Showing papers on "Laser linewidth published in 2004"
TL;DR: In this article, a cancellation of absorption occurs on resonance for two (or any even number of) coupled optical resonators, due to mode splitting and classical destructive interference, particularly when the resonator finesse is large and the loss in resonator farthest from the excitation waveguide is small.
Abstract: We demonstrate that a cancellation of absorption occurs on resonance for two (or any even number of) coupled optical resonators, due to mode splitting and classical destructive interference, particularly when the resonator finesse is large and the loss in the resonator farthest from the excitation waveguide is small. The linewidth and group velocity of a collection of such coupled-resonator structures may be decreased by using larger resonators of equal size, by using larger resonators of unequal size where the optical path length of the larger resonator is an integer multiple of that of the smaller one, or by using a larger number of resonators per structure. We explore the analogy between these effects and electromagnetically-induced transparency in an atomic system.
461 citations
TL;DR: In this article, a single-layer subwavelength periodic waveguide films with binary profiles are applied to design numerous passive guided-mode resonance elements and it is shown that the profile's Fourier harmonic content, along with the absolute value of the grating modulation strength, affects the resonance linewidth and their relative locations.
Abstract: Single-layer subwavelength periodic waveguide films with binary profiles are applied to design numerous passive guided-mode resonance elements. It is shown that the grating profile critically influences the spectral characteristics of such devices. In particular, the symmetry of the profile controls the resonance spectral density. Symmetric profiles generate a single resonance on either side of the second stopband whereas two resonances arise, one on each side of the band, for asymmetric structures. Moreover, the profile's Fourier harmonic content, along with the absolute value of the grating modulation strength, affects the resonance linewidths and their relative locations. Computed Brillouin diagrams are presented to illustrate many key properties of the resonant leaky-mode spectra in relation to modulation strength and profile symmetry at the second stopband. Associated mode plots elucidate the spatial distribution of the leaky-mode field amplitude at resonance and show that, for small modulation, the mode shape may be simple whereas at higher modulation, the shape appears as a complex mixture of modes. By computing device spectra as function of the modulation strength, the buildup of the final spectral properties is illustrated and the contributions of the various leaky modes clarified. The results presented include wavelength and angular spectra for several example devices including narrow linewidth bandpass filters with extended low sidebands for TE and TM polarization, wideband reflectors for TE and TM polarization, polarizer, polarization-independent element, and a wideband antireflector, all with only a single binary layer with one-dimensional periodicity. These results demonstrate new dimensions in optical device design and may provide complementary capability with the field of thin-film optics.
311 citations
01 Jan 2004
TL;DR: In this paper, the authors presented a compact integrated fiber laser with more than 200 mW of output power, which combines polarized fiber output with very narrow linewidth of less than 2 kHz.
Abstract: We present a compact integrated fiber laser with more than 200 mW of output power. It combines polarized fiber output with very narrow linewidth of less than 2 kHz. The coherence length of the laser is measured to be longer than 5 km. The laser features high mode stability of less than /spl plusmn/10 MHz over hours. The relative intensity noise (RIN) spectrum is dominated by a peak at the relaxation oscillation frequency and is shot-noise limited otherwise. The RIN peak at 1 MHz is reduced to /spl sim/-130 dB/Hz by integrating a negative feedback circuit. In addition to thermal wavelength tuning, the laser frequency can be modulated at a bandwidth of up to 10 kHz via the piezoelectric effect.
309 citations
TL;DR: In this article, a method for the measurement of the linewidth enhancement factor of semiconductor laser diodes is presented, based on the interferometric self-mixing effect.
Abstract: A new method for the measurement of the linewidth enhancement factor of semiconductor lasers is presented, based on the interferometric self-mixing effect. It is a fast and easy to perform method that does not require radio frequency nor optical spectrum measurements. A small fraction of the emitted light is backreflected into the laser cavity by a remote target driven by a sine waveform. The mixing of the returned and the lasing fields generates a modulation of the optical output power in the form of an interferometric waveform, with a shape that depends on the optical feedback strength and the linewidth enhancement factor /spl alpha/, according to the well-known Lang-Kobayashi theory. We show that the value of /spl alpha/ can be retrieved from a simple measurement of two characteristic time intervals of the interferometric waveform. Experimental results obtained on different laser diodes show an accuracy of /spl plusmn/6.5%.
