67-fs pulse generation from a mode-locked Tm,Ho:CLNGG laser at 2083 nm

Tunable and mode-locked Tm,Ho:GdScO3 laser

A novel, to the best of our knowledge, Tm,Ho:GdScO3 crystal grown using the Czochralski method was investigated for its polarized spectroscopic properties and laser performance in both tunable continuous-wave (CW) and mode-locked regimes. The crystal's multisite structure (Gd3+/Sc3+ site) and Tm3+/Ho3+ dopants contributed to spectral broadening, enabling a tunable laser operation from 1914 to 2125 nm (with a broad range of 215 nm). Additionally, a pulse duration of 72 fs was achieved for E || b polarization. These results demonstrate the potential of the Tm,Ho:GdScO3 perovskite crystal as a promising gain material for ultrafast lasers operating around 2 µm.

Femtosecond pulse generation from a SESAM mode-locked Tm,Ho:SrF2 laser at 2.08 µm

We report on a passively mode-locked Tm,Ho:SrF2 laser employing a SESAM as saturable absorber (SA), delivering nearly Fourier-transform-limited 246 fs pulses at 2084nm without any additional intra- or extra-cavity dispersion compensation elements. This represents, to the best of our knowledge, the shortest pulses generated from the mode-locked fluoride bulk lasers in the 2-µm spectral range. Such compact femtosecond laser can be a potential seed source for large-sized fluoride bulk amplifier systems with exact gain match, enabling the generation of ultrashort intense pulses around 2 µm.

Sub-60-fs mode-locked Tm,Ho:CaYLuAlO4 laser at 2.05 µm

Tm,Ho:CaYLuAlO4 (Tm,Ho:CALYLO) crystal has wide emission spectra both for π-polarization and σ-polarization, showing significant potential for the generation of ultrashort pulses. Here, a widely tunable and passively mode-locked laser operation based on Tm,Ho:CALYLO crystal under two polarizations was demonstrated for what we believe to be the first time ever. For π-polarization, a maximum output power of 1.52 W and a tuning range of 255.3 nm were achieved in the continuous wave (CW) regime. In the mode-locked regime, a pulse duration of 68 fs and an average output power of 228 mW were achieved upon GaSb-based semiconductor saturable absorber mirror (SESAM). As for σ-polarization, a broader tuning range of 267.1 nm was realized, leading to the shorter pulse duration of 58 fs at 79.7 MHz repetition rate.

Spectroscopy and efficient laser performances of a Tm,Ho:CaY0.9Lu0.1AlO4 crystal

We report on the spectral properties and laser performances of a novel, to the best of our knowledge, Tm,Ho:CaY0.9Lu0.1AlO4 (Tm,Ho:CYLA) crystal. The polarized absorption spectra, luminescence spectra, and fluorescence lifetime are systematically investigated, presenting a broad and smooth luminescence band. Furthermore, a maximum continuous wave (CW) laser output power of 0.51 W at 2092 nm is obtained under an absorbed pump power of 2.89 W, corresponding to a slope efficiency of 20.4%. The beam quality factors (M2) are measured to be 1.04 in both the x and y axes. A tuning range of 123.4 nm, from 2017.8 nm to 2141.2 nm, is achieved in the CW regime by using a birefringent filter (BF). A stable passively Q switched Tm,Ho:CYLA laser employing Cr2+:ZnSe as a saturable absorber (SA) is realized for the first time, delivering the shortest pulse width of 560 ns with a transmittance of 1%. The results indicate that the Tm,Ho:CYLA crystal is an excellent laser medium for generating high-efficiency laser at ∼2 µm and has a potential in ultrafast laser generation.

Spectroscopy and 2.8 µm laser operation of disordered Er:CLNGG crystals

We report on the first, to the best of our knowledge, laser operation on the ⁴I_11/2 → ⁴I_13/2 transition of erbium-doped disordered calcium lithium niobium gallium garnet (CLNGG) crystals with broadband mid-infrared emission properties. A 41.4 at.% Er:CLNGG continuous-wave laser generated 292 mW at 2.80 µm with 23.3% slope efficiency and a laser threshold of 209 mW. Er³⁺ ions in CLNGG feature inhomogeneously broadened spectral bands (σ_SE = 1.79 × 10^-21 cm² at 2.79 µm; emission bandwidth, 27.5 nm), a large luminescence branching ratio for the ⁴I_11/2 → ⁴I_13/2 transition of 17.9%, and a favorable ratio of the ⁴I_11/2 and ⁴I_13/2 lifetimes, exhibiting values of 0.34 ms and 1.17 ms (for 41.4 at.% Er³⁺), respectively.

44-fs pulse generation at 2.05 µm from a SESAM mode-locked Tm:GdScO3 laser

Pulses as short as 44 fs (6 optical cycles) with a spectral width of 120 nm are generated from a mode-locked solid-state laser near 2 µm employing an orthorhombic Tm:GdScO₃ perovskite crystal. The average power amounts to 188 mW at a repetition rate of ∼77.6 MHz. The strong inhomogeneous line broadening in GdScO₃ suggests optimum conditions for few-optical-cycle pulse generation of rare-earth ion doped GdScO₃ bulk lasers.

