Showing papers on "Laser linewidth published in 1993"
TL;DR: In this article, a theory of noise in mode-locked laser systems was developed that applies to additive pulse and Kerr lens mode-locking systems, and the effect of gain fluctuations, mirror vibrations, and index fluctuations were determined.
Abstract: A theory of noise in mode-locked lasers is developed that applies to additive pulse mode-locked and Kerr lens mode-locked systems. Equations of motion are derived for pulse energy, carrier linewidth, frequency pulling, and timing jitter. The effect of gain fluctuations, mirror vibrations, and index fluctuations are determined. Measurements that can determine all four fluctuation spectra are described. Experimental data in the literature are compared with theory. >
466 citations
TL;DR: In this article, the authors present experimental data for a high-power CO/sub 2/ laser which confirm the validity of a simple analysis for the beam divergence and beam quality of the output beam from a large-bore multimode stable-cavity laser oscillator.
Abstract: The authors present experimental data for a high-power CO/sub 2/ laser which confirm the validity of a simple analysis for the beam divergence and beam quality of the output beam from a large-bore multimode stable-cavity laser oscillator. The multimode beam parameters can be accurately predicted from a simple theory using only the geometrical parameters of the stable resonator. The data also suggest that a laser of this type with a uniform gain profile across the tube bore oscillates preferentially in the highest order modes allowed by the laser cavity rather than, for example, equipartitioning the output power among all the allowed cavity modes. >
179 citations
TL;DR: In this paper, the authors demonstrate that femtosecond laser pulses can be spectrally narrowed by self-phase modulation in optical fibers and obtain a reduction of the spectral linewidth from 10.6 nm to 2.7 nm, limited only by the laser power in the fiber.
Abstract: We demonstrate experimentally and theoretically that frequency‐modulated femtosecond laser pulses can be spectrally narrowed by self‐phase modulation in optical fibers. We obtain a reduction of the spectral linewidth from 10.6 down to 2.7 nm, limited only by the laser power in the fiber. Applications for extracavity conversion of femtosecond lasers to narrow‐linewidth picosecond sources are discussed.
160 citations
01 Apr 1993
TL;DR: In this paper, a simple method to produce a clock transition with purely optical means by modulated pumping is described, where the field-independent ground state resonance of /sup 87/Rb atoms using sinusoidal modulation of the injection current of an AlGaAs laser diode emitting at 780 nm (FM modulation) is observed.
Abstract: A simple method to produce a clock transition with purely optical means by modulated pumping is described. The field-independent ground state resonance of /sup 87/Rb atoms using sinusoidal modulation of the injection current of an AlGaAs laser diode emitting at 780 nm (FM modulation) is observed. The 6.835 GHz resonance with a subharmonic modulation frequency of 1.139 GHz is detected. A high-contrast resonance peak is observed and a condition for zero light shift is found. The linewidth is 3 kHz (at 6.835 GHz) in this preliminary experiment, due to the small size of the light beam ( approximately 2 mm diameter) and the low buffer gas pressure (680 Pa) that was used. A theoretical model that explains the main features of the experiment is described. >
145 citations
TL;DR: The first femtosecond electronic dephasing in CdSe nanocrystals using three-pulse photon echoes and a novel mode-suppression technique was reported in this article.
Abstract: We report the first direct measurements of femtosecond electronic dephasing in CdSe nanocrystals using three-pulse photon echoes and a novel mode-suppression technique. We are able to separate the dynamics of the coherently excited LO phonons from the underlying electron-hole dephasing by suppressing the quantum beats. The homogeneous linewidth of these materials at 15 K results from electronic dephasing in \ensuremath{\sim}85 fs, approximately half of which is due to acoustic phonon modes. Contributions from acoustic phonons dominate the homogeneous linewidth at room temperature.
143 citations
TL;DR: The spontaneous-emission coupling factor β for planar microcavities without lateral confinement is measured and calculated and it is shown that in order to maximize β, the spontaneous- emission linewidth of the gain medium must be smaller or equal to the cold-cavity linewsidth.