244 citations
TL;DR: A wide-bandwidth, phase-stabilized femtosecond laser is used to monitor the real-time dynamic evolution of population transfer and the mechanical action of the optical frequency comb on the atomic sample is explored and controlled, leading to precision spectroscopy with an appreciable reduction in systematic errors.
Abstract: Ultrashort laser pulses have thus far been used in two distinct modes. In the time domain, the pulses have allowed probing and manipulation of dynamics on a subpicosecond time scale. More recently, phase stabilization has produced optical frequency combs with absolute frequency reference across a broad bandwidth. Here we combine these two applications in a spectroscopic study of rubidium atoms. A wide-bandwidth, phase-stabilized femtosecond laser is used to monitor the real-time dynamic evolution of population transfer. Coherent pulse accumulation and quantum interference effects are observed and well modeled by theory. At the same time, the narrow linewidth of individual comb lines permits a precise and efficient determination of the global energy-level structure, providing a direct connection among the optical, terahertz, and radio-frequency domains. The mechanical action of the optical frequency comb on the atomic sample is explored and controlled, leading to precision spectroscopy with an appreciable reduction in systematic errors.
241 citations
TL;DR: Saturation spectroscopy demonstrates that the neutral exciton behaves as a two-level system and the remaining problem for manipulating excitonic quantum states in this system is spectral fluctuation on a mueV energy scale.
Abstract: We show how the optical properties of a single semiconductor quantum dot can be controlled with a small dc voltage applied to a gate electrode. We find that the transmission spectrum of the neutral exciton exhibits two narrow lines with approximately 2 mueV linewidth. The splitting into two linearly polarized components arises through an exchange interaction within the exciton. The exchange interaction can be turned off by choosing a gate voltage where the dot is occupied with an additional electron. Saturation spectroscopy demonstrates that the neutral exciton behaves as a two-level system. Our experiments show that the remaining problem for manipulating excitonic quantum states in this system is spectral fluctuation on a mueV energy scale.
228 citations
TL;DR: In this article, random laser action with coherent feedback has been observed in ZnO nanorod arrays embedded in epilayers and the dependence of the lasing threshold intensity on the excitation area is shown in good agreement with the random laser theory.
Abstract: Random laser action with coherent feedback has been observed in ZnO nanorod arrays embedded in ZnO epilayers The sample was fabricated by depositing a MgO buffer layer and followed by a layer of ZnO thin film onto a vertically well-aligned ZnO nanorod arrays grown on sapphire substrate Under 355 nm optical excitation at room temperature, sharp lasing peaks emit at around 390 nm with a linewidth less than 04 nm has been observed in all directions In addition, the dependence of the lasing threshold intensity on the excitation area is shown in good agreement with the random laser theory Hence, it is demonstrated that random laser action can also be supported in ZnO nanorod arrays
217 citations
TL;DR: Based on phase-matched collinear difference-frequency generation in a single GaSe crystal, continuously tunable and coherent radiation in the extremely wide ranges of 2.7-38.4 and 58.2-3540 μm has been achieved.
Abstract: Based on phase-matched collinear difference-frequency generation in a single GaSe crystal, continuously tunable and coherent radiation in the extremely wide ranges of 2.7–38.4 and 58.2–3540 μm has been achieved. This unique source has the additional advantages of high coherence (narrow linewidth) and simple alignment. The peak output power for the terahertz radiation reaches 209 W at the wavelength of 196 μm (1.53 THz), which corresponds to a power conversion efficiency of 0.055%. Moreover, the terahertz transmission spectra on DNA macromolecules and protein were directly measured, demonstrating some potential and important applications of this terahertz source.
183 citations
TL;DR: In this paper, a sequence of hole-burning pulses is used to isolate selected transitions between hyperfine levels, which makes it possible to directly study properties of the transitions, e.g., transition strengths, and gives access to information that is difficult to obtain in standard hole burning spectroscopy.