Diode-pumped Tm3+,Ho3+ co-doped GAGG mode-locking laser near the 2.1μm wavelength region

In this paper, a laser diode (LD) pumped passive mode-locking Tm,Ho:GAGG laser based on a semiconductor saturable absorber mirror (SESAM) is reported. By adjusting the group delay dispersions inside the laser cavity and transmissions of the output couplers (OCs), a shortest pulse duration of 10.84 ps at 2089.9 nm is achieved, the average output power is 33.17 mW and the laser runs at a 83.01 MHz repetition rate. A maximum average output power of 66.43 mW is also obtained at 2089.9 nm with a pulse duration of 16.56 ps by using an OC of 3%. To the best of our knowledge, this is the first report on the mode-locking Tm,Ho:GAGG laser.

Polarized spectroscopy and SESAM mode-locking of Tm,Ho:CALGO

A Tm,Ho:CALGO laser passively mode-locked by a GaSb-based SESAM generated pulses as short as 52 fs at a central wavelength of 2015 nm with a broad spectral bandwidth of 82 nm (full width at half maximum) owing to the combined gain profiles of both dopants for σ-polarized light. The average output power reached 376 mW at a repetition rate of 85.65 MHz. In the continuous-wave regime, the laser was power scaled up to 1.01 W at 2080.6 nm with a slope efficiency of 32.0%, a laser threshold of 155 mW and π-polarized emission. Polarized spectroscopic properties of Ho³⁺ ions in singly doped and codoped CALGO crystals were revisited to explain the observed laser performance.

SWCNT-SA mode-locked Tm,Ho:LCLNGG laser

Sub-100 fs pulse generation from a passively mode-locked Tm,Ho-codoped cubic multicomponent disordered garnet laser at ∼2 µm is demonstrated. A single-walled carbon nanotube saturable absorber is implemented to initiate and stabilize the soliton mode-locking. The Tm,Ho:LCLNGG (lanthanum calcium lithium niobium gallium garnet) laser generated pulses as short as 63 fs at a central wavelength of 2072.7 nm with an average output power of 63 mW at a pulse repetition rate of ∼102.5 MHz. Higher average output power of 121 mW was obtained at the expense of longer pulse duration (96 fs) at 2067.6 nm using higher output coupling. To the best of our knowledge, this is the first report on mode-locked operation of the Tm,Ho:LCLNGG crystal.

Sub-50 fs pulse generation from a SESAM mode-locked Tm,Ho-codoped calcium aluminate laser

We report on sub-50 fs pulse generation from a passively mode-locked (ML) Tm,Ho-codoped crystalline laser operating in a 2 µm spectral region. A ${\rm Tm},{\rm Ho}{:}{\rm Ca}({\rm Gd},{\rm Lu}){{\rm AlO}_4}$ laser delivers pulses as short as 46 fs at 2033 nm with an average power of 121 mW at a pulse repetition rate of ${\sim}{78}\;{\rm MHz}$ employing a semiconductor saturable absorber mirror as a saturable absorber. To the best of our knowledge, this result represents the shortest pulses ever generated from a Tm- and/or Ho-based solid-state laser. Polarization switching in the anisotropic gain material is observed in the ML regime without any polarization selection elements which is essential for the shortest pulses.

Tm3+ and Ho3+ colasing in in-band pumped waveguides fabricated by femtosecond laser writing

We report on the first, to the best of our knowledge, in-band pumped Tm³⁺,Ho³⁺ codoped waveguide (WG) laser. A depressed-index surface channel WG (type III) with a 50 µm half-ring cladding is fabricated in a 5 at. % Tm³⁺, 0.5 at. % Ho³⁺:KLu(WO₄)₂ crystal by femtosecond pulse direct laser writing. Under in-band pumping by a 1679 nm Er Raman fiber laser, Tm³⁺ and Ho³⁺ colasing is observed in the WG and explained by bidirectional energy transfer. The maximum total output power at ∼1942nm(Tm³⁺) and 2059 nm (Ho³⁺) is 448 mW with a slope efficiencyM of 40.6%, which is a record high for this type of WG lasers. The maximum output power of the Ho laser reaches 144 mW.

Watt-level passively mode-locked Tm:YLF laser at 1.83 µm

Passive, continuous-wave mode-locked (CWML) operation of a 1.83 µm Tm:YLF laser is experimentally demonstrated for the first time, to the best of our knowledge. Two specially selected output couplers are used to realize this operation. Stability of the CWML laser is obtained with a commercial semiconductor saturable absorber mirror. The maximum average output power is 1.04 W with a pulse duration of 107 ps and repetition rate of 54.1 MHz. Further, a 0.1 mm fused-quartz Fabry-Perot etalon is used to tune the central wavelength of the stable CWML laser at 1827.2 nm, 1829.5 nm, 1831.9 nm, and 1833.5 nm.

Focus issue introduction: advanced solid-state lasers

This joint issue of Optics Express and Optical Materials Express features 28 state-of-the-art articles written by authors who participated in the international "Advanced Solid State Lasers" conference, held in Boston November 4-8, 2018. This review provides a summary of these articles that cover the spectrum of solid state lasers from materials research to sources and from design innovation to applications.