Showing papers on "Laser linewidth published in 1999"
TL;DR: In this paper, the authors reported a visible laser with a subhertz linewidth of 0.6 Hz for averaging times up to 32 s. The authors derived their stability from a well-isolated, high-finesse, Fabry-P\'erot cavity.
Abstract: We report a visible laser with a subhertz linewidth for use in precision spectroscopy and as a local oscillator for an optical frequency standard. The laser derives its stability from a well-isolated, high-finesse, Fabry-P\'erot cavity. For a 563 nm laser beam locked to our stable cavity, we measure a linewidth of 0.6 Hz for averaging times up to 32 s. The fractional frequency instability for the light locked to the cavity is typically $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$ at 1 s. Both the linewidth and fractional frequency instability are approximately an order of magnitude less than previously published results for stabilized lasers.
584 citations
TL;DR: In this paper, a self-assembling method was used to grow InAs quantum dots with size fluctuations of less than 4% on GaAs using the self-assembly method and the photoluminescence linewidth was reduced to 21 meV at room temperature.
Abstract: InAs quantum dots with size fluctuations of less than 4% were grown on GaAs using the self-assembling method. By covering the quantum dots with In0.2Ga0.8As or In0.2Al0.8As, strain in InAs dots can be partly reduced due to relaxation of lattice constraint in the growth direction. This results in low-energy emission (about 1.3 μm) from the quantum dots. The photoluminescence linewidth can be reduced to 21 meV at room temperature. This width is completely comparable to the theoretical limit of a band-to-band emission from a quantum well at room temperature. Because the dots can be uniformly covered by the strain reducing layers, factors that degrade size uniformity during coverage, such as compositional mixing or segregation, will be suppressed, allowing for an almost ideal buried quantum dot structure.
551 citations
TL;DR: In this paper, the authors developed a theory of the extrinsic contributions to the ferromagnetic resonance linewidth and frequency shift of ultrathin films by two magnon scattering by defects at surfaces and interfaces.
Abstract: We develop a theory of the extrinsic contributions to the ferromagnetic resonance linewidth and frequency shift of ultrathin films. The basic mechanism is two magnon scattering by defects at surfaces and interfaces. In the presence of dipolar couplings between spins in the film, one realizes short wavelength spin waves degenerate with the ferromagnetic resonance (FMR) mode, provided the magnetization is parallel to the film surfaces. Defects on the surface or interface thus scatter the FMR mode into such short wavelength spin waves, producing a dephasing contribution to the linewidth, and a frequency shift of the resonance field. The mechanism described here is inoperative when the magnetization is perpendicular to the film.
478 citations
TL;DR: In this article, the ground state gain is determined from cavity mode Fabry-Perot modulation for InAs quantum-dot laser emitting at 1.22 /spl mu/m.
Abstract: Amplified spontaneous emission measurements are investigated below threshold in InAs quantum-dot lasers emitting at 1.22 /spl mu/m. The dot layer of the laser was grown in a strained quantum well (QW) on a GaAs substrate. Ground state gain is determined from cavity mode Fabry-Perot modulation. As the injection current increases, the gain rises super-linearly while changes in the index of refraction decrease. Below the onset of gain saturation, the linewidth enhancement factor is as small as 0.1, which is significantly lower than that reported for QW lasers.
305 citations
TL;DR: In this paper, a blue vertical cavity surface-emitting laser was demonstrated at a wavelength of 399 nanometers under optical excitation and confirmed by a narrowing of the linewidth in the emission spectra from 0.8 nanometer below threshold to less than 0.1 nanometer above threshold.
Abstract: Lasing action has been demonstrated at blue wavelengths in vertical cavity surface-emitting lasers at room temperature. The microcavity was formed by sandwiching indium gallium nitride multiple quantum wells between nitride-based and oxide-based quarter-wave reflectors. Lasing action was observed at a wavelength of 399 nanometers under optical excitation and confirmed by a narrowing of the linewidth in the emission spectra from 0.8 nanometer below threshold to less than 0.1 nanometer (resolution limit) above threshold. The result suggests that practical blue vertical cavity surface-emitting lasers can be realized in gallium-nitride-based material systems.
