Coherent transient amplification in inhomogeneously broadened rubidium atoms by diode-laser frequency switching.
TL;DR: Observation of coherent transient amplification that is due to free-induction decay and optical nutation in inhomogeneously broadened rubidium atoms by a sudden switch of diode-laser frequency is reported.
Abstract: We report observation of coherent transient amplification that is due to free-induction decay and optical nutation in inhomogeneously broadened rubidium atoms by a sudden switch of diode-laser frequency. An amplification coefficient of 2.2 × 10−2 cm−1 is observed when the diode-laser frequency, initially tuned to the blue side of the Doppler-broadened absorption profile, is switched to be out of resonance by application of a step-function pulsed injection current. The transition from free-induction decay to optical nutation is observed and discussed.
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TL;DR: The LTRS system combines optical trapping and near-infrared Raman spectroscopy for manipulation and identification of single biological cells in solution and may provide a valuable tool for the study of fundamental cellular processes and the diagnosis of cellular disorders.
Abstract: We report on the development and testing of a compact laser tweezers Raman spectroscopy (LTRS) system. The system combines optical trapping and near-infrared Raman spectroscopy for manipulation and identification of single biological cells in solution. A low-power diode laser at 785 nm was used for both trapping and excitation for Raman spectroscopy of the suspended microscopic particles. The design of the LTRS system provides high sensitivity and permits real-time spectroscopic measurements of the biological sample. The system was calibrated by use of polystyrene microbeads and tested on living blood cells and on both living and dead yeast cells. As expected, different images and Raman spectra were observed for the different cells. The LTRS system may provide a valuable tool for the study of fundamental cellular processes and the diagnosis of cellular disorders.
311 citations
TL;DR: In this article, a low-pressure sample of ethylene, within a multiple pass absorption cell, is subjected to radiation from a repetitively pulsed 10.25 micron quantum-cascade laser.
Abstract: Rapid passage signals exhibiting saturation effects have been observed when a low-pressure sample of ethylene, within a multiple pass absorption cell, is subjected to radiation from a repetitively pulsed 10.25 micron quantum-cascade laser. Within each pulse the laser frequency sweeps 36 GHz from high to low frequency in a time of 140 ns. At the low gas pressures, less than 20 mTorr, in the absorption cell the sweep rate through a Doppler-broadened absorption line (ca. 0.5 ns), is much faster than the collisional relaxation time of the ethylene and this leads to rapid passage effects. Examples are given of the complex rapid passage signals observed in pure and nitrogen broadened spectra. The rapid passage effects, which lead to the variety of the observed signals, have been modelled by numerical solution of the coupled Maxwell–Bloch equations for four sets of two-level systems.
39 citations
TL;DR: In this paper, an enhanced four-wave mixing (FWM) based on atomic coherence in a Pr3+:Y2SiO5 crystal was demonstrated, by employing coherent population return and fractional stimulated Raman adiabatic passage to prepare maximum atomic coherency in the crystal, an efficient FWM signal was generated.
Abstract: We experimentally demonstrate an enhanced four-wave mixing (FWM) based on atomic coherence in a Pr3+:Y2SiO5 crystal. By employing coherent population return and fractional stimulated Raman adiabatic passage to prepare maximum atomic coherence in the crystal, an efficient FWM signal can be generated. By measuring the generated FWM signal, the time-dependent atomic coherence is monitored. Such an enhanced FWM in solids may have practical applications in nonlinear optics and laser spectroscopy.
20 citations
TL;DR: Using a low power, rapid (nsec) pulse-modulated quantum cascade (QC) laser, collective coherent effects in the 5 μm spectrum of nitric oxide have been demonstrated by the observation of sub-Doppler hyperfine splitting and also Autler-Townes splitting of Doppler broadened lines.
Abstract: Using a low power, rapid (nsec) pulse-modulated quantum cascade (QC) laser, collective coherent effects in the 5 μm spectrum of nitric oxide have been demonstrated by the observation of sub-Doppler hyperfine splitting and also Autler-Townes splitting of Doppler broadened lines. For nitrous oxide, experiments and model calculations have demonstrated that two main effects occur with pulse-modulated (chirped) quantum cascade lasers: free induction decay signals, and signals induced by rapid passage during the laser chirp. In the open shell molecule, NO, in which both Λ-doubling splitting and hyperfine structure occur, laser field-induced coupling between the hyperfine levels of the two Λ-doublet components can induce a large ac Stark effect. This may be observed as sub-Doppler structure, field-induced splittings, or Autler-Townes splitting of a Doppler broadened line. These represent an extension of the types of behaviour observed in the closed shell molecule nitrous oxide, using the same apparatus, when probed with an 8 μm QC laser.