Abstract: The spontaneous-emission coupling factor \ensuremath{\beta} for planar microcavities without lateral confinement is measured and calculated for gain media with finite spontaneous-emission linewidth. It is shown that in order to maximize \ensuremath{\beta}, the spontaneous-emission linewidth of the gain medium must be smaller or equal to the cold-cavity linewidth. It is also shown that the planar-cavity geometry will give rise to spatial modes, and in order to maximize \ensuremath{\beta} one should pump only an area corresponding to one spatial mode. If the pumped area is larger than the lateral extent of a cavity mode, then the mode will grow laterally when pumped above threshold.
131 citations
TL;DR: In this article, the authors present a comprehensive and quasi-tutorial review of the theory for analyzing the optical power spectrum of an optical field that has noise modulations of both the amplitude and the phase.
Abstract: We present a comprehensive and quasi-tutorial review of the theory for analyzing the optical power spectrum of an optical field that has noise modulations of both the amplitude and the phase. We also present experimental results of the frequency stabilization of a commercial dye laser to a high-finesse Fabry–Perot cavity (0.49-Hz resulting full linewidth) and of the optical phase locking of the dye laser to a second reference laser (putting 97% of the optical power into the carrier) using an external stabilizer scheme. This external optical phase/frequency stabilization technique can be applied to virtually any cw laser system.
126 citations
TL;DR: In this paper, the effect of substrate temperature and oxygen partial pressure on the structure, composition, and magnetic properties of epitaxial Y3Fe5O12 (YIG) films was investigated and compared to liquid phase epitaxy YIG films.
Abstract: Epitaxial Y3Fe5O12 (YIG) films have been grown by the pulsed laser deposition (PLD) technique on (111) gadolinium gallium garnet substrates. The effect of substrate temperature and oxygen partial pressure on the structure, composition, and magnetic properties of the films was investigated and compared to liquid phase epitaxy YIG films. The results demonstrated that epitaxial YIG films could be prepared under a wide range of deposition conditions, but narrow linewidth (ΔH≂1 Oe) films were producible only at low oxygen partial pressures (O2<250 mTorr) and relatively high substrate temperatures (Ts≳800 °C). Since the linewidth of single‐crystal YIG is dominated by surface and volume defects and/or impurities, the narrow linewidth indicated that PLD is a viable technique for producing high‐quality ferrite films for microwave device applications. In addition, under all deposition conditions (50–1000 mTorr and 700–850 °C) there is a uniaxial axis perpendicular to the film plane. However, at low oxygen pressure ...
123 citations
TL;DR: In this paper, a picosecond, widely tunable, optical parametric generator-amplifier system was constructed with barium borate and lithium triborate crystals pumped by third or second-harmonic output of an active-passive mode-locked Nd:YAG laser.
Abstract: A picosecond, widely tunable, optical parametric generator–amplifier system can be constructed with barium borate and lithium triborate crystals pumped by third- or second-harmonic output of an active–passive mode-locked Nd:YAG laser. A tunable output of several hundred mirojoules per pulse with a conversion efficiency as high as 30% has been obtained. The tuning range covers from 0.4 to 2.0 or from 0.6 to 2.5 μm and can be extended by sum- and difference-frequency generation to near 0.2 μm in the UV and to near 8 μm in the IR. The output linewidth can be narrowed to near the transform limit with the help of frequency selection by a grating.
103 citations
TL;DR: It is found that, for regular pumping, maximum amplitude-noise reduction still occurs at zero frequency in all cases, however, a long-living polarizaton leads to an increase in amplitude noise and may even eliminate the dip atzero frequency, at the same time leading to a significant quenching of the laser linewidth in the bad-cavity limit.
