Showing papers on "Laser linewidth published in 1983"
TL;DR: In this paper, light scattering of the linewidth and frequency shift of the optical phonon in silicon over the temperature range of 5-1400 K are presented. But they do not consider the four-phonon anharmonic processes.
Abstract: Systematic measurements by light scattering of the linewidth and frequency shift of the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}=0$ optical phonon in silicon over the temperature range of 5-1400 K are presented. Both the linewidth and frequency shift exhibit a quadratic dependence on temperature at high temperatures. This indicates the necessity of including terms in the phonon proper self-energy corresponding to four-phonon anharmonic processes.
1,208 citations
TL;DR: An InGaAsP 1.5 μm laser, with one facet antireflection coated, has been incorporated into a diffraction grating external cavity in this article, where the lasing wavelength could be tuned over a 55 nm range about the centre wavelength of 1. 5 μm by rotating the grating.
Abstract: An InGaAsP 1.5 μm laser, with one facet antireflection coated, has been incorporated into a diffraction grating external cavity. The lasing wavelength could be tuned over a 55 nm range about the centre wavelength of 1.5 μm by rotating the grating. Furthermore, it was found that the emission spectrum was extremely narrow; beat-frequency measurements at 1523 nm against an HeNe laser showed it to be of the order of 10 kHz.
321 citations
TL;DR: In this paper, it was shown that the additional phase changes also give rise to line shape structure in the form of additional peaks separated from the main peak by multiples of the relaxation oscillation frequency.
Abstract: Spontaneous emission alters the phase and amplitude of the laser field. The amplitude changes induce relaxation oscillations, which cause additional phase changes while restoring the field amplitude to the steady state value. It was previously shown that the additional phase changes greatly enhance the linewidth. We show here that the additional phase changes also give rise to line shape structure in the form of additional peaks separated from the main peak by multiples of the relaxation oscillation frequency. The calculated mean square phase change and power spectrum are in good agreement with published observations.
302 citations
TL;DR: In this article, a model of semiconductor laser noise is presented which includes the carrier density as a dynamical variable and carrier density dependence of the refractive index, and the role of carrier noise in determining the field spectrum linewidth.
Abstract: A model of semiconductor laser noise is presented which includes the carrier density as a dynamical variable and the carrier density dependence of the refractive index. The Van der Pol laser noise model is shown to he a special case of this treatment. Expressions are calculated for all laser spectra and compared with their Van der Pol counterparts. The power fluctuations spectrum and the frequency fluctuations spectrum exhibit a resonance corresponding to the relaxation resonance and the field spectrum contains fine structure, similar to sidebands which result from harmonic frequency modulation of a carrier signal. The role of carrier noise in determining the field spectrum linewidth is also considered.
245 citations
TL;DR: In this paper, a theory of the amplitude and phase modulation characteristic of a single mode semiconductor laser is presented, where the amplitude modulation couples through the complex susceptibility of the gain medium to the phase.
Abstract: A theory of the amplitude and phase modulation characteristic of a single mode semiconductor laser is presented. In this model the amplitude modulation couples through the complex susceptibility of the gain medium to the phase. We show that this coupling constant can be obtained by a high‐frequency modulation experiment. This measured coupling constant is used to infer the linewidth enhancement factor α as discussed by Henry, and Vahala and Yariv. Experiments confirmed the model and we measured a linewidth enhancement factor ‖α‖=4.6±1.0 for a GaAlAs buried optical guide laser.
236 citations
TL;DR: In this article, a simple model for the linewidth enhancement factor α and its frequency dependence in semiconductor lasers is presented, which is in reasonable agreement with the experimental results.
Abstract: A simple model for the linewidth enhancement factor α and its frequency dependence in semiconductor lasers is presented. Calculations based on this model are in reasonable agreement with experimental results.
155 citations
TL;DR: A technique is demonstrated for measuring velocity at multiple locations in a plane of a gaseous flowfield using Doppler-shifted absorption with fluorescence detection from iodine molecules, excited by a sheet of tunable single-axial-mode argon-ion laser radiation.