16 citations
TL;DR: This work measured FID's in molecular iodine by frequency switching an extended-cavity diode laser with a small current modulation to provide valuable information on the Doppler-free linewidths for frequency-standard applications.
Abstract: The free-induction decay (FID) technique combined with broadly tunable lasers offers a convenient way to survey molecular dephasing times. We measured FID's in molecular iodine by frequency switching an extended-cavity diode laser with a small current modulation. These decay times provide valuable information on the Doppler-free linewidths for frequency-standard applications.
16 citations
References
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Book•
01 Jan 1982
TL;DR: In this paper, the authors present a book aimed at teaching the novice researcher enough laser spectroscopy to enable him to contribute to current laboratory projects, which contains problem sets, new materials on signal-to-noise ratio, resonant ionization spectrograms, and dynamic grating techniques.
Abstract: Aimed at teaching the novice researcher enough laser spectroscopy to enable him to contribute to current laboratory projects. Chapters contain problem sets, new materials on signal-to-noise ratio, resonant ionization spectroscopy, dynamic grating techniques. Annotation copyright Book News, Inc. Por
544 citations
TL;DR: In this paper, the frequency modulation characteristics of three different AlGaAs lasers, a channeled-substrate planar (CSP), a buried-heterostructure (BH) and a transverse-junction-stripe (TJS) laser, were studied theoretically and experimentally.
Abstract: Direct frequency modulation characteristics in three different AlGaAs lasers-a channeled-substrate planar (CSP) laser, a buried-heterostructure (BH) laser, and a transverse-junction-stripe (TJS) laserare studied theoretically and experimentally. Experimental FM responses are measured by using the Fabry-Perot interferometer and birefringent optical filters in the 0-5.2 GHz modulation frequency region. Experimental FM response dependences on modulation frequency, dc bias level, and stripe structure are successfully explained by the theoretical analyses considering both the carrier density modulation effect and the temperature change effect. FM response in the low modulation frequency regin from 0 to 10 MHz, gradually decreasing with the modulation frequency, stems from the thermal effect. FM response in the high modulation frequency region from 10 MHz to 5.2 GHz is caused by the carrier effect. A flat FM response of several hundred MHz per 1 mA is observed in the CSP and TJS lasers, but a V-shaped FM response is obtained in the BH laser. Resonance peak due to relaxation oscillation and cutoff characteristics are observed in several gigahertz regions. Weak lateral mode confinement, strong vertical mode confinement, carrier injection outside the effective core region, and p-side down mounts are effective ways to achieve a flat and efficient FM response with a small spurious intensity modulation.
438 citations
IBM1
TL;DR: Theoretical computations of the nutation effect agree with observation, and echo characteristics closely follow predictions of existing theories as mentioned in this paper, and it is shown that echo relaxes primarily by rotational energy transfer.
Abstract: Photon echo and optical nutation have been easily observed in ${\mathrm{C}}^{13}$${\mathrm{H}}_{3}$F and N${\mathrm{H}}_{2}$D by applying Stark pulses which shift the molecular levels into resonance with cw laser radiation. Numerical computations of the nutation effect agree with observation, and echo characteristics closely follow predictions of existing theories. The $T_{2}^{}{}_{}{}^{\ensuremath{'}}$ pressure dependence, from infrared-echo measurements, indicates that ${\mathrm{C}}^{13}$${\mathrm{H}}_{3}$F relaxes primarily by rotational energy transfer.
214 citations
TL;DR: Atomic coherence effects within the sodium D line are shown to lead to the suppression of optical pumping, to the switching of light on and off when the coherenceeffects are turned on and on, and especially to lasing without inversion.
Abstract: Atomic coherence effects within the sodium ${\mathit{D}}_{1}$ line are shown to lead to the suppression of optical pumping, to the switching of light on and off when the coherence effects are turned on and off, and especially to lasing without inversion
174 citations
TL;DR: A phenomenon observed in a simple experiment with a diode laser is found to be a basis for powerful spectroscopy and high-resolution spectra in a wide ratio-frequency range are observed simultaneously by frequency analyzing the intensity fluctuation of the light transmitted through a sample cell.
Abstract: A phenomenon observed in a simple experiment with a diode laser is found to be a basis for powerful spectroscopy. In this spectroscopy, the laser frequency is neither scanned nor modulated. High-resolution spectra in a wide ratio-frequency range, such as Zeeman and hyperfine spectra in both of the ground and the excited states, are observed simultaneously by frequency analyzing the intensity fluctuation of the light transmitted through a sample cell. Demonstrating experiments are carried out with respect to the ${\mathit{D}}_{1}$ and ${\mathit{D}}_{2}$ lines of Cs and Rb atoms.
92 citations