CaGdAlO4 Laser Research Articles

In-band pumped Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser

We report on a Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser with in-band pumping of the Tm ions by a spatially single-mode 1678 nm Raman fiber laser. The structurally disordered CaGdAlO4 host crystal is also codoped also with the passive Lu ion for additional inhomogeneous line broadening. The Tm,Ho,Lu:CaGdAlO4 laser generates soliton pulses as short as 79 fs at a central wavelength of 2073.6 nm via soft-aperture Kerr-lens mode-locking. The corresponding average output power amounts to 91 mW at a pulse repetition rate of ∼86 MHz. The average output power can be scaled to 842 mW at the expense of slightly longer pulses of 155 fs at 2045.9 nm, which corresponds to a peak power of ∼58 kW. To the best of our knowledge, this represents the first demonstration of an in-band pumped Kerr-lens mode-locked Tm,Ho solid-state laser at ∼2 µm.

Continuous-Wave and Mode-Locked Operation of an In-Band Pumped Tm,Ho,Lu:CaGdAlO4 Laser

We investigate in-band pumping of a Tm,Ho,Lu:CaGdAlO4 laser using a Raman-shifted Er-fiber laser (1678 nm), in the continuous-wave (CW) and mode-locked (ML) regimes. A maximum output power of 524 mW is obtained in the CW regime with a 5% output coupler at an absorbed pump power of 2.04 W, corresponding to a slope efficiency of 27.9%. A maximum CW wavelength tuning range of 160 nm at the zero level, from 1984 to 2144 nm, is obtained with a 0.2% output coupler. In the ML regime, pumping with 5.5 W (unpolarized), the average output power (0.2% output coupler) reaches 148 mW at a repetition rate of ~96 MHz. The output spectrum is centered at 2071.5 nm with a FWHM of 21.5 nm (σ-polarization). The pulse duration amounts to 218 fs (time-bandwidth product equal to 0.327).

Passively Q-Switched Yb:CALGO Laser Based on Mo:BiVO4 Absorber.

A stable, passively Q-switched Yb:CaGdAlO4 laser based on Mo:BiVO4 saturable absorber was demonstrated. Close observations of the structure and morphology of the nanoparticles by using transmission electron microscope, Raman spectrum and linear absorption were measured. The nonlinear transmission of Mo:BiVO4 was characterized by a 30 ps laser with a central wavelength of 1064 nm and a repetition rate of 10 Hz. The experimental maximum output power of the pulsed laser was 510 mW with a repetition rate of 87 kHz and pulse width of 3.18 μs, corresponding to a peak power of 1.84 W and a single pulse energy of 5.8 μJ. The experimental results indicate that Mo:BiVO4-SA is a great candidate for passively Q-switched lasers in the near infrared region.

Few-optical-cycle pulse generation based on a non-linear fiber compressor pumped by a low-energy Yb:CALGO ultrafast laser.

Pulse compression in a short, normal dispersion photonic-crystal fiber is investigated with a Yb:CaGdAlO4 laser pumped by a low-power fiber-coupled single-mode diode that delivers 70-fs pulses at 1050 nm central wavelength, with 45-mW average power at 60 MHz repetition rate. A simple and power-efficient compressor based on a ∼15-cm long, low-cost commercial nonlinear fiber, with normal dispersion at the laser wavelength, produces pulses as short as 14.9 fs, corresponding to ∼4.25 optical cycles, with 29 mW average power after a prism-pair compressor in double pass configuration. Pulse quality was investigated with frequency resolved optical gating (FROG) analysis. Furthermore, a comparative analysis of noise properties of the oscillator, pump laser and compressed pulses has been performed.

93 fs pulses at watt-level powers from a diode pumped Yb:CaGdAlO4 laser

We investigated the performance of diode pumped mode-locked Yb:CGA laser operating in the net normal or net anomalous dispersion region. With 26 W pump power, stable femtosecond laser pulses with average power of 4.5 W are obtained, yielding a pump power slope efficiency of 17%. Operating at 80.5 MHz repetition rate, the laser delivers as short as 93 fs pulse duration with average output power of 4.5 W, corresponding to a pulse energy of 56 nJ and a peak power of 0.59 MW. The oscillator exhibits a passive rms power stability of ~0.38% rms over 5 h in high beam quality.