Abstract: Due to their narrow homogeneous linewidths, rare-earth ions in inorganic crystals at low temperatures have recently been given considerable attention as test materials for experiments in coherent quantum optics. Because these narrow linewidth transitions have been buried in a wide inhomogeneous line, the scope of experiments that could be carried out in these materials has been limited. However, here we present spectroscopic techniques, based on spectral hole burning and optical pumping, which allow hyperfine transitions that are initially buried within an inhomogeneously broadened absorption line to be studied with no background absorption from other transitions. A sequence of hole-burning pulses is used to isolate selected transitions between hyperfine levels, which makes it possible to directly study properties of the transitions, e.g., transition strengths, and gives access to information that is difficult to obtain in standard hole-burning spectroscopy, such as the ordering of hyperfine levels. The techniques introduced are applicable to absorbers in a solid with long-lived sublevels in the ground state and where the homogeneous linewidth and sublevel separations are smaller than the inhomogeneous broadening of the optical transition. In particular, this includes rare-earth ions doped into inorganic crystals and in the present work the techniques are demonstrated in spectroscopy of Pr 3+ in Y2SiO5. Information on the hyperfine structure and relative transition strengths of the 3 H 4 - 1 D 2 hyperfine transitions in Pr 3+ :Y 2SiO5 has been obtained from frequency-resolved absorption measurements, in combination with coherent and incoherent driving of the transitions.
169 citations
TL;DR: In this article, a stable dual-wavelength Q-switched fiber laser for applications in differential absorption Lidar with tunability in absolute wavelength over several nanometers and discrete tuning in wavelength spacing from 1.1 to 3.3 nm was demonstrated.
Abstract: We demonstrate a stable dual-wavelength Q-switched fiber laser for applications in differential absorption Lidar with tunability in absolute wavelength over several nanometers and discrete tuning in wavelength spacing from 1.1 to 3.3 nm. Single longitudinal-mode operation is also achieved by employing Sagnac loop saturable absorber filter. The delayed self homodyne linewidth measurement of the dual-wavelength continuous-wave laser shows a very narrow spectral linewidth and frequency jitter (<40 kHz). The advantages of tunable wavelengths, narrow linewidth, temperature insensitivity, and high stability in an efficient, cost effective, rugged, compact and light system make it a promising technology for airborne Lidar systems.
144 citations
TL;DR: In this article, a classical version of the two-magnon model of ferromagnetic resonance linewidth in inhomogeneous magnetic thin films is described in terms of film properties and the statistical properties of the inhomogeneity.
Abstract: This paper describes a classical version of the two-magnon model of ferromagnetic resonance linewidth in inhomogeneous magnetic thin films. The ferromagnetic resonance line broadening due to inhomogeneity is described in terms of film properties and the statistical properties of the inhomogeneity. Analytical results for the case of ultrathin films in the limit of zero damping are compared with numerical results computed with finite damping.
TL;DR: In this paper, the first and second-order Raman spectra of cubic ZnS were revisited with two laser lines for samples with different isotopic compositions, aiming at a definitive assignment of the observed Raman features and the mechanisms which determine the linewidth of the first order TO and LO Raman phonons.
Abstract: The first- and second-order Raman spectra of cubic ZnS $(\ensuremath{\beta}$-ZnS, zinc-blende) are revisited. We consider spectra measured with two laser lines for samples with different isotopic compositions, aiming at a definitive assignment of the observed Raman features and the mechanisms which determine the linewidth of the first order TO and LO Raman phonons. For this purpose, the dependence of the observed spectra on temperature and pressure is investigated. The linewidth of the TO phonons is found to vary strongly with pressure and isotopic masses. Pressure runs, up to 15 GPa, were performed at 16 K and 300 K. Whereas well-defined TO Raman phonons were observed at low temperature in the whole pressure range, at 300 K the TO phonons appear to hybridize strongly with the two-phonon background and lose their identity, especially in the (3--10)-GPa region. The intensity of the TO phonons, which nearly vanishes when measured with a red laser line, is shown to result from a destructive interference of the amplitudes of the band-edge resonance and that of a background of opposite sign. The analysis of these effects is aided by calculations of the densities of one- and two-phonon states performed with the adiabatic bond charge model of the lattice dynamics.
TL;DR: In this article, Zhao et al. demonstrated room-temperature ultraviolet lasing in mirrorless zinc oxide thin-film waveguides on (100) silicon substrate and found that the lasing wavelength and linewidth of the zinc oxide random laser under 355 nm optical excitation are around 390 nm and less than 0.4 nm, respectively.
