We propose an integrated microfluidic optical system device design for a monolithic integration of blood plasma analysis in a single step using microfluidic channels on a tri wavelength LED source emitting wavelengths in ultraviolet, infrared and visible. The device is a miniature disposable Lab-on-a-Chip as small as 6x 1.5mm with a blood plasma reservoir volume of 2μl providing instantaneous results. The device is fabricated using minimal lithographic fabrication steps and consists of a microfluidic Polydimethylsiloxane (PDMS) layer on top of a quantum well (QW) structure. The PDMS layer has three 100μm thick microfluidic channels connected to the 2μl reservoir where the blood plasma is injected. The three microfluidic channels pass over the QW substrate which is micro fabricated to produce three LEDs that emit light in three different wavelengths on a single structure. The LEDs emit light in UV, infrared and visible and can be controlled individually for specific plasma testing or can emit light simultaneously depending on the application. To operate the device, first current is injected into the LEDs to turn on light emission. Light travels within the LED structure and at the same time light is emitted through the surface. Light can be either collected from the top of the device or the output facets by focusing the channels output on a spectrometer to collect the spectra of the device and analyze the output. The device is compact in size and provides fast, low power consumption and cost effective point of care devices with minimal heat output.
A monolithic multi-wavelength LED based on selective dielectric cap intermixing is investigated experimentally. The proposed LED is fabricated on a QW structure and it has an independent wavelength intensity power control for each wavelength. The device consists of three regions that have been intermixed to varying extents of SiO2 thicknesses then annealed at 975°C for 20s.The regions are blue shifted by amounts that depend on the thickness of a SiO2 capping film. Contact stripes are then evaporated on each region as intensity power control to emit its respective wavelength. Experimental results showed an independently tri-wavelength emission of 797nm, 780nm and 775nm.
A monolithic tunable laser on a quantum well (QW) structure is demonstrated by integrating an optical beam-steering section with an area-selectively intermixed QW gain section. Wavelength tuning is achieved by guiding an amplified optical beam over an optical gain medium that consists of three laterally adjacent regions containing a quantum well that has been selectively intermixed to varying extents. The laser light output can be tuned over a total of a 17-nm wavelength range by separately injecting electrical current pulses to each of the two parallel contacts in the steering region and to the optical amplifier contact.
A monolithically integrated multi-wavelength LED based on selective dielectric cap intermixing is investigated experimentally. The proposed LED emits radiation with multiple wavelength peaks from one compact easy to fabricate quantum well (QW) structure. Each wavelength has an independent emission power control, allowing the LED to radiate one or more wavelengths simultaneously. The LED material is an AlGaAs/GaAs QW p-i-n heterostructure. The device is divided into three selectively intermixed regions using an impurity-free vacancy induced intermixing technique creating localized intermixed areas. Each region is intermixed to varying extent resulting in different luminescence peaks and by separately addressing each section with its electrical current, the net emission spectrum can be fully controlled. The fabrication process starts with the growth of a 400nm thick layer of SiO<sub>2</sub> over the whole sample using plasma enhanced chemical vapor deposition. Three regions with different SiO<sub>2</sub> thicknesses are defined via two photolithographic and subsequent reactive ion etching steps. The sample is then annealed at 975°C for 20s to activate the intermixing of the constituent atoms of the quantum well and barrier materials. The degree of intermixing is determined by the thickness of the SiO<sub>2</sub> cap. After removal of the SiO<sub>2</sub> cap, contact stripes are evaporated on each region to act as an independent intensity power control for that region. Experimental results have shown that a controllable 10nm, 21nm and 33nm blue shifts of the peak wavelength of emission from that of the as-grown sample corresponding to 0, 100nm, and 400nm thick SiO<sub>2</sub> caps respectively.
A broadly tunable MQW laser utilizing a combined impurity-free vacancy disordering and beam steering techniques is
proposed and investigated experimentally. The device consists of a beam-steering section and an optical amplifier
section fabricated on a GaAs/AlGaAs MQW p-i-n hetrostructure substrate. The beam steering section forms a
reconfigurable single mode waveguide that can be positioned laterally by applying electrical currents to two parallel
contact stripes. The active core of the gain section contains a GaAs/AlGaAs MQW that is progressively disordered such
that an optical beam steered through the selected region experience a peak in the gain spectrum that is determined by the
degree of disordering of the MQWs. Furthermore the MQW in the beam-steering section is disordered to the largest
extent to minimize optical beam attenuation. The MQW structure was intermixed using an impurity-free vacancy
induced disordering technique. The MQW sample is encapsulated with a SiO<sub>2</sub> film grown by plasma enhanced chemical
vapor deposition (PECVD). The beam steering region is coated with a 400nm thick SiO<sub>2</sub> film whereas in the gain
section, the SiO<sub>2</sub> film is selectively etched such that the thickness grades linearly ranging from 0 to 325nm. The
disordering of the entire slab region is then induced by a single rapid thermal annealing step at 975°C for a 20s.
Experimental results showed a controllable 10 to 60 nm wavelength blue shift of the peak of the photoluminescence
spectrum corresponding to the change in SiO<sub>2</sub> caps thickness and a lateral beam steering range up to 20 μm over the slab
A platform that enables optical coupling from fiber-ribbon connectors to planar lightwave circuits (PLCs) is described. Flexible optical waveguides are used to form a variable length directional coupler that inserts and extracts light from a waveguide located arbitrarily inside the chip. The contact length can be adjusted for optimal coupling allowing manufacturing variation in materials, widths and cladding thicknesses present on a chip. This approach may be ideal for packaging WDM devices as the 3dB bandwidth of the coupling covers the whole 1300 -1700 nm fiber-optic telecommunication range. Coupling length control in the range of 0.05-0.2 μm leads to maximum coupling in excess of 80% for the range of conditions investigated. Simulations of the performance are discussed and initial fabrication and optical coupling results are presented.