Showing papers on "Laser linewidth published in 1975"
TL;DR: In this paper, a closed-form solution for the pulses of a homogeneously broadened laser mode locked by a saturable absorber of relaxation time much longer than the pulsewidth is presented.
Abstract: A closed-form solution is presented for the pulses of a homogeneously broadened laser mode locked by a saturable absorber of relaxation time much longer than the pulsewidth. With suitable approximations, the pulse shape is a secant hyperbolic. The system is described in terms of the linewidth omega C of the system, the saturation energies of the saturable absorber and the laser medium, the ratio of saturable-absorber loss to resonator loss, and the ratio of cavity round-trip time and laser-medium relaxation time. The energy and width of the pulse are obtained as functions of these parameters. Graphs are presented for the operating regimes as bounded by the choice of the preceding parameters. The theoretical predictions are compared with second-harmonic-generation (SHG) autocorrelation traces of mode-locked dye-laser pulses.
518 citations
TL;DR: In this article, the problem of absorption of microwaves by molecular oxygen in the atmosphere is treated by means of a first-order approximation to the impact theory of overlapping spectral lines.
Abstract: The problem of absorption of microwaves by molecular oxygen in the atmosphere is treated by means of a first-order approximation to the impact theory of overlapping spectral lines. By including only the coupling between adjacent rotational states in molecular collisions, we have devised a simple approximate method for computing the interference between lines from measurements on the resolved lines. The need for an empirically determined function describing the linewidth/ pressure ratio is eliminated. Comparisons with measurements at atmospheric pressures show that the first-order interference accounts for the low absorption at the band wings near 1 atm pressure. It also predicts the correct amount of asymmetry between high and low frequency wings. Improvement over previous models for the pressure broadening is obtained at frequencies \gsim 55 GHz. This approach is not specific to oxygen and could be adapted to other similar molecules.
469 citations
TL;DR: In this article, the design and performance of a prism beam expander and a holographic grating were discussed, and a dye laser pumped by a nitrogen laser was given 15 kW of diffraction limited power in 0.1-0.2 cm−1 linewidth.
Abstract: Design considerations and performance of a prism beam expander are presented. Using a prism beam expander and holographic grating, a dye laser pumped by a nitrogen laser has given 15 kW of diffraction limited power in 0.1–0.2 cm−1 linewidth. Addition of a single etalon gave a single frequency output of 10 kW in a linewidth of less than 0.01 cm−1.
162 citations
Patent•
13 Jan 1975
TL;DR: In this paper, an electrical signal is applied to the tuning crystal to establish an electrical tuning field within the crystal, and a desired laser tuning rate is established by rotating the optic axis of the crystal through a selected small acute angle from the direction of the laser light path through the crystal.
Abstract: A tunable laser includes a birefringent tuning crystal placed in the laser cavity. An electrical signal is applied to the tuning crystal to establish an electrical tuning field within the crystal, and a desired laser tuning rate as a function of the applied electrical signal is established by rotating the optic axis of the crystal through a selected small acute angle from the direction of the laser light path through the crystal. The tunable laser is included in tunable laser systems for derivative spectroscopy and transient spectroscopy.
104 citations
TL;DR: In this article, a new method is presented to measure the temperature of the optical cavity of a junction laser as a function of the average electrical power supplied to the device, based on a null measurement of the exact wavelength of a single Fabry-Perot mode and therefore does not require a preliminary calibration measurement.
Abstract: A new method is presented to measure the temperature of the optical cavity of a junction laser as a function of the average electrical power supplied to the device. The technique relies upon a null measurement of the exact wavelength of a single Fabry-Perot mode and therefore does not require a preliminary calibration measurement. Because of the small linewidth of the mode, very small ( C) temperature differences are easily measured. The method is utilized to obtain the thermal impedance for several different types of bonded stripe-geometry junction lasers.
90 citations
TL;DR: In this paper, it is argued that the increase of the paramagnetic resonance linewidth of CrBr3 with increasing temperatures above 100°K is primarily due to a spin-lattice relaxation mechanism.
