ultrafast laser

1. Novel materials for laser written optical waveguide amplifiersDenise M. Krol, University of California-Davis, DMR 0801786 Outcome: Scientists at UC Davis, in collaboration with Missouri S&T, have found that zinc polyphosphate glasses have superior properties for direct femtosecond (fs) laser writing of photonic devices. Impact:These glasses enable the fabrication of active 3-D photonic devices, such as compact high gain waveguide lasers and amplifiers that operate in the telecommunications window. Explanation: Tightly focused ultrafast laser pulses can be used to induce permanent changes in transparent materials such as glass. By moving the sample with respect to the laser focus, patterns can be “written” at will in the glass with high 3-D spatial ultrafast laser selectivity. This technology has great potential for the fabrication of optical components for all-optical circuits. However, many commercially available glasses do not exhibit the desired response to fs laser machining. Prof. Krol and her group at UC Davis, in collaboration with the group of Prof. R. Brow at Missouri S&T, have discovered that a specific zinc polyphosphate glass composition has shown changes in glass structure that make it ideal for use with the fs-laser writing technology. The team has used this glass to build a waveguide amplifier operating in the telecom window. glass

2. Fs-laser written waveguides in zinc phosphate glass Denise M. Krol, University of California-Davis, DMR 0801786 Femtosecond laser micromachining of waveguides depends on the bulk glass substrate used for fabrication. Phosphate glasses are important substrates because they can incorporate high concentrations of rare-earth ions, making them an ideal host material for fabricating compact high gain waveguide lasers and amplifiers that operate in the telecommunications window. However, commercially available phosphate glass is not necessarily the optimal material for use with fs-laser waveguide writing. Ph. D. student Luke Fletcher has discovered that zinc polyphosphate glasses with an O/P ratio of 3.25 exhibit laser-induced changes in glass structure that are ideal for waveguide fabrication. In rare-earth doped glass with composition 0.7Er2O3-1.3Yb2O3-56.0ZnO-42.0P2O5 low loss single-mode waveguides with an internal gain of 1 dB/cm at 1534 nm have been fabricated. White light microscope images (a) and 660 nm laser near field guiding intensity profiles (b) for fs laser written waveguides in (1) 60ZnO-40P2O5, (2) 0.7Er2O3- 1.3Yb2O3 -58.8ZnO-39.2P2O5 (3) 0.7Er2O3-1.3Yb2O3-56.0ZnO -42.0P2O5 glass.

3. Outreach and Education Activities Denise M. Krol, University of California-Davis, DMR 0801786 In Fall 2010 Professor Krol visited the University of Pardubice in the Czech Republic to teach a group of faculty and students (shown in picture below) about fs laser modification of glass in a one-week intensive course schedule of twelve 90 minute lectures. With support from this award graduate students Luke Fletcher (left) and Jon Witcher (right) both obtained their PhD degrees in 2011. Jon’s work focused on the “Dynamics of fs-Laser Modification inside Fused Silica” while Luke’s thesis was titled “Photonic Device Fabrication Inside Phosphate Glasses Using Femtosecond Laser Waveguide Writing Techniques”