical depth. However, in a bulk focused geometry, this length L is limited to t...