75 citations
TL;DR: In this article, the authors report the fabrication, testing, and analysis of distributed feedback (DFB) single-heterostructure (SH) electrically pumped GaAs lasers.
Abstract: This paper reports the fabrication, testing, and analysis of distributed-feedback (DFB) single-heterostructure (SH) electrically pumped GaAs lasers. The techniques of fabricating the DFB grating and diode using interferometric exposure of photoresist, development, ion milling, liquid-phase-epitaxial growth, and diffusion are described in detail. Next, experimental results on a variety of diodes operating at 77 K are presented. It is shown that narrow laser linewidth (< 0.15 A) and low threshold operation (775 A/cm2) can be obtained. Also reported is output coupling from the grating which results in highly collimated laser beams with divergence of approximately 0.35°. Coupling coefficients, which determine laser threshold, are computed as a function of device parameters including physical dimensions, refractive indices, grating size and shape, and Bragg order for single-and double-heterostructure geometries. Calculated and measured thresholds are shown to be in good agreement.
60 citations
TL;DR: In this article, the authors measured the direct interaction between two-level systems in glasses at low temperatures and showed that this interaction results in a strong broadening of the excited state in addition to the natural linewidth.
58 citations
TL;DR: In this article, a continuous train of <500 ps (detector limited) pulses has been produced with a cw dye laser pumped by a mode-locked argon ion laser, and an intracavity acousto−optic modulator was used to dump dye laser pulses at rates as high as 10 MHz.
Abstract: A continuous train of <500 ps (detector limited) pulses has been produced with a cw dye laser pumped by a mode−locked argon ion laser. The cavity lengths of the dye laser and argon laser were made equal in order to synchronously amplify a single pulse oscillating in the dye laser. An intracavity acousto−optic modulator was used to dump dye laser pulses at rates as high as 10 MHz.
57 citations
TL;DR: In this article, a fully ion-implanted miniature 8192-bit random access memory chip was fabricated using electron-beam lithography with minimum linewidth between 1 and 1.5 μm and advanced Si FET technology.
Abstract: A fully‐ion‐implanted miniature 8192‐bit random‐access memory chip has been fabricated using electron‐beam lithography with minimum linewidth between 1 and 1.5 μm and advanced Si FET technology. Device structure, processing steps, mask transfer, and reactive ion etching processes capable of fabricating device structures in the micrometer and submicrometer dimensions are described. With a minimum linewidth of 1.25 μm, the memory chip occupies an area of 1.1×1.6 mm with an array density of 5 million bits/in.2 (0.8 million bits/cm2). A typical readout access time of 90 ns was measured on a functional chip.
53 citations
TL;DR: Ferromagnetic resonance linewidth data for 75% Ni−25% Fe evaporated thin films at 2-36 GHz for both parallel and perpendicular orientations have been obtained in this article.
Abstract: Ferromagnetic resonance linewidth data for 75% Ni‐25% Fe evaporated thin films at 2–36 GHz for both parallel and perpendicular orientations show that the two linewidths are the same and increase linearly with frequency above 10 GHz. At lower frequencies the parallel linewidth is in accord with the high‐frequency behavior, but the perpendicular linewidth levels off at 10–30 Oe. These data suggest that the high‐frequency relaxation is characteristic of a Landau‐Lifshitz λ‐type process but that the low‐frequency losses are characteristic of a process intermediate between λ‐type and 1/τ‐type relaxation.
IBM1
TL;DR: In this article, it was shown that the linewidth reduction provided by counter-propagating beams can be used to sweep a two-photon resonance through the sum frequency of the applied light while simultaneously satisfying the conditions required for optical adiabatic rapid passage.
Abstract: We show that, by virtue of the linewidth reduction provided by counter-propagating beams, it is possible to use the optical Stark shift to sweep a two-photon resonance through the sum frequency of the applied light while simultaneously satisfying the conditions required for optical adiabatic rapid passage. Consequently, the application of a near-resonant pulse of light can result in complete population inversion of a two-photon transition.