Abstract: Room-temperature ultraviolet lasing is demonstrated in mirrorless zinc oxide thin-film waveguides on (100) silicon substrate. Laser cavities, due to closed-loop optical scattering from the lateral facets of the irregular zinc oxide grains, are generated through the post-growth annealing of high-crystal-quality zinc oxide thin films obtained from the filtered cathodic vacuum arc technique. It is found that the lasing wavelength and linewidth of the zinc oxide random lasers under 355 nm optical excitation are around 390 nm and less than 0.4 nm, respectively. In addition, the lasing threshold characteristics are in good agreement with the random laser theory.
TL;DR: In this article, the spectral linewidth of three continuous-wave quantum cascade lasers operating at terahertz frequencies was measured by heterodyning the free-running quantum cascade laser with two far-infrared gas lasers.
Abstract: We have measured the spectral linewidths of three continuous-wave quantum cascade lasers operating at terahertz frequencies by heterodyning the free-running quantum cascade laser with two far-infrared gas lasers. Beat notes are detected with a GaAs diode mixer and a microwave spectrum analyzer, permitting very precise frequency measurements and giving instantaneous linewidths of less than ∼30 kHz. Characteristics are also reported for frequency tuning as the injection current is varied.
TL;DR: It is demonstrated that femtosecond laser frequency combs (FLFCs) can have a subhertz linewidth across their entire emission spectra when they are phase locked to a reference laser with a similarly narrowLinewidth.
Abstract: We demonstrate that femtosecond laser frequency combs (FLFCs) can have a subhertz linewidth across their entire emission spectra when they are phase locked to a reference laser with a similarly narrow linewidth. Correspondingly, the coherence time of the comb components relative to the reference laser can be of the order of a few seconds. Thus we are able to detect high-contrast spectral interferograms at up to 10-s integration time between two FLFCs locked to a common optical reference.
TL;DR: In this article, a broadly tunable narrow-linewidth microwave subcarrier on an optical wave by exploiting the nonlinear dynamics of a semiconductor laser through a proper combination of optical injection and optoelectronic feedback is experimentally demonstrated.
Abstract: Generation of a broadly tunable narrow-linewidth microwave subcarrier on an optical wave by exploiting the nonlinear dynamics of a semiconductor laser through a proper combination of optical injection and optoelectronic feedback is experimentally demonstrated. The microwave frequency is generated by the period-one oscillation of an optically injected semiconductor laser. It is tuned in the range from 10 to 23 GHz by varying the optical injection strength, and its linewidth can be narrowed by optoelectronic feedback alone. The linewidth is reduced from the range of 40-120 MHz without stabilization by three orders of magnitude to the range of 10-160 kHz with stabilization through optoelectronic feedback alone. The effect of a small microwave modulation is also investigated. It reduces the linewidth to below the 1-kHz resolution limit of our instrument.
TL;DR: In this paper, the spectral dependence of the modal gain and linewidth enhancement factor is measured in an InAs/GaInAs/AlGaAs/GAAs quantum dot (QD) laser and a GaInAs+AlGaA/GaAs quantum well laser of the same design lacking only the quantum dots.
Abstract: The spectral dependence of the modal gain and linewidth enhancement factor is measured in an InAs/GaInAs/AlGaAs/GaAs quantum dot (QD) laser and a GaInAs/AlGaAs/GaAs quantum well laser of the same design lacking only the quantum dots. The material differential gain and material differential carrier induced refractive index are found to be about three times smaller in the quantum dot laser than in the quantum well laser. The linewidth enhancement factor is smaller in the QD laser and exhibits considerably less dispersion.
TL;DR: In this paper, room-temperature stimulated emission (SE) was obtained at 620 nm from an optical cavity formed by growing in situ Eu-doped GaN thin films on sapphire substrates.
Abstract: Rare-earth-based lasing action in GaN is demonstrated. Room-temperature stimulated emission (SE) was obtained at 620 nm from an optical cavity formed by growing in situ Eu-doped GaN thin films on sapphire substrates. The SE threshold for optical pumping of a ∼1 at. % Eu-doped GaN sample was ∼10kW∕cm2. The SE threshold was accompanied by reductions in the emission linewidth and lifetime. A modal gain of ∼43cm−1 and a modal loss of ∼20cm−1 were obtained.