Abstract: A technique is demonstrated for measuring velocity at multiple locations in a plane of a gaseous flowfield using Doppler-shifted absorption with fluorescence detection from iodine molecules, excited by a sheet of tunable single-axial-mode argon-ion laser radiation at 514.5 nm. Measurements were made simultaneously at 10,000 points in an iodine-seeded supersonic flowfield with a 100 x 100 element photodiode array camera and were found to agree well with a numerical solution for the velocity field. The accuracy with which a component of velocity can be measured is limited, in the current approach, by the iodine linewidth to about +/-5 m/sec.
155 citations
TL;DR: In this article, a single layer of polymethylmethacrylate (PMMA) was exposed by an approximately 2-nm−diam electron beam with energies ranging from 20 to 120 keV.
Abstract: Metal features with 10‐nm linewidths were produced on thick GaAs substrates using electron beam lithography. A single layer of polymethylmethacrylate (PMMA) was exposed by an approximately 2‐nm‐diam electron beam with energies ranging from 20 to 120 keV. Gold‐palladium lines less than 20 nm wide, and 15 nm thick, with center‐to‐center spacings of 70 nm, were produced over 15‐μm square fields at all electron beam energies by lift off. The exposure latitude increased significantly for higher electron energies, with 10‐nm‐wide metal lines formed using a 120‐keV writing beam.
136 citations
TL;DR: In this paper, a new method was presented for determining the semiconductor-laser linewidth broadening factor, which was shown to decrease with decreasing laser length, and was found to have similar values of? (6.6 cf. 6 4), but at 0.85?m significantly lower results were measured.
Abstract: A new method is presented for determining the semiconductor-laser linewidth-broadening factor ?. Measurements on 1.5 ?m devices suggest that ? decreases with decreasing laser length. 300 ?m-long devices emitting at 1.3 and 1.5 ?m were found to have similar values of ? (6.6 cf. 6 4), but at 0.85 ?m significantly lower results were measured (2.8)
134 citations
TL;DR: In this paper, the spectral width and shape of photoluminescence spectra for undoped superlattices were found to be sensitive to the well size of the well.
Abstract: Photoluminescence spectra for undoped superlattices exhibited smaller half widths compared with those obtained in GaAs bulk crystals. However, both the spectral width and shape were found to be very sensitive to the well size. When the well size is greater than about 80 A, the spectrum at 77 K showed smaller linewidth, which agrees with theoretical results, whereas when the well size is smaller than this, the spectral width increased with decreasing well size. In some cases, additional emission bands appeared in the lower energy side of the main emission peak. These phenomena were interpreted in terms of well size fluctuations.
127 citations
TL;DR: In this article, a single frequency dye laser is used as a plasma diagnostic for measuring ion velocity distributions with a resolution limited only by the natural linewidth of the laser excited resonance transition.
Abstract: In this paper we report the development of the single frequency dye laser as a plasma diagnostic for measuring ion velocity distributions with a resolution limited only by the natural linewidth of the laser excited resonance transition. For the 6S1/2–6P1/2 transition in Ba+ this corresponds to a velocity uncertainty of 103 cm/s. Velocity selection is performed by the laser as it scans the Doppler broadened plasma absorption line, in contrast with the usual method of scanning an emission line with a high‐resolution spectrometer. Both sensitivity and resolution are improved by 2 orders of magnitude, allowing nonperturbing measurements to be made at densities below 107 cm−3. In addition to a description of the technique, sample measurements of time‐resolved wave induced modifications of ion velocity distributions are shown.
TL;DR: In this paper, measurements of the frequency and fluence dependences of the photodissociation cross sections were performed over the CO2 laser frequency range from 900 to 1100 cm−1.
