F. Fusari

Femtosecond pulse operation of a Tm,Ho-codoped crystalline laser near 2 μm

We demonstrate, for the first time to our knowledge, femtosecond-regime mode locking of a Tm,Ho-codoped crystalline laser operating in the 2 microm spectral region. Transform-limited 570 fs pulses were generated at 2055 nm by a Tm,Ho:KY(WO(4))(2) laser that produced an average output power of 130 mW at a pulse repetition frequency of 118 MHz. Mode locking was achieved using an ion-implanted InGaAsSb quantum-well-based semiconductor saturable absorber mirror.

Femtosecond mode-locked Tm 3+ and Tm 3+ -Ho 3+ doped 2 μm glass lasers

We report on the spectroscopic characterization, continuous-wave and continuous wave mode-locked laser performance of bulk Tm(3+):GPNG fluorogermanate and Tm(3+)-Ho(3+):TZN tellurite glass lasers around 2 μm. A slope efficiency of up to 50% and 190 mW of output power were achieved from the Tm(3+):GPNG laser at 1944 nm during continuous wave operation. The Tm(3+)-Ho(3+):TZN laser produced a 26% slope efficiency with a maximum output power of 74 mW at 2012 nm. The Tm(3+):GPNG produced near-transform-limited pulses of 410 fs duration centered at 1997 nm with up to 84 mW of average output power and repetition frequency of 222 MHz when was passively modelocked using an ion-implanted InGaAsSb-based quantum well SESAM. Using the same SESAM, the Tm(3+)-Ho(3+):TZN laser generated 630-fs pulses with 38 mW of average output power at 2012 nm. Data analysis of pulses at different intracavity pulse energies provided an estimation of n(2) at 2012 nm of 2.9 × 10(-15) cm(2)/W for the Tm(3+)-Ho(3+):TZN.

Passive mode locking of a Tm,Ho:KY(WO4)2 laser around 2 μm

We report the first demonstration, to our knowledge, of passive mode locking in a Tm(3+), Ho(3+)-codoped KY(WO(4))(2) laser operating in the 2000-2060 nm spectral region. An InGaAsSb-based quantum well semiconductor saturable absorber mirror is used for the initiation and stabilization of the ultrashort pulse generation. Pulses as short as 3.3 ps were generated at 2057 nm with average output powers up to 315 mW at a pulse repetition frequency of 132 MHz for 1.15 W of absorbed pump power at 802 nm from a Ti:sapphire laser.

Spectroscopic and lasing performance of Tm3+- doped bulk TZN and TZNG tellurite glasses operating around 1.9 µm

We report spectroscopic and bulk laser performance characteristics for Tm(3+)-doped tellurite glasses when used as gain media operating around 1.9 microm. Two glass hosts studied are TZN and TZNG and their performances have been compared. In each case, well-characterized cw laser performance was obtained and this has been related to detailed spectroscopic measurements of the important lasing parameters of the laser transitions around 1900 nm when pumped at 793 nm. The maximum output power achieved was 124 mW from the TZNG sample with an associated slope efficiency of 28 % with a tuning range of 135 nm. Efficiency and loss analyses yielded a calculated maximum attainable efficiency of 48 % in Tm(3+):TZN compared to 28 % for the TZNG host.

Continuous-wave laser operation of Tm and Ho co-doped NaY(WO 4 ) 2 and NaLu(WO 4 ) 2 crystals

Tetragonal single crystals of NaT(WO(4))(2) (T = Y or Lu) co-doped with Tm(3+) and Ho(3+) ions have been employed for broadly tunable and efficient room-temperature laser operation at around 2 mum. With Ti:sapphire laser pumping at 795 nm, a slope efficiency and a maximum output power as high as 48% and 265 mW, respectively, have been achieved at 2050 nm from a Tm,Ho:NaY(WO(4))(2) crystal. Tuning from 1830 nm to 2080 nm has also been obtained using an intracavity Lyot filter.