TL;DR: In this article, the photoresist linewidth is maximized when the resist thickness is a multiple of half the exposure wavelength in the resist, and the effect increases with increasing reflectivity of the substrate.
Abstract: Photoresist thickness nonuniformities in the vicinity of profile steps on substrate surfaces lead to linewidth variations of AZ 1350 photoresist geometries. The effect increases with increasing reflectivity of the substrate, decreasing photoresist layer thickness, and decreasing contrast transfer of the exposure system. It is shown that the photoresist linewidth is maximum when the resist thickness is a multiple of half the exposure wavelength in the resist.
TL;DR: In this paper, absorption resonances in the ν2 band of D2O in near coincidence with CO2 laser lines are reported and assigned, and the center frequency is 1079.8628 cm−1; the linewidth due to collisional broadening is 13 MHz/Torr.
Abstract: Absorption resonances in the ν2 band of D2O in near coincidence with CO2 laser lines are reported and assigned. Optical pumping induces strong laser emission at new submillimeter wavelengths, confirming the assignments. Acousto−optic modulation is used to tune the R (22) line of the CO2 laser into coincidence with the 000,533−010,422 D2O transition. Its center frequency is 1079.8628 cm−1; the linewidth (HWHM) due to collisional broadening is 13 MHz/Torr. D2S and HDS transitions in near coincidence with CO2 laser lines are also reported.
TL;DR: In this article, high-resolution measurements of SO2 absorption coefficients in the uv were presented in the wavelength interval between 2962 and 3011 A using a frequency-doubled dye laser as the radiation source.
Abstract: High‐resolution measurements of SO2 absorption coefficients in the uv are presented in the wavelength interval between 2962 and 3011 A using a frequency‐doubled dye laser as the radiation source. These measurements have application to pollution monitoring of SO2 using the differential absorption scattering (DAS) technique. The spectral resolution of the measurements was 0.2 A (determined by the linewidth of the dye laser) and the generated spectra exhibited considerable rotational structure on the (000) ″ to (060) ′, (070) ′, and (080) ′ electronic‐vibrational transitions. The latter transitions correspond to center wavelengths of 3001.8, 2981.0, and 2962 A, respectively. The laser measurements were obtained with a signal‐processing technique which eliminated calibration procedures associated with conventional optical‐absorption measurements. Using this technique, the statistical uncertainty associated with measured absorption coefficients has been reduced to less than ±2% with a wavelength uncertainty of...
TL;DR: In this article, narrow linewidth tunable lasers augur a new kind of laser Doppler velocimetry employing resonant absorption and fluorescence from trace atomic species rather than scattering from particles.
Abstract: Narrow linewidth tunable lasers augur a new kind of laser Doppler velocimetry employing resonant absorption and fluorescence from trace atomic species rather than scattering from particles. This technique may provide better turbulence and small volume information than present velocimetry.
TL;DR: In this article, the fluorescence line narrowing technique is used to study homogenous linewidths of several resonant transitions (1 D 2 ↔ 3 H 4 ) for the first time.
TL;DR: In this article, a single element electro-optical birefringent filter is used to tune the relatively high-gained flashlamp-pumped pulsed dye laser across the entire dye emission band, but the resulting laser line width is relatively wide as might be expected.
Abstract: It is shown that the single‐element electro‐optical birefringent filter can be used to tune the relatively high‐gained flashlamp‐pumped pulsed dye laser across the entire dye emission band, but the resulting laser line width is relatively wide as might be expected. However, this line width could be drastically reduced without losing the tunability by injection locking the pulsed laser to an electro‐optically tuned cw dye laser. The beam direction, collimation, spectral width, and stability of the pulsed laser can, therefore, all be precisely controlled through the cw laser beam.
TL;DR: In this article, a series of diagnostic experiments designed to measure the fundamental absorption parameters in CH3F for the P (20) CO2 laser line at 9.55 μm are presented.