Abstract: We solve the problem of a laser with variable pumping statistics for any relative magnitude of the atomic- and cavity-decay constants, and obtain a different regime of sub-Poissonian light generation. We show that, even for Poissonian pumping, the noise in the amplitude quadrature outside the cavity can be reduced up to 50% below the shot-noise level when the polarization but not the populations can be adiabatically eliminated. Maximum noise reduction in this case is obtained when the lower level decays much faster than the upper one and occurs at a frequency given by the geometrical mean of the decay rates of the field and the lower-level population. Furthermore, the full consideration of atomic memory effects leads to a generalization of previous results on regularly pumped lasers. We find that, for regular pumping, maximum amplitude-noise reduction (up to complete quieting) still occurs at zero frequency in all cases. However, a long-living polarizaton leads to an increase in amplitude noise and may even eliminate the dip at zero frequency, at the same time leading to a significant quenching of the laser linewidth in the bad-cavity limit.
100 citations
TL;DR: A single-frequency, diode-pumped, Er-Yb:glass microchip laser at a 1530-nm wavelength has been designed and operated and a slope efficiency of 22% has been obtained.
Abstract: A single-frequency, diode-pumped, Er-Yb:glass microchip laser at a 1530-nm wavelength has been designed and operated. An output power of greater than 25 mW, a linewidth narrower than 1 kHz, and a slope efficiency of 22% have been obtained.
TL;DR: In this article, the authors reported a 7.6mW single-frequency fiber laser operating at 1545 nm, using for the first time an Er/sup 3+/:Yb/Sup 3++/ doped fiber and a fiber grating output coupler.
Abstract: We report a 7.6-mW single-frequency fiber laser operating at 1545 nm, using for the first time an Er/sup 3+/:Yb/sup 3+/ doped fiber and a fiber grating output coupler. The laser did not exhibit self-pulsation, which is a typical problem in short three-level fiber lasers, and had a relative intensity noise (RIN) level below -145.5 dB/Hz at frequencies above 10 MHz. The linewidth of the laser was limited by the relaxation oscillation sidebands in the optical spectrum and was typically less than 1 MHz. >
TL;DR: Ultranarrow bandpass Na vapor dispersive Faraday filters at 589 nm are studied experimentally and theoretically and their anticipated performance in the line-center operation is demonstrated experimentally with a thin Na cell in an axial magnetic field of 1750 G.
Abstract: Ultranarrow bandpass Na vapor dispersive Faraday filters at 589 nm are studied experimentally and theoretically. Their anticipated performance in the line-center operation is demonstrated experimentally with a thin Na cell in an axial magnetic field of 1750 G. A peak vapor transmission of 85%, a FWHM linewidth of 0.002 nm (or 1.9 GHz), and a background transmission of 2 × 10−5 have been achieved.
TL;DR: In this article, the effect of optical feedback on the stability of the modelocking frequency of monolithic, passively modelocked semiconductor lasers at approximately 50 GHz was investigated, and the effects of the optical feedback vary periodically as the length of the feedback delay is varied, with a periodicity that roughly matches the mode-locking wavelength.
Abstract: The effect of optical feedback on the stability of the modelocking frequency of monolithic, passively modelocked semiconductor lasers at approximately 50 GHz is investigated. Optical feedback leads to linewidth narrowing, frequency pulling, and multiple modes of the intensity modulations in modelocked lasers, reminiscent of similar effects on the optical frequency in conventional continuous wave (CW) lasers. The narrowest observed line has a full-width-at-half-maximum (FWHM) of 56 kHz, which represents close to two orders of magnitude reduction of the linewidth compared to the situation without feedback. The effects of the optical feedback vary periodically as the length of the feedback delay is varied, with a periodicity that roughly matches the mode-locking wavelength. This wavelength is on the order of millimeters, which makes the mechanical stability of the optical feedback loop relatively uncritical. >
TL;DR: In this article, an integrated receiver consisting of two Josephson fluxflow oscillators and a superconductor-insulator-superconductor (SIS) mixer was used to measure the linewidth of the oscillators.