Lasing action at around 1.9 μm from an ultrafast laser inscribed Tm-doped glass waveguide

We report optical guiding and laser action at around 1.9 μm in a Tm³⁺-doped fluorogermanate glass waveguide fabricated using ultrafast laser inscription. A monolithic laser cavity was constructed by directly butt coupling dielectric mirrors to each facet of the 6.0 mm long Tm³⁺-doped waveguide. When the waveguide was pumped by a Ti:sapphire laser tuned to 791 nm, laser oscillation was achieved at around 1.91 μm. This waveguide laser exhibited a maximum slope efficiency of 6% and a maximum output power of 32 mW when pumped with 620 mW of incident laser power.

GaInNAs semiconductor disk lasers as pump sources for Tm3+ (,Ho3+ )-doped glass, crystal and fibre lasers

We report the first use of a Semiconductor Disk Laser (SDL) as a pump source for ~2μm-emitting Tm3+ (,Ho3+)-doped dielectric lasers. The ~1213nm GaInNAs/GaAs SDL produces >1W of CW output power, a maximum power transfer net slope efficiency of 18.5%, and a full width half maximum wavelength tuning range of ~24nm. Free-running operation of a Tm3+-doped tellurite glass laser under 1213nm SDL pumping generated up to 60mW output power with 22.4% slope efficiency. Wavelength tunable output is also obtained from 1845 to 2043nm. Improved performance with output powers of ~200mW and a slope efficiency of ~35% are achieved by replacing the Tm3+-doped glass with a Tm3+-doped KYW active medium. Emission of a Tm3+,Ho3+-codoped tellurite glass laser is also reported with maximum output power of ~12mW and a ~7% slope efficiency. Finally, preliminary investigations of 1213nm-pumping of a Tm3+,Ho3+-codoped silica fibre laser lead to 36mW output power with ~19.3% slope efficiency.

Efficient Continuous-Wave, 2-μm Tm,Ho:KY(WO 4 ) 2 Laser

The growth, spectroscopy and lasing performance of a Tm,Ho:KY(WO4)2crystal are reported. An average power up to 390mW is generated at 2058nm with a corresponding slope efficiency of 42% during continuous-wave operation at room temperature.

Passively mode-locked Tm,Ho:KY(WO 4 ) 2 laser around 2µm

Ultrashort-pulse lasers operating around 2 µm spectral region are of great interest for applications in time resolved spectroscopy, nonlinear frequency upconversion, optical communications and photomedicine. Tm³⁺ doped and Tm³⁺,Ho³⁺ co-doped crystalline gain media represent an attractive option for creating of diode-pumped, efficient and broadly tunable lasers around 2 µm which can be further employed for ultrashort pulse generation through the modelocking techniques. In the past, the generation of sub-100 ps pulses was reported from Tm:YAG [1] and Tm,Ho:BaY<inf>2</inf>F<inf>8</inf> [2] lasers using an active mode-locking technique. However, no passively mode-locked Tm-doped and Tm,Ho co-doped bulk lasers have been reported to date. Here we demonstrate, for the first time to our knowledge, a Tm³⁺,Ho³⁺:KY(WO<inf>4</inf>)<inf>2</inf> (Tm,Ho:KYW) laser passively mode-locked by using semiconductor saturable absorber mirror (SESAM).

Spectroscopy and efficient room-temperature laser operation of Tm,Ho:KY(WO 4 ) 2 around 2µm

Solid-state laser sources operating around 2-µm spectral region are subject of considerable interest due to their recognised importance for applications in LIDAR technology and medicine. In recent years Tm³⁺-doped and Tm³⁺, Ho³⁺ co-doped crystalline gain media have become the key gain media choice for diode-pumped and efficient 2-µm laser sources. In particular, it has been shown that Tm³⁺-doped KGd(WO<inf>4</inf>)<inf>2</inf> (Tm:KGdW) [1] and KY(WO<inf>4</inf>)<inf>2</inf> (Tm:KYW) [2] gain media have efficient and broadly tunable operation near 1.9µm under diode-pumping at around 805nm. Here we report on the growth of a novel Tm,Ho:KYW laser crystal, together with its spectroscopic properties and lasing characteristics obtained using cw Ti:sapphire laser pumping at room temperature.