Abstract: Results are presented from a series of diagnostic experiments designed to measure the fundamental absorption parameters in CH3F for the P (20) CO2 laser line at 9.55 μm. These parameters include the small‐signal absorption coefficient, the saturation intensity for the absorbing transition, and the homogeneous linewidth. These data provide a quantitative characterization of the pumping process for the cw CH3F laser operating at 496 μm.
TL;DR: In this paper, the temperature dependence of the FMR and EPR linewidth of bulk nickel single crystals was measured from 260 to 410°C at 9.85 GHz.
TL;DR: In this paper, an electrooptic birefringent Fabry-Perot etalon is described for a wavelength selector of dye lasers, which is tuned with a linewidth of several angstroms over 135 A. This was achieved by changing the applied voltages from -1.2 to + 1.2 kV to the etalon constructed from a 3.6 mm long, LiTaO 3 crystal.
TL;DR: In this paper, the motion of sodium ions in single crystals of beta-alumina has been studied via its effects on NMR linewidth and electric quadrupole interaction.
Abstract: The motion of sodium ions in single crystals of beta‐alumina has been studied via its effects on NMR linewidth and electric quadrupole interaction. A single line is seen between −160 and +220 °C at Larmor frequencies from 4 to 19 mHz, indicating rapid ionic motion. The average coupling constant remains almost constant over the temperaure range. The average asymmetry parameter is nonzero and decreases with temperature, reflecting the change in off‐axis site population. An activation energy of about 0.17 eV has been estimated from the linewidth changes in general agreement with that found from diffusion and conductivity measurements.
TL;DR: In this paper, the frequency calibration and linewidth measurements of the spin-flip Raman laser (s.w.r.l.) over the range 1905-1850 cm$^{-1}$ have been afforded by molecular spectroscopy of the gases carbonyl sulphide, nitric oxide, deuterium bromide and water vapour.
Abstract: Frequency calibration and linewidth measurements of the c.w. spin-flip Raman laser (s.f.R.l.) over the range 1905-1850 cm$^{-1}$ have been afforded by molecular spectroscopy of the gases carbonyl sulphide, nitric oxide, deuterium bromide and water vapour. Opto-acoustic detection, made possible by the large spectral brightness of the s.f.R.l. (some 10$^{10}$ times above that of a conventional black body source), was shown to be a particularly useful technique. Two regimes of operation of the c.w. s.f.R.l. were investigated. In the spin-saturated regime the output was continuously tunable to within 100 MHz, with a linewidth of ca. 300 MHz, whereas in the cavity mode limited regime the output exhibited discontinuous tuning characterized by mode pulling effects, but with a linewidth some two orders of magnitude lower. A complete band analysis of several vibration-rotation transitions in carbonyl sulphide was made the results agreeing well with previous data. This showed that even with its poorest resolution the c.w. s.f.R.l. is a powerful tool for spectroscopic applications.
TL;DR: In this paper, the electron spin resonance spectrum of single-crystal NiSnCl6-6H2O has been measured at X-band at temperatures between 4.2 and 370 K.
Abstract: : The electron spin resonance spectrum of single-crystal NiSnCl6-6H2O has been measured at X-band at temperatures between 4.2 and 370 K. The results are consistent with low-temperature magnetic and thermal measurements that indicate a singlet ground state for the Ni(H2O)6(2+) complex. Linewidth measurements below 300 K indicate contributions from spin-lattice relaxation and from both isotropic and anisotropic exchange. Linewidth measurements in the vicinity of D = 0 exhibit narrowing due to vanishing of the isotropic exchange contribution and broadening by cross-relaxation.
Patent•
10 Mar 1975
TL;DR: In this paper, a dual functioning cavity with a Ba 2 Na(NbO 3 ) 5 frequency doubling crystal provides two frequencies of laser radiation, one frequency double the other, to provide a laser beacon beam at a wavelength of approximately 1.06 micrometers and a high data rate beam at approximately 0.53 micrometer.
