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Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was calculated to be 1.83 × 10−20 cm2 for σ polarization and 5.32 × 10−20 cm2 for π polarization. Similarly, the emission cross-section was determined to be 1.38 × 10−20 cm2 at 980 nm for σ polarization and 2.28 × 10−20 cm2 at 981 nm for π polarization, with a full width at half maximum (FWHM) of 50.3 nm and 89.5 nm, respectively. The fluorescence lifetime of the 5 at.% Yb:CALYGLO crystal at 2F5/2 was measured to be 1.10 ms. Additionally, gain cross-sections were calculated for different β values. In the continuous laser experiment, the crystal demonstrated a laser output of 20.15 W at 1057 nm, with a slope efficiency of 53.3%. These experimental findings indicate that the lattice of Y3+ in the crystal is partially replaced by Lu3+ and Gd3+, resulting in a broader spectrum. Consequently, this crystal shows promising potential as a gain medium for ultrashort pulse laser crystals. [ABSTRACT FROM AUTHOR]

The crystal growth, optical spectra and lifetime of Dy:CaGdAlO 4 crystal were investigated for the first time to our best knowledge. Single Dy:CaGdAlO 4 crystal with size of Φ4 × 40 mm 3 was grown by floating zone method. The peak absorption cross-sections were calculated to be 2.43 × 10 −21 cm 2 and 1.28 × 10 −21 cm 2 at 453 nm for σ and π polarizations. The Judd-Ofelt (JO) parameters of Ω 2 , Ω 4 and Ω 6 were calculated to be 1.8 × 10 −20 cm 2 , 1.0 × 10 −20 cm 2 and 0.5 × 10 −20 cm 2 , respectively. The emission cross-sections were calculated to be 0.51 × 10 −20 cm 2 and 0.55 × 10 −20 cm 2 for σ and π polarizations. The fluorescence decay time is 222 μs. The results indicate that the Dy:CaGdAlO 4 crystal is a potential candidate for yellow laser operation. [ABSTRACT FROM AUTHOR]

We report a fully stabilized self-referenced all-solid-state-laser frequency comb based on a home-built Kerr-lens mode-locked Yb:CaYAlO4 oscillator, which delivers ultrafast pulses with a pulse duration of 54 fs and an average power of 1.5 W. Free running carrier-envelope phase offset frequency (fceo) is observed with a signal to noise ratio of 40 dB at 100 kHz resolution bandwidth, which is phase-locked to a microwave frequency synthesizer with a residual phase jitter of 370 mrad [1 Hz–1 MHz] and with a standard frequency deviation of 0.8 mHz at 1-s gate time within 3-h, corresponding to the relative frequency instability of 2.9 × 10−18 at 1-s average time. It is the lowest phase noise and the highest frequency stability of fceo obtained in a watt-level all-solid-state bulk laser frequency comb to the best of our knowledge. A 13th repetition rate is simultaneously phase-locked to the same microwave standard with a frequency instability level of 10−12 at 1 s average time. Such fully stabilized power scaling Yb: CaYAlO4 laser frequency combs have great potential for applications in broadband dual comb spectroscopy as well as high loss cases such as long-distance time and frequency transfer. [ABSTRACT FROM AUTHOR]

We report on a femtosecond semiconductor saturable absorber mirror (SESAM) mode-locked Yb:LuYAG laser. Pumped by a 976 nm single-mode fiber laser, a self-starting mode-locked Yb:LuYAG laser was demonstrated, delivering a 618-mW output power with 140-fs pulses and a 95.4-MHz repetition rate. The output spectrum is centered at 1053 nm with a spectral width of 10.4 nm. To the best of our knowledge, this is the shortest pulse ever generated from a mode-locked Yb:LuYAG laser. [ABSTRACT FROM AUTHOR]

