Polarization effects in a high-birefringence elliptical fiber laser with a Bragg grating in a low-birefringence fiber

The polarization characteristics of a fiber laser cavity that combines a high-birefringence Er(3+)-doped elliptical core fiber with a Bragg grating fabricated in a low-birefringence (Low-Bi) fiber are studied. It is shown that, by use of an adequate length of Low-Bi fiber and an intracavity polarization controller, the dependence of the fiber laser's state of polarization on the pump's state of polarization can be altered. This fiber laser cavity design allows for the realization of a double-frequency, orthogonally polarized single-mode fiber laser source insensitive to the polarization parameters of the pump source.     

Polarization characteristic of a room-temperature Co:MgF2 laser

A study of the polarization characteristic of a Co:MgF2 laser with a 1320-nm YAG pumping laser at room temperature is reported. The thresholds, output energies, and efficiencies of the laser are given at the various polarization states. The more intensive emission is in the pi-polarization pump laser and sigma-polarization laser operation. Performances of the Co:MgF2 lasers are similar for the polarized and unpolarized laser pumping along the optical axis of the crystal.     

Orthogonal planar laser polarization spectroscopy

Planar laser polarization spectroscopy has recently been used to image the hydroxyl radical in combustion for small intersection angles of pump and probe beams. We report an experimental configuration that allows planar laser polarization imaging for perpendicular intersection of pump and probe beams. We demonstrate what to our knowledge is the first planar laser polarization spectroscopy imaging at a 90 degree intersection of pump and probe beams for both linearly and circularly polarized pump beams.     

Polarization switching time for semiconductor laser radiation

Expressions are derived for the polarization switching time for semiconductor laser radiation. These expressions can be used to assess the influence of the laser diode parameters on the polarization switching time of the output radiation. The results of an analysis of these expressions show that the main parameters influencing the polarization switching of the output radiation from a semiconductor laser are the nonlinear gains. Pis’ma Zh. Tekh. Fiz. 23, 87–95 (May 12, 1997)     

Non-sequential double ionization of argon by elliptically polarized laser pulses

With a classical ensemble model, we investigated non-sequential double ionization (NSDI) of argon by elliptically polarized laser pulses. The results show that the correlation behaviors of two electrons depend strongly on the laser intensity. At relatively high laser intensity, the momentum spectra of two electrons along the long axis of the laser polarization plane are mainly distributed in the first and third quadrants and display V-like structures. However, at relatively low laser intensity, the momentum spectra of two electrons are mainly distributed in the second and fourth quadrants. By back analyzing the classical trajectories of NSDI, we find that all of the successful NSDI events still come from recollision in the cases of elliptically polarized laser pulses, and the final-state electron repulsion plays a decisive role for the V-like structure along the long axis of the laser polarization plane. In addition, we find that the initial velocity of the first electron at ionization along the short axis of the laser polarization plane are essential for the recollision, and the time delay between the first ionization and recollision depends on the ellipticity strongly.     

Polarimetric distributed feedback fiber laser sensor for simultaneous strain and temperature measurements

We report the application of a dual polarization distributed feedback (DFB) fiber laser as a strain and temperature sensor. By measurement of the absolute wavelength of one polarization as well as the polarization beat frequency, strain and temperature were determined simultaneously. The sensor has an accuracy of +3 microepsilon and +/-0.04 degrees C. Self-heating of the DFB fiber laser as a function of pump power was measured with this sensor.     

偏振编码型光纤天线激光告警机的设计

为丁在激光告警中实现全方位角度探测,并且在一定探测精度的前提下尽量使结构简单、稳定,提出了基于偏振编码的光纤天线的测量方法.该方法是通过在不同方向上放置不同起偏角的偏振片编码,再将各个方向的光纤耦合成一束,经准直透镜组射入解偏光路中,通过判断电路分析得到激光入射方向.在计算及仿真了经偏振片后激光能量的衰减,求解电路能检测到最弱激光的幅值与偏振衰减最大时激光引起的响应电流的幅值的关系,得到在激光角分辨率为30°时满足探测要求.实验显示,在初始激光功率在20～150 mW的条件下,每20°划分的偏振角度中设定最小识别电压为20 mV时,满足全方位激光方向探测的要求.     

Mode-locked diode-pumped self-frequency-doubling neodymium yttrium aluminum borate laser

As far as we know this is the first report on picosecond green-light generation from an actively mode-locked diode-pumped self-doubling neodymium yttrium aluminum borate (NYAB) laser. The pulse width is approximately 100 ps and is limited by imperfect antireflection coating and the intracavity doubling effect. The green average output power of this laser for mode-locked operation was more than 12 times higher than that for the continuous wave NYAB laser. The polarization state of the laser can be switched from ordinary to extraordinary rays by displacement of the pump spot. The polarization ratio can be better than 200 without any intracavity polarization element.     

Metamaterial-based polarization control plate for producing incoherent laser irradiation

We present a metamaterial-based random polarization control plate to produce incoherent laser irradiation by exploiting the ability of metamaterial in the local polarization manipulation of a beam upon transmission via tuning its local geometry. As a proof of principle, we exemplify this idea numerically in a simple optical system using a typical L-shaped plasmonic metamaterial with locally varying geometry, from which the desired polarization distribution can be obtained. The calculating results illustrate that this scheme can effectively suppress the speckle contrast and increase irradiation uniformity, which has potential to satisfy the increasing requirements for incoherent laser irradiation.     