Abstract: Molecular beam experiments have been carried out on the infrared photodissociation of the (C2H4)2, (C2D4)2, and (C2H4)⋅ (C2D4) van der Waals molecules. Measurements of the frequency and fluence dependences of the photodissociation cross sections were performed over the CO2 laser frequency range from 900 to 1100 cm−1, which covers the region of the ν7 out‐of‐plane vibration of C2H4 and the ν12 in‐plane vibration of C2D4. In addition, the monomer product speed and angle distributions were measured in order to obtain information on the final energy disposition in the products. Absorption in either vibrational mode induces dissociation of the cluster, but the linewidth associated with excitation of the ν7 mode of C2H4 is about four times larger than that associated with excitation of the ν12 mode of C2D4. Two‐laser ‘‘hole‐burning’’ experiments demonstrate the homogeneity of the ground‐state populations. The absorption intensities are not simply proportional to the number of molecules in the cluster capable of...
TL;DR: In this paper, a theoretical analysis for semiconductor laser linewidth, employing optical feedback, is presented, not only for weak feedback, but also for strong feedback including multiple reflections.
Abstract: We present a theoretical analysis for semiconductor laser linewidth, employing optical feedback. This analysis is valid not only for weak feedback, but also for strong feedback including multiple reflections. The experimental result reported so far under a strong feedback condition is well explained.
TL;DR: In this paper, the linewidth of the far infrared cyclotron resonance in the 2-D electron gas in GaAs-AlxGa1−xAs heterojunctions was shown to be correlated with the filling factor of the Landau levels.
TL;DR: In this article, the linewidth narrowing of a semiconductor laser due to weak optical feedback is analyzed, taking into account both phase condition and threshold change for the feedback-induced modes.
Abstract: The linewidth narrowing of a semiconductor laser due to weak optical feedback is analysed, taking into account both phase condition and threshold change for the feedback-induced modes. The achievable linewidth reduction lies in between two limiting cases, 1/(1 + X √(1 + α2))2 and 1/(1 + X)2, where α and X are the linewidth enhancement factor and the feedback parameter, respectively.
TL;DR: In this article, a model based on the gate linewidth dependence of the SiO2/Si interfacial stress prior to irradiation, which affects the radiation sensitivity in accordance with the strained bond model was proposed.
Abstract: The density of radiation‐induced interface traps in a post‐metal‐annealed (PMA) Al‐gate metal‐oxide‐semiconductor (metal/SiO2/Si) depends strongly on the linewidth of the metal gate over a wide range (1–750 μm) of linewidths studied, although there is no discernible dependence prior to the irradiation. The dependence is such that the narrower the linewidth, the fewer the radiation‐induced interface traps. Such dependence has been generally observed for both p‐ and n‐type Si samples, for oxides grown in dry O2 or steam at temperatures over a wide range (900–1000 °C), and for PMA treatment either in dry N2 or in forming gas (10% H2+90% N2). The results can be qualitatively explained by a model based on the gate linewidth dependence of the SiO2/Si interfacial stress prior to irradiation, which affects the radiation sensitivity in accordance with the strained bond model.
TL;DR: In this article, self-oscillations of V-channeled substrate inner stripe (VSIS) lasers with index guiding and the influence of external feedback on low-frequency noise generation are presented.
Abstract: Self‐oscillations of V‐channeled substrate inner stripe (VSIS) lasers with index guiding and the influence of external feedback on low‐frequency noise generation are presented. The self‐oscillation is induced by means of shortening a cavity length of VSIS laser to 110 μm. VSIS lasers with self‐oscillation have the fundamental linewidth of 0.56 A below 3 mW and are not sensitive to both phase and amplitude of the externally reflected light. Signal to noise ratio of short‐cavity VSIS laser at 1 MHz with a 10‐KHz bandwidth was 97 dB at 0.05% optical feedback.
TL;DR: A single Mg(+) has been successfully trapped and cooled in a small radiofrequency trap and the result is a temperature of 5(-5) (+15) mK, which is lower than that attained previously.
