Jame J. Yang

Achromatic hybrid refractive-diffractive lens with extended depth of focus

A method for designing achromatic hybrid refractive-diffractive elements that can produce beams with long focal depths while they preserve the entire aperture for capture of light and high transverse resolution is presented. Its working principle is based on the combination of a diffractive optical element that generates a long range of pseudonondiffractive rays and a refractive lens of opposite dispersion to form an achromatic hybrid lens. A hybrid lens with a fast f-number (f/1) that works in the entire visible wave band (400-700 nm) was designed and fabricated. Simulation results demonstrate a factor-of-10 improvement in depth of focus compared with that of a conventional f/1 lens, with matching 1-microm lateral resolution. Experimental results confirm the effectiveness of the proposed method through demonstration of an achromatic hybrid lens with better than a factor-of-7 improvement in depth of focus and 1-microm transverse resolution.

High-Speed Optical Interconnect Coupler Based on Soft Lithography Ribbons

In this paper, high-speed optical ribbon couplers for card-to-backplane interconnect applications are presented. The ribbon couplers are based on evanescent coupling between flexible multimode waveguide arrays. A soft lithographic technique is utilized to fabricate the ribbons. A flexible nonterminating optical data bus has been developed. Using BeamPROP software, we simulated the evanescent light coupling between two closely spaced ribbon waveguides to study the effects of waveguides separation, interaction length, and misalignment on coupling efficiency. Further experimental analysis and tests have been performed to quantify these effects. To investigate data transmission performance, a 12-channel optical interconnect link has been assembled. Experimental results demonstrated successful evanescent coupling; facilitating auto alignment coupling between card and backplane ribbon waveguides at data speeds as high as 10 Gb/s per channel. The evident high-speed interconnect performance and rapid ribbon prototyping approach can result in overall lower cost coupler fabrication for prospective optical interconnect applications.

Array waveguide evanescent ribbon coupler for card-to-backplane optical interconnects

A flexible array waveguide evanescent coupler for card-to-backplane optical interconnects is presented. The proposed technique eliminates traditional 90 degrees out-of-plane turns and local waveguide termination of multidrop bus architectures that hinder conventional card-to-backplane optical interconnections. Evanescent coupling between array waveguide ribbons has been successfully demonstrated. Further experiments have been performed to quantify array waveguide coupling length versus transfer efficiency and waveguide misalignment tolerance. Preliminary optical interconnect testing has demonstrated 2.5GHz operation of the coupler ribbons. The successful high-speed coupling confirms the effectiveness of the proposed method for high-speed computing systems.

Wavelength-multiplexed submicron holograms for disk-compatible data storage

By using a hybrid diffractive and refractive achromat with extended depth of focus, we have successfully recorded a micro-hologram array with diffraction-limited individual spot size maintained throughout the thickness of recording medium. An electrically programmable wavelength combiner was constructed in which a white light source was adopted. By modifying on a commercial CD readout head, we configured a compact micro-hologram recording/readout system that is compatible to existing disk storage technology. Base on the wavelength combiner and recording/readout system, wavelength-multiplexed micro-holograms were recorded and recovered. The presented results demonstrate the practicality of our novel storage architecture.

Dynamic spectral imaging with spectral zooming capability

We report a dynamic spectral imaging system with spectral band zooming and selection capability that can adapt to different application requirements and significantly reduce the size of the captured spectral image data cube. It employs a diffraction grating to disperse the spectral information of the captured image and uses a dynamic spatial filter at the Fourier plane to select the spectral channel and spectral bandwidth for each spectral image. With a limited fixed spectral channel number, it can provide both coarse and fine spectral image viewing and capture. A prototype spectral imaging system with such spectral band zooming and selection features has been constructed. Spectral zooming from 9 to 50 nm resolution has been demonstrated.

Agile dual-channel spectral imaging with spectral zooming

A dual-channel spectral imaging system with agile spectral band access and spectral bandwidth tuning capability is presented. A diffractive grating and an acousto-optic tunable filter (AOTF) are respectively used as spectral dispersion and spectral filtering elements for the two channels. A 4f spectral filtering channel using an adjustable slit is set up at the first diffraction order of the grating to realize coarse spectral band selection. The AOTF selectively filters the spectrum of the nondispersed zero order to realize fine spectral imaging. The spectral zooming function is achieved without increasing spectral frame number facilitating real-time spectral imaging operation. Feasibility of the spectral imaging has been demonstrated through preliminary experiments. Minimum 6 nm spectral resolution and 1.2 degrees field of view have been achieved. The real-time spectral imaging capable of wide spectral band operation without loosing desired fine spectral capability is particularly useful for a variety of defense, medical, and environmental monitoring applications.

Infrared imaging lens with extended depth of focus

An infrared imaging lens that produces beams with long focal depth whilst preserving the entire aperture for full light capturing and high transverse resolution is presented. It is a diffractive optical element that generates a long range of pseudo-non-diffractive rays. The design technique is based on the conjugate-gradient algorithm. The surface relief pattern was generated on a thick film photoresist and then the pattern was transferred to germanium substrate. Preliminary experimental results demonstrated four times improvement in depth of focus at 10.6 μm wavelength.

Laser writing of polymeric channel waveguides for optical interconnect packaging

We report on optical interconnection using laser direct writing on polymeric channel waveguides. The optical transmitters and receivers are designed and fabricated using commercially available integrated circuits. The optical interconnect packaging is achieved by laser writing the packaged polymeric channel waveguides from the pre-connected optical transmitters to the receivers with transmitters and receivers turned on to monitor the optical interconnection and packaging process.

Dynamic multispectral imaging remote sensor with spectral zooming capability

We successfully demonstrated a multispectral remote sensing system based on our reported spectral imaging design. Dynamic spatial filters such as electronically selected slits were used to select desired bandpass spectrum at a Fourier plane of its optical system. Minimum 9 nm spectral resolution and 0.6° field of view has been achieved. In addition, compact prototype system packaging with a dimension of 17×11×8 inch has been attained. The real-time spectral imaging system capable of wide spectral band operation with simultaneous fine spectral resolution is particularly useful for a variety of defense, medical, and environmental monitoring applications.

Wide field-of-view target tracking sensor

Surveillance and tracking of targets such as sensor fused warheads (SFWs) and unmanned aerial vehicles (UAVs) has been a challenging task, especially in the presence of multiple targets moving at a relatively fast speed. Due to the insufficient wavelength resolution, conventional radar technology may fail to resolve closely located targets or lack spatial resolution for specific target identification. There is a need for the development of an innovative sensor that is able to recognize and track closely related targets. To address this need, we have developed a target sensor that combines vision and laser ranging technologies for the detection and tracking of multiple targets with wide viewing angle and high spatial resolution. Using this sensor, regions-of-interest (ROIs) in the global scene are first selected, and then each ROI is subsequently zoomed with vision technique to provide high spatial resolution for target recognition or identification. Moreover, vision technique provides the azimuth and elevation angles of targets to a laser range finder for target distance determination. As a result, continuous three-dimensional target tracking can be potentially achieved with the proposed sensor. The developed sensor can be suitable for a wide variety of military and defense related applications. The design and construction of a proof-of-concept target tracking sensor is described. Basic performance of the constructed target tracking sensor including field-of-view, resolution, and target distance are presented. The potential military and defense related applications of this technology are highlighted.