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1.
2.
We investigate the coherent population trapping effect occurring between the Zeeman sublevels of a given hyperfine state of Cs when excited by a single-mode diode laser, which is frequency modulated in the kHz–MHz range. In the presence of a dc magnetic field, simultaneous excitation of pairs of ground-state magnetic sublevels to common excited magnetic sublevels is performed. As a result, coherent population trapping resonance is detected at only a given modulation frequency, whose value gives a measure of the magnetic field. The parameters of the resonances are measured in order to determine the ultimate accuracy of the magnetic field measurement. Received: 6 December 2002 / Revised version: 24 February 2003 / Published online: 2 June 2003 RID="*" ID="*"Corresponding author. Fax: +39-0577/23-4689, E-mail: biancalana@unisi.it  相似文献   

3.
The laser-induced line-narrowing effect, discovered more than thirty years ago, can also be applied to recent studies in high resolution spectroscopy based on electromagnetically induced transparency. In this paper we first present a general form of the transmission width of electromagnetically induced transparency in a homogeneously broadened medium. We then analyze a Doppler broadened medium by using a lorentzian function as the atomic velocity distribution. The dependence of the transmission linewidth on the driving field intensity is discussed and compared to the laser-induced line-narrowing effect. This dependence can be characterized by a parameter which can be regarded as “the degree of optical pumping.” Received: 17 December 2001 / Published online: 15 January 2003 RID="*" ID="*"Corresponding author. E-mail: hwang.Lee@jpl.nasa.gov RID="**" ID="**"Present address: Jet Propulsion Laboratory, MS 126-347, California Institute of Technology, Pasadena, CA 91109, USA  相似文献   

4.
We report the observation of bichromatic coherent population trapping under the transition ^87 RbFg = 1 → Fc = 0 with two linearly polarized laser beams by means of a Hanle effect configuration. The mechanism behind this effect is identified, and numerical solutions for the pump rates equations are presented.  相似文献   

5.
Cavity-enhanced absorption spectroscopy is explained in terms of the transmission function of a rapidly swept interferometer, and the integrated transmission is shown to be proportional to the cavity ringdown time. The technique is demonstrated on the b1Σg +-X3Σg -  (1,0) band in molecular oxygen at 687 nm using a tunable diode laser and a relative-ly high-Q optical cavity (finesse ≈4000). A detection limit of 3×10-8 cm-1 s1/2 is achieved for a 0.8 cm-1 scanning range. Received: 24 June 2002 / Revised version: 5 August 2002 / Published online: 15 November 2002 RID="*" ID="*"Corresponding author. Fax: +44-1865/275410, E-mail: peverall@physchem.ox.ac.uk  相似文献   

6.
We have studied the dispersion and absorption line shapes of coherent population trapping resonances (dark resonances) in thermal cesium vapor. Outside the time-of-flight regime the line shapes can be described by a simple phenomenological model: a sum of a dispersive and an absorptive Lorentzian of identical width and position, whose relative weights depend on the detuning of the laser frequencies from the optical resonance. This functional form can be derived from a theoretical model for the full multilevel structure of an alkali atom. The analytical expressions for the parameters of the line shape model show the same behavior as the experimental data. Received: 4 October 2002 / Revised version: 30 October 2002 / Published online: 8 January 2003 RID="*" ID="*"Corresponding author. Fax: +41-26/300-9631, E-mail: robert.wynands@unifr.ch  相似文献   

7.
We measure the properties of coherent population trapping (CPT) resonances in Cs vapor cells as a function of temperature. We expected the CPT signal to increase with higher vapor density, but instead the signal fades away above a certain density. Two possible density-dependent explanations are discussed: spin-exchange collisions, which are found to give no relevant contribution at the temperatures considered here, and increased absorption due to the optical thickness of the vapor. The dependence of the dark-line resonance amplitude as a function of cell temperature can be well represented by a simple model based on the optical thickness of the vapor as a function of temperature. Received: 30 November 2001 / Published online: 7 February 2002  相似文献   

8.
The lasing properties of organic compounds in a polymethylmethacrylate matrix radiating in the blue-green (paraterphenyle and coumarine derivatives) and red (phodamine and phenalemine derivatives) regions of the spectrum pumped by an XeCl laser are studied. The lasing efficiency and photostability of the solid-state active media are compared with corresponding characteristics of the same liquid active media. Received: 14 March 2001 / Published online: 7 June 2001  相似文献   

9.
\valunit{8}{mW} ( corrected for the output mirror reflection) of the cw coherent blue light around by frequency doubling of only from a diode laser. With IR power of we reach the doubling efficiency of . The overall conversion efficiency from the electrical power into the blue light is . By the way of careful analysis of the Blue Light Induced IR Absorption (BLIIRA) in the potassium niobate based external doubling cavity we obtain good agreement with the theoretical conversion efficiency. Received: 29 November 1996  相似文献   