Abstract: An integrated receiver consisting of two Josephson flux‐flow oscillators and a superconductor‐insulator‐superconductor (SIS) mixer has been used to measure the linewidth of the oscillators. The oscillators are coupled to the SIS mixer using two centerfed interdigital capacitors, one of which with a fairly weak (−20 dB) coupling. By biasing the two oscillators (a few microvolt apart) on their velocity matching steps, the two resulting oscillations (280–330 GHz) were mixed in the SIS mixer. The difference frequency was amplified and detected on a spectrum analyzer. The combined linewidth of the two oscillators was 2.1 MHz throughout the band. The calculated available power incident on the SIS mixer was 430 nW at 320 GHz. The rf power from the oscillators, which could be tuned by changing the current bias, is high enough to pump the SIS mixer optimally.
TL;DR: In this paper, the authors studied the space-time dynamical behavior of broad-area semiconductor lasers, using an extended phenomenological laser model to include transverse diffraction of the counterpropagating optical fields and transverse diffusion of carriers.
Abstract: We study the space–time dynamical behavior of broad-area semiconductor lasers, using an extended phenomenological laser model to include transverse diffraction of the counterpropagating optical fields and transverse diffusion of carriers. Numerical results show that the profile of the output intensity exhibits spatiotemporal chaos by way of changing random filaments. A small confinement factor and/or linewidth enhancement factor can prevent instabilities. Simulations also confirm experimental results showing that a half-symmetric unstable resonator with a suitable mirror curvature restores stability.
TL;DR: In this article, a 1% compressive strained multiquantum-well (MQW) active layer was introduced into a corrugation-pitch-modulated distributed feedback (CPM-DFB) laser.
Abstract: Introducing a 1% compressive strained multiquantum-well (MQW) active layer into a corrugation-pitch-modulated distributed feedback (CPM-DFB) laser reduces the linewidth floor (residual linewidth for extrapolated infinite output power) to 2 kHz and results in a linewidth-power product of 140 kHz mW. Strained MQW CPM-DFB lasers produced a 55 mW output with a spectral linewidth of only 3.6 kHz.
TL;DR: It is found that the one-atom laser exhibits most of the typical features of a normal laser, but in the region far below threshold some aspects, among them the linewidth, are changed due to eigenvalues of the master equation with imaginary parts.
Abstract: We present a detailed numerical study of the one-atom laser, that is, a single two-level atom interacting with one lasing mode, whereby both the atom and the photon field are coupled to reservoirs. The stationary as well as the dynamical properties of the model are calculated directly from the quantum master equation with the help of two numerical methods. These numerical methods do not need any quasi-probability representation and they do not require approximations. We find that the one-atom laser exhibits most of the typical features of a normal laser. In the region far below threshold some aspects, among them the linewidth, are changed due to eigenvalues of the master equation with imaginary parts
TL;DR: Experimental and theoretical observations of a period-doubling route to chaos in a semiconductor laser with optical feedback and interactions between the external cavity modes and the laser relaxation oscillations are reported.
Abstract: We report experimental and theoretical observations of a period-doubling route to chaos in a semiconductor laser with optical feedback. Increasing the feedback produces a quasiperiodic route to chaos, manifested as a catastrophic increase in the laser linewidth. Under certain conditions, frequency locking occurs in preference to quasiperiodicity, and then period doubling appears. Both phenomena are explained as interactions between the external cavity modes and the laser relaxation oscillations.
Proceedings Article•
[...]
02 May 1993
TL;DR: Two-dimensional quantum confinement in quantum-wire (QWR) semiconductor lasers is expected to yield improved static and dynamic performance compared to conventional quantum-well (QW) lasers as discussed by the authors.
Abstract: Two-dimensional quantum confinement in quantum-wire (QWR) semiconductor lasers is expected to yield improved static and dynamic performance compared to conventional quantum-well (QW) lasers.1,2 The improved features include very low threshold currents (in the microampere regime), reduced temperature sensitivity, higher modulation bandwidth, and narrower spectral linewidth.
Patent•
IBM1
TL;DR: In this paper, a tip strain sensor is combined with a single axis atomic force microscope (AFM) for determining the profile of a surface in 3D, where the tip contact with the linewidth surface will cause tip deflection with a corresponding proportional electrical signal output.
