Yaping Shang

Ultra-stable high-power mid-infrared optical parametric oscillator pumped by a super-fluorescent fiber source

The longterm stability of the laser system is very important in many applications. In this letter, an ultra-stable, broadband, mid-infrared (MIR) optical parametric oscillator (OPO) pumped by a super-fluorescent fiber source is demonstrated. An idler MIR output power of 11.3 W with excellent beam quality was obtained and the corresponding pump-to-idler conversion slope efficiency was 15.9%. Furthermore, during 1h measurement at full power operation, the peak-to-peak fluctuation of idler output power was less than 1.9% and the corresponding standard deviation was less than 0.4% RMS, which was much better than that of a traditional single mode fiber laser pumped OPO system (10.9% for peak-to-peak fluctuation and 1.8% RMS for the standard deviation) in another experiment for comparison. To our knowledge, this is the first demonstration on a high-power, ultra-stable OPO system by using the modefree pump source, which offered an effective approach to achieve an ultra-stable MIR source and broadened the range of the super-fluorescent fiber source applications.

Study on high-power continuous-wave mid-infrared optical parametric oscillator

3~5μm mid-infrared laser has many important applications, such as gas detection, spectral analysis, remote sensing, medical treatment, and also in the military laser radar, infrared countermine, and so on. Optical parametric oscillator (OPO) is an efficient way to generate laser in this wavelength range, which has attracted the eyes of many people. In this paper, the recent development of mid-infrared OPO is overviewed. Meanwhile, detailed introduction on our recent work is given. Maximum idler output power of 34.2W at center wavelength of 3.35μm was obtained, to our knowledge, which is the new power record of the international public reporting for the continue-wave (CW) mid-infrared OPO. It is worth mentioning that the pump source, the quasi single-frequency (SF) narrow line width fiber laser, was also developed by our groups. According to the current status of research, some solutions is proposed in order to achieve higher power, narrower line width, and compact volume mid-infrared OPO in a wide tunable range.

Theoretical research of beam combination between hollow beam and Gaussian beam

The near and far field intensity distribution as well as the beam quality of the combination between the hollow beam generated by double axicons and the Gaussian beam were simulated in this paper. The simulation results revealed that several parameters like the interval between two axicons and the phase difference between the two beams would influence the intensity distribution of the combined beam, especially the phase difference between the hollow beam and Gaussian beam which could transforms the far-field intensity distribution into quasi-hollow distribution or peak shaped distribution and was of great potentiality in the industry application.

Investigation of hollow beam generated by double axicons and its propagation properties

The hollow beam has a variety of special physical properties and can be applied to the optical catheter, optical trap, generation of the light trap and many other important fields. In this paper the light-field conversion of the Gaussian beam passing through double axicons and generating the hollow beam is theoretical derived and simulated using the light-field propagation method. The influence of several parameters on the near and far field intensity distribution of the hollow beam is discussed. We find that the hollow beam with different light-field can be generated by controlling these parameters and this has a great potential in terms of micro manipulation, optical trap and other fields.

Mid-infrared optical parametric oscillator pumped by an amplified random fiber laser

Recently, the concept of random fiber lasers has attracted a great deal of attention for its feature to generate incoherent light without a traditional laser resonator, which is free of mode competition and insure the stationary narrow-band continuous modeless spectrum. In this Letter, we reported the first, to the best of our knowledge, optical parametric oscillator (OPO) pumped by an amplified 1070 nm random fiber laser (RFL), in order to generate stationary mid-infrared (mid-IR) laser. The experiment realized a watt-level laser output in the mid-IR range and operated relatively stable. The use of the RFL seed source allowed us to take advantage of its respective stable time-domain characteristics. The beam profile, spectrum and time-domain properties of the signal light were measured to analyze the process of frequency down-conversion process under this new pumping condition. The results suggested that the near-infrared (near-IR) signal light ‘inherited’ good beam performances from the pump light. Those would be benefit for further develop about optical parametric process based on different pumping circumstances.