Abstract: A Nd:YAG laser operating in a dual functioning cavity with a Ba 2 Na(NbO 3 ) 5 frequency doubling crystal provides two frequencies of laser radiation, one frequency double the other, to provide a laser beacon beam at a wavelength of approximately 1.06 micrometers and a high data rate beam at a wavelength of approximately 0.53 micrometer.
TL;DR: Line shapes and intensities of several rotational lines have been measured as a function of pressure and temperature and initial measurements tend to confirm the theoretical predictions of Drayson as to relative line positions, but show linewidths higher than predicted by Yamamoto et al.
Abstract: A tunable diode laser spectrometer was used for high resolution measurements on the Q-branch of the ν2 vibration of carbon dioxide. The infrared source was a current tuned Pb0.936Sn0.064Se diode laser. A 1-m gas cell was designed to allow variation of temperature (200–300 K) at 1–50 torr of 320 ppm mixtures in nitrogen. Owing to the narrow linewidth of the diode laser, true line shapes may now be measured well into the Doppler region. Line shapes and intensities of several rotational lines (J ≤ 34) have been measured as a function of pressure and temperature. Initial measurements tend to confirm the theoretical predictions of Drayson as to relative line positions, but show linewidths higher than predicted by Yamamoto et al. The line strengths, at low temperatures, appear to be about 12% greater than those predicted by Drayson.
TL;DR: Results are significant for long path absorption monitoring of NH(3) with CO(2) lasers since the path length can be reduced by approximately 40% and for heterodyne mdetection of NH (3) since the relative position of the laser transition to the NH( 3) absorption line is well within the bandpass of Hg-Cd-Te photomixers (B >/= 1.5 GHz).
Abstract: Measurements of NH3 absorption coefficients are presented for several transitions of a C-13(O-16)2 laser for small concentrations of NH3(p less than 1 torr) for absorption lines broadened to 1 atm with N2. NH3 absorption coefficients were determined for laser transitions R(8)(920.2194 wavelengths/cm) to R(28)(933.8808 wavelengths/cm) of the 00 1 - (10 0,02 0)I band. The strongest absorption coefficient K = 36.09 + or - 1.43 per (atm-cm) was measured for the R(18) transition for the NH3 line, aQ(6,6), and is larger than has been found in any previous measurements with a CO2 laser. The dependence of K on total pressure was also obtained for select transitions, and the frequency separation between the R(18) laser transition and the neighboring NH3 line aQ(6,6) was determined to be 550 + or - 50 MHz. These results are significant for long path absorption monitoring of NH3 with CO2 lasers since the path length can be reduced by approximately 40% and for heterodyne detection of NH3 since the relative position of the laser transition to the NH3 absorption line is well within the bandpass of Hg-Cd-Te photomixers.
TL;DR: In this paper, a 496-μm CH3F cavity laser characterized by an average power of 9 kW and predominant single longitudinal mode operation with a linewidth of 28 MHz has been constructed.
Abstract: A 496‐μm CH3F cavity laser characterized by an average power of 9 kW and predominant single longitudinal mode operation with a linewidth of 28 MHz has been constructed. The power conversion efficiency of the laser (CH3F power out/CO2 pump power in) is on the order of 1.5×10−3. The CH3F gas is pumped in a zig‐zag fashion by the CO2 laser radiation.
TL;DR: In this paper, an efficient controlled frequency narrowing and tuning of a high-power 15−atm electron−beam−controlled CO2 laser has been achieved using a Fabry−Perot etalon as a dispersive element in the laser resonator.
Abstract: Efficient controlled frequency narrowing and tuning of a high−power 15−atm electron−beam−controlled CO2 laser has been achieved using a Fabry−Perot etalon as a dispersive element in the laser resonator. Tuning has been accomplished over the free spectral range of the etalon (∼2.3 cm−1) giving a laser linewidth of <0.2 cm−1 for an output pulse energy ∼100 mJ in a spot size ∼1 mm2. The laser pulse length is ∼40 nsec for a peak power ∼5 MW.