James R. Busch

Correlator based on an integrated optical spatial light modulator

The fabrication and characterization of a 17.5-M bit/sec integrated optical correlator are described. The correlator makes use of a novel programmable electrooptic spatial light modulator in conjunction with a digitally modulated surface acoustic wave.

Integrated optic sensor with macro-flow cell

An integrated-optic channel waveguide device is configured as a biosensor. The device measures a refractive index change on the waveguide surface, so it is called a biorefractometer. With an appropriate overlay or selective coating, the device can monitor proteins in blood or pollutants and bio-warfare agents in water. We describe the design, fabrication, and testing of a sensor employing a waveguide Mach-Zehnder interferometer configuration. The device is fabricated in a glass substrate using potassium ion exchange. A patterned glass buffer layer defines the sensing and reference arms of the interferometer. A silicone-rubber macro-flow cell confines the liquid above the integrated-optical waveguide device. Salt solution data show that the biorefractometer has a sensitivity ((Delta) neff/(Delta) nLiquid) of 2 X 10-3 and can measure refractive index changes of about 0.005. Data obtained for antigen-antibody binding of the protein IgG indicate that a 10 percent signal change occurs in approximately 1 minute for a 10 (mu) g/ml concentration level.

Rectangular Luneburg-type lenses for integrated optics.

Compact Luneburg-type lenses of rectangular outline as viewed from above have been made by thermal evaporation of As2S3 glass onto single-mode LiNbO(3):Ti waveguides through suitably shaped masks and subsequent exposure of the glass to ultraviolet light. The best lenses had speeds of f/5.5 at an aperture of 10 mm and focal spots at reduced aperture about 1.2 times the diffraction-limited size. These lenses have a field of view of at least 25 degrees inside the waveguide.

Integrated Optic Biosensor for Environmental Monitoring

An integrated-optic biosensor monitors the concentration of liquid pollutants on the surface of a planar substrate composing single-mode channel waveguides. The concept uses a Mach- Zehnder interferometer structure to measure thickness and/or refractive index changes on the waveguide surface. These changes occur as pollutant molecules interact directly with the interferometers active arm or with a hydrophobic coating on the surface of the arm. Interferometer output data were obtained for various solutions including PPM levels of benzene and toluene in water. Theoretical analysis indicated that a hydrophobic coating on the waveguide would provide sensor specificity and detect pollutants at PPB levels.

Lithium niobate waveguides and their susceptibility to optical damage

Abstract The laser power-handling characteristics of diffused lithium niobate waveguides are reviewed in terms of laser-power-coupled, transmission length, crystal orientation, and method of preparation. Laser-induced optical damage is recorded for the first time in the new proton-exchanged lithium niobate waveguides. Optical damage is not observed, however, for propagation along the z-axis of titanium-in-diffused waveguides.

An integrated optical spatial filter

Abstract The demonstration of a static integrated optical spatial digital filter based upon the Bragg effect is reported and a design for a programmable filter is suggested.

Integrated optic sensor for measuring aflatoxin-B1 in corn

An integrated optic refractometer device was developed to perform a rapid one-step, homogeneous immunoassay. The device measures refractive index changes at the surface of a planar, singlemode, ion-exchange waveguide using difference interferometry. Anti-aflatoxin- B1 antibodies were attached to the waveguide surface to provide a bioselective coating for detecting and quantifying the aflatoxin-B1 antigen level in a sample. The detection limit of this small antigen must be determined using a competitive assay format. To determine feasibility of the competitive assay, we determined the biosensor response to a larger molecular weight competing antigen, namely HRP-labeled aflatoxin-B1. This labeled antigen will compete with unlabeled aflatoxin for binding sites on the sensor surface. Increased sample aflatoxin levels will result in a decreased time-dependent phase change of the helium-neon laser light beam. Phase change data were determined for various concentration levels of HRP-labeled aflatoxin- B1 antigen. The assay measurements were made over a 5-minute time period. Results indicated that a competitive assay is feasible. Future assay efforts should be able to demonstrate measurement of aflatoxin-B levels found in contaminated corn samples.

Integrated optic biosensor

A micro-sized biosensor is formed using integrated-optic channel waveguides in a Mach- Zehnder interferometer configuration. The device measures refractive index changes on the waveguide surface, so it is called a biorefractometer. With an appropriate overlay or selective coating, the sensor can monitor proteins in blood or pollutants and bio-warfare agents in water. The waveguides are fabricated in a glass substrate using potassium ion exchange. A patterned glass buffer layer defines the interferometers sensing and reference arms. A silicone-rubber cell arrangement brings sample analytes into contact with proteins immobilized on the integrated-optical waveguide surface. Data obtained for antigen-antibody binding of the proteins human Immunoglobulin-G and staph enterotoxin-B indicate that a 50 - 100 ng/ml concentration levels can be measured in less than ten minutes.

Engineered thin film lithium niobate substrate for high gain-bandwidth electro-optic modulators

This paper reports the demonstration of a high-speed electro-optic modulator in crystal ion sliced thin film lithium niobate (TFLN™). Experimental results indicate potential to realize a 100 GHz TFLN™ modulator at 1550 nm with V_π = 2.5V.

Integrated RF photonic devices based on crystal ion sliced lithium niobate

This paper reports on the development of thin film lithium niobate (TFLN™) electro-optic devices at SRICO. TFLN™ is formed on various substrates using a layer transfer process called crystal ion slicing. In the ion slicing process, light ions such as helium and hydrogen are implanted at a depth in a bulk seed wafer as determined by the implant energy. After wafer bonding to a suitable handle substrate, the implanted seed wafer is separated (sliced) at the implant depth using a wet etching or thermal splitting step. After annealing and polishing of the slice surface, the transferred film is bulk quality, retaining all the favorable properties of the bulk seed crystal. Ion slicing technology opens up a vast design space to produce lithium niobate electro-optic devices that were not possible using bulk substrates or physically deposited films. For broadband electro-optic modulation, TFLN™ is formed on RF friendly substrates to achieve impedance matched operation at up to 100 GHz or more. For narrowband RF filtering functions, a quasi-phase matched modulator is presented that incorporates domain engineering to implement periodic inversion of electro-optic phase. The thinness of the ferroelectric films makes it possible to in situ program the domains, and thus the filter response, using only few tens of applied volts. A planar poled prism optical beam steering device is also presented that is suitable for optically switched true time delay architectures. Commercial applications of the TFLN™ device technologies include high bandwidth fiber optic links, cellular antenna remoting, photonic microwave signal processing, optical switching and phased arrayed radar.