Iodine stabilized dye laser system for frequency measurements in the visible and near IR region of the spectrum

An iodine stabilized dye laser system is described that provides traceable measurement of reference frequencies in the visible spectrum from 540 to 670 nm and in the near infrared at 1.15 /spl mu/m. The system allows calibration of the widely used 633 nm, 612 nm, and 543 nm HeNe laser systems. Also, frequency measurements of a polarization stabilized 1153 nm HeNe laser have been performed via frequency doubling and comparison with the dye system operating on the corresponding 576 nm lines. Studies of the shift sensitivities of the system at various wavelengths of interest are described for variation of iodine cell pressure, laser modulation amplitude, and optical saturation power. The dye system was also stabilized to hyperfine components associated with the 6-3 P(33) iodine transition and compared with a 633 nm iodine stabilized HeNe standard.     

Space interferometry application of laser frequency stabilization with molecular iodine

A number of planned space interferometry missions, including the Laser Interferometer Space Antenna (LISA) gravitational wave detector, require a laser system with high-frequency stability over long time scales. A 1064 nm wavelength nonplanar ring oscillator (NPRO) laser stabilized to a resonant transition in molecular iodine is suitable for these missions, providing high-frequency stability at an absolute reference frequency. The iodine stabilized laser also offers low sensitivity to temperature and alignment fluctuations and allows frequency tuning. We have evaluated the noise performance of a NPRO laser stabilized to iodine using frequency modulation spectroscopy and have found an Allan standard deviation of 10(-14) over 100 s. Simplified optical configurations and the radiation hardness of the frequency-doubling crystals have also been investigated.     

Frequency stabilization of a diode-pumped Nd:Yag laser at 532 nm to iodine by using third-harmonic technique

A compact frequency standard was constructed by stabilizing the frequency of a diode-pumped Nd:YAG laser to the Doppler-free spectrum of iodine at 532 nm. The performance of the laser and the stability and repeatability of the stabilization scheme were investigated. The dependence of the laser frequency on such parameters as pressure of the iodine cell, modulation amplitude, and pressure were also studied. The results show that by using standard third-harmonic locking technique stability and repeatability comparable to more elaborate iodine-stabilized Nd:YAG laser systems can be achieved in a portable, and relatively simple and inexpensive, setup.     

Intracavity iodine cell spectroscopy with an extended-cavity laserdiode around 633 nm

The purpose of the work described was to develop a tunable laser diode which is as easy to use as a He-Ne laser stabilized on iodine. The particularity of this experiment is the use of I₂ cell placed inside the extended cavity laser (ECL). The experimental set-up mounted takes the form of a lambdameter which gives the wavelength to one part in 10⁶, a Fabry-Perot (FP) interferometer for mode analysis and a beat-frequency measurement system. The FP interferometer has the particular feature of a second I₂ cell which makes it possible to detect the iodine transitions by simple visual inspection of an oscilloscope. Many transitions, some much more intense than the usual R(127)11-5 transition, are under study. We worked mainly on P(33) 6-3 since this is inside the range of our beat-frequency system. Results are promising: the free running relative frequency stability is about three parts in 10¹⁰ and the locked-laser relative frequency stability about three parts in 10¹¹ after 80 s. This is already good enough for use as a wavelength standard for length and for interferometric measurement     

532 nm Nd:YVO4/KTP激光器的I2分子吸收谱线的观测及频率稳定的研究

激光二极管抽运的固体激光器可用于光学计量,长度测量,相干光通信,激光雷达等方面,高精度应用要求激光器的频率稳定。碘分子在５３２ｎｍ附近在上百条强的吸收谱线,采用单频Ｎｄ;ＹＶＯ４／ＫＴＰ激光对碘的一些吸收谱线作了观测,并进行了激光频率稳定的研究,这些吸收谱线是１９９７年９月国际米定义咨询委员会推荐作为频标的９组５３２ｎｍ碘吸收谱线之外的新的参考谱线。     

Determination of iodine in oyster tissue by isotope dilution laser resonance ionization mass spectrometry