BGO single crystals doped with Er3+, Tm3+ and Ho3+ rare-earth ions were prepared in the form of rod-type crystal fibers via the micro-pulling down technique to perform an extensive investigation of their visible, near- and mid-infrared luminescence properties and to really decide on their interest as solid-state laser media in the various spectral domains. Revisiting and completing the absorption spectra already available in the literature led to the derivation of more reliable "effective" radiative lifetimes and branching ratios. Registration of the fluorescence decays of the most important emitting levels versus dopant concentrations led for the first time to an unambiguous determination of "intrinsic" emission lifetimes – corresponding to negligible contributions from inter-ionic energy-transfers - and non-radiative multiphonon relaxation rates. Such data also allowed for the determination of the dominant phonon energy which comes into play in the electron-phonon coupling responsible for these multiphonon relaxation processes and for its lattice vibration origin, i.e. a high phonon energy of the order of 820 cm−1 corresponding to the coupling between bending vibrations of (GeO 4)4- tetrahedra and vibrations corresponding to motions of these (GeO 4)4- tetrahedra against the Bi3+ ions for which the rare-earth dopant ions substitute. Using the above data and different methods for the calibration of the registered emission spectra in cross section unit and for the derivation of gain cross section curves finally show that mid-infrared emissions of Er:BGO, Tm:BGO and Ho:BGO around 1.55 μm, 1.9 μm and 2 μm, respectively, occur with comparable gain cross sections as in the most important reference mid-infrared laser materials, although over slightly shifted thus complementary spectral domains. It is shown that potentialities also exist with Tm:BGO in the blue, deep-red and near-infrared spectral domains around 470 nm, 800 nm and 1.45 μm, by pumping the crystals with conventional pump sources and using some suitable co-dopants to avoid detrimental self-terminating processes. • Bi 4 Ge 3 O 12 rod-type crystal fibers doped with Er3+, Tm3+ and Ho3+ ions are successfully grown by using the micro-pulling down technique. • An extensive spectroscopic investigation is performed from the near-UV to the mid-infrared. • Effective radiative and intrinsic emission lifetimes are unambiguously determined for all the important emitting levels. • The origin and the energy of the phonons responsible for the non-radiative multiphonon relaxation of the emitting levels are clearly identified. • Emission and gain cross section spectra show the interest of Er3+, Tm3+ and Ho3+ doped BGO crystals for the high power mid-infrared laser application. [ABSTRACT FROM AUTHOR]

Sm:YAlO 3 (Sm:YAP) crystal with size of Φ28 × 80 mm3 was grown by Czochralski (Cz) method. Polarized absorption spectra and fluorescence spectra of Sm:YAP crystal were discussed for the first time. The peak emission cross-sections were calculated to be 0.80 × 10−21 cm2 (604 nm for a-polarization), 1.82 × 10−21 cm2 (604 nm for b-polarization) and 1.63 × 10−21 cm2 (610 nm for c-polarization), respectively. The Judd-Ofelt (JO) intensity parameters were calculated to be Ω 2 = 2.59 × 10−20 cm2, Ω 4 = 1.78 × 10−20 cm2 and Ω 6 = 2.98 × 10−20 cm2, respectively. The decay lifetime of 4G 5/2 energy level was measured to be 2.51 ms. All above results indicate the Sm:YAP crystal may be a potential candidate of reddish-orange laser pumped directly by the GaN/InGaN laser diode. • Sm:YAlO 3 crystal was grown by Cz method. • Polarized optical spectra of Sm:YAlO 3 crystal were investigated. • The transitions of 4G 5/2 → 6H 7/2 have the highest branching ratio value, which is suitable for reddish-orange laser. [ABSTRACT FROM AUTHOR]

Pr 3+ -doped YAlO 3 (YAP) single crystal was successfully grown by the Czochralski (Cz) method. Polarized absorption and polarized fluorescence spectra were measured at the room temperature. The spectroscopic parameters based on the polarized absorption spectra were calculated by Judd-Ofelt (J-O) theory for the first time. The fluorescence lifetime of 3 P 0 energy level was fitted to be 19.16 μs with the quantum efficiency of 95.8%. Through the analyzing of the spectroscopic properties, Pr:YAP crystal was demonstrated to be a promising candidate for solid state laser operation. [ABSTRACT FROM AUTHOR]