Abstract: An integrated tip strain sensor is combination with a single axis atomic force microscope (AFM) for determining the profile of a surface in three dimensions. A cantilever beam carries an integrated tip stem on which is deposited a piezoelectric film strain sensor. A high-resolution direct electron beam (e-beam) deposition process is used to grow a sharp tip onto the silicon (Si) cantilever structure. The direct e-beam deposition process permits the controllable fabrication of high-aspect ratio, nanometer-scale tip structures. A piezoelectric jacket with four superimposed elements is deposited on the tip stem. The piezoelectric sensors function in a plane perpendicular to that of a probe in the AFM; that is, any tip contact with the linewidth surface will cause tip deflection with a corresponding proportional electrical signal output. This tip strain sensor, coupled to a standard single axis AFM tip, allows for three-dimensional metrology with a much simpler approach while avoiding catastrophic tip "crashes". Two-dimensional edge detection of the sidewalls is used to calculate the absolute value or the linewidth of overlay, independent of the AFM principle. The technique works on any linewidth surface material, whether conductive, non-conductive or semiconductive.
TL;DR: In this paper, a theoretical investigation of the possibility of reducing the linewidth enhancement factor ( alpha factor) in quantum-well (QW) lasers to zero is presented.
Abstract: Low-chirp lasing operation in semiconductor lasers is addressed in a theoretical investigation of the possibility of reducing the linewidth enhancement factor ( alpha factor) in quantum-well (QW) lasers to zero. It is shown that in reducing the alpha factor it is essential that lasing oscillation be around the peak of the differential gain spectrum, not in the vicinity of the gain peak. The condition for such lasing oscillation is analytically derived. The wavelength dependence of the material gain, the differential gain, and the alpha factor are calculated in detail taking into account the effects of compressive strain and band mixing on the valence subband structure. The effect of p-type modulation doping in compressively strained QWs is discussed. It is shown that the alpha factor, the anomalous dispersion part in the spectrum, crosses zero in the region of positive material gain, which makes is possible to attain virtual chirpless operation by detuning. >
TL;DR: In this article, a quasi-3D semiconductor laser model that takes into account both longitudinal and lateral spatial hole burning is presented and used to perform calculations of the longitudinal sidemode-suppression ratio, the lateral side-mode kink power, and the linewidth of devices with coupling up to kappa L=6.
Abstract: A quasi-3-D semiconductor laser model that takes into account both longitudinal and lateral spatial hole burning is presented and used to perform calculations of the longitudinal side-mode-suppression ratio, the lateral side-mode kink power, and the linewidth of devices with coupling up to kappa L=6. Detailed results on the effects of inhomogeneous injection, wavelength detuning, phase shift position, and optical losses on these quantities are discussed and used to draw conclusions on the regions of stable single-mode operation. >
TL;DR: In this paper, the electronic properties of CdSe nanocrystallites (quantum dots) as a function of crystallite diameter (20-80A) were investigated using low temperature (10K) optical hole-burning and fluorescence line narrowing spectroscopy.
Abstract: We use low temperature (10K) optical hole-burning and fluorescence line narrowing spectroscopy to investigate the electronic properties of CdSe nanocrystallites (quantum dots) as a function of crystallite diameter (20–80A). We discuss how the homogeneous linewidth of the HOMO-LUMO transition, the energy shift between the absorbing and emitting state, and the LO phonon frequency vary with nanocrystallite size.
TL;DR: It is shown, both theoretically and experimentally, that stable single-longitudinal-mode operation, with transform-limited spectral linewidth and without pulse-to-pulse mode competition, can be obtained in a monolithic self-Q-switched Cr,Nd:YAG solid-state laser with a distributed saturable absorber.
Abstract: It is shown, both theoretically and experimentally, that stable single-longitudinal-mode operation, with transform-limited spectral linewidth and without pulse-to-pulse mode competition, can be obtained in a monolithic self-Q-switched Cr,Nd:YAG solid-state laser with a distributed saturable absorber. In this system, the lasing mode establishes a loss grating and thereby stabilizes itself.
