Absolute frequency measurements for hyperfine structure determination of the R(26) 62-0 transition at 501.7 nm in molecular iodine

The absolute frequencies of the hyperfine components of the R(26) 62-0 transition in molecular iodine at 501.7 nm are measured for the first time with an optical clockwork based on a femtosecond laser frequency comb generator. The set-up is composed of an Ar+ laser locked to a hyperfine component of the R(26) 62-0 transition detected in a continuously pumped low-pressure cell (0.33 Pa). The detected resonances show a linewidth of 45 kHz (half-width at half-maximum). The uncertainty of the frequency measurement is estimated to be 250 Hz

Correction of the distortion in frequency-modulation spectroscopy

A theoretical expression of the detected signal in frequency modulation spectroscopy with a residual amplitude modulation (RAM) is computed. The line shape distortion induced by the RAM is shown to be essentially suppressed for a proper choice of the modulation and detection parameters. The experimental tests are carried out in saturation spectroscopy of I2 at 514.5 nm. Experimental limitations are analysed

Frequency modulated laser beam with highly efficient intensity stabilisation

We analyse the limitation of the amplitude modulation rejection due to the spatial modulation of the output beam of an acousto-optic modulator used in an active laser beam stabilisation system when a frequency modulation of a few megahertz is applied to this modulator. We show how to overcome this problem, using a single mode optical fibre at the output of the modulator. A residual amplitude modulation of 10-5 is achieved

Absolute frequency measurement of the iodine-stabilized Ar+ laser at 514.6 nm using a femtosecond optical frequency comb.

The frequency of 127I2 hyperfine component a3 of the P(13) 43-0 transition at 514.6 nm has been measured with an optical clockwork based on a femtosecond laser frequency comb generator. The measured frequency at an iodine pressure of 0.12 Pa is 67.3(0.75) kHz higher than the value of 582490603.38(15) MHz, adopted by the CIPM in 2003 [T.J. Quinn, Metrologia 40, 103 (2003)] but is in a good agreement with the value measured by R.J. Jones et al [Appl. Phys. B74, 597 (2002)]. In our experiment we used H-maser reference frequency located at BNM-SYRTE Observatoire de Paris and transported to our laboratory by a 43 km optical fibre link

CW frequency doubling of 1029 nm radiation Using single pass bulk and waveguide PPLN crystals

Following various works on second harmonic process using periodically poled Lithium Niobate crystals (PPLN), we report on the performances comparison between commercial bulk and waveguide crystals at 1029 nm. We use a continuous wave (CW) amplified Yb doped single fibre laser delivering up to 500mW in single mode regime. In case of bulk crystal we generate 4 mW using 400 mW IR power. The use of waveguide crystal leads to an increase of the harmonic power up to 33mW with input IR power limited to 200mW. Nevertheless, this impressive efficiency was affected by the long term degradation of the non-linear waveguide crystal

Stabilisation de l'intensité d'un faisceau laser par un correcteur en bande étroite (application à une référence Ar+ /I2 à 501.7 nm)

On présente le développement, l'analyse et l'application d'un dispositif de stabilisation de l'intensité d'un faisceau laser dans une bande étroite de fréquence. La stabilité, la durée de convergence et la réjection du bruit d'intensité d'un faisceau sont analysés à partir d'un schéma équivalent à temps continu. Le dispositif est appliqué en spectroscopie de saturation à la réjection de la modulation d'amplitude parasite en spectroscopie FM et la stabilisation de l'intensité du faisceau sonde en transfert de modulation. Une nouvelle stabilisation de la fréquence d'un laser Ar+ sur une transition hyperfine de l'iode à 501,7 nm est proposée. La transition est détectée dans une cellule haute pression en transfert de modulation pour le moyen terme et dans une cellule basse pression en spectroscopie FM pour le long terme. On atteint une déviation d'Allan d'environ 10-13 pour une durée d'intégration de 1 s et 10-14 pour 500 s.We present the development, the analysis and the application of a device for stabilization of the laser beam intensity in a narrow frequency band. The stability, the convergence speed and the intensity noise rejection are analyzed from a continuous time model. The device is applied to saturation spectroscopy for rejection of the residual amplitude modulation in FM spectroscopy and for stabilization of the probe beam intensity in modulation transfer technique. A new frequency stabilization scheme of an Ar+ laser on a hyperfine transition of iodine at 501,7 nm is proposed. The transition is detected in a high pressure cell using the modulation transfer technique for the mean term stabilization and in a low pressure cell in FM spectroscopy for the long term stabilization. An Allan deviation of about 10-13 for 1 s integration time and 10-14 for 500 s is reached.PARIS13-BU Sciences (930792102) / SudocSudocFranceF

Effects of polarization modulation induced by electro-optic modulators in fiber-based setups

Using the Jones formalism, it is shown that electro-optic modulators used for phase modulation generate a modulation of the output polarization induced by the difference of phase modulation depth along the crystallographic axes of the modulator. We study two consequences of this polarization modulation in the fiber setups, limiting the performance of high sensitivity measurement devices. The first one is its partial conversion into a residual amplitude modulation (RAM) within any component presenting polarization dependent losses (PDL). The second one is a new effect that consists of the distortion of the signal detected at the output of a fiber cavity. The theoretical expressions of the detected signals are computed in each case

Efficient third harmonic generation of a CW-fibered 1.5 µm laser diode

International audienceWe report on frequency tripling of CW-Telecom laser diode using two cascaded PPLN ridge nonlinear crystals, both used in single-pass configuration. All optical components used for this development are fibered, leading to a very compact and easy to use optical setup. We have generated up to 290 mW optical power in the green range, from 800 mW only of infrared power around 1.54 µm. This result corresponds to an optical conversion efficiency P3ω/Pω > 36 %. To our knowledge, this is best value ever demonstrated up today for a CW-third harmonic generation in single-pass configuration. This frequency tripling experimental setup was tested over more than two years of continuous operation, without any interruption. The compactness and the reliability of our device make it very suitable as a transportable optical oscillator. In particular, it paves the way for embedded applications thanks to the high level of long term stability of the optical alignments

Limitations of the frequency stability transfer in the near infrared using a fiber-based ring cavity

We describe a fiber ring cavity for transferring frequency stability from a metrological optical reference at 1542 nm to tunable lasers covering a hundred nm around 1.55µm and show a stability transfer to the 10-15 level in relative value. The optical length of the ring is controlled by two actuators: a cylindric piezoelectric actuator (PZT) on which a portion of the fiber is coiled and glued for fast corrections (vibrations) acting on the length of the fiber and a Peltier module for slow corrections acting on its temperature. We characterize the stability transfer and analyze the limitations imposed by two critical effects in the setup: Brillouin backscattering and the polarization modulation generated by the electro-optic modulators used in the error signal detection scheme. We show that it is possible to reduce the impact of these limitations to a level below the detection threshold imposed by the servo noise. We also show that in the long term, the limitation to the stability transfer is a thermal sensitivity of-550 Hz/K/nm which could be reduced by active control of the ambient temperature