The technique of laser resonance ionization mass spectrometry has been combined with isotope dilution analysis to determine iodine in oyster tissue. The long-lived radioisotope, 129I, was used to spike the samples. Samples were equilibrated with the 129I, wet ashed under controlled conditions, and iodine separated by coprecipitation with silver chloride. The analyte was dried as silver ammonium iodide upon a tantalum filament from which iodine was thermally desorbed in the resonance ionization mass spectrometry instrument. A single-color, two-photon resonant plus one-photon ionization scheme was used to form positive iodine ions. Long-lived iodine signals were achieved from 100 ng of iodine. The precision of 127I/129I measurement has been evaluated by replicate determinations of the spike, the spike calibration samples, and the oyster tissue samples and was 1.0%. Measurement precision among samples was 1.9% for the spike calibration and 1.4% for the oyster tissue. The concentration of iodine determined in SRM 1566a, Oyster Tissue, was 4.44 micrograms/g with an estimate of the overall uncertainty for the analysis of +/- 0.12 microgram/g.     

Oxidation of Steel Samples in Air Under the Action of a Photodissociative Iodine Laser

Abstract

We report experimental data on the oxidation of steel samples in air by laser irradiation using pulses of different duration generated by a photodissociative iodine laser source. The results indicate an enhancement of the oxidation process under the action of laser radiation as compared with conventional oxidation techniques.     

Frequency stabilization of internal-mirror He-Ne lasers by air cooling

Instead of the traditional heating method, the cavity length of an internal-mirror He-Ne laser is controlled by air cooling which is implemented by a mini cooling fan. The responsive property of the cooling fan and the thermal expansion of the internal-mirror laser tube are investigated. According to these investigations, a controlling system is designed to drive the cooling fan controlling the cavity length of the laser. Then the frequency is stabilized by comparing the light intensities of two operating longitudinal modes. The results of beating with an iodine stabilized He-Ne laser show that a relative uncertainty (Δf/f-) of 4.3×10^-9 in 5 months, a frequency fluctuation of <1.4 MHz, and an Allan deviation of 6×10^-11 (τ=10,000 s) in 20?h are obtained.     

Production of Atomic Iodine by Decomposition of Methyl Iodide by the Products of a Glow Discharge Plasma in a Flow of Oxygen

The concentration of atomic iodine is measured by decomposing methyl iodide by the afterglow products of a dc glow discharge in a vortex flow of oxygen at pressures from 6 to 24 torr, at a flow rate of 4.2 mmol/s, currents of up to 500 mA, and a discharge power of up to 370 W. The experimental results are interpreted using the kinetic model developed by the authors, which includes the reactions of atomic oxygen with methyl iodide and the reactions between the resulting products. The produced concentrations of atomic iodine of up to 1.3 × 10¹⁵ cm^–3 are sufficient for use in the active medium of an oxygen-iodine laser.     

633nm He—Ne碘稳频激光波长的国际比对

１９９７年７月,在北京中国计量科学研究院进行了由国际计量局组织的碘稳频６３３ｎｍＨｅ－Ｎｅ激光波长基准的多边国际比对,进行了频率稳定度、频差及相应的压力位移、功率位移和调制位移测量实验。测量工作以ＢＩＰＭＰ３激光器为参考,最后给出以ＢＩＰＭ４激光器为基准的最终测量结果。     

Iodine-stabilized extended cavity diode laser at λ=633 nm

An extended cavity diode laser at 633 nm has been frequency stabilized to I₂-Doppler-free absorption signals of the P(33)6-3 transition using a third-harmonic detection technique. The frequency was measured by the beat-frequency technique with an iodine-stabilized He-Ne laser as reference. A minimum value for the two-probe relative standard uncertainty of 1× 10^-11 (5 kHz) is reached after 100 s. We also report measurements of the hyperfine splittings of the P(33)6-3 transition and laser frequency dependence on modulation amplitude and iodine pressure     

External photoacoustic detection of a trace vapor inside a multimode laser.

We combine highly sensitive intracavity absorption spectroscopy in a multimode laser with external photoacoustic detection, providing high detectivity. Photoacoustic measurements of the intracavity iodine concentration in a Rhodamine 6G laser are compared with simultaneous spectral recordings. They demonstrate slightly improved overall sensitivity and a greatly enhanced dynamic range of 5 orders of magnitude that may be shifted along the absolute scale of absorber density.     

