K. J. Malone

Integrated-Optic Laser Fabricated by Field-Assisted Ion Exchange in Neodymium Doped Soda-Lime-Silicate Glass

A continuous-wave integrated-optic channel waveguide laser operating at 1.057 microm has been fabricated in neodymium-doped soda-lime-silicate laser glass. The device was end-fire pumped with the 0.528-microm line of an argon-ion laser. Threshold for laser action occurs for an absorbed pump power of 31 mW. The slope efficiency for the integrated-optic laser is estimated to be 0.5%. Field-assisted ion exchange in a eutectic melt of CaNO(3) and KNO(3) was used to form the waveguide.

Y-branch waveguide glass laser and amplifier

A Y-branch channel waveguide laser operating near 1057 nm was fabricated by electric-field-assisted ion exchange in Nd-doped silicate glass. The overall length was 24 mm. Optical pumping was performed with a cw Ti:sapphire laser. Mirrors were bonded to the polished waveguide facets. The slope efficiency was 5.1% when a 4%-transmitting output coupler was used. Threshold was reached at 26-mW absorbed pump power. The device exhibited a single-pass small-signal gain of 0.034 dB/mW when operated as an amplifier. The 3-dB splitting loss of the Y-branch structure was overcome when the absorbed pump power was approximately 85 mW.

Nd:LiTaO 3 waveguide laser

Waveguide lasers operating near 1092 and 1076 nm were fabricated in Z-cut Nd-Ti codiffused LiTaO(3). The Nd diffusion was at 14000 degrees C for 120 h. Samples from two wafers were examined. The Nd film starting thickness was 7 nm in wafer 1 and 15 nm in wafer 2. Ti stripes, 8-15 microm wide, were diffused at 1500 degrees C for 4 h for wafer 1 (130-nm stripe thickness) and 2 h forwafer 2 (100-nm stripe thickness). Pumping was at 750 nm. Threshold occurred at 330 mW of absorbedpump power for the best waveguides from wafer 1 and100 mW for the best waveguides from wafer 2. The slope efficiency of the latter was 0.07%.

Passively Q-switched Nd-doped waveguide laser.

A passively Q-switched waveguide laser operating at 1.054 μm has been demonstrated in a Nd-doped phosphate glass. The channel waveguide was fabricated by K-ion exchange from a nitrate melt. Passively Q-switched pulses were achieved by placement of an acetate sheet containing an organic saturable-absorbing dye within the laser cavity. The resulting pulse train consisted of pulses with a FWHM of ~25 ns and peak powers of 3.04 W. With an 80% transmitting output coupler, cw operation of the laser provided 5.2 mW of output power at 1.054 μm for 229 mW of absorbed 794-nm pump power.

Extended-cavity operation of rare-earth-doped glass waveguide lasers

Channel waveguides fabricated in Nd-doped glass were used as gain elements for extended-cavity lasers. End-fire pumping was performed with a Ti:sapphire laser operating at 807 nm. The 4-nm FWHM output spectrum was centered near 1057 nm. Slope efficiencies were typically 4-11%, with thresholds near 20 mW. Active mode locking and Q switching were separately performed; mode-locked pulse widths were roughly 80 ps FWHM. Q-switched peak power was 1.2 W. The cw output narrowed to 7 GHz and tuned over a range of 24 nm when a grating provided feedback; single-frequency operation resulted when a high-reflectivity étalon was added.

Linewidth narrowing in an imbalanced Y-branch waveguide laser.

A Y-branch channel waveguide laser whose branch segments were mismatched in length by 2.4% was fabricated by electric-field-assisted ion exchange in Nd-doped, mixed alkali–silicate glass. The laser output wavelength was centered at 1057.3 nm, and the linewidth was 0.4 nm FWHM. Our similarly fabricated single-channel Fabry–Perot lasers and balanced Y-branch lasers display linewidths of 3–4 nm. Pumping was performed with a cw Ti:sapphire laser operating at 785 nm. The imbalanced Y-branch laser reached threshold with an absorbed pump power of 48 mW when a 2% transmitting output coupler was used. The slope efficiency was 2%. An extended cavity was used to imbalance the arms in a second laser by a ratio of 2.8:1. This device displayed a linewidth of approximately 3.7 GHz FWHM. The linewidth narrowing of these coupled-cavity lasers is analogous to that seen in a Michelson laser.

Glasses for waveguide lasers

Waveguide lasers formed by ion exchange in rare-earth-doped glasses have emerged as an attractive new technology on the threshold of commercial insertion. These devices can be used as both laser oscillators and optical amplifiers. In this article, we review ion exchange and glass composition. We then discuss the performance of ion-exchanged waveguide lasers made in silicate and phosphate glasses.

Integrated optical devices in rare-earth-doped glass

Integrated-optical devices in rare-earth-doped glasses have emerged as an attractive new technology on the threshold of wide-scale manufacturing and commercial insertion. These devices can be used both as laser oscillators and optical amplifiers. They have been formed by a number of fabrication methods including ion exchange and thin-film deposition. Active integrated-optical devices are expected to be important elements in future optical fiber networks. Rare-earth-doped optical fiber devices provide nearly perfect amplification of signals in optical fibers. The performance of these rare-earth-doped optical fibers is so promising that researchers started investigating whether similar performance could be achieved in planar waveguides. The combination of passive integrated-optical components and rare-earth ions has produced many devices with impressive performance.