Michael R. Wang

Guided-wave planar optical interconnects using highly multiplexed polymer waveguide holograms

An intraplanar interconnection scheme using substrate guided modes in conjunction with a highly multiplexed waveguide volume hologram is proposed. Acoustooptically addressed 1-to-50 passive and 1-to-2-to-100 reconfigurable interconnections with a fan-out diffraction efficiency of 55% at 514-nm wavelength are demonstrated. A coordinate transformation converts the 3-D diffraction problem into a 2-D one, which significantly simplifies the theoretical calculation. Intraplane massive fan-out optical interconnection using substrate guided mode provides both collinear and coplanar fan-out capability for data and clock signals. Colinearity of signal distribution allows the 2-D input signal array to be processes. The laminated waveguide device containing a highly multiplexed dichromated gelatin (DCG) hologram has been evaluated. >

Laser direct-write gray-level mask and one-step etching for diffractive microlens fabrication

High-efficiency diffractive optical elements can be achieved by an increase in the number of phase levels. We present a technique for laser direct-write gray-level masks on high-energy-beam-sensitive glass and one-step etching on the gray-level mask plate for the production of high-efficiency diffractive optical elements. Sixteen-phase-level diffractive microlenses and microlens arrays with a focusing efficiency of approximately 94% have been realized by use of the one-step nonphotolithographic fabrication technique.

Large fanout optical interconnects using thick holographic gratings and substrate wave propagation

Substrate wave propagation and Bragg diffraction by multiplexed holographic gratings have been used to demonstrate a new 1-to-30 fanout optical interconnect having an overall diffraction efficiency of 87.8% at 514.5 nm and an individual channel efficiency of approximately 3.0 +/- 0.8%. The device configuration utilizes the large multiplexing capability of dichromated gelatin polymer films and substrate total internal reflection to realize large channel fanouts within the plane of a soda-lime glass substrate. A simplified theoretical formulation is presented to treat the corresponding three-dimensional holographic diffraction problem in the Bragg regime for slanted phase gratings. Results are compared with experimentally measured quantities for singly exposed phase gratings in different polarization conditions and incident angle orientations. The limitations of using multiplexed holograms in multiplanar substrate interconnection applications are also discussed.

Anterior Segment Biometry during Accommodation Imaged with Ultralong Scan Depth Optical Coherence Tomography

PURPOSE To measure by ultralong scan depth optical coherence tomography (UL-OCT) dimensional changes in the anterior segment of human eyes during accommodation. DESIGN Evaluation of diagnostic test or technology. PARTICIPANTS Forty-one right eyes of healthy subjects with a mean age of 34 years (range, 22-41 years) and a mean refraction of -2.5 ± 2.6 diopters were imaged in 2 repeated measurements at minimal and maximal accommodations. METHODS A specially adapted and designed UL-OCT instrument was used to image from the front surface of the cornea to the back surface of the crystalline lens. Custom software corrected the optical distortion of the images and yielded the biometric measurements. The coefficient of repeatability and the intraclass correlation coefficient were calculated to evaluate the repeatability and reliability. MAIN OUTCOME MEASURES Anterior segment parameters and associated repeatability and reliability upon accommodation. The dimensional results included central corneal thickness (CCT), anterior chamber depth and width (ACD, ACW), pupil diameter (PD), lens thickness (LT), anterior segment length (ASL = ACD + LT), lens central position (LCP = ACD + 1/2LT), and horizontal radii of the lens anterior and posterior surface curvatures (LAC, LPC). RESULTS Repeated measurements of each variable within each accommodative state did not differ significantly (P>0.05). The coefficients of repeatability (CORs) and intraclass correlation coefficients for CCT, ACW, ACD, LT, LCP, and ASL were excellent (1.2%- 3.59% and 0.998-0.877, respectively). They were higher for PD (18.90%-21.63% and 0.880-0.874, respectively) and moderate for LAC and LPC (34.86%-42.72% and 0.669-0.251, respectively) in the 2 accommodative states. Compared with minimal accommodation, PD, ACD, LAC, LPC, and LCP decreased and LT and ASL increased significantly at maximal accommodation (P<0.05), whereas CCT and ACW did not change (P>0.05). CONCLUSIONS The UL-OCT measured changes in anterior segment dimensions during accommodation with good repeatability and reliability. During accommodation, the back surface of the lens became steeper as the lens moved forward. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any of the materials discussed in this article.

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.