243 citations
Abstract: Emission spectra of multimode lasers are very sen- sitive to spectrally selective extinction in their cavity. This phenomenon allows the quantitative measurement of absorp- tion. The sensitivity of measurements of intracavity absorp- tion grows with the laser pulse duration. The ultimate sen- sitivity obtained with a cw laser is set by various perturba- tions of the light coherence, such as quantum noise, Rayleigh scattering, four-wave mixing by population pulsations, and stimulated Brillouin scattering. It depends on the particular laser type used, and on its operative parameters, for example pump power, cavity loss, cavity length, and length of the gain medium. Nonlinear mode-coupling dominates the dy- namics of lasers that feature a thin gain medium, such as dye lasers, whereas Rayleigh scattering is more important in lasers with a long gain medium, such as doped fibre lasers, or the Ti:sapphire laser. The highest sensitivity so far has been obtained with a cw dye laser. It corresponds to 70 000 km effective length of the absorption path. The ultimate spec- tral resolution is determined by the spectral width of mode emission, which is 0: 7H zin this dye laser. High sensitiv- ity and high temporal and spectral resolution allow various practical applications of laser intracavity spectroscopy, such as measurements and simulations of atmospheric absorption, molecular and atomic spectroscopy, process control, isotope separation, study of free radicals and chemical reactions, combustion diagnostics, spectroscopy of excited states and nonlinear processes, measurements of gain and of spectrally narrow light emission. Intracavity absorption in single-mode lasers shows enhanced sensitivity as well, although not as high as in multimode lasers.
236 citations
TL;DR: Lasing of Fe:ZnSe is demonstrated, for the first time to the authors' knowledge, for temperatures ranging from 15 to 180 K, with an Er:YAG laser operating at 2.698mum as the pump source.
Abstract: Lasing of Fe:ZnSe is demonstrated, for the first time to the authors’ knowledge, for temperatures ranging from 15 to 180 K.?The output wavelength of the Fe:ZnSe laser was observed to tune with temperature from 3.98 µm at 15 K to 4.54 µm at 180 K.?With an Er:YAG laser operating at 2.698 µm as the pump source, a maximum energy per pulse of 12 µJ at 130 K was produced. Laser slope efficiencies of 3.2% at 19 K and 8.2% at 150 K were determined for an output coupling of 0.6%. A laser emission linewidth of 0.007 µm at 3.98 µm was measured at 15 K.?Absorption and emission spectra and emission lifetimes for Fe:ZnSe are also discussed.
209 citations
TL;DR: In this paper, the authors proposed the optical injection phase-lock loop (OIPLL) for homodyne OIPLL systems with DFB lasers of summed linewidth 36 MHz, loop propagation delay of 15 ns and injection ratio less than -30 dB.
Abstract: The requirement for narrow linewidth lasers or short-loop propagation delay makes the realization of optical phase-lock loops using semiconductor lasers difficult. Although optical injection locking can provide low phase error variance for wide linewidth lasers, the locking range is restricted by stability considerations. Theoretical and experimental results for a system which combines both techniques so as to overcome these limitations, the optical injection phase-lock loop (OIPLL), are reported. Phase error variance values as low as 0.006 rad/sup 2/ (500 MHz bandwidth) and locking ranges exceeding 26 GHz were achieved in homodyne OIPLL systems using DFB lasers of summed linewidth 36 MHz, loop propagation delay of 15 ns and injection ratio less than -30 dB. Phase error variance values as low as 0.003 rad/sup 2/ in a bandwidth of 100 MHz, a mean time to cycle slip of 3/spl times/10/sup 10/ s and SSB noise density of -94 dBc/Hz at 10 kHz offset were obtained for the same lasers in an heterodyne OIPLL configuration with loop propagation delay of 20 ns and injection ratio of -30 dB.
208 citations
TL;DR: The dynamics and bifurcations of a single-mode semiconductor laser with optical injection, modeled by three-dimensional rate equations, are presented, to the best knowledge, yet, of the dynamics of injected semiconductor lasers.
181 citations
TL;DR: In this article, the authors used a weakly absorbing gas such as C2H2 or C2HD placed inside an external high-finesse resonator to obtain an integrated absorption sensitivity of 5×10-13(1×10−14/cm) for the gas's weak near-IR molecular overtone transitions.
