Methane stabilizer laser

K.M. Evenson, J.S. Wells, F.R. Petersen, B.L. Danielson, G.W. Day, R.L. Barger, J.L. Hall Speed of light from direct frequency and wavelength measurements of the methane-stabilized laser. Phys. Rev. Lett. 29, 1346 (1972)... 

As shown in Fig. 7 we compared the frequency of the cesium Di line at 895 nm with the 4th harmonic of the methane stabilized He-Ne laser operating at 3.4 pm (/ = 88 THz). The laser that creates the frequency comb, the fourth harmonic generation and the HeNe laser are identical with the systems shown in Fig. 4. However, the HeNe laser was stabilized to a methane transition in this experiment and was used as a frequency reference instead of the Cs fountain clock. The frequency of this laser has been calibrated at the Physikalisch Technische Bundesanstalt Braunschweig/Germany (PTB) and in our own laboratory [51] to within a few parts in 1013. 

Fig. 3. Set-up of the frequency chain used to measure the absolute frequency of the two iodine spectrometers. The chain links the 532 nm radiation of the frequency doubled Nd YAG lasers (563 THz) to a methane-stabilized He-Ne laser at 3.39 /rm (88 THz). The two input frequencies of the frequency interval divider stage at 852 nm and 946 nm determine the frequency of the NdtYAG lasers at 1064 nm. The input frequencies are phase-coherently linked to the methane-stabilized He-Ne laser at 3.39 /xm by use of a frequency comb generated with a Kerr-lens mode-locked femtosecond laser...

One interesting reference standard may be the methane stabilized helium neon laser at 3.39 pm. Its infrared frequency can be compared directly with the microwave cesium frequency standard with the help of a relatively short frequency chain [32], An accuracy of 1 part in 1012 or better appears feasible for a transportable secondary standard. 

One way an optical standard could be provided is by harmonic multiplication of a microwave frequency standard in a synthesis chain. By use of this technique, a laser at 88 THz (3.39 pm) has been made phase coherent with a microwave oscillator. - The best optical frequency standards may be made by locking a local oscillator (laser) to an atomic or molecular resonance line. State-of-the-art accuracies are characterized by measurements on methane stabilized He-Ne lasers in which reproducibilities in the 10— -- range have... 

Here, the unknown laser frequency is compared (via heterodyne methods) to a harmonic of some well known reference line such as the methane stabilized He-Ne laser at 3.39 pm.- -... 

H. Hellwig, H.E. Bell, P. Kartaschoff, J.C. Bergquist Frequency stability of methane-stabilized He-Ne-lasers. J. Appl. Phys. 43, 450... 

Fluorescence Lifetimes. Fluorescence lifetimes were determined by the phase shift method, utilizing a previously-described phase fluorimeter. The emission from an argon laser was frequency doubled to provide a 257 nm band for excitation. Fluorescence lifetimes of anisole and polymer 1 in dichloro-methane solution were 2.2 and 1.4 nsec, respectively. Fluorescence lifetimes of polymer films decreased monotonically with increasing DHB concentration from 1.8 (0) to 0.7 nsec (9.2 x 10 3 MDHB). Since fluorescence lifetimes (in contrast to fluorescence intensities) are unaffected by absorption effects of the stabilizer, these results provide direct evidence in support of the intensity measurements for RET from polymer to stabilizer. 

The burner of Case 1 uses a swirled injector (Fig. 9.1) where swirl is produced by tangential injection downstream of a plenum. A central hub contributes to flame stabilization. In the experiment methane is injected through holes located in the swirler but mixing is fast so that perfect premixing is assumed for computations. Experiments include LDV (Laser Doppler Velocimetry) measurements for the cold flow as well as a study of various combustion regimes. The dimensions of the combustion chamber are 86 mm X 86 mm x 110 mm. 

Acetylene and methane can be detected in remote locations using diode lasers coupled with optical fibres Environmental measurements of acetylene are possible based on the overtone transition at 2 789 nm, using a stabilized AlGaAs diode laser, operating in an external optical cavity configuration. The detection limit is 0.2ppm/km for acetylene... 

A.S. Rine High-resolution methane U3-band spectra using a stabilized tunable difference-frequency laser system. J. Opt. Soc. Am. 66, 97 (1976) ... 

S.N. Bagayev, V.R Chebotajev Frequency stability and reproducibility at the 3.39 nm He-Ne laser stabilized on the methane line. Appl. Phys. 7,71 (1975)... 

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