Abstract: A single Mg+ has been successfully trapped and cooled in a small radiofrequency trap. The ion was cooled by using the radiation from a single-frequency ring dye laser whose output was doubled in frequency with an NH42H2PO4 temperature phasematched crystal; a power of about 22 μW or less was sufficient for all of the experiments. The ion temperature was estimated by a computer fit of the experimental resonance line profile; the resulting linewidth was compared to previously published Mg+ 32P3/2 Hanle-effect linewidths. The result is a temperature of 5-5+15 mK, which is lower than that attained previously.
TL;DR: In this paper, the intrinsic linewidth in angle-and energy-resolved photoemission is generally assumed to be limited by the final-state lifetime, but the authors show that in some cases, the linwidth is dominated by weakened ${k}_{||}$ conservation.
Abstract: The intrinsic linewidth in angle- and energy-resolved photoemission is generally assumed to be limited by the final-state lifetime. High-resolution measurements of the intrinsic linewidths for emission from bulk and surface states of Cu show that in some cases the linewidth is dominated by weakened ${k}_{||}$ conservation. We tentatively attribute this effect to a finite mean free path for elastic scattering from the small number (\ensuremath{\approx} 0.01 monolayer) of impurities present at the surface. This suggests that as instrumental precision improves, sample preparation may be the limiting factor determining resolution.
TL;DR: In this article, a sequence of edge defined techniques has been developed which allows the successive multiplication of the number of lines in a grating pattern, which can then be repeatedly applied given a proper choice of materials and etches.
Abstract: A sequence of edge defined techniques has been developed which allows the successive multiplication of the number of lines in a grating pattern. Holographic lithography at 351.4 nm wavelength in a liquid medium has been used as the primary pattern generation technique for producing gratings with periods of ≊160 nm. A shadowing technique is then used to produce x‐ray masks with precisely controlled linewidth‐to‐period ratios. Reactive‐ion etching in CHF3 yields a square profile structure in SiO2 with precise linewidth. The basic edge defined technique consisting of CVD deposition, reactive‐ion etching, and selective isotropic etching can then be repeatedly applied given a proper choice of materials and etches. Each cycle of the edge defined technique doubles the number of lines in the pattern. Careful linewidth control at each step can result in gratings with one‐half of the initial period with minimum fundamental components. Gratings with ∼40 nm period have been fabricated by doubling the number of lines in a 160 nm period grating twice.
TL;DR: Several microwatts of tunable cw radiation near 194 nm in a linewidth of less than 2 MHz have been generated by sum-frequency mixing the radiation from a frequency-doubled argon-ion laser with the Radiation from a ring dye laser in a crystal of potassium pentaborate.
Abstract: Several microwatts of tunable cw radiation near 194 nm in a linewidth of less than 2 MHz have been generated by sum-frequency mixing the radiation from a frequency-doubled argon-ion laser with the radiation from a ring dye laser in a crystal of potassium pentaborate. An external ring cavity resonant with the dye laser gives an enhancement factor of about 14 in the sum-frequency-generated radiation power. The Doppler-limited absorption spectrum of the 6s2S1/2–6p2P1/2 first resonance line of natural Hg ii has been resolved, and the vacuum wave number for the mass-202 isotope has been measured to be 51485.904(20) cm−1.
TL;DR: In this paper, the influence of various scattering center distributions on the Landau level width and the cyclotron resonance linewidth is calculated for GaAs-AlGaAs heterostructures in high magnetic fields.
TL;DR: In this article, the effect of fast thermal fluctuations of electronic state occupancy on the field spectrum of semiconductor lasers is considered and an expression for the resulting power independent linewidth contribution is derived.
Abstract: In this letter we consider the effect of fast thermal fluctuations of electronic state occupancy on the field spectrum of semiconductor lasers and derive for the first time an expression for the resulting power independent linewidth contribution. The magnitude and temperature dependence of this linewidth component agree reasonably well with measurements of a power independent linewidth made by Welford and Mooradian.
TL;DR: In this article, the mean positions and root mean square (RMS) linewidths of the six-line Mossbauer Zeeman spectrum of 57 Fe in an amorphous environment have been set out and used to interpret the measured room temperature spectrum.