Abstract: The sensitivity of FM spectroscopy can be dramatically enhanced by location of the sample in a high-finesse cavity, for example, ∼5 orders of magnitude in this study. To avoid conversion of laser frequency noise into amplitude noise by the cavity, we choose the rf modulation frequency to match the cavity’s free spectral range. In this way small frequency fluctuations produce no additional noise, and a pure FM dispersion signal is recovered in transmission. We present a systematic study of the detection sensitivity, signal line shape and size, and slope at the central tuning. Experimentally, using a weakly absorbing gas such as C2H2 or C2HD placed inside an external high-finesse resonator, we obtained an integrated absorption sensitivity of 5×10-13(1×10-14/cm) for the gas’s weak near-IR molecular overtone transitions. As an interesting application, a Nd:YAG laser was well stabilized on the P(5) line of the C2HD(ν2+3ν3) band by this technique. The high attainable sensitivity permitted selection of slow molecules with low power and gas pressure to give a linewidth 13 times below the room-temperature transit-time limit.
169 citations
TL;DR: It was found that the Brillouin-loss signal intensity is linearly related to the duration of the pump pulse used to obtain the spectrum, and three distinct behaviors were observed in the spectral linewidth.
Abstract: The characterization of the Brillouin-loss spectrum of single-mode fibers with very short (<10-ns) pulses has been studied. It was found that the Brillouin-loss signal intensity is linearly related to the duration of the pump pulse used to obtain the spectrum. In contrast with the uniform trend of the signal, three distinct behaviors were observed in the spectral linewidth. At long pulse durations the linewidth was constant at approximately 40 MHz. Pulse durations of the order of the phonon lifetime resulted in a broader spectrum, reaching a maximum width of ~100 MHz at 5 ns. Reducing the pulse duration further resulted in a sudden narrowing of the Brillouin line.
TL;DR: In this article, the first fully packaged semiconductor laser optical phase-locked loop (OPLL) microwave photonic transmitter is presented, based on semiconductor lasers that are directly phase locked without the use of any other phase noise-reduction mechanisms.
Abstract: In this paper, we present the first fully packaged semiconductor laser optical phase-locked loop (OPLL) microwave photonic transmitter. The transmitter is based on semiconductor lasers that are directly phase locked without the use of any other phase noise-reduction mechanisms. In this transmitter, the lasers have a free-running summed linewidth of 6 MHz and the OPLL has a feedback bandwidth of 70 MHz. A state-of-the-art performance is obtained, with a total phase-error variance of 0.05 rad/sup 2/ (1-GHz bandwidth) and a carrier phase-error variance of 7/spl times/10/sup -4/ rad/sup 2/ in a 15-MHz bandwidth. Carriers are generated in the range of 7-14 GHz. The OPLL transmitter has been fully packaged for practical use in field trials. This is the first time this type of transmitter has been fabricated in a packaged state which is a significant advance on the route to practical application.
TL;DR: A quantum-cascade laser operating at a wavelength of 8.1 micrometers was used for high-sensitivity absorption spectroscopy of methane (CH4) and the content of 13CH4 and CH3D species in a CH4 sample was determined.
Abstract: A quantum-cascade laser operating at a wavelength of 81 micrometers was used for high-sensitivity absorption spectroscopy of methane (CH4) The laser frequency was continuously scanned with current over more than 3 cm-1, and absorption spectra of the CH4 nu 4 P branch were recorded The measured laser linewidth was 50 MHz A CH4 concentration of 156 parts in 10(6) ( ppm) in 50 Torr of air was measured in a 43-cm path length with +/- 05-ppm accuracy when the signal was averaged over 400 scans The minimum detectable absorption in such direct absorption measurements is estimated to be 11 x 10(-4) The content of 13CH4 and CH3D species in a CH4 sample was determined
TL;DR: In this article, a magneto-optic trap with 50 mW of frequency-doubled diode laser light at 423 nm was used to trap >107 Ca atoms in 20 ms.