10.
The atomic density, the buffer gas pressure, and the voltage dependence of the 510.6 nm laser line shape and its temporal evolution emitted from a Cu/CuBr vapor laser are measured. It is found that the monochromaticity of these laser lines can be improved greatly at a relative high buffer gas pressure. The temporal evolution of the line shape offers a stereoscopic view of a laser pulse. The sequence of appearance of the peaks of the line shape is governed by the intensity of the hyperfine component of the copper line.  相似文献   

11.
Measurements of oxygen concentration at high pressures (to 10.9 bar) were made using diode-laser absorption of oxygen A-band transitions near 760 nm. The wide current-tuning frequency range (>30 cm-1) of vertical cavity surface-emitting lasers (VCSELs) was exploited to enable the first scanned-wavelength demonstration of diode-laser absorption at high pressures; this strategy is more robust than fixed-wavelength strategies, particularly in hostile environments. The wide tuning range and rapid frequency response of the current tuning were further exploited to demonstrate wavelength-modulation absorption spectroscopy in a high-pressure environment. The minimum detectable absorbance demonstrated, ∼1×10-4, corresponds to ∼800 ppm-m oxygen detectivity at room temperature and is limited by etalon noise. The rapid- and wide-frequency tunability of VCSELs should significantly expand the application domain of absorption-based sensors limited in the past by the small current-tuning frequency range (typically <2 cm-1) of conventional edge-emitting diode lasers. Received: 26 July 2000 / Revised version: 2 January 2001 / Published online: 20 April 2001  相似文献   

12.
An atomic clock system based on coherent population trapping (CPT) resonance in 85Rb is reported, while most past works about the CPT clock are in ST Rb. A new modulation method (full-hyperfine-frequency-splitting modulation) is presented to reduce the effect of light shift to improve the frequency stability of the CPT clock in SSRb. The experimental results show that the short-term frequency stability of the CPT clock in SSRb is in the order of 10^-10/s and the long-term frequency stability can achieve 1.5 × 10^-11/80000s, which performs as well as 87 Rb in CPT resonance. This very good frequency stability performance associated with the low-cost and low-power properties of SSRb indicates that an atomic clock based on CPT in SSRb should be a promising candidate for making the chip scale atomic clock.  相似文献   

13.
We have studied atomic absorption in an argon discharge by wavelength-modulation spectroscopy with a frequency-doubled diode laser. The tunable wavelength-modulated radiation at 430 nm was generated by frequency doubling a current-modulated 860-nm diode laser in a KNbO3 crystal. 2f-, 4f- and 6f-harmonic spectra as a function of diode laser modulation depth were measured on a Doppler-broadened sample of excited argon atoms produced in a capacitively coupled plasma chamber. Characterisation of the harmonic signals was accomplished. Minimum detectable absorbances of 7.7×10-5 and 1.9×10-4 based on a 3σ criterion (σ being the standard deviation of the noise) were estimated for 2f- and 4f-harmonic detection of the frequency-doubled radiation with a time constant of 0.1 s. The concentrations of argon in the 1s4 state were found to be in the range of 3×108 to 1.2×1011 cm-3 for the experimental conditions studied. Received: 25 February 2002 / Revised version: 4 April 2002 / Published online: 14 May 2002  相似文献   

14.
We theoretically describe and experimentally investigate the spatio-spectral wave mixing of induced and spontaneous emission in large-area InGaAs-semiconductor laser amplifiers. The dynamic light-matter-coupling is described by a spatially resolved theory based on Maxwell–Bloch–Langevin equations, taking into account many-body-carrier interactions, energy transfer between the carrier and phonon systems and, in particular, the spatio-temporal interplay of stimulated and amplified spontaneous emission and the noise caused by spontaneous emission. Our numerical model reveals the fundamental physical processes which are responsible for the spectral power distribution of the amplified laser light and predicts the emission properties of high-power semiconductor laser amplifiers, such as emission spectra and input power–output power characteristics. Received:30October2002/Revisedversion:21November2002 / Published online: 12 February 2003 RID="*" ID="*"Corresponding author. Fax: +49-711/6862-349, E-mail: Edeltraud.Gehrig@dlr.de RID="**" ID="**"Also at: Institute of Physics, Tampere University of Technology, P.O. Box 692, FIN-33101, Tampere, Finland RID="***" ID="***"Present address: Heidelberger Druckmaschinen AG, Speyerer Strasse 6, 69115 Heidelberg, Germany RID="****" ID="****"Present address: Lightbit Corporation, 411 Clyde Avenue, Mountain View, CA 94043, USA  相似文献   