TL;DR: A universal correlation between the spectral linewidth and position of the excitonic transition in the spectral jitter observed from single elongated colloidal quantum dots is demonstrated.
Abstract: We demonstrate a universal correlation between the spectral linewidth and position of the excitonic transition in the spectral jitter observed from single elongated colloidal quantum dots. Breaking the symmetry of electron and hole confinement as well as of the spatial directions for surface charge diffusion enables us to microscopically track meandering surface charges, providing a novel probe of the particle's nanoenvironment. Spectral diffusion exhibits only a weak temperature dependence, which allows us to uncover the single particle homogeneous linewidth of 50 meV at room temperature.
TL;DR: A second-generation pulse-burst laser system for high-speed flow diagnostics with addition of a phase-conjugate mirror allows for more-efficient amplification and harmonic generation, with efficiencies exceeding 50% for second- Harmonic and 40% for third-harmonic generation.
Abstract: A second-generation pulse-burst laser system for high-speed flow diagnostics is described in detail. The laser can produce a burst of high-energy pulses (of the order of hundreds of millijoules per pulse) with individual pulse durations of less than 10 ns and pulse separations as short as 1 micros. A key improvement is the addition of a phase-conjugate mirror, which effectively isolates the high-intensity, short-duration pulses from the low-intensity, long-duration background illumination. It allows for more-efficient amplification and harmonic generation, with efficiencies exceeding 50% for second-harmonic and 40% for third-harmonic generation. Characteristics of the laser system, including gain narrowing, pulse-burst energy distribution, pulse narrowing, and overall pulse-burst energy, are described. In addition, the applicability of the laser for spectroscopic-based flow diagnostics is demonstrated through the presentation of megahertz-rate planar Doppler velocimetry results.
TL;DR: In this article, self-assembled InAs quantum dots (QDs) with In 0.15 Ga 0.85 As were grown by a molecular beam epitaxy and their optical properties were investigated by photoluminescence (PL) spectroscopy.
TL;DR: Light from a Nd:YAG laser is independently stabilized to two Fabry-Perot etalons situated on separate vibration-isolation platforms, showing their relative frequency stability to be at the part-in-10(15) level at 5 s and the relative linewidth to be less than 1 Hz.
Abstract: Light from a Nd:YAG laser at 1064 nm is independently stabilized to two Fabry–Perot etalons situated on separate vibration-isolation platforms. A heterodyne beat measurement shows their relative frequency stability to be at the part-in-1015 level at 5 s and the relative linewidth to be less than 1 Hz.
TL;DR: In this paper, the fine structure splitting of bright exciton states is measured for a range of thermally annealed InGaAs quantum dot (QD) samples with differing degrees of intermixing and also for a dot-in-a-well (DWELL) structure.
Abstract: The fine structure splitting of bright exciton states is measured for a range of thermally annealed InGaAs quantum dot (QD) samples with differing degrees of $\mathrm{In}∕\mathrm{Ga}$ intermixing and also for a dot-in-a-well (DWELL) structure. Magnitudes of the fine structure splitting are determined in polarization-resolved differential transmission experiments from measurements of the period of quantum beats observed in QD exciton dynamics. The splitting is found to decrease in structures with weaker strain: both for $\mathrm{In}∕\mathrm{Ga}$ intermixed QD's and also in dots surrounded by strain-reducing layers (DWELL's). Our findings pave the way to the achievement of entangled two photon sources based on emission from individual QD's, currently prevented since the fine structure splitting is larger than the radiative linewidth.
TL;DR: In this article, double resonance optical pumping (DROP) spectra for the 5P3∕2-4D3 ∕2 transition of R87b were presented.
Abstract: We present double resonance optical pumping (DROP) spectra for the 5P3∕2–4D3∕2 transition and the 5P3∕2–4D5∕2 transition of R87b and we use these spectra for frequency stabilization in the 1.5μm region. The spectra, compared to the conventional double resonance spectrum, show a good signal-to-noise ratio and a narrow spectral linewidth for laser frequency stabilization. The different intensities of the hyperfine states were attributed to the different rates of double resonance optical pumping into the other ground state. When we stabilized the frequency of a 1.5μm laser diode to the DROP spectrum, the best frequency stability was 1×10−11 after 100s.
