Baoyin Zhao

4.62 kW excellent beam quality laser output with a low-loss Yb/Ce co-doped fiber fabricated by chelate gas phase deposition technique

A high-power Yb/Ce co-doped double-clad fiber with low optical loss was successfully fabricated by an optimized chelate gas phase deposition technique. It exhibits a nearly homogenous distribution of Al, Ce and Yb ions in the fiber core region, which reduce the clustering. The core attenuation at 1080 nm and 1383 nm are 12 dB/km and 46 dB/km, respectively, indicating high optical performance with a low optical loss. The amplifier stage with this fiber delivers 4.62 kW excellent beam quality (M2 = 1.67) laser output with a slope efficiency of 80.3%. The experimental results show that the chelate gas phase deposition technique is a prospective method to fabricate a Yb/Ce co-doped fiber with low optical loss, which is beneficial for acquiring multi-kilowatt continuous-wave fiber laser with excellent beam quality.

Ytterbium-doped double-cladding fiber with 3.5 kW output power, fabricated by chelate gas phase deposition technique

A ytterbium-doped double-cladding fiber was successfully fabricated by a chelate gas phase deposited technique. The measurement results of dopant concentration distribution and refractive index of preform indicate that radial and longitudinal homogeneity could be controlled perfectly with this technique. The absorption coefficients of fiber are 0.39 dB/m at 915nm and 1.02 dB/m at 976nm respectively. Using this fiber as the laser amplifier stage, 3592W output power at 1080nm with 72.5% slope efficiency was obtained with end-pump technique, which is close to the test results of Nufern commercial fiber. The results demonstrate that the chelate gas phase deposition technique is a relatively promising technique for high quality gain fiber fabrication.

High pumping-power fiber combiner for double-cladding fiber lasers and amplifiers

Abstract. A high pumping-power fiber combiner for backward pumping configurations is fabricated and demonstrated by manufacturing process refinement. The pump power handling capability of every pump fiber can extend to 600 W, corresponding to the average pump coupling efficiency of 94.83%. Totally, 2.67-kW output power with the beam quality factor M2 of 1.41 was obtained, using this combiner in the fiber amplifier experimental setup. In addition, the temperature of the splicing region was less than 50.0°C in the designed combiner under the action of circulating cooling water. The experimental results prove that the designed combiner is a promising integrated all-fiber device for multikilowatt continuous-wave fiber laser with excellent beam quality.

Growth and lasing performance of a Tm,Y:CaF 2 crystal

A Tm3+ ion and Y3+ ion co-doped CaF2 crystal was grown and characterized, in which spectral and lasing performance was presented for the first time, to the best of our knowledge. Under diode end-pumping, in a continuous-wave regime, maximum output power of 453 mW was delivered under an absorption pump power of 2.5 W, corresponding to an optical-to-optical conversion efficiency of 17.9% and a slope efficiency of 21%. With a birefringent quartz plate, wavelength-tunable operation with a tunable range of more than 190 nm was realized. The results show that Tm,Y:CaF2 is a promising laser crystal operating in a spectral region ranging from 1850 nm to 2050 nm.

KW-level low photodarkening Yb/Ce codoped aluminosilicate fiber fabricated by the chelate gas phase deposition technique

A Yb/Ce codoped aluminosilicate fiber was successfully fabricated by the chelate gas phase deposition technique. Using the homemade fiber as the amplifier stage in a master oscillator power amplifier configuration laser setup, a near single mode laser output (M2 = 1.55) with an output power of 1026 W and slope efficiency of 84.8% is obtained. In the 100 hour photodarkening experiment, the entire reduced power is less than 14 W, and the ratio, compared to the initial 1026 W output power, is less than 1.4%. The investigation of optical properties indicates that Yb/Ce codoped aluminosilicate fiber fabricated by the chelate gas phase deposition technique shows homogenous distribution, appropriate absorption coefficient, low background attenuation, high optical-to-optical efficiency and a rather low photodarkening loss, making it a promising candidate as an active fiber for a reliable and efficient fiber laser in high-power applications.

Kilo-hertz-level Q-switched laser characteristics of a Tm,Y:CaF 2 crystal

Employing an acousto-optic modulator (AOM), the Q-switched laser characteristics of a Tm,Y:CaF2 crystal have been investigated. With T = 1%, 2% and 5% output couplers (OCs), output laser performance in both continuous-wave (CW) and Q-switching regimes have been presented and are discussed in details. The AOM Q-switched Tm,Y:CaF2 laser can run at high repetition rates ranging from 1 kHz to 10 kHz. Under the modulation frequency of 1 kHz, pulses with the shortest duration of 280 ns and the maximum pulse energy of 0.335 mJ have been delivered, corresponding to a maximum peak power of 1.19 kW. The results indicate that Tm,Y:CaF2 crystals can act as a promising candidate of gain medium for pulsed 2 μm laser.