| It plays an important role of nonlinear 2nd optical effect in people’s understanding and applications of laser. As a practical technology to extend the laser wavebands, the frequency doubling, sum-frequency generation and optical parameter oscillator which are based on nonlinear 2nd optical effect all shown an excellent performance. Currently, optical fiber communications market developed rapidly, various kinds of modules and devices in this waveband owning a fine property and high output power.1560 nm is coincidental the optical fiber communications C band, and it is the low loss window in optical fiber transmission. Relying on 1560 nm fiber amplifier as a fundamental-wave source, we carry out three aspects related works including the second harmonic generation (SHG), sum-frequency generation (SFG) and optical parameter oscillator (OPO), respectively.Since 780 nm corresponds to rubidium D2 transition line, it has important applications in rubidium atom cooling and manipulation as well the controlled triggered single-photon sources.780nm laser generated by direct frequency doubling of 1560nm laser owns high beam quality and high conversion efficiency, which can be one of the ideal programs served to the above applications.520nm laser generated by further sum-frequency generation also owns the same advantages, and there are appealing application prospect in visible laser display, biomedicine and quantum metrology and so on.1560 and 780nm laser generated by the optical parameter oscillator have special place in optical fiber transmission and rubidium atom transition. For example, taking rubidium atom as quantum information storage unit, and 1560nm as the carrier of quantum channel for long-distance information transmission, such a high entangled two-color optical field combination must emerge a huge potential in future long-distance quantum communications.This thesis is focus on optical 2nd nonlinear effect. Combining the maturely developed nonlinear periodically poled crystal, taking optical communications waveband of 1560nm laser as a fundamental wave, with the help of reasonable theoretical analysis and experiential design, we obtained a frequency doubling laser at 780nm by a single-pass configuration and cavity enhanced configuration, a sum-frequency generation at 520nm via a singly resonant sum frequency configuration and the two-color down-conversion optical fields at 1560 and 780nm via a doubly resonant optical parameter oscillator.The major research contents in this thesis are as followings:1) Taking an optical communications C band seed laser amplifier system(1560nm external cavity diode laser as seed laser, erbium-doped fiber amplifier as the seed laser power amplifier), combining novel quasi-phase matched MgO doped periodically poled lithium niobate crystal as the nonlinear media. Applying a single-pass and a cavity enhanced configuration, respectively, and we realized a high-power, high beam quality 780nm laser which is corresponding to rubidium atom D2 transition line. It has been served to the frequency calibration of optical communications waveband;2) Analysis of optical inhomogeneity of the bulk MgO:PPLN crystal. Starting from temperature tuning curve of MgO:PPLN crystal, to the distortion of ideal phase matched of the sinc2 geometrical form, we takes the assumption of partition processes of the refractive index along the optical propagation direction, and we obtained the fitted results which is agreement with the experimental results;3) We deduced the formulas of singly resonant sum-frequency generation, 1560nm fundamental wave laser is converted by a frequency chain of frequency doubling and sum-frequency generation process, we finally obtain satisfactory output power and high beam quality of single frequency sum-frequency generation green laser at 520nm, which are based on a single-pass configuration of PPKTP crystal at 1560nm and a configuration of enhanced sum-frequency generation cavity with second-harmonic optical field at 780nm;4) Combining novel efficient nonlinear periodically poled PPKTP crystal, we obtained a high efficient, broadband wavelength tuning down-conversion two-color optical fields (signal laser at 1.5μm, idler laser at 0.78μm) by a discrete doubly resonant optical parameter oscillator. The wavelength tuning range of the signal laser is 44nm, of the idler laser is 11nm via a changing of PPKTP crystal temperature. Taking a room-temperature natural abundance mixed rubidium atom vapor cell as the frequency rating, when we continuously changed the seed laser frequency of 1560nm fundamental wave, it will realize at least 1.6GHz continuous frequency tuning range of idler laser (780.2nm), it will be an important application to rubidium precision spectroscopy measurement. Such a scheme will be a potential candidate to be served to the long-distance quantum information transmission devices which is used rubidium atom as the quantum storage device (780nm), and the fiber as the quantum channel (1560nm).Innovations of the above works are as follows:1) With the help of a single-pass configuration and an enhanced cavity configuration of frequency doubling, we obtained a high-power, high beam quality 780nm laser. In an hour monitoring time scale, the 780nm laser power fluctuation (RMS) is lower than 1.3%.2) Present the assumption of optical inhomogeneity of MgO doped periodically poled lithium niobate along the optical propagation direction, and we take the assumption theory to fit the experimental data as a verification.3) Periodically-poled potassium titanyl phosphate (PPKTP) combining a singly resonant sum-frequency generation, we obtained a third harmonic of 1560nm laser by a frequency conversion chain.4) Using the 520nm laser as a pump source, we obtained a high efficient two-color down-conversion optical fields at 1560 and 780nm.
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