Distribution of numbers of photons in the region of unstable behavior in the process of intracavity second harmonic generation

For the process of intracavity second harmonic generation we investigate in positive P-representation with simulation of Langevin noise sources the distribution functions of numbers of photons in fundamental and second harmonic modes in the region of unstable behavior of the system. It is shown that in the unstable region, as distinct from the stable, the functions of distribution have two-peak structure. We also study the joint function of distribution of photon numbers in interacting modes.     

Fluctuations in the number of photons above the bifurcation point in the process of third harmonic generation

The quantum fluctuation of the number of photons of the fundamental mode and of the third harmonic in the process of intracavity generation of the third harmonic in the region of unstable behavior of the system is studied. The distribution functions of the number of photons of interacting modes, as well as the function of the joint distribution of the number of photons of the fundamental mode and of the third harmonic, are calculated in the positive P-representation.     

Mode-coupling phenomena in intracavity second harmonic generation

The dependence of intracavity second harmonic generation efficiency on the linear phase detunings in crystal and air is studied both theoretically and experimentally. It is shown that in the presence of feedback at the second harmonic frequency an optimum conversion efficiency can be achieved by a mutually correlated choice of phase mismatch in a nonlinear crystal and the position of the latter inside the cavity.     

Evolution dynamics of initial coherent states of a field in an unstable region of the behavior in the process of intracavity third harmonic generation

The quantum dynamics of the state of a field is studied for the process of intracavity third harmonic generation in the region of unstable behavior of the system in the case in which the interacting modes are developed from initial coherent states. It is shown that the Wigner functions of the states of the modes and mean values of the quadrature amplitudes of the fields can have oscillations disappearing with the transition of the system to a stable region.     

Correlation of quadrature amplitude fluctuations during the intracavity generation of second harmonic

For the process of intracavity generation of the second harmonic, the dynamics of correlation of quadrature amplitudes fluctuations of the fundamental and the second harmonic modes is studied depending on the nonlinear coupling coefficient between the modes. It was shown that in this system the entangled states of field related to variables of quadrature amplitudes may be obtained depending on the nonlinear coupling coefficient. It was also shown that the entanglement of the states of field modes related to one quadrature amplitude may vanish depending on the value of nonlinear coupling coefficient, whereas the states of field modes related to the other quadrature amplitude stay entangled.     

Fluctuations of second harmonic generated light

We calculate the statistical properties of light, arising by second harmonic generation from stationary quasimonochromatic light fields as thermal and single-mode laser light. After a derivation of the correlationfunctions we draw conclusions about spectral densities and the expected results for photon-counting experiments for the converted light.     

Use of nonlinear properties of intracavity type II second harmonic generation for image processing

We discuss the use of intracavity type-II second harmonic generation for all-optical processing of images. Injecting an image in a pump beam linearly polarized and a homogeneous field in the orthogonally polarized pump, it is possible to magnify the contrast and to recognize the contour of any part of the image whose intensity is above a tunable reference level. This can be done using ideal planar cavities where all the fields are resonant as well as in the more realistic situation where only the fundamental fields are resonant and using cavities with spherical mirrors. PACS 42.30.-d; 42.65.Ky; 42.65.Pc     

光抽运垂直扩展腔面发射激光器腔内倍频理论研究

建立了计入光波在非线性晶体中走离和相位失配情况下的光泵面发射激光器腔内倍频的速率方程理论模型,采用循环数值逼近的方法对该速率方程进行求解.以BBO,LBO,PPLN等非线性晶体为例,研究了晶体长度以及抽运功率等因素对倍频输出功率的影响,模拟结果与实验结果符合得较好. 关键词： 光抽运 垂直扩展腔面发射激光器 腔内倍频 数值模拟     

Spontaneous 2D modulation instability in second harmonic generation process

Two-dimensional modulation instability (2DMI) is experimentally demonstrated in a classical second harmonic generation setup. The spatial spectrum is measured and reveals typical 2DMI bands, in agreement with the analytical MI model. These observations are confirmed by (2 + 1)D numerical simulations.     