Abstract: We report an optical frequency standard at 657 nm based on laser-cooled/trapped Ca atoms. The system consists of a novel, compact magneto-optic trap which uses 50 mW of frequency-doubled diode laser light at 423 nm and can trap >107 Ca atoms in 20 ms. High resolution spectroscopy on this atomic sample using the narrow 657 nm intercombination line resolves linewidths (FWHM) as narrow as 400 Hz, the natural linewidth of the transition. The spectroscopic signal-to-noise ratio is enhanced by an order of magnitude with the implementation of a “shelving" detection scheme on the 423 nm transition. Our present apparatus achieves a fractional frequency instability of in 1 s with a potential atom shot-noise-limited performance of and excellent prospects for high accuracy.
TL;DR: Frequency stabilization of mid-IR quantum cascade (QC) lasers to the kilohertz level has been accomplished by use of electronic servo techniques.
Abstract: Frequency stabilization of mid-IR quantum cascade (QC) lasers to the kilohertz level has been accomplished by use of electronic servo techniques. With this active feedback, an 8.5-microm QC distributed-feedback laser is locked to the side of a rovibrational resonance of nitrous oxide (N(2) O) at 1176.61cm (-1) . A stabilized frequency-noise spectral density of 42Hz/ radicalHz has been measured at 100 kHz; the calculated laser linewidth is 12 kHz.
TL;DR: A major advance in this method is the correction for the broadening produced by Zeeman modulation commonly used to obtain EPR signals; this allows experimenters much more freedom to optimize their experimental conditions for the best signal-to-noise ratio.
TL;DR: In this paper, the physical, chemical and optical properties of barium nitrate crystal are considered from the point of its application for development of solid state Raman lasers and shifters.
TL;DR: In this paper, the authors report on actively stabilized single-frequency operation of a vertical-external-cavity surface-emitting semiconductor laser (VECSEL).
Abstract: We report on actively stabilized single-frequency operation of a vertical-external-cavity surface-emitting semiconductor laser (VECSEL). The VECSEL was locked to a 300-MHz reference cavity allowing a relative frequency measurement that indicated a laser linewidth of 3 kHz. Coarse tuning over an 8.5-nm range was achieved, with fine tuning over 250 MHz. The laser produced up to 42 mW of output power in single-frequency operation.
TL;DR: The measurements indicate the possibility of achieving a spectral width of the signal peak that is transform limited rather than limited by the frequency modulation response of the laser, which permits the use of a narrow detection bandwidth.
Abstract: The performance of a frequency-modulated continuous-wave (FMCW) semiconductor laser radar has been examined. Frequency modulation (linear chirp) has been studied experimentally in detail. To create a linear frequency sweep, we modified the modulating function according to the measured frequency response of the laser, using an arbitrary function generator. The measurements indicate the possibility of achieving a spectral width of the signal peak that is transform limited rather than limited by the frequency modulation response of the laser, which permits the use of a narrow detection bandwidth. The narrow width results in a relatively high signal-to-noise ratio for low output power and thus also in relatively long-range and high-range accuracy. We have performed measurements of a diffuse target to determine the performance of a test laser radar system. The maximum range, range accuracy, and speed accuracy for a semiconductor laser with an output power of 10 mW and a linewidth of 400 kHz are presented. The influence of the laser’s output power and coherence length on the performance of a semiconductor-laser-based FMCW laser radar is discussed.
TL;DR: In this paper, the authors measured the relative intensity noise (RIN) for two diode lasers whose linewidths differ by more than 10−2 after the lasers have propagated through a resonant rubidium vapor.
Abstract: When laser light propagates through a resonant medium, the transmitted beam can exhibit excess intensity noise [amplitude modulation (AM)]. In a semiclassical description of the phenomenon, laser phase noise (PM) induces fluctuations in the medium's electric susceptibility, which in turn cause fluctuations in the transmitted intensity. The process provides an efficient means for PM-to-AM conversion, and intuition suggests that large linewidth lasers should exhibit much greater PM-to-AM conversion than narrow linewidth lasers. Here we measure the relative intensity noise (RIN) for two diode lasers whose linewidths $\ensuremath{\Delta}{\ensuremath{
u}}_{L}$ differ by more than ${10}^{2},$ after the lasers have propagated through a resonant rubidium vapor. Though the RIN of the narrow linewidth laser is only reduced by a factor of about 6 compared to the broad linewidth laser, our results are nonetheless consistent with numerical simulations of the PM-to-AM conversion process. In particular, both computation and analytical theory indicate that RIN is a nonlinear function of $\ensuremath{\Delta}{\ensuremath{
u}}_{L}.$ For single-mode laser linewidths less than the atomic dephasing rate, RIN increases like $\sqrt{\ensuremath{\Delta}{\ensuremath{
u}}_{L}},$ while for linewidths greater than the atomic dephasing rate RIN is a decreasing function of $\ensuremath{\Delta}{\ensuremath{
u}}_{L}.$
TL;DR: In this paper, the experimental realization of a silver gallium sulfide (AgGaS2) optical parametric oscillator (OPO) with a wide mid-IR tuning range was presented.