We report on blue-diode-pumped continuous-wave Pr:YAlO 3 (YAP) crystal lasers. Using a b- cut sample, a maximum output power of 181 mW is achieved at ∼747 nm with slope efficiency of 12.7% with respect to the absorbed power. Using a c -cut sample, a dual-wavelength laser at ∼743 and ∼753 nm is obtained with a total maximum output power of 72 mW by using the blue diode pumping, for the first time to our knowledge. These laser emissions are all linearly polarized and M 2 factors of these output laser beams are also measured. YAP is experimentally verified to be one of effective oxide hosts for Pr-doped visible laser operation besides its fluoride counterparts. [ABSTRACT FROM AUTHOR]

In this paper, the Floating zone technique was used to grow high-quality Cr3+:YScO 3 crystals. The absorption cross-sections of the 4A 2 →4T 1 transition and 4A 2 →4T 2 transitions were calculated to be 1.71 × 10−20 cm2 at 488 nm and 0.72 × 10−20 cm2 at 666 nm, respectively. The crystal field strength Dq, Racah parameters B, and C were calculated to be 1502 cm−1, 533 cm−1, and 3362 cm−1, respectively. In the Cr3+:YScO 3 crystal, the effective phonon energy and Huang-Rhys factor S were calculated to be 284 cm−1 and 8.62, respectively. The emission cross-section at 988 nm corresponding to the 4T 2 →4A 2 transition was calculated to be 1.44 × 10−20 cm2 with full width at half maximum (FWHM) of 318 nm. All the results show that Cr3+:YScO 3 crystal has the potential to be a tunable and ultrafast laser crystal. • Cr:YScO 3 crystals were successfully grown by the Floating zone technique(FZ) method. • Broad emission spectrum with full width at half maximum (FWHM) of 318 nm in Cr:YScO 3 crystals was observed. • Spectral properties and crystal field parameters of Cr:YScO 3 crystals were investigated and analysed. [ABSTRACT FROM AUTHOR]

A high-quality Cr:CYA (Cr:CaYAlO 4) single crystal fiber was grown by μ-PD (Micro-Pulling-Down) method. The E//a and E//c polarized excitation spectra of Cr:CYA at room temperature was measured. The crystal field parameters were calculated and the energy level structure of Cr:CYA was analyzed. We also measured the polarization emission spectra and lifetimes at different temperatures and calculated the effective emission cross-section. Based on the above data and Boltzmann law, the thermal distribution between the excited energy levels 2E and 4A 2 at different temperatures was analyzed. The present work may be useful for guiding laser research on Cr:CYA and other Cr3+-doped laser crystals above room temperature. • Cr:CYA single crystal fiber was grown by μ-PD (Micro-Pulling-Down) method. • Excitation spectra and crystal field parameters of Cr:CYA crystals were investigated and analyzed. • The effective emission cross section of Cr:CYA at different temperatures was calculated. [ABSTRACT FROM AUTHOR]

We report on diode-pumped Nd:LuAG crystal and ceramic lasers operating at about 1.83 μm, using a simple and compact plane-concave cavity configuration. For Nd:LuAG crystal laser oscillating at 1828.43 nm, the maximum output power reaches 0.36 W with slope efficiency of about 5.0%. For Nd:LuAG ceramic laser, a maximum output power of 0.145 W is achieved with slope efficiency of about 2.2%, and the lasing wavelength peaks at 1828.76 nm. The 1.83-μm Nd laser sources could be very promising for eye-safe applications because they have stronger water absorption than another kind of eye-safe Nd lasers operating at 1.4 μm. [ABSTRACT FROM AUTHOR]