Quantum dynamics of formation of an unstable field state in the process of intracavity third-harmonic generation

The dynamics of the Wigner functions and quantum entropy of the fundamental and third-harmonic modes is studied for the process of intracavity third-harmonic generation. It is shown that quantum dynamics of the system strongly depends on the coupling coefficient of the interacting modes. The dynamics of the transition of the system from a stable to an unstable state is investigated.     

Calculation of the stationary generation power of a solid-state raman laser with intracavity second harmonic generation and sum frequency mixing

Analytical equations for the power of second-harmonic stationary generation or sum frequency mixing in a Raman laser with an intracavity nonlinear medium are developed and analyzed as functions of pumping mode and other parameters of the laser system. Parameter relationships providing the maximum output power and conditions for suppression of both stimulated Raman scattering by sum frequency mixing and; consequently, of sum frequency mixing itself are found.     

Self pulsing in second harmonic generation

We consider nonlinear optical processes in a cavity maintained far from thermal equilibrium by external pumping. In second harmonic generation we predict a hard mode instability at a critical pump strength indicating the existence of undamped spiking similar to that in strongly pumped lasers. In subharmonic generation above the soft mode transition noted by Graham we predict the appearance of sidebands in the subharmonic spectrum.     

Noncollinear second harmonic generation in KDP

This paper reports experimental and analytical results on optical second harmonic generation when a noncollinear arrangement is employed. The dependence of second harmonic power on crystal length, absorption, beam radius and the angle between the two fundamental waves is obtained. Double refraction of the crystal is taken into account, but the divergence and depletion of the fundamental waves are neglected. The results of the calculations are confirmed by experiments carried out with a KDP crystal in the near field of two intersecting TEM₀₀ ruby laser beams.An extension of the theory to nonlinear interactions other than second harmonic generation - e.g. four-wave interaction - is possible.     

Efficient second harmonic generation in CDA

Efficient second harmonic generation at 0.532 μ has been achieved in a temperature tuned CDA crystal when a narrow beam divergence Nd:YAG laser was used. At a crystal temperature of 40.3°C, a peak second harmonic power of 7.5 MW was obtained with a peak power conversion efficiency of 33%. The temperature variation of the refractive indices in CDA has been determined to be d(n^e_2ω?n⁰_ω)/dT = 7.2 × 10^?5°C^?1.     

Monitoring process of human keloid formation based on second harmonic generation imaging

In this paper, the morphological variation of collagen among the whole dermis from keloid tissue was investigated using second harmonic generation (SHG) microscopy. In the deep dermis of keloids, collagen bundles show apparently regular gap. In the middle dermis, the collagen bundles are randomly oriented and loosely arranged in the pattern of fine mesh while the collagen bundles are organized in a parallel manner in the superficial dermis near the epidermis. The developed parameters COI and BD can be used to further quantitatively describe these changes. Our results demonstrate the potential of SHG microscopy to understand the formation process of human keloid scar at the cellular level through imaging collagen variations in different depth of dermis.     

二次谐波产生过程中准相位匹配条件的研究

从耦合波基本方程出发,在实空间严格推导出二次谐波产生(SHG)过程中的准相位匹配(QPM)条件.讨论了满足QPM条件时,SHG的转换效率以及相位失配角随波传播距离的变化.着重研究了非线性极化率的周期性调制对提高SHG转换效率的贡献.     

Optical second harmonic generation in ammonium tartrate

Second harmonic generation was observed in ammonium tartrate single crystals by a phase matching technique at the fundamental wavelength 1.153 μm. The nonlinear coefficients were found to be comparable in magnitude to those of KDP. The optical transmission and the refractive indices were also measured.     

Optical second harmonic generation in ammonium malate

Second harmonic generation in ammonium malate has been investigated in a wavelength region between 492 nm (short wavelength limit of the harmonic beam at 246 nm) and 640 nm. Phase match angle, refractive indices and all coefficients of the nonlinear susceptibility tensor have been measured; several possibilities for phase matching are discussed.