TL;DR: In this article, the linewidth in intersubband transitions can be significantly reduced below the sum of the lifetime broadening for the involved states, if the scattering environment is similar for both states.
Abstract: The linewidth in intersubband transitions can be significantly reduced below the sum of the lifetime broadening for the involved states, if the scattering environment is similar for both states. This is studied within a nonequilibrium Green function approach here. We find that the effect is of particular relevance for a recent, relatively low doped, THz quantum cascade laser.
TL;DR: In this paper, the optical transitions in AlN and GaN epilayers at temperatures from 10 to 800K were studied, from which the parameters that describe the temperature variation of the energy band gap (α and β or aB and θ) and linewidth broadening have been obtained.
Abstract: Deep ultraviolet photoluminescence spectroscopy has been employed to study the optical transitions in AlN and GaN epilayers at temperatures from 10 to 800K, from which the parameters that describe the temperature variation of the energy band gap (α and β or aB and θ) and linewidth broadening have been obtained These parameters are compared with the previously reported values in AlN and GaN obtained by different methods in narrower temperature ranges Our experimental results demonstrate that the broader temperature range of measurements is necessary to obtain accurate values of these parameters, particularly for AlN These results, together with other well-known physical properties of AlN, may expand future prospects for the application of III-nitride materials
TL;DR: Heterodyne mixing of two free-running, multimode, 3.3-THz quantum cascade lasers by use of a point-contact Schottky diode is demonstrated, with a signal-to-noise ratio of 30 dB.
Abstract: We demonstrate heterodyne mixing of two free-running, multimode, 3.3-THz quantum cascade lasers by use of a point-contact Schottky diode. By temperature tuning the emission wavelength of one laser, a difference frequency signal spanning the 2-4-GHz range is obtained, with a signal-to-noise ratio of 30 dB. The frequency of the heterodyne signal is subject to random fluctuations of a few megahertz, principally from instabilities in the temperatures of the devices. From single-shot measurements we derive an instantaneous linewidth for a single Fabry-Perot mode of 20 kHz, corresponding to an integration time of 3.6 ms.
TL;DR: A diode-pumped KGd(WO/sub 4/)/sub 2/ Yb/sup 3+/ doped laser has been developed for CW-THz generation as discussed by the authors.
Abstract: A diode-pumped KGd(WO/sub 4/)/sub 2/ Yb/sup 3+/ doped laser has been developed for CW-THz generation The frequency difference between the two modes is step tunable from DC to 31 THz A maximum total optical output power of 120 mW CW has been obtained with a beat note linewidth narrower than 30 kHz
20 Dec 2004
TL;DR: In this article, the development of high-power GaAs-based ridge wave guide distributed feedback lasers is described, where the distributed feedback is provided by first or second order gratings, formed in an InGaP/GaAsP/InGaP multilayer structure embedded into the p-AlGaAs cladding layer.
Abstract: The development of high-power GaAs-based ridge wave guide distributed feedback lasers is described. The lasers emit between 760 nm and 980 nm either in TM or TE polarization. Over a large current range, the lasers exhibit stable operation in a single transversal and longitudinal mode. A maximum continuous-wave output power of about 400 mW, a spectral linewidth below 1 MHz and a side mode suppression ratio greater than 50 dB have been demonstrated at room temperature. The distributed feedback is provided by first or second order gratings, formed in an InGaP/GaAsP/InGaP multilayer structure embedded into the p-AlGaAs cladding layer. Applications of such wavelength stabilized devices in non-linear frequency conversion, spectroscopy and for excitation of atomic transitions are discussed.
TL;DR: In this paper, the authors reported measurements of optical transitions in single III/V (InGaN) quantum dots as a function of time and attributed this temporal variation to randomly generated local electric fields inducing a Stark shift in the optical emission peaks of the InGaN quantum dots.
Abstract: We report measurements of optical transitions in single III/V (InGaN) quantum dots as a function of time. Temporal fluctuations in microphotoluminescence peak position and linewidth are demonstrated and attributed to spectral diffusion processes. The origin of this temporal variation is ascribed to randomly generated local electric fields inducing a Stark shift in the optical emission peaks of the InGaN quantum dots.