Investigations of a two-wave laser refractometer

A two-wave laser interference refractometer for measuring the refractive index of air, pure gases, and gaseous mixtures is described. An algorithm for calculating the results of measurements using the method of coincidence of fractional parts of the orders of interference is given.Translated from Izmeritel'naya Tekhnika, No. 7, pp. 29–31, July, 1993.     

Analysis of errors of a three-channel laser interferential fluid refractometer

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 25–28, May, 1990.     

Simple autocollimation laser refractometer with highly sensitive, fiber-optic output

A simple autocollimation scheme for a laser refractometer with a highly sensitive, single-mode, fiber-optic output is described. It allows for the determination of the refractive index and dispersion of optical materials with an accuracy exceeding 10(-5), which is confirmed by both experimental and analytical investigations.     

A liquid laser interference refractometer for measuring the concentration of solutions

A liquid interference refractometer is described. The results of an investigation of the instrument and of its practical use to measure the concentration of aqueous solutions of caprolactam are presented.Translated from Izmeritelnaya Tekhnika, No. 12, pp. 58–61, December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Laser interference refractometer for monitoring the absolute index of refraction of air

An interference gas refractometer circuit based on a unimodal laser is proposed. By means of the device it is possible to measure the absolute index of refraction of air over a broad range with error at most 10⁻⁸. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 25–31, April 1998.     

Effect of the finite dimensions of the probing beam on measurements using a laser scanning refractometer

Translated from Izmeritel'naya Tekhnika, No. 8, pp. 40–42, August, 1992.     

Measurement of the linewidth of a continuous-wave laser with a cavity-length modulation technique

We introduce a Fabry-Perot cavity-length modulation technique for measuring the linewidth of a continuous wave (cw) laser. We calculate the peak intensity of a cw laser transmitted through a Fabry-Perot cavity as a function of mirror speed. By fitting the experimental data to the results of the calculation, we determine the linewidth of a frequency-stabilized cw laser. The linewidth of a cw ring dye laser measured in the 570-590-nm wavelength range is approximately 170 +/- 20 kHz. We also demonstrate the use of this technique to measure the reflectivity of a high-reflectance mirror.     

Measurement of the lidar ratio for atmospheric aerosols with a 180 degrees backscatter nephelometer

Laser radar (lidar) can be used to estimate atmospheric extinction coefficients that are due to aerosols if the ratio between optical extinction and 180 degrees backscatter (the lidar ratio) at the laser wavelength is known or if Raman or high spectral resolution data are available. Most lidar instruments, however, do not have Raman or high spectral resolution capability, which makes knowledge of the lidar ratio essential. We have modified an integrating nephelometer, which measures the scattering component of light extinction, by addition of a backward-pointing laser light source such that the detected light corresponds to integrated scattering over 176-178 degrees at a common lidar wavelength of 532 nm. Mie calculations indicate that the detected quantity is an excellent proxy for 180 degrees backscatter. When combined with existing techniques for measuring total scattering and absorption by particles, the new device permits a direct determination of the lidar ratio. A four-point calibration, run by filling the enclosed sample volume with particle-free gases of a known scattering coefficient, indicates a linear response and calibration reproducibility to within 4%. The instrument has a detection limit of 1.5 x 10(-7) m(-1) sr(-1) (~10% of Rayleigh scattering by air at STP) for a 5-min average and is suitable for ground and mobile/airborne surveys. Initial field measurements yielded a lidar ratio of ~20 for marine aerosols and ~60-70 for continental aerosols, with an uncertainty of ~20%.     

热风式大气湍流模拟装置的哈特曼测量

大气湍流是由于大气温度、压强的随机变化引起大气折射率随机改变而产生的。遵循这一原理,热风式湍流模拟装置对传输光束周围的空气加热,用风扇抽吸热空气产生湍流,通过改变加热温度和风扇的转速,模拟不同强弱的湍流。用哈特曼传感器对该装置进行测量并采集数据,通过波前斜率处理复原波前,在此基础上从时间域和空间域等方面分析所产生湍流的特点,并与理论进行比较。结果表明,该装置能产生基本符合大气湍流统计理论的湍流。     

Measurement of small amplitudes of vibration with a laser vibrometer

A method is examined for measuring amplitudes of vibration based on harmonic analysis of the output signal of a Michelson interferometer, with modulation of the frequency of radiation in the reference arm. The advantages of the method are explained and a specific example of its use is given. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 29–32, November, 1999.