We report a power scaled laser operation of diode-pumped Nd:LSO lasers at 1.35 μm. With single-end-pumping scheme, maximum output power reaches 0.77 W at 1358.99 nm in free-running mode. By inserting an etalon, wavelength tuning can be realized with tuning range of at least 6.5 nm from 1356.95 nm to 1363.39 nm. Simultaneous dual-wavelength laser at 1331.63 and 1357.43 nm can also be generated with total output power of 0.19 W, for the first time to our knowledge. Further power scaling to 1.03 W of the 1358.99 nm laser is finally achieved by recycling the remaining pump power, which represents the highest output power so far for 1.3 μm silicate lasers. [ABSTRACT FROM AUTHOR]

• The stable CW ML pulsed with pulse duration as short as 1.97 ps was experimentally obtained. • We proved it experimentally that under the increasing saturation parameters , output pulses could be narrowed in the steady state cavity. • We used the generalized Ginzburg-Landau equation for the mode-locked pulse dynamic evolutions. • We showed that the pulse-narrowing mechanism in solid-state cavity at water absorption band. Ultrafast solid-state laser sources operating in the mid-infrared (mid-IR) region are of significant importance in a variety of applications. However, the realization of ultrafast lasers with narrow pulse width at wavelengths between 1.8 and 2 µm has remained a big challenge due to the strong water molecule absorption. Here, we report a stable mode-locking (ML) pulsed lasing at 1967 nm and narrow pulse duration of 1.97 ps in a diode-pumped Tm:CaYAlO 4 (Tm:CYA) crystal laser oscillator. By employing the SESAMs with different modulation depths as mode-lockers, we show that under the increasing saturation parameters, output pulses could be narrowed in the steady state cavity. Furtherly, the generalized Ginzburg-Landau equation is used for the mode-locked pulse dynamic evolutions. It shows that the pulse- regulation mechanism in solid-state cavity at water absorption band is governed by the balance of the laser gain, the modulation depth, and the saturation parameter. To our knowledge, this is the first demonstration of pulse regulation mechanism in the 2 μm water absorption band by a commercial laser diode in a Tm:CYA laser. Our results provide an effective method for pulse regulation of ultra-short mid-IR pulses and even few-cycle pulses with controllable optical spectra in the water absorption band. [ABSTRACT FROM AUTHOR]

A Nd:BGSO crystal with the dimensions of Φ2 × 131 mm3 has been grown successfully by the micro-pulling-down method. The peak absorption cross-section at 808 nm was calculated to 0.98 × 10−20 cm2 with full-width at half-maximum of 17.4 nm. The stimulated emission cross-section was obtained to be 3.15 × 10−20 cm2 at 1063 nm. The fluorescence and radiative lifetimes of 4F 3/2 level were 248 μs and 300 μs respectively. All results indicate that the Nd: BGSO single crystal would be a promising near-IR solid-state laser material. [ABSTRACT FROM AUTHOR]

High quality 7 at%Er:Y 2 O 3 crystal was successfully grown by Fz method. Judd-Ofelt theory was applied to analyze spectroscopic properties at 2.7 μm. The larger value of Ω 2 shows low local environment symmetry exists in Er:Y 2 O 3 crystal, and the large Ω 4 /Ω 6 indicates better spectral quality. The larger absorption cross-section and FWHM are beneficial to efficient absorption of pump source. The fluorescence spectra and lifetimes of Er:Y 2 O 3 crystal were measured and studied at 2.7 μm. The emission cross-sections at 2723 nm was calculated to be 1.41 × 10−20cm2. Compared with other Er3+ doped crystals, the large spectral quality factors Q and low fluorescence lifetime ratio illustrate that Er:Y 2 O 3 crystal has excellent laser properties at 2.7 μm. In addition, the low inversion ratio also indicates great potential of Er:Y 2 O 3 crystal for laser generation at 2.7 μm. • A high quality 7%Er:Y 2 O 3 laser crystal was successfully grown by Fz method. • Judd-ofelt (J-O) parameterization scheme was applied to analyze the spectroscopic properties of 7%Er:Y 2 O 3 laser crystal at 2.7 μm. • The large spectral quality factors Q with low fluorescence lifetime ratio illustrates that Er:Y 2 O 3 crystal has excellent laser properties at 2.7 µm. • The low inversion ratio indicates great potential of Er:Y 2 O 3 crystal for laser generation at 2.7 μm. [ABSTRACT FROM AUTHOR]