Abstract: This is the experimental realization of a silver gallium sulfide (AgGaS2) optical parametric oscillator (OPO) with a wide mid-IR tuning range. The singly resonant angle-tuned AgGaS2 type-II OPO was pumped by 1.06 μm pulses from a nanosecond Nd:YAG laser and yielded idler wave continuously tunable from 3.9 to 11.3 μm with a linewidth of 1 cm−1. The OPO threshold was 0.03 J/cm2 corresponding to sub-MW/cm2 pump intensity and sub-100 μJ pump energy. The slope and absolute quantum conversion efficiencies reached 41% and 22%, respectively.
TL;DR: In this paper, the authors demonstrated tunable, locked output from 9.5 to 17.1 GHz with a linewidth below the 1-kHz resolution limit of the measurement apparatus.
Abstract: Semiconductor lasers subjected to near-resonant external optical injection can exhibit strong oscillations of the output power due to a dynamic instability in the coupling of the gain medium to the circulating optical field. The oscillation frequency depends on the operating point of the injected laser and the strength and frequency offset of the injected optical signal. Adding a reference current modulation to the dc-bias current can induce the oscillation frequency of the optical power to become locked to the reference. Tunable, locked output from 9.5 to 17.1 GHz is demonstrated, with a linewidth below the 1-kHz resolution limit of the measurement apparatus.
TL;DR: Numerically analyze the coupling efficiency of a cw laser to a ringdown cavity in terms of changes in the scanning rate, the laser linewidth, and the mirror reflectivity, and demonstrate a new simple design for a CRDS system that can produce aCRDS signal with only a piezoelectric transducer (PZT).
Abstract: For the efficient operation of a cavity ringdown spectroscopy (CRDS) system utilized with a continuous-wave (cw) laser, we numerically analyze the coupling efficiency of a cw laser to a ringdown cavity in terms of changes in the scanning rate, the laser linewidth, and the mirror reflectivity. We also demonstrate a new simple design for a CRDS system that can produce a CRDS signal with only a piezoelectric transducer (PZT), without the acousto-optic modulator that is usually adopted to switch off the cw laser beam that enters the cavity. Furthermore, we investigate the feasibility of the cw CRDS technique with a fast-scanning PZT by recording a CRDS spectrum of acetylene overtones. The detection sensitivity that corresponds to the noise-equivalent absorption is found to be approximately 3 x 10(-9)/cm.
TL;DR: In this article, the growth of self-organized In0.4Ga0.6As quantum dots on Si substrates by molecular-beam epitaxy was reported, and the optical properties of the self-organised quantum dots were compared to quantum dots grown on GaAs.
Abstract: We report growth of self-organized In0.4Ga0.6As quantum dots on Si substrates by molecular-beam epitaxy. Low-temperature (17 K) photoluminescence spectra show that the optical properties of In0.4Ga0.6As quantum dots grown on Si are comparable to quantum dots grown on GaAs substrates. We also present preliminary characteristics of In0.4Ga0.6As quantum-dot lasers grown on Si substrates. Light versus current measurements at 80 K under pulsed bias conditions show that Ith=3.85 kA/cm2. The lasing spectral output has a peak emission wavelength of 1.013 μm and a linewidth (full width at half maximum) of ∼4 A at the threshold.
TL;DR: In this article, the analytical expression for the lasing threshold for whispering-gallery-mode microsphere lasers under the strong-coupling condition is obtained by solving a quasi-three-level quantized model.
