Engineering Studv Of The Nanosecond Pulse Mid-infrared Laser Based On Optical Parametric Oscillator

Mid-infrared(MIR) Laser has great practical value in the field of wireless communication, remote sensing, spectrum analysis, environmental detection, atmospheric composition analysis, and so on. In particular, because of its high power and low atmospheric loss, the nanosecond MIR laser has a very important application value in the military confrontation. The optical parametric oscillator(OPO) based on quasi phase matching(QPM) is an effective method to obtain MIR laser. At the same time, it has the characteristics of tunable wavelength and high output power, which makes it obvious advantages than other technology. In recent years, near infrared laser technology and nonlinear crystal polarization technology has been developed, so that the research of the MIR laser is no longer confined to the laboratory level, and it can be developed to the direction of the project. In this paper, commercial nanosecond Lasers with high power and good stability are used as the pumping source, and the MgO:PPLN crystal is used as the nonlinear crystal. Then, with the method of disturbing flow,3D printing technology, integral forming technique and strengthening rib structure, the prototype is made successfully and solves the problem of the power instability of MIR laser. Besides, the fiber laser with small size, high power (all wind cooling), better stability is used as a pumping source, so that the volume of the whole machine is reduced by more than half. Finally, using multi period MgO:PPLN crystal, through a programmable logic controller (PLC) technology, temperature control technology and the precise displacement technology, we make the controller which can control the amount of power and wavelength tuning. A set of control software is written to solve the problem of difficult wavelength tuning. The main contents include the following aspects:1. We use the LD pumped Nd:YVO4 solid state laser as the pumping source, and develop a prototype by the engineering method, which is characterized by good beam quality, high efficiency and good stability. The prototype’s average output power at 3.74μm is 1.95W, and power stability (RMS) during 24 hours is 1.13%. This prototype has passed the Power ON-OFF test, long run test, vibration test and remote acceptance test, and it is found that the effect of using it to interfere infrared detector is obvious.2.Then, high power solid slab laser is used as pumping source. The research of high power MIR laser is carried out, and the reasons of the damage of optical elements are analyzed. Finally, the output power of 3.8μm laser is 12.2W and 2.7μm laser is 34.4W.3. The advantages of the fiber laser are analyzed, and the fiber laser is used as the pumping source. According to the characteristics of the fiber laser, a small size, all air cooling, dual wavelength of nanosecond MIR laser is developed. The prototype has passed the reliability test and the remote acceptance test, and the user feedback is good.4. With the use of the fiber laser as the pumping source and the multi period MgO: PPLN crystal with 8 channels, the wavelength tuning range of the infrared laser is obtained from 1.41μm to 4.33μm. A controller is made by using PLC, temperature controller and the precise electric translation table, which can control the amount of the output power and wavelength setting value, and a set of control software is written which has friendly software interface and is easy to operate.