The development of the first Yb<sup>3+</sup> doped microchip and waveguide laser in germanate glass (GPGN) is reported with a composition of 54GeO<sub>2</sub>-31PbO-4Ga<sub>2</sub>O<sub>3</sub>-9Na<sub>2</sub>CO<sub>3</sub>-1.5Yb<sub>2</sub>O<sub>3</sub> (Yb<sup>3+</sup>: GPGN). Up to 51mW at 650mW of input power is obtained from a L=4.5mm long cavity microchip laser operating at 1052nm with slope efficiency of ~30% and laser threshold of ~230mW. Single track (type 1) waveguides are inscribed 150μm beneath the surface of the sample in the femtosecond laser cumulative heating regime. Pulse energies range from15nJ to 75nJ producing guiding structures ranging from d= 12μm to 60μm. Waveguide laser operation is achieved for a 24μm diameter waveguide with up to ~20mW output power generated at 1.07μm for 650mW of 976 nm pump power.
We report on the latest results towards a compact ultra-high repetition rate Yb-doped fluorozirconate laser, based on a simple and robust extended cavity design. Preliminary results show a laser operates with a pulse width of 2.5 ps and a repetition rate of 276 MHz at λ = 1018 nm. By controlling the dispersion and intracavity loss it should be possible to decrease the pulse width and increase the repetition rate to multi-GHz range.
High beam quality visible laser emission can be directly generated using optically pumped rare-earth (RE) ion doped praseodymium (Pr3+) in a suitable low phonon energy host. Trivalent Pr3+ can generate laser emission in the red, orange, green and blue spectral domains . Direct generation in a RE ion has the advantage of energy storage and broad gain-bandwidths thus allowing tunable, Q-switched, and mode-locked laser operation . Previously we have reported waveguide-based ZBLAN chip lasers in the near IR to mid-IR spectral domain. These chip lasers are based on the ultra-fast laser inscription (ULI) of depressed cladding waveguides into bulk RE ion doped ZBLAN chips.
We report here visible continuous wave laser emission at 636 nm from a praseodymium doped fluorozirconate glass guided-wave chip laser. This ultra-fast laser inscribed gain chip is demonstrated to be a compact and integrated laser module. The laser module, pumped by two polarisation-coupled 442 nm single-mode GaN laser diodes, generates >8 mW lasing output with a beam quality of M2xy~ 1.15 and 1.1 (±0.1). To the best of our knowledge, this is the first visible laser emission from a glass-based waveguide chip laser.
Improved laser performance may also realize laser operation of the lower gain 527 nm green transition, thus allowing the chip laser to simultaneously emit blue (un-depleted pump), green and red laser emission from the same waveguide.
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2. M. Gaponenko, et al., Opt Lett 39, 6939-6941 (2014).
Defects in optical fibers can cause severe damage, and thus must be found and repaired/replaced early. Such defects in fibers and their coatings can be detected using an angle-resolved interrogator that exploits the contribution of different ray groups. This approach can also estimate the radial position of defects within the fiber. A demonstration is performed with a femtosecond-laser-induced internal defect inside the cladding.
A new type of photodetector with an optical sensor is presented, which enables it to operate even in the presence of strong electro-magnetic interference. The optical sensor head consists of cascaded Fabry-Perot etalons coated with a new type of photo-thermal coating comprising of hydrogel-embedded copper-oxide micro-particles. For white-light irradiation, the photodetector exhibits a power sensitivity of 760 pm/mW, a detection limit of 16.4 μW, and an optical damage threshold of ∼100 mW or ∼800 mW/cm<sup>2</sup>. The response and recovery times are 3.0 s (∼90% of change within 100 ms) and 16.0 s.
Passively mode-locked sub 200 fs pulses are generated from Er-Yb co-doped ZBLAN waveguide laser using a semiconductor saturable absorber mirror repetition rates of up to 533 MHz. At 156 MHz and 1556 nm central wavelength, the chip laser operates with a broad 25 nm bandwidth. The waveguides were written in the Er-Yb co-doped ZBLAN glass by using ultrafast laser inscription.