MEMS-actuated wavelength drop filter based on microsphere whispering gallery modes

MEMS-enabled tuneable optical coupling between optical microsphere resonators and optical fibre waveguides is reported. We describe the design, fabrication and experimental characterization of a MEMS platform, based on electrothermal actuators, which controls the resonator-to-waveguide separation. We compare the simulated and experimental displacements of the actuators in an unloaded and loaded state, where the load is a 1 mm optical spherical resonator. We then demonstrate the proof of concept application of selective wavelength dropping using the MEMS platform by modulating the coupling between the spherical resonator and a tapered optical fibre waveguide

Probing Small-Molecule Microarrays with Tagged Proteins in Cell Lysates

The technique of small-molecule microarray (SMM) screening is based on the ability of small molecules to bind to various soluble proteins. This type of interaction is easily detected by the presence of a fluorescence signal produced by labeled antibodies that specifically recognize a unique sequence (tag) present on the target protein. The fluorescent signal intensity values are determined based on signal-to-noise ratios (SNRs). SMM screening is a high-throughput, unbiased method that can rapidly identify novel direct ligands for various protein targets. This binding-based assay format is generally applicable to most proteins, but it is especially useful for protein targets that do not possess an enzymatic activity. SMMs enable screening a protein in a purified form or in the context of a cellular lysate, likely providing a more physiologically relevant screening environment.National Cancer Institute (U.S.) (CA160860

Demodulation of polarimetric fibre laser ultrasonic sensor with intensity noise cancellation

In this paper, the influences of the relative intensity noise (RIN), in particular the relaxation oscillation noise, of an erbium distributed feedback (DFB) fibre laser has been investigated theoretically and experimentally for use a polarimetric ultrasonic sensor. We show that the relaxation oscillation noise and the ultrasonic signal both induce modulation sidebands on the polarization beat frequency of the DFB laser ultrasonic sensor. We present a novel demodulation algorithm for the polarimetric DFB fibre laser ultrasonic sensor, which can effectively eliminate the influences of the intensity noise and slowly varying drift of the polarization beat frequency

Modeling and characterization of an electrowetting based single mode fiber variable optical attenuator

We report an optofluidics-based variable optical attenuator (VOA) employing a tapered side-polished single-mode optical fiber attached to an electrowetting-on-dielectric (EWOD) platform. The side polishing of the fiber cladding gives access to the evanescent field of the guided mode, while the EWOD platform electrically controls the stepwise translation of a liquid droplet along the variable thickness polished cladding of the fiber. The penetration of the evanescent field into the droplet leads to tunneling of optical power from the fiber core to the droplet, from where it is radiatively lost. As a result of the variable cladding thickness, the position of the droplet along the length of the polished fiber determines the degree of penetration of the evanescent field into the droplet. The droplet position can be electrically changed; thus, controlling the optical power loss from the fiber. This approach has been used to demonstrate an optofluidic continuous-fiber VOA typically providing up to 26 dB of broadband attenuation in the 1550-nm transmission window, with a wavelength dependent loss less than 1.1 dB. In this paper, we present the theoretical modeling and experimental characterization of the system, discussing the influence of the design parameters on the performance of this VOA

In-line single-mode fiber variable optical attenuator based on electrically addressable microdroplets

We report an in-line, fiber optic, broadband variable optical attenuator employing a side-polished, single-mode optical fiber integrated on a digital microfluidics platform. The system is designed to electrically translate a liquid droplet along the polished surface of an optical fiber using electrowetting forces. This fiber optic device has the advantage of no moving mechanical parts and lends itself to miniaturization. A maximum attenuation of 25 dB has been obtained in the wavelength range between 1520 nm and 1560 nm

Influence of microphone housing on the directional response of piezoelectric mems microphones inspired by Ormia ochracea