Dual-wavelength vortex beam with high stability in a diode-pumped Yb:CaGdAlO4 laser

We present a stable dual-wavelength vortex beam carrying orbital angular momentum (OAM) with two spectral peaks separated by a few terahertz in a diode-pumped Yb:CaGdAlO4 (CALGO) laser. The dual-wavelength spectrum is controlled by the pump power and off-axis loss in a laser resonator, arising from the broad emission bandwidth of Yb:CALGO. The OAM beam is obtained by a pair of cylindrical lenses serving as a convertor for high-order Hermite–Gaussian modes. The stability is verified by the fact that a OAM beam with two spectral peaks at 1046.1 nm and 1057.2 nm (3.01 THz interval) can steadily operate for more than 3 h. It has great potential for scaling the application of OAM beams in terahertz spectroscopy, high-resolution interferometry, and so on.

High-power, widely tunable Tm:CaGdAlO4 laser resonantly pumped by a Raman fiber laser at ∼1.7 μm

High-power, widely tunable Tm:CaGdAlO4 laser resonantly pumped by a Raman fiber laser at ∼1.7 μm

Microchip Yb:CaLnAlO4 lasers with up to 91% slope efficiency.

Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO4(Ln=Gd,Y)) crystals in plano-plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978nm by an InGaAs laser diode, a 3.4mm long 8at.% Yb:CaGdAlO4 laser generated 7.79W at 1057-1065nm with a slope efficiency of η=84% (with respect to the absorbed pump power). An even higher η=91% was achieved with a 2.5mm long 3at.% Yb:CaYAlO4 laser, from which 5.06W were extracted at 1048-1056nm. Both lasers produced linearly polarized output (σ-polarization) with an almost circular diffraction-limited beam (Mx,y2<1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004-0.007 cm-1. In addition, their spectroscopic properties were revisited.

A diode pumped passively mode-locked Nd:CaGdAlO4 laser

A diode pumped passively mode-locked Nd:CaGdAlO4 (Nd:CGA) laser was demonstrated. By using a semiconductor saturable-absorber mirror (SESAM) as the modulator, stable mode-locked pulses with a duration of 6.0 ps and a repetition rate of 88.3 MHz have been achieved at a central wavelength of 1078.6 nm. The maximum output power of 452 mW was obtained under a pump power of 10 W.

Diode-Pumped Passively Mode-Locked 1079 nm Nd:CaGdAlO4 Laser**Supported by the National Key Basic Research Program of China under Grant No 2013CB922402, and the International Joint Research Program of the National Natural Science Foundation of China under Grant No 61210017.

We demonstrate a diode-pumped passively cw mode-locked Nd:CaGdAlO4 laser operating at 1079nm with a semiconductor saturable absorber mirror for the first time to the best of our knowledge. The threshold pump power of the laser is 180mW. A maximum average output power of 93mW is obtained under the pump power of 1.94 W. The pulse duration of the mode-locked pulses is 3.1 ps and the repetition rate is 157 MHz.

SESAM mode-locked Tm:CALGO laser at 2 µm

GaSb-based SESAM is successfully employed for passive mode locking of a Tm3+:CaGdAlO4 laser operating near 2 µm. The pulse duration is around 650 fs at a repetition rate ~100 MHz.

Diode-pumped Kerr-lens mode-locked Yb:CaGdAlO4 laser with tunable wavelength

We experimentally demonstrated a wavelength tunable Kerr-lens mode-locked femtosecond laser based on an Yb:CaGdAlO4 (Yb:CGA) crystal. The Kerr-lens mode-locked wavelength tuning range was from 1043.5 to 1076 nm, as broad as 32.5 nm, by slightly tilting the end mirror. Pulses as short as 60 fs were generated at the central wavelength of 1043.8 nm with an average output power of 66 mW. By using an output coupler with 1.5% transmittance, the Kerr-lens mode-locked average output power reached 127 mW with a pulse duration of 81 fs at a central wavelength of 1049.5 nm.

Lasing characteristics of a diode-pumped Nd3+ : CaGdAlO4 crystal

A new Nd3+-doped CaGdAlO4 laser crystal was investigated. This crystal was grown by the Czochralski method. The atomic concentration of Nd3+ in the melt was 2%. The absorption and luminescence spectra were analysed and the Stark structure of the upper and lower active levels was determined. The lifetime of the upper level was ∼140 μs. The stimulated emission cross section at the 1078 nm wavelength was 1.1 × 10-19cm2 for the E∥c polarisation. A GaAlAs diode, with an output power of 3 W emitting at the wavelength 806.5 nm, was used as the pump source. The slope efficiency was 37% at the 1078 nm wavelength when the output mirror transmission was 5%. The output radiation power of the crystal laser was 360 mW when the absorbed pump power was 1.29 W.