30 Watts mid-infrared optical parametric oscillator based on spectral beam combination technology

Limited by the thermal effects and the laser-induced damage characteristics of the non-linear crystals, mid-infrared (MIR) output power of single optical parametric oscillator (OPO) is hard to get further promoted with excellent beam quality. An alternative solution is the multiple-beams combination technology, which exactly provided an effective approach for decreasing the thermal effects and the damage risk of the OPO system under high power operation. In this letter, the experimental study on the spectral beam combination of three idler MIR lasers was carried out for the first time. An optical parametric system with MIR output power of 30 W at 3130nm, 3352nm, and 3670nm was finally obtained. Experimental results indicated that the beam quality M2 factors of the combined laser were measured to be ~1.76 and ~2.42 in the horizontal and vertical directions, respectively, which confirmed the feasibility of the schematic design.

A fiber-laser-pumped four-wavelength continuous-wave mid-infrared optical parametric oscillator

In this paper, a four-wavelength continuous-wave mid-infrared optical parametric oscillator was demonstrated for the first time. The pump source was a home-built linearly polarized Yb-doped fiber laser and the maximum output power was 72.5 W. The pump source had three central wavelengths locating at 1060 nm, 1065 nm and 1080 nm. Four idler emissions with different wavelengths were generated which were 3132 nm, 3171 nm, 3310 nm and 3349 nm under the maximum pump power. The maximum idler output reached 8.7 W, indicating a 15% pump-to-idler slope efficiency. The signal wave generated in the experiment had two wavelengths which were 1595 nm and 1603 nm under the maximum pump power. It was analyzed that four nonlinear progresses occurred in the experiment, two of them being optical parametric oscillation and the rest two being intracavity difference frequency generation.

Frequency downconversion of an amplified, full-open cavity random fiber laser

Abstract. The experimental results of a temporally stable, continuous wave, midinfrared (MIR), singly resonant optical parametric oscillator pumped by an all-fiberized master oscillator power-amplifier structured random fiber laser (RFL) is presented. The maximal idler output power of 4.35 W was achieved at 3271 nm with good beam quality, and the corresponding pump-to-idler slope efficiency was up to 17.1%. The idler output power exhibited a peak-to-peak fluctuation better than 3.2% RMS at the maximum output power over 20 min. Meanwhile, other characteristics of the generated idler MIR laser had been discussed in details, which offered effective guidance on the research of the frequency downconversion process in the case of temporally incoherent light and broadened the range of RFL applications.

High power mid-infrared continuous-wave optical parametric oscillator pumped by fiber lasers

3~5μm mid-infrared laser has many important applications, such as gas detection, spectral analysis, remote sensing, medical treatment, and also in the military laser radar, infrared countermine, and so on. Optical parametric oscillator (OPO) is an efficient way to generate laser in this wavelength range, which has attracted the eyes of many people. In this paper, the recent development of mid-infrared OPO is overviewed. Meanwhile, detailed introduction on our recent work is given. Maximum idler output power of 34.2W at center wavelength of 3.35μm was obtained, to our knowledge, which is the new power record of the international public reporting for the continue-wave (CW) mid-infrared OPO. It is worth mentioning that the pump source, the quasi single-frequency (SF) narrow line width fiber laser, was also developed by our groups. According to the current status of research, some solutions is proposed in order to achieve higher power, narrower line width, and compact volume mid-infrared OPO in a wide tunable range.

Theoretical explanation of the polarization-converting system achieved by beam shaping and combination technique and its performance under high power conditions

The fiber laser has very obvious advantages and broad applications in remote welding, 3D cutting and national defense compared with the traditional solid laser. But influenced by heat effect of gain medium, nonlinear effect, stress birefringence effect and other negative factors, it’s very difficult to get high power linearly polarized laser just using a single laser. For these limitations a polarization-converting system is designed using beam shaping and combination technique which is able to transform naturally polarized laser to linearly polarized laser at real time to resolve difficulties of generating high-power linearly polarized laser from fiber lasers in this paper. The principle of the Gaussian beam changing into the hollow beam passing through two axicons and the combination of the Gaussian beam and the hollow beam is discussed. In the experimental verification the energy conversion efficiency reached 93.1% with a remarkable enhancement of the extinction ratio from 3% to 98% benefited from the high conversion efficiency of axicons and the system worked fine under high power conditions. The system also kept excellent far field divergence. The experiment phenomenon also agreed with the simulation quite well. The experiment proves that this polarization-converting system will not affect laser structure which controls easily and needs no feedback and controlling system with stable and reliable properties at the same time. It can absolutely be applied to the polarization-conversion of high power laser.