Stable,Efficient, Single-mode Operation of a High Repetition Rate Grazing Incidence Dye Laser

Abstract

A pulsed, grazing incidence dye laser has been designed to oscillate at a repetition rate of 6·5 kHz in a single, narrow and stable, axial mode with a high excitation conversion efficiency. A single mode efficiency of 12% has been measured in a near diffraction limited beam. No measurable fluctuations of the central laser wavelength or the 100–150 MHz single mode linewidth were observed during an hour of observation. The effect of grating incident angle and dye flow rate on laser operation have been investigated and a correlation has been found between the state of polarization of the dye laser output and the polarization of the pump laser.     

Effect of laser-radiation polarization on the nonlinear scattering of light in nanodiamond suspensions

The effect of laser radiation polarization on the nonlinear scattering of light in aqueous suspensions of detonation nanodiamonds (DNDs) in a regime of optical power limiting (OPL) has been studied. It is established that the nonlinear transmission coefficient of DND suspension in the OPL regime in a field of nanosecond laser pulses with a wavelength of 532 nm is independent of the polarization of incident radiation. The nonlinear scattering of light observed at an angle of 90° in the plane perpendicular to the plane of polarization of the incident radiation depends on the polarization angle in accordance with a trigonometric law. It is shown that the ratio of the signals of scattered radiation for the vertical and horizontal polarizations exhibits nonmonotonic dependence on the laser-beam power density. The results are explained by the Rayleigh-Mie scattering and a change in the size of scattering centers as a result of the effect of a laser upon the DND suspension.     

Efficient linearly polarized ytterbium-doped fiber laser at 1120 nm

We report a 20 W linearly polarized, spectrally clean Yb-doped fiber laser at 1120 nm with an optical conversion efficiency of 54%. An excellent polarization extinction ratio of more than 23 dB is obtained using fiber Bragg gratings (FBGs) polarization selection technique at all power levels. The results reveal that a Yb-doped fiber laser at 1120 nm could be a promising replacement compared to Raman fiber lasers.     

Common-path optical heterodyne profilometer: a configuration

A novel configuration that combines a linearly polarized He-Ne laser and a birefringent lens to produce a common-path polarized optical heterodyne profilometer with respect to the heterodyned P and S waves has been set up. In this profilometer a linear polarized frequency-stabilized He-Ne laser was used with an acousto-optical modulator to replace the Zeeman laser as the light source that had two polarization eigenstates in different temporal frequencies. The proposed interferometer shows a more symmetric and ideal common-path structure than the conventional optical heterodyne profilometers with the Zeeman laser. The phase error aroused by the elliptical polarization and the nonorthogonality of the two eigenpolarization modes of the Zeeman laser can be reduced. The system's resolution in the vertical direction reaches 2 A, and in a 27-mum scanning range the repeatability of the surface profile measurements is shown to be 5 A.     

Measurement of surface roughness profile by a triangulation method

Some aspects of measuring surface roughness parameters using a laser triangulation method are considered. A connection is established between surface roughness and scattering indicatrices with probing radiation polarization parameters of a semiconductor laser. A marked effect is noted of the form and position of the polarization plane on the measurement error for linear values. __________ Translated from Metrologiya, No. 6. pp. 21–27, June, 2008.     

多束相干光叠加的计算机模拟

研究了具有空间不对称分布的多束相干光的叠加问题。对参考平面上相干光产生的干涉光强分布进行理论推导和数值计算,从理论上定量地分析了多束相干光的波矢量、偏振态对干涉光强分布的影响。模拟结果表明波矢量的改变主要影响干涉光强的空间分布,激光束偏振态的改变主要影响干涉场的对比度。     

Tunable multiwavelength fiber laser based on a double Sagnac HiBi fiber loop

A tunable multiwavelength fiber laser based on double Sagnac loops is proposed and demonstrated. Comb filter characteristics of single and double Sagnac loops are analyzed by Jones matrix. Simulated results show that there are better tunability and controllability with double loops than with a single loop, and this also has been confirmed by experimental results. By adjusting the polarization controller and the length of the polarization maintaining fiber the wavelength range, wavelength spacing, and laser linewidth can be tuned. Experimental results indicate that the linewidth of the multiwavelength fiber laser was 0.0187 nm and the optical sidemode suppression ratio was 50 dB.     

Multibeam scanning optics with single laser source for full-color printers

In the novel optical system described here, four-color toners can be developed in one rotation of the photoconductor, and the color control information is given when the intensities of the laser power levels are changed and the two polarization directions are switched. A polarizing beam splitter between the common scanning optics and the photoconductor enables the laser beam to pass through a common scanning system and to illuminate two positions on the photoconductive material. The laser beam polarization direction is controlled by an electro-optical device immediately behind the laser. In each illuminated position, two-color toners are developed by a three-level (trilevel) photographic process. This simplified optical system eliminates the registration errors that occur with four-color information items and can be useful in high-speed printing systems.     

Prelase stabilization of the polarization state and frequency of a Q-switched, diode-pumped, Nd:YAG laser

We present an experimental investigation of the energy statistics of the linear polarization components of pulses from a Nd:YAG laser that is repetitively Q-switched with an acousto-optic modulator. Varying the modulator-induced diffraction losses leads to changes in the pulse polarization state and the energy statistics of the polarization components. For conventional Q-switching there is no laser oscillation during the low-Q intervals, and we find that the orthogonal components of the pulses can display large relative energy fluctuations even though the total pulse energy is quite stable. In the prelase mode, a weak continuous-wave background seeds the Q-switched pulses and results in the emission of highly linearly polarized, single-longitudinal-mode pulses with small relative energy fluctuations.