The influence of custom microphone housings on the acoustic directionality and frequency response of a multiband bio-inspired MEMS microphone is presented. The 3.2 mm by 1.7 mm piezoelectric MEMS microphone, fabricated by a cost-effective multi-user process, has four frequency bands of operation below 10 kHz, with a desired first-order directionality for all four bands. 7×7×2.5 mm3 3-D-printed bespoke housings with varying acoustic access to the backside of the microphone membrane are investigated through simulation and experiment with respect to their influence on the directionality and frequency response to sound stimulus. Results show a clear link between directionality and acoustic access to the back cavity of the microphone. Furthermore, there was a change in direction of the first-order directionality with reduced height in this back cavity acoustic access. The required configuration for creating an identical directionality for all four frequency bands is investigated along with the influence of reducing the symmetry of the acoustic back cavity access. This paper highlights the overall requirement of considering housing geometries and their influence on acoustic behavior for bio-inspired directional microphones

A MEMS microphone inspired by Ormia for spatial sound detection

This work introduces a MEMS microphone with two pairs of orthogonal and joined sensor membranes, with independent acoustic directionality responses, leading to a 3D sound localization potential. This single microphone can thus be regarded as two individual bi-directional microphones. Combining this architecture with the fly Ormia ochracea’s tympana mechanism, this microphone is also the first biomimetic MEMS microphone with piezoelectric sensing, designed for 2D sound localization

A low frequency dual-band operational microphone mimicking the hearing property of Ormia ochracea

This paper introduces a directional MEMS microphone designed for hearing aid applications appropriate to low frequency hearing impairment, inspired by the hearing mechanism of a fly, the female Ormia ochracea. It uses both piezoelectric and capacitive sensing schemes. In order to obtain a high sensitivity at low frequency bands, the presented microphone is designed to have two resonance frequencies below the threshold of low frequency hearing loss at approximately 2 kHz. One is around 500 Hz and the other is slightly above 2 kHz. The novel dual sensing mechanism allows for optimization of the microphone sensitivity at both frequencies, with a maximum open-circuit (excluding pre-amplification) acoustic response captured via differential piezoelectric sensing at approximately – 46 dB (V) ref. 94 dB (SPL) at the resonance frequencies. The corresponding minimum detectable sound pressure level is just below -12 dB. The comb finger capacitive sensing was employed due to a lower electrical response generated from a ground referenced single-ended output by the piezoelectric sensing at the first resonance frequency compared to the second resonance frequency. The capacitive sensing mechanism, connected to a charge amplifier, generates a -28.4 dB (V) ref. 94 dB (SPL) acoustic response when the device is excited at either of the two resonance frequencies. Due to the asymmetric geometry and the 400 µm thick substrate, the device is predicted to perform as a bi-directional microphone below 3 kHz, which is shown by the measured directional polar patterns

Effects of laser intensity noise on polarimetric distributed feedback fibre laser ultrasonic sensor

The influence of the relative intensity noise, in particular the relaxation oscillation noise, of a distributed feedback (DFB) fibre laser on the performance of a polarimetric DFB fibre laser ultrasonic sensor is investigated theoretically and experimentally. A novel demodulation algorithm for the DFB fibre laser ultrasonic sensor is used to demodulate the polarization beat frequency and eliminate the effects of the intensity noise completely. The sensing system is demonstrated to demodulate time varying ultrasonic signals at 2.25 MHz and 10 MHz

Housing influence on multi-band directional MEMS microphones inspired by Ormia ochracea

A new bio-inspired multi-band directional MEMS microphone based on the hearing properties of the fly Ormia ochracea is presented, together with the behavioral influence of 3D-printed housings. The multi-user foundry fabricated microphone operates on four frequency bands, all below 10 kHz and acts as a pressure gradient directional microphone with figure of eight polar pattern, or as an omni-directional microphone depending on the housing. The influence of an open or closed backside housing on the frequency response and directionality is shown, leading to the loss of directionality with no acoustic access to the backside of the fly-ear inspired microphone membrane