David S. Funk

Arrays of distributed-Bragg-reflector waveguide lasers at 1536 nm in Yb/Er codoped phosphate glass

We have demonstrated an array of monolithic, single-frequency-distributed-Bragg-reflector (DBR), waveguide lasers operating near 1536 nm wavelengths. The lasers were fabricated by forming waveguides in Yb/Er-codoped phosphate glass by ion exchange. The slope efficiency for each laser as a function of launched pump power is 26% and the thresholds occur at 50 mW of launched pump power. An output power of 80 mW was achieved with 350 mW of coupled pump power. Each laser exhibits stable operation on a single longitudinal mode and all have linewidths less than 500 kHz. A comb of waveguides with varying effective indices allows the selection of wavelength using a single-period grating.

Ion-exchanged waveguide lasers in Er 3+ /Yb 3+ codoped silicate glass

We investigated an Er(3+)/Yb(3+) codoped silicate glass as a host material for waveguide lasers operating near 1.5 microm. Spectroscopic properties of the glass are reported. Waveguide lasers were fabricated by K(+)-ion exchange from a nitrate melt. The waveguides support a single transverse mode at 1.5 microm. An investigation of the laser performance as a function of the Yb:Er ratio was performed, indicating an optimal ratio of approximately 5:1. Slope efficiencies of as great as 6.5% and output powers as high as 19.6 mW at 1.54 microm were realized. The experimental results are compared with a waveguide laser model that is used to extract the Er(3+) upconversion coefficients and the Yb(3+)-Er(3+) cross-relaxation coefficients. The results indicate the possibility of obtaining high-performance waveguide lasers from a durable silicate host glass.

Hybrid glass substrates for waveguide device manufacture

Hybrid glass substrates were prepared by a novel, low-temperature process joining active (Er-Yb codoped) and passive phosphate glass. The resulting hybrid substrates are chemically and physically robust; they can be cut, ground, and polished by conventional, water-based techniques. The entire substrate can be immersed in a molten-salt bath to produce waveguides simultaneously in the active and passive regions. A low reflectance of -34+/-2 dB was measured at the joint interface with 1531.2-nm light by optical low-coherence reflectometry. Further, a hybrid laser waveguide device exhibited a slope efficiency of 33% at 1540 nm when pumped at 975 nm.

High-power waveguide lasers

During the past few years high power lasers which incorporate intracavity optical waveguiding have been demonstratedin a number of different geometric formats. These include rectangular planar waveguide structures, two-dimensional multielement waveguide array lasers and annular waveguide devices, all of which dependcrucially on the operational flexibility of the transverse radiofrequency excitation technique. Here, we review the fundamental issues which underlie the attractions of the use of waveguiding structures in the design and construction of ultracompact, diffusion-cooledlasers which are efficient and operate at high average power levels. In particular, we review the properties oflarge area discharge planar waveguide C02/CO lasers, where multi-kilowatt cw power levels have been demonstrated with excellent beam quality and efficiency. It is shown that similar concepts may also be applied to solid state lasers. In addition, theuse of the multi-element array concept for high power scaling will be examined, and the operating characteristics ofan ultra-compact 64 (4 x 16) element array laser operating at 2kW cw output power will be described.

Erbium/ytterbium-codoped glass waveguide laser producing 170 mW of output power at 1540 nm

This paper describes the fabrication and performance of an ion-exchanged, channel waveguide laser in erbium/ytterbium-codoped phosphate glass, which has produced 170 mW of cw power near 1540 nm.

Active materials for integrated optic applications

The ability to engineer glass properties through the selection and adjustment of chemical composition continues to make glass a leading material in both active and passive applications. The development of optimal glass compositions for integrated optical applications requires a number of considerations that are often at variance with one another. Of critical importance is that the glass offers compatibility with standard ion exchange technologies, allowing fabrication of guided wave structures. In addition, for application as an active material, the resultant structures must be characterized by absence of inclusions and low absorption at the lasing wavelength, putting demands on both the selection and identity of the raw materials used to prepare the glass. We report on the development of an optimized glass composition for integrated optic applications that combines good laser properties with good chemical durability allowing for a wide range of chemical processing steps to be employed without substrate deterioration. In addition, care was taken during the development of this glass to insure that the selected composition was consistent with manufacturing technology for producing high optical quality glass. We present the properties of the resultant glasses, including results of detailed chemical and laser properties, for use in the design and modeling of active waveguides prepared with these glasses.

Low-threshold diode-pumped operation of the holmium upconversion fiber laser

Low threshold operation of the 550 nm holmium laser is reported in a Ho3+:ZBLAN fiber pumped near 650 nm. The 550 nm transition has been pumped by an InGaAlP diode laser producing approximately 30 mW at 643 nm. Over 1.2 mW of green laser output and an optical conversion efficiency of 12% has been obtained. The threshold diode laser pump power was 3.5 mW launched.

Ion-exchanged Er3+/Yb3+ glass waveguide lasers in silicate glasses

Waveguide lasers and amplifiers in glasses codoped with Er3+ and Yb3+ are promising candidates for compact multifunctional devices operating near 1.5 μm.

Arrayed DBR waveguide lasers for the ITU grid

We have successfully demonstrated an array of monolithic, single-frequency DBR waveguide lasers that operate near 1536 nm. Single transverse mode waveguides in the 1500 nn telecommunications band were fabricated in a commercially available phosphate glass that was codoped with 1/spl times/10/sup 20/ Er/sup 3+/ ions/cm/sup 3/ and 4/spl times/10/sup 20/ Yb/sup 3+/ ions/cm/sup 3/. Phosphate glass is a very good host compared to silica for erbium ions since the sensitization efficiency is nearly unity and large doping concentrations are possible before the onset of concentration quenching. We have performed waveguide laser simulations correlated to experimental results that indicate the Yb-Er energy transfer efficiency is greater than 95% in this glass. Waveguides are formed by potassium for sodium thermal ion-exchange. We have also used a field assisted process to form waveguides in codoped phosphate glass. Tests of thermal ion exchanged Fabry-Perot lasers without DBR gratings have shown that slope efficiencies of 28% are possible with thresholds as low as 25 mW of coupled 980 nm pump power, Similar results have been achieved using field assisted ion exchanged waveguides. We have also shown these lasers can be tuned from 1525 to 1595 nm.