Venkata Adiseshaiah Bhagavatula

Dispersion-shifted segmented-core single-mode fibers

Dispersion-shifted segmented-core single-mode designs with low sensitivity of the zero-dispersion wavelength to the cutoff-wavelength variation have been identified. Dispersion, spot size, and bending-loss results on such dispersion-shifted fibers with the highest cutoff wavelength reported to date are presented.

Novel fibers for dispersion-managed high-bit-rate systems

Summary form only given. Novel dispersion-managed fibers that minimize four-wave mixing (FWM) and other nonlinear effects with built-in dispersion compensation, large effective areas, and low dispersion slopes have been developed. These fibers are also expected to be flexible enough to allow upgrades in both wavelength-division multiplexing and time-division multiplexing approaches. Propagation and FWM efficiency models have been used to optimize the designs and evaluate the system advantages of these fibers.

Progress in high-power fiber lasers

We review current work on fiber laser systems at Corning. In particular, we describe design and performance of all-glass double-clad laser fibers, broad-area laser pumps, and pump coupling optics. We discuss our approaches using single-polarization fiber and low-nonlinearity photonic band gap fiber as technologies for developing the next generation of high-power fiber lasers.

High optical power testing of physical contact connectors at 1550 nm

We have investigated the high optical power handling capability of standard SC physical contact (PC) and angled physical contact (APC) connectors using SMF-28/sup TM/ fiber at powers of 1 and 3 W at 1550 nm. We will report results of short-term exposure tests of mated connector pairs prepared with various endface surface conditions.

Packaging and performance of high power semiconductor lasers of high heat flux up to 2000 W/cm/sup 2/

High power broad area semiconductor lasers have found increasing applications. Compared to low power narrow-stripe semiconductor lasers, packaging including the assembly design, process and thermal management, has much higher impact on the output power and reliability of high power broad area lasers which generate more heat and have high heat flux. In this paper, we first introduce the package structures and assembling process of high power broad area lasers. We report two types of high power broad area laser assemblies. One is a microchannel liquid cooled assembly and the other is a conduction cooled CT-mount assembly. The performances including output power, thermal behavior and far fields are presented. The measurement results showed that excellent thermal management through package structure design as well as quality die attachment is the key in not only improving output power, but also significantly improving beam divergence and far field distribution. The reliability of indium solder bonded and AuSn solder bonded CT mount assemblies were evaluated. The results showed that the die attach solder can significant impact the reliability of high power broad area lasers and that indium solder is not suitable for high power laser applications due to electromigration at high current densities and high temperatures.

Reverse-proton-exchanged waveguide frequency doublers for green light generation

We describe reverse-proton exchanged (RPE) waveguides in MgO-doped lithium niobate capable of stable secondharmonic generation (SHG) of over 100 mW of CW green light with conversion efficiency exceeding 200%/Wcm2. Substantially higher green power would require careful thermal management to limit the phase mismatch due to heating produced by optical absorption. RPE waveguides show ability to support high-power generation of green light superior to anneal-proton exchanged (APE) waveguides containing a higher-index layer. We also demonstrate devices with multipeak spectral response for speckle-reduced green laser by using phase-modulated, quasi-periodic ferroelectric domain structure.

UV photosensitivity in conventionally melted germano-silicate glasses

The UV-photosensitivity effect in germania-doped optical waveguides has become an important area of research because of the ease and utility of making Bragg gratings. In this study we report on the finding of a large UV-induced refractive index change in a conventionally melted an alkali-alumino-boro-germano- silicate composition that has been loaded with molecular hydrogen. The exposure was done with either CW 244-nm light, or a pulsed KrF excimer laser at 248-nm. A modulated refractive index of the order of 2-3 X 10-4 has been measured.

Planar lens devices by CVD process

A novel technique for splitting optical signals using planar refractive lenses is proposed. The concept of the planar lens in dielectric films for the fabrication of thin film 1/spl times/N couplers is described. The advantages of this approach for fabricational tolerances, pigtailing, and packaging are described, and the performance of the devices, made by the CVD process is analysed. Experimental results on 1/spl times/2 and 1/spl times/8 devices using this approach are presented. Very good output spot characteristics and insertion loss values have been obtained, and a number of functional, pigtailing, and packaging advantages have been identified.<<ETX>>

Conversion efficiency and green power of compact reverse-proton-exchanged MgO:LiNbO 3 waveguides

A sub-cm-long reverse-proton-exchanged waveguide with record normalized efficiency showed 44.2% peak internal continuous-wave single-pass conversion, 196-mW peak green, and overall conversion peaking at 30%, being above 25% for green outputs above 80 mW.

Design of athermalized proximity coupled (APC) synthetic green laser opto-electronic package for microprojector displays: Numerical modeling and experiments

Micro-projector based displays are proposed for information display for a number of consumer devices. These displays would provide larger images than existing fixed Liquid crystal displays. The two major components of micro-projector technology are the Light source and the Imaging technology. Three primary colors, red, blue and green are required to create full color images. The light sources in the projection technology would be semiconductor devices that emit these colors. These devices could be either light emitting diodes (LEDs) or lasers. To enable the laser based projection technology, red and blue lasers are commerically available. Native semiconductor green lasers are still in development. As an alternative, synthetic green light can be produced by passing 1060nm infra-red light emitted from a GaAs based semiconductor laser diode (LD) through second harmonic generation (SHG) crystal, thereby emitting the green light at 530 nm. The current research work proposes bringing the SHG structure in close proximity to the LD, thereby eliminating the use of any optics in between. The proximity coupling approach promises to reduce the number of package components and process cost significantly. This paper presents the mechanical package design, coefficient of thermal expansion based displacement estimates, thermal analysis wherein the thermal impedance is predicted and measured, thermo-mechanical analysis wherein the thermo-mechanical stresses and strains are predicted. Shock modeling has been done to understand the displacements of the waveguides during the shock event. Optical modeling is performed to estimate the coupling efficiency change as a function of lateral and longitudinal offset between the LD and SHG waveguides. Finally, an assembled package that generated green light using this design is presented.