Abstract: The analytical expression for the lasing threshold for whispering-gallery-mode microsphere lasers under the strong-coupling condition is obtained by solving a quasi-three-level quantized model. It explicitly displays the dependence of the lasing threshold on the cavity radius, the homogeneous linewidth, the quality factors and linewidths of the relevant cavity modes.
TL;DR: In this article, spontaneous emission from interwell intersubband transition from an electrically pumped multiple-quantum-well structure was observed, and the center frequency of the emission peak was at 2.57 THz and its full width at half maximum was 0.47 THz.
Abstract: Narrow-linewidth terahertz spontaneous emission resulting from interwell (or diagonal) intersubband transition from an electrically pumped multiple-quantum-well structure was observed. The center frequency of the emission peak is at 2.57 THz, and its full width at half maximum is 0.47 THz. The emission frequency is in good agreement with the calculated intersubband transition energy of 11.3 meV (corresponding to 2.7 THz) in a three-level system, which was designed to achieve population inversion between two radiative levels.
TL;DR: In this article, the anharmonic shift of the Raman frequency of the covalent semiconductors diamond and silicon are determined ab initio by combining density-functional perturbation theory with the frozen-phonon approach.
Abstract: Combining density-functional perturbation theory with the frozen-phonon approach, the anharmonic shift of the Raman frequency of the covalent semiconductors diamond and silicon are determined ab initio. The temperature dependence of the Raman frequency and the contribution of zero-point motion are calculated as well as the Raman linewidth. Corresponding results for germanium have been obtained with the assumption that the quartic anharmonic force constants may be approximated by those of silicon.
TL;DR: In this article, the authors present a theoretical model for the electrically pumped single-quantum-dot microsphere laser and analyze the steady state and dynamical properties of the optical field, such as output power, photon number fluctuation, and linewidth.
Abstract: We present a theoretical model for the electrically pumped single-quantum-dot microsphere laser. We solve the master equation of the system and analyze the steady state and dynamical properties of the optical field, such as output power, photon number fluctuation, and linewidth, for realistic experimental parameters. The laser threshold power is several orders of magnitude lower than is currently possible with semiconductor microlasers. A semiclassical approximation for the output power and laser linewidth is derived and compared to the exact solution. Electrical pumping together with Coulomb blockade effect allows for the realization of regular pumping in the system. We discuss the possibility for the generation of heralded single photons and of sub-Poissonian laser light. @S1050-2947~99!05506-7#
TL;DR: In this article, the authors derived the relation between the Petermann factor and the residues of poles of the scattering matrix, and investigated the statistical properties of the P factor for cavities in which the radiation is scattered chaotically.
Abstract: The quantum-limited linewidth of a laser cavity is enhanced above the Schawlow-Townes value by the Petermann factor K, due to the non-orthogonality of the cavity modes. We derive the relation between the Petermann factor and the residues of poles of the scattering matrix and investigate the statistical properties of the Petermann factor for cavities in which the radiation is scattered chaotically. For a single scattering channel we determine the complete probability distribution of K and find that the average Petermann factor $ $ depends non-analytically on the area of the opening, and greatly exceeds the most probable value. For an arbitrary number N of scattering channels we calculate $ $ as a function of the decay rate $\Gamma$ of the lasing mode. We find for $N\gg 1$ that for typical values of $\Gamma$ the average Petermann factor $ \propto \sqrt{N}\gg 1$ is parametrically larger than unity.
TL;DR: In this paper, the output of two grating-stabilized external-cavity diode lasers was injected into a semiconductor tapered amplifier in a master oscillator-power amplifier (MOPA) configuration.
Abstract: The output of two grating-stabilized external-cavity diode lasers was injected into a semiconductor tapered amplifier in a master oscillator – power amplifier (MOPA) configuration. At a wavelength of 671 nm this configuration produced 210 mW of power in a diffraction-limited mode with two frequency components of narrow linewidth. The frequency difference ? was varied from 20 MHz to 12 GHz, while the power ratio of the two components was freely adjustable. For ? <2 GHz additional frequency sidebands appear in the output of the MOPA. This configuration is a flexible and simple high-power cw laser source for light with multiple narrow-linewidth frequency components.