TL;DR: In this article, the static and dynamic properties of poly(γ-benzyl-L-glutamate) (PBLG) in dimethyl formamide at 25 °C using laser light scattering were reported.
Abstract: We report measurements of static and dynamic properties of poly(γ-benzyl-L-glutamate) (PBLG) in dimethyl formamide at 25 °C using laser light scattering. Correlation-function profile analyses were performed using the histogram method. The resultant average linewidth and dispersion were reconfirmed using the cumulants method. We were able to determine the molecular-weight distribution of PBLG using the histogram method and to confirm the polydispersity for rod polymers in solution to be roughly Mw/Mn ∼ 1 + μ2/Γ2. In our analysis of the Rayleigh linewidth, we used both the rigid-rod model and the Fujime approach involving rod flexibility. We obtained very reasonable agreement between the Fujime theory and our experiments and concluded that for most stiff polymers of interest, it would be more appropriate to use the Fujime approach, which could also yield a rod-flexibility parameter. In semidilute solutions, we observed two effects, namely, a maximum in the diffusion coefficient and a broadening of the linewidth distribution function at both low and high frequencies, which were not predicted by the Doi-Edwards theory.
15 Feb 1983
TL;DR: In this paper, a theory of the amplitude and phase modulation characteristic of a single mode semiconductor laser is presented, where the amplitude modulation couples through the complex susceptibility of the gain medium to the phase.
Abstract: A theory of the amplitude and phase modulation characteristic of a single mode semiconductor laser is presented. In this model the amplitude modulation couples through the complex susceptibility of the gain medium to the phase. We show that this coupling constant can be obtained by a high-frequency modulation experiment. This measured coupling constant is used to infer the linewidth enhancement factor as discussed by Henry, and Vahala and Yariv. Experiments confirmed the model and we measured a linewidth enhancement factor |alpha|=4.6±1.0 for a GaAlAs buried optical guide laser.
TL;DR: In this article, an easily tunable, single frequency source of UV radiation is described based on an intracavity second harmonic generation (SHG) using an angle tuned LiIO3 crystal in a ring dye laser.
TL;DR: In this paper, a theoretical description of planar channeling radiation is given, with special emphasis on the scattering processes contributing to the radiation linewidth, and a comparison between measured and calculated intensities serves as a further check on the theoretical treatment.
Abstract: A theoretical description of planar-channeling radiation is given, with special emphasis on the scattering processes contributing to the radiation linewidth. Owing to coherence between scattering in the initial and final states for the radiation process, the contribution to the linewidth from processes with small momentum transfer (e.g., plasmon excitation) is strongly suppressed, and the linewidth is dominated by thermal interband scattering. Also contributions from nonsystematic reflections and from finite crystal thickness are evaluated. Experimentally, planarchanneling radiation has been studied for 4 MeV electrons in nickel, at different target temperatures, and the radiation energies and linewidths confirm the predictions. The influence of correlation of vibrations is revealed by a variation of the linewidth with the angle to a major axis in the plane. The radiation intensity as a function of incidence angle to the plane is strongly modified by multiple interband scattering, and a comparison between measured and calculated intensities serves as a further check on the theoretical treatment.
TL;DR: In this paper, the effect of low frequency (1/f) carrier noise on the linewidth of a semiconductor laser was investigated and theoretical results suggest that broadening is strongly dependent on the 3 dB corner frequency of the 1/f noise.
Abstract: The effect of low frequency (1/f) carrier noise on the linewidth of a semiconductor laser is investigated. Theoretical results suggest that broadening is strongly dependent on the 3 dB corner frequency of the 1/f noise. As an example, a linewidth of 80 MHz broadens to 110 MHz with a 5 MHz corner frequency.
TL;DR: In this paper, the hyperfine and spin-rotation structure in the A 2 Σ 1/2 +, ν=0 state has been determined from linewidth measurements, a rotationally dependent predissociation is shown to be present.