Tb3+ doped Y 3 Al 5 O 12 (Tb:YAG) single crystal has been grown by the Czochralski method. Optical spectroscopic characterization of the crystal was performed in order to evaluate the potential for the visible laser application. Based on the Judd–Ofelt theory, the spectroscopic parameters Ω t (t = 2, 3, 6), spontaneous transition probabilities, fluorescence branch ratio and the radiation lifetime of excited state 5D 4 state were calculated. The green emission cross section of 5D 4 →7F 5 transition were calculated to be 1.23 × 10−21 cm2 , The yellow emission cross section of 5D 4 →7F 4 transition were calculated to be 7.08 × 10−23 cm2. The decay time of the 5D 4 level was measured to be 3.12 ms, which is in reasonable agreement with the radiation lifetime of 3.30 ms. All the results indicate the potential of Tb:YAG crystal as a visible laser material. • Tb:YAG crystal was grown by Czochralski method. • Judd-Ofelt theory was used to analyze the spectroscopic properties of Tb:YAG for the first time. • Tb:YAG crystal is a potential laser material for yellow and green laser output. [ABSTRACT FROM AUTHOR]

• The performance of diode-pumped (Nd3+-doped) Ca 0.7 La 0.3 Al 12 O 19 (Nd:CLA) lasers was studied for the first time. • By inserting a Cr4+:YAG absorber, we successfully achieved a passively Q-switched laser. • Comparation between a- and c-cut disordered Nd:CLA lasers were made. A new neodymium-doped (Nd3+-doped) Ca 0.7 La 0.3 Al 12 O 19 (Nd:CLA) disordered crystal was successfully grown by the Czochralski method. The performance of diode-pumped Nd:CLA (a-cut and c-cut) lasers was demonstrated for the first time. For the c-cut crystal continuous-wave (CW) operation, we obtained the highest output power of 2.08 W at the wavelength of 1053.2 nm, and the slope efficiency was 23% versus the incident pump power. By inserting a Cr4+:YAG absorber, we successfully achieved a passively Q-switched laser, and the shortest pulse width was 18.36 ns with a peak power of 364.6 W. Compared with a-cut crystal, c-cut crystal has superior laser characteristics. [ABSTRACT FROM AUTHOR]

LaMgAl 11 O 19 (LMA) crystal with nominal Sm3+ concentrations of 8 at.% was grown by the Czochralski method. Polarized absorption spectra, polarized emission spectra and fluorescence decay curve of Sm:LMA crystal were recorded at room temperature. The absorption cross-sections at 404 nm were calculated to be 2.33 × 10−20 cm2 and 0.86 × 10−20 cm2 for σ and π polarization, respectively. The spontaneous transition rates, branching ratios and the radiative lifetime of the 4G 5/2 multiplet, were calculated. The Judd-Ofelt theory has been applied to evaluate the Ω t (t = 2, 4, 6) intensity parameters. The highest stimulated emission cross-sections for the 4G 5/2 → 6H 7/2 transition around 594 nm were calculated to be 1.67 × 10−21 cm2 for σ polarization and 1.15 × 10−21 cm2 for π polarization, with full width at half maximum (FWHM) of 7.68 nm and 7.27 nm, respectively. The fluorescence lifetime of the 4G 5/2 manifold was 1.84 ms. All the results show that Sm:LMA crystal would be a promising orange-red solid state laser material. • The most intensive absorption line of Sm3+ ion, suitable for 405 nm InGaN laser diode. • The rigidity of Sm:LMA crystal is higher than some host crystals. • The value Ω 2 of Sm:LMA crystal is comparable to Sm:LiYF 4. • The large parameter σ em τ of Sm3+ in LMA is beneficial for the solid state laser. [ABSTRACT FROM AUTHOR]