15.
A dual-beam laser absorption spectrometer with balanced detection for high sensitivity detection of oxygen via the A-band at 760 nm is described. The 2×2 vertical-cavity surface-emitting laser arrays used for this set-up are characterized by their wavelength tuning behavior with temperature and current, amplitude modulation, side-mode suppression ratio and polarization contrast. The spectrometer performance is determined over time periods of up to 10 h using the variation in the differential absorption between two beam paths. With the R11R11 line at STP, 670 μW laser power and 200 mm-long absorption cells, we realized an excellent linearity (R=0.9999) and over a 5-min interval a record sensitivity for VCSEL-based spectrometers of 35 ppmV, corresponding to an optical density (O.D.) of 7×10-7. For this specific set-up, this sensitivity is only a factor of 2.7 above the shot noise limit, giving us a normalized detection limit of 7.6 ppmV·m·. Over a 10-h interval we achieved a standard deviation of 65 ppmV. Received: 26 July 2000 / Revised version: 1 November 2000 / Published online: 6 December 2000  相似文献   

16.
Optical magnetometers have reached sensitivities that make them interesting candidates for the measurement of weak magnetic fields also outside physics laboratories. In order to overcome problems with stray magnetic fields a common solution with existing magnetometers is to operate a pair of them in a gradiometer configuration: one sensor measures the signal plus the stray fields, while the other one is mounted such that it is only influenced by the stray fields. In the difference signal the stray fields cancel. We have constructed such a gradiometer consisting of two sensors based on coherent population trapping (CPT) resonances in a thermal cesium vapor. Using a magnetic bias field the intrinsically scalar CPT magnetometer can be turned into a true vector magnetometer that is insensitive to magnetic fields perpendicular to a chosen measurement direction. We describe how to align and calibrate the gradiometer. Stray field suppression by more than two orders of magnitude has been achieved, limited by the sensitivity of the magnetometer. This makes possible the detection of picotesla flux density changes in a weakly shielded or even unshielded environment. Received: 3 April 2002 / Published online: 15 November 2002 RID="*" ID="*"New address: Département de Physique, Université de Fribourg, Chemin du Musée 3, 1700 Fribourg, Switzerland RID="**" ID="**"Corresponding author. Fax: +41-26/300-9631, E-mail: robert.wynands@unifr.ch  相似文献   

17.
We discuss a mechanism that allows the formation of nearly transform-limited soliton-like pulses in passively mode-locked optically pumped external-cavity surface-emitting semiconductor lasers. It involves the interplay of positive dispersion and the nonlinear index changes in gain medium and saturable absorber, while ordinary solitons are based on dispersion and the Kerr effect. The obtained quasi-soliton pulses share some of the properties of ordinary solitons (in particular, their stability and near bandwidth-limited nature), while other properties are different. In particular, the pulse duration scales with the square root of the cavity dispersion, and an excessive drift of the laser wavelength must be avoided by proper design. Received: 23 April 2002 / Published online: 25 September 2002 RID="*" ID="*"Corresponding author. Fax: +41-1/633-1059, E-mail: Paschotta@iqe.phys.ethz.ch  相似文献   

18.
19.
A miniature high-coherent diode laser was developed. Optical feedback from a high-Q microsphere resonator was used to narrow the spectrum of the laser, and a nearly half-pitch gradient-index lens served as a coupling element. As estimated from the variation in frequency-tuning range (chirp-reduction factor) the fast line width of the laser was reduced by more than three orders. It is remarkable that the system reveals stable single-mode operation at a relatively high feedback level. A tentative explanation is presented in terms of previously given models. Received: 8 July 2002 / Revised version: 9 March 2003 / Published online: 24 April 2003 RID="*" ID="*"Corresponding author. Fax: +7-095/334-0249, E-mail: vvv@okb.lpi.troitsk.ru  相似文献   

20.
Experimental results have demonstrated that the use of ejector-nozzle concepts can allow to achieve simultaneously high chemical efficiency and high pressure recovery in a chemical oxygen iodine laser. The estimated small-signal gain of the gain medium generated by these nozzle banks was from 0.5 to 0.8 %/cm. In laser experiments with all nozzle banks (NB-1–NB-5), Pitot pressures of the order of 80 Torr and Mach numbers of ∼2 in the cavity-mixing chamber have been achieved. The geometry of a given ejector-nozzle bank and gas-flow conditions affect the power extraction and chemical efficiency. The main factors for high efficiency and high power are small mixing scale, high area for the oxygen flow, dilution of chlorine by helium, and the arrangement of nozzles. A chemical efficiency of 25% at a power level of ∼900 W was obtained for NB-1 having the smallest mixing scale, parallel injection of all flows, and dilution of oxygen by helium. The highest power of ∼1.2 kW with a chemical efficiency of 19.5% and 160 W/cm2 of specific output power was achieved with NB-5 having the largest area for the oxygen flow and dilution of oxygen by helium. Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +7-8462/355-600, E-mail: nikolaev@fian.smr.ru  相似文献   

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