频率调制多普勒全场测速实验系统测试

频率调制多普勒全场测速技术是一种基于分子滤波和多普勒频移现象的流场速度测量方法,在高速、超高速及大尺度风洞流场测量方面潜力巨大.我们设计开发了采用CCD相机作为接收探头的FM-DGV实验系统,该系统主要包括激光器、片光光学系统、碘分子滤波器、图像采集相机、频率监测单元等.基于该系统进行了谐波幅值比和转盘线速度测试实验.实验结果表明,该实验系统工作正常,速度测量误差最大值小于2m/s.     

Absolute frequency of the molecular iodine transition R(56)32-0near 532 nm

The absolute frequency of the hyperfine component a₁₀ in the transition R(56)32-0 of iodine has been measured using the D₂ line in Rb at 780 mm and an iodine-stabilized 633-nm He-Ne laser as references. This measurement provides a secondary frequency standard within the tuning range of a doubled Nd:YAG laser. The measured frequency of the a₁₀ component is 563 260 223.480 MHz ±70 kHz     

Experimental study on an all gas-phase iodine laser using microwave discharge of Cl2/He as a Cl atoms source

Microwave discharge of a Cl2/He mixture as a simple, clean and efficient Cl atom generator was used for an all gas-phase iodine laser study. Sufficient NCl(a1Delta) was produced through the reaction of HN3+2Cl-->NCl(a1Delta)+HCl+N2. The energy transfer reaction of I(2P3/2)+NCl(a1Delta)-->I(2P1/2)+NCl(X3Sigma) was observed. A population inversion was observed directly by using a 1315 nm tunable diode laser by scanning the entire line shape of the (3,4) hyperfine transition of iodine, and a small signal gain of 5x10(-5) cm-1 was obtained.     

Amplitude noise and linewidth reduction of an Ar+ laser

Frequency modulation spectroscopy is used to frequency stabilize an Ar⁺ laser at 515 nm with respect to a commercial passive cavity. Two transducers, a slow and a fast one, are used. The fast transducer is also used to perform amplitude stabilization of a laser beam. Measured amplitude and frequency spectral noise densities are reported. A simplified scheme of the circuitry used to reduce amplitude noise is shown. Noise characteristics of the realized system are adequate to perform spectroscopy of hyperfine-structure transitions of molecular iodine     

Frequency shifts of iodine stabilized He-Ne lasers at higherharmonic order stabilization

The frequency shifts of an ¹²⁷I₂ stabilized He-Ne laser at 633 nm have been measured at the third, fifth, and seventh harmonic stabilization using a digital signal processing lock-in amplifier. The observed frequency shifts confirmed the previous theoretical prediction that the laser frequency depends on the harmonic order of stabilization. The lower effects of modulation amplitude shift, power shift, and iodine pressure shift at the fifth harmonic stabilization indicate a potential improvement of the frequency reproducibility of the laser standard. A model is suggested to describe the power shifts of the laser. The mechanism explains the lower power shift of some lasers when they are operated at relatively high intracavity power     

Resonances of subnatural line width in iodine vapor driven by apolychromatic laser light field atλ=515 nm: a proposal

An initial study of the characteristics of sub-natural line width resonances in iodine elicited by polychromatic laser light has been made. Results of theoretical calculations are presented. Under proper experimental conditions, super-narrow resonances with high contrast ran be expected     

Mode-matching Techniques as an Aid to Laser Cavity Alignment

Improvement of the alignment accuracy of an experimental, curved mirror, laser cavity by mode matching of the alignment laser beam to the experimental cavity parameters is discussed. It is shown that the use of a two-lens telescope, giving beam magnification, allows the mode-matched condition to be readily obtained for a wide variety of cavity configurations, and that a particular matching condition optimizes the mirror alignment accuracy, giving equal alignment sensitivity for each mirror of the experimental cavity. The mode-matching procedure avoids the need for large distances to provide high angular sensitivity, and compact alignment systems, suitable for building in to experimental lasers are readily designed. As an example, the alignment of an atomic iodine laser is discussed.     

Experimental investigation of an unstable ring resonator with 90-deg beam rotation for a chemical oxygen iodine laser

We report the experimental results of an unstable ring resonator with 90-deg beam rotation for a kilowatt class chemical oxygen iodine laser (COIL). The distributions of near-field phase and far-field intensity were measured. A beam quality of 1.6 was achieved when the COIL average output power was approximately 5 kW.