Characterization of Soft Contact Lens Edge Fitting Using Ultra-High Resolution and Ultra-Long Scan Depth Optical Coherence Tomography

PURPOSE To characterize the edge fitting of soft contact lenses using ultra-high resolution optical coherence tomography (UHR-OCT) and ultra-long scan depth optical coherence tomography (UL-OCT). METHODS A total of 20 participants (11 men, 9 women; mean age, 32.3 years) were recruited. Four different types of soft contact lenses were randomly fitted to both eyes of each subject on two separate visits. After 30 minutes, the horizontal meridians of the corneal center, midperiphery, and limbus were imaged by UHR-OCT. UL-OCT imaged each lens in vitro and the ocular surface of a physical model eye. RESULTS Angle-edged lenses had significantly less conjunctival buildup than did round-edged lenses (P = 0.008). Limbal post-lens tear film gaps were present in 42% of the eyes, with the round-edged lenses having the most at 68%. Similarly, post-lens tear film gaps at the corneal mid-periphery were present in 47% of all eyes, with the round-edged lens having the most at 75%. Mismatches between the lens and the ocular surface were simulated based on UL-OCT images of the in vitro lenses and the model eye. The existence of tear film gaps and touching points were predicted in the simulation. CONCLUSIONS The soft contact lens edge fitting was characterized by the conjunctival buildup and tear film gaps. Different types of contact lenses presented different levels of conjunctival buildup as well as different frequencies of tear film gaps. The findings by UHR-OCT were predicted in the simulation by UL-OCT. The application of these new technologies may open new ways of designing lenses and evaluating their fit.

SD-OCT with prolonged scan depth for imaging the anterior segment of the eye.

An 840-nm wavelength spectral domain optical coherence tomography (SD-OCT) with prolonged scan depth was developed and mounted onto a conventional slit lamp for imaging the anterior segment of the eye. X-Y cross aiming was applied to align the SD-OCT scanning position during imaging. An internal fixation target displayed on a miniature LCD monitor was provided. The SD-OCT instrument had an axial resolution of 6 μm and a prolonged scan depth of 7.2 mm. High-quality SD-OCT images, consisting of 2,048 × 2,048 pixels, were acquired of the entire anterior chamber and entire crystalline lens from a healthy subject. The entire cornea, anterior chamber angle, limbus, and iris were clearly visible. Additionally, the internal structure of crystalline lens, including anterior and posterior surfaces of the crystalline lens, capsule, nucleus, and cortex, were clearly imaged with the instrument. The system was also tested in imaging accommodation of the same eye, demonstrating the feasibility of the novel approach for evaluating presbyopia/accommodation.

Five-channel polymer waveguide wavelength division demultiplexer for the near infrared

A five-channel wavelength division demultiplexer (WDDM) fabricated in polymer gelatin waveguides and operating over a 100-nm bandwidth centered at 770 nm in the near infrared is discussed. The device has a maximum diffraction efficiency of 80% at 730 nm, has a spectral bandwidth of 17+or-3 nm per channel, and effectively utilizes a portion of the large optical transparency bandwidth ( approximately 2400 nm) of the photo-lime gelatin polymer material at laser diode wavelengths. High-channel-density WDDM devices at longer infrared wavelengths should be possible.<<ETX>>

Wavelength-division multiplexing and demultiplexing on locally sensitized single-mode polymer microstructure waveguides

A four-channel wavelength-division-(de)multiplexing [WD(D)M] device, operating over optical wavelengths of 543.0 to 632.8 nm, has been successfully fabricated on newly developed locally sensitized polymer (photo-lime gelatin) microstructure waveguides (PMSWs). The WD(D)M device exhibits a cross talk of less than -40 dB between adjacent channels and a diffraction efficiency of better than 50%. The angular and spectral bandwidths for the device are ~0.2-0.4 degrees and ~4-10 nm, respectively. Such sensitivities can significantly increase the WD(D)M channel density for optical interconnect architectures. Since the PMSW device can be constructed on a variety of substrates, including insulators, semiconductors, conductors, and ceramics, the demultiplexing technique that we report is suitable for use in a variety of optical-computing, signal-processing, and communication applications.

Entire contact lens imaged in vivo and in vitro with spectral domain optical coherence tomography.

Objectives To demonstrate the capability of directly visualizing the entire ocular surface and the entire contact lens on the eye using spectral domain optical coherence tomography (SD-OCT). Methods A custom-built, high–speed, and high-resolution SD-OCT was developed with extended scan depth and width. The eye was imaged before and after wearing a toric soft contact lens (PureVision; Bausch & Lomb). A lubricant eye drop (Soothe; Bausch & Lomb) was instilled in the eye to enhance the image contrast on the lens. The same toric soft contact lens immersed in the contact lens solution was also imaged with a contrast enhancement medium (0.5% Intralipid). Results Cross-sectional OCT images of the entire ocular surface were acquired with high-resolution 2,048 × 2,048 pixels. Quantitative surface height map of the ocular surface was obtained from a radial scan data set containing 32 B-scans. With the contrast enhancement agent, the entire toric soft contact lens was clearly visualized, both in vitro and on the eye. The surfaces of the lens were detected and used to generate the thickness maps of the soft contact lens. Conclusions Spectral domain optical coherence tomography with extended scan depth and width is a promising tool for imaging the entire ocular surface shape and soft contact lenses. This successful demonstration suggests that the extended depth SD-OCT is effective in studying ocular surface shape and its interaction with a soft contact lens. The novel method is helpful for the evaluation of contact lens fitting and lens design.