TL;DR: Theoretical results are in good qualitative and quantitative agreement with previously reported experimental observations and measurements on standing-wave laser oscillators.
Abstract: In standing-wave laser oscillators the field energy density periodically varies along the resonator axis and creates a complex refractive-index grating in the gain medium. This grating couples the originally independent counterpropagating waves of the individual axial cavity modes. The coupling induces a mode frequency shift that is a nonlinear function of the unperturbed mode frequency. The uneven shifts can give rise to a substantial broadening of the beat-note linewidth of the multi-axial-mode free-running laser and to a corresponding increase in the threshold intracavity power for self-starting passive mode locking. The theoretical results are in good qualitative and quantitative agreement with previously reported experimental observations and measurements.
TL;DR: The method to resolve the phase of chi(2) by exploiting the interference between the C60 overlayer contribution and the anisotropic Si(111) substrate contributions is presented and a strong and sharp resonance at 2HBARomega = 3.60 eV is found.
Abstract: We studied the optical-second-harmonic generation from thin C60 films, using a combination of frequency-, rotational-, angular-, and film-thickness-dependent measurements. We present a method to resolve the phase of chi(2) by exploiting the interference between the C60 overlayer contribution and the anisotropic Si(111) substrate contributions. We find a strong and sharp resonance at 2HBARomega = 3.60 eV. The linewidth is found to be surprisingly small as compared to linear ellipsometry and third-harmonic-generation experiments. The intensity as a function of film thickness agrees with a model considering interference effects between equal second-harmonic contributions- from the inner C60/Si interface and the outer C60 surface. The possibility of nonlocal bulk contributions is discussed.
TL;DR: In this article, the wavelength dependence of the linewidth enhancement factor (amplitude phase coupling factor) α in quantum well lasers of different quantum well barrier heights have been determined from the spontaneous emission spectra and the Fabry-Perot mode wavelength shifts.
Abstract: The wavelength dependence of the linewidth enhancement factor (amplitude‐phase coupling factor) α in quantum well lasers of different quantum well barrier heights have been determined from the spontaneous emission spectra and the Fabry–Perot mode wavelength shifts. It is found that the α parameter at lasing wavelength in GaAs/Al0.15Ga0.85As lasers is about twice as large as that in GaAs/Al0.30Ga0.70As lasers. The observation is consistent with the previously observed spectral linewidth behavior in these lasers, which were attributed to the different state filling effects.
TL;DR: In this paper, a three-section, distributed Bragg reflector (DBR) InGaAsP/InP laser diode is described, where the refractive indices of the DBR section and the phase control section are thermally controlled by thin-film heaters embedded on these passive sections.
Abstract: A wavelength-tunable, three-section, distributed Bragg reflector (DBR) InGaAsP/InP laser diode is described. The refractive indices of the DBR section and the phase-control section are thermally controlled by thin-film heaters embedded on these passive sections. This structure enables wide-range wavelength tuning without the spectral linewidth broadening accompanying conventional tuning by current injection into the passive sections. A tuning range of 10.8 nm and a linewidth of less than 1.6 MHz have been achieved in the 1.5- mu m wavelength region. The temperature increase in the active layer is held to within a few degrees, even when the DBR-section temperature reaches 90 degrees C. >
01 Aug 1993
TL;DR: A novel method of frequency division based on optical parametric oscillation is proposed, which converts with high efficiency an input signal into two intense, coherent subharmonic outputs whose frequencies are tunable and whose linewidths are essentially limited by the input pump linework.
Abstract: A novel method of frequency division based on optical parametric oscillation is proposed. This scheme converts with high efficiency an input signal into two intense, coherent subharmonic outputs whose frequencies are tunable and whose linewidths are essentially limited by the input pump linewidth. By locking their difference frequency to a microwave, a millimeter-wave, or an infrared reference source, the output frequencies are precisely determined. The proposed frequency dividers can be operated in series or in parallel to measure, compare, and synthesize frequencies from optical to microwave. A line-narrowing effect for the generation of ultrastable radiation is discussed.